Sheep-pox, a highly contagious disease, causes a mortality of 20 to 50% in animals below the age of 6 months. It also causes damage to the wool and skin in adults. Of the pox diseases, sheep-pox ranks only second to human small-pox in virulence. The disease is transmissible to in-contact goats in some outbreaks but not to other species of animals. Sheep pox, caused by Capri pox virus in the family Poxviridae, is common in Africa, Asia and Europe. It is most severe form of pox disease of domestic animals and mortality rate is more than 50% in lambs.
Clinical signs: Two form of disease, namely, malignant form and benign form have been reported. Malignant form is seen in lambs, where some may die without showing any symptoms. High fever, symptoms of pneumonia, acute enteritis, and skin lesions appear particularly in parts free from wool, notably around the eyes, inner side of the thigh, udder surface of the tail. Trachea, lungs, kidneys and intestines are also affected. The disease results in emaciation and as already mentioned, frequent deaths of affected animals.
Diagnosis: The disease is diagnosed on the basis of clinical signs, lesions, and demonstration of inclusion bodies and isolation of the virus in sheep or goat kidney cell-cultures and PCR. Immunodiffision and serum neutralization tests are also employed.
Treatment, prevention and control: The diseased animals should be given palliative treatment. In the young-ones, nursing is more important than medication. The infected litter should be burnt and the bedding changed every day. Affected animals should be kept on soft diet. The ulcers on the skin should be washed with potassium permanganate lotion and dusted with boric acid; strict hygienic measures should be adopted.To control sheep-pox, use of vesicular fluid was in vogue before the vaccine was available. A couple of sheep were first inoculated with the vesicular fluid on the under surface of the tail or the inner side of the ear by scarification. In about 4 to 6 days, vesicles appeared at the spot and the fluid collected from these vesicles, mixed with equal parts of glycerol, served as a vaccine. Vaccination was done by scarification inside the ear or under the tail. In about 15 to 20 days, the animals developed resistant to the disease. This method of vaccination termed 'ovination' having live virus is not advocated.An adjuvant vaccine made with formalized sheep-pox virus grown either on sheep skin or in cell-culture and subsequently treated with aluminium hydroxide is used at present. Of late, tissue-culture vaccines using 'live attenuated strains of sheep-pox virus have been developed and being used with satisfactory results.