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.

Dorsal thermal necrosis in a Brazilian sheep flock

“…These are the main mechanisms related to skin necrosis affecting mostly the dorsal areas of affected sheep in this study. Previous reports of DTN in sheep are rare; it has only been described in Uruguay (García et al 2019) and Australia (Butler & Bergman 2006). This lack of knowledge, in our experience, has resulted in frequent misdiagnosis of DTN as other forms of dermatological disease, mostly primary or secondary photosensitization, that are ordinary diseases caused by several toxic plants in Brazil (Schwartz et al 2018, Mendonça & Riet-Correa 2023.…”

“…The skin temperature was 39.6°C, demonstrating that the effects of absorbed radiation remained mainly on the surface of the wool (Haddade et al 2018), which may explain why the wooly sheep exhibited fewer lesions when compared to the short-haired sheep. In reports of thermal necrosis in sheep, recent clipping was the main predisposing factor to injury in sheep (Butler & Bergman 2006, García et al 2019.…”

“…This condition was described in eight sheep in Uruguay. It was characterized by extensive, wide, and linear necrosis of the dorsal skin, extending from the interscapular to the lumbosacral area in eight sheep with black skin (García et al 2019). The lesion is compatible with a burn and occurs because black skin absorbs approximately 45% more solar radiation than white skin and can produce thermal energy, causing tissue carbonization (Mauldin & Peters-Kennedy 2015).…”

Putative Novel Atypical BTV Serotype ‘36’ Identified in Small Ruminants in Switzerland

“…Another study revealed Pastinaca sativa as the cause of photosensitization via contact photodermatitis leading to severe necrotizing dermatitis in goats [ 39 ]. Recently, un-induced thermal burns leading to dorsal skin necrosis in Texel sheep were reported in Uruguay, particularly in obese sheep, sheep with dark skin or after sunlight exposure during hot months after shearing [ 40 ]. However, the evidence of solar-induced skin necrosis or photosensitization caused by plant contact or ingestion remains unproven for the goats of the Swiss pasture.…”