engleski

Viral contaminants of bivalve molluscan shellfish harvested from production areas in Croatia: the results of a three-year study

Bivalve molluscan shellfish (BMS) are prone to microbial contamination due to their filter- feeding nature. Whilst bacterial contamination is being monitored by E. coli count, viral contamination is overlooked. Nevertheless, the outbreaks in the community are occurring and their frequency is probably underestimated. Our study aimed to identify the extent of BMS contamination by norovirus (NoV), rotavirus A (RVA), hepatitis E virus (HEV) and SARS-CoV-2 in Croatia. During three years (2018-2021) 275 digestive tissue samples (2 g pools of hepatopancreas) were collected from three species of BMS (Mediterranean mussels, N= 203 ; European flat oysters, N= 61 ; and warty venus clams, N= 11) harvested from commercial production areas (N= 22) on the Croatian side of the Adriatic Sea. The virus concentration procedure and RNA extraction were conducted according to the standard ISO 15216-1 2017, using Mengovirus as a whole process control. The NoV (GI and GII), RVA, HEV, SARS-CoV-2 (on 77 samples collected in 2020/2021) and Mengovirus were detected by RT-qPCR. The results reveal the anthropogenic influence with NoV detected in 30.8% (GI 10.9% and GII 26.3%) and RVA in 23.3% of BMS samples. Mussels were the most affected by viral contamination (NoV 37.2% and RVA 30.6%), followed by oysters (NoV 15.3% and RVA 1.7%) and clams (NoV negative and RVA 9.1%). Nevertheless, no evidence of HEV and SARS-CoV-2 circulation in BMS was observed. The genomic quantities of RVA and NoV were mostly up to 300 gc/g of digestive tissue. Seasonal variations were observed, especially regarding NoV with the highest contamination rate (60% NoV positive BMS samples) observed in the winter 2018/2019 which corresponded to the outbreak reported in humans at that time. The outbreak of NoV GII was connected to the consumption of contaminated BMS from two production sites in Southern Croatia. Our study emphasizes the importance of regular monitoring of BMS for potential viral contamination, especially concerning NoV and RVA. On the contrary, low public health risk was observed regarding SARS-CoV-2 and HEV.

: bivalve molluscan shellfish, Croatia, norovirus, rotavirus A, SARS-CoV-2, HEV

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