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PubMed2005

Fish and shellfish allergy.

Fish and shellfish are important in the American diet and economy. Nearly $27 billion are spent each year in the United States on seafood products. Fish and shellfish are also important causes of food hypersensitivity. In fact, shellfish constitute the number one cause of food allergy in the American adult. During the past decade, much has been learned about allergens in fish and shellfish. The major allergens responsible for cross-reactivity among distinct species of fish and amphibians are parvalbumins. The major shellfish allergen has been identified as tropomyosin. Many new and important potential cross-reacting allergens have been identified within the fish family and between shellfish, arachnids, and insects. Extensive research is currently underway for the development of safer and more effective methods for the diagnosis and management of fish and shellfish hypersensitivity.

Allergens↗
PubMed1982

The effect of shellfish in the diet upon the plasma lipid levels in humans.

In order to document any hypercholesterolemic effects from the ingestion of shellfish, 6 normal men were given two diets containing different shellfish, each preceded by a low cholesterol baseline diet. Diet I contained 449 mg cholesterol per day from lobster, crab, and shrimp. Diet II contained clam, oyster, and scallop and provided 447 mg of sterols of which cholesterol constituted only 40 percent. The other sterols are uniquely characteristic of these shellfish (i.e. brassicasterol, 24-methylene cholesterol, etc.). In a second study, 2 normal men and 1 type II hypercholesterolemic woman were fed the baseline diet and shellfish diet II to provide 623 mg of sterols per day. The plasma cholesterol of the 6 subjects averaged 184 +/- 35 mg/dl during baseline, 192 +/- 35 mg/dl in shellfish diet I (p less than 0.05) and 182 +/- 24 mg/dl during shellfish diet II. In the second study, the plasma cholesterol of the 2 normal men did not change. The cholesterol of the hypercholesterolemic woman increased from 311 mg/dl (baseline) to 352 during the shellfish diet (p less than 0.05). Plasma triglyceride levels remained unchanged. Our data indicated that large quantities of lobster, crab, and shrimp were only mildly hypercholesterolemic in normals, but less so than other cholesterol-containing foods. Clams, oysters, and scallops were not hypercholesterolemic in normal subjects but were in a hypercholesterolemic patient.

Adult↗
PubMed2003

Comparative analysis of viral pathogens and potential indicators in shellfish.

Shellfish can be responsible of outbreaks of infectious diseases and current health measures do not guarantee the absence of viral pathogens in this product. Here we examine the presence of pathogenic viruses and potential indicators in shellfish in a comparative analysis.Sixty shellfish samples collected in three areas with different levels of faecal contamination were analysed for Escherichia coli, total coliforms, Clostridium perfringens, somatic coliphages, F-specific phages of RNA (F-RNA), bacteriophages infecting Bacteroides fragilis RYC2056, human adenovirus, enterovirus and hepatitis A virus (HAV). Viruses were eluted in a glycine buffer at pH 10. The overall percentage of viral pathogens detected was 47% for human adenoviruses, 19% for enteroviruses and 24% for HAV. Since all the samples positive for enterovirus and HAV were also positives for human adenovirus, the latter may be considered useful as a molecular index of viral contamination in shellfish. No significant differences in the bioaccumulation of bacteria and bacteriophages for oysters or mussels were observed. It was found that the probability of detection of any of the pathogenic virus decreases as the temperature of shellfish growing waters increases. However, the probability of detecting viruses increases when phages of B. fragilis are found. Although more data are needed in order to fulfil the need of viral indicators for controlling the presence of human viruses in shellfish, the obtained results indicate that phages infecting B. fragilis RYC2056 could be a suitable group of bacteriophages to be used as an indicator of the presence of viruses in shellfish.

Adenoviruses, Human↗
PubMed2004

Azaspiracid poisoning, the food-borne illness associated with shellfish consumption.

