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PERIVASCUIAR AND NEUROGLIAL REACTIONS IN MAINS FROM
NEUROINICALLY ASYMPTOMATIC CHICKENS

By

JOHN HENRY GREVE

AN ABSTRACT

Submitted to the College of Veterinary Medicine
Michigan State University of.Agricu1ture and
Applied Science in partiel.fhlfillment of

the requirements for the degree of

MASTER OF SCIENCE

Department of Veterinary Pathology

1959

Approved by [2 QMWZZ/

John Henry Grave

ABSTRACT

Brains were collected from diseased but neurologically asymptomatic
chickens submitted to the Michigan State University avian necrOpsy
laboratory. Using hematoxylin and eosin technique, neuroglial prolifer-
ations and/or perivascular cuffings with lymphoid cells were seen in
h8.8% of the cerebral hemispheres, h6.l% of the mesencephalon halves,
30.1% of the medulla-pontes, and 35.3% of the cerebellums. Chickens 5
weeks old.and younger were usually free of lesions, whereas chickens 7
‘weeks old and older often had lesions. The general incidence of lesions
in asymptomatic chickens was comparable to that reported by other workers.

The perivascular cuffs were usually intramural, being contained by
a connective tissue membrane peripherally. The lymphoid cells of the
cuffs were pleomorphic, perhaps demonstrating morphological changes due
to aging of the lesions. Small nodules of'microglia were the most
common neuroglial abnormalities. The perivascular cuffs tended to be
concentrated near the ventricles, but the neuroglial nodules had a more
haphazard distribution. Endothelial hypertrophy was commonly seen.

Some possible causes of perivascular cuffs in asymptomatic poultry
may include: subclinical Newcastle disease, avian leukosis complex,
response to specific infectious agents primarily affecting other systems,
a previous attack of encephalitis, or a reaction to avian encephalonyelit-
is vaccination. That these vessels are a normal site of lymphocytopoiesis

was considered a remote possibility.

PERIVASCULAR AND NEUROGLIAL REACTIONS IN RUINS FRO!

NEUROLWI CALLY ASYI‘U’TOMATIC CHICKENS

JOHN HENRY GREVE

A THESIS

Suhnitted to the College of Veterinary Medicine
Michigan State University of Agriculture and
Applied Science in partial fulfillment of

the requirements for the degree of

MASTER OF SCIENCE
Department of Veterinary Pathology
1959

ACKNWIEIBEMEN TS

The author is gratefully indebted to the following people for
their guidance in this study:

To Dr. C. C. Merrill, Head, Department of Veterinary Pathology,
for his suggestions and guidance;

To Dr. R. F. Langham, Department of Veterinary Patholog, and
Dr. T. W. Jenkins, Department of Anatomy, for their
suggestions;

To Dr. E. M. Smith, Department of Anatomy, for her suggestions
and for the occasional use of her laboratory facilities;

And to his wife, Sally, for her patience, understanding, and
assistance in the preparation of this manuscript.

I.

III.

IV.

V.

CONTENTS

INTRODUCTION . . . . . . . . . .

LITERATURE REVIEW . . . . . . .

A. Newcastle disease . . . . .

B. Asian encephalomyelitis . .

C. Neural lymphomatosis

D. Pathogenesis of
PROCEDmRE . . . . .
RESULTS . . . . . .
A. lesions . . . .
B. Distribution .

0. Age incidence .

O O 0

lesions . .

DISCUSSION . . . . . . .

SUMMARY AND CONCLUSIONS

REFERENCES CITED . . . .

CD mm 13' N N H

10

10

13
25
30
32

I. INTRODUCTION

Much about the experimental pathology of Newcastle disease (NCD),
avian encephalomyelitis (AE), and avian leukosis complex.(ALC) has
been recorded in the literature. The ubiquity and infectivity of these
viruses make them constant companions to other disease agents in the
field. To what extent these viral diseases play a role in the pathogene-
sis of other natural disease outbreaks, and to what extent these and
other viral agents produce lesions in the brains of "normal" field
specimens is not well understood.

The objectives of this research were: (a) to obtain a better
understanding of the fundamental disease processes involved in the
encephalitides of poultry, (b) to discover the incidence of vascular
and neuroglial lesions in neurologically asymptomatic poultry, and (c)

to evaluate the severity of such lesions.

II. LITmATURE KEVIN
A. Newcastle disease

Jungherr (17, 21) and Pappenheimer gt 9.1.. (25) found microscOpic
lesions indistinguishable from neural lymphomatosis in the central
nervous system of asymptomatic chickens. Isolated perivascular cuffs and
minor neuroglial foci were coumon in these birds. In most instances
these ”nonspecific changes" were so designated because of their sparseness
and the lack of concomitant encephalitic symptoms (21). Jones found
lesions indistinguishable from avian encephalomyelitis in healthy poultry
(16). little attention was given to the location of lesions within the
gross divisions of the brain. Since the publishing of these reports sev-
eral years ago, poultry husbandry methods have changed, the genetic back-
ground of poultry has changed, and the disease-complement of the poultry
environment has changed.

