Selective Accumulation May Account for Shellfish-Associated Viral Illness

Abstract

From 1991 through 1998, 1,266 cases of shellfish-related illnesses were attributed to Norwalk-like viruses. Seventy-eight percent of these illnesses occurred following consumption of oysters harvested from the Gulf Coast during the months of November through January. This study investigated the ability of eastern oysters (Crassostrea virginica) to accumulate indicator microorganisms (i.e., fecal coliforms, Escherichia coli, Clostridium perfringens, and F ؉ coliphage) from estuarine water. One-week trials over a 1-year period were used to determine if these indicator organisms could provide insight into the seasonal occurrence of these gastrointestinal illnesses. The results demonstrate that oysters preferentially accumulated F ؉ coliphage, an enteric viral surrogate, to their greatest levels from late November through January, with a concentration factor of up to 99-fold. However, similar increases in accumulation of the other indicator microorganisms were not observed. These findings suggest that the seasonal occurrence of shellfish-related illnesses by enteric viruses is, in part, the result of seasonal physiological changes undergone by the oysters that affect their ability to accumulate viral particles from estuarine waters.

Coliform accumulation in Amphibalanus amphitrite (Darwin, 1854) (Cirripedia) and its use as an organic pollution bioindicator in the estuarine area of Recife, Pernambuco, Brazil

“…Kolm and Absher (2008), when comparing the bacterial density in waters and oysters of the Paranaguá estuarine complex, Paraná-Brazil, always found lower TC values in the water than in the oysters during the period sampled. The same was observed by Burkhardt III and Calci (2000), who found TTC concentrations inside the oysters Crassostrea virginica (Gmelin, 1791) from an estuary of the Mexican Gulf as much as 4.4 times than that of the surrounding water. Similarly, Lucena et al (1994) noted that bacterial concentrations of the black mussel Mytilus edulis d`Orbigny, 1846 from the Mediterranean Sea were far greater than bacterial levels in the water, which indicates bioaccumulation.…”

Bacteria of fecal origin in mangrove oysters (Crassostrea rhizophorae) in the Cocó River estuary, Ceará State, Brazil

“…In a study involving oysters (Crassostrea virginica) from an estuary on the coast of the Mexican Gulf, Burkhardt III and Calci (9) found the concentration of fecal coliforms inside the mollusks to be 4.4 times that of the surrounding water. Pommepuy et al (27) explain this fact by suggesting that the cultivability of E. coli and other enterobacteria is better preserved when the microorganisms are ingested by mollusks than when they are exposed to sunlight in a marine environment, a fact which may account for the great differences observed in bacterial counts.…”

Analytical Methods for Virus Detection in Water and Food

“…The majority of accumulated virus is found in the pancreatic tissue, also called the digestive diverticula. Mechanical entrapment and ionic bonding are among the mechanisms that have been suggested to explain observed differences in accumulation of different viruses and among different oyster species (Burkhardt and Calci 2000;Di Girolamo et al 1977). Another potential mechanism for the uptake and concentration of viruses in shellfish has been proposed based upon the observation of specific binding of a NoV genogroup I to shellfish tissues (Le Guyader et al 2006b).…”