Pythiosis of the digestive tract in sheep.

Cutaneous and rhinofacial infections by Pythium insidiosum have previously been reported in sheep in Brazil. In the current study, a new form of pythiosis involving the alimentary tract of 2 nursing lambs from 2 different farms in the semiarid region of Brazil is described. The first lamb showed food regurgitation, lethargy, and anorexia, and died 5 days after the presentation of clinical signs. The second lamb had no history of gastrointestinal disease before death. Necropsy findings were similar in both lambs. The mucosa of the esophagus, reticulum, rumen, omasum, and abomasum showed ulcerated areas covered by yellowish caseous granular exudate. The lesions were transmural and extended to the serosal surfaces, and adhesions were observed between the serosa of the forestomachs and abomasum to the liver and diaphragm. Histologic lesions consisted of pyogranulomatous necrotizing transmural esophagitis, rumenitis, reticulitis, omasitis, and abomasitis with vascular thrombosis and intralesional hyphae. Pythium insidiosum was confirmed as the etiology by immunohistochemistry and culture. The presence of sheep in the vicinity of water ponds during the hot, dry season when forage is not available in the pastures seems to be the main predisposing factor for the occurrence of pythiosis in sheep in the Brazilian semiarid region.