Newcastle disease was first observed by Doyle (10) in 1926 in
Newcastle-on-Tyne, England. Doyle differentiated this condition frm
fowl plague. Respiratory and paralytic symptoms were the clinical mani-
festations of this outbreak.

Since 1926 Newcastle disease has become world-wide. In the United
States it was first diagnosed by Beach as "pnemnoencephalitis" in l9h2
(2). Jungherr and Minard (20) described the condition as it occurred in
the U. S.

The histopathology of emerimental NCD was studied by Jungherr and
Minard (20). Lesions seen in the brain were considered more characteris-
tic of this disease than those seen in the viscera. They included, in
ascending order of occurrence, capillary huorrhages, myelin degenera-
tion, localised meningitis, endothelial proliferation, neuronal degenera-

tion, and neuroglial foci, often the macroglial types. DeKock (8)
characterised the vascular changes as swollen endothelial cells, which
may slough into the vascular lumen, and as infiltration by lymphocytes,
monocytes, and other cells into the vessel wall. In a few cases, a few
of these cells were found free in the perivascular spaces. Schuermann
(29) described the vascular lesions as perivascular cuffs accompanied by
endothelial and adventitial proliferations. According to Jungherr _e_t_ g.
(21), recent lesions sometimes had only a thickening and proliferation
of the vascular endothelium along with early neuronal degeneration.

Glial clumps were a character of older lesions. Karzon and Bang (22)
demonstrated that neuronal degeneration and perivascular cuffs occurred
simultaneously after a 3 to 1: day incubation period. Foci of predilection
were lumbar cord, medulla, and the cerebellar nuclei (21), while Jungherr
and Minard (20) noted the thalamus as an important site in addition to
those mentioned.

Auer (1) studied loci of predilection. He noticed two main syndromal
classifications of Newcastle disease: somnolent and excitable. Micro-
scopically, both groups had widespread engorgement of vessels and lympho-
cytic infiltrations. In the excitable type, the hypothalamus had only
a few foci of lymphocytes and the midbrain and hindbrain had neuronal
degeneration and lymphocytic foci, especially in the postural mechanisms.
In the somnolent type, widespread lymphocytic infiltration without any
neuronal degeneration was seen. The excitable type may progress to the
somnolent type.

Sullivan (32) studied more thoroughly the involvement of the postural
mechanism (cerebellum, reticular nucleus, and vestibular nuclei). Out-

standing lesions were hyperemia of the medulla and cerebellum, endothelial

proliferation and neuronal degeneration (especially in the Purkinje cells,
cerebellar nuclei, vestibular nuclei, and reticular nuclei).

The attenuated, En strain of'Newcastle disease virus, first describ-
ed by Hitchner and Johnson (12), is used widely in the prephylaxis of
NCD. Bernstein and Bang (6), working with this strain, noticed that the
virus did not extend beyond the turbinates in.most birds when inoculated
intranasally. In a few (10%), the virus was recovered from the lower
respiratory tract. No symptoms were noted.at any time. Extensive infil-
trations of lymphocytes into the lamina propria of the nasal.mucosa were
present. A degeneration of the ciliated epithelium.also occurred.

Sinha gt 5;. (31) also failed to produce symptoms with the B1 strain,
even when this virus was injected.intracerebrally. The hemoencephalic
barrier could not be crossed by 81 when visceral involvementnwas attained.
Karson.and.Bang (22), however, did produce occasional perivascular cuffs
and glial foci homolaterally to the inoculation.site in the brain.

Permanent carriers of Newcastle disease virus are not common (3),
but partially immune flocks may act as "healthy carriers" of this virus
for several months (h).

B. AEEEEDEncephalogyglitis

Epidemic tremor, first described by Jones (15), has been renamed avian
encephalomyelitis after the suggestions of VanRoekel 22.3}. (33). Jones
(15, 16) and Jungherr (l9) feund that the lesions seen.in AE are micro-
scopic rather than gross. Summed.up, these are a neural and.perivascu1ar
lymphocytic infiltration of capillaries, veins, and.meningeal vessels; a
reactive perivascular astrocytosis; and an intervascular neuroglial prolif-
eration. Neuronal degeneration and destruction and neuroglial prolifera-

tion (astrocytes, oligodendroglia, and occasional.microglia) are prominent

in the anterior horn of the spinal cord and throughout the brain. Accord-
ing to Peckham (26), these lesions may still be observed in the central
nervous system approximately 3 months after the original outbreak.

Jungherr (19) found in his series that the cerebrum had lesions in
31.7% of the cases of AE, and the midbrain, cerebellum, and medulla were
each involved in about 22%. Jones (16) noted that the more severe reactions
were seen in emerimentally inoculated chickens. Peckham (26) and Bridges
and Flowers (5) noted a positive correlation between the appearance of
cataracts and a previous diagnosis of AB in a chicken flock. The inci-
dence of cataract was as high as 35% of the flock.

