Pathology of paratuberculosis in sheep as confirmed by ISMav2 gene real-time polymerase chain reaction

The present investigation was carried with the objective to study the prevalence and pathology of naturally occurring paratuberculosis in sheep showing chronic enteritis. Out of 300 sheep examined postslaughter, samples from 50 sheep (16.7%) exhibiting various degree of thickening or corrugation of intestinal mucosa (ileum and ICV) and enlargement of lymph nodes were collected. Small pieces of tissues from the affected sheep were also collected on ice for genomic detection of Mycobacterium avium subspeies paratuberculosis (MAP) targeting ISMav2 gene by quantitative real-time PCR (qRT-PCR) method. In the intestine various pathological conditions such as chronic diffuse gmulomatous enteritis (multibacillary paratuberculosis) (12%), chronic focal granulomatous enteritis (paudbacillary paratuberculosis) (24%) and chronic enteritis (64%) without granuloma formation were observed. Multibacillary lesions were characterized by diffuse infiltration of epithelioid macrophages loaded with clusters of AFB in small intestine and mesenteric lymph nodes (MLN) of all cases. Paudbacillary lesions were characterized by the presence of multiple microgranuloma in the cortex and paracortex of lymph nodes and loosely arranged macrophages in the small intestine with AFB demonstrable in 4 (33%) sheep. Chronic enteritis, without granuloma formation and detectable AFB, were characterized by moderate to severe infiltration of lymphocytes, mixed with macrophages and eosinophils. Eight (16%) of these cases were assodated with parasitic nodules (Oesophagostomosis). The ISMav2 gene was detected in 25 (50%) cases which induded all multibacillary cases, 50% of paudbacillary cases and 40.63% of chronic enteritis (non-granulomatous) cases. It was conduded that Johne's disease was quite prevalent in sheep of unorganized sector also, and ISMav2 was found to be a sensitive test for the diagnosis of Johne's disease in sheep.