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After oral administration of Mycobacterium paratuberculosis to hamsters, the organism passed the epithelial barrier of the intestine, and infection was established in the small intestine and mesenteric lymph nodes. The addition of aflatoxin to the ration of hamsters did not increase their susceptibility to M paratuberculosis but, rather, seemed to decrease susceptibility to the bacillus. Hamsters not treated with aflatoxin and infected with M paratuberculosis had higher bacterial counts in intestinal tract and mesenteric lymph node on necropsy than did infected hamsters that had been treated with aflatoxin. Aflatoxin-treated hamsters grew slowly, had an unthrifty appearance, and developed lesions of megalocytosis regardless of whether they were infected with M paratuberculosis.

Two 1-month-old calves, four 9-month old calves, and 4 adult (5 to 11 years old) cattle were exposed to Mycobacterium paratuberculosis. At 150 days after exposure, all cattle were killed and necropsied, and at that time, tissues of the 1-month-old calves had more bacilli and lesions than did tissues of the 9-month-old calves or the adult cattle. All cattle responded to immunologic tests during the experiment.

Paratuberculosis (Johne's disease) is described in a 5-month-old white-tailed deer (Odocoileus virginianus). Diagnosis was based on clinical signs and pathology.