Soft shell crab is a seafood delicacy in many parts of the world. In Denmark, it has been investigated whether a commercial production of soft shell European green crabs (Carcinus maenas) would be feasible. In relation to this, a feeding study was performed to examine if occurrence of DSP toxins in the product could be a food safety problem. The crabs were fed with mussels containing DSP toxins (2500 microg total okadaic acid equivalents/kg) for 17 days and then fasted for 19 days. The content of total okadaic acid equivalents in the digestive organs was on average 27 times higher than the corresponding content in the body meat. The highest level of total okadaic acid equivalents measured was 12 microg/kg in body meat and 503 microg/kg in digestive organs. The results show that the content of DSP toxins in a commercial product of soft shell European green crab (without digestive organs) could be regarded as negligible.
Okadaic acid (OA) is a lipophilic phycotoxin, which accumulates in the digestive organs of mussels and may cause diarrhetic shellfish poisoning (DSP) in humans. Depuration of toxic mussels is a potential option for the shellfish industry to increase the availability of marketable mussels. To develop cost-effective depuration methods for DSP toxins, knowledge about the environmental conditions and physiological processes regulating the rate of depuration is essential. In this paper, the importance of lipid breakdown for elimination of OA in mussels was investigated by performing a field study and a manipulative laboratory experiment. First, total lipid content and concurrent concentration of OA in the digestive glands of farmed blue mussels, Mytilus edulis, was analysed on a monthly basis from January to June 2000. A significant positive correlation between levels of OA and lipid content was observed between January and March, when lipid levels were showing a decreasing trend. This supported a previously proposed model that breakdown of lipid stores may affect the release and elimination of this lipophilic toxin. To test this causal model, a laboratory experiment was performed. Mussels containing OA were exposed to experimental treatments (increased seawater temperature and/or food limitation) for 24 days in order to increase the energy requirements and need to use lipids as an energy source. It was predicted that mussels exposed to these treatments would have a faster elimination rate of OA compared to feeding mussels kept in ambient seawater temperature. The results showed that lipid content was significantly reduced in mussels exposed to an increased water temperature (24 degrees C) compared to ambient temperature (18 degrees C). The amount of lipids was not affected by food limitation. Although lipid content was reduced in 24 degrees C, the rate of depuration of OA was not faster for mussels in this treatment and no correlation was detected between lipid content and OA. Depuration rates were very similar for all treatments and followed an exponential decrease relationship (t(1/2) = 8 days). Thus, the proposed model that lipid breakdown affects the mechanism of elimination of OA was not supported. Nevertheless, the observed rates of depuration provide useful information and a potential predictive tool for large-scale depuration methods of mussels. The difficulties to influence the rate of depuration of this toxin by changing the environmental conditions suggest that processes, insensitive to short-term manipulation of the external environment, regulate depuration of OA.
Norovirus causes large outbreaks involving all age groups and are considered the most common cause of infectious foodborne diseases worldwide. The aim of this study was to describe a norovirus outbreak connected to insufficient heat treatment during preparation of a shellfish soup in serving portions, during a company Christmas celebration in Norway, December 2013. A questionnaire sent to the employees, showed that 67 % (n = 43) of the celebration participants, reported gastrointestinal symptoms including stomach pain, vomiting, diarrhoea and light fever in the period between 24 and 48 h post celebration. Several dishes were served, including shellfish soup made with carpet shell clams (Tapes rhomboides) in porcelain cups. Consuming this soup, was the only significant risk factor for infection. Norovirus GI and GII were detected in the remaining raw shellfish. To mimic the time and temperature obtained during bivalve soup preparation, raw chopped shellfish tissue and raw cepa onion were added in porcelain cups tempered to 20 °C. To each of these cups, boiling soup base was added. The temperature in the shellfish tissue was continuously recorded, and showed a maximum of 49 °C in the period between 3 and 7 min after adding the boiling soup base. After 1 h the temperature was 30 °C. This time and temperature combination was obviously not sufficient for inactivation of norovirus present in the shellfish tissue. In conclusion, the heat-absorbing capacity of cold ingredients, utensils and table wear porcelain should not be underestimated during food production. Consumers who want to avoid eating raw shellfish, should not assume that the shellfish tissue in preparation as described in our study is adequately heat treated.
In Canada in late 1987 there was an outbreak of an acute illness characterized by gastrointestinal symptoms and unusual neurologic abnormalities among persons who had eaten cultivated mussels. Health departments in Canada solicited reports of this newly recognized illness. A case was defined as the occurrence of gastrointestinal symptoms within 24 hours or of neurologic symptoms within 48 hours of the ingestion of mussels. From the more than 250 reports received, 107 patients met the case definition. The most common symptoms were vomiting (in 76 percent of the patients), abdominal cramps (50 percent), diarrhea (42 percent), headache, often described as incapacitating (43 percent), and loss of short-term memory (25 percent). Nineteen patients were hospitalized, of whom 12 required intensive care because of seizures, coma, profuse respiratory secretions, or unstable blood pressure. Male sex and increasing age were associated independently with the risks of hospitalization and memory loss. Three patients died. Mussels associated with this illness were traced to cultivation beds in three river estuaries on the eastern coast of Prince Edward Island. Domoic acid, which can act as an excitatory neurotransmitter, was identified in mussels left uneaten by the patients and in mussels sampled from these estuaries. The source of the domoic acid appears to have been a form of marine vegetation, Nitzschia pungens, also identified in these waters in late 1987. The contaminated mussels from Prince Edward Island were removed from the market, and no new cases have occurred since December 1987. We conclude that the cause of this outbreak of a novel and severe intoxication was the ingestion of mussels contaminated by domoic acid, a potent excitatory neurotransmitter.
