Rotavirus A associated pathology of intestine and mesenteric lymph nodes and occurrence in bovine calves of Gwalior and Bareilly regions

To understand the pathology of natural cases of rotavirus (RVA) in bovine calves, a total of 40 cases below 6 months died due to diarrhoea were studied, out of which 7 cases (17.5%) turned positive for RVA by RT-PCR. Histopathology of small intestine showed loss of villous enterocytes, blunting and fusion of villi, elongation of crypts and mononuclear cells infiltration in the lamina-propria. The mesenteric lymph nodes were severely depleted of lymphocytes. These changes were corroborated with presence of RVA antigen in sections by dFAT and nucleic acid by RT-PCR. The fluorescent signals were more in mesenteric lymph nodes than in intestine. Besides, 115 rectal fecal samples were also collected from calves for RVA detection by RT-PCR using VP6 gene specific sets of primers. Dead carcasses of calves (n= 40) belonged to organized dairy farm of Bareilly, while rectal fecal samples belonged to both organized (n= 38) and unorganized farms (n= 77) of Bareilly and Gwalior. The overall occurrence of RVA was 19.3% (30/155), comprising 5/37 cases (13.5%) from Gwalior (MP) and 25/118 cases (21.1%) from Bareilly (UP). These findings suggest the infection of RVA widely prevalent in calves and have potential to escape from the intestinal site to mesenteric lymph nodes.