All sheep grazed on a pasture of Brachiaria decumbens cv. Basilisk of about 1 hectare. The pasture was green and at the blooming phase. The flock was supplemented with a protein-energy-mineral mixture. In a neighboring pasture of 1.5 hectares grazed by 124 adult cattle without photosensitization B. decumbens had greater quantities of dry leaves. It was part of a pasture rotation system in which the animals stayed for 8 days.
Six lambs and an adult sheep showed clinical signs characterized by anorexia, depression, dry muzzle, dermatitis of the ears and face, and ocular and nasal yellowish secretion. Five lambs and an adult sheep died after a clinical manifestation period of up to 5 days. The three lambs examined (Sheep 1, 2 and 3) had increased values of GGT, CB, UCB, TB and cholesterol, but in the two adult healthy sheep these parameters were within normal range (Table 1).
At necropsy, an adult sheep in moderate body condition showed unilateral corneal opacity, dry muzzle, moderate jaundice, increased lobular pattern of the liver and a distended gallbladder.
Histologically, the main alteration in the liver were the cholesterol-like, needle-shaped, crystals negative images in the lumen of some bile ducts, associated with a periductular moderate infiltration of mononuclear inflammatory cells (Fig.1). In the small bile ducts epithelial cells were degenerated or necrotic. Proliferation of bile duct cells was also observed. There was a diffuse severe swelling and vacuolation of hepatocytes. A mild amount of foamy macrophages was observed, mainly in the centroacinar zone, some of them also containing negative images of crystals. The heart showed multifocal areas of degeneration and necrosis of muscular fibers associated with connective tissue proliferation and mild infiltration of mononuclear cells. In the kidneys, cholesterol-like, needle-shaped, negative images of crystals were observed in the lumen of some tubules, occasionally with presence of giant multinucleate cells.
No Pithomyces chartarum spores were found in the pasture samples from the sheep paddock, and only 5,000 spores per gram of pasture, were found in the paddock grazed by cattle. The levels of protodioscin of B. decumbens were 2.36 and 1.63% for the sheep and cattle paddocks, respectively.
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