Azaspiracid poisoning (AZP) is a recently discovered toxic syndrome that was identified following severe gastrointestinal illness from the consumption of contaminated mussels (Mytilus edulis). The implicated toxins, azaspiracids, are polyethers with unprecedented structural features. Studies toward total toxin synthesis revealed that the initial published structures were incorrect and they have now been revised. These toxins accumulate in bivalve molluscs that feed on toxic microalgae of the genus Protoperidinium, previously considered to be toxicologically benign. Although first identified in shellfish from Ireland, azaspiracid contamination of several types of bivalve shellfish species has now been confirmed throughout the western coastline of Europe. Toxicological studies have indicated that azaspiracids can induce widespread organ damage in mice and that they are probably more dangerous than previously known classes of shellfish toxins. The exclusive reliance on live animal bioassays to monitor azaspiracids in shellfish failed to prevent human intoxications. This was a consequence of poor sensitivity of the assay and the fact that azaspiracids are not exclusively found in the shellfish digestive glands used for toxin testing. The strict regulatory control of azaspiracids in shellfish now requires frequent testing of shellfish using highly specific and sensitive methods involving liquid chromatography-mass spectrometry.

Animals↗
PubMed2000

Evaluation of F-specific RNA bacteriophage as a candidate human enteric virus indicator for bivalve molluscan shellfish.

Escherichia coli is a widely utilized indicator of the sanitary quality of bivalve molluscan shellfish sold for human consumption. However, it is now well documented that shellfish that meet the E. coli standards for human consumption may contain human enteric viruses that cause gastroenteritis and hepatitis. In this study we investigated using F-specific RNA bacteriophage (FRNA bacteriophage) to indicate the likely presence of such viruses in shellfish sold for consumption. FRNA bacteriophage and E. coli levels were determined over a 2-year period for oysters (Crassostrea gigas) harvested from four commercial sites chosen to represent various degrees of sewage pollution. Three sites were classified as category B sites under the relevant European Community (EC) Directive (91/492), which required purification (depuration) of oysters from these sites before sale. One site was classified as a category A site, and oysters from this site could be sold directly without further processing. Samples were tested at the point of sale following commercial processing and packaging. All of the shellfish complied with the mandatory EC E. coli standard (less than 230 per 100 g of shellfish flesh), and the levels of contamination for more than 90% of the shellfish were at or below the level of sensitivity of the assay (20 E. coli MPN per 100 g), which indicated good quality based on this criterion. In contrast, FRNA bacteriophage were frequently detected at levels that exceeded 1,000 PFU per 100 g. High levels of FRNA bacteriophage contamination were strongly associated with harvest area fecal pollution and with shellfish-associated disease outbreaks. Interestingly, FRNA bacteriophage contamination exhibited a marked seasonal trend that was consistent with the trend of oyster-associated gastroenteritis in the United Kingdom. The correlation between FRNA bacteriophage contamination and health risk was investigated further by using a reverse transcription-PCR assay for Norwalk-like virus (NLV). NLV contamination of oysters was detected only at the most polluted site and also exhibited a seasonal trend that was consistent with the trend of FRNA bacteriophage contamination and with the incidence of disease. The results of this study suggest that FRNA bacteriophage could be used as viral indicators for market-ready oysters.

Animals↗
PubMed2002

Density of total and pathogenic (tdh+) Vibrio parahaemolyticus in Atlantic and Gulf coast molluscan shellfish at harvest.

The densities of total and pathogenic Vibrio parahaemolyticus in 671 samples of molluscan shellfish harvested in 1999 and 2000 from 14 sites in seven Gulf and Atlantic coast states were determined at 2-week intervals over a period of 12 to 16 months in each state. Changes in V. parahaemolyticus densities in shellfish between harvest and sample analysis were minimized with time and temperature controls. Densities were measured by direct plating techniques, and gene probes were used for identification. Total and pathogenic V. parahaemolyticus organisms were identified with probes for the thermolabile direct hemolysin (tlh) gene and the thermostable direct hemolysin (tdh) gene, respectively. An enrichment procedure involving 25 g of shellfish was also used for the recovery of pathogenic V. parahaemolyticus. The densities of V. parahaemolyticus in shellfish from all harvest sites were positively correlated with water temperature. Shellfish from the Gulf Coast typically had higher densities of V. parahaemolyticus than did shellfish harvested from the North Atlantic or mid-Atlantic coast. Vibrio parahaemolyticus counts exceeded 1,000 CFU/g for only 5% of all samples. Pathogenic (tdh+) V. parahaemolyticus was detected in approximately 6% of all samples by both procedures, and 61.5% of populations in the positive samples from the direct plating procedure were at the lower limit of detection (10 CFU/g). The frequency of detection of pathogenic V. parahaemolyticus was significantly related to water temperature and to the density of total V. parahaemolyticus. The failure to detect pathogenic V. parahaemolyticus in shellfish more frequently was attributed to the low numbers and uneven distribution of the organism.

