MERCURY TOXICOSIS {N THE PIG

 

“Wash for $th Degree o§ M. S.
MICHIGAN STATE UNIVERSETY

Winiam J. C. Donnelly
1965

THESIS

LIBRARY

Michigan State
Universxty

 

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ABSTRACT
MERCURY TOXICOSIS IN THE PIG

by William J. Co Donnelly

Research was conducted using 12 pigs assigned in pairs to the
following groups: (1) control, (2) 2 mg. mercuric chloride (H3012) per
kilogram ration, (3) 20 mg. HgClz per kilogram ration, (4) 100 mg.-
HgCl2 per kilogram ration, (5) 200 mgo HgCl2 per kilogram ration, and
(6) 2 Gm. HgClz per kilogram ration.

Signs of clinical disturbance deve10ped on the 5th day in both ani~
mals fed the high level of HgClz° One of the pigs fed 200 mg. per kilo-
gram ration had signs of acute illness on day 19 and died. Clinical
signs included anorexia, staggering gait, emaciation, and diarrhea.

None of the remaining pigs became clinically ill.

Gross lesions noted in the clinically affected pigs included a
paleness of the renal cortex, generalized hemorrhages, and a pseudo~
membrane formation in the colon. MacrosCOpic lesions included neuronal
necrosis and vacuolation, necrosis and regeneration of renal parenchymal
tissue, and focal hepatic coagulation necrosis.

Individual susceptibility appeared to be an important factor in
mercuric chloride toxicosis in the pig, since there was little correla-
tion between the amount of mercuric chloride ingestion per unit of body

weight and the degree of toxicosis.

I

MERCURY TOXICOSIS IN THE PIG

By

William J. C. Donnelly

A THESIS

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

MASTER OF SCIENCE

Department of Pathology

1965

ACKNOWLEDGEMENTS

The author is extremely grateful for the generous support of the
W. K. Kellogg Foundation, which sponsored this study at Michigan State
University.

Appreciation is expressed to my academic advisors, Drs. C. K.
Whitehair, K. K. Keahey, and S. D. Sleight, for their suggestions and
guidance in conducting this research and writing the thesis.

The writer wishes to acknowledge his gratitude to the Deparhment
of Pathology, Michigan State University, for the many favors, courtesies,
technical assistance, and financial support in conducting this research
and making my visit to Michigan such a worthdwhile experience.

My sincere thanks go to my wife for her unfailing understanding and
patience during the period of separation.which inevitably accompanied

my studies.

11

TABLE OF CONTENTS
2233

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
REVIEW OF THE LITERATURE . . . . . . . o . . . . . . . . . . . . . 2
MATERIALS AND METHODS . . . . . . ... . . . . . . . . . . . . . . 5
Experimental Animals, Housing, and Care . . . . . . . . . . . 5
RESUETS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
General Observations . . . . . . . . . . . . . . . . . . . . 10
Clinical Signs . . . . . . . . . . . . . . . . . . . . . . . 10
Pathology . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Brain and Spinal Cord . . . . . . . . . . . . . . . . . 11

Kidney . . . . . . . . . . . . . . . . . . . . . . . . . 13

Urinary Bladder: . . . . . . . . . . . . . . . . . . . . 16

Liver . . . . . . . . . . . . . . . . . . . . . . . . . 20

Heart . . . . . . . . . . . . . . . . . . . . . . . . . 21

Colon . . . . . . . . . . . . . . . . . . . . . . . . . 23
Hematology . . . . . . . . . . . . . . . . . . . . . . . . . 26
Changes in Remaining Pigs . . . . . . . . . . . . . . . . . . 29
DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Clinical . . . . . . . . . . . . . . . . . . . . . . . . . . 3O
Pathological . . . . . . . . . . . . . . . . . . . . . . . . 31

LIST OF REFERENCES 0 O O O O O O O O O O O O O O O O 0 0 O O 0 O 0 35

iii

Table

LIST OF TABLES

Identification of pigs assigned to each pair, initial and
final weights and concentration of mercuric chloride
(H8012)inrationoeeeoeoeeseeeoeeeesee

Total amount of mercury consumed to date of necropsy and
organweights atnecrOP‘Ys a s s e e s e s s s s e s s o s

Hemoglobin, hematocrit, and total and absolute and dif-
ferential leukocyte counts of pigs fed mercuric chloride .

iv

Page

27

Figure

10

ll

12

LIST OF FIGURES

Pigs 7 (2 Gm. HgClzlkg. ration) and 10 (control) on day
22. Pig 7 has a retardation of growth and fecal material
adhering to the rear quarters . . . . 0,0 . . . . . . . o .

Thoracic spinal cord from pig 9 on day 19. Neuronal vacuo-
lation and swelling with loss of Nissl's granules. Hema-
toxylin and eosin. x 187.5. . . . . . . . . . . . . . . . .

Cerebrum from pig 7 on day 27. Focal glial proliferation.
Hematoxylin and eosin. x 75 . . . . . . . . . . . . . . . .

Cerebrum from pig 7 on day 27. Detail of glial prolifera-
tion in Figure 3. Hematoxylin and eosin. x 750.. . . . . .

Kidneys, ureters, and urinary bladder from pig 9 on day
19; Dark hemorrhagic bladder and diffuse surface petechia-
tim on kidney. 0 O O O O O O O 0 O O O O O O O O O O O O O

Kidney from pig 9 on day 19. AtrOphic glomeruli, pyknotic
nuclei, and desquamation of cells of the convoluted tubules.
Hemtmlin and eosin. x 187.5. s e s e e a s e s e e e s e

Kidney from pig 9. Degeneration of transitional epithelium
of renal pelvis with margination of nuclear chromatin.

