title: Prevalence and Molecular Genotyping of Noroviruses in Market Oysters, Mussels, and Cockles in Bangkok, Thailand.
abstract: Noroviruses are the most common cause of acute gastroenteritis associated with bivalve shellfish consumption. This study aimed to detect and characterize noroviruses in three bivalve shellfish species: oysters (Saccostrea forskali), cockles (Anadara nodifera), and mussels (Perna viridis). The virus concentration procedure (adsorption-twice elution-extraction) and a molecular method were employed to identify noroviruses in shellfish. RT-nested PCR was able to detect known norovirus GII.4 of 8.8 × 10(-2) genome copies/g of digestive tissues from oyster and cockle concentrates, whereas in mussel concentrates, the positive result was seen at 8.8 × 10(2) copies/g of digestive tissues. From August 2011 to July 2012, a total of 300 shellfish samples, including each of 100 samples from oysters, cockles, and mussels were collected and tested for noroviruses. Norovirus RNA was detected in 12.3 % of shellfish samples. Of the noroviruses, 7.7 % were of the genogroup (G) I, 2.6 % GII, and 2.0 % were mixed GI and GII. The detection rate of norovirus GI was 2.1 times higher than GII. With regards to the different shellfish species, 17 % of the oyster samples were positive, while 14.0 and 6.0 % were positive for noroviruses found in mussels and cockles, respectively. Norovirus contamination in the shellfish occurred throughout the year with the highest peak in September. Seventeen norovirus-positive PCR products were characterized upon a partial sequence analysis of the capsid gene. Based on phylogenetic analysis, five different genotypes of norovirus GI (GI.2, GI.3, GI.4, GI.5, and GI.9) and four different genotypes of GII (GII.1, GII.2, GII.3, and GII.4) were identified. These findings indicate the prevalence and distribution of noroviruses in three shellfish species. The high prevalence of noroviruses in oysters contributes to the optimization of monitoring plans to improve the preventive strategies of acute gastroenteritis.
authors.affiliation: Department of Microbiology, Faculty of Public Health, Mahidol University, 420/1 Ratchawithi Road, Bangkok, 10400, Thailand. leera.kit@mahidol.ac.th.
authors.forename: Leera
authors.initials: L
authors.lastname: Kittigul
authors.affiliation: Department of Microbiology, Faculty of Public Health, Mahidol University, 420/1 Ratchawithi Road, Bangkok, 10400, Thailand.
authors.forename: Anyarat
authors.initials: A
authors.lastname: Thamjaroen
authors.affiliation: Department of Microbiology, Faculty of Public Health, Mahidol University, 420/1 Ratchawithi Road, Bangkok, 10400, Thailand.
authors.forename: Suwat
authors.initials: S
authors.lastname: Chiawchan
authors.affiliation: Department of Protozoology, Faculty of Tropical Medicine, Mahidol University, Bangkok, 10400, Thailand.
authors.forename: Porntip
authors.initials: P
authors.lastname: Chavalitshewinkoon-Petmitr
authors.affiliation: Department of Microbiology, Faculty of Public Health, Mahidol University, 420/1 Ratchawithi Road, Bangkok, 10400, Thailand.
authors.forename: Kannika
authors.initials: K
authors.lastname: Pombubpa
authors.affiliation: Department of Microbiology, Faculty of Public Health, Mahidol University, 420/1 Ratchawithi Road, Bangkok, 10400, Thailand.
authors.forename: Pornphan
authors.initials: P
authors.lastname: Diraphat
mesh_terms: D000818:Animals; D049872:Bivalvia / Q000821:virology*; D049873:Cardiidae / Q000821:virology*; D005506:Food Contamination / Q000032:analysis* / Q000706:statistics & numerical data; D005838:Genotype; D029322:Norovirus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D010125:Ostreidae / Q000821:virology*; D010802:Phylogeny; D015995:Prevalence; D012367:RNA, Viral / Q000235:genetics; D012758:Shellfish / Q000821:virology*; D013785:Thailand
chemical_list: D012367:RNA, Viral
keywords: Bivalve shellfish; Genotype; Norovirus; RT-nested PCR