Systematic Veterinary Virology

DIFFERENTIAL DIAGNOSIS

• SGP should be differentiated from bluetongue, Peste des petits ruminants, contagious ecthyma, photosensitisation, dermatophilosis, insect bites, parasitic pneumonia, caseous lymphadenitis and mange (scrabies).
• Bluetongue — Animals are depressed and have a nonpurulent conjunctivitis. The muzzle is swollen, congested, and edematous, and there may be a coronitis. Deformed aborted fetuses and deformed newborn sheep and goats may be encountered.
• Peste des Petits Ruminants — Conjunctivitis, rhinitis, and oral lesions that are white, raised, and necrotic are common. Pneumonia, diarrhea, and mortality approaching 90 percent in lambs and kids under 1 month of age are characteristic signs.
• Contagious Ecthyma (contagious pustular dermatitis, ORF) — This disease is most severe in lambs and kids. The proliferative pox lesions are common on the muzzle and eyes of affected neonates; mortality may approach 50 percent. Nursing females may have proliferative pox lesions on the teats and muzzle. This is a zoonotic disease; lesions in attendants are not uncommon.
• Photosensitization — Dry, flaky, inflamed areas are confined to the nonpigmented parts of the skin.
• Insect bites — The trauma from insect bites may cause local inflammation, edema, and pruritus. Insects seldom bite mucous membranes.
• Parasitic pneumonia — Severe signs of respiratory distress may occur with extensive parasitic lesions; in these cases, there is no pox lesion in the skin.
• Caseous lymphadenitis — Focal, raised lesions in the skin represent caseous abscesses; abscesses are not seen in SGP.
• Streptothricosis (Dermatophilus congolensis infection) — Lesions are superficial and often moist. Lesions are common in the skin of the neck, axillary region, inguinal region, and perineum. The organism may be demonstrated by Giemsa staining.
• Mange - Scab-like skin lesions are seen in psoroptic mange. Itching and scratching are not seen in SGP.