Prevalence of Porcine Noroviruses, Molecular Characterization of Emerging Porcine Sapoviruses from Finisher Swine in the United States, and Unified Classification Scheme for Sapoviruses

Abstract

Noroviruses (NoVs) and sapoviruses (SaVs) are important human pathogens. Although the involvement of porcine NoVs in disease in pigs is unclear, they are genetically and antigenically closely related to human NoVs. Human NoV-like strains have been detected in pigs, raising public health concerns of potential interspecies transmission. Porcine SaVs are highly diverse and emerging in swine populations. Recently, at least three new genogroups of porcine SaVs have been proposed. In this study, we tested 413 pooled fecal samples collected from apparently healthy finisher pigs in North Carolina swine farms during 2009. Reverse transcription (RT)-PCR coupled hybridization assays were performed to detect known porcine NoVs. The overall prevalence of porcine NoVs determined was 18.9% based on this method. Samples were then tested by RT-PCR targeting the 5= end of the capsid region for genogroup II (GII) NoVs, a group which includes human NoVs, followed by sequence analysis. All NoVs identified belonged to typical porcine NoV genotypes, and no human NoV-like strains were detected in specimens from these pigs. Porcine NoV-negative samples (n ‫؍‬ 335) were subsequently screened using universal calicivirus primers, and 17 SaV strains were confirmed by sequencing. Based on the partial RNA-dependent RNA polymerase (RdRp) region, they clustered with GIII, GVII, and GVIII and with currently unclassified SaVs. According to analysis of the complete capsid sequences, 7 representative strains clustered with GVII, GVIII, and GIX? SaVs. We tentatively classified SaVs into 14 genogroups based on the complete capsid protein VP1. In summary, porcine NoVs and highly divergent SaVs were present in North Carolina finisher pigs.

Phylogenetic Analysis of the Nonstructural and Structural Protein Encoding Region Sequences, Indicating Successive Appearance of Genomically Diverse Sapovirus Strains from Gastroenteritis Patients

“…The functions of other NS and ORF2-encoded proteins have not yet been experimentally determined. Based on the VP1 sequences, SaV can be divided into at least five genogroups (GI-GV), and recently, nine additional genogroups (GVI-GXIV) have been proposed (7). Thus far, GI, GII, GIV, and GV SaV strains have been detected in humans.…”

Occurrence of Norovirus in pig faecal samples in the Eastern Cape, South Africa

“…Previous studies have documented many sets of primers that have been utilized to detect the occurrence of porcine Norovirus with comparably minimal identification rate which indicates that Norovirus contagions are certainly rare amid swine [3]. Furthermore, a study carried out by Scheuer et al [10] documented high occurrence of Norovirus in US finisher pigs (18.9%). Infection rates of porcine enteric Calicivirus can be impacted by hygienic conditions of the farm [9] and a possibility of cross species infection could happen in humans who do not maintain proper hygiene.…”

“…Norovirus is mostly detected in finisher swine, whereas Sapovirus has been found in all different age groups of swine [10,12]. Swine illnesses are associated with porcine Sapovirus while the influence of Norovirus contagions in swine is unknown [3].…”

“…Norovirus have been observed amongst pigs from high income countries, suggesting the significance to monitor the incidence of Norovirus in swine with a view to assessing the risk in humans since Norovirus is highly diverse and new strains are continually evolving and having also the possibility of interspecies spread [10].…”

“…Pigs are susceptible to human Norovirus genogroup II, which is the main predominant genogroup causing gastroenteritis in human beings [9]. Pig strains of Norovirus are hereditarily similar to human strains which were known to replicate and show a mild pathogenicity in gnotobiotic pigs under experimentally conditions [10,11].…”