Molecular characteristics of bovine norovirus and nebovirus in Swedish dairy herds.

BACKGROUND: Neonatal enteritis is a major cause of losses in dairy calves and bovine norovirus (BNoV) and nebovirus (NeV) are underdiagnosed contributors to this disease. In this study, we report for the first time molecular characteristics of bovine norovirus (BNoV) and nebovirus (NeV) detected in calves in Swedish dairy herds. 700 samples from preweaned calves with and without diarrhea were analysed. RESULTS: BNoV was more prevalent (19%) than NeV (4.5%), and among BNoV, the GIII.P2 genotype was more frequently detected than the GIII.P1 genotype. These viruses were detected at similar frequencies in calves with and without diarrhea. The 17 NeV partial polymerase gene sequences all clustered with the Bo/NB/80/ USA prototype strain. Also, the molecular epidemiology of BNoV GIII.P1 in a longitudinal study in one dairy herd is reported. CONCLUSIONS: In this study, we describe for the first time molecular characteristics of BNoV and NeV from Swedish dairy herds. The genotypes detected in Swedish dairy calves were similar to those detected in most of the studies from other countries within and outside Europe. Phylogenetic clustering of Swedish virus strains was detected and discussed in relation to virus transmission.