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PubMed1971

Accumulation and elimination of coliphage S-13 by the hard clam, Mercenaria mercenaria.

Accumulation and elimination of viral particles by hard clams, Mercenaria mercenaria, were studied with the coliphage S-13 as a working model. Escherichia coli uptake and elimination were simultaneously monitored. Clams were exposed to low levels of S-13 (7 particles/ml) in running seawater for several days, achieving titers in tissues from 2 to more than 1,000 times the levels to which they had been exposed. Bacterial accumulation (previously established by other workers) was comparable. Upon exposure to virus-free running water, clams polluted to relatively low levels (100 plaque-forming units/ml) eliminated most of their bacterial contaminants in 24 to 48 hr. Viral contaminants, however, persisted for several days to weeks even under ideal conditions for clam activity, provided that the temperature remained below the inactivation threshold for the virus. Most of the accumulated virus appeared to be sequestered in the digestive gland. These sequestered particles are refractory to those mechanisms responsible for elimination of bacterial contaminants. This discrepancy points out the need for caution in evaluating the efficiency of shellfish depuration processes, especially if only a bacterial criterion is used as a monitoring system.

Coliphages↗

PubMed2002

Organic mercury compounds: human exposure and its relevance to public health.

Humans may be exposed to organic forms of mercury by either inhalation, oral, or dermal routes, and the effects of such exposure depend upon both the type of mercury to which exposed and the magnitude of the exposure. In general, the effects of exposure to organic mercury are primarily neurologic, while a host of other organ systems may also be involved, including gastrointestinal, respiratory, hepatic, immune, dermal, and renal. While the primary source of exposure to organic mercury for most populations is the consumption of methylmercury-contaminated fish and shellfish, there are a number of other organomercurials to which humans might be exposed. The antibacterial and antifungal properties of organomercurials have resulted in their long use as topical disinfectants (thimerosal and merbromin) and preservatives in medical preparations (thimerosal) and grain products (both methyl and ethyl mercurials). Phenylmercury has been used in the past in paints, and dialkyl mercurials are still used in some industrial processes and in the calibration of certain analytical laboratory equipment. The effects of exposure to different organic mercurials by different routes of exposure are summarized in this article.

Animals↗

PubMed2003

Diet and lung cancer risk from a 14-year population-based prospective study in Japan: with special reference to fish consumption.

N-3 polyunsaturated fatty acids in fish oil exhibit a variety of health benefits, and there is evidence that they can inhibit the development of human lung mucoepidermoid and other carcinomas. To examine the hypothesis that fish consumption reduces the risk of lung cancer, we conducted a population-based prospective study, following 5,885 residents for 14 yr. Person-years were used to calculate the relative risk (RR) by the Cox proportional hazards model, with adjustment for potential confounding factors. A total of 51 incident lung cancer cases were observed, and we found linearly decreasing RRs for lung cancer with increased frequency of consumption of fish and shellfish (RRs = 1.00, 0.99, and 0.32, P for trend = 0.003) but not with intake of dried/salted fish. Decreased RRs were apparent with both broiling and boiling cooking methods, but reduction with raw and deep-fried fish consumption was not statistically significant. We conclude that frequent fresh fish consumption, irrespective of the cooking method, may reduce the risk of lung cancer.

Animals↗

PubMed2000

Food anaphylaxis.

Food anaphylaxis is now the leading single cause of anaphylactic reactions treated in emergency departments in Westernized countries. In the US, it is estimated that there are 29,000 anaphylactic reactions to foods treated in emergency departments and 125-150 deaths each year. Peanuts, tree nuts, fish and shellfish account for the vast majority of severe food anaphylactic reactions. Immunopathogenic mechanisms responsible for food anaphylaxis may differ somewhat from other forms of anaphylaxis, since elevation of serum tryptase is rarely seen following food anaphylactic reactions. Education regarding the strict avoidance of food allergens, the early recognition of anaphylactic symptoms, and the early use of self-injectable epinephrine remain the mainstays of therapy. However, clinical trials are now underway for the treatment of patients with peanut anaphylaxis utilizing anti-IgE antibody therapy and novel immunomodulatory therapies utilizing 'engineered' recombinant proteins, overlapping peptides, and immunostimulatory deoxyoligonucleotide sequences are being tested in animal models of anaphylaxis.

Acute Disease↗

PubMed2000

Marine algal toxins: origins, health effects, and their increased occurrence.

Certain marine algae produce potent toxins that impact human health through the consumption of contaminated shellfish and finfish and through water or aerosol exposure. Over the past three decades, the frequency and global distribution of toxic algal incidents appear to have increased, and human intoxications from novel algal sources have occurred. This increase is of particular concern, since it parallels recent evidence of large-scale ecologic disturbances that coincide with trends in global warming. The extent to which human activities have contributed to their increase therefore comes into question. This review summarizes the origins and health effects of marine algal toxins, as well as changes in their current global distribution, and examines possible causes for the recent increase in their occurrence.