Comment In: N Engl J Med. 1990 Dec 6;323(23):1631-32073268
Sources of faecal pollution in coastal recreational waters may be identified by analysing different host associated microorganisms or molecular markers. However, the microbial targets are often present at low numbers in moderately impacted waters, and often exhibit significant temporal and spatial variability in waters with fluctuating faecal loads. This patchy occurrence can limit successful detection of relevant targets in microbial source tracking studies. In this study, we explored the possibility for using the blue mussel (Mytilus edulis) as a biosampler for accumulation of faecal bacteria relevant for microbial source tracking. Non-contaminated blue mussels were transferred to three coastal recreational waters affected by faecal pollution of unknown origin. Molecular markers associated with animal and human waste were targeted by PCR and compared in seawater and mussel samples. The results demonstrated that transplanted mussels in simple enclosures accumulated and retained elevated levels of molecular markers associated with different types of faecal pollution. The targets included a novel putative human associated E. coli subgroup B2 VIII clone, and animal and human associated markers in enterococci (esp, M19, M66, M90, and M91). Human (sewage) associated markers including esp and M66 were sometimes not detectable in seawater samples despite known wastewater contamination, whereas the markers were detectable in mussels. We suggest that transplanted mussels should be considered as potential biosamplers in studies focusing on identifying source of faecal pollution in low or moderately impacted recreational waters. Bioaccumulation of molecular markers in mussels for several days may represent the water quality better than traditional grab samples from the water column.
Anthropogenic CO2 emissions are rapidly changing seawater temperature, pH and carbonate chemistry. This study compares the embryonic development under high pCO2 conditions across the south-north distribution range of the marine clam Limecola balthica in NW Europe. The combined effects of elevated temperature and reduced pH on hatching success and size varied strongly between the three studied populations, with the Gulf of Finland population appearing most endangered under the conditions predicted to occur by 2100. These results demonstrate that the assessment of marine faunal population persistence to future climatic conditions needs to consider the interactive effects of co-occurring physico-chemical alterations in seawater within the local context that determines population fitness, adaptation potential and the system resilience to environmental change.
Aquatic Ecology and Water Quality Management Group, Department of Environmental Sciences, Wageningen University, P.O. Box 47, 6700 AA Wageningen, the Netherlands; Department of Animal Ecology, Wageningen Environmental Research, P.O. Box 47, 6700 AA Wageningen, the Netherlands. Electronic address: firstname.lastname@example.org.
Monitoring parameters for the assessment of oil and gas related contaminants and their biological effects need validation before application in the Arctic. For such monitoring purposes, we evaluated the potential use of three biomarkers (acetylcholinesterase, acyl-CoA oxidase and glutathione S-transferase) for application to an Arctic bivalve (Astarte borealis) and determined the body residue of pyrene and two pyrene metabolites (1-hydroxypyrene and pyrene-1-glucuronide) in Arctic benthic species (bivalve: Macoma calcarea; polychaete: Nephtys ciliata) and temperate benthic species (bivalve: Limecola balthica; polychaete: Alitta virens) in order to establish the potential of polycyclic aromatic hydrocarbons (PAHs) metabolite profiles as biomarkers of exposure in such species. Experimental PAH exposure levels were probably too low (0.2-1.7?mg/kg dry weight in sediment) to induce or inhibit biomarker responses in A. borealis. Concentrations of pyrene and pyrene metabolites varied between species, although no consistent patterns could be established among taxonomic groups and locations. Metabolites made up to 79% of the total pyrene concentrations, indicating that basal metabolic activity is affecting pyrene kinetics even at low concentrations in all species. This indicates that Arctic and temperate species could show similar metabolism patterns of PAHs, although more insight into the effects of confounding factors is needed.
The effects of cyanobacteria (Aphanizomenon flos-aquae (90%), Microcystis aeruginosa) and dense Elodea canadensis beds on the health endpoints of the amphipod Gmelinoides fasciatus and bivalve mollusc Unio pictorum were examined in mesocosms with simulated summer conditions (July-August 2018) in the environment of the Rybinsk Reservoir (Volga River Basin, Russia). Four treatments were conducted, including one control and three treatments with influencing factors, cyanobacteria and dense elodea beds (separately and combined). After 20 days of exposure, we evaluated the frequency of malformed and dead embryos in amphipods, heart rate (HR) and its recovery (HRR) after stress tests in molluscs as well as heat tolerance (critical thermal maximum or CTMax) in both amphipods and molluscs. The significant effect, such as elevated number of malformed embryos, was recorded after exposure with cyanobacteria (separately and combined with elodea) and presence of microcystins (MC) in water (0.17 µg/l, 40% of the most toxic MC-LR contribution). This study provided evidence that an elevated number (>5% of the total number per female) of malformed embryos in amphipods showed noticeable toxicity effects in the presence of cyanobacteria. The decreased oxygen under the influence of dense elodea beds led to a decrease in HR (and an increase in HRR) in molluscs. The notable effects on all studied biomarkers, embryo malformation frequency and heat tolerance in the amphipod G. fasciatus, as well as the heat tolerance and heart rate in the mollusc U. pictorum, were found when both factors (elodea and cyanobacteria) were combined. The applied endpoints could be further developed for environmental monitoring, but the obtained results support the importance of the combined use of several biomarkers and species, especially in the case of multi-factor environmental stress.