Frequent Detection of Noroviruses and Sapoviruses in Swine and High Genetic Diversity of Porcine Sapovirus in Japan during Fiscal Year 2008

Abstract

A molecular biological survey on porcine norovirus (NoV) and sapovirus (SaV) was conducted in Toyama Prefecture, Japan, during fiscal year 2008. Both NoV and SaV were detected from swine fecal samples throughout the surveillance period, indicating that these viruses were circulating in this region. NoV strains detected in this study belonged to three genotypes that are known as typical swine NoVs. Although human NoVs were occasionally detected, it was unclear whether they replicated in pigs. As for SaV, genogroup VII (GVII) and other divergent genogroups were identified in addition to the dominant genogroup, GIII, which is the prototypic porcine SaV. In addition, 3 strains genetically related to human SaV were detected. Two of these 3 strains were closely related to human SaV GV. Our study showed that genetic diversification of porcine SaV is currently progressing in the swine population.

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

“…These differences could be due to different geographical locations, different ages of pigs sampled, or the use of different detection methods and primers with various specificities. Most porcine NoVs belong to the typical porcine genotypes (GII.11, -18, and -19), but human GII NoV-like RNA (GII.2, -3, -4, and -13) was occasionally detected from pigs in Asia (8,15). Overall there was no significant prevalence difference among the disinfection treatments (biocides and water control; see Table S1 in the supplemental material).…”

“…Even though different ages of pigs were tested, NoVs were detected only in finisher pigs (7). A Canadian study reported 25% prevalence (41), and many other studies found lower prevalence rates: 2% to 4.6% in Europe (5, 42), 9% in New Zealand (43), 8% in Brazil (44), and Ͻ1% to 15% in Asia (8,15,22). These differences could be due to different geographical locations, different ages of pigs sampled, or the use of different detection methods and primers with various specificities.…”

“…4 and GII.12 NoVs can replicate in experimentally inoculated gnotobiotic piglets (13,14). Recently, human NoV-like NoV RNA has been detected in feces of commercially reared pigs, some of which were simultaneously infected with porcine NoVs (8,15). This is especially worrisome, even at low levels of infection, since recombination commonly occurs among NoVs within the same genogroup (16), and coinfections of human and porcine NoVs in pigs could potentially result in novel recombinant strains with broader host ranges.…”

“…Recently, at least three more SaV genogroups (GVI, GVII, and GVIII) have been proposed based on complete capsid sequences, and several porcine strains are not yet classified (19)(20)(21)(22)(23)(24). One study found porcine SaVs genetically closely related to human GV SaVs (15). Some novel genogroups have been suggested based on analysis of the partial RNA-dependent RNA polymerase (RdRp) region (25), but capsid sequences are presently unavailable for these strains.…”

Prevalence of Recovirus-Neutralizing Antibodies in Human Serum Samples

“…On the other hand, human NoVs can replicate in gnotobiotic pigs, which indicates the possibility of the emergence of swine-human recombinant NoVs or that swine could serve as reservoir for human NoVs. Recently, the detection of human G2.3, G2.4, and G2.13 NoVs that were associated with human outbreaks in the same year was reported in swine in Japan (10). However, the low copy numbers of these viruses compared to swine NoV strains raises questions about whether the human NoVs replicated in the pigs or were the result of environmental contamination.…”