Kidney from pig 7. Atrophic glomeruli, desquamation of
tubular epithelium, and perivascular edema. Hematoxylin
and eOSin. x 75 0‘.“ O O O ’ O 0'. O O O O O O O I O O O O .. O

Kidney from pig 4. Desquamated epithelial cells with pyk-
notic nuclei and proliferating cells with large vesicular

nuclei and prominent nucleoli.

Kidney from pig 7. Necrotic dilated tubules and foci of
lymphocytic infiltration. Hematoxylin and eosin. x 75. . .

Liver from pig 7. Centrolobular coagulation necrosis.
Hemtoxylinandeosinox7500seeeesosseesse

Liver of pig 7. "Bile lake" with adjacent necrotic hepatic
cells and a mild neutrophilic infiltration. Hematoxylin
and eosin. x 187.5. . . . . . . . . . . . . . . . . . . . .

V

12

14

14

15

15

l7

17

18

18

19

22

F1

l3

14

15

16

17

re

Heart and lung from pig 9 on day 19. Subepicardial
hemorrhage with total involvement of the right ventricle. .

Heart from pig 9. Areas of hemorrhage and perivascular
edema. Hematoxylin and eosin. x 75.. . . . . . . . . . . .

Heart from pig 9. Hemorrhage with infiltration of neutro-
phils and lymphocytes. Hematoxylin and eosin. x 750 . . .

Heart from pig 9. Anitschkow myocytes. Hematoxylin and
808 in. x 750. O O O O O O 0 O O O O O O O O O O O O O O O 0

Colon from pig 7. Necrosis and degeneration of mucosa

with leukocytic infiltration and surface debris. Hema-
toxy11n and eOSin. x 187.5. s s s ale 0 e.s s e e"s s e s 0

vi

Page

21
24
24

25

25

INTRODUCTION

The treatment of seed grains by mercurial fungicides has resulted
in the exposure of livestock to a possible source of mercury poisoning.
Animals may fortuitously gain access to the treated grain; or the
farmer, in the interests of economy, may use it for the compounding of
a ration. Naturally occurring episodes of mercurialimm.have been re-
corded in swine following the ingestion of treated grain.

Variability in the biological activity of mercurial compounds is
known to depend not only on their mercury content but also on their
‘molecular structure (Hughes, 1957, and Garner, 1961). Nevertheless,
characterization of the clinical and pathologic aberrations produced
by the inclusion of a simple inorganic mercurial compound at varying
concentrations in the ration of swine would provide information hither-
to unavailable in this species.

This project was designed to furnish such information with particu-
lar reference to toxic levels of mercuric chloride and the clinical

signs and pathologic changes induced by this compound in growing swine.

REVIEW OF THE LITERATURE

King (1957), in a brief resume of the history of mercury in chemistry
and medicine, stated that mercury compounds were used as drugs in Greece
by Hippocrates around 400 3.0. Occupational mercury poisoning in man
was described by Jean Fernel in 1557 (Goldwater, 1957). At this time
Paracelsus advocated the use of mercury as a treatment for syphilis, for
which condition it became regarded as a specific remedy; and it continued
in this role as a therapeutic agent until the introduction of the organic
arsenical Salvarsan by Ehrlich in 1912 (Haggard, 1929). Haggard stated,

"Patients with syphilis were dosed with mercury in-
ternally and rubbed with it externally until the
saliva flowed from their mouths in a steady stream,
their teeth were loosened and their health permanently
impaired by mercury poisoning."
Thus, in human medicine the disease entity was early recognised and the
clinical changes documented.

Early reports of toxicosis in domestic animals are rare. Oasis,
presumably as a result of ingestion, have been reported in dogs (Green
_£.gl,, 1938) and cats (Gorton, 1924). Two reports of poisoning in
cattle subseduent to the application-of mercurial ointment to the skin
illustrate the susceptibility of ruminants to the toxic action of the
element. Stevens (1938) recorded a case of dermal necrosis in a calf.
A.young bull was also poisoned after licking the mercurial ointment which
had been applied to the back of the calf. Petrelius (1953) experimen-
tally demonstrated the susceptibility of the bovine and ovine species to

inhalation of mercury vapor generated after the application of ointments

to the skin of the horse.

3

McNew (1959) traced the development of mercurial compounds as fungi-
cidal cereal seed dressings. Corrosive sublimate'was used in the late
18th century for this purpose, and this was later supplanted by organic
mercurial compounds. McNew attributed the development of these prepara-
tions to Riehms in 1913 following Ehrlich's success with organic arseni-
cals. Within 3 years, organic mercurials were introduced into the United
States, and as much as 512,000 pounds of mercury equivalent went into
this use each year.

Edwards (1942), in England, reported the death of a 9~year-old horse
following ingestion of grain treated with mercury. Boleylg£_gl, (1941)
and Herberg (1954) reported cases in feeder calves and dairy cattle,
respectively, in the United States. Sonoda 33,31, (1956), in Japan,
investigated the clinical manifestations in 29 cattle fed treated seed
grain, and the pathologic changes in these animals were documented by
Fujimoto 25.31, (1956). Experimental work on the pharmacologic action
of an organic mercurial in 6amonth-old calves was described by Oliver
and Platonow (1960). PaLmer (1963) reported the toxicity of the same
compound (ethyl mercury petoluene sulfonanilide) for sheep and chickens.

Toxicosis was first reported in swine by Taylor (1947), who described
sickness and death of a saw and 8 shoots following feeding of seed grain
treated with a fungicidal mercurial preparation containing 1% ethyl
mercury phosphate. One ounce of the preparation was added to each
bushel of corn, and 1.5 gallons of this treated corn was added to 3.5
gallons of untreated corn to comprise the daily ration. The ration was
fed for about 2 months before the onset of signs. Signs of toxicosis
were observed over a period of almost 3 weeks. These included anorexia,

weakness, paralysis, convulsions, blindness, and loss of condition.

