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Outline of Exotic Diseases
OIE List A Diseases
OIE List B Diseases
Exotic Agents not on OIE Lists
Course Introduction
Overview 1
(Modes
of introduction of
exotic animal disease agents)
Overview 2
(Role
of international, national & state agencies in
controlling outbreaks and appropriate responses to suspected outbreaks.
Overview 3
(Description
of recent incursions
of exotic diseases)
Scenarios of Outbreaks
Rift Valley
Fever
Equine Respiratory Diseases
(African Horse Sickness, Hendra, EIA)
Rabbit Haemorrhagic Diseases
Equine Neurologic Syndrome
Mexico Cattle Abortion
Zoo Module
Bioterrorism/Agroterrorism
Reptile ticks/Heartwater
Poultry/Pet Birds
Rinderpest/Salmonella/BVD/Haemorrhagic Septicemia
Fish Diseases
Ticks
Feline Spongiform Encephalopalitis
Ruminant Neurologic Diseases
Screwworm
Vesicular Diseases of Swine
Acute Swine Diseases
Related Links |
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Importance Sheep and goat pox are contagious viral
skin diseases. These diseases may be mild in indigenous breeds
from endemic areas, but are often fatal in newly introduced
animals. Pox infections can limit trade, export, and the
development of intensive livestock production. They may also
prevent new breeds of sheep or goats from being imported into
endemic areas. |
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| Etiologic
agent |
| Sheep pox and goat pox result
from infection by members of the Capripox genus in the family
Poxviridae. Most isolates cause disease mainly in sheep or mainly
in goats; some isolates can cause serious disease in both species.
The causative viruses cannot be distinguished from each other with
current techniques. Only one serotype exists. |
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| Species |
| Sheep and goat pox viruses cause
disease only in these two species. Infections have not been seen
in wild ungulates. |
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| Geographic
distribution |
| Sheep pox and goat pox are found
in central and north Africa, central Asia, the Middle East, and
parts of the Indian subcontinent. A mild goat pox-like disease has
been reported in California but is unlikely to be a capripoxvirus. |
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| Clinical
signs |
The first sign of infection is a
fever, followed 2 to 5 days later by erythematous macules that
develop into 0.5 to 1.5 cm hard papules. The centers of the
papules are initially edematous but become depressed, gray, and
necrotic, surrounded by an area of hyperemia. Fluid-filled
vesicles have been seen over the lesions but are rare. Dark, hard,
sharply demarcated scabs eventually form and may take up to six
weeks to heal. Skin lesions may be restricted to the axilla,
perineum, and groin or may cover the body. In animals with heavy
wool, the lesions can be easier to find by palpation than visual
inspection. Mild infections can easily be missed; only a few
lesions may be present, often around the ears or the tail.
Systemic signs may include conjunctivitis, rhinitis,
lymphadenopathy, depression, and a variable degree of blepharitis.
Anorexia is sometimes present if the mucous membranes are
involved. Lung lesions can cause dyspnea. The mucous membranes may
become necrotic and animals may develop a mucopurulent nasal or
ocular discharge. Secondary bacterial infections are common and
death can occur at any stage of the disease. Some European breeds
of sheep die before the characteristic skin lesions appear. |
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| Morbidity
and mortality |
Morbidity and mortality vary
with the breed of the host and the strain of the virus. Disease is
usually more severe in young animals. Mild infections are common
in indigenous breeds; however, symptoms may be more severe in kids
or lambs, stressed animals, animals that have concurrent
infections, or animals from areas where pox has not occurred for
some time. Imported breeds of sheep and goats usually develop
severe disease when they are moved into an endemic area. Mortality
may be up to 50% in a fully susceptible flock and as high as 100%
in young animals.
Infection results in good immunity. Vaccines are available in some
areas. |
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| Modes
of transmission |
Sheep and goat pox viruses are
usually transmitted by the respiratory route, but may also enter
the body through abraded skin. Most animals become infected while
they are in close contact with infected sheep or goats. Infectious
virus is found in all secretions, excretions, and the scabs from
skin lesions. Contagious aerosols may also be generated from dust
that contains pox scabs. These viruses can be spread on fomites
and are probably transmitted mechanically by insects. Chronically
infected carriers are not seen.
Sheep and goat pox viruses can remain infectious for up to six
months in sheep pens. These viruses may also be found on the wool
or hair for as long as three months after infection. |
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| Incubation
period |
| The incubation period is 8 to 13
days in most natural infections, but may be as short as 4 days. |
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| Post
mortem lesions |
| The skin usually contains
macules and papules, with areas of edema, hemorrhage, congestion,
necrosis, and vasculitis. The papules penetrate through both the
dermis and epidermis; in severe cases, they may extend into the
musculature. The lungs often contain discrete congested or
edematous lesions or hard white nodules. Papules or ulcerated
papules are common on the abomasal mucosa. They may also be found
on the rumen, large intestine, trachea, esophagus, tongue, and
hard or soft palate. Pale foci are sometimes present on the
surface of the kidney, liver, and testicles. The lymph nodes are
usually swollen and the mucous membranes may be necrotic. |
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| Public
health aspects |
| Sheep and goat pox viruses do
not appear to infect humans. |
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| Diagnosis |
Clinical
: Sheep or goat pox should
be suspected in animals with the characteristic full-thickness
skin lesions, fever, and lymphadenitis. Dyspnea may also be seen.