Jungherr and Hinard (20) offer some criteria for the differentiation
of Newcastle disease from AE lustopathologically. limiting the compar-
ison to the central nervous system, some of the differences are as
follows: localized meningitis occurs in NOD, but not in AE; there are
more numerous neuroglial foci in NOD than AE; and a more marked endothel-
iosis is seen in NOD than in AB. These criteria were based on the eXper-
imentally induced disease.

C. M lymphomatosis

Pappenheimsr gt 21. (25) described the lesions of neural lymphoma-
tosis. They gave credit to Marek for the first description of this con-
dition. Grossly, no changes in the brain nor meninges were observed, but
enlargement of the dorsal root ganglia and peripheral nerves with a
slight yellowish discoloration was characteristic in birds showing paresis
or paralysis.

MicroscOpically, the most severe lesions were in the nerve trunks and
ganglia; namely, an infiltration by small and large mononuclear cells

(lymphoblasts, lymphocytes, and plasma cells) between nerve fibers,

secondary degenerative changes, and edema. A massive lymphoid infil-
tration sometimes replaced the nervous tissue. Barely were all bundles
affected, and the infiltration usually was not uniform throughout the
nerve. In the spinal cord, the lesions were similar to those in the
peripheral nervous system, with the addition of ”sub-miliary nodules”,
which consisted of wandering lymphoid cells and neuroglia, in the
vicinity of small blood vessels in the grey and white matter. In the
brain, lesions were present in the cerebrum, cerebellum, thalamus, and
pens. The lesions were focal, not massive as in the cord, and peripheral
nerves. Tito types were identified: (1) compact perivascular rings of
small, densely stained lymphoid cells and (2) 'sub-miliary nodules”.
Perivascular infiltration of meningeal vessels was comon.
D. Pathogenesis of lesions in brain

The dynamics of vascular and neuroglial lesions has been studied
by Nichols and Globus (21;), Gone (7), and Globus (11). Cone stated
that acute changes of neuroglial elements were degenerative in the
astrocytes and oligodendroglia, but were proliferative in the microglia.
Large cuffs formed by cells staining with silver were mentioned. Globus
described chronic changes of oligodendroglia as a moderate swelling of
the cytOplasm, of microglia as a rosette (plaque) formation and gitter
cell formation, and of astrocytes as a hyperplasia or sclerosing glioais.

VonEconomo (cited in Nichols and Globus, 2h) visualized the active
role of the adventitial cell in the histogenous production of polyblasts
and plasma cells. The adventitial cell is regarded as a pluripotent,
undifferentiated cell capable of forming, directly or by more devious
routes, the cells associated with perivascular cuffs (23).

Hichels and Globus (2h) , in working with human encephalitis, out-

lined the pathogenesis of perivascular infiltrations of the hematogenous
type. The cells involved were modified forms of lymphocytes and mono-
cytes which emigrated from the vascular lumen. Migrating cells were
recognized by their hour-glass-shaped nucleus. While in the Virchow-
Robin space, these cells gave rise to various forms. The vast majority
of cells were small and medium lymphocytes, but peripherally a zone of
large lymphocytes was present. The cells were pleomorphic and ameboid.
Erythrocytes were almost always present in the cuffs. The authors noted
a tendency for the cuffs to remain for long periods, the cells undergoing
morphological changes. Migrating lymphoid cells were seen in the nervous
tissue forming focal accumulations.

Johnson (11;) , in his work on the avian leukosis complex, thought
the cuffings to be hematogenous. Hemocytoblasts were carried from
the bone marrow to various sites and there produced lymphocytes, erythro-
cytes, or myelocytes, depending on the environment. In the brain,
lymphocytes were produced.

III . PROCEDURE

Brains used for examination were collected at random from diseased
but neurologically asymptomatic chickens at the Michigan State University
avian necropsy laboratory. Chickens were classified as "neurologically
asymptomatic" after a clinical examination revealed no unusual somnolence
that could not be accounted for by another disease process or motor
abnormalities. For comparative purposes, 1; chickens known to be affected
with N01), 21 chickens known to be affected with MS, and 11 chickens known
to be affected with neural lymphomatosis were also collected and examined.
The chickens were Single-Combed White Leghorns, White Rocks, or hybrids.
The period of collection extended from October, 1958, through June, 1959.

Only brains from recently euthanized chickens were used. The
standard mode of euthanasia was a forcible separation of the atlanto-
occipital joint. Some chickens were euthanized by the application of
a Burdiszo emasculatome midway in the neck. A few chickens were euthaniz-
ed with 5 cc. of a concentrated solution of magnesium sulfate injected
into the wing vein. This was to avoid the injury to the cervical sympa-
thetic trunk attendant to the other forms of euthanasia.