Animals↗
PubMedDate not supplied

Fish and shellfish poisoning.

OBJECTIVE: To review history, biology, and medical aspects associated with fish and shellfish poisoning. DATA SOURCES: Current literature, various Web sites, and Halstead's Volume II of Poisonous and Venomous Marine Animals. STUDY SELECTION: Determined by author. DATA SELECTION: Determined by author. DATA SYNTHESIS: Fish and shellfish poisoning occur through the natural event of the food chain. Fish and shellfish consume algae that contain toxin-producing dinoflagellates. As a result they become contaminated and the toxin is concentrated as it moves up the food chain. Fish and shellfish can tolerate high levels of toxins, thereby appearing healthy while posing a significant danger to man. The toxin cannot be detected by sight, smell, or taste and is not destroyed by cooking or freezing. Thus man becomes an unsuspecting victim. There are several types of poisoning that occur through fish and shellfish consumption. They are ciguatera and scombroid fish poisoning; and paralytic, diarrheic, neurotoxic, and amnesic shellfish poisoning. A different toxin produces each of these poisonings; however, sources and symptoms may be similar among these poisonings making them difficult to diagnose. These intoxications can vary in severity from mild to fatal depending on the type and amount of toxin ingested. Age and underlying illnesses may also contribute to the outcome of these poisonings. CONCLUSION: Though people are aware of health warnings and may think they are important, it is human nature to think that "this could not possibly happen to me". Therefore, they fail to make the necessary changes required to reduce the incidence of fish and shellfish poisoning.

Animals↗
PubMed2006

Problems associated with shellfish farming.

Shellfish culture is a major sector of aquaculture production worldwide, and zoonoses and drug residues associated with shellfish farm practice are of concern to public health. This paper focuses on three of the most important shellfish species: molluscs, crabs and shrimp. Although many diseases can affect shellfish, they do not appear to be transmittable to humans. Rather, the main hazards are associated with the methods used to farm the different species. The risk to human health from shellfish most commonly relates to contamination by biotoxins produced by marine algae. Another well-recognised problem associated with shellfish culture is the contamination of shellfish with domestic sewage that contains human pathogenic bacteria and viruses, which causes diseases such as typhoid fever and hepatitis. In shrimp farming, the main potential food safety hazards are zoonoses, chemical contamination and veterinary drug residues. Untreated effluent from shrimp farms is a major concern to the environmental sector as it is known to promote plankton blooms if directly discharged into natural water sources.

Animals↗
PubMed1984

Sterol composition of normal human bile. Effects of feeding shellfish (marine) sterols.

To examine the sterol composition of normal human bile and the effects of dietary components from certain shellfish upon bile composition, we fed 7 subjects diets rich in shellfish for 2 wk following a typical American diet. The total cholesterol, bile acid, and phospholipid, and the individual sterols and bile acids of the bile samples during each dietary period were measured. In the bile of 7 subjects consuming the typical American diet, nine different neutral sterols, in addition to cholesterol, were identified. Similar patterns of these sterols have been found in human gallstones and in plasma after shellfish feeding. The five shellfish sterols (22-dehydrocholesterol, 24-methylene cholesterol, brassicasterol, isofucosterol, and a C-26 sterol) increased from 0.3% to a total of 5.2% (p less than 0.001) of total sterols. A comparison of the ratios of various shellfish sterols to cholesterol in plasma and in bile suggested selectively greater excretion of shellfish sterols relative to cholesterol. Our data demonstrated that human bile contains a mixture of sterols and that its sterol composition can be readily altered by dietary changes. The lithogenicity of the bile based on the ratio of cholesterol, bile acids, and phospholipids, and the bile acid composition was not affected by the presence of shellfish sterols. However, since some of these sterols occur in human gallstones, their lithogenic capacity cannot be ruled out.

