First detection of bovine noroviruses and detection of bovine coronavirus in Australian dairy cattle.

BACKGROUND AND OBJECTIVE: Noroviruses have been recognised as a significant cause of neonatal enteritis in calves in many countries, but there has been no investigation of their occurrence in Australian cattle. This study aimed to establish whether bovine noroviruses could be detected in faecal samples from Australian dairy cattle. It also sought to determine whether bovine coronaviruses, also associated with neonatal enteritis in calves, could be detected in the same faecal samples. METHODS: A selection of faecal samples that were negative for rotaviruses from dairy farms located in three geographically distinct regions of Victoria were pooled and tested by reverse transcription-PCR for the presence of noroviruses (genogroup III), neboviruses and bovine coronaviruses. RESULTS AND CONCLUSION: Genetically distinct genogroup III noroviruses were detected in two sample pools from different geographic regions and bovine coronavirus was detected in a third pool of samples. This is the first report of bovine norovirus infection in Australian cattle and suggests that future work is required to determine the significance of these agents as a cause of bovine enteric disease in Australia.

Norovirus mixed infection in an oyster-associated outbreak: an opportunity for recombination.

We describe an outbreak of gastroenteritis in which the nucleic acid of three distinct noroviruses was amplified from the same fecal sample. To enable the separate amplification of each virus, an inclusion/exclusion RT-PCR primer design strategy was developed. This paired a virus-specific exclusion primer (designed with the exact sequence of one virus in a region displaying low conservation among the three viruses) with a virus-nonspecific inclusion primer (designed in a conserved region). Thus, in each reaction the exclusion primer provided specificity for a single virus, and the inclusion primer increased the sensitivity and allowed hybridization in a region of unknown sequence. Analysis of the partial genomic sequences of the three viruses (3.6-3.8 kb) indicated that each virus belonged to a separate genogroup II cluster, and each displayed evidence of a potential recombination event when the sequences were compared with other published norovirus sequences. Our results, which show a mixed norovirus infection in a single individual, confirm the need to be aware of the possibility of mixed norovirus infections, and of the possibility of genomic recombination causing anomalies in phylogenetic analyses in such instances.