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PATTERNS OF OCCURRENCE OF CAMPYLOBACTER IN
DAIRY FARMS IN MIDWESTERN AND NORTHEASTERN
UNITED STATES

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AMY M. Campbell

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6/01 cz/CIRC/DateDuepGSp. 15

 

PATTERNS OF OCCURENCE OF CAMPYLOBAC T ER IN DAIRY FARMS IN
MIDWESTERN AND NORTHEASTERN UNITED STATES

By

Amy M. Campbell

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Large Animal Clinical Sciences
(Epidemiology)

2002

ABSTRACT

PATTERNS OF OCCURRENCE OF CAMPYLOBA C T ER ON DAIRY FARMS IN
MIDWESTERN AND NORTHEASTERN UNITED STATES

By

Amy M. Campbell

Campylobacter is the leading cause of bacterial gastroenteritis in the United
States. Because dairy cattle can be a source of Campylobacter in humans, more research
is needed to describe the epidemiology of Campylobacter in dairy cattle and to identify
the risk factors associated with the prevalence Campylobacter in dairy cattle.

In this work, three major objectives were addressed. First, the patterns of
occurrence of Campylobacter on dairy farms in Michigan, Minnesota, New York, and
Wisconsin were identified. Secondly, any differences in the prevalence of
Campylobacter by cattle age group, health status, and season were determined. Finally,
specific risk factors that contributed to the prevalence of Campylobacter on dairy farms
were identified.

The overall prevalence of Campylobacter of dairy farms in Michigan, Minnesota,
and Wisconsin was 12%. Calves had a higher prevalence of Campylobacter than adults,
sick adults had a higher prevalence than healthy adults, and Campylobacter prevalence
was the highest in winter and lowest in summer. Risk factors associated with an
increased prevalence of Campylobacter on dairy farms were those that increased risk of

fecal contamination and increased exposure to infected animals.

ACKNOWLEDGEMENTS

I would first like to thank USDA-NR1 and Population Medicine Center for their
support of this project.

I would also like to thank Doctors Bartlett, Corner and Mansfield for being a part
of my committee.

Thanks to all of the farms that participated in this study and to everyone that
worked long hours to collect and process over 25,000 samples and those that did the
tedious job of entering data. Without all of you, this project would not be possible.

Also, I would like to thank RoseAnn Miller for her continued enthusiasm
assisting me through the many stages of my thesis.

Special thanks to my major advisor, Dr. John Kaneene for all of his help. I am
still trying to figure out how he has managed to remain calm through all of the stressful
moments he has encountered during this project.

Finally, I would like to thank my family and my new husband for the endless

support they have given me through all of this.

iii

TABLE OF CONTENTS

LIST OF TABLES ............................................................................................. vi
LIST OF FIGURES .......................................................................................... viii
INTRODUCTION
Purpose ............................................................................................................ 1
Hypotheses Tested .......................................................................................... 1
Objectives ....................................................................................................... 2
Overview ......................................................................................................... 2
CHAPTER 1
A REVIEW OF CAMPYLOBA C T ER. SPP. IN CATTLE AND ITS IMPORTANCE IN
HUMAN INFECTION
Introduction ..................................................................................................... 3
Background of Campylobacter ....................................................................... 4
Pathology in Cattle .......................................................................................... 6
Frequency in Cattle ......................................................................................... 7
Significance of Cattle as sources of infection for humans .............................. 14
Preventive Measures ....................................................................................... 17
Discussion ....................................................................................................... 18
CHAPTER 2

PATTERNS OF OCCURENCE OF CAMPYLOBAC T ER IN ORGANIC AND
CONVENTIONAL DAIRY FARMS IN MIDWESTERN AND NORTHEASTERN
UNITED STATES: A HERD LEVEL ANALYSIS

Structured Abstract ...................................................................................... 20
Introduction ................................................................................................... 22
Materials and Methods .................................................................................. 25
Statistical Analysis ........................................................................................ 29
Results ........................................................................................................... 30
Discussion ..................................................................................................... 34
Conclusions ................................................................................................... 46
CHAPTER 3

PATTERNS OF OCCURENCE OF CAMPYLOBA C T ER IN ORGANIC AND
CONVENTIONAL DAIRY FARMS IN MIDWESTERN AND NORTHEASTERN
UNITED STATES: AN INDIVIDUAL LEVEL ANALYSIS

Structured Abstract ....................................................................................... 58
Introduction ................................................................................................... 60
Materials and Methods .................................................................................. 61
Statistical Analysis ........................................................................................ 65

iv

Results ........................................................................................................... 67

Discussion ..................................................................................................... 70

Conclusions ................................................................................................... 80
OVERALL CONCLUSIONS ............................................................................ 89
APPENDIX

Initial Questionnaire ...................................................................................... 93

Herd Visit Questionnaires ............................................................................. 116
REFERENCES .................................................................................................. 123

Table 2-1

Table 2-2

Table 2-3

Table 2-4

Table 2-5

Table 2-6

Table 2-7

Table 2-8

Table 3-1

Table 3-2

Table 3-3

Table 3-4

Table 3-5

LIST OF TABLES

Description of farms by herd size, and state
Apparent Period Prevalence of Campylobacter from Animals

Apparent Period Prevalence of C ampylobacter from Milk and
Environmental Samples

Risk Factors used in Herd, Cow, and Calf Population Multi-
variable Analyses

F inal multivariable Poisson regression model for prevalence of
Campylobacter, for herd (n=127), controlling for herd size,
state, and season

Final multivariable Poisson regression model for prevalence of
Campylobacter, for Cow Population (n=127), controlling for
herd size, state, and season

Final multivariable Poisson regression model for prevalence of
Campylobacter, for Calf Population (n=127), controlling for
herd size, state, and season

Comparison of risk factors between Cow Population and Calf
Population Poisson regression model for Campylobacter
Prevalence, controlling for herd size, state, and season
Description of farms by herd size, and state

Cattle population in the analysis

Risk Factors used in Cow and Calf Population Multivariable
Analyses

Final multivariable logistic regression model with random effects
for prevalence of Campylobacter, for cows (n=20,3 80), controlling
for herd size, state, and season

Final multivariable logistic regression model with random effects

for prevalence of Campylobacter, for calves (n=4,741), controlling
for herd size, state, and season

vi

48

49

50

51

53

54

55

56

82

83

84

86

87

Table 3-6

Comparison of risk factors between Cow and Calf Logistic
Regression models for Campylobacter status, controlling for
herd size, state, and season

vii

88

Figure 2-1

LIST OF FIGURES

Frequency of apparent prevalence in herds

viii

57

INTRODUCTION

Purpose

Campylobacter is the leading cause of bacterial gastroenteritis in the United States.
Foods of animal origin are considered to be the greatest sources of these pathogens to
humans. Since cattle are known to be intestinal carriers of C ampylobacter, consumption
of meat and milk from cattle has been identified as a major risk to humans. There have
been limited studies on the epidemiology of Campy/obacter in dairy cattle on the farm,
which have described the prevalence of C ampylobacter and identified some risk factors
that affect Campylobacter prevalence on the farm. More extensive research is needed to
describe the epidemiology of Campylobacter in cattle on the farm in greater detail, and to
confirm the effects of previously reported risk factors and identify new risk factors
associated with Campylobacter in cattle. This information will aid dairy producers in
reducing the potential for contamination of meat and milk used for human consumption.
Hypotheses Tested

1. C ampylobacter is prevalent in cattle on dairy famrs.

2. The prevalence of Campylobacter on dairy farms varies by cattle age groups
(calves and adult cows), and by season (hypothesis tested in Chapter 2 and 3).

3. Specific dairy herd management practices (including health management,
feeding and housing, biosecurity, and sanitation) affect Campylobacter

prevalence on dairy farms (hypothesis tested in Chapter 2 and 3).

Objectives

1. Identify patterns of occurrence of Canzpylobacter on dairy farms in Michigan,
Minnesota, New York, and Wisconsin.

2. Determine whether there are differences in the prevalence of Campylobacter
by cattle age group, location, and season. Identify specific risk factors that
contribute to the prevalence of Campylobacter on dairy farms.

Overview

Chapter 1 is a literature review of Campylobacter in cattle and the role cattle play in
human Campylobacter infection. Particular attention is paid to the risk factors that
contribute to Campylobacter prevalence in cattle. Chapter 2 is a herd level analysis of
risk factors for Campylobacter prevalence in cattle on Midwestern and Northeastern
dairy farms in the United States. Chapter 3 is an individual animal level analysis of risk
factors for the occurrence of Campylobacter in cattle on Midwestern and Northeastern
dairy farms in the United States. The importance of both analysis approaches is

discussed in the conclusion.

CHAPTER 1

A Review of Campylobacter spp. in Cattle and Its Importance in Human infection

1. Introduction

Campylobacter is considered the current leading cause of bacterial gastroenteritis in
the United States (Altekruse et al, 1999). The usual consequences of Campylobacter
infection are not serious and do not need medical intervention. It is only when
campylobacterosis causes severe illness, sequela such as Guillian-Barré Syndrome,
antimicrobial resistance, and in rare instances, death that this organism becomes an issue
for the human population both medically and economically (McDowell and McElvaine,
1997; Wegener, 1999).

The sources of human infection are linked mainly to food animals. Poultry, cattle,
pigs, and sheep are known to be reservoirs for Campylobacterjejzmi and Campylobacter
0011'. These organisms do not usually cause disease for these animals but function as
commensals (Blaser et al, 1983). Humans acquire Campylobacter infection from these
animals in an indirect way. Preparation of contaminated meat is primarily the cause for
humans to become infected. Either the contaminated meat is not fully cooked or cross-
contamination occurs in the kitchen while preparing the contaminated meat (Skirrow,
1982). Poultry is known to be the most important source of infection for humans and is
estimated to cause from 50 to 70% of all human infections (Allos, 2001). Whereas
poultry remains the most important source of human infection, the importance of cattle in

the transmission to humans should not be overlooked.

Campylobacter spp. have been reviewed in a number of papers. Altekruse et al (1998)
summarize the epidemiology of Campylobacterjejuni in relation to its many reservoirs
and its role in the human population. They reported that the greatest concern to humans
is the contamination of food, mainly meat, with Campylobacterjejuni. Griffiths and
Park (1990) describe Camylobacters and the association with human disease. They
summarize the epidemiology, pathogenicity, and microbiology of Campylobacters. The
main conclusion from this report is that human disease mainly occurs because of food
contaminated with Campylobacter. To date, no review has been written on the
Campylobacter in cattle and its importance in humans. None of these reviews or other
reviews emphasized the possible areas where the research could be improved; therefore,
the purpose of this paper is not only to give background information on Campylobacter,
describe Campylobacter in cattle, and underline the important role of cattle in human
campylobacteriosis, but also identify the gaps that exist in the previous literature in order

to better direct future research.

2. Background of Campylobacter

Campylobacter was originally known as Vibrio. in the early part of the 20th century.
It was first known to cause abortion in sheep. By the 19305, this Vibrio sp. was known as
the cause of jejunitis in cattle and then named V. jejum‘. It wasn’t until the 19605 that the
classification of this organism changed from Vibrio spp. to Campylobacter spp. (Sebald

and Véron, 1963). Even though the importance of this organism was described in many

animals previously, it was not until the 19705 that Campylobacter spp. was recognized as
a human pathogen associated with acute diarrhea in humans (Skirrow, 1982). Today, it is
known that C. jejuni is commonly isolated from cattle and most commonly the cause of
human gastroenteritis (Blaser et al, 1983 and Altekruse, 1999).

Campylobacter spp. are gram-negative, spiral shaped rods. This group of organisms
possess a single flagella or polar flagella that create a distinct cork screw movement
(Griffiths et al, 1990). The environment that is best suited for this organism is one that is
thermophilic and microaerophilic. The thermophilic and microaerophilic environment
that best supports the survival of C ampylobacter spp. is at 42°C and from 5-10% C02,
respectively. The combination of these two environments allows this organism to be
easily found in the gut of many mammals (Ketley, 1997). Another important
characteristic of Campylobacter spp. is that this organism can transform from a viable rod
to a non-culturable coccoid form when exposed to oxygen or temperatures higher than
42°C (Skirrow, 1994 and Hazeleger et al, 1998). Even though Campylobacter spp. can
undergo this transformation in unfavorable conditions, it has a difficult time surviving in
temperatures below 30°C and in dry or acidic environments (Altekruse et a1, 1998).
Finally, differentiation between C. jejum’ and other Campja'lobacter spp. can be achieved
by serotyping, resistance to cephalothin, pulse-field gel electrophoresis, randomly
amplified polymorphic DNA, and hippurate hydrolysis. (Griffiths et al, 1990; Altekruse

et al, 1999; Skirrow, 1994; Allos, 2001).

3. Pathology in Cattle

The pathogenesis of Campylobacter in cattle is not well understood (Luechtefeld and
Lou Lang, 1982). It has been reported to cause a multitude of disease; however,
Campylobacter organisms are frequently isolated from healthy cattle (Myers et a1, 1984;
Skirrow, 1994; Wesley et al, 2000). Cattle are known to be good reservoirs for
Campylobacter because of the ability of this organism to establish itself as a commensal
in the gastrointestinal tract without causing any apparent disease (Stanely et al, 1998;
Stern, 1992; Warner et al, 1986). Although cattle are carriers of Campylobacter, it
continues to be a potential causative agent of disease in cattle when conditions are
favorable (Skirrow, 1994).

Most of the diseases linked to Campylobacter carriage are associated with the
gastrointestinal tract. Experimental inoculations of cattle were shown to result in enteritis
with blood and mucus present in the feces (F irehammer and Myers, 1981). In another
study conducted by Al-Mashat and Taylor, Campylobacter was isolated from enteric
lesions of cattle and calves (1980). Bacteremia was another anomaly observed in
neonatal calves following infection with Campylobacter (Warner and Bryner, 1984).
Yet, another gastrointestinal illness linked to Campylobacter in calves was acute colitis
(Morgan et al, 1983; Terzolo et al, 1987).

Other diseases not associated with the gastrointestinal tract, but associated with
reproduction, can also be linked to Campylobacter infection. One such disease is bovine
abortion. Bovine abortion may occasionally be due to C. jejuni but is commonly due to

C. fetus (Berg et al, 1971; Welsh, 1984; Van Donkersgoed et al, 1990, Skirrow, 1994).

Infectious infertility was another disease caused by Campylobacter in cattle that was first
described by Plastridge et a1 (1947). Vibrz‘o fetus, now called C. fetus, was the causative
agent of this lowered conception rate in cows. This was evident from isolation of C. fetus
in cows with infertility along with the evidence of serologically positive bulls. Another
disease associated with Campylobacter is mastitis. Experimental studies have
demonstrated that Campylobacter can cause clinical mastitis (Lander and Gill, 1980;
Logan et al, 1982). According to Lander and Baskerville (1983), experimental infection
of cows’ udders with Campylobacter can produce a range of symptoms from no disease
to severe clinical mastitis. There is very little evidence that nonexperimental clinical
mastitis is caused by Campylobacter. In one report, (Logan et a1, 1982), Campylobacter
was isolated from the udder of an infected cow. In their report, Logan et al (1982) went
on to explain the difficulty of isolating this organism from clinical mastitis cases.

Even though these diseases do not always occur or are not routinely apparent in cattle
and calves that are colonized with Campylobacter, this organism is still considered an
important pathological possibility. These bovine diseases caused by Campylobacter need
to be further defined and understood, especially in regards to clinical mastitis. Many
times these diseases are benign and not highly infectious in a herd, but they still warrant

concern when the bovine population becomes a common carrier of Campylobacter.

4. Frequency in Cattle

Campylobacter is commonly isolated from the feces of cattle; therefore, cattle are

considered common intestinal carriers of this organism (Manser and Dalziel, 1985).
Previous studies that reported on the prevalence of Campylobacter in cattle usually
focused on C ampylobacter carriage rates from healthy and sick adult cattle and/or healthy
and sick calves. In addition to the health status and age of the cattle, many reports
provided information on the species of Campylobacter that were isolated. The majority
research found C. jejuni to be most prevalent in cattle. Other pertinent information
included in these studies were type of cattle, herd information, number of samples
collected, type of sample, and how the samples were processed. Even though this
detailed information was provided, great variation in the reported carriage rate of
Campylobacter in cattle exist.

The reported Campylobacter prevalence in healthy adult cattle, either beef or
dairy cattle, ranged from 2.5% to 60% (Wesley et al, 2000; Giacoboni et a1, 1993;
Meanger and Marshall, 1989; Atabay and Corry, 1998; Humphrey and Beckett, 1987;
Hoar et a1, 2001; Manser and Dalziel, 1985; Munroe et al, 1983; Prescott and Bruin-
Mosch, 1981; Waterman et a1, 1984; Doyle and Roman, 1982). Some studies only
reported the occurrence of C. jejuni (Doyle and Roman, 1982; Waterman et al, 1984;
Prescott and Bruin-Mosch, 1981; Humphrey and Beckett, 1987; Munroe et al, 1983)
whereas other studies reported the occurrence of all Campylobacter spp. (Wesley et al,
2000; Giacoboni et a1, 1993; Meanger and Marshall, 1989; Atabay and Corry, 1998; Hoar
et al, 2001; Manser and Dalziel, 1985). If the studies looked at all thermophilic
Campylobacter, the major isolate identified was C. jejuni. The number of fecal samples
and the number of herds in the study varied between studies and some studies were

unclear as to how many herds were included (Waterman et al, 1984; Prescott and Bruin-

Mosch, 1981; Manser and Dalziel, 1985; Munroe et al, 1983). The largest number of
herds enrolled in the 10 studies was 31 (Wesley et a1, 2000) and the smallest number was
only one herd (Doyle and Roman, 1982; Meanger and Marshall, 1989). All studies
reported the total number of samples that were collected. Although all samples were fecal
samples collected rectally, all studies had some variations in the Campylobacter isolation
techniques. This may partially explain the differences in the prevalences between
studies, along with the other apparent differences observed between studies.

Three of ten studies reported on the difference in Campylobacter prevalence
between healthy and sick adult cattle (Manser and Dalziel, 1985; Munroe, 1983; Prescott,
1981). The sick cattle were considered sick because of the presence of diarrhea. The
frequency of Campylobacter among these sick cattle in the three studies was from 1.5%
to 26%. The frequency of Campylobacter found in the diarrheic cattle did not
significantly differ from the frequency of Campylobacter found in the healthy animals.
Among these studies sample numbers from diarrheic animals ranged from 198 (Manser
and Dalziel, 1985) to 314 samples (Munroe, 1983). Sample numbers from healthy cattle
ranged from 107 samples (Munroe, 1983) to 202 samples (Prescott, 1981). Two of the
three studies only reported C. jejuni rates (Munroe, 1983; Prescott, 1981) and one study
reported on all thermophilic Campylobacter (Manser and Dalziel, 1985). A11 fecal
samples in these three studies were obtained from submissions to veterinary teaching
hospitals or from submissions to diagnostic centers. Again, variation in isolation
techniques occurred in the three studies.

Comparing seven studies that examined the prevalence in healthy calves, the

reported Campylobacter prevalence ranged from 19% to 100% (Snodgrass et al, 1986;

Giacoboni et a1, 1993; Busato et al, 1999; Atabay and Corry, 1998; Myers et al, 1984;
Firehammer and Myers, 1981; Rycke et a1, 1986). The number of rectal fecal samples in
these studies ranged from 3 to 1521. The study that only sampled from 3 healthy calves
found a prevalence of 100% (F irehammer and Myers, 1981) whereas the study that
sampled 395 calves reported a prevalence of 42.9% (Busato et al, 1999). The number of
samples may be another reason prevalence varies greatly. Two studies reported only C.
jejuni rates (Firehammer and Myers, 1981; Rycke et al, 1986) and the other studies
reported thermophilic Campylobacter rates but included the breakdown by
Campylobacter species.