Animals↗

PubMed1998

Detection of Listeria monocytogenes in humans, animals and foods.

The Listeria monocytogenes-carrying rates were 100% for listeriosis patients and 1.3% for healthy humans. The L. monocytogenes contamination rates for retail sliced beef (34.2%) and pork (36.4%) were significantly higher (p < 0.05) than those for cattle (2.0%) and pigs (0.8%) and for cattle (4.9%) and swine (7.4%) carcasses. The percentages of serotypes 1/2a, 1/2b and 4b which are most dominant in human patients were high in isolates from fresh (90.0%) and processed (100%) fish and shellfish and imported natural cheese (96.7%).

Adolescent↗

PubMed2003

Comparison between specific and multiplex reverse transcription-polymerase chain reaction for detection of hepatitis A virus, poliovirus and rotavirus in experimentally seeded oysters.

Outbreaks of gastroenteritis have occurred among consumers of raw or undercooked shellfish harvested from faecally polluted waters. A multiplex reverse transcription-polymerase chain reaction (RT-PCR) was applied for the simultaneous detection of hepatitis A virus (HAV), poliovirus (PV) and simian rotavirus (RV-SA11) and compared with specific primers for each genome sequence. Three amplified DNA products representing HAV (192 bp), PV (394 bp) and RV (278 bp) were identified when positive controls were used. However, when tested on experimentally contaminated raw oysters, this method was not able to detect the three viruses simultaneously. This is probably due to the low concentration of viral RNAs present in oyster extract which were partially lost during the extracts preparation.

Animals↗

PubMed1996

International trade in live molluscs: perspective from the Americas.

There is an active world trade in seed and edible molluscs, including such species as oysters, abalones, clams, scallops, and mussels. The supply of new and effectively-produced products, such as triploid oyster seed, is likely to increase due to greater world-wide demand for these high-value products, together with improved technology. Transfer to live molluscs is driven by need an availability, with concern over infectious disease risks often playing subordinate role or serving to support economic trade barriers. Experience shows that serious risks from infectious disease transfer exist. Technology and balanced management, however, can limit such risks. Separation of biological risks from trade control objectives is a necessary first step. A systematic method of risk analysis is urgently needed, along with predefined actions which can be adapted to the various risk levels. Critical to the effective development and implementation of this risk analysis is the participation of the shellfish industry in defining risks and actions. Organization and infrastructure to improve recognition of infectious diseases and decrease response time are necessary improvements, together with appropriately-targeted research on impacts, diagnosis, epidemiology, carrier status, and geographical distribution of diseases.

Animals↗

PubMed1997

Public health issues in aquaculture.

The authors address the public health issues associated with the consumption of aquacultural products using numerous examples from the United States of America. As with other foods, public health risks exist but these mostly involve open water environments or products which are consumed raw or undercooked. Unlike wild fisheries, inland aquaculture systems can minimise public health risks by proper site evaluation and good aquacultural practices. Responsible use of pesticides and therapeutants can prevent violative residues to assure product safety and wholesomeness. The implementation of hazard analysis and critical control point regulations will further enhance the preventive approach to hazards control. The most challenging public health risks arise from shellfish production in open, surface waters, where both naturally-occurring and trace environmental residue contaminants can bioaccumulate in tissues and may cause disease outbreaks (and, in severe cases, death). Water quality certification programmes and field surveillance efforts including product sampling, testing and monitoring can address critical safety criteria. This paper focuses primarily on public health risks associated with production: however, the fact that consumer risks also occur as a result of the processing of aquacultural products and that foodborne diseases arise additionally from unsanitary handling or preparation and storage at incorrect temperatures (as is the case for food products from other animals) must also be taken into consideration.

Animals↗

PubMed1979

Failure of indicator bacteria to reflect the occurrence of enteroviruses in marine waters.

The results of several studies conducted along the upper Texas Gulf coast, where a substantial amount of quantitative virological data were collected, are compared to bacteriological indicators and other environmental factors on a statistical basis. Variables common to all these studies were anlayzed by multivariate regression. Although multivariate analysis indicated that the number of viruses detected in water was related to rainfall, salinity, and total coliforms in the water, the amount of variation in the number of viruses accounted for by these factors was not large enough to make them good predictors. Enteroviruses were detected 43 per cent of the time in recreational waters considered acceptable as judged by coliform standards, and 44 per cent of the time when judged by fecal coliform standards. Enteroviruses were detected 35 per cent of the time in waters which met acceptable standards for shellfish-harvesting. Our failure to correlate the occurrence of enteroviruses in marine waters with indicator bacteria, and the frequent occurrence of enteroviruses in water which met current bacteriological standards, indicates that these standards do not reflect the occurrence of enteroviruses, and perhaps other human pathogenic viruses, in marine waters.

