Causative agent
- Orf virus, family Poxviridae
Synonyms
- Orf, contagious ecthyma of sheep, scabby
mouth sore mouth
Differential diagnosis
- Sheep pox or goat pox
- Ulcerative dermatosis
- Foot and mouth disease
- Bluetongue
1. History taking
- Mainly young lambs and kids
- High morbidity (up to 100%) but low mortality rate
- Death due to complication of the invasion of
screw-worm fly or bacterial infection
- The virus persists in the environment in dust, wool and soil of affected pasture for long period (more than 12 yr) and acts as the source of the new infection
- Sheep recovered from a natural infection are
highly resistant to reinfections
2. Clinical examination
- Primary lesion on the skin of the lips and the
nostrils
- On the feet (around the coronet), thigh, axilla,
vulva, or udder of ewes, and other part covered
by short hairs
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- The more severely affected lambs fail to eat and
loss of condition
- The lesions papules, vesicles, pastulars and ulcer
formation in 3-4 days, by large scabs within one
week and peel of the skin within 3-4 weeks
3. Histopathological observation
(material by biopsy)
- Hydropic (ballooning) degeneration of the cells
of the upper layers of the epidermis with
polymorphonuclear cells infiltration
- Inclusion bodies (4-8 microns in diameter) in the
cytoplasm of epidermal cells
4. Antigen detection
Specimen : proliferative lesions infected scab
material or epithelial cell scrapings
Method : electron microscopic examination in
the early stage of the disease
Control and treatment
- Antibiotic treatment
- 5% copper sulphate solution, 7% iodine solution
or creosole dip to combat secondary infection
- Brush small amount of live virus vaccine (prepared
from 1% scab material in glycerine buffer) over
the sacrified skin on the inside of the thigh
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