Of the seven studies that reported prevalence in calves, three of those studies
(Rycke et a1, 1986; Snodgrass et al, 1986; F irehammer and Myers, 1981) compared the
prevalence of Campylobacter between healthy calves and sick calves. Sick calves were
defined as sick due to enteric disease resulting in diarrhea. The prevalences of
Campylobacter in those sick ranged from 19% to 50%. One study sampled for two years
and reported the prevalence of Campylobacter from those two years separately
(F irehammer and Myers, 1981). The least number of samples collected from sick calves
in these three studies was 32 (Rycke et al, 1986) and the greatest number of samples was
156 (Snodgrass et al, 1986). Two of the studies statistically compared the prevalence of
Campylobacter between healthy and sick calves and found no statistical difference
between the two groups (Rycke et a1, 1986; Snodgrass et al, 1986). One study did not
examine the significance between the healthy and sick calves (Firehammer and Myers,
1981), probably due to the low number of samples collected from the healthy calves. The

two groups were not comparable based on the sample size so no further conclusions

10

could be made in regards to differences between the groups. Also, two studies reported
only C. jejuni rates (Firehammer and Myers, 1981; Rycke et al, 1986) while the
remaining study reported the thermophilic Campylobacter prevalence along with giving
the C. jejuni rate (Snodgrass et a1, 1986).

In all the cited studies in cattle some Campylobacter was isolated from the feces
of these animals, regardless of age. There was variation among all studies due to at least
one of the following reasons: isolation technique, number of animals studied, the species
of Campylobacter isolated, the health status of the animal, or the age of the animal.
There were probably many other factors that could contribute to the variations including
transportation of the samples to the laboratory, climate where the samples were collected,
and size of the sample collected. Even though variation was observed between all
studies, the information on the prevalence of Campylobacter in cattle is still useful for
other researchers and for farmers.

A number of studies examined milk from cattle for the occurrence of
C ampylobacter (Waterman et al, 1984; Oosterom et a1, 1982; Desmasures et al, 1997;
Beumer et al, 1985; Beumer et a1, 1988; Orr et al, 1995; Davidson et al, 1989; Doyle and
Roman, 1982; Rohrbach et al, 1992). Milk was either collected from bulk tanks or
directly from the individual cows. The majority of the studies reported only C. jejuni
rates (Waterman et a1, 1984; Oosterom et al, 1982; Beumer et al, 1985; Beumer et al,
1988; Orr et al, 1995; Davidson et a1, 1989; Doyle and Roman, 1982; Rohrbach et a1,
1992) whereas only one study did not report on the species of Campylobacter isolated
(Desmasures et al, 1997). The prevalence of C ampylobacter ranged from 0% to 95%.

Most herds had a very low prevalence of Campylobacter between 0.9% and 3.2%. The

11

one study that found 95% prevalence was an investigational study that only looked at 19
raw milk samples (Orr et al, 1995). The number of total samples investigated ranged
from 19 (Orr et al, 1995) to 1,501 (Waterman et a1, 1984). It was very difficult to find
Campylobacter in milk according to these studies. Again, these studies had different
transport and culture techniques that could explain the variation in the prevalence. For
the most part, the reported prevalences in milk were low. One study (Beumer, 1988)
found that an enzyme found in milk, lactoperoxidase, was the reason for the low recovery
rates in the samples. They experimentally inactivated this enzyme and found that the rate
of recovery of Campylobacter was much greater. This may be the major reason for the
difficulty in isolated Campylobacter from milk.

Only seven looked at potential risk factors associated with the prevalence of
C ampylobacter (Wesley, 2000; Busato, 1999; Hoar, 2001; Rohrbach, 1992; Meanger and
Marshall 1989; Waterman et a1, 1984; Humphrey and Beckett, 1987). Four of the seven
studies examined many different risk factors that could contribute to the frequency of
C ampylobacter (Wesley, 2000; Busato, 1999; Hoar, 2001; Rohrbach, 1992).

Wesley and colleagues (2000) found broadcast Spreaders for manure disposal,
feed containing alfalfa, feed containing cottonseed or hulls, and nuisance birds to be
significantly associated with the prevalence of Campylobacter on the herd-level. On the
cow-level, they reported that large herds and cows fed brewer’s by-products were
significantly associated with the presence of Campylobacter in the feces of cows. They
also found that lactating cows had significantly higher prevalence rates of Campylobacter

than cull cows.

In a longitudinal study (Busato et al, 1999), age, open barns, feeding a dry matter
that consisted of more than 50% grass or corn silage were found to be significantly
associated with increased prevalence of Campylobacter spp. in beef cattle. On the other
hand, the number of cows, crossbreed animals, antiparasitics, and feeding 50% dry matter
other than silage was significantly associated with the decreased prevalence of
Campylobacter.

In a cross-sectional study, Hoar et al (2001) used a multivariable model and found
the number of female cattle present to be the only significant factor for the increased
prevalence on the beef farms. The authors explained, however, that the number of female
cattle on these farms was an indirect indicator of herd size.

In another cross-sectional study, Rohrbach and colleagues (1992) examined the
associations between risk factors and Campylobacter prevalence. This study was
different because it looked at risk factors associated with Campylobacter prevalence in
bulk tank milk. They found no significant difference between any of the risk factors they
examined and the prevalence of Campylobacter in milk despite the 12.3% prevalence
found in the 292 milk samples collected. Some of the risk factors included were milking
hygiene, grade classification of dairy, mean cow number, number of clinical mastitis
cases, facilities for milking, or the percent of replacement stock on the farm.

The remaining three studies that looked at risk factors and the occurrence of
Campylobacter did not include formal statistics to analyze the risk factors that were
included on those studies (Meanger and Marshall, 1989; Waterman, 1984; Humphrey and
Beckett, 1987). In one longitudinal study conducted by Meanger and Marshall (1989),

they found that the highest prevalence rate of Campylobacter was in the autumn months.

13

Another study examined the risk of season in the association of Campylobacter
occurrence in cattle and found that cattle excreted more Campylobacter in the winter than
in the summer (Waterman, 1984). A third study found that herds exposed to river water
were more likely to shed Campylobacter than herds that drank from mains water
(Humphrey and Beckett, 1987). Without true statistical analysis only speculations can be
made in regards to these potential risk factors and the prevalence of Campylobacter in
cattle.

More than half of the studies that reported on the prevalence of Campylobacter in
cattle or in milk did not report on the possible risk factors contributing to the prevalence
rate. Prevalence, alone, only gives a partial picture of the occurrence of Campylobacter
in cattle. More extensive research needs to be done to help answer the questions of
where these isolates are originating from, why these isolates are persisting, and how farm
management practices can contribute to the increased or decreased rates of

Campylobacter found in cattle.

V. Significance of Cattle as sources of infection for humans.

Currently, the most common cause of bacterial diarrhea in most industrialized
countries is Campylobacter (Tauxe, 1992; Skirrow, 1994). Campylobacterjejuni is the
major source of Campylobacter enteritis in humans but other Campylobacter species
such as C. hyointestinalis, C. coli, C. lardis, and C. pylori are known to be associated
with human infection (Skirrow, 1994; Penner, 1988). The incubation period of

Campylobacter enteritis is from one to seven days (Andrews, 1998). The majority of

14

those that experience this type of illness have symptoms such as diarrhea, fever, and
severe abdominal pain. Some cases may even experience bloody diarrhea (Morris,
1996). By 24 to 48 hours after symptoms develop, the illness usually peaks and
gradually resolves itself within one week (Blaser, 1997). Treatment is not usually
needed, but if signs and symptoms persist or worsen antimicrobials may be prescribed
(Altekruse, et a1. 1999).

After the initial infection with Campylobacter, complications are known to occur
but are infrequent. Reactive arthritis, Reiter’s syndrome, pancreatitis, or Guillain-Barré
Syndrome (GBS) are possible sequelae to the initial gastroenteritis. The most important
of these sequelae is GBS. GBS affects approximately 1 out of every 1000 people
infected with Campylobacter. The onset of GBS occurs from 10 days to 3 weeks after
onset of diarrhea (A1105, 1997). GBS can range from mild demyelinating neuropathy to
severe axonal neuropathy that leads to residual disability (Rees et al, 1995). The clinical
presentation associated with this syndrome includes paralysis, pain, and wasting muscles
(Ropper, 1992; Miller, 1985). Most patients recover from GBS, but approximately 20%
will be left with some form of disability. Another 5% of GBS patients will not survive
this disease (Altekruse, 1999). GBS and the other sequelae of Campylobacter infection
are rare, but can cause significant hardship for those patients that experience such
complications.

An additional concern associated with Campylobacter is antimicrobial resistance.
Campylobacter resistance is reported to be on the rise. A marked resistance to
fluoroquinolones along with a number of other antimicrobial agents has been reported

(Aarestrup, 1999; Sanchez et al, 1994; Velazquez, 1995). There has also been

15

speculation as to why there is resistance and where it may be coming from. One possible
answer is that the increased resistance is due to the use of antimicrobial agents in humans
and in animals (Acar, 2001), however the problem is being focused on the use of
antimicrobials in food animals (Nicholls, 2001). This issue remains undefined because of
the limited research conducted in this area.

The initial step in combating the problem of Campylobacter disease in humans along
with the problem of Campylobacter resistance is to identify the potential risk factors for
Campylobacter infection. There are four commonly reported risk factors associated with
human campylobacterosis. The greatest risk to humans is reported to be contact with
contaminated food (Skirrow, 1994). Included in this category, is the consumption of raw
or undercooked meat including poultry, the consumption of raw or inadequately
pasteurized milk, and the cross-contamination from food items infected with
Campylobacter (Adak, 1995; Hopkins, 1984; Peabody, 1997; Frost, 2001). Contact with
animals is another potential risk factor for human illness (Blaser, 1980). This not only
includes contact with pets but also contact with food animals. The risk of animal contact
greatly increases if the animals are experiencing diarrhea (Tenkate, 2001; Saeed, 1993).
A third risk factor is the consumption of untreated water (Vogt, 1982). A final major risk
factor includes travel abroad (Rodrigues, 2000). Defining these risk factors helps to

create guidelines to minimize potential problems for humans.

16

VI. Preventive Measures

Preventive measures need to be applied to eliminate or decrease the potential risks of
human Campylobacter illness. Prevention must be placed into practice not only on the
human level but also on the animal level (Altekruse, 1994). One place to begin
prevention is the farm. Good livestock management practices must be put into effect in
order to reduce or eliminate the spread of Campylobacter among farm animals
(Altekruse, 1998a). One possible way to do so is by chlorinating the water supply
provided for the food animals (Kapperud, 1993). Additional farm risk factors must first
be defined before other farm management practices are put into effect.

Human behavior is another area that can be altered in order to control
campylobacterosis. People must exercise good food safety technique. This includes
separately preparing raw meat in an area apart from other foods, properly sanitizing
hands and cookware before and after food preparation, and thoroughly cooking meat
(CDC, 1998). Next, people that come in contact with animals should properly wash
hands after contact especially when diarrheic animals are handled (Blaser, 1983).
Unpasteurized milk should also be avoided (Skirrow, 1994). Finally, establishment of
surveillance systems will also insure proper monitoring of the disease along with

providing risk analysis and education geared toward prevention practices (Altekruse,

1998b)

l7

VII. Discussion

Much of the literature and research has been focused on poultry and poultry meat as
the major source of Campylobacter in humans. These reports compare prevalence of
Campylobacter between poultry meat and beef and report that beef products are a minute
problem. Only briefly does this literature mention the occurrence in live food animals
(Harris et al, 1986, Kotloff, 1999; Peterson, 1994, Humphrey, 1995; Dawkins, 1984;
Skirrow and Blaser, 1992). According to the articles reviewed in this paper, live cattle
should be of concern to the human population because of the high prevalence rate in
cattle. The literature does not focus much on cattle and beef products. This may be due
to the limited number of studies conducted in this area. Much greater research has been
conducted on poultry and poultry meat, which would influence many authors to report on
such trends. Serotyping helps in finding the possible origin of human Campylobacter
isolates. In one study by Nielson and colleagues (1997), both poultry and cattle were
identified as major sources of human Campylobacter due to serotyping. Poultry are a
very important source of human illness, but cattle are likely an underestimated source of
human campylobacterosis. More research is needed to examine the role of cattle in
human Campylobacter infection.

Along with the need to conduct further research on the association cattle play in
human Campylobacter cases, better research is needed to more accurately identify the
prevalence rate on the farms and also to better identify risk factors that contribute to the
prevalence on the farm. In previously reviewed literature huge variations exist in the

prevalence rates and risks factors of Campylobacter in cattle between each study. This is

18

due mainly to the isolation techniques and the number of herds or animals involved in the
studies. Because Campylobacter is believed to be shed intermittently, larger and longer
prospective studies need to be conducted to find truer prevalence rates. This, in turn, will
help to find additional risk factors in cattle and on the farm. Better studies will provide a
better basis for the potential risks to humans along with finding preventive measures on
the farms. Only one study has really met these objectives. The prospective study by
Wesley and colleagues (2000) was a large study that examined numerous risk factors
associated with Campylobacter prevalence in cattle. This study found a herd prevalence
rate of 80.6% (n = 31 herds) and a cow prevalence rate of 37.7% (n=2,085 cows).

Wesley and colleagues also found that the use of broadcast feeders, feed, dietary
supplements, and accessibility of feed to birds to be potential risks for the increased
prevalence in dairy cattle. Other studies like this will help reinforce their findings and get

to the root of the problem.

19

Chapter 2

Patterns of Occurrence of Campylobacter on Dairy Farms in the Midwestern and
Northeastern United States: A Herd-Level Analysis

STRUCTURED ABSTRACT

OBJECTIVES: 1) Identify patterns of occurrence of Campylobacter spp. over time; 2)
Investigate risk factors that contribute to prevalence of Campylobacter spp. on dairy

farms.

DESIGN: Longitudinal

SAMPLE POPULATION: 25,155 cattle from 128 randomly selected dairy farms from
Michigan, Minnesota, New York and Wisconsin. Herds were stratified by state and herd

size. Cattle were sampled based on age and health/lactation status.

PROCEDURE: Management data and biological samples were collected from each herd
bimonthly for 10 months, and Campylobacter spp. were isolated from these samples.
Apparent period prevalences (APP) were computed, and multivariable Poisson regression

was used to assess associations between management factors and herd-level APPS.

RESULTS: The overall APP of Campylobacter spp. was 12%, and over 97% were C.

jejuni. Higher APPs were seen in calves versus adults. Sick adults had higher APPS than

20

healthy adults, while healthy calves had higher APPS than Sick calves. APPS were highest
in winter and lowest in summer. Factors associated with higher APPS included higher
levels of calf diarrhea, the use of inorganic cattle bedding, and poor feed storage. Factors
associated with lower APPS included housing lactating cows on dry lots, and washing

calf housing.

CONCLUSIONS AND CLINICAL RELEVANCE: Management factors which
increased risk of fecal contamination and exposure to infected animals were associated
with higher APPS. Factors associated with decreased APPS were those that reduced
animal stress, and reduced environmental survival of Campylobacter spp. Specific
factors identified in this study can be used to develop programs to reduce Campylobacter

spp. on farms.

21

INTRODUCTION

Campylobacter is the most frequently identified cause of foodbome bacterial
gastroenteritis in the United States (Allos, 2001; Altekruse et al., 1999). Most cases are
mild, self-limiting episodes of vomiting, cramping and diarrhea, but serious illness can
occur in immune suppressed individuals (Tauxe et al., 1992; Acheson, 2001 ).
Antimicrobial resistance has been recognized as an emerging global health issue (Neu,
1992; Moore et al., 2001), and drug resistance has been found in Campylobacter from
humans (Allos, 2001; Moore et al., 2001). Long-term sequelae of Campylobacter
infection, including arthritis and the neuropathic Guillian-Barré syndrome, have been
identified (Rees et al., 1995; Mead et al., 1999). Foods of animal origin, including
poultry (Smith et al., 1999; Harris et al., 1986) and raw milk (Lehner et al., 2000), have
been associated with Campylobacter gastroenteritis. Dairy cattle are sources of foods
(milk and meat) that have been recognized as sources of Campylobacter for consumers
(Evans et al., 1996; Dilworth et al., 1988). Human infection can also occur through
contact with contaminated farm environments, ground water, and other farm animals
(Piddock et al., 2000).

Since Campylobacter can colonize the gastrointestinal tracts of mammals and birds
without causing disease (Manser and Dalziel, 1985), these animals can serve as reservoirs
of Campylobacter (Wesley et al., 2000). Cattle, poultry, swine, and sheep are known to
be intestinal carriers of Campylobacter spp (Blaser et al., 1983; Harvey et al., 1989;
Engvall et al., 1986; Penner and Hennessy, 1980). To date, only a limited number of

studies have been reported on Campylobacter in cattle. From these studies, reported

22

Campylobacter prevalence rates in cattle ranged from 5% (Oosterom, 1982) to 65%
(Atabay and Corry, 1998; Giacoboni et al., 1993), with most prevalence rates around 20%
(Manser and Dalziel, 1985; Beumer et al., Humphrey and Beckett, 1987).

Several factors have been associated with increased Campylobacter prevalence in
food animals, including animal age, health status, season, and environmental
contamination. Unfortunately, there have been very few studies (Wesley et al., 2000)
looking at dairy cattle management practices and their associations with herd
Campylobacter levels.

The relationship between Campylobacter occurrence and host age is not clear.
Chickens younger than two weeks were not colonized with Campylobacter, but the rate
of infection increased as the age of the flock increased (J acobs-Reitsma et al., 1995).
However, the prevalence of C. jejuni was greater in calves than in adult cows (Giacoboni
et al., 1993), and the rate of Campylobacter prevalence decreased as pigs aged (Weijtens
et al., 1993). In mammals, it appears that the Campylobacter shedding decreases with
age, but further research is needed to confirm this.

It is possible that associations between animal health and increased isolation of
Campylobacter may be due to other conditions that result in reduced immune response in
an animal, which could lead to increased Campylobacter burdens and subsequent
shedding. One study found that pigs with diarrhea had a higher isolation rate of C. coli
than healthy pigs (Nielsen et al., 1997). However, other studies have found no
differences in the isolation rate between healthy and sick calves (Rycke et-al., 1986;

Snodgrass et al., 1986), and healthy and sick cattle (Manser and Dalziel, 1985).

23

 

Additional work is needed to determine the influence of animal health on the prevalence
of Campylobacter Shedding.

Seasonal patterns in Campylobacter prevalence have been observed. Higher rates of
Campylobacter in cattle have been reported for winter (Waterman et al., 1984), and
Spring and autumn (Stanley et al., 1998). Another study found that Campylobacter
prevalence was highest in autumn and lowest in winter (Meanger and Marshall, 1989). In
poultry, Campylobacter spp. were Shown to occur at higher rates in May and October
(Atanassova and Ring, 1999), and in autumn (Kapperud et al., 1993). However, no
seasonal trends were seen in the rate of colonization of Campylobacter spp. in broiler
chickens (Gregory et al., 1997), or recovery rates for C. jejuni from dairy cattle in the US
(Wesley et al., 2000).