The brains, without dura meters, were immersed for at least 20
hours in 10% formalin which was rendered isotonic by sodium acetate.
Transverse sections of the cerebral hemispheres, transverse sections of
the mesencephalons near the level of the oculomotor nerve , and sagittal
sections of the cerebellums, pontes, and medullas were made. The
sections were imbedded in paraffin.

One suitable section 6 microns thick was cut from each block of
tissue and was stained with hematoxylin and eosin (H and E). A complete

microscopic seaming was given each slide. Vascular and neuroglial

lesions recognised by this technique were mapped onto a stereotyped
profile of that part of the brain. Different notations were used for
different types of lesions. The maps were grouped according to age,
expressed in weeks. The age group of 214 weeks and older was termed

.BMt' e

10

IV. RESULTS

A. Lesions

Seventy-two brains had allgfour areas represented, whereas 66
additional brains were lacking one or more areas. Only 26 of the 72
complete brains had no lesions throughout. Fifty-nine (h8.8%) of 121
cerebral hemispheres, hl (h6.l%) of 89 mesencephalon halves, 31 (30.1%)
of 109 medulla-pontes, and h2 (35.5%) of 119 cerebellums had some degree
of neuroglial and/ or lymphoid involvement. No gross abnormalities were
noticed in any brains.

The lesions noted in this study were perivascular ringing or
cuffing with lymphoid cells, endothelial hypertrophy and hyperplasia, and
neuroglial proliferation. The perivascular cuffs were usually recognized
as an admixture of reticulo-endothelial type cells and lymphoid cells,
hereafter described as "mononuclear". Smaller perivascular cuffs were
often nodular, but larger, older lesions were more widespread along the
course of the affected vessel. The mononuclear cells usually were
irregular in outline and had indefinite borders. The moderate amount
of cytoplasm stained a pale, homogeneous pink. Extreme pleomorphism of
the tissue lymphoid elements was comnon. Capillaries and venules were
the primary sites of cuffing, although a few arterioles had cuffs, too.
Subarachnoid accumulations were also occasionally seen. Rarely were
mononuclears noted free in the perivascular spaces of Virchow-Robin; almost
always the mononuclear cells were intramural, part of a proliferating
adventitial layer (Figures 1-1;). Cuffings were loose to compact, and
often were contained by a connective tissue-membrane. Belicate collagen-
ous fibers occasionally twisted about between the mononuclear cells. In

cuffs that were apparently younger, no collagenous fibers were seen, but

the mononuclear cells merely were condensed in layers around the vessel
(Figure 1). Pyknotic nuclei, particles of hemosiderin, and elongated,
dense mononuclear nuclei were seen in aging cuffs. In a few instances
the mononuclear cells were definitely anaplastic. Mitotic figures,
however, were rare (Figure 3). Sometimes anaplastic cells could be
seen throughout the ventricular spaces; possibly a "shower” of leukotic
cells was in the process of metastasizing.

Hypertrophy of the endothelial nuclei occurred sporadically in
most sections. Often it was in conjunction with a perivascular cuff.
Hyperplasia of the endothelium occurred occasionally. Sloughing of
endothelial cells with hypertrophic nuclei was not common, but occurred
in tuperplasia.

Neuroglial nodules were not as numerous as perivascular cuffs.
mall, loose, rosette-like plaques of microglia were the most common
type noticed. Occasionally a ring of neuroglial cells was present
around the edges of perivascular spaces. Nodules resembling the
'sub-miliary' nodules of Pappenheimer 3.13 a}. (25) were also seen (Fig-
ure 5) . A diffuse neuroglial proliferation of the granular layer was
seen in several cerebellum (Figure 6).

Findings that were not evaluated were congestion, distention of the
perivascular spaces, a vascular dilatation wherein the vascular wall
appeared flaccid, and small lenticular defects in occasional perikarya
(Figure 11). Occasional pyknosis of neurons was apparently due to
their state of post-mortem degeneration at the time of fixation. Pyknosis
of the Purkinje cells was more prevalent. in extracellular rarefaction
of the Purkinje layer that resembled edema was seen at the tips of

almst all cerebellar folia. This artifact was apparently due to

differential shrinkages during fixation. Hemorrhages into the ventricles
were considered agonal. Perivascular hemorrhages were common in the
caudal portion of the medulla and were thought to be due to the trauma
of euthanasia.

B. Distribution

The cerebrum.and.mesencephalon tended to be equally involved with
the most lesions, while the medulla was involved the least often and had
the fewest lesions. The cerebellum held an intermediate position in this
regard.

The distribution pattern of’perivascular cuffs was diffuse, but
there was a tendency in the mesencsphalon and cerebrum.fhr the cuffs to
concentrate near the ventricles. In the cerebellum, the periventricular
region was relatively devoid of cuffs. Instead, they oocurred.mainly
in the white matter of the felia, especially in those felia of the anter-
ior half of the cerebellum. The molecular, Purkinje, and granular
layers were affected about equally; In the medulla and.pons, there was
a tendency for the cuffs to be in the region of the vestibular mechanism
of VIII and.rostral to this area.

