Viruses and Shellfish

While studying the cycle of viral contamination of aqueous media, it appears that the human being is both the primary contaminator and the secondary receiver of the viruses transported in the aqueous medium. Human contamination takes place by drinking water of poor quality, by eating vegetables irrigated with waste water or shellfish. Shellfish consumption is clearly associated with the transmission of enteric infections and epidemics have been reported in many countries. The viruses responsible for the transmission of epidemics are mostly gastro-enteric viruses (Norwalk virus, Rotavirus and “small round viruses”) and the hepatitis A virus. The shellfish implicated are oysters, cockles, mussels and clams. Shellfish depuration techniques involve either closed loop circuits or semi-open circuits. They are very effective bacteriologically, but they do not totally eliminate the viral particles. Furthermore, sanitary controls are, usually, based on the sole research of fecal coliform although this bacterial type is a bad indicator of viral contamination. It is therefore necessary to include a virological criterion in the sanitary control of shellfish.