4
There were no gross pathologic changes. There was an "appreciable"
quantity" of mercury in the liver. Kernkamp (1963), in referring to the
work of Ferris w£,g;. (1949), described a controlled study in pigs fed
undiluted treated grain. The pigs fed the treated grain for over 20
days had signs of illness and died after an additional 5 to 10 days.
When pigs were fed the treated grain for only 10 days, no disorders
developed and they reached market weight. In a case report, McEntee
(1950) described the clinical signs and microsc0pic lesions associated
with mercurial poisoning in 2 droves of swine after prolonged feeding
with seed oats treated with a mercurial fungicide. Signs included
inappetance, vomiting, paralysis, blindness, locomotor disturbance,
and a possible glossOpharyngeal paralysis. Characteristic gross
lesions were not described. HistOpathologically, there was coagulation
necrosis of epithelial cells lining the convoluted tubules of the kidney
and neuronal degeneration in the brain.

In summary, toxicoses arising from the absorption of mercury occur
inya number of species. Those publications which described mercurialism
in swine pertained, in general, to naturally occurring episodes and pro-

vided only limited information on toxic levels and on the clinical signs

and pathologic lesions.

MATERIALS AND METHODS

Experimental Animals, Housing, and Care

One litter of 12 Yorkshire-Hampshire crossbred 4dweek-old pigs was
purchased from a local swine farm, and each pig was placed in an indi-
vidual galvanized metabolism cage. Twelve days of acclimatization
elapsed before commencement of the experimental regimen. Observation
of the piglets during this period revealed no clinical abnormalities.

Each piglet was identified and the group was divided into 6 pairs
by random numbers according to Goulden (1956). Pigs were fed once-daily
in troughs attached to each cage. Water was given 3g,libitum. ‘Records
were kept of food consumption. Clinical signs of disease were observed
and recorded. The animals were weighed at the beginning of the experi-

ment and weekly thereafter.

Eggigg. The pigs were fed the standard Michigan State University, Animal
Husbandry Department, grower ration. For the period of scclimatisation,
each pig was fed 400 Gm. daily of this feed. Mercuric chloride (H3012)
was added to the ration at the levels indicated (TABLE 1). Pair I (con-
trols) received no mercuric chloride. The concentrations of HgClz ranged
from 2 mg./kg. basic ration in Pair II to 2 Gm./kg. basic ration in

Pair VI. The ration for each animal was increased to 500 Gm. daily on
day 6, with the exception of Pair VI, whose food consumption had de-
creased by this tfme. The ration was again increased to approximately

600 Gm. daily on day 18 and continued at this level until termination

TABLE 1. Identification of pigs assigned to each pair, initial and
final‘weights and concentration of mercuric chloride (“8012)
in ration.

 

Weights Concentration of

 

Pair Pig Initial Final Avg. Daily ch12 (ms. lkg.
No. No. Sex (kg.) (kg.) Gain (Gm.) ration)
5 M1 8.2 24.1 468 control
I
10 F 10.0 25.5 456 control
3 F 10.0 24.5 453 . . 2
II
11 M 11.8 22.7 373 .7 2
l M. 6.8 18.6 600 20 '
III
8 F 9.1 18.6 327 20
6 F 9.5 25.5 500 100
IV
12 M 7.3 18.2 376 100
2 M 8.2 20.9 410 200
9 M 6.8 13.6 358 200’
4 F 8.2 10.9 90 2000
VI

7 F 6.4 7.3 33 2000

7
of the experiment. Pigs were fed the experimental ration for 28 to 34

days and decrepsied on the days indicated (TABLE 2).

Mercury. The mercury was in the form of the inorganic salt, mercuric
chloride (HgClz). The requisite amounts of the salt were measured on
a Mettler balance. Four kilograms of the sa1t~meal mixture for each
pair of experimental animals were prepared at one time. The dry prepara-
tion was mixed at a slow speed for 5 minutes in an electric feed mixer.
At a later date, when 8 kilograms of mixture were prepared, the time of
mixing was increased to 10 minutes.

On day 14 molasses was added to the ration of those pigs in
Pair VI in an attempt to increase palatability. Eight Gaams of HgCl2
were dissolved in 1200 m1. of molasses. One hundred fifty milliliters
of this solution (containing 1 Gm. HgClz) was‘mixed with 500 Gm. of feed,
the final weight of the mixture being 670 Gm. Fresh feed was prepared

as required. Unconsumed food was weighed at 3-day intervals.

Urine Analyses. Urine was examined at weekly intervals during the
course of the experiment and collected aseptically from the urinary
bladder at necropsy. All urine samples were screened for glucose, pro-
tein, and pH using proprietary indicator strips.* Specific gravity was

routinely recorded on all samples.

Blood Analyses. Blood samples were collected from the anterior vena

cava, as described by Carle and Dewhirst (1942), using lmel. syringes

 

*Combistix, Ames Company, Incorporated, Indiana.

