Table Of Contenti. Tii2 ::is?ciat;:clcgy op cgltagicus pcar.iriA n; a:TVV”!
iX. TIuj rliOPAGATICi; OP Tax, PYIOLCGICAI AGLi.'T (VIRUS)
n; 22m chicj: mimYC
by
Tsu-ling Chov/
A Phesis
Submitted to the School of Graduate Studies of
Hi chican State College of Agriculture and
Applied Science in partial fulfillment
of the recuirementc for the decree
of
DOCTOR CP PHILOSOPHY
Department of Animal ratholony
1950
TABLE CF CCLTEIJTS
-
ACI-lKC./LSDCrEISI'T
xlv TRCDUC TI Gil 1
ETIOLOGY AL2) ..AYLCGELESIS 4
REVIEW OP LITER AT LiRE 8
I LIT ER IAL .ALL LET.-.'CDS 26
RESULTS 05
AISTCLATACLOGY ;E6
liscussioi; 49
su: EARY 67
JLLUSTEATIGi.S 6S
BIBLICGEAIL'CY 109
She writer who was sent to the United States to
pursue graduate study under the cooperation of Lichican
State College and the Agriculture Association of China
•fishes to express his gratitude and appreciation for this
benefit, lie is deeply indebted to Dr. Prank Thorp, Jr.,
'major professor, for his impressing guidance and persistent
encouragement. Dr. Thorp fires tne writer’s imagination
as he conveys his critical ability. Also the writer wants
to display his gratitude and thankfulness to Dr. A. A.
Hartnells, Head of t.-.c Department of Animal _athology, and
Dr. C. A. Uoppert, professor of biochemistry for their
critical reading of the thesis. The writer feels that it
was his privilege tc have years of association with hr.
m. 1. Gray who has taken much interest in -this. Investigation.
Finally, the writer sincerely thanks ail the friends in
the department.of Animal Pathology 'for their friendliness
•throughout all the years of his stay at Mchigan State College
I ITT RC DU C TI Cl?
Contagious ecthyma is a specific viral disease of
the shin of sheep. Primarily the stratified epithelium
of the shin is attacked by the virus which results in pro
liferative and vesicular formations. Secondarily, the
lesion is invaded by pyogenic bacteria causing pustular
formation and tissue necrosis.
The disease-has been reported in almost all parts
of the world, Annain, India, East Indies, Peru, U. S. A.,
Australia, Hungary, Yugoslavia, Holland, Belgium, 'Jest
Africa, South Africa, liorocco, Germany, Italy, Greece,
Erance, England and Scotland.
This disease is commonly jmown as sore mouth or
contagious ecthyma of sheep. Classically it is termed
"dermatitis vesiculoso-pustulosa necroticans ovium".
Synonyms such as necrobncillosis, impetigo labialie,
malignant aphtha, orf, lip-and-leg ulceration, 3cabby mouth,
acute facial dermatitis, contagious sore lips, pustular
stomatitis and ensootic necrosis of the sheep do not
exactly express the correct idea of the viral vesicular
formation and the specific location of the lesions on
the body. ITecrobacillosis, for example, implies bacterial
infection with necrotic formation which differs fundamental
ly from viral sore raouth disease. Impetigo labialis re
fers to the localised form of pustular formation on the
labia, however, it in no.way indicates the viral origin.
The designation malignant aphtha may be confused with foot-
and-moutli disease. Aphtha is characterized "by an eczema
like lesion, but sore mouth is of the vwriola-vaceina type.
Orf is a good term, tut unfortunately was not used in the
United States, lip-and-leg ulceration is not appropriate
because sore mouth disease does not present an ulcerative
formation unless secondary infection takes place. Scabby
mouth is too general a term there being other causes for
scabby mouth. Bcthyma is primarily a pustular eruption,
while thi3 disease is principally characterized by a
vesicle formation usually followed by secondary invaders.
i
It would be better to apply! the term "contagious vesiculo-
pustular dermatitis" to this disease.
The disease was first noted in the latter part of
the nineteenth century, although its previous existence
night be assumed. Zeller (1920) first investigated the
possibility of a virus etiology. This was verified by
Aynaud in 1921 who concluded it was due' to a filtrable
virus. About the same time in Greece, Blanc et al (1922)
studied a similar condition which affected goats. They
teiieved that the same viru 3 affected both the sheep and
the goats. This disease vm s less widespread during the
summer months. Animals of all ages were susceptible.
Since the disease v/as so widely distributed throughout
the sheep growing areas of the world mid animals of all
ages were affected, the con lition was deemed worthy of
study’’.