The cerebrum and.mesencephalon were so evaluated that one half was
compared with the other half. In both parts of the brain it was noticed
that there was some tendency for one half to have more cuffs than the
other. For example, at a given level, one side might have no cuffs while
the other side might have 3 to 5. ‘Whether the larger number of lesions
occurred with greater consistency on the right or left side was not
determined.

The distribution of the neuroglial lesions was more haphazard.and

did not necessarily follow the distribution of the cuffs.

C. 533 incidence

Table I records the frequency of perivascular cuffs in chickens
7 weeks old and older. Asymptomatic chickens 5 weeks old and younger
seldom had lesions, so they are not included. Fifty-six cerebellums,
97 cerebral hemispheres, SO mesencephalon halves, and 52 medulla-pontes
were examined in the young group. In the 7 week and older group, the
percentage of unaffected brains tends to increase as the age increases,
but the percentage of more severely affected brains remains about the
same.

The incidence of neuroglial lesions is similar to that of perivascular
cuffs, except that there were fewer of the neuroglial lesions in the

brains e

TABLE I

INCIDENCE 0F CUFFS IN NEUROLDGICALLY ASYMPTQMATIC CHICKENS

Lesionsuper section

 

 

 

 

 

 

 

 

 

Age Number None 1:?» ’_E-6' :7:I0 11- Up
Weeks Total (1.) (z) (z) (z) (5%) (%)
Cerebral Hemispheres
7 13 23.1 30.8 0 7.7 7.7 30.8
8 22 59.1 27.3 10.0 8.5 h.5 0
9 18 27.8 27.8 5.6 27.8 5.6 5.6
10 17 29.h 29.h 21.2 17.7 0 0
12 h 25.0 50.0 25.0 o 0 0
adult 53 3707 26011 1609 507 308 9J4
‘Hesenceggalon
7 13 15.h 38.5 15.8 15.h 15.h 0
8 20 65.0 25.0 5.0 5.0 o 0
10 13 30.8 30.8 0 23.1 15.h 0
12 h 50.0 50.0 0 0 0 0
adult 53 62.3 19.0 11.3 5.7 1.9 o
Msdulla
7 8 25.0 37.5 0 25.0 12.5 0
8 11 90.9 0 9.1 0 0 0
9 6 50.0 16.7 0 33.3 0 o
10 10 60.0 0 30.0 0 10.0 0
12 2 0 100 0 0 0 0
adult 20 h5.o h5.0 5.0 5.0 0 0
IOErebellum
7 6 16.7 16.7 16.7 0 16.7 33.3
8 12 66.7 8.3 16.7 8.3 0 0
9 8 37.5 37.5 12.5 12.5 0 0
10 9 hh.h 22.2 11.1 0 0 22.2
12 2 100 0 0 0 0 0
adult 25 no.0 28.8 12.0 8.0 8.0 8.0

 

FIGURE 1 An early hypertrophy and.hyperplasia (arrow) of

the adventitial elements of a large capillary.
Cerebrum.

(0.1.525. 9 weeks. m. 1620.)

FIGURE 2

 

A large perivascular cuff near the lateral ventricle.
Various stages of lymphocytOpoiesis are present.
Extravasated erythrocytes (arrows) are present among
the lymphoid cells. Cerebrum.

(0.1.61.1. 7 weeks. m. 1620.)

FIGURE 3

17

-o'_;.
I“
."1
«1‘

.

1‘".

 

A large perivascular cuff containing a mitotic
figure (A). A large capillary courses through
the lesion. Extravasated erythrocytes (B) are
present among the lymphoid cells. Cerebellum.
( 0446111. 7 weeks. 8&3. X620.)

 

-‘

FIGURE 1; A perivascular cuff of small, dense, lymphoid cells
filling the Virchowaflobin space around a venule.
This is apparently an old lesion, with the cells

undergoing morphological changes. Cerebrum.
(0-5987-1. Adult. Ins. x620.)

FIGURE 5

l9

 

Hodular accumulation of microglial cells adjacent
to a capillary. This lesion is similar to the

'sub-miliary' nodule described by Pappenheimer.
Cerebrum.

(04.525. 9 weeks. M. 1620.)

20

     

  

’ . 3:2 t, I." '
"’5. " "."..:o¢.;" " — 3v
fem , :11. "" '

Va.

FIGURE 6 A diffuse infiltration into the granular layer by
small, densely-staining cells, probably microglia.

This figure shows the edge of such a lesion.
Cerebellmn.

(0-5227. 8 weeks. IRE. X620.)

21

 

FIGURE 7 Normal interfoliar pia mater from an adult
chicken. Cerebellum.
(0529h. Adult. H&E. 1620.)

 

FIGURE 8 Normal interfoliar pia mater from a young chicken.
when compared with Figure 7, the pia mater is seen
to be thickened due to a sub-pial accuulation of
cells, possibly microglia. Cerebellum.

(c-hhoo. 5 days. 8&3. 1620.)