Since human infection has been linked with contact with contaminated farm
environments, ground water, and infected animals (Piddock et al., 2000), these sources
could also be sources of Campylobacter for cattle. One study suggests that the high rates
of C. jejuni in cattle may be due to feed and water contamination, and found increasing
recovery of C. jejuni on farms that used broadcast Spreaders for manure disposal (Wesley
et al., 2000). Unfortunately, Campylobacter are difficult to detect in environmental
samples due to the effects of temperature and desiccation (Hoar et al., 1999; Wage et al.,
1999), and other competitive microflora on samples (Waage et al., 1999). Consequently,
the effects of environmental sources of Campylobacter on the prevalence in cattle remain
unclear.

The studies conducted on the prevalence of Campylobacter spp. in food animals

suggest that there are multiple factors that contribute to the frequency of isolation in these

24

animals. Differences seen in results from these studies may be due to low numbers of
herds or animals or both, and the cross-sectional nature of these studies. The purpose of
this study was to use a longitudinal study design to determine the prevalence of
Campylobacter on Midwestern and Northeastern dairy farms, and major risk factors
associated with prevalence. The specific objectives of this study were to: 1) identify
patterns of occurrence of Campylobacter spp. over time; and 2) investigate specific risk

factors that contribute to prevalence of Campylobacter spp. on dairy farms.

MATERIALS AND METHODS

Study design -This study is part of a larger study, with the long-term goals to
describe the ecology of Campylobacter on Midwestern and Northeastern dairy farms, and
to understand the dynamics of shedding of these bacteria.

A longitudinal approach was used to collect specimens and corresponding data
relating to potential risk factors. Data collection and sampling occurred bimonthly over a
lO-month period, resulting in 5 to 6 data collection points over one year.

Study population -Dairy herds from Michigan, Minnesota, New York, and
Wisconsin were recruited for the study. Each farm needed to have at least 30 milking
cows, provide good records, and allow samples to be collected randomly from the
animals on the farm and from specific areas of the farm. A pool of farms was identified
based on travel time and distance to research facilities within each state, stratified by herd
size (Table 1), and farms were then randomly selected and recruited for participation in

the study.

25

Animals in each herd were classified into different age/status classes, including pre-
weaned calves; healthy lactating cows; cull cows (identified by the producer as selected
to leave the herd within 7 days, regardless of reason); periparturient (within 14 days of
calving) cows; and sick cows (as reported by the producer). The number of animals to
sample within a herd differed in each animal class: up to 15 calves, up to 5 cull cows, up
to 10 periparturient cows, and up to 5 sick cows were sampled. The number of healthy
lactating cows to sample was dependent on herd size: 20 from herds with 30-49 cows, 25
from herds with 50-99 cows, and 30 from herds with 100 or more milking cows.

Sample size -A sample Size of 128 dairy herds was established for the study, based
on the ability to evaluate herd level prevalence rates of Campylobacter. Collection of 50
samples in large herds (200 cattle or more) would provide 95% confidence of detecting at
least one positive animal per visit if the within-herd prevalence is 2 5%, which Should
allow sensitivity of sampling given reported prevalence rates vary from 5% to 37% in
individual dairy cattle (Oosterom et al., 1982; Hoar et al., 2001).

Data collection -Data were collected using initial and bimonthly pre-tested
questionnaires administered in person. On the initial questionnaires, data collectors
asked detailed questions about herd management practices, herd inventory, animal
housing, feed, water systems, production, milk quality, cattle health, manure
management, and antimicrobial use on the farm being studied. On the bimonthly
questionnaire, data collectors asked questions about any changes in the herd management
practices, herd inventory, and antimicrobial use that may have occurred after the previous

sampling visit.

26

An ‘other animal’ index was developed as a measure of the presence of other

animals on the farm that can carry Campylobacter:

Index H = Z Swine H + Poultry H + Geese},

where:
Swine” = 1 if swine present on the farm, 0 if no swine present
PoultryH = 1 if chickens, ducks, turkeys or other poultry present on farm, 0 if not
present
Geese” = 1 if wild geese present on farm, 0 if not present

Values for the index ranged from 0 to 3.

Sample collection - All samples collected were identified by farm code, sample
date, sample container number and type of sample (animal identification or type of
environmental sample). Cattle were systematically selected for sample collection, and
approximately 5 grams of feces were collected per rectum and placed in sterile Whirl-
pak® containers. Approximately 30 ml of milk were collected from the bulk tank, and the
milk filter was collected after the morning milking on the sampling day and stored in a
plastic bag for Shipping. Sterile cotton swabs of each environmental sample were taken
from several locations: floors in the sick and/or calving pens; calf housing, hides of cull
cows, feed alley, lagoon sludge or manure pile, and any bird droppings in the areas where
cattle may have come into contact. Swabs were saturated with sterile Skim milk for
transport, and placed in a Whirl-pak® for shipment. A 100 ml sample of water from a
cattle watering tank was collected in a sterile specimen cup. All samples were Shipped in

a Styrofoam cooler, packed with ice, and sent to a central laboratory at Michigan State

27

University. The samples were shipped within 24 hours of collection and processed
immediately upon arrival at the laboratory.

Sample processing -Fecal and bulk tank milk samples were prepared by the addition
of approximately 30 ml of phosphate buffered saline solution. Milk filters and
environmental samples were prepared by enrichment with 30 ml of Bolton broth (Oxoid)
supplemented with 5% laked horse blood and antimicrobial agents (20 mg/l l
cefoperazone, 20 mg/l vancomycin, 20 mg/l trimethoprim, 50 mg/l cycloheximide), and
incubated at 42°C in 5-10% CO2 for 48 h. After preparation or enrichment, samples were
then directly plated onto selective Campylobacter Blaser agar with Supplement B (BD
Bioscience), streaked for isolation, and incubated at 42°C in 5-10% CO2 for 48 b. If
growth was observed after 2 days, the isolate was subcultured onto a sheep blood agar
(SBA) plate and incubated at 42°C in 5-10% CO2 for 48 h. Gram staining, oxidase
testing (BD Bioscience), and hippurate (Remel) testing were performed. Motility testing
was performed by inoculating Mueller Hinton Broth with a heavy inoculum of the
suspect Campylobacter, incubating for 48 h at 42°C in 5-10% CO2 , and examining the
suspension under bright field microscopy for characteristic darting motility. Isolates that
were gram negative rods with spiral shaped morphology, demonstrated darting motility,
and were oxidase positive were classified as Campylobacter spp. Hippurate testing was
performed to distinguish hippurase positive isolates as C. jejuni while hippurase negative
isolates were classified as non-jejuni Campylobacter spp. If the gram-stain, oxidase test,
or motility test were not indicative of Campylobacter, the sample was recorded as

negative.

28

STATISTICAL ANALYSIS

Calculation of apparent period prevalence -Because animals from each farm were
tested every other month for a period of ten months and results were from a sample of
cattle population in the four states, apparent period prevalence was computed. A positive
animal was defined as an animal from which Campylobacter was isolated from any
sample during the lO-month period. Because different numbers of animals were tested
from each herd within a herd size category, weighted prevalence was computed, using a
previously reported method (Kaneene and Hurd, 1990). In order to describe the patterns
of this infection on dairy farms, apparent period prevalence was calculated in three ways;
one for the whole herd (cows and calves), one for cows only, and one for calves only.
The general formula used to calculate the apparent period prevalence (APP) in each

animal category was:

Positive Animals GH

APP = x100.0

 

Number of cattle tested in study period GH

where Positive Animals 0 was the number of Campylobacter-positive animals in group G
(whole herd, cows, or calves) tested from herd H, and Number of cattle tested in study
period c was the total number of cattle in group G from herd H.

Analysis of risk factors -Associations between the prevalence of Campylobacter spp.
and herd size, animal health status and age, location, season, and other possible on-farm

risk factors were tested using the non-parametric Wilcoxon rank-sum test for association.

29

Risk factors which were associated with Campylobacter prevalence at p g 0.2 were
considered for further analysis.

Multivariable analysis of risk factors was then conducted. Three separate models
were developed; one for the cow population, one for calf population, and one for both
cows and calves (herd model), Since cows and calves are managed differently on dairy
farms, and the apparent period prevalence of Campylobacter was found to differ between
cows and calves during preliminary analysis of the data. It was hoped that this approach
would provide Specific information that could be used in reducing the risk of this
infection in each age group.

Since the APP followed a Poisson distribution, multivariable Poisson regression
modeling (SAS PROC LOGISTIC) was used to identify the major risk factors associated
with the APP for each animal age class category. Herd size and state were included in
the multivariable model to control for confounding, as both were confounders of several
of the risk factors in the analysis. A backward elimination procedure was used to find the
best fitting model in each case: if removal of a potential confounder resulted in a 10% or
more change in the odds ratios of the remaining risk factors of interest, the variable was

retained in the model to control for confounding.

RESULTS

Study population -A total of 128 dairy herds from Michigan, Minnesota, New York,

and Wisconsin were enrolled in the study (Table 1). The average number of milking

cows per herd in Michigan, Minnesota, New York, and Wisconsin were 217, 169, 198,

30

and 177, respectively. A total of 25,155 samples from dairy cattle were studied, of which
19,727 (80.3%) were healthy lactating cows.

Apparent period prevalence -The overall APP of C ampylobacter was 12% from all
animals sampled (Table 2). The majority of the herds had prevalence values ranging
from 5% to 15% (Figure 1). There were significant associations (p 5 .0001) between
season and Campylobacter APP: winter was found to have higher APP, while the
summer had lower Campylobacter APP (Table 2). Calves had greater Campylobacter
APPS than adult cows (p 5 .0001) (Table 2). Sick cows had significantly higher levels of
Campylobacter than healthy adult cows (p = .0021) (Table 2), but healthy calves had
greater APPS than sick calves (p5 .0001) (Table 2). The APP of Campylobacter from
milk samples was 2.0%, with higher levels of Campylobacter in milk filters compared to
bulk tank milk samples (Table 3).

The APP of Campylobacter from environmental samples was very low, with an
overall prevalence of 1.3% (Table 3). The highest rates of isolation were from cull cow
hide swabs (2.5%), while the lowest rates were from swabs of the feed alley (.5%) (Table
3). A Significant difference was observed between the APPS of C ampylobacter in animal
samples (12.0%) and environmental samples (1.3%) (p 5 0.0001 ).

Identification of C. jejuni — Based on hippurate testing, almost all Campylobacter
isolates identified in this study were C. jejuni: 97.8% from animal samples (2,950 of
3,016 isolates) and 97.1% of environmental samples (68 of 70 isolates) were identified as

C. jejuni.

31

Multivariable analysis of risk factors -From 55 risk factors available, a total of 28
risk factors met the criteria for inclusion in the multivariable analyses (Table 4). Data
from one herd was omitted from analysis due to missing data on herd milk production.

Herd animal model -For the herd model (including both cows and calves), risk
factors associated with increased Campylobacter APP included not protecting feed from
wild birds or rodents, increased levels of calf scours within 60 days prior to the beginning
of the study, group-housing calves, the use of inorganic bedding for lactating cows, using
a bucket loader for feed, availability of sick animal housing, and higher percentages of
the milking herd coming from off-farm sources (Table 5). Risk factors associated with
reduced levels of Campylobacter included the use of dry lot housing for lactating cows,
and washing calf housing.

Cow population model -For healthy lactating cows, risk factors associated with
increased odds for Campylobacter included not protecting feed from wild birds or
rodents, increased levels of calf scours, group-housing calves, the use of inorganic
bedding for lactating cows, using a bucket loader for feed, availability of sick animal
housing, higher percentages of the milking herd coming from off—farm sources, and if a
manure pack was used for manure disposal (Table 6). Risk factors associated with the
reduced odds for Campylobacter included the use of dry lot housing for lactating cows,
pasture access for cattle, washing calf housing, washing feed loader buckets between
uses, and the use of combined Sick/matemity cattle housing.

Calf population model -In the model for pre-weaned calves, factors associated with
increased Campylobacter prevalence included increasing adult herd APP, increased

levels of calf scours, group housing of lactating cows, pasture access, the use of inorganic

bedding for calves, and high bacterial counts in bulk tank milk (Table 7). Risk factors
associated with the reduced Campylobacter prevalence in calves included cleaning milk
buckets between feedings, lactating cow access to dry lots, use of manure packs, and
possible contact with other animals on the farm.

Comparison of cow and calf population models -Risk factors that were retained in
both the cow and calf population models were increased levels of calf scours within 6
months prior to beginning of the study, cattle access to pasture, lactating cow access to
dry lots, use of manure pack, and the use of inorganic bedding (Table 8). Several risk
factors had similar affects on the APPS in both the cow and calf models. The use of
inorganic bedding and increasing levels of calf scours were associated with increasing
odds in both models, while keeping lactating cows on a dry lot was associated with
reduced prevalence in both models. However, there were risk factors that showed
differing effects between the models. Herd pasture access decreased the odds of cow
prevalence, but was associated to increased risk for calves, while the use of manure packs

was associated with increased risk for cows, but decreasing risk for calves.

33

DISCUSSION

Study population -We were able to recruit 128 herds for the study, and were able to
collect over 25,000 samples for bacterial isolation. While the initial target for herd
enrollment was to enroll equal numbers of herds in each Size classification, there were
very few small herds available for enrollment in the study. Despite this limitation, the
number of herds that were enrolled and the number of samples collected were sufficient
for the purposes of this study.

Apparent Period Prevalence -The overall herd APP reported in this study was
12%, which was somewhat lower than the prevalence reported for other studies of
Campylobacter in cattle of 20% (Manser and Dalziel, 1985; Beumer et al, 1988;
Humphrey and Beckett, 1987). Factors that may account for differences between our
current work and previous authors include: study design (longitudinal in this study versus
cross-sectional in other studies), number of cattle sampled (25,155 cattle samples versus
94 (Giacoboni et al., 1993) and 904 (Beumer et al., 1988)), and measure of prevalence
(period prevalence versus point prevalence).

In this study, Campylobacter prevalence was Si gnificantly associated with season.
Winter had the highest Campylobacter prevalence (15.5%), which agrees with results
from other studies (Waterman et al., 1984). Other studies have reported peaks in
Campylobacter incidence in fall (Meanger and Marshall, 1989; Stanley et al., 1998) and
spring (Stanley et al., 1996). Samples collected in the summer had the lowest seasonal
prevalence in this study (6.7%), which was also observed by other investigators

(Waterman et al., 1984). These differences in the effect of season on Campylobacter

34

prevalence could be due to cattle densities being increased in the winter months when
cattle are often confined indoors during inclement weather in the upper Midwestern and
Northeastern United States. The other studies were conducted in New Zealand (Meanger
and Marshall, 1989) and the United Kingdom (Stanley et al., 1996), which have climates
that may not necessitate protecting cattle from harsh weather.

Calves in this study had a Significantly higher Campylobacter prevalence (14.4%)
than adult cows (11.4%), which has also been reported in the literature (Giacoboni et al.,
1993). This may be due to the naive immune systems to Campylobacter in calves. As
cattle age, they have more opportunities to become exposed to Campylobacter, develop
immunity from these exposures over time, and become less likely to Shed the organism.

When comparing Campylobacter APP by animal health status, differences were seen
between sick and healthy cattle according to age. Sick adult cows were found to have an
APP of 17.9%, while healthy adults were found to have an 11.3% APP (p < .0001).
Conversely, healthy calves had an APP of 14.6%, and Sick calves had APP of 12.0%,
which did not statistically differ. These findings differ from reports in the literature,
which found no differences in prevalence based on health status (Manser and Dalziel,
1985; Rycke et al., 1986; Snodgrass et al., 1986).

A fundamental reason for this difference in findings with prior research may be in
how ‘illness’ was defined in the study. In several studies, illness was limited to enteric
disease (Blaser et al., 1983; Rycke et al.). 1986In the current study, diarrhea was the most
commonly reported illness in calves, which would suggest that results of this study
should be similar to the other studies. One explanation for the differences in calf APPS

may be that the pathogens responsible for diarrhea in calves (e.g., E. coli, Salmonella,

35

Coccidia) out-compete Campylobacter in the intestines, making it much more difficult to
detect Campylobacter in fecal specimens from sick calves. In adult cattle, illness was
defined by diagnoses which could include diarrhea, metritis, respiratory illnesses, ketosis,
displaced abomasum, milk fever, and peritonitis. These illnesses may suppress the
animal’s immune system, which may allow Campylobacter to flourish, and when levels
in the gut become high enough, become detectable in fecal specimens.

Campylobacter from milk filters and bulk tank milk samples were isolated in this
study. There have been reports of Campylobacter isolated from milk filters, especially in
food-related disease outbreak situations (Robinson and Jones, 1981). Farms that had
Campylobacter isolated from milk filters had higher levels of Campylobacter, with a
mean APP of 17% on these farms. This may reflect less hygienic procedures during
milking, and levels fecal contamination in the milking parlor.

Although the APP of Campylobacter from environmental samples was low (1.3%)
compared to animal samples (12%), we were able to isolate the organism from a variety
of environmental sources. The highest APP from environmental samples was from cull
cow hide swabs: these swabs were taken from the flank and rump of culled animals,
which are areas on cattle where fecal contamination would be likely. This is a significant
finding since Campylobacter on cull cattle hides may contaminate beef during the
slaughtering process.

In contrast, Swabs from the manure lagoon or manure pile did not yield higher levels
of Campylobacter than other environmental samples. These swabs were taken at the

edge of the manure lagoon or the surface of the manure pile, and any Campylobacter in

36

these areas would have been exposed to sunlight and open air, which would decrease
their likelihood of survival.

Campylobacterjejuni was the most frequently isolated species in this study. In
cattle, C. jejuni has been reported as the most common Campylobacter isolated (Nielsen
et al., 1997), and the most common species of Campylobacter associated with human
enteric disease is C. jejuni (Smith et al., 1999).

Risk factors associated with the APP —When examining risk factors associated
with the prevalence of Campylobacter on dairy farms, it is helpful to view them in an
epidemiological context, as being measures of host (cattle), agent (Campylobacter spp.),
or environmental factors.

The Herd Model

Host-Related Risk Factors —In general, host-related factors are those that are
indicative of cattle health and susceptibility to colonization and Shedding of
Campylobacter due to illness or age. Factors associated with increasing risk of
C ampylobacter identified in the herd model included increased levels of calf scours
within 60 days prior to beginning of the study, the availability of sick animal housing on
the farm, group housing of calves, the percent of the herd not raised on the farm, and
housing of lactating cows in dry lots.

Reported high levels of scouring calves may be indicative of higher levels of
pathogens on the farm. Since the immune systems of calves are not as well developed as
those of adult cattle, calves are more likely to shed Campylobacter than adults. Farm
maintenance of separate Sick animal housing may be an indirect indicator of herd health

status. Maintenance of separate facilities for sick animals requires an investment on the

37

part of the dairy operation: space must be made available, pens maintained and cleaned,
etc. Consequently, farms that make the investment in Sick animal facilities may have a
relatively constant level of sick animals that require segregation from the healthy milking
herd.

Stress is a known cause of decreased immune function in cattle (Jones, et al., 1999),
and several risk factors identified in this study are associated with sources of stress in
cattle. Group housing can be a source of competitive stress for calves, which would
result in increasing Campylobacter shedding. The increasing percentage of the milking
herd coming from off-farm sources is another area in which stress can influence the APP.
The stresses associated with transporting cattle have been associated with increased
bacterial shedding (CEAH, 1995),which may increase the number of cows actively
shedding at the time of sampling, and provide more opportunities for spread of
Campylobacter through fecal contamination by increasing the quantities of the organism
in the fecal material.

