Solar-induced dorsal skin necrosis in sheep

Abstract

Background: Solar-induced thermal burns of dark skin over the dorsum have been reported in dogs, sheep and a pig. Objectives: This report describes an outbreak of solar-induced thermal burns over the dorsal skin of criollo and Texel sheep in Uruguay. Animals and methods: Cross-bred criollo and pure-bred Texel adult ewes from a flock of 80 animals presented with severe skin lesions. Eight animals were evaluated clinically and skin biopsy specimens were collected from three ewes for histopathology. Epidemiological data were collected. Results: Black/brown criollo sheep presented with extensive, wide, linear dorsal skin necrosis extending from the interscapular to the lumbosacral area. Necrotic skin was firm, dry and largely detached from the underlying subcutis. Nonpigmented Texel sheep showed milder lesions with rapid re-epithelialization and healing. Histological features were consistent with third-degree burns, characterized by full-thickness coagulative necrosis of epidermis and dermis, including blood vessels and adnexa. The cumulative incidence of the disease was 21% during the 30 days post-shearing, affecting 50% of criollo and 7.4% of Texel sheep (P < 0.001). Conclusions: The findings are consistent with post-shearing, sun-induced thermal burns leading to dorsal skin necrosis. Risk factors include sunlight exposure during hot months after shearing, dark skin and obesity.