MOLECULAR CHARACTERISTICS OF SOME HIGH-RISK PATHOGENIC VIRUSES IN BIVALVE MOLLUSCS MARKETED IN HANOI IN 2016

Abstract

Aims: Norovirus (NoV), Hepatitis E virus (HEV) and Human Astrovirus (HAstV) are common human pathogenic viral agents in bivalve molluscs with frequent emergence of new variants, which pose various difficulties in fighting the epidemic. Therefore, this study aims to evaluate the molecular characteristics of viruses, thus proposing timely response measures and limiting unwanted consequences caused by food poisoning. Methods: A total of 120 samples (60 samples of oysters and 60 samples of clams) were collected at markets and supermarkets in Hanoi in 2016. The samples were analyzed for 3 indicators of Norovirus (NoV), Hepatitis E virus (HEV) and Human Astrovirus (HAstV) using Real-time RT-PCR technique. The samples that were positive for the virus were further analyzed for molecular characteristics through RT-Nested-PCR reaction, Sanger sequencing, and phylogenetic tree construction using MEGA 11 software. Results: For NoV GI, there are 5 detected genotypes: GI.2, GI.4, GI.5, GI.6 and GI.8 of which GI.5 genotype accounts for 56%. The number of genotypes of NoV GII detected is 9 types, including GII.3, GII.4, GII.6, GII.7, GII.13, GII.14, GII.17, GII.18, GII.21, with GII.3 accounting for the majority (54.8%). Three samples of HEV infection were detected, all belonging to the HEV-3 group. For HAstV, out of 6 positive samples, 4 strains of HAstV were sequenced, all belonging to HAstV-1, which is a common subtype of HAstV. Conclusion: The contamination of foodborne viruses in bivalve molluscs in Vietnam is relatively complicated with many genotypes circulating; in particular, there exist a number of genotypes capable of causing outbreaks in the community on a large scale such as NoV GII.4, NoV GII.7, HEV-3 and HAstV-1.