22

 

FIGURE 9 TMckening of the epemtma in the roof of the
third ventricle. Hesencephalon.
(04:516. 2'} weeks. me. 1100.)

23

 

FIGURE 10 Detail of the ependymal thickening shown in
Figure 9.
(the. 1620.)

FIGURE 11

2h

 

Mmerous tiny (I x 3 u), lenticular defects in

a perikaryon. They may also be seen extending
down the axon. Medulla.

(c-529h. Adult. 88:3. 1950.)

25

V. DISCUSSION

No chickens were used from the age groups of 13-23 weeks. Although
this gap exists in the continuity of age groupings, the tendency of
neurologically asymptomatic chickens to have lesions in the brain is
still evident. These findings corroborate those of Jungherr (17,21) ,
Pappenheimer gt al_. (25), and Jones (16), who were concerned with healthy
poultry. This thesis is conceer with poultry that had diseases pri-
marily of systems other than the central nervous systan. What possible
effects these disease processes might have had on the vascular and
neuroglial components of the brain is not certain. The fact remains
that the poultry used were clinically classified "neurologically normal".
Brains from chickens like these appear in experimental groups and in
diagnostic tissues. In either case, the incidence of the "normal
lesions“ described herein should be borne in mind. An accurate yard-
stick for the evaluation of 110 may be necessary before a precise
appraisal of these findings is possible.

Since poultry used in this study were asymptomatic, little is
known of the age of the lesions observed. Michele and Globus (214)
describe "morpholOgical changes" in the lymphoid cells of aging perivascu-
lar cuffs. It is probable that the younger lesions in this study were
characterised by the larger, more round cells with moderate amounts of
cyt0p1asm, and that the aging lesions were characterised by compactness,
and by small and sometimes compressed cells with little cytoplasm. The
latter description also resembles the lesions mentioned by Peppenheimer
3‘5 g. in their treatise on ABC.

In comparing the lesions seen in asymptomatic poultry with those
of chickens naturally afflicted with NCD, AF, or neural lymphomatosis,

26

the two groups may be indistinguishable both ‘qualitatively and quanti-
tatively. In general, the same distribution of lesions was evident,
with the cerebrum high and the medulla-pone low in incidence. Some of
the asymptomatic brains had more lesions than any of the symptomatic brains,
but usually the reverse was true. The quantitative values derived from
this study for the asymptomatic brains were comparable to what Jungherr
(18) apparently noticed. Jungherr noted that approximately 38% of the
brains were “positive" and 23% “suspicious” for the lesions of neural
lymphomatosis or avian encephalomyelitis. Advancements in genetic
resistance to disease, improved nutrition, new disease entities, and
other environmental changes have been made since Jungherr and others
reported on the finding of lesions in asyMptomatic chickens. These
environmental changes appear to have had little effect on the incidence
and severity of lymphoid reactions seen in asymptomatic birds, however.

A suitable seasonal distribution was not collected, so little may
be determined in this regard. However, it was noticed that most of the
severely affected brains were from chickens necrOpsied from the last
half of March through to May. However, more chickens were examined
during this period than other periods.

The significance of the tendency for perivascular cuffs to occur
near the ventricles is not clear. The Virchow-Robin spaces do not
communicate with the ventricles in birds (27), so it appears unlikely
that cuffs in Virchow-Robin spaces in this area are due to dissemination
of a process via the ventricles. Perhaps the nutrition is better nearer
the ventricles, supporting more proli ferative growth.

Using the criteria of Michele and Globus (2h) , little evidence was

seen for the hematogenous origin of the mononuclear elements. Rather,

27

an impression of histogenous (adventitial) origin was gained. Lympho-
blasts were seen, apparently giving rise to more mature cells.

Possible causes of perivascular cuffs in brains of asymptomatic

poultry include:

1. Subclinical Newcastle disease or NOD vaccination reaction
Sullivan located a high percentage of lesions in the postural
mechsllism in cases of NCD. This area of the medulla-pone was
also the locus of most of the lesions in asymptomatic poultry.
Antibodies against this disease following vaccination may
alter its course, producing a subclini cal or otherwise atypical
syndrome. The highest seasonal incidence of lesions in these
asymptanatic chickens conpares with that mentioned for NOD --
November through May (3).

2. Early ADC
Brains of known All: cases were found to have primarily perivascu-
lar cuffing and little neuroglial reaction. This relationship
of lesions was also evident in brains of asymptomatic birds.
Some asymptomatic birds had severe, extensive involvement, such
as would suggest A10.

3. Response to specific infectious agents primarily affecting other
systems-

Many agents, such as PPLO, cause lymphoid Imperplasia in other
areas of the body. Perhaps these same agents cross the hemo-
encephalic barrier and stimulate a mononuclear response in the
perivascular spaces.

h. Previous attack of an encephalitis

How long perivascular cuffs remain is not certain, but it has

28

been suggested that they may last for long periods. Peckham
reported the lesions of AE approadmately 3 months after the
infection occurred in a flock. Michele and Globus (21:) reported
the same for poliomyelitis of man.

