Abstract
The enteric viruses, including adenovirus (AdVs) and norovirus (NoVs), in shellfish is a significant food safety risk. This study investigated the prevalence, seasonal occurrence, genetic diversity, and quantification of AdVs and NoVs in the water and cultured shellfish samples at the four major coastal oyster breeding farms (COBF), five major fishing ports (FP), and their markets in Taiwan. The AdVs/NoVs in the water and shellfish samples were isolated by the membrane filtration and direct elution methods. The RNA of NoVs was reverse-transcribed into complementary DNA through reverse transcription reaction. Further NoVs and AdVs were detected using nested PCR. A higher detection rate was recorded in the low-temperature period than high-temperature. Detection difference was noted between nested PCR and qPCR outcomes for AdVs. The total detection rate of AdVs was higher in the water samples (COBF-40.6%, FP 20%) than the shellfish samples (COBF-11.7% and FP 6.3%). The AdVs load in the water and shellfish samples ranged from 1.23 × 103 to 1.00 × 106 copies/L and 3.57 × 103 to 4.27 × 104 copies/100g, respectively. The total detection of NoVs was highest in the water samples of the FP and their market shellfish samples (11.1% and 3.2%, respectively). Genotyping and phylogenetic analysis were identified as the prevalent AdVs and NoVs genotypes in the water and shellfish samples: A species HAdVs serotype 12; F species HAdVs serotype 41; and C species PAdVs serotype 5 (NoVs GI.2, GI.3 and GII.2). No significant differences were observed between the presence of AdVs, and all of the water quality parameters evaluated (heterotrophic plate count, water temperature, turbidity, pH, salinity, and dissolved oxygen). The virus contamination occurs mainly due to the direct discharge of domestic sewage, livestock farm, and fishing market wastewater into the coastal environment. Thus, this study suggested framing better estuarine management to prevent AdVs/NoVs transmission in water and cultured/distributed shellfish.
Highlights
Enteric viruses are frequently detected in environmental waters, including coastal and estuarine regions, and may be associated with water contamination by fecal pollution
The total detection rate of AdVs was the highest in the water samples of coastal oyster breeding farms (COBF) (40.6%) and fishing ports (FP) (20%)
It was followed by the shellfish samples of COBF (11.7%) and FP (6.3%)
Summary
Enteric viruses are frequently detected in environmental waters, including coastal and estuarine regions, and may be associated with water contamination by fecal pollution. The discharge of effluents from the wastewater treatment plants directly into the coastal ecosystem may contaminate water sources and lead to the continuous release of human viruses into the coastal environment, which may cause serious human health hazards These viruses can survive for a long time either in the water or by attaching to particulate matter and subsequently getting accumulated in sediments [1]. Shellfish are cultured in inshore coastal environments, which may pollute with significant quantities of fecal contaminants from urban runoff, point-source discharges, and disposal from boats [2]. They can filter the neighboring water from their surroundings by their bioaccumulation capacity for feeding. Consumption of contaminated shellfish can lead to many enteric virus outbreaks since shellfish is often consumed raw or half-cooked [4,5]
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