Tribulus terrestris herb has been used as a drug in traditional medicine and its toxic effects have also been reported. Less attention has been paid to the interpretation of pathological and laboratory findings in the natural form poisoning with this plant in animals. Following a report of mortalities in a sheep farm feeding on a pasture containing Tribulus terrestris herb and involvement of 50 of the animals with similar clinical symptoms, one ewe with these signs i.e. inappetance, serosal nasal discharge, dehydration, severe mucosal and scleral jaundice and rumen impaction was evaluated. Serum biochemical profile and CBC tests revealed an increasing of total protein, blood urea nitrogen, creatinine, glucose, cholesterol, triglycerides, total bilirubin, magnesium, phosphorus values and enzymes activities (ALT, ALP, GGT, CPK) and leukocytosis, neutrophilia, lymphopenia. The presence of bilirubin, protein and blood in the urine was also confirmed by the urine strip. In macroscopic observations, severe pathologic jaundice in different parts of the carcass, rumen impaction with forage materials, petechial hemorrhages in the abomasal mucosa, necrosis and ulcerative lesions in the gallbladder mucosa, presence of pinpoint dark spots on the surface of the kidney, pulmonary edema and focal white deposits on the endocardial surface of the heart were seen. Microscopically, necrosis and degeneration of the hepatocytes and myocardium, acute tubular necrosis, deposition of eosinophilic structures in the renal tubules and hemosiderin pigments in its epithelium were observed. The presence of some toxins in the herb, especially steroidal saponins, is very important in inducing hepatorenal lesions in sheep.

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