Etiology
Two types of viruses are incriminated. The viruses are not well defined. One of the viruses is believed to be specific for sheep while the other one affects sheep and goat.
Occurrence
It is endemic in southern Asia, Africa, north of equator and parts of Asia like India, Iran and neighboring countries.
Transmission
The virus specific for sheep occurs when there is direct contact between sick and healthy sheep. Infected dust helps in disease spread. Some virus strains affecting sheep and goats are spread by arthropods. Intrauterine infection occurs. Lambs have been born with pocks lesions.
Clinical signs
Clinical reactions may be peracute, acute or subacute. Peracute infections are seen in indigenous lambs and exotic sheep brought into endemic areas. It is characterized by generalized haemorrhages while spreading cutaneous ulceration and death before pocks develop.
In acute disease, there is fever, ocular and nasal discharge, salivation, papules emerge on mucous membrane and thin skin areas of the body.
Papules are crusted with exudates.
Crusts become scabs and darken. Irritation is intense and self mutilation is common. Death can occur at any stage after the appearance of pocks. Healing of lesion results in permanent scar formation.
Subacute reactions are characterized by low grade fever and lesions appear on restricted areas like head and under the tail.
Diagnosis
This is based on history, clinical signs and post-mortem lesions.
It is also diagnosed using agar gel diffusion test.
Differential diagnosis
Orf
Mange
Cutaneous streptotricosis
Blue tongue
Immunology
Each type of virus induces durable active immunity in surviving animals but there is no cross protection between the two major types.
Live and inactivated vaccines are available. The former is administered by scarification and produces immunity for a long time. The later vaccine produces immunity that last for about a year.
Control
For free areas, ensure their freedom from sheep pox by not importing sheep and goat from endemic areas.
Destruction of infected sheep and goat and vaccination of in-contact sheep and goat is necessary. In endemic areas, it is recommendable to vaccinate regularly.
Treatment
Systemic antibiotic therapy should be administered.
Keep the animals warm in clean environment.
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