The study’- of the hisfcopathological changes in sheep
infected "by this virus constitutes the first part of
this investigation, and the attempts to propagate the
virus and to produce the lesions in the chick embryo
composes the second part.
ETIOLOGY A17D PATHCGEHESIS
The primary infective agent of this disease is a
filtrable virus which is present in the lesions only,
particularly the vesicular contents and the scabs. This
virus has a relatively large size, and is filtrable
through Berfefeld filter V and Chamberland L. Handler
filters give inconsistent results. The viral agent does
not pas.: through Berhefeld 17 and Chamberland Lg filters.
Therefore, the disease can not always be produced success
fully by artificial inoculation with these filtrates.
The virus is rather resistant to desiccation. It retains
infectiveness for about two years in a dry sto.te. Infected
pastures contain the etiological material for two to three
months or longer, although no definite period has been
determined. The virus is easily hilled by common chemical
disinfectants, however it is attenuated slowly by ether
of chloroform.
The disease belongs to variola-vaccinia group but
is not identical to them as was proved by Aynaud (1925),
Glover (195.10 and Bennett e_t al (1944). Artificial in
fection in sheep and goats of all ages could be produced
by emulsified crust material. Inoculation could be per
formed by scarifying or puncturing the shin.
An important accessory factor in the etiology is
the portal of entry of the virus. It can be the wounds
or abrasions of the shin which occur commonly during
grazing. Other factors which can lower the resistance
of the tissues such as exposure to dampness, exhausting
journey, insufficient food and lambs suckling the ewes.
Soft skin devoid of viool or hair is the most favor
able location for the viral esion. The lesions after
healing leave no scar or any sign of the disease provided
there are no deep erosions formed. Complications, in
volving the tongue, omasum, reticulum, intestines, liver
or lungs due tc secondary invaders, have been reported
(Newsom and Cross, 1951). The evident lesions were ne
crosis and ulcers. Transmission to man under natural con
ditions had been reported (Hatzioles, 1950; Branderburgh,
1952; ITev/som and Cross, 1954), however it rarely occurred.
Eorses, calves, dogs, and monkeys have been mentioned as
susceptible (Hutyra, et al, 1949). nevertheless, Howarth
(1929) stated conclusively that cattle, pigs, dogs and
rabbits were not susceptible.
The primary macroscopic lesions develop after an
incubation period which wries from one to four days. The
lesions always occur on the non-wooly area of the skin.
In general, three types can be distinguished according to
the location of the lesions, namely, labial type, padolic
type, and genital type. The labial type is the most common
one. The lesions are confined to the lips and the com
missure of the mouth, but they quite often occurron the
nose. The symptoms begin with a circumscribed red spot
termed a macule. It continues to swell and increases in
height and becomes a papule. Soon the papule becomes
vesicular in nature. Meanwhile the secondary bacterial
invaders gain entrance into the lesion and change the vesicle
into a pustule. This secondary infection hastens the pro
gress of the stages to such a degree that sometimes the
vesicular stage is so short and insignificant that it is
often not observed, particularly under natural conditions.
Moreover, it is not uncommon to find ulcers which tend
to coalesce. The pustule, either ruptures or remains in
tact and dries gradually, so that a crust is formed on
top of the pustule. The whole period, from macule to scab,
lasts from one to two weeks. The scab loosens in two to
three weeks. If the whole flock is affected, the disease
persists for about four to six weeks. The morbidity of
the lambs in the flock may be as high as 95f>. Death does
not ensue unless secondary infection sets in. The labial
type is usually benign in form. If severe secondary in
fection takes place under conditions of poor management,
the lesions may spread over both lips and not frequently
may spread to the non-woolly parts of the head such as the
eyelids and ears. Suckling lambs often iniect the teats
of the ewes during nursing.
The padolic type occurs less frequently than the
labial type. The favorite location of such lesions is
the coronet. Due to the anatomical location, it always
results in erosions and ulcers with extensive suppura
tion and lameness. The genital type is rare. It is
characterized, in the female, by painful swelling of the
labia sometimes with development of ulcers. It often in
volves the under surface of the tail, adjacent skin, udder
and teats. In the male, the prepuce is primarily affected
v/ith reddening and swelling. The lesions also develop
into ulcers which may coalesce to form a large suppurat
ing area, sometimes involving the entire prepuce. The
progress of the lesion does not depend necessarily upon
the time element because a two-day old lesion of one sheep
did not show less advanced changes than the three-day
lesion of another sheep. The seriousness of the infection
v/as mainly contingent up on the manner of management
and the resistance of the host.
