Title : SARS-CoV-2 in shellfish reared in Lesina and Varano lagoons (South-East Italy) by reverse transcription droplet digital PCR
Abstract:
Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is the causative agent of an acute respiratory disease that has rapidly spread worldwide, resulting in the SARS-CoV-2 pandemic emergency in the period 2020-2023. The virus is commonly detected in the faeces of symptomatic and asymptomatic infected patients and consequently in wastewater. Occasionally, SARS-CoV-2 has been detected in treated sewage, rivers and seawater, thus it is possible to hypothesize the presence of this virus in aquaculture. The aim of this study was to collect data on SARS-CoV-2 prevalence in bivalve molluscs, waters and sediments from harvesting areas of Lesina and Varano lagoons (South-East Italy) in order to investigate the spread of SARS-CoV-2 in shellfish farming areas and coastal environment.
The study was carried out on 143 samples of molluscs and 166 water and sediment samples collected between January 2022 and December 2023. Molluscs were collected from harvesting areas or fish shops; water and sediment samples were taken at the Lesina and Varano lagoon (North Apulia region), where there are molluscs farms. The samples were subjected to RNA extraction and tested by Reverse Transcription droplet digital PCR (RT-ddPCR) targeting N, E and RdRp genes to investigate the presence of SARS-CoV-2.
During the period considered, none of the 143 samples of molluscs and 166 water and sediment samples tested positive for the presence of SARS-CoV-2 viral RNA by RT-ddPCR method. The limit of detection (LOD) of each target gene was found to be 1 copy/μl.
The results of this study suggest that SARS-CoV-2 did not reach the shellfish farming areas of Lesina and Varano lagoons and coastal environment at significant levels to allow a bioaccumulation in molluscs. This could be explained considering the dilution effect of viral particles in water and the efficiency of the wastewater treatment systems. The RT-ddPCR assays applied in this study confirmed the high sensitivity of the method to detect low levels of nucleic acids and could be used in routine practice. This work was supported by the Italian Ministry of Health (IZSPB 04/21 RC).
Audience take-away:
- Monitoring the circulation of pathogens could be useful to evaluate the water quality of fish and shellfish farms
- Molecular testing for microbiological investigations is useful tool