Animals↗

PubMed1994

Risk factors for acute non-A, non-B hepatitis and their relationship to antibodies for hepatitis C virus: a case-control study.

A case-control study was carried out comparing 333 case subjects with non-A, non-B hepatitis and 1095 hospital control subjects. Of 333 case subjects, 197 (59%) were positive for hepatitis C antibody (anti-HCV). Excluding blood transfusion and intravenous drug use, surgical intervention and dental therapy were strongly associated with anti-HCV-positive cases: in particular, obstetric and gynecology surgical intervention was found to be strongly associated with HCV positivity (odds ratio [OR] = 32; 95% confidence interval [CI] = 7, 147). Raw shellfish consumption was a risk factor for anti-HCV-negative cases (OR = 2.2; 95% CI = 1.0, 5.1), thus suggesting an enterically transmitted virus in sporadic non-A, non-B hepatitis in Italy.

Acute Disease↗

PubMed1997

An outbreak of Norwalk virus gastroenteritis following consumption of oysters.

In August 1996, an outbreak of Norwalk virus gastroenteritis occurred among south-east Queensland and northern New South Wales residents over a four week period. Ninety-two of the 97 cases detected were confirmed as having consumed raw oysters within three days prior to developing the illness. No other food items or beverages were significantly associated with the illness. Environmental investigations indicated the Terranora Broadwater, Tweed Heads as the origin of the contaminated oysters. However, the primary source of Norwalk virus could not be verified. Oysters and other shellfish appear to be a common vehicle for transmission of this virus. This outbreak and the more recent hepatitis A outbreak associated with Wallis Lake oysters, highlight the susceptibility of oysters to environmental contamination and the urgent need for stricter quality control procedures. This report details the epidemiological, microbiological and environmental findings from an outbreak investigation conducted jointly by the Queensland and New South Wales health authorities.

Adolescent↗

PubMed2004

Common whelk (Buccinum undatum) allergy: identification of IgE-binding components and effects of heating and digestive enzymes.

In Korea, common whelk (Buccinum undatum) is a popular edible shellfish. The aim of this study was to observe the sensitization rate to common whelk and to characterize its allergens. We carried out skin prick test (SPT) in 1,700 patients with various allergic diseases. Specific IgE were detected by ELISA in the patient sera and ELISA inhibition tests were conducted. IgE-binding components were identified by means of SDS-PAGE and IgE-immunoblotting. The effects of digestive enzymes were evaluated in both raw and thermally treated extracts. SPT to common whelk was positive (>/=2+) in 83 (4.9%) patients studied. Twenty-four (38.7%) out of 62 SPT positive patients had high serum specific IgE to common whelk. ELISA inhibition test showed significant inhibitions by abalone as well as by common whelk. IgE-immunoblotting demonstrated three IgE-binding components (40, 71, 82 kDa), which were digested by simulated intestinal fluid and moderately digested by simulated gastric fluid, and the digestibility of allergens remained unchanged after thermal treatment. In conclusion, IgE-sensitization rate to common whelk was 4.9% in allergy patients. IgE-immunoblotting demonstrated three IgE-binding components, which were degraded by digestive enzymes. Further studies are needed to evaluate the clinical significance of the sensitized patients to common whelk.

Allergens↗

PubMed2002

Detection of Campylobacter jejuni and Campylobacter coli in foods by enrichment culture and polymerase chain reaction enzyme-linked immunosorbent assay.

A polymerase chain reaction (PCR) assay based on a solution hybridization format with colorimetric end-point detection (PCR ELISA) was investigated for the specific detection of Campylobacter jejuni and Campylobacter coli in food samples following enrichment culture. One hundred fifteen samples of raw meat and offal (poultry, porcine, ovine, and bovine), raw shellfish, and artificially contaminated milk were enriched in blood-free Campylobacter Enrichment Broth for 48 h. Enrichment cultures were subcultured to Campylobacter blood-free selective agar plates, and presumptive isolates were identified by phenotypic methods. DNA was extracted from 1-ml aliquots of the enrichment cultures using a rapid extraction method, and the DNA was used as the template in a PCR ELISA. A comparison of the PCR ELISA with the enrichment culture and subculture to selective agar method showed that the results of 112 of the 115 samples tested were in agreement by both methods. Seventy-one of the various food samples were positive in the PCR ELISA, and 70 samples were positive by culture. The PCR ELISA had a sensitivity of 99% and a specificity of 96%, with a positive predictive value of 97% and a negative predictive value of 98%. The PCR ELISA is a rapid, sensitive, and specific method for the detection of C. jejuni and C. coli in foods following enrichment culture and significantly reduces the time required for their detection.