Dry lot housing for cows, 3 form of group housing, was associated with decreased
levels of Campylobacter. Dry lot housing for adults allows animals a lower density of
housing and may be less stressful than confining cattle to indoor housing, which can
result in lower APP in cows on dry lots. Group housing adults would allow direct contact
between cows, which would provide exposure to the entire population to any bacteria
carried by a single animal. Over time, the entire group would develop herd-wide
immunity to these bacteria, resulting in overall resistance to infection, which would

decrease the likelihood for Campylobacter Shedding.

38

Agent-Related Risk Factors —Risk factors associated with the agent, specifically
Campylobacter, are those which influence the quality or quantity or both of the agent
present and available for exposure to hosts. In the herd level model, the increasing
percentage of the milking herd coming from off-farm sources was associated with
increased Campylobacter prevalence. Cattle coming from off-farm sources may be naive
to the flora endemic on a farm or these introduced animals may bring new bacteria,
including Campylobacter, which may Spread quickly within members of a herd.

Environment-Related Risk Factors —Epidemiological environment-related risk
factors are those associated with the conditions in which the hosts become exposed to the
agent, and factors that affect the agent’s ability to survive outside the host during
transmission. Host exposure can occur in one of two general ways: either direct exposure
of uninfected hosts to infected hosts, or through indirect exposure of uninfected hosts
through contaminated feed, water, or housing. One risk factor for direct exposure was
group housing calves (increasing risk). Animals that are housed together have direct
contact with each other, and are more likely to spread disease within the group, which
would explain why group housing calves increases the APP of Campylobacter.

Risk factors for indirect exposure which were associated with increased risk of
Campylobacter were feed storage which protects from moisture but not from pests, using
inorganic bedding for lactating cows, and using a bucket loader for feed. Risk factors for
indirect exposure of animals to Campylobacter which were associated with decreased
odds of prevalence were washing calf housing and lactating cow access to dry lots.

Potential exposure to Campylobacter through contamination of feed was found

in this study. Not protecting stored feed from rodents, wild birds, and other pests was

39

associated with increasing prevalence, which agrees with one study which found that pest
access to feed stores could be responsible for the persistence of Campylobacter (Wesley
et al., 2000). In another study, the presence of rats on the farm was an indicator of
increased Campylobacter in broiler flocks (Kapperud et al., 1993). In another study of
lambs and beef cattle, temporal trends in antimicrobial resistance patterns of C. jejuni
coincided with peaks in bird activity in farm outbuildings: high levels of metronidazole
resistance were seen in isolates from starlings and gulls, and peaks in metronidazole
resistance in beef calves occurred when these birds were present in large numbers on the
farm (Stanley and Jones, 1998), indicating that wild birds and other pests may be sources
of Campylobacter for livestock.

In addition to risks of feed contamination by pests, using a loader for handling feed
was associated with increase risks for Campylobacter. Farms that used a loader for
moving feed often used the loader for moving manure, which would provide opportunity
for the loader bucket to become a vehicle for contamination of Campylobacter.

Conditions that reduced the survivability of Campylobacter in the environment were
associated with reduced prevalences in this study. In a dry lot, any environmental
contamination by fecal material would be exposed to sunlight, wind, and other
environmental factors that would reduce the survival of Campylobacter outside the host,
and consequently reduce the risk of a cow being infected through fecal contamination of
the environment. Also, there may be other factors associated with dry lot housing that
more directly decrease Campylobacter prevalence, but which were outside the scope of

this study.

40

The hygiene of cattle housing was associated with the APP of Campylobacter in this
study. Herds that used inorganic bedding for lactating cows Showed an increased risk for
Campylobacter. In this study, inorganic bedding was defined as any inorganic material
used for bedding such as sand, rubber tires or mats, mattresses, crushed limestone, etc.
While not significant in the analysis, these materials were washed or changed much less
frequently than organic bedding, which would provide conditions in which fecal
contamination of cattle housing would pose a greater risk for exposure to Campylobacter.
Washing calf housing will remove manure and any contaminated material in the calf
environment, which will decrease the chance of exposure to Campylobacter and other
enteric bacteria. High levels of calf diarrhea may also be an indicator of poor farm
hygiene. Infectious scours is difficult to contain, but basic cleaning and sanitizing may
help control and possibly prevent such outbreaks (Etgen et al., 1987). High levels of
scours would provide opportunities for spread of fecal contamination and subsequent

increases in levels of Campylobacter on the farm.

The Cow Population Model —Since over 80% of the samples evaluated in the Herd
model were from the cow population, there is considerable overlap in the results of the
two models.

Host-related Risk Factors —The use of shared maternity and Sick cattle housing
facilities was associated with decreased APP of Campylobacter, which is in opposition to
the association between any Sick cattle housing and increasing Campylobacter risk. The

reasons for the differences between these associations are not clear. The use of combined

41

sick and maternity facilities may reflect overall lower level of disease of a farm if
separate sick animal facilities do not need to be maintained.

The use of pastures for cattle was also associated with decreased risk of
Campylobacter. AS described for the use of dry lot housing for milking cattle in the herd
model, pasture access reduces animal density and may decrease animal stress, while still
providing opportunity for improved herd immunity.

Environment-related Risk Factors —In the cow model, risk factors associated with
Campylobacter prevalence were the washing of loader buckets (decreasing risk), herd
pasture access (decreasing risk), and the use of manure packs for manure storage
(increasing risk). As described in the herd model, use of a loader for feed and manure
handling may increase the risk of fecal contamination of feed. In this scenario, the
washing of loader buckets would then remove fecal materials and any microorganisms
present, and therefore reduce the risk of feed contamination with Campylobacter or other
bacteria. When evaluating the decreased risk of Campylobacter associated with pasture
use, housing cattle outdoors would decrease the survival of Campylobacter outside the
host, due to the effects of sunlight and desiccation in this open environment. On the other
hand, storing manure in manure packs increased risk for Campylobacter in this study.
Manure packs were defined as piles of manure stored inside barns, which would be
protected from sunlight, desiccation, and severe temperature changes. These piles would
constitute a risk for exposure to any cattle coming in contact with the manure pile, and

result in increased Campylobacter prevalence.

42

The Calf Population Model —

Host-related Risk Factors — The animal index was developed to measure the
presence of other species known to be intestinal carriers of Campylobacter on the farm,
including swine, chickens, turkeys, and other poultry (Harvey et al., 1999; Engvall, et al.,
1986; Penner and Hennessey, 1980). Since these animals commonly harbor
Campylobacter, it was expected that Campylobacter prevalence would increase if these
animals were also kept on the farm premises, but this effect was not seen. It is difficult to
determine why the presence of these animals was associated with reduced Campylobacter
prevalence. It is possible that the index, generated from whether these Species were
present or absent on the farm, was not sufficiently sensitive to the risk that these other
species may have posed to the cattle herd. A more likely explanation of this finding is
that the presence of various other livestock Species on a dairy farm did not measure dairy
cattle exposure to these other potential reservoirs of Campylobacter. Raising other
species may also be associated with other styles of overall farm management that
function to reduce the prevalence Campylobacter.

Agent-related Risk Factors — The adult cow APP and high bacteria counts in bulk
tank milk were associated with increased APP of Campylobacter in calves. Increased
levels of Campylobacter in adult cattle, which make up the majority of animals on the
farm, will result in increasing levels of the bacteria available for exposure to calves. If
milk with high bacterial counts is fed to calves, this provides a direct source of infection
for calves through the consumption of Campylobacter and other organisms in milk.
Campylobacter was isolated from both milk filters and bulk tank milk in this study (Table

3), making this scenario highly likely. The association between feeding waste milk and

43

Campylobacter prevalence was assessed in this study, but was not found to be Si gnificant.
These high bacteria counts may be an indicator of the milking and general hygiene
practiced on a particular farm.

Environment-related Risk Factors -There were several environment-related risk
factors present in the Calf Population model that were not retained in the Herd or Cow
Population models. Risk factors associated with increased Campylobacter included herd
access to pasture, housing calves on inorganic bedding, and keeping lactating cows in
group housing. Risk factors associated with reduced Campylobacter prevalence were
washing calf milk buckets and use of a manure pack. Almost all farms that used manure
packs (95%) kept cattle in dry lots, a reduced density group housing situation. It iS likely
that the use of manure packs is another indicator of low density housing in the adult
cattle, and does not directly protect calves from exposure to Campylobacter.

Herd access to pasture was associated with increased APP of Campylobacter in
the Calf Population model, but was associated with reduced APP in the Cow Population
model. The rationale for the differences in the effect of this risk factor on the two
populations is not clear, but may be Similar to factors which contribute to the
development of herd immunity in adults may actually increase expression of disease in
calves.

There were several risk factors present in the Calf Population model, which captured
information on calf exposure to Campylobacter through fecal contamination. As
described in the Cow Population model, the effect of using inorganic bedding for calves
probably increases risks for Campylobacter exposure due to increased fecal

contamination Since the bedding is changed or washed less frequently than organic

44

bedding. Group housing of lactating cows was associated with increase prevalence in
calves, presumably by increasing the adult herd reservoir of the organism. Conversely, a
group housing Situation with decreased density of adult cattle and lowered stress, such as
in dry lots, was associated with reduced prevalence in calves. Finally, washing calf milk
buckets between feedings would reduce the chance of Spreading infection through milk
that may become contaminated from environmental sources while in the bucket.

Comparison of Cow and Calf Population Models - Risk factors present and
consistent in effect both models were the levels of scouring calves in the 60 days prior to
the beginning of the study, the use of inorganic bedding, and keeping lactating cows in
dry lot housing. While the strength of association for the level of scouring calves was not
large (odds ratios ranging from 1.02 to 1.04), the consistency of the strength of the
association indicates that this is an important component of Campylobacter prevalence on
the farm. Levels of calf diarrhea are probably not specifically a cause of increased
Campylobacter prevalence, but can be used by farm managers as an indicator of
increased herd risk for Campylobacter due to poor hygiene practices.

Two risk factors were present in the Cow Population and Calf Population models,
but had differing effects on the Campylobacter APP. Herd access to pasture increased
the odds of Campylobacter prevalence in the Calf Population model, but decreased the
odds of Campylobacter prevalence in the Cow Population model, while the use of
manure packs on the farm was associated with decreased prevalence in the Calf
Population model and increased prevalence in the Cow Population model. As described
above, the differences seen in the effects in the two models may be a reflection of the

difference in the immune status of calves and cows. Calves and cows are managed very

45

differently on the farm, so the effects of risk factors may function differently in the two
age groups. Additional research is needed in this area to determine whether the effects of
these and other potential risk factors for Campylobacter shedding are influenced by

population immune status.

CONCLUSIONS

As previously mentioned, this study is one part of a larger study looking at the
ecology and dynamics of shedding of Campylobacter on dairy farms. We were able to
collect over 25,000 fecal samples for bacterial isolation from 128 dairy farms in 4 states
over a 10 month period, which provided the opportunity examine patterns in the APP of
Campylobacter in dairy calves and milking cows. Although there may have been areas in
the collection of data on risk factors that may have been more extensive, this study
provided information that can be used to direct future research on specific herd
management factors that can reduce the prevalence of Campylobacter on the farm.

In summary, Campylobacter was commonly found on dairy farms, particularly in
healthy calves and sick adult cattle. There were seasonal patterns seen in prevalence of
Campylobacter, with the highest rates seen in the winter and the lowest rates seen in the
summer. Results of multivariable analyses in this study found that factors associated
with reduced health of the herd were associated with increasing prevalence of
Campylobacter. Herd management risk factors associated with increased Campylobacter
prevalence were those which increased risk of fecal contamination and exposure for

cattle, and increased calf exposure to infected animals. Management risk factors

46

associated with decreased Campylobacter were those which reduced fecal contamination
risks, and increased the opportunities for adult animals to develop natural immunity to
Campylobacter through exposure to infected animals. The findings of this study are by
no means exhaustive, but the specific risk factors identified in this study can be used to
develop programs aimed at reducing the risk of infection on farms. Additional targeted
research on management strategies to reduce Campylobacter shedding on dairy farms
will provide the industry with the tools necessary to provide a safer milk supply to the

food chain.

47

Table 1. Description of farms by herd size, state, and farm management style

Herd Size‘I Michigan Minnesota New York Wisconsin

 

 

3O — 49 0 6 4 6
50 — 99 10 9 9 9
100 - 199 11 8 9 8
200 + 11 9 10 9
Total 32 32 32 32

a — Number of cows in milking herd

48

Table 2. Apparent Period Prevalence of Campylobacter from Animals

 

Category Number of animals tested Percent positive
Overall 25,155 12.0
State

Michigan 6,887 11.9

Minnesota 5,624 15 .2

New York 6,678 11.0

Wisconsin 5 ,933 10.2
Age Group

Adult cows 20,377 1 1.4
Calves 4,745 14.4

Health Status
Cows only — Healthy 19,303 11.3
. Cows only — Sick 606 17.0
Calves only — Healthy 4,380 14.6
Calves only — Sick 357 12.0

Season

Fall 4,701 14.1
Winter 5,906 15.5
Spring 6,480 13.8
Summer 8,036 6.7

 

49

Table 3. Apparent Period Prevalence of Campylobacter from Milk and

Environmental Samples

 

Category Number of samples tested Percent positive
Overall 5,127 1.3
Milk Samples
Bulk tank milk 562 1.1
Milk filters 560 2.9
Environmental Samples
Feed Alley 614 .49
Calf housing 606 .99
Sick pens 182 1.6
Maternity pens 451 1.6
Water tank 616 1.1
Manure Lagoon 614 1.3
Bird droppings 596 .84
Cull cow hide swabs 326 2.45

 

50

Table 4. Risk Factors used in Herd, Cow, and Calf Population Multivariable

Analyses

Risk Factor

Coding Used in Analysis

 

General Herd Management
% milking herd imported
General Cattle Housing
Lactating cows in dry lot housing
Any cattle kept in dry lot housing
Calves group housed
Calves housed on organic bedding
Calves housed on inorganic bedding
Lactating cows on organic bedding
Lactating cows on inorganic bedding
Frequency of calf organic bedding changes
Frequency of cow organic bedding changes
Herd has pasture access
Herd has access to surface water
Special Cattle Housing
Sick animal housing available
Maternity pens available

Shared matemity/ sick pens

51

Continuous (0 - 100%)

1 = yes; 0 = no

1 = yes; 0 = no

1 = yes; 0 = no

1 = yes; 0 = no

1 = yes; 0 = no

1 = yes; 0 = no

1 = yes; 0 = no
1) daily; 2) weekly; 3) monthly
1) daily; 2) weekly; 3) monthly

1 = yes; 0 = no

l=yes;0=no

l=yes;0=no
l=yes;0=no

l=yes;0=no

Table 4. Risk Factors used in Herd, Cow, and Calf Population

Multivariable Analyses (cont.)

Risk Factor

Coding Used in Analysis

 

Biosecurity and Sanitation
Feed protected from moisture

Feed protected from animal pests

Calf housing washed with water
Calf milk buckets washed

Loader used for feed
Wash feed loader buckets
Contact with other animals
Manure pack used
Slurry spread on fields
High somatic cell count (> 30,000)
High bacteria counts in milk (> 300,000)
Percent of herd calves scouring

APP for adult cows (calf model only)

1 = yes; 0 = no
1 == yes; 0 = no
1 = yes; 0 = no
1 = yes; 0 = no
1 = yes; 0 = no
1 = yes; 0 = no
Categorical index (0 - 4)
l = yes; 0 = no
1 = yes; 0 = no
I = yes; 0 = no
1 = yes; 0 = no
Continuous (0 - 100%)
Continuous (0 — 100)

Table 5. Final multivariable Poisson regression model for prevalence of

Campylobacter, for herd (n = 127), controlling for herd size, state, and

 

season
Risk Factor Odds Ratio * 95% CJ.
Feed protected from moisture 1.20 1.04 - 1.39
Percent of herd calves scouring 1.03 1.01 - 1.04
Lactating cows in dry lot housing .81 .73 - .90
Calves group housed 1.10 1.01 - 1.20
Lactating cows on inorganic bedding 1.36 1.24 - 1.50
Calf housing washed/w water .74 .66 - .83
Loader used for feed 1.20 1.05 - 1.36
Sick animal housing available 1.48 1.34 - 1.63
% Milking herd imported 1.06 1.04 - 1.07

 

Model -2 log L = 17,644.7
Likelihood ratio = 708.6, 19 d.f., p < .0001

Estimated R2 = 2.81 %

 

* - all odds ratios significant at p 5 0.05

53

Table 6. Final multivariable Poisson regression model for prevalence of

Campylobacter, for Cow Population (n=127), controlling for herd size, state,

 

and season
Risk Factor Odds Ratio * 95% CI.
Protecting feed from moisture only 1.36 1.15 — 1.61
Percent of herd calves scouring 1.02 1.00 - 1.03
Calves in group housing 1.13 1.03 — 1.25
Lactating cows in dry lot housing .87 .77 - .97
Herd has pasture access .80 .71 - .90
Inorganic bedding for lactating 1.44 1.28 _ 1.62
cows
Calf housing washed .76 .67 - .87
Manure pack used 1.17 1.01 — 1.35
Bucket loader used for handling 1.17 1.01 _ 1.3 6
feed
Loader bucket washed .79 .70 - .90
Sick animal housing available 1.78 1.51 — 2.09
Combined sick/maternity facility .83 .72 - .96
% Milking herd imported 1.06 1.04 — 1.08

 

-2 log L = 13,756.74

Likelihood ratio = 648.38 d.f., p < .0001

est. R2=3.16%

 

* - all odds ratios significant at p 5 0.05

54

Table 7. Final multivariable Poisson regression model for prevalence of

Campylobacter, for Calf Population (n=127), controlling for herd Size, state,

 

and season
Risk Factor Odds Ratio * 95% CI.
Adult Cow APP (5% change) 1.12 1.09 — 1.17
Percent of herd calves scouring (10%) 1.05 1.03 — 1.08
Lactating cows in group housing 1.49 1.01 — 2.19
Lactating cows in dry lots .75 .60 — .94
Herd has pasture access 2.17 1.67 — 2.80
Inorganic bedding for calves 2.54 1.69 — 3.82
Calf milk buckets washed .68 .56 — .83
Manure pack used .65 .49 — .86
High bacteria counts in milk 1.89 1.45 — 2.47
Other Animal Index .61 .49 - .75

 

-2 log L = 3,490.49

Likelihood ratio = 353.49, 18 d.f., p < .

est. R2 = 7.29 %

 

* - all odds ratios Significant at p _<_ 0.05

55

Table 8. Comparison of risk factors between Cow Population and Calf Population

Poisson regression model for Campylobacter prevalence, controlling for

herd size, state, and season

 

Calves Cows
Risk Factor O.R. * 95% CI. O.R. * 95% CJ.
Percent of herd calves scouring 1.05 1.03 — 1.08 1.02 1.00 — 1.03
Lactating cows on dry lots .75 .60 — .94 .87 .77 - .97
Herd has pasture access 2.17 1.67 — 2.80 .80 .71 — .90
Inorganic bedding used 2.54 1.69 — 3.82 1.44 1.28 — 1.62
Manure pack used .65 .49 — .86 1.17 1.01 — 1.35

 

* - all odds ratios significant at p 5 0.05

56

Figure Legend:

Figure 1. Frequency of Apparent Period Prevalence in Herds

 

H
N

 

 

I—i
O

 

 

 

 

  

 

Number of Herds
as

 

 
 

 

OllllT-i 25II—IlllTllIl‘l-I—i
5 10 15 20 30 35 40

Apparent Period Prevalence (%)

 

57

CHAPTER 3

Patterns of occurrence of Campylobacter on dairy farms in Midwestern and
Northeastern United States: An Individual Animal Analysis

STRUCTURED ABSTRACT

OBJECTIVE: Investigate specific risk factors that are associated with an animal’s

Campylobacter status on dairy farms

DESIGN: Prospective

SAMPLE POPULATION: 25,121cattle from 128 randomly selected conventionally
managed dairy farms and organic dairy farms from Michigan, Minnesota, New York and
Wisconsin. Herds were stratified by state, farm management and size. Cattle sampled

were divided into six classes based on age and health/lactation status.