 

 

 

 

TABLE 2. Total amount of mercury consumed to date of necropsy and
organ weights at necropsy.
Total HgCl2 Organ Wts.4gt_Necrcmsijm.#§_1_d 7. ‘B. Wt.)
Pig Day of Consumed . Right Left
No. Necropsy (mg.) Liver Kidney Kidney Spleen
5 34 control 727(3)* 62(.26) 68(.28) 55(.23)
10 34 control 761(2.9) 60(.24) 59(.23) 51(.20)
3 32 33.0 459(1.9) 45(.18) 41(.17) 31(.13)
11 30 29.6 459(2.0) 45(;195 41(.18) 26(.11)
1 31 310.8 391(2.1) 40(.22) 34(.13) ‘35(.19)
8 ’ 29 280.0 460(2.5) 42(.23) 38(.20) 226.12)
6 32 1670.0 609 (2.4) 60(.24) 61(.24) 28(.11)
12 29 1440.0 -401(2.2) 42(.23) 43(.24) 15(.08)
2 31 3100.0 425(3.o) 63(.30) 61(.29) 30(.14)
9 19 1530.0 52563.9) 60{.44) 65(.48) 50(.37)
4 30 8270.0 31762.95 686.62) 67(.62) 21(.19)
7 28 6550.0 348(4.8) 40(.55)

35(.48)

8(.11)

 

*( ) =3 2 body wt.

. 9
with 1k-inch, 20~gauge needles. Five milliliters each of clotted and whole
blood were collected. The anticoagulant was potassium ethylene diamino-
tetraacetic acid (EDTA). Smears for total and differential white cell
counts were prepared immediately and stained with Wright's stain as
described by Benjamin (1964). The cyanmethemoglobin method was used for
the estimation of hemoglobin (Benjmmin, 1964).

Serum samples collected on days 1, 21, and terminally were examined
for blood urea nitrogen (BUN) levels using a modification of the direct
chemical method of Friedman (1953) as recommended by the manufacturers
of the reagents used.*

A bilirubin estimation‘was carried out on the serum collected from
pig number 4 using a spectrophotometric method (Giordano-Pestrud, Modi-

fied) as described by Levinson and MacFate (1961).

_flecropsy Procedure. With the exception of pig 9, which died on day 19,
all the experimental animals were electrocuted and necrOpsies performed.
Prior to death the animals were weighed and terminal blood samples and
rectal temperatures taken. The liver, spleen, and both kidneys were
removed and weighed. Tissue sections were prepared from the following:
Cerebrum, cerebellum, medulla oblongata, thoracic and lumbar spinal cord,
liver, kidneys, spleen, heart muscle, salivary gland, urinary bladder,
skin, duodenum, jejunum, ileum, and colon. Skeletal muscle, lymph nodes,
— and stomach were taken from selected cases. The tissues were placed in
10% neutral formalin for fixation? .Sections were cut at 5 microns and
stained with Harris' hematoxylin and eosin. All histopathologic methods

used are described in the Manual of Histologic and Special Staining

Technics of the Armed Forces Institute of Pathology, Washington, D.C. (1957).

 

*Hycel, Incorporated, Texas.

RES ULTS

General Observations

Pig 9 died on day 19 of the experiment, manifesting an acute terminal
syndrome. Pigs 7 and 4 were euthanatized on days 28 and 30, respectively,
having manifested signs commonly associated with chronic disease of en-
teric origin. Definitive clinical signs of disease or gross pathologic
changes were not demonstrable in the other animals. The total amount of
HgClz consumed by each animal throughout the experimental period and
organ weights are given (TABLE 2). An increase in kidney weight is evi- ‘

dent in pig 4.
Clinical Signs

‘Agggg. On day 13, pig 9, having consumed a total of approximately 1.05
Gm. HgClz, had slight but noticeable petechiation of the skin of the base
and outer surface of the ears. There was marked petechiation the follow-
ing day on the skin of the back, shoulders, sides, and medial surface of
the thighs. In some areas these hemorrhages were ecchymotic and purple.
There was a large ecchymotic hemorrhage on the slcera towards the medial
canthus of the right eye, and there were many petechiae on the skin of
the snout. Skin irritation was not manifested. On day 16 the nictitating
membrane of the left eye had protruded and was hemorrhagic. The central
areas of many of the larger petechiae and ecchymoses of the skin were
black and necrotic. On day 18 the pig was reluctant to rise but had no
signs of incoordination. At 7 a.m. on day 19, it was very’weak, and the

10

11
rectal temperature was 103 F. It was found dead at 12:30 p.m. on day 19.

Total HgC12 consumed up to this time was 3.1 Gm.

Chronic. There were signs of chronic toxicosis in both animals (numbers
7 and 4) of Pair VI. On day 5, there was partial anorexia and a slight
diarrhea, and it was estimated that each pig had consumed about 3.5 Gm.
HgClZ. Food consumption was markedly reduced, and there was weakness of
the posterior limbs by day 8. Diarrheic, darkacolored, fetid feces were
passed. Deterioration in condition occurred more rapidly in pig 7. On
day 21, pig 7 had jaundice which persisted until necropsy. ‘Weight gains
in both animals were negligible (TABLE 1). There/was aLmost total inap-
petance in both animals from day 21 until necrOpsy. The addition of
molasses did not increase food consumption. The water intake of pig 7
was reduced. Signs of illness included hind leg weakness, swaying motion
when walking, crossing of the hind legs, and collapse. The hind legs
were drawn forward when standing and during forward progression were
moved stiffly, without free joint action. The only evidence of abdominal
pain was intermittent grinding of the teeth during the last 2 weeks of

the experiment. The hindquarters were stained with fecal material

(Figure 1).

Pathology

The most marked gross and microscOpic changes were in pigs 4, 7,

and 9. These are described in detail.
Brain and Spinal Cord

Gross Lesions.

Pig 9. A large submeningeal hemorrhage obscured the surface of the

12

 

 

Figure l. Pigs 7 (2 Gm. HgClzlkg. ration) and
10 (control) on day 22. Pig 7 has a retardation of
growth and fecal material adhering to the rear quarters.

13
right frontal lobe of the cerebrum. There were many petechiae on the

superficial and cut surfaces of the brain. The spinal cord was normal.

