Enteroviruses and Potential Bacterial Indicators in Gulf Coast Oysters

Abstract

Bacteriological and virological examinations of Louisiana and Texas Gulf Coast oysters were done over a 12-month period. Oysters taken from approved waters sometimes contained detectable enteroviruses: echovirus 4 and poliovirus 1 were in one each of 17 samples from Texas, and poliovirus 3 was in one of 24 samples from Louisiana. Neither the coliform MPN for the water from the shellfish beds nor the coliform MPN, Escherichia coli MPN, or aerobic plate counts for the shellfish meats was clearly indicative of the presence of virus. Two of the 24 oyster meat samples which contatined Vibrio parahaemolyticus also yielded virus; however, virus was present in one of 17 samples in which V. parahaemolyticus was not detected. Poliovirus 1 was also found in frozen, shucked oysters imported from Japan.

Bacteriological indicators of tropical water quality

“…The most widely used indicators are the coliform bacteria-the total coliforms that got narrowed down to the fecal coliforms, and the fecal streptococci. For various reasons, there has been growing dissatisfaction and loss of confidence in the continued use of these two groups of organisms as the conventional indicators of fecal pollution of water (Dutka, 1973;Fugate et al, 1975;WHO, 1980;Colwell, 1978).…”

A 2-year survey of the prevalence of enteric viral infections in children compared with contamination in locally-harvested oysters

“…Viruses have been isolated most commonly from heavily polluted areas closed to shellfish harvesting but have also been detected in some areas approved for shellfish harvesting [8,9]. Our results indicate that uncultivated wild oysters grown on the sea bottom far from the estuary may still be contaminated by prevalent human enteric viruses.…”

“…Recent studies have indicated that the faecal coliform index cannot be relied upon because coliform bacteria are more sensitive to treatment processes or natural inactivation factors than some of the more resistant enteroviruses [3,8,9,18]. The standard plate count is very useful as a highly sensitive indicator of treatment deficiencies and secondary contamination, and is most valuable for monitoring disinfection processes because it covers a variety of bacterial spores which are more resistant than any known viruses [18].…”

“…In Japan, small round virus infections have been reported in several oyster-associated gastroenteritis outbreaks [7]. It has been suggested that bacteriological indicators such as standard plate counts and coliform indices may be poor indicators of the level of viral contamination [3,8,9]. However, these procedures are still being used to set national standards of microbial safety in oysters because other, more sensitive or simple methods for recovery of enteric virus have not been developed.…”

Public health considerations associated with molluscan aquaculture systems: Human viruses

“…The occurrence of human viruses in shellfish species residing in light to moderately polluted marine waters is well documented (Morris et al, 1976;Vaughn and Metcalf, 1975;Metcalf and Stiles, 1967;Gerba and Goyal, 1978). Studies have also documented the recovery of viruses from animals residing in waters which had been certified as safe for shellfish harvesting (Fugate et al, 1975;Vaughn et al, 1980;Goyal et al, 1979). Origins of pollution identified during these studies have ranged from continuous point sources such as ocean outfalls and the outlets of sewage-polluted freshwater systems, to sources of a more sporadic 0044-84a~/84~$03.00 0 1984 Elsevier Science Publishers B.V. nature [i.e., runoff during periods of heavy rain and flooding, areas under heavy recreational (swimming, boating) use].…”