Moluscos

APPLIED AND ENVIRONMENTAL MICROBIOLOGY, Mar. 1979, p. 572-581 0099-2240/79/03/0572-10$02.00/0

Vol. 37, No. 3

Human Enteroviruses in Oysters and Their Overlying Waters
SAGAR M. GOYAL,* CHARLES P. GERBA, AND JOSEPH L. MELNICK Department of Virology and Epidemiology, Baylor College ofMedicine, Houston, Texas 77030 Received for publication 10 December 1978

The presence of enteroviruses inoysters and oyster-harvesting waters of the Texas Gulf coast was monitored over a period of 10 months. Viruses were detected in water and oyster samples obtained from areas both open and closed to shellfish harvesting. Viruses were detected periodically in waters that met current bacteriological standards for shellfish harvesting. No significant statistical relationship was demonstrated betweenvirus concentration in oysters and the bacteriological and physicochemical quality of water and shellfish. Viruses in water were, however, moderately correlated with total coliforms in water and oysters and with fecal coliforms in oysters. Total coliforms in water were related to total coliforms and fecal coliforms in oysters and to fecal coliforms in water. Fecal coliforms in sediment were relatedonly to total coliforms in sediment. Among the physicochemical characteristics of water, turbidity was related statistically to the organic matter content of water and to fecal coliforms in water. There was a marked effect of rainfall on the bacteriological quality of water. Of a total of 44 water samples, 26 yielded virus in concentrations from 4 to 167 plaque-forming units per 100-gallon (ca.378.5-liter) sample. Of a total of 40 pools of 10 to 12 oysters each, virus was found in 14 pools at a concentration of 6 to 224 plaqueforming units per 100 g of oyster meat. On five occasions, virus was found in oysters but not in the overlying water. Similarly, viruses were isolated from 17 water samples when no virus could be detected in oysters harvested from the same sites. This study indicatesthat current bacteriological standards for determining the safety of shellfish and shellfish-growing waters do not reflect the occurrence of enteroviruses.
The coastal areas of any nation are a vital niques for their study. Documented outbreaks recreational resource and food source. This val- of hepatitis have been attributed to the conuable resource, however, is lost when humans sumption ofshellfish, which emphasizes both overload the natural self-purification system the need for definitive information on virus polwith their wastes. Viruses usually occur in do- lution of coastal waters and shellfish and the mestic sewage and survive in some numbers inadequacy of present bacteriological criteria for even after secondary treatment (17). They can the sanitary quality of shellfish andshellfishalso survive in seawater for a few days to several harvesting waters. weeks (32). By virtue of their ability to concenEven in nonepidemic periods, there is a relatrate viruses and bacteria, shellfish such as oys- tionship between the consumption of shellfish ters, mussels, and clams may become actively and the occurrence of hospitalized cases of infeccontaminated even at considerable distancestious hepatitis (24). It would seem that the true from the point of sewage discharge. Because incidence of shellfish-associated viral diseases is these species are often eaten raw or lightly greatly underestimated (18). In addition, resicooked along with their gastrointestinal tract, dents of coastal states seem to have a higher the risk of illness after their consumption may incidence ofinfectious hepatitis (6). The prebe high. dominantly occult nature of other waterborne Effective control of enteric bacterial disease viruses has made it difficult to document their spread by shellfish has resulted from the estab- transmission by shellfish, but their occurrence lishment of bacteriological standards by using in shellfish is well documented (12, 35, 42) and total coliform and fecal...