PROCEDURE: Herd management data and fecal samples were collected from each herd
every other month over a 10-month period, and Campylobacter were isolated from fecal
samples. Multivariable logistic regression with random effects was used to assess the
associations between management risk factors and an individual animal’s Campylobacter
status.

RESULTS: The overall apparent period prevalence (APP) of Campylobacter was 12%.

58

Calves had higher APP than adult cattle, sick adults had higher APP than healthy adults.
Factors associated with a greater risk of Campylobacter included poor or stressed health
status, decreasing age, inorganic cattle bedding, pasture availability, level of milking herd
from off-farm sources , feed protected only from moisture, and the presence of sick
animal housing. Factors associated with lower risk of Campylobacter included washing
calf housing, washing calf milk buckets, housing lactating cows on dry lots, and

spreading manure slurry on fields rather than on-farm storage.

CONCLUSIONS AND CLINICAL RELEVANCE: Herd management risk factors
associated with higher risk of Campylobacter were those which increased risk of fecal
contamination and exposure for cattle, and increased calf exposure to infected animals.
Management risk factors associated with decreased risk of Campylobacter were those
which reduced fecal contamination and increased the opportunities for adult animals to
develop natural immunity to Campylobacter through exposure to infected animals.
Specific risk factors identified in this study can be used to develop programs aimed at

reducing the risk of this infection on farms.

59

INTRODUCTION

Campylobacter is identified as the leading cause of foodbome bacterial
gastroenteritis in the United States (Allos 2001; Altekruse et al., 1999). Most
Campylobacter enteritis cases are mild and self-limiting, but more serious consequences
like arthritis and the neuropathy Guillian-Barré syndrome can occur (Tauxe et al., 1992;
Rees et al., 1995; Mead et al., 1999). Antimicrobial resistance is another serious
consequence of Campylobacter infection and is considered an emerging global health
issue (Neu 1992; Moore et al., 2001). These issues pose a major medical and economic
concern for the human population (McDowell and McElvaine, 1997; Rees et al., 1995;
Wegener, 1999).

The greatest risk of Campylobacter infection in humans is fi'om foods of animal
origin. (Smith et al., 1999; Harris et al., 1986). Milk and meat from dairy cattle are one
of the sources of Campylobacter for consumers (Evans et al., 1996: Dilworth et al., 1988;
Lehner et al., 2000). Cattle are known to be intestinal carriers of Campylobacter spp.
(Blaser et al., 1983) Since Campylobacter can colonize their gastrointestinal tract without
causing disease (Manser and Dalziel, 1985). The reported Campylobacter prevalence
rate in dairy cattle is around 20% (Manser and Dalziel, 1985; Beumer et al., 1988;
Humphrey and Beckett, 1987).

Several factors have been associated with the risk of Campylobacter in dairy cattle,
including animal age, health status, and environment. Calves were reported to have
higher prevalence rates of C. jejuni than adult cows (Giancoboni et al., 1993). Several

studies have seen no increased risk for Campylobacter in sick cattle compared to healthy

60

animals (Rycke et al., 1986; Snodgrass et al., 1986; Manser and Dalziel, 1985). Grazing
on pasture was found to be associated with increased rates of C ampylobacter shedding in
contrast to animals fed hay and silage diets (Jones et al., 1999). Also, parturition
appeared to increase shedding in animals compared to other periods of gestation (Jones et
aL,1999)

From studies conducted on cattle, most have looked at herd-level risk factors that
influence Campylobacter prevalence (Beumer et al, 1988; Giacoboni et al, 1993;
Humphrey and Beckett, 1987; Stanley et al, 1998; Wesley et a1, 2000) (Chapter 2).

While these types of analyses offer tremendous insight, more information about the
dynamics of Campylobacter infection on the farm can be gained by evaluating risk
factors on the individual animal level. Therefore, the specific objective of this study was
to investigate specific animal-level risk factors associated with the shedding of

Campylobacter spp. in cattle on dairy farms in four Midwestern and Northeastern states.

MATERIALS AND METHODS

Study design

This study is part of a larger study, with the long-term goals to determine the ecology
of Campylobacter on conventional and organic Midwestern and Northeastern dairy
farms, and understand the dynamics of Shedding of this bacteria.

A prospective approach was used to collect specimens and corresponding data
relating to potential risk factors. Data collection and sampling occurred bimonthly over a

10-month period, resulting in 5-6 data collection points over one year.

61

Study population

Dairy herds from Michigan, Minnesota, New York, and Wisconsin were recruited
for the study. For a farm to be included in the study, it had to meet the following criteria:
a farm had to have at least 30 milking cows, provide good records, and allow samples to
be collected randomly from the animals on the farm and from specific areas of the farm
for a year. A pool of farms was identified based on travel time and distance to research
facilities within each state, and farms were then randomly selected and recruited for
participation in the study.

The study utilized conventionally-managed dairy farms and organic dairy farms
(certified to ship to local organic dairy processors and did not use any antimicrobial
therapy for cattle greater than one year old within the previous three years). The herds
were stratified into four herd size categories, 30 to 49, 50 to 99, 100 to 199, and more
than 200 milking cows. When possible, equal numbers of organic and conventional
dairies were enrolled within each Size class within each state.

Animals in each herd were classified into different age/status classes, including
calves less than 2 months of age (pre-weaning); healthy lactating cows; cull cows
(identified by the producer as leaving the herd within 7 days, regardless of reason);
periparturient (within 14 days of calving) cows; and sick cows (as reported by the
producer). Up to 15 calves, 5 cull cows, 10 periparturient cows, and 5 sick cows were
sampled from each herd. The number of healthy lactating cows to sample was dependent
on herd Size: 20 from herds with 30-49 cows, 25 from herds with 50-99 cows, and 30

from herds with 100 or more milking cows.

62

Sample size

A sample size of 128 dairy herds was established for the study, based on the ability
to evaluate herd level prevalence rates of Campylobacter. Taking at least 50 samples per
herd would provide 95% confidence of detecting at least one positive animal per visit if
the within-herd prevalence is _>_ 5%, which agrees with reported prevalence rates, which
Should allow sensitivity of sampling given reported prevalence rates vary from 5% to

37% in individual dairy cattle (Hoar et al, 2001; Wesley et al., 2000).

Data collection

Data were collected using initial and bimonthly pre-tested questionnaires
administered in person. The initial questionnaires were designed to capture data
regarding herd management practices, herd inventory, animal housing, feed, water
systems, production, health, manure management, and antimicrobial use on the farm
being studied. On the bimonthly questionnaires, data collectors recorded information
about any changes in herd management practices, herd inventory, and antimicrobial use
that may have occurred after the previous sampling visit.

An ‘other animal’ index was developed as a measure of the presence of other
animals on the farm that have been reported as sources of Campylobacter (Harvey et a1,

1999; Engvall, et al, 1986; Penner and Hennessy, 1980):

63

Index H = Z(Swine,, + Poultry H + Geese”)

where:
SwineH = 1 if swine present on the farm, 0 if no swine present
Poultry” = 1 if chickens, ducks, turkeys or other poultry present on farm, 0 if not
present

Geese” = 1 if wild geese present on farm, 0 if not present

Values for the index ranged from 0 to 3.

Sample collection

All samples collected were identified by farm code, sample date, sample container
number and type of sample (animal identification or type of environmental sample).
Cattle were systematically selected for sample collection, and approximately 5 grams of
feces were collected per rectum and placed in sterile Whirl-pak® containers. All samples
were shipped in a Styrofoam cooler, packed with ice, and sent to a central laboratory at
Michigan State University. The samples were shipped within 24 hours of collection and

processed immediately upon arrival at the laboratory.

Sample processing

Fecal samples were prepared by the addition of approximately 30 m1 of phosphate
buffered solution, and then directly plated onto Campylobacter agar (BD Biosciences),
streaked for isolation, and incubated at 42°C in 5-10% CO2 for 48 h. If growth was

observed after 2 days, the isolate was subcultured onto a sheep blood agar (SBA) plate

64

and incubated at 42°C in 5-10% CO2 for 48 h. Gram staining, oxidase testing (BD
Biosciences), and hippurate (Remel) testing were performed. Motility testing was
performed by inoculating Mueller Hinton broth with a heavy inoculum of the suspect
Campylobacter, incubating for 48 h at 42°C in 5-10% CO2 , and examining the
suspension under bright field microscopy for characteristic darting motility. If the gram-
stain, oxidase test, or motility test were not indicative of Campylobacter, the sample was
recorded as negative. Hippurate testing was performed to distinguish C. jejuni from other

Campylobacter spp.

STATISTICAL ANALYSIS

Associations between individual animal Campylobacter status and possible risk
factors were assessed using logistic regression models with random effects (SAS PROC
MIXED, macro GLIMMIX). These models controlled for the effects of state, herd size,
and season, and included individual herd as the random effect term, to control for any
herd effect in the analysis. Initially, separate models were developed for each risk factor,
and factors that showed associations with Campylobacter status at p 5 0.2 were
considered for inclusion in the multivariable analysis.

Cows and calves differ physiologically in their response to Campylobacter
infection (Giacoboni et al, 1993; Grau, 1988), and on-farm management of these two
groups differs (types of housing, feeding practices, disease treatment, exposure to other
animals, etc.). Taking this into consideration, and based on differences in the apparent

prevalence of Campylobacter between cows and calves during analysis of these data

65

(Chapter 2), two separate models were developed: one for the cow population, one for
calf population. A list of risk factors used for the multivariable analysis is provided in
Table 3. Risk factors that were directly associated with the animal group being modeled
(e. g., washing calf housing in the calf model, dry lot housing in the adult model) were
included in the multivariable analysis. In addition, risk factors that could influence the
levels of Campylobacter in the other animal group were examined in the analysis. Since
both animal groups could serve as potential sources of Campylobacter for each other, the
possibility that these ‘indirect’ risk factors could influence rates in the group of interest
by affecting the quantity of Campylobacter present in the other animal group.

Multivariable logistic regression models with random effects were used to
identify the major risk factors associated with each animal’s Campylobacter status. All
variables identified in the initial analyses were included in the multivariable model.
Since herd size and state were confounders of several of the risk factors in the analysis,
both were included in the multivariable model to control for confounding. A backward
elimination procedure was used in order to find the best fitting model in each case: if
removal of a potential confounder resulted in a 10% or more change in the odds ratio of
the risk factors of interest (excluding state, herd size and season), the variable was

retained in the model to control for confounding.

66

RESULTS

Study population

A total of 128 dairy herds from Michigan, Minnesota, New York, and Wisconsin
were enrolled in the study (Table 1). The average number of milking cows per herd in
Michigan, Minnesota, New York, and Wisconsin were 217, 169, 198, and 177,
respectively. A total of 25,121 samples from dairy cattle were sampled, of which 20,380
(89%) were from healthy lactating cows, and 5% and 7% of the cows and calves,
respectively, were sick (Table 2). The apparent prevalence of Campylobacter in this
study was 12%, with 14.4% of calves and 11.4% of cows with samples positive for
Campylobacter (Chapter 2).

The majority of lactating cows in this study lived in multiple housing (90%) in which
cows were always in close proximity to one another. Of the lactating cows that lived in
multiple housing, only 39% lived in dry lot housing and 35% had access to pasture. Less
than half of the lactating cows had inorganic bedding provided for them (36%).

Calves were housed in areas with other calves (43%) or separately (57%).
Approximately 50% of the calves did not have cleaned calf pens and the other 50% of
calves had their calf pens cleaned with either water or disinfectant. Around 4% of the
calves were exposed to inorganic bedding in the pens. And 85% of the calves were

exposed to milk buckets that were not washed between feedings.

67

Cow population model

There were individual animal and herd level risk factors associated with increased
risk for Campylobacter in adult cows. Individual animal factors associated with
increasing risk included an animal’s health status (being sick, a cull, or periparturient)
and age. Herd level risk factors associated with increased Campylobacter risk included
increased levels of calf scours on the farm, the use of inorganic bedding for lactating
cows, pasture access by any cattle on the farm, pasture access specifically for dry cows,
higher percentages of the milking herd coming from off-farm sources, protecting feed
only from moisture, using a bucket loader for feed, and availability of sick animal
housing on the farm (Table 4). Risk factors associated with the reduced risk for
Campylobacter included high bacterial counts in bulk tank milk, the use of dry lot
housing for lactating cows, washing calf housing between animals, and using the same
loader bucket for feed and manure. Risk factors that were not significant, but retained in
the model to control for confounding, included group housing for lactating cows and

cattle access to surface water (ponds, creeks, etc).

Calf population model

In the model for pre-weaned calves, factors associated with increased Campylobacter
risk included increased levels of calf scours on the farm, herd access to surface water
(ponds, creeks, etc.), pasture access by any cattle on the farm, using the same loader
bucket for feed and manure, the use of inorganic bedding for calves, and high bacterial
counts in bulk tank milk (Table 5). Risk factors associated with the reduced

Campylobacter risk in calves included access to dry lots by any cattle on the farm,

68

cleaning calf milk buckets between feedings, spreading Slurry on fields for manure
disposal, and possible contact with other animals on the farm. Confounders that were
included in the model were calf health status, organic herd certification, and higher

percentages of the milking herd coming from off-farm sources.

Comparison of cow and calf population models

Risk factors that were retained in both the cow and calf population models included
increased levels of calf scours on the farm, access to surface water, washing calf housing,
the use of inorganic bedding, pasture access by any cattle on the farm, higher percentages
of the milking herd coming from off-farm sources, using the same loader bucket for feed
and manure, and high bacterial counts in bulk tank milk (Table 6). Both the cow and calf
population models showed an increase in the risk for Campylobacter when the level of
calves scours was high, inorganic bedding was used, the herd had access to pasture, and
higher percentages of the milking herd came from off-farm sources. A decrease in the
risk of Campylobacter was observed for both the cow and calf population model when
calf housing was washed. Risk factors associated with an increase in the risk of
Campylobacter in the calf model but with a decrease in risk for the cow model were herd
access to surface water, using the same loader bucket for feed and manure, and higher

percentages of the milking herd coming from off-farm sources.

69

DISCUSSION

When examining risk factors associated with the individual animal Campylobacter
status on dairy farms, it is helpful to view them in an epidemiological context, as being

measures of host (cattle), agent (Campylobacter spp.), or environmental factors.

The Cow Population Model

Host-related Risk Factors - Host related factors are those related to the general
health status of individual adult cattle. Factors in the multivariable analysis that were
host-associated were animal health status and cattle age.

Being classified as a non-healthy cow (sick, cull, or periparturient) was associated
with increased risk of Campylobacter. Sick cattle were considered sick because of
clinical signs of illness, excluding any localized infections. For cattle in the Sick/cull
category, illness may weaken the immune system, creating opportunities for
microorganisms to more readily establish themselves in an immune compromised animal
(Carter and Chengappa, 1991), and the majority of cattle in this classification (79%) had
some form of illness. Periparturient cows, cows within 14 days before or after calving,
have increased stress levels associated with pregnancy, calving and early lactation, which
would explain why Campylobacter was more commonly found in these animals (Jones et
aL,1999)

The effects of age on the likelihood of Campylobacter shedding are probably due to
the association between age and an individual animal’s immune status. As cattle age,

their exposure to a wide range of diseases increases, which, in turn, aids in the

70

development of immunity to a variety of agents. Consequently, younger cattle have an
increased risk for Campylobacter infection because of the lack of this acquired immunity.
As cattle mature, their immune responses become more effective than younger animals
(particularly calves), and they are better able to fight infection regardless of their prior
exposure. The overall result would be that their risk of Campylobacter colonization
would decrease, and the likelihood that they would be shedding detectable levels of
Campylobacter would also decrease (Benj aminin and Leskowitz, 1991; Weijtens, 1993).

Agent-related Risk F actors- Agent-related risk factors are those that are related to the
agent in question, Campylobacter. A risk factors in the multivariable analysis that was
agent-associated were the percentage of cattle from off-farm sources. In this study,
increasing the percentage of cattle introduced from sources off the farm increased the
likelihood for individual cattle to become Campylobacter positive. One basic cattle
management practice known to reduce the risk of imported infection is to maintain a
“closed” herd, in which no cattle are brought from outside the operation into the herd
(Etgen et al, 1987). Imported cattle can introduce new strains of bacteria into a herd that
was not previously exposed, allowing the bacteria to quickly spread within this naive
population. Also, the stresses associated with transporting animals can cause increased
shedding of bacteria (Stern et a1, 1995), which would provide a greater possible source of
infection for cattle already on the farm, and making it more likely to isolate
Campylobacter from these transported animals.

Environment-related Risk Factors - Environment-related risk factors are those that
are related to the increasing the likelihood of a host becoming exposed to the agent. This

exposure can either be direct (animal to animal), or indirect (exposure through

71

contaminated feed, water, or housing). Environmental risk factors supporting direct
exposure between cattle in this study included the use of dry lot housing for lactating
cows. Environmental risk factors supporting indirect exposure included the use of
inorganic bedding for lactating cows, the levels of diarrhea reported in calves on the
farm, washing calf housing with water, feed storage that protected against moisture only,
the use of loader buckets for feed, the combined use of a loader bucket for feed and
manure, and high bulk milk bacteria counts. Factors that decreased risk were the use of
dry lot housing for lactating cows, washing calf housing with water, and the combined
use of a loader bucket for feed and manure. Risk factors that were associated with the
increased risk of Campylobacter were the use of inorganic bedding for lactating cows,
feed storage that protected against moisture only, and the use of loader bucket for feed.

Dry lot housing is a form of multiple-animal housing for cattle. Cattle in this
environment are in close contact with one another, which would cause rapid transmission
of the bacteria, but no associated increase in risk for Campylobacter shedding was found
in this study. Instead, cattle in dry lot housing had decreased risk for Campylobacter.
Any environmental contamination by fecal material in a dry lot would be exposed to
sunlight, wind, and other environmental factors that would reduce the survivability of
Campylobacter outside the host, and consequently reduce the risk of infection. Also, this
association could be due to the density of cattle in housing. While there may be direct
contact between cattle in any group housing environment, the stocking density of cattle in
a dry lot will be lower than in cattle group housed in free stalls in a building, and

lowering the density of potential hosts will reduce disease transmission in the dry lot.

72

In this study, inorganic bedding was defined as bedding that consisted of inorganic
material such as sand, rubber tires or mats, mattresses, crushed limestone, etc. These
materials were washed or changed much less frequently than organic bedding (i.e., straw,
sawdust, etc.) (Chapter 2), which would result in fecally-contaminated bedding being
used for long periods of time. This would increase the likelihood for cattle to become
exposed to manure contaminated with Campylobacter. On the other hand, washing calf
housing decreased the risk of Campylobacter. Routinely washing calf housing would
decrease levels of fecal contamination, which would, in turn, decrease the risks of
infection with Campylobacter.

The use of pasture housing for dry cows and pasture availability were associated
with an increased risk for Campylobacter. Pasture access provides a unique opportunity
for fecal-oral contamination due to cows defecating in areas that may be grazed by their
herd-mates. This finding agrees with observed increases in Campylobacter prevalence
found when Sheep grazed pastures in comparison to being fed hay and silage diets (Jones
et al., 1999). Another possible exposure to cattle on pasture could be wildlife reservoirs
of Campylobacter. While the parameters of this study did not attempt to measure
wildlife contact with cattle, other authors have documented the carriage of
Campylobacter by rodents (Annan-Prah and J anc, 198 8), insects (Gregory et a1, 1997;
Refregier-Petton et a1, 2001), and birds such as starlings and gulls (Stanley and Jones,
1998; Piddock et al., 2000; Craven et a1. 2000). These same environmental risk factors
may also be associated with the increased risk observed with feed storage that was only

protected from moisture, but not pests.

