HAZARDOUS ANALYSIS AND CRITICAL POINT PLAN DEVELOPMENT FOR CONTROL OF VIBRIOS AND CRYPTOSPORIDIUM IN RAW OYSTERS
Abstract:V. parahemolyticus and V. vulnificus are the two main microbial agents associated with illness following raw oyster ingestion or contact with raw oyster. Recently, investigation of raw oysters from Chesapeake Bay isolated CRYPTOSPORIDIUM oocysts from hemocytes, on gills and within the body of the oysters. Those oocysts residing in oyster tissues for 1 week were still infectious to mice. Although it is not known if this occurs in the natural environment, the study suggests the possibility that oysters grown in waters contaminated with Cryptosporidium parvum oocysts pose a threat of infection in raw oysters.
Louisiana oysters may be the source of infection of a large portion of infections because oyster harvesting is a primary industry in Louisiana. The economic loss and potential liability if oysters harvested in Louisiana are indicated in disease, infection or death could be substantial. The Gulf oyster industry can avert the potential loss of jobs and revenues if Louisiana oysters are known to be pure, safe and marketable.
The Center for Science in the Public Interest (CSPI) and the Interstate Shellfish Sanitation Conference (ISSC) approached the problem by petitioning the United States Food and Drug Administration to adopt a performance standard of non-detectable levels of Vibrio vulnificus. The standard would be applied for raw molluscan shellfish harvested from waters that have been linked to illnesses or deaths. However, the frequency of eating raw oysters and the true incidence of illness following raw oyster ingestion or contact with raw oyster are not known. An understanding of the true incidence and infectivity of Vibrio and CRYPTOSPORIDIUM from raw oysters may support implementation of alternative methods for infection control. Such alternatives include development of a HACCP that allows the control and management of oyster harvesting, transport, packaging and consumption to reduce the potential of infection and use of alternative technologies for disinfection of oysters prior to consumption. An important outcome would be the development of state policy based on the assessment of risk.
Health effects assessment is a process whereby the magnitude of a specific risk is characterized so that decision-makers can conclude whether the potential hazard is sufficiently great that it needs to be managed or regulated. We have chosen this method in conjunction with a Health Risk Assessment to collect the necessary data for HACCP plan and policy development, to predict the exposure of various populations and estimate the magnitude of health risk.
The health effects assessment will investigate the influence of the abiotic environment, including salinity, temperature, agricultural and urban impact on Vibrio and CRYPTOSPORIDIUM densities. It is thought that changes in the environmental characteristics of oyster growing water may be related to the density of Vibrio species in such waters. For example, the salinity in the Gulf and estuarine waters of South Louisiana has increased subsequent to the channelization of the Mississippi River and the Mississippi Gulf Outlet. The increase in salinity has caused the waters in the estuaries and bays to increase in temperature (the specific heat of water goes down with increasing salinity) which may impact the densities of Vibrio vulnificus in the oyster beds in South Louisiana and Texas. In addition, contamination in this region from non-points source urban, rural and agricultural runoff can increase the nutrient and microbial levels in basins such as the Lake Pontchartrain Basin.
The study will use hospital-collected data to obtain information on the prevalence of illness in Louisiana, wherever possible taking into account various risk factors. We will further attempt to ascertain the degree of under-reporting, if any, of Vibrio-induced illnesses in the State. We will assess to what extent it is possible to link detected cases to environmental data.
Document Type: Research Article
Publication date: January 1, 2000
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