Systemic mycobacteriosis caused by Mycobacterium avium subspecies hominissuis in a sheep

Mycobacterium avium subsp. hominissuis (MAH) causes pulmonary and disseminated infections in immunocompromised humans. In pigs, MAH commonly causes subclinical infections that lead to granulomatous lesions in the mesenteric lymph nodes, liver, spleen, and jejunum. MAH infections have been reported less commonly in other animal species and in birds. Here, we report a case of systemic mycobacteriosis caused by MAH in a sheep. The affected animal had a history of hypoproteinemia, weight loss, and fever. Gross pathology findings included serous fluid accumulation in the peritoneal and pleural cavities, patchy dull granular light-red mucosa of the small intestine, diffuse orange-brown discoloration of the liver, and noncollapsing lungs that were mottled pink to dark-red. Histologically, granulomas were present in the intestines, mesenteric lymph nodes, liver, spleen, kidneys, lungs, and brain. MAH was isolated from the liver, spleen, and feces. Whole-genome sequencing revealed a mobile genetic element—an ISMAP 02 -like sequence—in the MAH genome. An ISMAP 02 -like sequence in mycobacteria other than Mycobacterium avium subsp. paratuberculosis (MAP) may interfere with the detection of MAP by PCR assays targeting ISMAP 02 .