Experimental infection of pigs with group A rotavirus and enterotoxigenic Escherichia coli in India: gross, histopathological and immunopathological study.

The authors describe a detailed study conducted in Assam, India, of gross, histopathological and immunopathological alterations in pigs experimentally infected with rotavirus and enterotoxigenic Escherichia coli (ETEC) expressing K88 pili. A total of 30 Caesarean derived piglets were infected experimentally with rotavirus alone or in combination with ETEC to study the gross and histopathological alterations and the distribution pattern of different B- and T cell subsets in the gut. Villus atrophy, especially in the jejunum and ileum, was the consistent lesion in piglets infected with rotavirus, while in piglets simultaneously infected with rotavirus and ETEC, severe necrosis of the intestinal villi was observed. Ultrastructural studies revealed similar pathological alterations in the ileum of the infected piglets. A morphometric study of the intestinal villi and crypts showed a reduction in the ratio between the average villus height and crypt depth (VH:CD ratio) in the group infected with rotavirus (5.95±0.33) and those infected with rotavirus and ETEC (7.90±0.16). A higher (p<0.01) reduction in the VH:CD ratio was observed in the jejunum (8.83±0.79) and ileum (8.46±0.78) compared that in the duodenum (10.03±0.50) of the infected pigs. Piglets infected with rotavirus and sacrificed on day 6 post infection revealed the presence of lymphocytes containing cytoplasmic IgA+ (cIgA+) cells in the villus lamina propria and intra-epithelial CD8+ T cells in the villus epithelia. Rotavirus infection of young piglets in association with ETEC was more severe than rotavirus infection alone. Such infection resulted in marked clinico-pathological and immunological alterations in the infected piglets.