Ostertagiosis in captive bison in New York State: report of nine cases.

Type II ostertagiosis was found at necropsy in 9 American bison (Bison bison) from 3 farms in New York. Clinical signs included severe diarrhea, emaciation, unthrifty coats, anemia, and weakness. In severely affected animals, the macroscopic abomasal changes consisted of irregular thickening and edema of the mucosa, resulting in a pebbly or morocco-leather appearance. Microscopically, many gastric pits and glands were dilated, lined by hyperplastic epithelium, and contained nematode sections or debris. Parasites recovered included Ostertagia ostertagi, Trichostrongylus axei, Trichostrongylus lerouxi, Cooperia oncophora, Haemonchus contortus, Nematodirus helvetianus, Trichuris discolor, Setaria labiato-papillosa, Dictyocaulus viviparus, Hypoderma lineatum, and Sarcocystis sp. Nodules in the small and large intestine were attributed to Oesophagostomum sp. Trichostrongylus lerouxi, Trichuris discolor, and Nematodirus helvetianus are reported from bison for the first time.