AiV-1 is considered an emerging human enteric pathogens and foodborne transmission has been documented as an important source of exposure for humans, chiefly in relation to non-safe, risky food habits. We surveyed the presence of AiV-1 in retail shellfish, including oysters and mussles, identifying the virus in 3/170 (1.8%) of the analysed samples. The AiV-1 positive samples were of different geographic origin. Upon sequence analysis of a portion of the 3CD junction region, two AiV strains identified from harvesting areas in Northern Italy were characterised as genotype B and displayed 99-100% identity at the nucleotide level to other AiV-1 strains detected in sewages in Central Italy in 2012, suggesting that such strains are stably circulating in Italian ecosystems. Interestingly, a strain identified from mussles harvested in Southern Italy could not be characterised firmly, as inferred in the Bayesian analysis and by sequence comparison, indicating that different AiV strains are also circulating in Italy. Viral contamination in retail shellfish challenges the microbiological guidelines for food control and requires the development and optimization of additional diagnostic and prevention strategies.

Introduction

Aichi virus, a human enteric virus of the genus Kobuvirus, family Picornaviridae, was first recognized in 1989 as the cause of oyster-associated non-bacterial gastroenteritis in humans in Aichi Prefecture, Japan (Yamashita et al., 1991). The Kobuvirus genus includes three species, Aichivirus A (formerly Aichi virus) (Yamashita et al., 1998), Aichivirus B (formerly Bovine kobuvirus) (Yamashita et al., 2003) and Aichivirus C (porcine kobuvirus) (Reuter et al., 2009). The species Aichivirus A includes the prototype Aichi virus 1 (AiV-1) identified in humans, along with canine kobuvirus 1 (Kapoor et al., 2011; Li et al., 2011), feline kobuvirus 1 (Chung et al., 2013) and murine kobuvirus 1 (Phan et al., 2011). AiV-1 is a small non-enveloped virus of approximately 27–۳۰ nm in diameter with a single85 stranded, positive polarity RNA genome of 8,280 nucleotides (nt) in length. The single large open reading frame encodes a polyprotein of 2,432 amino acids that is cleaved into the structural proteins 87 VP0, VP3 and VP1 and non-structural proteins 2A, 2B, 2C, 3A, 3B, 3C and 3D (Sasaki et al., 2001; Yamashita et al., 1998). Upon sequencing of a short genome fragment of the 3C and 3D (3CD) junction region, AiV-1 has been further classified into at least 2 main phylogenetic lineages or genotypes, indicated with the letters A and B (Di Martino et al., 2013; Le Guyader et al., 2008; Yamashita et al., 2003; Yamashita 92 et al., 2000) and this is exploited for epidemiological investigations and molecular tracking of sporadic cases and outbreaks of gastro-enteritis. An AiV-1 strain identified in France has been proposed as a distinct lineage/genotype, C (Ambert-Balay et al., 2008). AiV-1 has been suspected to play a role as human gastroenteric pathogen. AiV-1-related clinical signs and symptoms include diarrhea, abdominal pain, nausea, vomiting and fever (Yamashita et al., 1991).