5. Reaction to AE vaccination

With this vaccination procedure expected to become routine in
the near future, this factor'may'become more important. Using
the wing-web technique, the live AE virus may produce the
typical disease in about 1% of the breeder-age vaccinates (28,
33). Probably numerous other birds will have the lesions
without the symptoms. Jones (16) showed that chickens inoculat-
ed with live AE virus to produce the disease may have brain
lesions without symptoms.

6. Normal site of lymphocytOpoiesis

Perivascular cuffs have been seen in enough asymptomatic
chickens that this must be considered a possibility, although
remote.

Endothelial hypertrophy and ruperplasia were seen comonly in the
asymptomatic brains. Although these lesions are associated with NOD and
AE, other conditions, such as infectious synovitis (13) and a toxicity
due to an unidentified dietary factor (30) have been described as char-
acterized by similar endothelial changes. Undoubtedly other conditions
are also involved. Apparently endothelial hypertrophy and hyperplasia
are responses by that tissue to nonspecific stimuli, and not a response
to a few specific agents.

The interfoliar pia mater was obviously thickened in the cerebellums

of chickens l to 2 weeks old (Figures 7 and 8). The thickening appeared

29

to be due to a condensation of cells, possibly microglia, Just beneath
the pia mater. Since the pia mater is a source of microglia (9), perhaps
these cells were migrating into the nervous tissue from their site of
formation. This condition was not noticeable in cerebellums of older
chickens. Another meningeal thickening which.is normal is a.marked.in~
crease in the thickness of the ependyma in the roof of the third.ventricle
(Figures 9 and 10). The sub-spendymal cells in this thickening are as
‘many as 10 to 12 layers deep. This formation was seen consistently.
Jungherr (17) mentioned.a thickening up to several layers of the ependymal
lining of the lateral ventricles.

30

VI. SUMMARY AND CONCLUSIONS

In this study, h8.8% of the cerebral hemispheres, h6.l% of the
mesencephalon halves, 30.1% of the medulla-pontes, and 35.3% of the
cerebellums of neurologically'asymptomatic chickens had some degree of
perivascular cuffing and/ or neuroglial proliferation. Chickens 5 weeks
old and younger were usually found to be without lesions, whereas
chickens 7 weeks old and older often had lesions. The general incidence
of lesions in asymptomatic chickens was comparable to that encountered
by other workers.

The perivascular cuffs were usually intramural, being contained by
a connective tissue membrane peripherally. Small nodules of microglia
were the most common neuroglial abnormalities. Perivascular cuffs tended
to be concentrated.near the ventricles, but neuroglial nodules had a more
haphazard distribution. Endothelial hypertrOphy was commonly seen.

Possible causes of perivascular cuffs may include: subclinical
Newcastle disease, avian leukosis complex, response to specific infectious
agents primarily affecting other systems, a previous attack of an encephal-
itis, or reaction to AE vaccination. That these vessels are a normal site
of lymphocytepoiesis was considered a remote possibility.

It may be concluded that the values of histopathology used alone as
a diagnostic tool for avian encephalitides are limited when using hema-
toxylin and eosin. The presence of lesions indistinguishable from those
of Newcastle disease, avian encephalomyelitis, or neural lymphomatosis in
brains of asymptomatic chickens necessitates the use of other diagnostic
aids in conjunction with a histopathological examination. Such diagnostic
aids might be serological tests or virus isolation techniques. Without

concomitant encephalitis symptoms, the finding of lesions in the brain

must be considered with care.

31

1.

2.

3.

Is.

5.

9.

10.

13.

32

REFERENCES CITED

Auer, J .3 Functional Localization of lesions in Newcastle Disease.
I. General Survey. Can. J. Comp. Med., 16(1952):277-28h.

Beach, J. R.: Avian Pneumoencephalitis. Proc. U.S. Livest. San.
Assoc., (19h2):203-223.

Beaudette, F. R.: Newcastle Disease. N.J. Agr. Exp. Sta. 0.,
565(195h).

wandly, Coho: in 31331531., HeEe’ and scmma, LeHe’ 11888868 0!
Poultry. 3rd Ed. Iowa State College Press, Amos, 1952.

Bridges, C.H., and Flowers, A.I.: Iridocyclitis and Cataracts
Associated with an Encephalomyelitis in Chickens. J .A.V.H.A. ,
132(1958):79-8h.

Burnstein, T. , and Bang, F.B.: Infection of the Upper Respiratory
Tract of the Chick with a Mild (Vaccine) Strain of Newcastle
Diseage Virus. I and II. Bull. Johns Hopkins Hosp., 102(1958):
127-1 7.

Cone, V1.3 Acute Pathologic Changes in Neuroglia and in Microglia.
Arch. Neurol. Psychiat., 20(1928):3h-68.

