Persistence of the rotavirus A genome in mesenteric lymph nodes of cattle raised on farms.

Previous studies revealed that rotavirus A (RVA) is present in not only the small intestine but also various organs. It was reported that RVA persisted in mesenteric lymph nodes (MLNs) in experimental models. However, there have been no reports focused on RVA in MLNs of animals under natural conditions. In this study, in order to investigate the persistence of the RVA genome in MLNs in cattle under natural conditions, reverse transcription-semi-nested PCR was carried out to detect RVA genomes in the MLNs from 17 calves that had been subjected to autopsy examinations. RVA genomes were detected in MLNs from 10 (˜60  %) of the 17 autopsied calves. MLNs from 170 healthy adult cattle that had been slaughtered were also examined; 15 (∼10  %) of the 170 cattle had RVA genomes in their MLNs, indicating that RNA genomes are found frequently in MLNs of cattle under natural conditions. Genetic analyses revealed that RVAs in MLNs were classified as G and/or P genotypes generally prevalent in bovines. Basically, the strains in intestinal contents were genetically identical to those in MLNs from individual cattle, suggesting that bovine RVAs have the ability to spread from the intestine to MLNs. Furthermore, amongst RVA-positive cattle, six of 10 autopsied calves and 12 of 15 healthy adult cattle were negative for the virus in the intestinal contents, indicating that bovine RVA genomes can persist in MLNs after viral clearance in the digestive tract.