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Differential
Diagnosis :
The differential diagnosis
includes contagious ecthyma (contagious pustular dermatitis),
bluetongue, mycotic dermatitis, sheep scab, mange,
photosensitization, peste des petits ruminants, parasitic
pneumonia, and caseous lymphadenitis.
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Laboratory
Tests: Sheep or goat pox can
be tentatively diagnosed by electron microscopy; the morphology of
the virus particle is characteristic. The causative viruses can be
isolated in lamb testis or kidney cell cultures or in other sheep,
goat, or bovine cell lines. Identification is by immunofluorescence
or immunoperoxidase staining.
An agar gel immunodiffusion (AGID) test or enzyme-linked
immunosorbent assay (ELISA) can detect virus antigens.
Cross-reactions occur in the AGID test with parapoxvirus. A
polymerase chain reaction (PCR) technique has also been reported.
Antibodies can be found a week after the skin lesions appear.
Serologic tests include virus neutralization, agar gel
immunodiffusion, indirect immunofluorescence, ELISA, and
immunoblotting (Western blotting). Virus neutralization is the most
specific serological test, but is not sensitive enough to detect
infections in all animals. Cross-reactions with other viruses are
seen in the AGID and indirect immunofluorescence tests.
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Samples
to collect: Skin biopsies
should be taken for virus isolation and antigen detection. In live
animals, virus can also be isolated from blood samples or lymph
nodes. Samples taken at necropsy should include the skin, lymph
nodes and lung lesions. Neutralizing antibodies can interfere with
virus isolation or antigen-detection ELISAs; samples for these tests
must be collected during the early stages of infection. Blood
samples must be sent to the laboratory within two days and, ideally,
as soon as possible. They should be shipped on wet ice or gel packs.
Tissues for virus isolation, antigen detection, or PCR should be
kept at 4° C or -20° C. Glycerol (10%) can be added to tissue
samples that must be shipped long distances without refrigeration;
these samples must be large enough that the medium does not
penetrate into the center of the tissue.
Serum should be collected for serology. Samples for histology should
include skin (with a wide range of lesions) from live animals and a
full set of tissues at necropsy. Lesions from the skin, rumen,
lungs, and trachea are particularly useful.
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| Recommended
actions if this disease is suspected: |
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Notification of authorities
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Sheep or goat pox must be
reported immediately to state or federal authorities.
http://www.aphis.usda.gov/vs/area_offices.htm
State:
http://www.aphis.usda.gov/vs/sregs/official.html
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Quarantine and disinfection:
A limited outbreak of sheep or goat pox can sometimes be controlled
by depopulating infected and exposed animals, cleaning and
disinfecting affected farms and equipment, and imposing a quarantine
on animal movement. Sodium hypochlorite is an effective
disinfectant. When the disease has spread more widely, vaccination
may also be required. |
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| Links
to further information on this disease |
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Office International des Epizooties (OIE)
OIE Manual of Standards
OIE International Animal Health
Code
USAHA
FAD Book |
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| Experts |
| For current
information on experts click below: |
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| References |
Blackwell, J.H. “Cleaning and
Disinfection.” In Foreign Animal Diseases. Richmond, VA: United
States Animal Health Association, 1998, pp. 445-448.
House, J.A. “Sheep and Goat Pox.” In Foreign Animal Diseases.
Richmond, VA: United States Animal Health Association, 1998, pp.
384-391.
“Sheep Pox and Goat Pox.” Animal Health Australia. The National
Animal Health Information System (NAHIS). 11 December 2001
<http://www.brs.gov.au/usr-bin/aphb/ahsq?dislist=alpha>.
“Sheep Pox and Goat Pox.” In Manual of Standards for Diagnostic
Tests and Vaccines. Paris: Office International des Epizooties,
2000, pp. 168-177.
“Sheeppox and Goatpox.” In The Merck Veterinary Manual, 8th ed.
Edited by S.E. Aiello and A. Mays. Whitehouse Station, NJ: Merck
and Co., 1998, pp. 622-3. |
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| Key Words |
-Species
: sheep, goat
-Clinical signs
: fever,
erythematous macule, papule, papule with necrotic center, dark
sharply demarcated scab, scabs that heal slowly, conjunctivitis,
rhinitis, lymphadenopathy, depression, blepharitis, anorexia,
dyspnea, necrotic mucous membranes, mucopurulent nasal or ocular
discharge, death
-Post mortem lesions
: skin
macules, full-thickness skin papules, discrete congested or
edematous lesions in the lungs, hard white nodules in the lungs,
papules or ulcerated papules in the abomasum, papules in the
rumen, papules in the large intestine, papules in the trachea,
papules in the esophagus, papules on the tongue, papules on the
palate, papules on internal organs, pale foci on the kidney,
pale foci on the liver, pale foci on the testicles,
lymphadenopathy, necrotic mucous membranes |
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