Pigs 4 and 7. The only gross change was congestion of the meningeal

blood vessels.

Histopathologic Examination.

 

Pig 9. Hemorrhage, as reported under gross lesions, was present.
There was no evidence of a breakdown of the extravasated red blood cells.
Edema in the meninges and in the Virchow-Robin spaces was evident." There
was vacuolation, swelling, and loss of Nissl's substance in the neurons
of the gray matter of the thoracic spinal cord (Figure 2). Hemorrhage
and accumulation of macrophages and lymphocytes were adjacent to the

central canal of the thoracic spinal cord.

Pigs 4 and 7. Focal glial proliferations, hemorrhages, and edema
were in the proximity of blood vessels in the cerebrum (Figures 3 and 4).
The meninges were edematous and contained focal petechial hemorrhages.
There was neuronal degeneration in thoracic and lumbar portions of the

spinal cord.
Kidney
Gross Lesions.

Pig 9. The kidneys were pale gray and stippled with a few petechiae
(Figure 5). The pale coloration was localized in the cortex. There was
an area of reddening at the corticomedullary junction. Petechial hemor-
rhages were present throughout the cortex, and there were ecchymotic

hemorrhages in the pelvic area which extended into the medulla.

14

 

Figure 2. Thoracic spinal cord from pig 9 on day
19. Neuronal vacuolation and swelling with loss of
Nissl's granules. Hematoxylin and eosin. x 187.5.

 

Figure 3. Cerebrum from.pig 7 on day 27. Focal
glial proliferation. Hematoxylin and eosin. x 75.

15

iPt.

é.‘
. . “d .
‘. .(
1' ."‘I ‘ .. ‘
,. 1
1 , .,
. v .'
‘ |

. "-y

0" .

o6

’

. .
’

 

Figure 4. Cerebrum from pig 7 on day 27. Detail
of glial proliferation in Figure 3. Hematoxylin and

eosin. x 750.

 

 

 

 

Figure 5. Kidneys, ureters, and urinary bladder
from pig 9 on day 19. Dark hemorrhagic bladder and
diffuse surface petechiation on kidney.

l6

Pigs 4 and 7. The renal cortex was pale.

Histgpathologic Examingtion.

Pig 9. There were hemorrhages and edema in the capsule. Mhny of the
glomeruli were atrophic with pyknotic nuclei and vacuolation of the cyto-
plasm, Some of the epithelial cells lining the convoluted tubules were
pyknotic and some had cloudy swelling. Many of these cells were desqua-
mated into the lumens (Figure 6). There were scattered interstitial
hemorrhages in the cortex and medulla. Margination of the chromatin in
the nuclei of the transitional epithelium lining the pelvis was observed

(Figure 7).

Pigs 4 and 7. Many glomeruli were atrophic. There was cloudy
swelling of many of the epithelial cells lining the convoluted tubules,
with some pyknosis and desquamation of epithelium (Figure 8). Regenera-
tive processes were widespread throughout the tissue.) In these areas
the cellular cytOplasm was more basophilic and the nuclei were large,
vesicular, and contained prominent nucleoli CFigure 9). A few mitotic
figures were seen. There were scattered dilated tubules with flattened
lining epithelium, some containing desquamated cells and albuminous
material (Figure 10). There was an interstitial fibroblastic reaction

and occasional foci of lymphocytes. Perivascular edema was demonstrable.
Urinary Bladder
Gross Lesions.

Pig 9. The organ was dark red and contained approximately 40 m1.

of orange-colored urine (Figure 5). The redness was the result of severe

l7

 

Figure 6. Kidney from.pig 9 on day 19. Atrophic
glomeruli, pyknotic nuclei, and desquamation of cells

of the convoluted tubules. Hematoxylin and eosin. x
187.5.

‘prv

 

 

 

Figure 7. Kidney from pig 9. Degeneration of
transitional epithelium of renal pelvis with margina-
tion of nuclear chromatin. Hematoxylin and eosin.

x 187.5. '

l8

 

Figure 8. Kidney from pig 7. Atrophic glomeruli,
desquamation of tubular epithelium, and perivascular
edema. Hematoxylin and eosin. x 75.

'

 

Figure 9. Kidney from pig 4. Desquamated epi-
thelial cells with pyknotic nuclei and proliferating
. cells with large vesicular nuclei and prominent
nucleoli. Hematoxylin and eosin. x 187.5.

l9

 

Figure 10. Kidney from pig 7. Necrotic dilated
tubules and foci of lymphocytic infiltration. Hema-
toxylin and eosin. x 75.

.L" "
. u

- -. .- - ’.~ ~. ' (
, ‘ - I 7“ '0.
, \ s (O . f at
‘ I ‘4 {* . ; '1' '?'8
- ‘ . .

.D. 3'... ‘o\/é.

 

Figure 11. Liver from pig 7. Centrolobular
coagulation necrosis. Hematoxylin and eosin. x 75.

20
hemorrhage in the muscularis. The mucosal surface had irregular dark red
areas which were most numerous in the fundus and abated towards the
urethral outlet. There was an abrupt change to normal epithelium on the

urethral side of the sphincter.
Pigs 4 and 7. No gross lesions were observed.

Histopathologic Examination.

Pig 9. There was a hemorrhagic infiltration of the urinary bladder
wall from the mucosal to the serosal surfaces. Atrophy and pyknosis of
the smooth mmscle cells were prominent. The atrophy in places was ad-
vanced, leaving areas almost devoid of musculature. finch of the transi-

. tional epithelium‘was desquamated, and the remaining cells were atrophic.

Pigs 4 and 7. There was coagulation necrosis of the transitional

epithelium with pyknosis and loss of cellular integrity.
Liver
Gross Lesigns.