73

Higher levels of scours in calves may be an indirect indicator of higher levels of
pathogens on the farm. Calves, with their new and relatively weak immune systems,
would Show evidence of infection to pathogens that would not be observed in adult cattle
that have better-developed immune systems, and may have already acquired immunity to
those specific pathogens.

There were several environmental risk factors associated with the potential
contamination of feed by Campylobacter through feed storage and handling. Feed storage
that only protected feed from moisture (not from pests like rodents, insects, and wild
birds) was associated with increased risk for Campylobacter. From previous studies,
rodents (Annan-Prah and J anc, 1988; Kapperud et al, 1993; Evans and Sayers, 2000),
insects (Gregory et a1, 1997; Refregier—Petton et al, 2001), and birds (Whelan et al, 1988)
have been identified as important sources of Campylobacter on the farm.

The use of loader buckets for both manure and feed transport were associated with a
decrease risk of Campylobacter. The majority of farms that reported using the same
loader bucket for feed and manure also reported washing the loader bucket between uses,
which would improve the overall hygiene of the loader buckets and decrease
opportunities for fecal contamination during feed handling. However, the use of a loader
bucket for feed was associated with an increased risk of Campylobacter. The reason for
this association is unclear, and further work is needed to understand the impact of the use
of loaders for handling feed and/or manure on the farm. It is possible that, if loader
buckets were used for feed handling alone and are not carefully washed, there would be

increased chances for contamination of feed from the environment.

74

Another environment-related risk factor associated with increased risk of
Campylobacter in this study was high levels of bacteria in bulk tank milk. The
association between bulk tank milk bacteria counts and Campylobacter risk is not clear.
Higher bacterial levels would be expected in herds with poorer overall herd health, but
this association is not seen. It is possible that bacterial levels in bulk tank milk may be
due to poor hygiene during milking. Additional research into the association between

bulk tank milk bacteria counts and cattle risk for Campylobacter is needed.

The Calf Population Model

Host-related Risk Factors - Factors in the multivariable analysis that were host-
associated were the levels of calf scouring on the farm, and calf health status. As
described under the cow population model, higher percentages of calves scouring on a
farm increased the risk of Campylobacter in calves. For adult animals, levels of calf
scours could be an indirect measure of pathogen load on the farm, but in the calf model,
the level of calf scours reported at the beginning of the study may be an indirect measure
of overall calf health. When more calves are sick, the chance for the spread of disease
increases, either through direct contact with sick calves in group housing, contact with
contaminated environments, or from handling by farm workers that become contaminated
while handling Sick calves and do not use any precautions to prevent the spread of
disease. Since the majority of farms in this study housed calves individually, exposure
from contaminated environments or through poor hygiene practices are the more likely

sources of infection for these calves.

75

Agent—related Risk Factors - In the calf model, agent-related risk factors were those
associated with the introduction of novel Campylobacter to calves. The risk factor in the
calf multivariable analysis that was agent-associated was the presence of other Species
known to be intestinal carriers of Campylobacter (Harvey et al, 1999; Engvall, et a1,
1986; Penner and Hennessy, 1980). It was expected that Campylobacter prevalence
would increase when these other animals were present on the farm, but this was not
observed. It is difficult to conclude why the presence of these animals was associated
with reduced Campylobacter prevalence. It is possible that the index used was not
sufficiently sensitive to the risk that these other species posed to the cattle herd. A more
likely explanation of this finding is that the presence of various other livestock Species on
a dairy farm may be associated with other styles of overall farm management that
function to reduce the levels of Campylobacter on the farm. Farms that maintain a
variety of different livestock species on their facilities may reflect a more diversified
approach to livestock farming, and may not manage their dairy operation as intensely as a
farm whose sole occupation is dairy production.

Environment-related Risk Factors - Environment-related risk factors associated with
Campylobacter risk in calves can be divided into two groups: factors that were directly
associated with calves and calf management; and factors that were not directly associated
with calves, but did influence calf risk for Campylobacter. Calf-related environmental
risk factors included the use of inorganic bedding for calf housing, washing calf milk
buckets, and high levels of bacteria reported in bulk tank milk. Other environmental risk

factors included herd access to surface water, pasture, and dry lot housing, the use of the

76

same loader bucket for both feed and manure, and manure disposal by spreading slurry
on fields.

When examining calf-related environmental risk factors, washing calf milk buckets
reduced risk for Campylobacter, while the use of inorganic bedding and high levels of
bacteria in bulk tank milk were associated with increased calf risk. Washing milk
buckets between feedings would reduce the chance of spreading infection through milk
that may become contaminated from environmental sources while in the bucket.

As described in the Cow Population model, the effect of using inorganic bedding for
calves probably increases risks for Campylobacter exposure due to increased fecal
contamination, since the bedding is changed or washed less frequently than organic
bedding.

If milk with high levels of bacteria is fed to calves, they are more likely to become
infected with Campylobacter and any other bacteria in the milk. In this study,
Campylobacter was isolated from both milk filters and bulk tank milk (Chapter 2),
making this highly likely. Interestingly, no statistically Si gnificant associations were
found between calf Campylobacter and the feeding of waste milk to calves.

Environmental risk factors that are not directly associated with calves or calf
management would increase the risk for calves to become infected by increasing herd
exposure to Campylobacter through fecal contamination. Risk factors associated with
increased Campylobacter risk included herd access to surface water, herd access to
pasture, and the use of the same loader bucket for feed and manure, while risk factors
associated with reduced Campylobacter prevalence included herd access to dry lots, and

spreading slurry on fields for manure disposal.

77

Contaminated water has been reported as a source of Campylobacter for man
(Piddock et a1 2000, Evans et al, 1996) and animals (Pearson et a1, 1993; Gregory et a1
1997). Since C. jejuni can be isolated from surface water for up to four days when
temperatures exceed 20°C (Korhonen and Martikainen, 1991), contaminated surface
water is a likely source of Campylobacter in cattle that have access to surface water. Any
surface water that cattle have contact with may become contaminated with cattle feces,
causing the spread of any Campylobacter in these feces. As greater numbers of adult
cattle carry Campylobacter, the likelihood of bacterial shedding is increased, and the risk
for calves acquiring the bacteria is increased. The associations between Campylobacter
in adult cattle and surface water was evaluated, but was not significant in the
multivariable analysis.

Pasture access was associated with the increase in Campylobacter. Pastured cattle
will graze on grass, which can easily be contaminated by feces, thereby creating more
opportunities for Campylobacter ingestion and spread. Loader buckets used for handling
both feed and manure increases the risk of feed contamination with Campylobacter if the
bucket is not thoroughly washed between uses.

As in the adult cow model, herd access to dry lots decreased in the risk of
Campylobacter, presumably through the development of herd immunity in the cattle in
dry lot housing. Additionally, spreading manure Slurry on fields removes manure from
animal housing areas, which would reduce chances of exposure to Campylobacter, and

subsequently reduce prevalence in the calf population.

78

Comparison of Cow and Calf Population Models

There were five risk factors present in both models that had Similar effects on the
risk of Campylobacter in both models. These risk factors included the increased
percentage of scouring calves in the 6 months prior to the beginning of the study, the use
of inorganic bedding, herd access to pasture, the increased level of imported milking
cows, and washing calf housing. The effect of the percentage of scouring calves was
fairly consistent between both models (cow model OR. = 1.02, calf OR. = 1.04, Table
6). The effect of the level of imported cattle in the herd, and washing calf housing were
similar in magnitude between both models (imported cows: cow OR. = 1.05, calf OR. =
1.03; washing calf housing: cow OR. = .76, calf OR. = .82; Table 6), even though these
risk factors were significant in the cow model but not Significant in the calf model. The
effect of the use of inorganic bedding was slightly higher in the calf model (OR. = 1.9)
compared to the cow model (OR. = 1.4), while the effect of herd pasture access was
notably higher in cows (OR. = 2.5) than in calves (OR. = 1.5).

In risk factors where effects were consistent between cow and calf model, it is
interesting to note how the magnitude of effect differed between the models. Risk factors
directly associated with the cattle group being modeled (cow model: level of imported
cattle and pasture access; calf model: percent of calves scouring, washing calf housing,
use of inorganic bedding) had higher magnitudes of effect than factors not directly
associated with the cattle group being modeled. These factors would directly affect the
age group being evaluated in the model, so it would be expected that these direct effects

would be stronger than any indirect effect of a risk factor on the other cattle group.

79

There were three risk factors present in the Cow Population and Calf Population
models that had opposite effects on the individual animal risk of Campylobacter. Surface
water access, the use of a loader bucket for manure and feed, and high bulk tank milk
bacterial count increased the risk of Campylobacter in the Calf Population model, but
decreased the risk of Campylobacter in the Cow Population model. Calves and cows are
managed differently on the farm, so the effects of the management risk factors may
function differently in these two groups, as described above. Differences in cow and calf
immune status may also result in changes in the effect of different risk factors. Additional
research is needed in this area to determine whether the effects of these and other
potential risk factors for Campylobacter shedding are influenced by an animal’s immune

status.

CONCLUSIONS

As previously mentioned, this study is a subset of a larger study investigating the
ecology and dynamics of Shedding of Campylobacter on conventional and organic dairy
farms. For this study, we were able to collect more than 25,000 fecal samples for
bacterial isolation from 128 dairy farms in 4 states over a 12-month period, which
allowed for the opportunity to look at the associations between various risk factors and
Campylobacter shedding in dairy calves and milking cows. While there may be areas in
which more detailed information about risk factors is needed, this study provided
information that can be used to direct future research on specific herd management

practices.

80

In summary, risk factors associated with reduced health of the herd were
associated with increasing prevalence of Campylobacter. Herd management risk factors
associated with increased Campylobacter prevalence were those which increased risk of
fecal contamination and exposure for cattle, and increased calf exposure to infected
animals. Management risk factors associated with decreased risk for Campylobacter
were those which reduced fecal contamination risks, and increased the opportunities for
adult animals to develop natural immunity to Campylobacter. The findings of this study
were by no means exhaustive, but the specific risk factors identified in this study can be
used to develop programs aimed at reducing the risk of infection on farms. Additional
targeted research on management strategies to reduce Campylobacter shedding on dairy
farms will provide the dairy industry with the tools necessary to provide a safer milk

supply to the food chain.

81

Table 1. Description of farms by herd Size and state

 

 

Herd Size'I Michigan Minnesota New York Wisconsin
30 — 49 O 6 4 6
50 — 99 10 9 9 9
100 -— 199 1 1 8 9 8
200 + 11 9 10 9
Total 32 32 32 32

a — Number of cows in milking herd

82

Table 2. Cattle population in the analysis

 

 

Age Group Health Status Total number Campylobacter +
Healthy 4398 14.6
calves Sick 343 12.2
Healthy 19303 1 1.3
Cows Sick or Cull 1227 14.1
Periparturient 263 8 15 .4

 

83

Table 3. Risk Factors used in Cow and Calf Population Multivariable
Analyses

Risk Factor Coding Used in Analysis

 

General Herd Management
Herd certified Organic 1 = yes; 0 = no

Cattle-related Factors

Health Status 1 = cull / Sick; 2 = Within 14 days before
or after calving; 3 = healthy

1 = bred heifers; 2 = 15‘ lactation; 3 = 2nd

Age lactation; 4 = 3rd — 4‘h lactation; 5 = 5th
lactation and above

Percent of herd calves scouring Continuous (0 - 100%)
High somatic cell count (> 30,000) 1 = yes; 0 = no
High bacteria counts in milk (> 1 = yes; 0 = no

300,000)
General Cattle Housing

Lactating cows in dry lot housing 1 = yes; 0 = no
Any cattle kept in dry lot housing 1 = yes; 0 = no
All age groups with access to dry lots 1 = yes; 0 = no
Lactating cows in multiple housing 1 = yes; 0 = no
Calves housed on inorganic bedding 1 = yes; 0 = no
Lactating cows on inorganic bedding 1 = yes; 0 = no
Herd has pasture access 1 = yes; 0 = no
Dry cows on pasture 1 = yes; 0 = no

 

84

Table 3. Risk Factors used in Cow and Calf Population Multivariable
Analyses (cont.)

 

Risk Factor Coding Used in Analysis
Biosecurity and Sanitation
% milking herd imported Continuous (0 - 100%)
Feed protected fiom moisture only 1 = yes; 0 = no
Calf housing washed with water 1 = yes; 0 = no
Calf milk buckets washed 1 = yes; 0 = no
Loader used for feed 1 = yes; 0 = no
Wash feed loader buckets 1 = yes; 0 = no
Contact with other animals Categorical index (0 — 3)
Manure pack used 1 = yes; 0 = no
Slurry spread on fields 1 = yes; 0 = no
Sick animal housing available 1 = yes; 0 = no
Herd has access to surface water 1 = yes; 0 = no

 

85

Table 4. Final multivariable logistic regression model with random effects for
prevalence of Campylobacter, for cows (n = 20,380), controlling for herd

size, state, and season

 

 

 

 

 

 

Risk Factor
Cattle-related factors
Cattle health status (baseline: healthy)
Sick or culls
Within 14 days before or after calving
Age group (baseline: 5+ lactations)
Bred heifers
1" lactation
2“d lactation
3rd - 4‘h lactation
Percent of herd calves scouring (for 10% change)

High bulk tank milk bacteria count

Cattle housing
Lactating cows in multiple housing
Lactating cows in dry lot housing
Lactating cows on inorganic bedding
Any pasture availability
Dry cows on pasture

Access to surface water

Biosecurity and Sanitation
% Milking herd imported (for 10% change)
Feed protected from moisture only
Calf housing washed/w water
Loader used for feed
Same bucket for feed, manure

Sick animal housing available

Risk Ratio

1.25"
140*"
2.52***
1.88***
156*”

1.17

1.02*
.82“

1.19
.89*
1.38***
2.52"”""I
152*"
.91

1.05***
1.36***
.76***
1.18*
.84"
1.50***

95% CI.

1.08 - 1.45
1.27 - 1.55
1.79 - 3.54
1.60 - 2.22
1.32 - 1.84
.99 - 1.39
1.00 - 1.03
.70 - .95

.99 - 1.43
.80 - .99
1.24 - 1.53
1.98 - 3.21
1.20 - 1.94
.82 - 1.02

1.04-1.07
1.16-1.60
.68-.85
1.02 -1.36‘
.75 -.93
1.35 - 1.66

 

Model -2 log L = 99216.4

*-p50.05; **-p_<_0.01;

86

*** -pg0.001

Table 5. F inal multivariable Logistic regression model with random effects for
prevalence of Campylobacter, for calves (n = 4,741), controlling for herd size,

state, and season

Risk Factor
Cattle-related factors
Percent of herd calves scouring (10%)

Sick calf

Cattle housing
Herd has access to surface water
All age groups with access to dry lots
Calf housing washed/w water

Herd has pasture access

Biosecurity and Sanitation
Organic farm
% Milking herd imported (10%)
Wash milk buckets

Slurry spread on fields

Same loader bucket used for feed & manure

Inorganic bedding used for calves

High bulk tank milk bacteria count

Other animals (swine, poultry) present on farm

Risk Ratio

104*“

.78

1.28**
.77*
.82

l.45***

1.19
1.03
.76”
.82*
1.19*
187*"
1.56***

.78"

95% CI.

1.02 -1.06

.58 - 1.04

1.06- 1.53

.61 - .97

.67 - 1.00

1.18-1.78

.95 - 1.47

1.00 - 1.06

.64 - .90

.69 - .98

1.00 - 1.42

1.32 — 2.64

1.24 - 1.97

.68 - .91

 

Model -2 log L = 22,3584

*-p50.05; **-p_<_0.01; ***-p50.001

87

Table 6. Comparison of risk factors between Cow and Calf Logistic regression
models for Campylobacter status, controlling for herd size, state, and season

Cows (n = 20,380) Calves (n = 4,741)

Risk Factor RR. 95% CJ. RR. 95% CJ.

 

Cattle-related factors

Percent of herd calves scouring (10%) 1.02,, 1.00 - 1.03 1.04,," 11.0026-
Cattle housing
Herd has access to surface water .91 .82 - 1.02 1.28“ 11.0563-
Calf housing washed/w water .76*** .68 - .85 .82 .67 - 1.00

Use of inorganic bedding 1.38**“' 1.24 _ 1.53 1.87*** 1.32 -

2.64

Herd has pasture access 252*“ 1.98 _ 3.21 1.45,," 11.1788-
Biosecurity and Sanitation

% Milking herd imported (10%) 1.05,," 1.4 _ 1.07 1.03 11.0316-

Same bucket used for feed & manure .8 4“ .75 _ .93 1.19,, 11.022-

High bulk tank milk bacteria count .82" .70 _ .95 156*" 11.2947-

 

*-p50.05; **-p50.01; ***-p50,001

88

OVERALL CONCLUSIONS

A sample of 25,155 cattle from 128 randomly selected dairy farms from
Michigan, Minnesota, New York and Wisconsin were used to assess the associations
between the apparent period prevalence (APP) of Campylobacter at the farm level, and
the risk for shedding Campylobacter at the individual animal level. The overall APP of
Campylobacter was 12%, and ranged from 5% to 15% per herd. Calves had higher
Campylobacter APP than adult cattle, Sick adults had higher APP than healthy adults, and
APPS were highest in the winter and lowest in the summer.

In general, factors associated with poor farm hygiene and biosecurity were
associated with increasing prevalence and risk of Campylobacter, in both the herd-level
and individual-level analyses.

Herd management risk factors associated with higher APPS were those that
increased risk of fecal contamination and increased calf exposure to infected animals.
Factors associated with higher APPS include the use of infrequently-changed inorganic
cattle bedding, the percentage of cows in the milking herd from off-farm sources, cattle
access to surface water, and milk with high bacteria counts. Inorganic bedding was
changed less frequently than other types of bedding, which would allow contaminated
feces to accumulate in the housing environment. Introducing a high percentage of the
milking herd from outside sources would increase the chances of introducing foreign
organisms into the herd, which could rapidly spread through the naive herd population.
Surface water is commonly contaminated with feces, which allows the opportunity for

cattle to ingest contaminated water.

89

Herd risk factors associated with decreased APPS were those that decreased
opportunities for Campylobacter contamination and survival in the environment. Factors
associated with lower APP include washing calf housing, washing feed loader buckets,
housing lactating cows on dry lots, and spreading manure Slurry on fields. Basic hygiene,
such as washing calf housing and washing feed loader buckets, decreases the risk of fecal
contamination through direct exposure of calves to manure, and avoiding feed
contamination in the loader bucket. Washing is particularly important when feed loader
buckets are also used to transport manure. Proper manure handling, such as removing
manure from cattle housing and spreading Slurry on fields, decreases the amount of feces
in the areas with high cow traffic, thereby decreasing the chances for cattle exposure to
fecal contamination. The use of dry lot housing influences Campylobacter prevalence in
several ways. Dry lot housing would decrease animal stress by stocking cattle at lower
densities than in barns, provide opportunities for improved herd immunity through direct
contact between animals, and the physical environmental conditions in dry lots do not
support the survival of Campylobacter outside the host.

