Photosensitization problems in livestock.

Photosensitization is a sunburn-like condition caused by the presence of certain photoactive compounds in the skin when it is exposed to the appropriate wavelength of light. Most photoactive compounds (phototoxic agents) that cause PS in livestock are of plant origin, others are drugs, chemicals, or endogenous porphyrins. Photosensitization is a disease caused by phototoxic xenobiotics, or by acquired or hereditary dysfunction of (1) heme synthesis or (2) PE excretion by the liver. Hepatotoxins, especially those of plant origin, most frequently are the cause of the condition. Photosensitization primarily is a disorder of sheep and cattle, but all classes of livestock are susceptible. Clinical recognition of the syndrome usually presents no difficulty because of the restriction of lesions to areas of skin unprotected from sunlight. Prognosis generally depends on the extent of hepatic injury. The most important elements of treatment are termination of exposure to the photo- or hepatotoxin, protection from light, treatment and prevention of infection and fly strike, and provision of nutritious feed.