Risks Associated with Fish and Seafood

Fresh fish and seafood are highly perishable, and microbiological spoilage is one of the important factors that limit their shelf life and safety. Fresh seafood can be contaminated at any point from rearing or harvesting to processing to transport or due to cross-contamination by consumer mishandling at home. With the increase in the demand for fish and seafood, aquaculture production is increasing, which could lead to new risks that will need to be addressed in the future to control foodborne pathogens.

Detection of pathogenic bacteria in shellfish using multiplex PCR followed by CovaLink NH microwell plate sandwich hybridization

Outbreak of diseases associated with consumption of raw shellfish especially oysters is a major concern to the seafood industry and public health agencies. A multiplex PCR amplification of targeted gene segments followed by DNA-DNA sandwich hybridization was optimized to detect the etiologic agents. First, a multiplex PCR amplification of hns, spvB, vvh, ctx and tl was developed enabling simultaneous detection of total Salmonella enterica serotype Typhimurium, Vibrio vulnificus, Vibrio cholerae and Vibrio parahaemolyticus from both pure cultures and seeded oysters. Amplicons were then subjected to a colorimetric CovaLink NH microwell plate sandwich hybridization using phosphorylated and biotinlylated oligonucleotide probes, the nucleotide sequences of which were located internal to the amplified DNA. The results from the hybridization with the multiplexed PCR amplified DNA exhibited a high signal/noise ratio ranging between 14.1 and 43.2 measured at 405 nm wavelength. The sensitivity of detection for each pathogen was 10(2) cells/g of oyster tissue homogenate. The results from this study showed that the combination of the multiplex PCR with a colorimetric microwell plate sandwich hybridization assay permits a specific, sensitive, and reproducible system for the detection of the microbial pathogens in shellfish, thereby improving the microbiological safety of shellfish to consumers.

Infectious outbreaks associated with bivalve shellfish consumption: a worldwide perspective

Outbreaks of shellfish-associated infection have been reported for more than a century. Since the early 1970s, the global consumption of shellfish has increased considerably--and with it, the reports of outbreaks of infection. Most of these reports have originated from the United States, but Europe and, to a lesser extent, Asia and Australia have also been represented. The majority of outbreaks have been linked to oysters, followed by clams and mussels. Hepatitis A virus caused the largest ever shellfish-associated outbreak, but caliciviruses have caused the highest number of outbreaks; Vibrio species lead the list of bacterial pathogens. The prognosis of shellfish-associated infections is generally good, except for outbreaks of Vibrio vulnificus infection, which have a mortality rate of up to 50% in vulnerable people. Conventional and molecular techniques should be applied to better identify the causative agents, thereby enabling more-targeted control measures in growing, harvesting, and shipping bivalves.

An elective rotation in applied epidemiology with the Centers for Disease Control and Prevention (CDC), 1975-1997

INTRODUCTION

To increase awareness of and interest in public health and epidemiology, CDC initiated an elective in epidemiology and public health for senior medical students in 1975 and for veterinary students in 1982.

METHODS

A review of CDC records to describe participation in the elective, to assess whether students subsequently enrolled in another CDC training program, the Epidemic Intelligence Service (EIS), and, if enrolled, employment status following EIS. A review of documentation of board certification in preventive medicine to determine how many participants later chose this specialty, one indicator of public health and prevention as a career choice.

RESULTS

From 1975 through 1997, 632 students participated in the elective. Of these, 438 (69%) were assigned to infectious disease areas, 95 (15%) to environmental health, 59 (9%) to chronic disease, and 40 (7%) to other areas. Students participated in at least 278 official investigations of important public health problems including infectious disease outbreaks, natural disasters, chronic disease problems and access to health care. Of 530 students who had completed the elective through June 1995, 91 (17%) were enrolled in EIS by July 1997. Of 83 completing EIS by July 1997, 65 (78%) had continued in public health careers: 35 with CDC; 17 with local or state health departments; 7 with other federal agencies; 4 in academic public health; and 2 in international health. Of those not enrolling in EIS, at least 5% were certified by the American Board of Preventive Medicine, compared with 34% of those completing EIS.

CONCLUSION

An elective rotation in public health and applied epidemiology is valuable in introducing future physicians and veterinarians to the practice of public health, and can provide important role models for encouragement to pursue careers in public health.