Adult↗
PubMed1993

Methods for the concentration and detection of human enteric viruses in shellfish: a review.

Shellfish, including oysters, mussels, and clams, are filter feeding bivalve mollusks and can accumulate human pathogens at levels higher than those in their surrounding waters. Outbreaks of shellfish-borne enteric viral diseases have been reported worldwide. To determine the public health safety of shellfish, methods are available for the direct detection of human enteric viruses in shellfish tissues. Potential problems with these methods include (i) toxicity of the final sample to cell cultures used for viral assay, and (ii) a large sample volume that cannot be conveniently assayed. To overcome these problems, several methods for the concentration and detection of enteric viruses in shellfish tissues have been developed and utilized. A review of these methods indicates that none of them is universally accepted because no single method is equally effective for shellfish obtained from different geographical locations and under all conditions. It is suggested, therefore, that a proposed method should first be tested under experimental conditions, utilizing virus-spiked shellfish, before using it under field conditions.

Animals↗
PubMed1996

Raw shellfish consumption and warning labels: results from the 1993 Texas Behavioral Risk Factor Surveillance System (BRFSS) survey.

We used the 1993 Texas Behavioral Risk Factor Surveillance System survey to assess the prevalence of raw shellfish consumption and to find the demographic and behavioral characteristics of raw shellfish consumers. We studied the general impact of warning labels reported by survey respondents. Data were analyzed using univariate and multiple logistic regression methods. Fourteen percent of the Texas surveyed reported consuming raw shellfish. Respondents with incomes greater than or equal to $25,000 and with education beyond high school were more likely to report consuming raw shellfish than were those with incomes less than $25,000 and with high school diplomas or less. Respondents at risk for acute and chronic drinking, driving while intoxicated, and driving without a seat belt were more likely than those not at risk of these behaviors to report consumption of raw shellfish. We did not find a significant difference between eaters and noneaters of raw shellfish regarding the impact of warning labels: however, among eaters of raw shellfish, older respondents were more likely than younger respondents to report that warning labels had no effect on them.

Adolescent↗
PubMedDate not supplied

[Microbiological monitoring of mussels and clams collected from the shellfish-growing marine areas in Rimini Province].

A 5 years survey (1996-2000) was performed on the microbiological quality of shellfish (mussels and clams) collected from authorized shellfish-growing area of the North Adriatic Sea (province of Rimini). 7.0% of mussel samples (33/474) and 21.9% of clam samples (218/996) exceeded the legal limits for faecal indicators (Dlgs 530/92). The faecal contamination of shellfish was related to the organic pollution arriving from inland surface waters. In fact shellfish harvested near the coast were more contaminated, as well as shellfish grown in the surface layers of the open sea, where the fresh waters of the streams tend to stratify. Faecal contamination was also directly correlated with rainfall, probably because the atmospheric precipitation, increasing the flow of the streams, favoured the transport of organic substances and micro-organisms deriving from the soil washing and the municipal sewage effluents. Furthermore, when rainfall was particularly plentiful, sewage inflow could also exceed the hydraulic capacity of the treatment plants; thus making necessary to discharge untreated waste directly into surface waters. Salmonellae were found in 0.7% of clam samples. Although this percentage is very low, it shows that pathogenic micro-organisms are present in this area of sea. This finding, together with the high variability of shellfish pollution due to occasional factors as rainfall, emphasise the importance of the systematic monitoring of the microbiological quality of shellfish.

Animals↗
PubMed2007

Feasibility of gamma irradiation as a stabilisation technique in the preparation of tissue reference materials for a range of shellfish toxins.

