High frequency of porcine norovirus infection in finisher units of Brazilian pig-production systems.

Norovirus (NoV) is a member of the Caliciviridae family and is considered an emerging human enteric pathogen. NoVs are detected in farm animals such as cattle, sheep and pigs. Porcine NoV (PoNoV) is widespread worldwide, but frequency of infection is often low. This study aimed to investigate the natural PoNoV infection from adult animals of an important Brazilian pig-production region. Faecal samples (n = 112) of asymptomatic pigs aged 9 to 24 weeks old were collected from 16 grower-to-finish herds located in Paraná state, Brazilian Southern region, and evaluated for PoNoV presence. A reverse transcription-polymerase chain reaction (RT-PCR) assay was performed using specific primers that target a conserved region of the virus capsid gene (VP1). PoNoV was detected in 58 (51.8%) of the 112 faecal samples and in 14 (87.5%) of the 16 herds evaluated. Six of the obtained amplicons were submitted to phylogenetic genotyping analysis. The higher nucleotide (86.5-97.4%) and amino acid (100%) similarities of the sequences in this study were with the representative strains of the porcine NoV genogroup II genotype 11 (PoNoV GII-11). These results reveal that PoNoV infection is endemic in one of the most important pork production areas of Brazil and that the PoNoV GII-11 is prevalent in this region.