DeKock, 6.: Studies on the Histopathology and Pathogenesis of
Newcastle Disease of Fowls in South Africa, with Special Reference
to the Lymphoid Tissue - A Preliminary Report. Under. Vet. Res.,
26(19Sh):599-630.

Daugherty, T.F.: Studies on the Cytogenesis of Microglia and Their
Relation to Cells of the Reticulo-endothelial System. Am. J.
Anat., 7h(19b,h):61-9S.

Doyle, T.H.: A Hitherto Unrecorded Disease of Fowls Due to a Filter-
passing Virus. J. Comp. Path. , h0(1927):1hh-169.

Globus, J .11.: Glia Response in Chronic Vascular Disease of the
Brain. Arch. Neurol. Psychiat” 20(1928):lh-33.

Hitchner, 8.3., and Johnson, E.P.: A Virus of Low Virulence for
Immlizing Fowls against Newcastle Disease (Avian Pneumoencepha-
litis). Vet. Med. , h3(l9h8):525-530.

Hubben, K.: The Pathogenesis of Infectious Synovitis of Chickens, a
Chronological Examination. U. of Penna. Bull. , Vet. Ext. Quart. ,
15M 1959) :77-90.

Johnson, E.P.: The Etiology and Histogenesis of Ieucosis and
Lymphomatosis of Fowls. Va. Agr. Exp. Sta. Tech. 80.11., 56(193h):
1-32.

15.

16.

17.

18.

19.

20.

21.

22.

23.

2h.

25.

26.

27.

28.

29.

30.

33

Jones, E.E.: An Encephalomyelitis in the Chicken. Sci. , 76(1932):
331-332e

Jones, E.E.: Epidemic Trenor, and Encephalomyelitis Affecting Young

Chickens. J. Exp. Med. , 59(193h):78l-798.

Jungherr, E.L.: The Diagnosis of Fowl Paralysis. Storrs Agr. Exp.
Sta. Bull., 200(193h):l-28.

Jungherr, E.L.: The Etiologic and Diagnostic Aspects of the Fowl
Paralysis Problem. J.A.V.M.A., 86(1935):h2h-h32.

Jungherr, E.L.: Pathology of Spontaneous and Experimental Cases of
Epidemic Tremor. Poultry Sci. , 18(1939):h06.

Jungherr, E.L., and Minard, E.L.: The Pathology of Experimental
Pneumoencephalitis. Am. J. Vet. Res., 5(19hh):125-13h.

Jungherr, E.L., Tyzzer, E.E., Brandly, C.A., and Moses, H.E.t The
Comparative Pathology of Fowl Plague and Newcastle Disease. Am.
J. Vet. Res., 7(19h6)3250-2880

Karson, D.F., and Bang, F.B.: The Pathogenesis of Infection with a
Virulent (CG 179) and an Avirulent Strain of Newcastle Disease
Virus. J. Elm. Med. , 93(1951):267-296.

Maxinow, A.A.: Relation of Blood Cells to Connective Tissue and
Endothelium. Plvs. Rev. , h(l92h):533-563.

Michele, N. , and Globus, J .H.: The So-Called Small Round Cell In-
filtrations. Polio-encephalitis and Acute hidemic Encephalitis.
ArChe Paths, h(1927)3692’7310

Pappenheimer, A.M., Dunn, L.C., and Cons, V.C.: A Study of Fowl
Paralysis (Neuro-lymphomatosis Gallinarum) . Storrs Agr. Exp.
Sta. Bull. , 1h3( 1926) :183-310.

Peckham, M.C.: Case Report - Lens Opacities in Fowls Possibly
Associated with Epidemic Tremors. Avian Dis. , 1(1957):2h7-255.

Ranson, 8J1. , and Clark, 8. L.: The Anatomy of the Nervous System.
9th Ed. H.B. Saunders Co. , Philadelphia, 1953.

Schaaf, K., and Lamoreux, W.F.: Control of Avian Bleephalomyelitis
by Vaccination. Am. J. Vet. Res., 16(1955):627-633.

Schuermann, E.: cited in Jungherr, E.L., 313 51., Am. J. Vet. Res.,
7( l9h6) :250—288 .

Simpson, C.F., Pritchard, W.R., and Hams, 11.11.: An Eldotheliosis
in Chickens and Turkeys Caused by an Unidentified Dietary Factor.
J.A.V.H.A. , 13h(1959):h10-h16.

 

v17-

31.

32.

33.

3h

Sinha, S.K., Hanson, R.P., and Brandly, C.A.: Comparisons of the
Tropisms of Six Strains of Newcastle Disease Virus in Chickens
Following Aerosol Infection. J. 1111‘. Dis., 91(1952):276-282.

Sullivan, D.J.: lesions in the Cerebellum and in the Reticular and
Vestibular Centers in Newcastle usease. Am. J. Vet. Res.,

Van Roekel, H., Bullis, K.L., and Clarke, M.K.: Preliminary Report

on Infgctious Avian Encephalomyelitis. J .A.V.M.A. , 930.938):
372-37 0

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