Animals↗

PubMed2003

Modification of an approved medium for fecal coliform detection in seawater: A-1 medium minus salicin.

Four hundred fifteen shellfish seawater samples from approved, conditionally approved, and restricted areas along the coastlines of Connecticut, Massachusetts, and Maine were tested in duplicate to compare results obtained with A-1 medium (AOAC official method no. 978.23) and those obtained with A-1 medium without salicin. Four laboratories used five sets of most probable number procedures to perform the analyses. No statistically significant differences between the two media were found with the t test, the F test, or the analysis of variance.

Animals↗

PubMed2003

Sensitivity of Vibrio species in phosphate-buffered saline and in oysters to high-pressure processing.

Multiple strains of Vibrio vulnificus, Vibrio parahaemolyticus, and Vibrio cholerae non-O1 were tested in phosphate-buffered saline for their sensitivity to high-pressure processing (HPP). Variability in sensitivity among strains was observed for all species; this variability decreased at higher pressures. V. vulnificus was the species that was most sensitive to treatment at 200 MPa (decimal reduction time [D] = 26 s), and V. cholerae was the species that was most resistant to treatment at 200 MPa (D = 149 s). The O3:K6 serotype of V. parahaemolyticus was more resistant to pressure than other serotypes of V. parahaemolyticus were. The results of studies involving V. vulnificus naturally occurring in oysters revealed that a pressure treatment of 250 MPa for 120 s achieved a > 5-log reduction in the levels of this bacterium. V. parahaemolyticus serotype O3:K6 in oysters required a pressure of 300 MPa for 180 s for a comparable 5-log reduction. When properly applied, HPP can be effective in improving the safety of shellfish with respect to Vibrio spp.

Animals↗

PubMed2004

Survival and persistence of norovirus, hepatitis A virus, and feline calicivirus in marinated mussels.

Noroviruses (NV) and hepatitis A virus (HAV) are foodborne enteric viruses associated with outbreaks of disease following consumption of raw or lightly cooked bivalve shellfish. Marinated mussels are a popular delicacy, but there is no published information on whether enteric viruses survive the marination process. The survival and persistence of HAV, NV, and a surrogate calicivirus, feline calicivirus (FCV), in marinated mussels over time was determined. NV, HAV, and FCV were inoculated into marinated mussels and marinade liquid and then held at 4 degrees C for up to 4 weeks. Survival of HAV and FCV was quantified by determining the 50% tissue culture infectious dose (TCID50), and these results were correlated with those of the reverse transcription (RT)-PCR assay. The persistence of nonculturable NV was determined by RT-PCR assay only. Over 4 weeks, HAV survived exposure to acid marinade at pH 3.75. There was a 1.7-log reduction in HAV TCID50 titer but no reduction in NV or HAV RT-PCR titer after 4 weeks in marinated mussels. FCV was inactivated in acid conditions although it was still detectable by RT-PCR. To simulate preharvest virus contamination and commercial marination processing, experiments using fresh mussels infected with HAV and NV were performed. HAV and NV persistence was determined using semiquantitative real-time RT-PCR, and HAV infectivity was determined by the TCID50 assay. HAV retained infectivity following simulated commercial marination and exposure to acid conditions over 4 weeks. The survival of pathogenic enteric viruses in marinated mussels constitutes a potential health risk and so is of concern to public health authorities.

Animals↗

PubMed2005

Ice immersion as a postharvest treatment of oysters for the reduction of Vibrio vulnificus.

Vibrio vulnificus produces serious illnesses that are commonly associated with shellfish consumption, particularly raw oysters. Ingestion can result in fatal septicemia in susceptible individuals with hepatitis, cirrhosis, immune dysfunction, diabetes, or hemochromatosis (metabolic iron overload). Therefore, postharvest treatments to reduce vibrio levels in oysters have been recommended. In this study, rapid chilling by immersion of unwashed whole oysters in ice for 3 h was assessed as a postharvest treatment for reduction of V. vulnificus. Treated oysters were subsequently refrigerated at 45 degrees F (7.2 degrees C), whereas control oysters were not iced but were maintained at 45 degrees F throughout the study. Homogenized meats were monitored for total heterotrophic aerobic bacteria, V. vulnificus, and fecal coliform content before and after treatment over a 2-week period. V. vulnificus was enumerated by DNA probe hybridization of colonies from standard plate counts on nonselective medium, and recovery was compared for several media. Loss of plating efficiency was observed on standard selective and differential media compared with nonselective agars. Numbers of V. vulnificus generally declined in treated samples compared with controls; however, increases in total heterotrophic bacteria and fecal coliforms were also observed in treated samples at some time points. This study does not support the use of ice immersion as a postharvest method because of the relatively small declines in V. vulnificus numbers and the possibility of concomitant increases in fecal coliform and total bacterial contamination.

Animals↗