An outbreak of hepatogenous photosensitization in sheep grazing Tribulus terrestris in Argentina.

An outbreak of hepatogenous photosensitization occurred in 40% of sheep grazing Tribulus terrestris in southern Buenos Aires province. Postmortem examinations revealed diffuse jaundice and ochre discoloration of the liver. Histopathological liver lesions consisted of fibroplasia, periductular lamellar fibrosis, hyperplasia of small bile ducts and diffuse swelling of hepatocytes. A crystalloid material was observed in some bile ducts. Aspartate aminotransferase and gamma glutamyltransferase serum activities were elevated in all tested animals while serum bilirubin content was elevated only in the most severely affected sheep. These findings are consistent with reports of geeldikkop, a photosensitivity of sheep which occurs in South Africa and Australia.