Bioaccumulation Efficiency, Tissue Distribution, and Environmental Occurrence of Hepatitis E Virus in Bivalve Shellfish from France

Abstract

dHepatitis E virus (HEV), an enteric pathogen of both humans and animals, is excreted by infected individuals and is therefore present in wastewaters and coastal waters. As bivalve molluscan shellfish are known to concentrate viral particles during the process of filter feeding, they may accumulate this virus. The bioaccumulation efficiencies of oysters (Crassostrea gigas), flat oysters (Ostrea edulis), mussels (Mytilus edulis), and clams (Ruditapes philippinarum) were compared at different time points during the year. Tissue distribution analysis showed that most of the viruses were concentrated in the digestive tissues of the four species. Mussels and clams were found to be more sensitive to sporadic contamination events, as demonstrated by rapid bioaccumulation in less than 1 h compared to species of oysters. For oysters, concentrations increased during the 24-h bioaccumulation period. Additionally, to evaluate environmental occurrence of HEV in shellfish, an environmental investigation was undertaken at sites potentially impacted by pigs, wild boars, and human waste. Of the 286 samples collected, none were contaminated with hepatitis E virus, despite evidence that this virus is circulating in some French areas. It is possible that the number of hepatitis E viral particles discharged into the environment is too low to detect or that the virus may have a very short period of persistence in pig manure and human waste.

Tulane Virus as a Potential Surrogate To Mimic Norovirus Behavior in Oysters

“…Samples of each tissue type were extracted together (e.g., all gills together), and all tissues were extracted in triplicate as described previously (25,36). Briefly, MgV (2 ϫ 10 6 RNA copies) was added as an extraction efficiency control to each dissected tissue (1.5 g) before homogenization, except to oysters contaminated with MgV.…”

Bioaccumulation and persistence of faecal bacterial and viral indicators in Mytilus edulis and Crassostrea gigas

“…8 and 24 ⁰ C) over a 96 hour exposure period. Previous shellfish bioaccumulation studies have predominantly evaluated bacteria 14,20 , protozoa 26 , enteric viral pathogens 6,12 and bacteriophages 1,13 in clams 6 , mussels 6,14,20 and oysters 1,6,13,26 . This study represents the first known attempt to investigate bioaccumulation of human-specific bacteriophages infecting B.…”

“…On each occasion, three C. gigas and five M. edulis were removed from the experimental tanks at set intervals (6,12,24,48, 96 hrs) and processed. The flesh and the intravalvular fluids were assessed for E. coli, faecal coliforms and intestinal enterococci using the MPN methods mentioned above, while the digestive glands were assessed for somatic coliphages, F-RNA coliphages and bacteriophages infecting B. fragilis GB124 using a standardised double agar-layer method (ISO 10705).…”

“…Several research studies have been undertaken across a variety of geographic areas in recent years to evaluate the presence of microorganisms within shellfish 1,6,13,20,26 . Enteric viruses have been detected in shellfish harvested from areas classified as 'Category A' status according to EU standards 11 , suggesting that the current hygiene classifications for shellfisheries, based on levels of bacterial indicators, may not offer an indication of risk of enteric viral pathogens.…”

“…Again, the high phage density was required to allow for those that would be voided when introduced into the tanks. The time increments and overall duration of bioaccumulation of faecal indicator bacteria and phages in the shellfish matrices were based in part on previous findings 6 , where variations were observed in the bioaccumulation efficiency of viral pathogens in different shellfish species using a maximal theoretical bioaccumulation (MTB) calculation. These authors reported the highest bioaccumulation efficiencies after 1hr in mussels and, after 24 hrs in oysters and flat oysters.…”