The effect of gamma-irradiation on concentrations of hydrophilic and lipophilic phycotoxins has been investigated by use of HPLC-UV and LC-MS. Pure toxins in organic solvents and toxins in mussel (Mytilus edulis) tissues were irradiated at three different doses. In solution all toxin concentrations were reduced to some extent. Most severe decreases were observed for domoic acid and yessotoxin, for which the smallest dose of irradiation led to almost complete destruction. For pectenotoxin-2 the decrease in concentration was less severe but still continuous with increasing dose. Azaspiracid-1 and okadaic acid were the least affected in solution. In shellfish tissue the decrease in toxin concentrations was much reduced compared with the effect in solution. After irradiation at the highest dose reductions in concentrations were between ca. 5 and 20% for the lipophilic toxins and there was no statistical difference between control and irradiated samples for azaspiracids in tissue. Irradiation of shellfish tissues contaminated with domoic acid led to a more continuous decrease in the amount of the toxin with increasing dose. The effect of irradiation on the viability of microbial activity in shellfish tissues was assessed by using total viable counting techniques. Microbial activity depended on the type of shellfish and on the pretreatment of the shellfish tissues (with or without heat treatment). As far as we are aware this is the first investigation of the effectiveness of irradiation as a technique for stabilising tissue reference materials for determination of phycotoxins. Our results suggest that this technique is not effective for materials containing domoic acid. It does, however, merit further investigation as a stabilisation procedure for preparation of shellfish tissue materials for some lipophilic toxins, in particular azaspiracids. Chemical structures of the toxins investigated in the study.

Animals↗
PubMed1989

Paralytic shellfish poisoning in northwest Spain: the toxicity of the dinoflagellate Gymnodinium catenatum.

The highly productive mussel fishery in the Rias Bajas region of northwest Spain has experienced several outbreaks of paralytic shellfish poisoning (PSP) beginning in 1976. In this study, similarities in the HPLC analyses of extracts from toxic shellfish, plankton tows and cultured dinoflagellates from the Rias Vigo and Pontevedra clearly indicate that Gymnodinium catenatum Graham is the organism responsible for recent PSP episodes. The toxin profile of the dinoflagellate contains an unusually high proportion of the low potency sulfocarbamoyl toxins (ca. 90-95 mole %), although a major portion of the overall toxicity is due to the more potent saxitoxin that is present at 5-10% of the total. Toxin profiles of shellfish showed approximately the same composition as that of the dinoflagellate, although the shellfish contained several carbamate toxins (GTX I, GTX II, GTX IV and NEO) that were not detected in G. catenatum culture extracts. The shellfish also contained decarbamoyl toxins (dc-GTX II and dc-GTX-III) at approximately 2% of the total profile. Since these were not detected in the dinoflagellate, their presence reflects either chemical or enzymatic conversion within the shellfish.

Animals↗
PubMed2002

A rapid and sensitive assay for paralytic shellfish poison (PSP) toxins using mouse brain synaptoneurosomes.

A membrane potential assay using mouse brain synaptoneurosomes was evaluated for the determination of paralytic shellfish poison (PSP) toxin content of mussels and other bivalve species important to the shellfish industry. The assay relies on the ability of PSP toxins to block veratridine-induced depolarization of synaptoneurosomes. Changes in the membrane potential of synaptoneurosomes were monitored using the voltage-sensitive fluorescent probe rhodamine 6G. Standard saxitoxin was found to be a potent inhibitor of the membrane depolarizing effects of the sodium channel activator veratridine (I(50) ca. 4 nM). Likewise, shellfish extracts containing PSP toxins inhibited veratridine-induced depolarization. Neither saxitoxin or shellfish extracts had any discernible effect on the resting membrane potential of synaptoneurosomes. When synaptoneurosomal results for extracts of mussels (n=120) and other shellfish (n=29) were correlated with official mouse toxicity assay data there was very good agreement (r(2)=0.84 and 0.86, respectively), indicating that the in vitro assay has utility for a variety of commercially relevant shellfish species. Our investigation suggests that the mouse synaptoneurosome assay is of similar sensitivity to the official CD1 mouse toxicity assay. The synaptoneurosome fraction can be prepared quickly (approx. 40 min) and an individual assay takes less than 7 min. Since 20 such assays can be performed using material from a single CD1 mouse brain, there is considerable opportunity for reducing the number of animals required in conventional PSP monitoring while retaining the same animal system.