Pig 9. The organ was pale yellow-brown with a well demarcated

lobular structure.

Pigs 4 and 7. The liver of pig 7 was brownish-red and had well
demarcated lobules. The peripheral zone of the hepatic lymph node was

bile stained. Nochanges were observed in pig 4.

Histgpatholggic Examination.

Pig 9. There were focal discrete areas of coagulation necrosis of

21
irregular intralobular distribution, and these were lightly infiltrated
with neutrophils, fibrin, and red blood cells. The remaining hepatic
cells had cloudy swelling and cytoplasmic vacuolations. The degenerative
changes were most pronounced in the centrolobular regions. There was a
slight increase of fibrous connective tissue and edema in the regions of
the portal triads, with moderate increases in numbers of lymphocytes,

neutrophils, and eosinophils.

Pigs 4 and 7. Widespread parenchymal degeneration was demonstrable
in pig 7 (Figure 11). There were irregularly distributed areas of focal
coagulative necrosis similar to that reported in pig 9. In association
with these areas, there were small, irregular "bile lakes" (Obel, 1953)
(Figure 12). There was sinusoidal dilatation and many Kupffer cells
contained pigment similar to hemosiderin. The severity of the centrolobu-
lar necrosis was again a notable feature. In pig 4, in.which there was
no discernible gross change, there was edema of the portal triads, sinusoidal
dilatation, and degeneration of the parenchymal cells. The Kupffer cells

again contained pigment resembling hemosiderin, but they were less affected.
Heart
Gross Lesions.

Pig 9. The cardiac musculature was diffusely affected by hemorrhage.
Ecchymotic hemorrhages extended from the subepicardial and subendocardial
regions deep into the musculature of the left ventricle. The entire

musculature of the right ventricle was hemorrhagic and dark red (Figure

13). There were subepicardial and subendocardial.petechiae of both atria.

22

 

Figure 12. Liver of pig 7. "Bile lake"‘with
adjacent necrotic hepatic cells and a mild neutrOphilic
infiltration. Hematoxylin and eosin. x 187.5

 

 

 

 

Figure 13. Heart and lung from pig 9 on day 19.
Subepicardial hemorrhage with total involvement of the
right ventricle.

23
Pigs 4 and 7. No gross changes were detectable in the muscular
tissue. In pig 7 the fat of the coronary groove was edematous and

appeared similar to serous atrophy.

Histopathologic Examination.

4—

Pig 9. There were many hmnorrhages in the myocardium, which were
often infiltrated with neutrOphils and lymphocytes (Figures 14 and 15).
There was an interstitial and perivascular edema. A wide variation in
the size, shape, and density of the myocardial nuclei was noted.
Anitschkow myocytes were present (Figure 16). Small foci of coagula-
tion necrosis were detectable, and these were often associated with

hemorrhagic areas .

Pigs 4 and 7. Hemorrhage, though present to some degree, was not

a noticeable feature. There were numerous Anitschkow myocytes.
Colon
Gross Lesions.

_Pig 9. There were hemorrhages on the serosal and mucosal surfaces.
No gross mucosal ulceration was detectable. The contents of the organ

were bright yellow and of normal consistency.

Pigs 4 and 7. The mucosal surface was covered by a yellowish-white,
thick, necrotic material which was easily detached. In some areas the
mucosa was speckled with small points of black discoloration. These
may have represented petechial hemorrhages with digestion of the blood.

The contents of the organ were sparse, fluid, and yellow. The terminal

24

 

.Heart from pig 9. Areas of hemorrhage
Hematoxylin and eosin. x 75.

Figure 140

and perivascular edema.

 

Hematoxy-

Hemorrhage with

infiltration of neutrophils and lymphocytes.

lin and eosin. x 750.

Heart from pig 9

Figure 15.

25

 

Figure 16. Heart from pig 9. Anitschkow myo-
cytes. Hematoxylin and eosin. x 750.

 

 

Figure 17. Colon _frm pig 7. Necrosis and
degeneration of mucosa with leukocytic infiltration
and surface debris. Hematoxylin and eosin. x 187.5.

26

24 inches of the mucosal surface of the ileum in pig 4 were also necrotic.
HistOpathologic Eggmination.

Pig 9. There was coagulation necrosis of cells within the crypts
of Lieberkflhn. Individualization, opaque eosinophilic cytOplasm, and
nuclear margination of chromatin were common to these necrotic cells.
There was swelling of the cells at the base of the crypts. Large areas
of hemorrhage dissected the muscular layers and in some locations involved

the submucosa.

Pigs 4 and 7. The "false membrane" covering the mucosal surface
consisted of a thick layer of necrotic debris containing the degenerative
nuclei of many neutrophils and lymphocytes (Figure 17). The necrosis
extended into the submucosa and in many areas obliterated the mmscularis
mucosae. Granulation tissue infiltrated by macrophages and a few other
inflammatory cells represented the reparative process in the area. The
villi in the ileum of pig 4 were necrotic and structurally indiscernible.
Recognizable cells at the base of the crypts were pyknotic. A band of
cellular reaction beneath the necrotic debris was composed mainly of
neutrOphils and lymphocytes. There was congestion of submucosal blood

vessels. .

Hematolggy

The results of hemoglobin, hematocrit, and total and absolute dif-
ferential leukocyte counts are given (TABLE 3). Pig 4 had a neutrophilia
with a shift to the left. Pig 7 had similar changes in the white cell
count and a fall in the hemoglobin content to 8.6 mg./100‘m1. The BUN
level in pig 4 at death was elevated to 200 mg./100 ml. The result of

a total serum bilirubin analysis on pig 7 before death was 6.5 mg./100‘m1.

