Sequential pathological study of intestine and their lymph nodes in experimentally infected sheep with caprine strain of Mycobacterium avium subspecies paratuberculosis

摘要

To elucidatethepathology of intestine and mesentericlymph nodes (MLN) and categorize the infection depending on various diagnostic tests in experimentally induced infection with caprine strain of Mycobacterium avium subspecie sparatuberculosis (4x109bacilli, 10 times), 31 sheep were divided in to 3 groups (15 infected, 8 in-contact and 8 control) for sequential study. Emaciation, depletion and gelatinization of mesenteric fat were observed in ascending manner from starting to termination of the experiment. Grossly, at 90 days post infection (DPI) mild thickening of intestinal mucosa, enlarged MLN, at 150 DPI, prominent thickness of i intestinal mucosa with presence of corrugations, enlarged and swollen MLN were observed, which became more prominent at 210 DPI, 270 DPI and 330 DPI. Microscopically, mild lesions consisted of focal granulomas, mostly in the Peyer's patches area of the ileum and ileocaecal valve (ICV), infiltration oflamina propria with increased number of lymphocytes and macrophagesand 1 occasional multinucleated giant cells in the ileum and jejunum at 90 and 150 DPI. Moderate lesions consisted of multiple focal granulomas containing few to numerous acid fast bacilli from proximal jejunum to the ICV, besides diffuse infiltration of lymphocytes and macrophages. Severe lesions varied from large granulomas to epithelioid cell sheets containing abundant AFB, similar to the classical paratuberculosislesions. The presence of only mild lesions (focal granuloma without AFB) in in-contactsheep suggested that caprine strain ingested with contaminated feed and water may not be sufficient to produce clinical disease, but may sensitize the sheep enough to react positively in certain immunological tests. This is important from epidemiologicand diagnostic points of view especially in the Indian situation where sheep and goats are reared side by side.