Animals↗
PubMed2000

Simplified procedure for detection of enteric pathogenic viruses in shellfish by RT-PCR.

Epidemiological evidence linking the transmission of enteric viral disease to shellfish has been known for a long time. A variety of methods have been described for the detection of viral contaminants in shellfish using RT-PCR. However, these methods generally include numerous, often fastidious and time consuming steps for virus release from shellfish tissues and viral RNA isolation. A simplified procedure based on the enzymatic liquefaction of shellfish digestive tissues without any mechanical homogenisation step, followed by a simple clarification of the lysate using dichloromethane extraction, was developed. Viral RNA is isolated directly from the shellfish extract by a guanidium thiocyanate-silica extraction method, adapted for the use of a vacuum manifold system. Virus-specific RT-PCR assays were set up for detection of genomic sequences of the predominant viral pathogens, HAV, Astrovirus and Norwalk-like viruses (from genogoups I or II). The specificity of the amplicons is confirmed finally by hybridisation with DIG-labelled specific probes. The overall procedure applied to shellfish samples spiked with HAV particles allowed a detection of 20 pfu of HAV per g of hepatopancreas. In addition, up to 20 samples can be tested within 24 h.

Animals↗
PubMed2002

Depuration dynamics of viruses in shellfish.

The consumption of shellfish has been associated with viral infections even in cases where shellfish complied with the current regulation, which is based on bacterial analysis. In this study, depuration rates of potential indicators and human viruses have been analysed in order to study the use of complementary parameters for evaluating the microbiological quality of depurated shellfish. Depuration of naturally highly polluted mussels has been evaluated and analyses for Escherichia coli, Clostridium perfringens, somatic coliphages, F-RNA phages and bacteriophages infecting Bacteroides fragilis RYC2056 and HSP40, human adenovirus, enterovirus have been done. Seawater of the depuration tank was disinfected by UV irradiation, ozone and passed through a skimmer and a biological filter. The correct functioning of the depuration tank was monitored by the quantification of total organic carbon (TOC), NH4+ and total aerobic bacteria in the seawater. To study the relation between the bacteriophages and the human viruses analysed, a logistic regression model was applied. F-RNA phages are significantly related to human adenoviruses and enteroviruses. Thus, they can be used as a complementary parameter for evaluating the efficiency of the depuration treatment. Somatic coliphages are also significantly associated with enteroviruses. Bacteriophages infecting B. fragilis HSP40 were analysed by the double-agar-layer (DAL) method, which quantifies infectious viruses, and by nested PCR, which detects the presence of the genome of these phages. The highest sensitivity of the molecular techniques was demonstrated and the results obtained are an indicator of a close relation between positive results by PCR and the presence of infectious viral particles in shellfish. All shellfish samples were negative for human viruses by PCR after 5 days of depuration treatment and the results obtained applying a regression model also showed negative results or nearly for F-RNA phages and bacteriophages infecting B. fragilis RYC2056. Thus, in this specific depuration treatment, 5 days may be necessary to assess the sanitary quality of shellfish.

Adenoviridae↗
PubMed2000

Toxigenic saprophytic fungi in marine shellfish farming areas.

Toxigenic saprophytic fungi were isolated from samples of shellfish, sediment and seawater obtained from marine shellfish farming areas. The 456 strains identified included 12 different genera, with a clear predominance (68%) of Penicillium, Aspergillus, Trichoderma and Cladosporium. To assess the risk of poisoning due to the presence of these fungi in shellfish farming areas, the strains were cultured in liquid medium, filtered, and tested on larvae of Artemia salina, a small crustacean highly sensitive to mycotoxins. Thirty-five point five percent of the strains proved active with this test. This study confirms the existence of fungi in shellfish farming areas, as suggested by our earlier work showing that filter-feeding shellfish accumulate toxic metabolites of fungal origin. The presence of fungi in the marine environment represents a real risk of poisoning through the consumption of contaminated shellfish.

Animals↗