Public health consequences of a non-native oyster species introduction in the Chesapeake Bay

In efforts to ameliorate the economic strain experienced by the Chesapeake Bay's commercial oyster industry, the States of Maryland and Virginia are currently considering the introduction of a non-native oyster species, Crassostrea ariakensis into the Chesapeake Bay. Biosecurity trials of the C. ariakensis have already begun and the official introduction will likely occur without a full understanding of all the public health consequences. Gastroenteritis associated with the consumption of contaminated, raw oysters causes worldwide health concerns, but the ability for C. ariakensis to bioaccumulate, retain, or depurate human pathogens has not been fully evaluated.

We evaluated the ability for the native Crassostrea virginica and non-native C. ariakensis to bioaccumulate, retain, and depurate nine pathogens and indicators over various salinity ranges relevant to the Chesapeake Bay. In all experiments, oysters were allowed to bioaccumulate microorganisms for 24 hours; depurated for 29 days; and sampled at weekly time intervals. The non-native C. ariakensis oysters bioaccumulated and retained human pathogens over broad salinity ranges. C. ariakensis were more likely to harbor viruses, protozoa, and microsporidia as compared to C. virginica oysters. Overall depuration was ineffective in the removal of enteric pathogens from the non-native C. ariakensis and human enteric viruses were detected at day 29 of depuration. If C. ariakensis are introduced into the Chesapeake Bay, they will filter human wastes efficiently. Unfortunately, C. ariakensis oysters will predominately be harvested for human consumption, and thus ecological benefits provided by the oyster's filtration efficiency will likely cause harmful repercussions to the health of consumers.