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.
The Royal Swedish Academy of Sciences, Kristineberg 566, SE-451 78 Fiskebäckskil, Sweden; Dept. of Natural Science, Kristianstad University, SE-291 88 Kristianstad, Sweden. Electronic address: firstname.lastname@example.org.
The potential for climate-related spread of infectious diseases through marine systems has been highlighted in several reports. With this review we want to draw attention to less recognized mechanisms behind vector-borne transmission pathways to humans. We have focused on how the immune systems of edible marine shellfish, the blue mussels and Norway lobsters, are affected by climate related environmental stressors. Future ocean acidification (OA) and warming due to climate change constitute a gradually increasing persistent stress with negative trade-off for many organisms. In addition, the stress of recurrent hypoxia, inducing high levels of bioavailable manganese (Mn) is likely to increase in line with climate change. We summarized that OA, hypoxia and elevated levels of Mn did have an overall negative effect on immunity, in some cases also with synergistic effects. On the other hand, moderate increase in temperature seems to have a stimulating effect on antimicrobial activity and may in a future warming scenario counteract the negative effects. However, rising sea surface temperature and climate events causing high land run-off promote the abundance of naturally occurring pathogenic Vibrio and will in addition, bring enteric pathogens which are circulating in society into coastal waters. Moreover, the observed impairments of the immune defense enhance the persistence and occurrence of pathogens in shellfish. This may increase the risk for direct transmission of pathogens to consumers. It is thus essential that in the wake of climate change, sanitary control of coastal waters and seafood must recognize and adapt to the expected alteration of host-pathogen interactions.
The levels of aluminium have been determined in a number of individual foodstuffs on the Swedish market and in 24 h duplicate diets collected by women living in the Stockholm area. The results show that the levels in most foods are very low and that the level in vegetables can vary by a factor 10. Beverages from aluminium cans were found to have aluminium levels not markedly different from those in glass bottles. Based on the results of the analysis of individual foods, the average Swedish daily diet was calculated to contain about 0.6 mg aluminium, whereas the mean content of the collected duplicate diets was 13 mg. A cake made from a mix containing aluminium phosphate in the baking soda was identified as the most important contributor of aluminium to the duplicate diets. Tea and aluminium utensils were estimated to increase the aluminium content of the diets by approximately 4 and 2 mg/day, respectively. The results also indicate that a considerable amount of aluminium must be introduced from other sources.
The performance characteristics of AOAC Official Method 2011.02 (the PCOX method) as a replacement for the AOAC mouse bioassay procedure have been well defined by validation studies, but these data do not communicate the complete story. The context provided by analyzing 9000 regulatory monitoring samples over 3 years demonstrates not only the reduction in animal use but also the increase in food safety that has been realized using a chemistry-based method. Detection of lower toxin levels provided early warning to enable directed sampling as toxin levels increased. The toxin profile information generated by a chemistry-based method was used to detect potential interferences qualitatively and can be used to assess the impact of changes recommended to monitoring programs. Such changes might include which toxins should be included in an action limit or the toxic equivalence factors used for these toxins.
In Antwerp, Belgium, 403 cases of diarrhoeic shellfish poisoning were reported after consumption of blue mussels. Symptoms included diarrhoea, vomiting, abdominal pain, and nausea. The analysis of faecal specimens from patients allowed diagnosis exclusions for bacteria and viruses. Mouse-assays revealed the presence of biotoxins specific of dinoflagellates, which were identified and quantified by LC-MS. The mussels were imported from Denmark, and were part of a batch presenting high concentrations of okadaic acid above the regulatory limits.
In January 2004, an increase in gastrointestinal illness following oyster consumption was reported in British Columbia. An investigation was initiated to explore the association between norovirus infection and consumption of British Columbia oysters and to identify the source of oyster contamination.
The outbreak investigation included active surveillance for human cases, two cohort studies, trace-back of oysters, and laboratory testing of oysters and human stools.
Enhanced surveillance identified 26 confirmed and 53 clinical cases over 3 months. Oyster consumption was associated with illness in one cohort and suggestive in the other. Oysters were traced to 14 geographically dispersed harvest sites, 18 suppliers, and 45 points of purchase. Norovirus BCCDC03-028 (genotype I.2) was detected in 50% of human specimens. Experimental methods detected norovirus in 12 oyster samples. Sequencing identified mixed clonal patterns in the oysters with one direct sequence match between an oyster sample and the associated human specimen.
The consumption of raw oysters led to norovirus infection. The source of oyster contamination remained unidentified. The geographical dispersion of implicated harvest sites was unusual.
This outbreak is unlike most shellfish outbreaks that can be traced back to a common source and challenges conventional thinking that all oyster-related norovirus outbreaks of are a result of point source contamination.
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.