The clinical and pathological aspects of bovine paratuberculosis in a dairy herd in the county of Capela de Santana, Rio Grande do Sul, southern Brazil, are described. Clinical signs in eight cows out of 345 cattle included chronic diarrhea refractory to treatment, progressive emaciation and decreased milk production. Necropsy findings included severe and diffuse thickening of the mucosa of the small intestine with exaggerated reticular pattern, reflected in the serosal surface, similar to cerebral gyri. Intestinal loops were filled with whitish watery contents. The lymphatic vessels of the intestinal serosa and of the mesentery were thickened and tortuous. The mesenteric lymph nodes were enlarged and, on cut surface, there were oozing of milky fluid. Plaques of mineralization were evident in the intima of larger arteries, in the endocardium of the heart valves and in the ruminal serosa. There was also edema of the abomasal folds and atrophy of the caudate lobe of the liver. The main histopathological findings were granulomatous enteritis, lymphadenitis and lymphangitis. The inflammatory infiltrate was composed of macrophages, epithelioid cells and Langhans' giant cells containing large numbers of acid-fast bacilli. Vascular lesions included degeneration, calcification and collagen proliferation of the intima and media of larger arteries. Other microscopic lesions included calcification of the ruminal serosa, diffuse hepatocellular atrophy and multifocal granulomatous hepatitis. Mycobacterium paratuberculosis was cultured in Herrold's medium enriched with mycobactin from all the eight samples of intestinal scrapings submitted to bacteriological examination.
Paratuberculosis; Mycobacterium paratuberculosis; Johne's disease; ruminants; pathology