27

 

 

 

 

 

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2232833 in RemainingiPigg
Changes in the parenchyma of the liver, kidney, and heart were
discernible in 5 other pigs (numbers 1, 8, 6, 12, and 2) fed HgClz.
These same pigs had no clinical signs or gross lesions. The changes
were minimal in the :- pigs in Pairs III and IV. Pig 2, from Pair v,
had cloudy swelling of the renal convoluted tubules, and this was
limited to a comparatively small number of nephrons. The pigs in

Fair II and the control animals in Fair V were normal.

DISCUSSION

Clinical

This research using a highly soluble inorganic mercury salt gave
results suggestive of individual variation in susceptibility to the
toxicosis. Signs developed in pig 9 after a total of 1.58 Gm. HgClz
had been consumed; however, in pig 2, 3.1 Gm. HgClz was consumed with-
out any clinically detectable changes.

Both animals in Pair VI, fed 2 Gm. of HgClz per kilogram basic
ration, gave early indications of toxicosis. The acute fonm of mercury
poisoning, as described by Kernkamp (1964), was not observed. Clinical
disturbance did not appear until experimental day 5, when the estimated
amount of ingested mercuric chloride was 3.5 cm. per pig. Approximately
0.1 Gm./kg. body weight was consumed by these pigs up to this time.
Figures quoted by other authors on the toxicity of organic mercurial
compounds for species other than swine demonstrate that much smaller
amounts of these compounds are required to produce clinical signs and
death (Boley, 3;.gl,, 1941, and Palmer, 1963). Death did not occur in
the pigs in Pair VI of this experiment. Signs of the chronic toxicosis
increased in severity in the 2 pigs as the experiment progressed. The
sudden rise in BUN level in pig 4 on experimental day 30 may have been
an indication of approaching death. A rapid terminal rise in BUN levels
was noted by Oliver and Platonow (1960) in experimentally induced toxi-

cosis in 6-month-old calves. They attributed it to an acute renal failure.

30

31

Clinical variation in the individual response of pigs 4 and 7 was
found. The rise in BUN level in pig 4 has already been mentioned. No
significant change in BUN levels was demonstrable in pig 7. In this
animal, however, jaundice was clinically detectable on experimental
day 21. The serum in blood samples taken from this pig after the
development of clinical jaundice was.yellow. A serum bilirubin estima-
tion was carried out on a blood sample taken immediately prior to
euthanasia. The total serum bilirubin concentration was 6.5 mg./100‘m1.
These clinical indications of extensive hepatic damage were confirmed
histologically.

Taylor (1947) and McEntee (1950) have described naturally occurring
outbreaks in which definite neurologic disturbances were noted. There
‘was some difficulty in assessing the clinical manifestations of incoordi-
nation and staggering gait occurring in the pigs in Group VI of this
experiment, since deterioration in condition produced lassitude and
weakness. No disturbance in vision or convulsions were detectable.

There was no laboratory evidence of kidney damage until the rise
of the BUN level inpig 4 described earlier. Goldwater (1957) has‘
pointed out that there is uncertainty as to whether or not occupational
mercury poisoning in man due to inorganic compounds produces such

laboratory evidence.

Pathological
In the present investigation the 3 pigs (numbers 4, 7, and 9) which
were clinically affected also had grossly demonstrable lesions. There
was evident paleness of the renal cortex in all 3 cases. This was the

only lesion common to all pigs. Hughes (1957) stated that the pathologic

32

effects of mercury on human tissues are the result of real concentrations
of the element in the affected organ. Must analytical data on tissue
concentrations of mercury both in man and the domestic animals indicate
that mercury is found in highest concentration in the kidneys (Boley
35.31,, 1941; Drill, 1958; Fujimotolggflgl., 1956). It is to be expected,
therefore, that these organs would be abnormal in appearance if sufficient
time had elapsed from primary contact with mercury. Glomerular changes
have not been previously reported in the pig. Atrophic changes in the
glomeruli were observed in pigs 4, 7, and 9. The necrosis and regenera-
tion of the tubular epithelium corresponded to that described by
McEntee (1950).

The histologic changes in the brain and spinal cord were shailar
to those described by MbEntee (1950) but also included neuronal vacuola-
tion and focal glial proliferation. Drill (1958) stated that the pro-
longed systemic action from mercuric salts is manifested by damage to
the capillary bed and at sites of excretion. The neuronal damage in the
pigs of this series could thus be due to anoxia. Both Taylor (1947) and
McEntee (1950) reported blindness and paralysis in pigs fed organic
mercurials. Certain organic mercurials, for example the methyl mercury
halides, are 100 times more soluble in lipids than in water (Hughes,
1957), and their action could be attributed to selective deposition in
nervous tissue. It would seem that the comparative lack of definitive
nervous symptoms and lesions in this experiment may be due to the
nature of the compound administered.

Hepatic damage was found in the 3 clinically affected cases in this
series. It was most evident in pig 7, which had a clinical icterus and

gross evidence of liver change. The distribution of the intralobular

33
focal necrosis was difficult to explain. Few normal liver cells were
found. Taylor (1957) stated that mercury was found in appreciable
quantities in the liver in those pigs dying after eating seed grain
treated with 1% ethyl mercury phosphate. Ogilvie (1932) described a
cloudy swelling of the liver in rabbits given HgClz. Fujimoto gt; §_1_.
(1956) also described focal hepatic necrosis in cases of mercury
poisoning in cattle due to "Ceresan", an organovmercuric fungicide.

The necrosis of the mucosa of the colon in pigs 4 and 7 may be
explained on the basis of partial excretion of mercury through the mucosal
surface. Ogilvie (1932), using rabbits, demonstrated that intravenous
as well as oral administration of HgClz resulted in mucosal degeneration
in the colon and postulated that the mercury is partially excreted by
this route.