In the individual level analyses, factors associated with animal health and factors
identified in the herd level analyses were associated with Campylobacter risk for the
individual animal. The individual animal level analysis also identified risk factors that
were associated with reduced odds of a cow or calf acquiring Campylobacter, and all of
these risk factors were similar to those identified under the herd level analysis. Since
significant differences were seen in the APP between calves and adult animals, separate
analyses were conducted for calves and adults. New factors associated with a greater risk

of Campylobacter included poor or stressed health status, and reported levels of calf

90

 

scouring at the beginning of the study. Poor health (disease) or stress (periparturient
cows) can cause the animal to have a weakened immune system, which would increase
the likelihood of Campylobacter shedding. High levels of calf scours may be an
indicator of a large volume of microorganisms on the farm, since calves are more likely
than adults to Show signs of illness because of their immature immune systems.

This study was able to utilize a longitudinal approach to investigating the
associations between Campylobacter and herd management practices on conventional
and organic dairy farms. The sample size achieved (25,155 cattle from 128 farms) and
the time period in which sampling occurred (a 10-month period) was an improvement
over many studies in the current literature. The study design and data collected allowed
us the flexibility to look at Campylobacter from both the herd level and individual animal
level. The herd level analysis offered a considerable amount of information on the risk
factors associated with Campylobacter prevalence within a herd, while the individual
level analysis provided additional risk factors that applied to an individual animal. We
were also able to conduct individual animal analyses by cattle age class, which targets the
identification of risk factors for each age class more specifically.

In summary, farm hygiene, to reduce on-farm contamination, and herd
biosecurity, to avoid the introduction of potentially harmful microbes to the herd, are two
extremely important areas that affect the prevalence of Campylobacter. This information
can be used to develop specific interventions to reduce herd levels of Campylobacter,
such as in controlling fecal contamination, which will not only reduce levels of this non-
pathogenic organism, but can also reduce levels of harmful bacteria (e. g. Salmonella

spp.) on the farm. Reductions in overall bacterial loads in cattle on the farm will also

91

 

help in reducing the levels of any bacteria that have developed resistance to antimicrobial
agents, a known animal and human health problem. Minimizing levels Campylobacter
on farms will reduce the reservoir of Campylobacter for introduction into the human food

chain, and result in a safer food supply.

92

APPENDIX A

Initial Questionnaire

Risk Factors for Salmonella and Campylobacter Infections and Drug Resistance in
Dairy Cattle

This in-person questionnaire is to be given once for each producer e.g., at the initial herd visit. A much
shorter questionnaire will be used to collect data that changes frequently.

Producer Information:

Farm name:

 

Owner(s) name:

 

Contact person or herdsman
(if different from owner):

 

Farm Address:

 

 

Business Address (if different from above)

 

 

 

 

 

Home Phone:( ) Fax:( )
Barn Phone:( )
E-mail:

 

Herd Veterinarian:

 

DHIA Number (if applicable):

 

Directions to farm:

 

 

Person to whom survey is administered

 

Survey administrator

Date of next visit

93

l.

A. Inventory—Herd Size

A5 of today, what is your inventory of the following groups of dairy
cattle?

 

Lactation 1"

Lactation 2 & up“

Total

 

>

. Milking cows

2

 

Dry cows

 

 

. Total cows (add totals

of A. and B. above)

 

one:

. Preweaned (milk-fed)

heifer calves

 

l'l'l

. Weaned replacement

calves and heifers"

 

Other youngstock*"

 

. Bulls #00.

II

 

 

. Total cattle (Add

C-G above)

 

 

 

lactation just completed for dry cows.

" Lactation numbers here refer to the current lactation in the case of milking cows and to the

" “Weaned replacement calves and heifers” here means all female animals that will be kept as

replacement cows, have not yet calved, and are no longer receiving milk or milk replacer as
part of the diet.

"'" “Other youngstock” here means all animals that will not be kept as replacements that are

weaned or will be kept up to or past weaning (e.g., steers and heifers raised for beef—exclude
calves that are only kept for a short period after birth)

saved for breeding purposes)

94

”" Include only bulls kept for breeding purposes (e.g., breeding age bulls or younger bulls being

 

As of today, how many of the total milk cows (both milking and
dry) were:

(NOTE: Add up the total cows in 1.C. and compare to 2D. as a check
before moving on to next page. These numbers should be the same—if

not, investigate to see where the problem is)

A. Born and raised on this operation? (refers to all sites
managed by this operation) ......................................................................... '3 head

B. Born here but raised elsewhere? (refers to contract rearing:

in case they have done this in past but are not now) .................................. ” head
C. Not born on this operation? ......................................................................... '5 head
D. Total ofA. + C. (Should equal 1.C. above.) ................................................ '6 head

95

3. This question refers to animals other than dairy cattle on this
operation.

Within the last 12 months, have any of the following types of animals been present on this operation?
If so, please indicate whether these animals had physical contact" with any of this operation’s dairy
cows or heifers, or their feed, minerals, or water supply.

 

 

 

Present on operation? Physical contact“?
17
A. Beef cattle? D Yes D No DYes E] No
B. Chickens, turkeys,
domestic geese, or other D Yes D No D Yes D No

poulty?
C. Horses or other equines

(such as ponies, D Yes D N0 [1 Yes D No

donkeys, mules, burros,
etc.)?

D. Pigs? D Yes D No D Yes D No

B. Sheep? D Yes E] No D Yes D No
F. Goats? D Yes [:1 No [:1 Yes [:1 No

G. Farmed (confined to a
pen) exotic animals
(such as deer, llamas,

ostriches, etc.)? [:I Yes D No DYes D N

 

 

 

 

 

 

 

 

 

o
Specify:

H. Dogs? [:1 Yes [:1 No [:I Yes [:1 No
1. Cats? D Yes D No DYes D No
.1. Wild geese? I: Yes D No D Yes D No

 

K. Other animals?

Specify:

_ D Yes D No D Yes D No

Include Nuisance
Birds

 

 

 

 

 

 

"‘ As used here, “physical contact” means nose-to-nose contact or sniffing/touching/licking each
other, including through a fence.

96

B. Herd Expansion Status

4. Were any of the following groups of animals brought onto this operation from outside
sources during the last 12 months?

 

 

 

 

 

 

 

 

 

 

 

 

IF YES, IF YES.
IF YES, How many of On average, how
Brougtlhggnto How these animals long were they
I ’ many? were isolated“ isolated" (in
upon arrival? days)?
A. Preweaned
(milk-fed) L_—Ies [110 Days
calves?
B. Weaned
dairy Des Clio Days
C. Dairy
.,,,,. Des Do D...
D. Bulls? Des Do Days
B. Other
cattle, Elie-t Do Days
E. Total. ' “ “j if ’

 

" “Isolated” here means that the animal(s) is held for a period of time in a separate pen or other
facility where nose-to-nose contact with cattle in the existing herd is prevented.

5. In the last 12 months, what is the largest number of dairy cows or weaned heifers that were

introduced to the herd from outside sources within a period of one week.

 

C. Housing

head

6. Which one of the following types of milking facilities did this operation primarily use
during the past 12 months? (Circle the appropriate letter A-D)

A. Pit parlor?

Flat parlor or step—up milking facility?

B
C. Tie Stall or stanchion barn milking facilities?
D

Any other type of milking facility? (specify)

97

 

7. What housing facilities did this operation use during the past 12 months for the following
(check all that apply):

Tie Stall or Calf is tied in Individual Multiple
S tanchion stanchion or animal animal
tie stall barn area" area‘"

(for single
. l Freestall

(milk-fed)
dairy

dairy calves

C. Lactating
cows?
D. Maternity

 

" “Maternity housing" here refers to where cows normally calve.

*" “Individual animal area” here refers to a pen housing only one animal (e.g., individual calf pen)
that is not covered by one of the previous options (e.g., if “hutch” has been selected, do not also mark
“individual animal area" to refer to hutches).

‘"” “Multiple animal area” here refers to a pen housing multiple animal (including “super hutches")
that is not covered by one of the previous options (e.g., if “freestall” has been selected, do not also mark
“multiple animal area" to refer to freestalls).

8. During the past 12 months, approximately how many months of daily access to outside
areas did the following groups of dairy animals have? (Enter “0" if no access)

 

 

 

 

 

 

 

 

 

 

 

 

Pasture
Dry 10’ Does not provide at least Provides 2 90% of
90% of roughage in ration) rouggge in ration
A. Weaned dairy heifers? Months months months
B. Lactating dairy cows? Months months months
C. Dry cows? Months months months
D. Maternity, close-up,
or recently fresh cow Months months months
housing?
9. Is maternity housing" in a separate pen or facility from Cl C]
other lactating cows? Yes No

 

" “Maternity housing" here refers to where cows normally calve.

98

10. Which of the following bedding types are typically used for the following groups of
animals? Mark bedding types for each group of cattle using letters A-F corresponding to
how often the bedding is changed. (e.g., if inorganic bedding for lactating cows is changed
monthly, but organic bedding for lactating cows is changed every 2-3 days, put “B” in
“other organic bedding” column and “E” in “inorganic bedding” column for lactating

 

 

 

cows.)
For each bedding type, put a letter A-F (select from list below)
corresponding to how often the bedding is chanjed or added to
. Other organic Inorganic
Dmd mm bedde bedde
Lactating cows

 

Maternity, close-up, or
recently fresh cows

 

 

 

 

 

 

 

 

Sick cows
Preweaned (milk-fed)
calves
A. Daily.
B. Every 2-3 days.
C. Weekly (more than 3 days, less than 8 days)
D. 2-3 times per month
E. Monthly
F. Greater than monthly

I

“Organic bedding” here includes any organic materials used for bedding, such as straw,
sawdust, newspaper, corn cobs or stalks, excluding dried manure.

"" “Inorganic bedding” here includes any inorganic materials such as sand, rubber tires or mats,
mattresses, crushed limestone, etc.

D. Feed and Water System

1 1. Do you feed a total mixed ration (TMR) to
lactating dairy cows? .................................................. D Yes D No

99

12. In the last 60 days, which of the following feeds have been used in the following groups of
dairy animals? Include only purchased feeds or feeds obtained from off-farm sources.

 

 

 

 

 

Check all that apply
Hi h-Producin 0‘1““ Dr
Type of Feed C g * g Milking y
ows Cows
Cows“

A. Whole cottonseed/hulls
B. Cottonseed meal
C. Whole soybeans or soybean meal
D. Bakery by-products

 

1T1

Brewers by-products (includes distillers’

ains)

 

F. Blood meal

 

G. Meat & bone meal (e.g., porcine-only or
equine-only)

 

G. Milk products (e.g., whey)

 

H. Tallow/animal fat

 

1. Other protein meal (e.g., meal from fish or

poultry)
Pleasespecify

 

 

 

 

 

 

 

* If high-producing cows are not fed differently from other cows, put N/A in “Other Milking Cows”
column.

13. The following questions refer to the storage areas used for protein and concentrates fed to

 

dairy cattle.
Is storage area for this Does storage area Does storage area for this
feed type in an for this feed type feed provide protection
enclosed building or provide protection Against birds or rodents?
other enclosed against moisture?
structure?

 

A. P ' Y N Y N Y N
feedsrotem es D o [:1 es [:1 o D esD D

 

B. Yes D No D YesE] No D YesD NOD

Concentrates

 

 

 

 

 

 

100

 

14.

15.

Which of the following coccidiostats or ionophores, if any, do you normally use for the
followinggroups of animals? Include products used in feed, water, or milk replacer.

 

Preweaned
(milk-fed)
calves

_ Weaned calves
up to breeding

Heifers
alter
breeding__

 

Deccox

(or other decoquinate product)

 

Rumensin (or other monensin product)

 

Bovatec (or other lasalocid product)

 

Corid

(or other arrrprolium product)

 

Sulfaquinoxaline (many oral products)

 

 

Other (Please
specify)

 

 

 

 

During the last 12 months, did cows drink from the following (check all that apply):

 

Milk
cows

Dry

COWS

Frequency
cleaned” (times
per year)

Frequency
disinfected“
(times per year)

List
disinfectant

 

. Automatic waterer—

for individual cows
(each has own cup or
one cup shared by
two cows)

Times/year

Times/year

 

. Automatic waterer—

cows drink
individually, but
waterer shared by
STOUP

Times/year

Times/year

 

. Water tank—

multiple cows can
drink at once

Times/year

Times/year

 

. Lake, pond, stream,

river, etc.—
occasional use only

 

. Lake, pond, stream,

river, etc—seasonal
main source (e.g., if
primary source of
water in summer is
lake, pond, river, etc)

 

 

Other: Please
Specify

 

 

 

Times/year

 

Times/year

 

“ “Cleaned” here refers to removal of water from waterer and removal of scum or feed

accumulation—regardless of whether a disinfectant is used.

 

” “Disinfected” means that after cleaning, a chemical disinfectant is used to sanitize waterer.

101

 

 

16.

17.

18.

19.

20.

Is the water that dairy cattle drink usually chlorinated? D Yes D No

What is the source of drinking water for cows? (Check all that apply)

 

A. Well C. Surface water (stream, lake, spring, etc.)
B. Municipal water D. Other (Please specify)
15 the ration for close-up dry cows different from the ration for far-off
dry cows (i.e., does this operation have a transition/close up ration)? D Yes [:I No

Does this operation normally feed anionic salts in transition cow diets
(e.g., during the last 2 to 3 weeks of gestation) Common anionic salts
are the sulfates or chlorides of magnesium, calcium, or ammonium?. D Yes El No

E. Calf Management and Feeding

Which one of the following methods is used most frequently for the first feeding of colostrum to
newborn dairy heifer calves? (Colostrum is the first milk produced after a calf is born.) (Circle
the appropriate letter A-D)

A. Calf is left with cow to nurse for a period of time (e.g., for 2—4 hours)
B. Hand feeding from bucket or bottle
F C. Hand feeding using esophageal feeder

D. Do not get colostrum

 

 

21.

 

Answer #21 only if B or C is circled.

 

 

How much colostrum is normally fed during the first 24 hours? (A calf
bottle is typically 2 quarts) (Circle the appropriate letter A-C)

A. Two quarts or less
B. More than 2, but less than 4 quarts

C. Four quarts or more

102

22. During the past 60 days, what types of grill; have usually been fed to preweaned calves that are
kept up to weaning, after they have received colostrum? Do not include calves (e.g. bulls) that
are kept for only a few days, and do not include diets that are not fed as a usual practice (e.g., if
waste milk is always fed to calves whenever available, mark “yes” for “B” regardless of the
number of times it was fed in the past two months. On the other hand, if waste milk was
discarded more often than it was fed, mark “no” for “B”).

Included in diet? (Check If A or B is YES,

all that apply) Is the milk pasteurized?

 

 

A. Whole milk from untreated“

 

cows Yes D No Yes E] NOE]
B. Wh 1 '1k fr (1"
(wait: nfiiilk) 0m “Gate COWS Yes D No Yes D NOD

 

C. Milk replacer without antibiotics Yes [I No

 

 

1:1 CID [11:1

D. Milk replacer containing Yes D No
antibiotics
E. Calf starter without antibiotics Yes El No

 

Yes D No D

F. Calf starter containing antibiotics

 

 

 

 

 

G. Other (Specify) Yes [:1 No [:l

" “Treated cows” refers to cows that have been given antibiotics and are still within the milk
withholding period. (A cow given Naxcel/Excenel is not considered a “treated cow” here).

 

 

Answer question #23 only if D. or F. is YES,

 

 

 

23. List the types of antibiotics used below. If unknown, ask to look at tag of bag/container.
Include only antibiotics here.

 

24. How often is maternity housing used as a hospital area for sick’ cows? (Circle appropriate
letter A-C)

A. More than once a month
B. Less than once a month
C. Never
" “Sick” as used here refers to cattle designated as sick by personnel on your farm or by a veterinarian.

Include all i11nes_ses that would result in cattle being segregated (e.g., placed in sick pen) and/or treated
with systemic antibiotics. This would include, but is not limited to lameness, respiratory disorders, and

diarrhea.

 

103

25.

26.

27.

28.

29.

30.

After removal from the dam, at what age do heifers first have direct contact with adult cows in
the herd? months

 

Which of the following best represents your normal practice regarding the cleaning of calf milk
buckets or containers between feedings? (Circle the appropriate letter A-C)

A.

B.

C.

Between each feeding, all calf milk buckets or containers washed with water only.

 

Between each feeding, > List disinfectant
all calf milk buckets

or containers washed and disinfected .

Buckets or containers not washed or disinfected between feedings on a routine basis.

Are preweaned (milk-fed) calves fed milk or calf starter on an
individual basis (e.g., individual bucket in hutch or individual calf pen, D
as opposed to group feeding where a corrunon trough is used)? D Yes No

Are individual calf pens or hutches washed and/or disinfected on a regular basis? (Circle the
appropriate letter A-D.)

A. Washed with water only. —> __times per year
B Washed and disinfected. —’ __times per year —> List disinfectant
C. Not washed or disinfected.
D Calf pen or hutch is not used.
3;)“, often are individual hutches moved to a new location? (Choose the appropriate letter A-
A. Every time a calf is weaned. (Before introducing each new calf.)
B. Not after every weaning, but on a regular basis —’ times per year
C. Calf hutches are not relocated.
D. Calf hutches are not used.

Do personnel on your farm use any of the following precautionary practices when handling
calves? (Check all that apply)

 

When finished with all D0 (“”1
After handling calves (e.g., before {routine y _use
each calf entering a different 11‘s 13:31::
area of the farm) w en n mg
calves

 

A.

Wash boots or use boot dip

 

 

B.

Wash hands after handling
calf or use disposable gloves

 

 

 

 

104

 

31. Is unpasteurized milk that is produced on this operation consumed by family members, farm
workers, or others?

A. Unpasteurized milk from this operation is consumed.
B. Home pasteurizer is used for milk produced on this operation.

C. Unpasteurized milk is not consumed. All milk consumed is purchased.

G. Production and Health

32. During the last six months, which of the following best describes the average bulk tank
somatic cell count for milk shipped? (Circle the appropriate letter A-F below)

A. <100,000 D. 300,000-399,000
B. 100,000—199,000 E. 400,000-499,000
C. 200,000—299,000 F. 500,000+

33. During the last six months, which of the following best describes the average bacterial count
(aka: standard plate count, plate loop count) for milk shipped? (Circle the appropriate letter
A-E)
Colony forming units per millimeter (cfu/ml)
A. 0-24,999 D. 75,000-99,999
B. 25,000-49,999 E. 100,000+

C. 50,000-74,999

105

34.

Do you use DHIA or other computerized records? Yes D No D

 

35.

 

 

 

 

 

 

 

 

 

If YES, answer #35
If NO. go to #36
What is your current rolling herd average for
milk production? ........................................................ Annual

 

36.

37.

38.

39.

What is your average pounds of milk produced per day? (This question is to be asked for
purposes of approximating a rolling herd average if one is not available by DHIA or other
records. Thus, try to get an average pounds per day for as long a time as possible—not just
over the past few days) ............................................... Daily

 

Are sick“ cattle placed in a pen or facility separate from lactating

cows? .......................................................................... Yes D No D

“Sick" as used here refers to cattle designated as sick by personnel on your farm or by a
veterinarian. Include all illnesses tlLat would result in cattle being segregated ( e. 2., placed in sick
pen), and/or treated with systemic antibiotics. This would include, but is not limited to lameness,
respiratory disorders, and diarrhea.

