Study on extraintestinal tissue distribution of bovine rotavirus in naturally infected calves

Abstract

This study investigated the extra-intestinal tissue distribution of bovine rotavirus in naturally infected calves. Prominent histopathological alterations in the duodenum, jejunum, and ileum included mucosal and submucosal congestion, villous atrophy and fusion, increased crypt depth, epithelial necrosis with desquamation, moderate to diffuse mononuclear cell infiltration, and eosinophilic intracytoplasmic inclusion bodies within enterocytes. Extra-intestinal lesions comprised lymphocyte depletion with macrophage and neutrophil infiltration in the mesenteric lymph nodes (MLN); interstitial pneumonia characterized by mononuclear infiltration and type II pneumocyte proliferation in the lungs; and focal hepatocellular necrosis, either individual or clustered, predominantly near portal triads or central veins, accompanied by mononuclear infiltration. Rotavirus antigen and nucleic acid were detected in the small intestine, MLN, lungs, and liver using immunohistochemistry and SYBR Green-based real-time PCR, respectively. Quantitative analysis revealed that, aside from the intestine, the MLN (5.47 × 10? copies/mg) represented the second major site of viral replication, followed by the lungs (4.01 × 10? copies/mg). These findings demonstrate that bovine rotavirus can infect and replicate in extra-intestinal tissues, and suggest that the MLN may serve as an important site for secondary and prolonged viral replication, facilitating viral dissemination beyond the intestinal tract.