Drill (1958) indicated that the mercuric ion produced a circulatory
collapse as a result of arrhythmia and ventricular fibrillation.“ The
changes found in cardiac musculature of pig 9 in.this experiment appeared
to be the result of prolonged tissue damage and not acute circulatory

collapse.

SUMMARY

Research was conducted using 12 pigs assigned in pairs to the
following groups: (1) control, (2) 2 mg. mercuric chloride (HgClz)
per kilogram ration, (3) 20 mg. HgC12 per kilogram ration, (4) 100 mg.
HgC12 per kilogram ration, (5) 200 mg. HgClz per kilogram ration, and
(6) 2 Gm. HgClz per kilogram ration.

Signs of clinical disturbance developed on the 5th day in both
animals fed the high level of HgClz. One of the pigs fed 200 mg. per
kilogram.ration had signs of acute illness on day 19 and died. AClinical
signs included anorexia, staggering gait, emaciation, and diarrhea.

None of the remaining pigs became clinically ill.

-Gross lesions noted in the clinically affected pigs included a
paleness of the renal cortex, generalized hemorrhages, and a pseudo-
membrane formation in the colon. Microscopic lesions included neuronal
necrosis and vacuolation, necrosis and regeneration of renal parenchymal
tissue, and focal hepatic coagulation necrosis.

Individual susceptibility appeared to be an important factor in
mercuric chloride toxicosis in the pig, since there was little correla-
tion between the amount of mercuric chloride ingestion per unit of body

weight and the degree of toxicosis.

LIST OF REFERENCES

Armed Forces Institute of Pathology. 1957. Manual of Histologic and
Special Staining Technics. Washington, D.C.

Boley, L. F., Morrill, C. C., and Graham, R. 1941. Evidence of
mercury poisoning in feeder calves. North Am. Vet., 22: 161.

Carle, B. N., and Dewhirst, W. H., Jr. 1942. A method for bleeding
swine. J.A.V.M.A., 101: 495.

Drill, V. A. 1958. Pharmacology in Medicine, 2nd ed. McGraw-Hill
Book Co., Inc., New York: 782.

Edwards, C. M. 1942. Mercurial poisoning in a horse as a result of
eating treated oats. Vet. Rec., 54: 5.

Ferrin, E. F., Kernkamp, H. C. H., Roepke, M. H., and Moore, M. B.
1949. Treated seed grains found fatal to hogs. Minn. Farm and
Home Sci., 6: 7. '

Fijimoto, Y., Ohshima, K., Satch, H., and Ohta, Y. 1956. Pathologi-
cal studies on mercury poisoning in cattle. Jap. J. Vet. Res.,
4: l7.

Garner, R. J. 1961. Veterinary Toxicology, 2nd ed. Williamm and
Wilkins Co., Baltimore, Md.: 103.

Goldwater, L. J. 1957. The toxicology of inorganic mercury. Ann.
N.Y. Acad. Sci., 65: 498.

Gorton, B. 1924. Mercurial poisoning. B. Vet. J., 80: 49.

Goulden, C. H. 1956. Methods of Statistical Analysis, 2nd ed. John
Wiley & Sons, New York. -

Green, D. F., Allison, J. 3., Greenwood, W. R., and Morris, M. L. 1938.
Kidney damage in dogs produced by mercury poisoning. J.A.V.M.A.,
93: 225.

Haggard, H. W. 1929. Devils, Drugs, and Doctors. Harper and Brothers,
London. . ‘ '

Herberg, W. H. 1954. Mercury poisoning in a dairy herd. Vet. Med.,
49: 401.

Kernkamp, H. c. H. .1964. Diseases of Swine. H. W. Dunne (Editor),
Iowa State Univ. Press, Ames, Iowa: 578. .

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36

King, C. V. 1957. Mercury: its scientific history and its role in
physical chemistry and electrochemistry. Ann. N. Y. Acad. Sci.,
65: 360.

MbEntee, K. 1950. Mercurial poisoning in swine. ‘Cornell Vet., 40: 143.

MtNew, G. L. 1959. Landmarks during a century of progress in the use of
chemicals to control plant diseases. From Plant Pathology Problems
and Progress 1908-1958. Univ. of Wisconsin Press, Madison, Wisc.:
42.

Obel, AoL. 1953. Studies on the morphology and etiology of so-called
toxic liver dystrOphy Chepatosis diaetetica) in swine. Acts
Pathologica et Mucrobiologica Scand., Sup. 94.

Ogilvie, R. F. 1932. The pathological changes produced in tissues by
corrosive sublimate. J. Path. Bact., 35: 743.

Oliver, W. T., and Platonow, N. 1960. Studies on the pharmacology of
N-(ethylmercuri)-p-toluenesulfonanilide. Am. J. Vet. Res., 21:
906. '

Palmer, J. S. 1963. Mercurial fungicidal seed protectant toxic for
sheep and chickens. J.A.V.M.A., 142: 1385.

Petrelius, T. 1953. Poisoning of ruminants through the inhalation of
mercury vapour from horses treated with mercury oinmment. Proc.
15th Int. Vet. Congr., Pt. I: 506.

Sonoda, M., Nakamura, K., Too, K., Matsuhashi, A., Ishimoto, H., Sasaki,
K., Ishida, K., and Takahashi, M; 1956. Clinical studies on
mercurial poisoning in cattle. Jap. J. Vet. Res., 4: 5.

Stevens, G. G. 1938. Mercurial poisoning. Cornell Vet., 28: 50.

Taylor, E. L. 1947. Mercury poisoning in.swine. J.A.V.M.A., 111: 46:

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