Within the past two years, have any of your dairy cattle been positively diagnosed (i.e.,
by evidence of positive fecal culture or other laboratory test) with any of the following
diseases? (Circle all that apply)

A. Salmonella
B. Johne’s disease
C. Bovine Viral Diarrhea (BVD)

D. No cattle have been diagnosed with any of the diseases above.

Do you normally vaccinate cows with any of the following vaccines? (Circle all that
apply)

A. 15 (Enviracor by Upjohn or J. Vac J5 by Rhone Merieux)
B. Endovac Bovi

C_ Salmonella bacterin vaccine _> Please specify which one, (e.g., Colorado Serum

Companies S. duinn/Sryphimurium bacterin)

 

106

40.

Within the last 60 days, how many dairy cattle within the following groups had diarrhea or
died?

 

Number of animals with Enligbmasitngaelidxljith Number of total
diarrhea lasting at least diarrhgea lastin at least animals that have
24 hours? g died

24 hours

 

Preweaned calves

 

Weaned heifers

 

 

 

 

 

 

 

 

Milk cows
(milking or dry)
41. Are any of the following methods of rodent control routinely used on this operation?
(Circle all letters A-D that apply.)
A. Chemicals/bait?
B Traps?
C. Cats?
D Other methods? (specify)
H. Manure Management
42. Do you use any of the following to remove manure from cow housing areas? (Circle all
letters A-E that apply)
A. Gutter cleaner
B Tractor (bucket loader or skid steer)
C. Hand fork or shovel
D Alley scraper--mechanical
E. Alley flushed with water ——> If so, is the water recycled? D Yes D No
F. Other (specify)

 

107

43.

44.

45.

46.

Are any of the following waste storage systems used on this operation? (Circle all letters A-K

that apply)
A. Below floor or deep pit B. Anaerobic lagoon with cover
C. Slurry storage in earth-basin D. Anaerobic lagoon without cover

E. Slurry storage in Slurrystore® F. Aerated lagoon
(or similar storage structure)

G. Manure pack (inside barn) H. Outside storage within dry lot or pens

1. Outside storage for solid manure not in dry lot or pen
1. Storage of solid manure in a building without cattle access

K. Other storage system used or no storage system used (specify)

 

You may respond to this question in miles or feet. What is the distance between the manure

storage area and the nearest:
A. Well? ...................................................................................................

B. Waterway or body of water? ...............................................................

miles or

miles or

Which of the following methods are used to dispose of manure on owned or rented land?

(Circle all letters A-E that apply)

A. Irrigation B. Slurry (surface application)

C. Broadcast/solid spreader D. Slurry (subsurface application)

B. Other method (specify)

 

F. Do not apply manure on owned or rented land.

In this question, the term “roughage” means hay, fresh chop forage, or
pasture that dairy animals may eat or graze. Do cows eat or graze on
roughage obtained from fields where manure in solid or liquid form
was applied to the surface but not plowed under during the same

growing season? ......................................................... D Yes

How many days do you wait after applying manure to a field before co
allowed to eat or graze the roughage from that field? days

108

DNO

feet

feet

 

 

If YES,
answer #47

 

 

IS are

48. Do you use a loader bucket on a tractor or skid steer to move feed? D Yes D No
l L_

 

 

 

i If YES, answer #49 If NO, go to
Section I

 

 

 

 

 

 

49. Do you use separate loader buckets for moving feed and for handling
manure? (Circle the appropriate letter A-C) ...............

A. Yes, use separate buckets.
B. No, do not use separate buckets.

C. Do not use this equipment for handling manure.

 

If B. is circled, answer #50

 

 

 

50. Afier you have used the loader bucket for handling manure, do you do
any of the following before using it for feed?: (Circle the appropriate
letter A-D)?
A. Rinse bucket with water only.

Power wash bucket with high pressure water.

 

 

 

B
C. Wash and disinfect bucket. > LiSt disinfectant
D

Do not wash or disinfect bucket

I. Antimicrobial Use

51. Which of the following best describes the use of dry cow tubes (intramarrunary infusions)
used to treat your cows at final milk out? (Circle one of the following letters A-C)

A. Dry treat all 4 quarters on all or almost all the cows
B. Dry treat selected cows only, 1 or more quarters

C. Do not dry treat any cows

109

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

52. Does this operation routinely record antibiotic treatment for the following groups of cattle
in some way?
If YES, what types of records are kept?
(Check all that apply)
. . Barn sheet,
$31222: treatment Conrputer log, or Calendar ftherify)
, - , ' notebook 3"“
A.
Lactating D Yes D No
cows
B. Non-
lactating E] Yes D No
cows
C. Calves
and Cl C]
heifers “=5 N0
53. Where do you get recommendations on the following aspects of antibiotic use? (Check all
that apply)
Product label-
Manufacturer 0 l
. . Pharmaceutical Personal label only— Other '
Veterinarian . . Please
Representative Experience not labels farmers cify
from your spe
veterinarian
Recomrneded
use i.e., what
drugs to use
for certain
diseases)
Dosage
Withdrawal
Time

 

 

 

 

 

 

 

 

110

 

 

54.

55.

56.

57.

When you treat respiratory disease in adult cows with antibiotics, what antibiotics do you
normally use? (Circle all that apply)

A. Naxcel/Excenel (ceftiofur)

B Tetracyclines (e.g., Liquamycin--LA-200)
C. Penicillin
D Ampicillin (e.g., Polyfiex)
E. Albon (sulfadimethoxine)

F. Others (please specify)

 

When you treat respiratory disease in calves and heifers with antibiotics, what antibiotics
do you normally use? (Circle all that apply)

A. Naxcel/Excenel (ceftiofur)
B Nuflor (florfenicol)
C. Penicillin
D

Tetracyclines (e.g., Liquamycin--LA-200, Oxy-Tet-IOO )

F“

Ampicillin (e.g., Polyflex)
F. Micotil (tilmicosin)

G. Others (please specify)

 

When you treat calf scours with systemic antibiotics, what antibiotics do you normally use
(oral or injectable)? (Circle all that apply)

A. Panmycin boluses (tetracycline) B. Spectam (spectinomycin)
C. Nuflor (florfenicol) D. Trimethoprim—Sulfa

E. Others (please specify)

 

F. Do not use systemic antibiotics for calf scours.
When you treat mastitis with systemic (oral or injectable) antibiotics, what antibiotics do
you normally use? Do not include intrarnammary antibiotics. (Circle all that apply)

A. Polyflex (ampicillin) B. Amoxi-Inject (amoxicillin)

C. Penicillin D. Erythromycin (e.g., Gallimycin)

E. Others (please specify)

 

F. Do not use systemic antibiotics for mastitis.

111

58. When you treat metritis or retained placenta (RP) with systemic (oral or injectable)
antibiotics, what antibiotics do you normally use? (Circle all that apply)

A. Naxcel/Excenel
B. Penicillin
C. Ampicillin (e.g., Polyflex)

D. Others (please specify)

 

E. Do not use systemic antibiotics for metritis/retained placenta.

59. When you treat foot problems in adult cows with systemic antibiotics (oral or injectable),
what antibiotics do you normally use Do not include topical treatments such as in foot
wraps. (Circle all that apply)

 

A. Ampicillin (e.g., Polyflex) B. Penicillin
C. Albon (sulfadimethoxine) D. Naxcel/Excenel (ceftiofur)
E. Tetracyclines F. Ampicillin (Polyflex)

(e.g., Liquamycin--LA-200)

G. Others (please specify)

 

H. Do not use systemic antibiotics for foot problems.

60. Do you routinely use antibiotics in footbaths to control D
Yes D

or treat lameness? ...................................................... No

A. If YES, do you use the antibiotics in footbaths on a continuous
basis (i.e., all year long)? ................................................................... D Yes [:I No

B. Please list what antibiotics are used, if any:

 

 

61. Do you routinely use any medications in feed or water in weaned
calves or heifers (other than coccidiostats)? ............. YD NE

A. If YES, do you use the additives on a continuous basis? ................... D Yes D No

B. Please list what feed or water additives are used, if any:

 

 

112

62. Approximately what percent of the following groups of cattle have received at least one
antibiotic injection (or oral dose of antibiotics) within the past two months? Include
treatments given by personnel on your farm or by your veterinarian. Do not include
intramamrnary or topical administration of antibiotics. (Make only one check per column)

 

Heifer calves (weaned or

Milk cows (rrulking or dry) Bred heifers pr eweaned)

 

0%

 

1-10%

 

11-25 %

 

26-50 %

 

51-75 %

 

76-100 %

 

 

 

 

 

 

63. Within the past two months, approximately how much of the following antibiotics have
you used? Fill in only one column per row in the table below.

 

Approximate number of bottles used, Approximate
including bottle size (put “0” if do not use number of doses*, if
or if used less than one bottle in past two less than one bottle
months) was used.

 

Penicillin-type

Includes penicillin,
amoxicillin (Amoxi-inject),
anrpicillin (Polyflex)

bottles of size ml or g doses

 

Cephalosporin-type
Includes cefiiofur (Naxcel, bottles of size ml or g doses

Excenel)

 

Tetracycline-type
(includes LA-200, Oxy-Tet- bottles of size ml or g doses
100)

 

Sulfonamides
Includes sulfadimethoxine bottles of size ml or g doses
(Albon)

 

Florfenicol

(NuFlor) bottles of srze____ml or g doses

 

Other antibiotics

Includes tilmicosin
(Micotil), Erythromycin
(Gallimycin), and any others
not covered in the groups
above.

bottles of size ml or g doses

 

 

 

 

 

* A “dose” here means one administration of antibiotic. E.g., if you give 20 ml of Naxcel to a
cow, that is one dose. If you give another 20 ml the next day to the same cow, that is another
dose.

113

Glossary of Terms

The terms listed below are defined according to how they are meant to be used in this survey.

Calving Interval: the time from one calving to the next calving
Colostrum: The first milk produced after a calf is born

Heifer: Non-lactating weaned female animal that has not yet calved,

 

Inorganic bedding includes any inorganic materials such as sand, rubber tires or mats, mattresses,
crushed limestone, etc.

Isolated/Isolation: A newly acquired animal(s) is held for a period of time in a separate pen or other
facility where nose-to-nose contact with cattle in the existing herd is prevented

Maternity housing refers to where cows normally calve.

Organic bedding includes any organic materials used for bedding, such as straw, wood products such
as sawdust or newspaper, corn cobs or stalks, excluding dried manure.

Physical Contact: means nose-to-nose contact or sniffmg/touching/licking each other, including
through a fence

Sick as used here refers to cattle designated as sick by personnel on your farm or by a veterinarian.
Include all illnesses that would result in cattle being segregated, and/or treated with systemic
antibiotics. This would include, but is not limited to lameness, respiratory disorders, and diarrhea.

Treated cows means cows that have been given antibiotics.

Youngstock: means all animals that are past weaning age and will not be kept as replacements (e.g.,
steers and heifers raised for beef)

 

' As of date of survey completion, number of milking cows in first lactation
2 As of date of survey completion, number of milking cows, lactation 2 & up
3 As of date of survey completion, total number of milking cows (lactation l and up)

4As of date of survey completion, number of dry cows finished with first lactation, but before start of
second lactation

5 As of date of survey completion, number of dry cows, lactation 2 & up.

6 As of date of survey completion, total number of dry cows (lactation 1 & up)

7 As of date of survey completion, total cows (milking and dry, lactation l & up)
8 As of date of survey completion, number of preweaned (milk-fed) heifer calves

9 As of date of survey completion, number of weaned replacement calves and heifers

114

 

'0 As of date of survey completion, number of “other youngstock”

” As of date of survey completion, number of bulls kept for breeding purposes

'2 As of date of survey conrpletion, total number of dairy cattle present on operation
'3 Number of total milk cows (milking and dry) born and raised on this operation

'4 Number of total milk cows (milking and dry) born here but raised elsewhere.

'5 Number of total milk cows (milking and dry) not born on this operation

'6 Total number of total milk cows (milking and dry) (should agree with #7 above)

'7 Beef cattle present on operation l=yes, 2%0

115

Herd Visit Questionnaire

Risk Factors for Salmonella and Campylobacter Infections and Drug Resistance in
Dairy Cattle

This short questionnaire is to be given every two months (at each sampling visit) in
order to capture management and inventory changes that may have occurred since the
initial questionnaire was given.

 

 

 

IMPORTANT: Note that on questions 4 and 5, the questionnaire administrator
should pencil in answers from the last administration of the questionnaire and
note any changes between previous answers and what is being fed today. Ask
questions in the format “Are you still feeding blood meal to high-producing
cows?” for feeds that were previously fed. For feeds that weren’t fed in the past,
make sure they are not now feeding them, such as by asking “Are you feeding any
blood meal to any cows now?” and, if so, ask further which groups are being fed
blood meal.

 

 

Date:

 

Study ID
number:

 

Person to whom herd visit questionnaire is
administered

Herd visit questionnaire
administrator

Date of next
visit

116

A

 

1. As of today, what is your inventory of the following groups of dairy cattle?

 

Total

 

A. Total cows (milking and dry)

 

B. Preweaned (milk—fed) heifer calves

 

C. Weaned replacement calves and heifers“

 

 

 

 

" “Weaned replacement calves and heifers" here means all female animals that will be kept as replacement cows, have
not yet calved. and are no longer receiving milk or milk replacer as part of the diet.

2. Were any of the following groups of animals brought onto this operation from outside
sources during the last 60 days?

 

Brought onto IF YES.

operation? HOW many were
brought onto

1 = YES 2 = NO operation?

 

A. Preweaned (milk- 4 5
fed) calves? [:1 Yes [:i No

B. Weaned dairy 5 7
calves or heifers? D Yes D No

 

 

 

 

 

 

 

 

C. Dairy cows? 8 9
D Yes [:1 No

D. Bulls? 10 11
D Yes [:1 No

B. Other cattle, 12 13
including beef? D Yes E] No

14

E. Total.

 

 

 

 

’ “Isolated” here means that the animal(s) is held for a period of time in a separate pen or other facility where nose-to-
nose contact with cattle in the existing herd is prevented.

117

3. Within the last 60 days, how many dairy cattle within the
following groups had diarrhea or died?

 

 

 

 

 

Podinq Number of animals with Number of deaths. Number of total
”mom”: 1 = diarrhea lasting at least among ammals wuh animals that have
checked; 2 = 24 h 9 diarrhea lasting at d' (1

"am (““5- least 24 hours ‘6

Preweaned 15 16 17

calves

Weaned 18 19 20

heifers

Milk cows 21 22 23

(milking or

(‘0’)

 

 

 

 

 

4. Have the ration ingredients for milking and dry cows changed since the last time our
questionnaire was given? Compare answers from the previous questionnaire with what is
now being fed and note any changes in the table below. Include only purchased feeds or
feeds obtained from off-farm sources. (Check all that apply).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

. . Other
Type of Feed High-Producing Milking Dry
Cows“ * Cows
Cows
A. Whole cottonseed/hulls 24 25 26
B. Cottonseed meal 27 28 29
C. Whole soybeans or soybean meal 30 31 32
D. Bakery by-products 33 34 35
E. Brewers by-products (includes distillers’ grains) 35 37 33
F. Blood meal 39 40 41
G. Meat & bone meal (e.g., porcine-only or 42 43 44
equine-only)
G. Milk products (e.g., whey) 45 45 47
H. Tallow/animal fat 43 49 50
1. Other protein meal (e.g., meal from fish or 52 53 54
poultry)
Please specify 51
" lf high-producing cows are not fed differently from other milking cows, put MA in the “Other Milking Cows"
column.

118

5. Have the types of milk or calf starter fed to preweaned calves changed since the last time
our questionnaire was given? Compare answers from the previous questionnaire with what
is now being fed and note any changes in the table below. Include only calves that are
kept up to weaning, after they have received colostrum.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Included in diet? Answer
1
A. Whole milk from untreated“ cows 55 D Y E] N 22:11}?
es ° if c, D,
B. Whole milk from treated“ cows (waste 55 [:1 D E, or F.
milk) Yes No is YES
C. Milk replacer without antibiotics 57 D
Yes D No —
D. Milk replacer containing antibiotics 58 _
D Yes [:1 No
E. Calf starter without antibiotics 59 D Yes D No .—
F. Calf starter containing antibiotics 50 D D
Yes No '
62
G. Other (specify) 61 D Yes E] No
‘ “Treated cows" refers to cows that have been given antibiotics and are still within the milk
withholding period. (A cow given Naxcel/Excenel is not considered 3 “treated cow” here).
6. List the types of antibiotics used and the brand names of the milk replacer or calf 5 er
below. If unknown, ask to look at tag of bag/container.
Antibiotics used, if any
63
Brand name of milk
replacer 54
Brand name of calf
starter 65

 

119

7.

Within the past 60 days, have you used any medications
in feed or water in weaned calves or heifers (other than
coccidiostats)? ........................................................... 66 ........................... Yes El No D

A. IF YES, Please list the feed or water medications used. Include brand name of additive,
medication name, and duration of use:

 

67
8. Within the past 60 days, have you used any
medications in feed or water in adult cows? .................... 68 D Yes [:i No
A.If YES, Please list the feed or water medications used. Include brand name of additive,
medication name, and duration of use:
69

 

120

9. Within the past 60 days, approximately how much of the following antibiotics have you
used? Fill in only one column per row in the table below.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Approximate number of bottles used, including bottle size (put A roximate
“0" if do not use or if used less than one bottle in past two pp
number of
months) .
doses“, if less
# bottles size of bottle units (ml or g) 31:35:;bottle
(# ml or g) coding: (1 = ml; 2 = g) '
Pencillin 94 95 96 97_doses
Amoxicillin 98 99 100 101—doses
(e.g.,
Penicill Amoxi-
in-type inject)
Ampicillin 102 103 104 105—doses
(e.g.,
Polyflex)
Cephalosporin-type
Includes ceftiofur 106 107 108 109___doses
(Naxcel, Excenel)
Tetracycline-type
(includes LA-ZOO, Oxy- 110 111 112 113—doses
Tet-100)
S
u Albon or other 114___ 115____ 116___ 117___doses
l sulfas
f
o
n
' Trimcthoprim-sulfa
1' type (e.g.,
3m Tribrissen, SMZ- 118 119 120 121_doses
' TMP, Primor)
d
e
s
Florfenicol (NuFlor) 122__ 123____ 124____ 125_doses
Tilmicosin (M icotil) 126 127 128 129 doses
LS-SO
(Spectinomycin/Lincom 130 131 132 133 doses
ycin soluble powder)
Other antibiotics(e.g., Spectam, Gentocin, Erythromycin, etc. Please specify)

 

‘ A “dose" here means one administration of antibiotic. e.g.. if you give 20 ml of Naxcel to a cow, that is one dose. if
you give another 20 ml the next day to the same cow. that is another dose

121

 

 

The terms listed below are defined according to how they are meant to be used in this survey.

Dose: as used here means one administration of antibiotic. e.g., if you give 20 ml of Naxcel to a cow,
that is one dose. If you give another 20 ml the next day to the same cow, that is another dose.

Heifer: Non—lactating weaned female animal that has not yet calved,

Isolated/Isolation: A newly acquired animal(s) is held for a period of time in a separate pen or other
facility where nose-to-nose contact with cattle in the existing herd is prevented

Medications: as used here refers specifically to antibiotics—it does not refer to probiotics,
anthelmintics and other non-antibiotic medications.

Physical Contact: means nose-to-nose contact or sniffing/touching/licking each other, including
through a fence

Preweaned calves: as used here means calves that are still receiving milk or milk replacer.

Treated cows: means cows that have been given antibiotics and are still within the milk withholding
period. (A cow given Naxcel/Excenel is not considered a “treated cow” here).

Weaned: refers to animals that are no longer receiving milk or milk replacer.

Weaned replgement calves and heifers: here means all female animals that will be kept as replacement
cows, have not yet calved, and are no longer receiving milk or milk replacer as part of the diet

122

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