Mycobacterium species related to M. leprae and M. lepromatosis from cows with bovine nodular thelitis.

Bovine nodular thelitis is a granulomatous dermatitis associated with infection with acid-fast bacteria. To identify the mycobacterium responsible for this infection, we conducted phylogenetic investigations based on partial sequencing of 6 genes. These bacteria were identified as an undescribed Mycobacterium species that was phylogenetically related to M. leprae and M. lepromatosis.

Inducible nitric oxide synthase immunoreactivity in the granulomatous intestinal lesions of naturally occurring bovine Johne's disease.

Inducible nitric oxide synthase (iNOS) is important in the control of a number of intracellular pathogens, including mycobacteria, and is a marker of classic macrophage activation. In human granulomatous diseases such as leprosy, a spectrum of granulomatous lesions is described, ranging from the tuberculoid to lepromatous types. Tuberculoid granulomas are associated with enhanced iNOS production and improved clinical outcomes over the lepromatous types. The aim of this study is to determine whether an association exists between morphology of bovine Johne's disease granulomas and lesion macrophage effector functions. To accomplish this, we retrospectively evaluated 24 cases of bovine Johne's disease. In each case, we recorded the predominant granuloma morphology and evaluated iNOS immunoreactivity and bacterial burden by acid-fast stains and mycobacterial immunolabeling. The results of this study demonstrate that all cases had granulomas with features most similar to the lepromatous type. This morphology correlated with heavy bacterial burdens demonstrated by acid-fast staining and mycobacterial immunoreactivity. None of the cases had high expression of iNOS in mycobacterial-positive granulomas. When iNOS immunoreactivity was identified, it was usually located near the crypts and was distinct from the granulomatous foci.

Pathology of spontaneous and experimental infection of North American wild ruminants with Mycobacterium paratuberculosis.

Spontaneous paratuberculosis was studied in free-ranging and captive bighorn sheep (Ovis canadensis), and Rocky Mountain goats (Oreamnos americanus). Lesions of paratuberculosis in these species resembled the disease in domestic sheep and goats. Mycobacterium paratuberculosis cultured from bighorn sheep was used to orally infect bighorn x mouflon (Ovis musimon) hybrid sheep, elk (Cervus elaphus nelsoni), mule deer (Odocoileus hemionus), and white-tailed deer (Odocoileus virginianus). Clinical paratuberculosis developed only in mule deer and was characterized by poor growth and diarrhea. Gross lesions were mild in all species. Enlargement of mesenteric lymph nodes was mild to moderate; the wall of the distal small intestine was affected minimally. Focal to diffuse infiltrates of epithelioid macrophages and giant cells occurred in the cortex of mesenteric lymph nodes, around mesenteric lymphatics, and in the intestinal mucosa. Extraintestinal lymph nodes, spleen, liver, and lung were involved in some animals; focal necrosis and mineralization was present in all species but was severe and widespread in the cervids.