13 sick pulling mussels from the shell

Posted on August 31, 2019 by Douglas Powell

I love my shellfish – mussels and scallops (oysters are sorta gross) – but the kid was diagnosed with a shellfish allergy so they’re an occasional lunch while she’s at school.

Health types in the UK report on six cases of diarrhetic shellfish poisoning (DSP) following consumption of mussels in the United Kingdom (UK). The mussels contained high levels of heat-stable okadaic acid (OA)-group toxins. Here we describe the environmental and epidemiological investigation carried out in response to the outbreak.

In June 2019 (day 0), Public Health England South West was notified by the local authority of three diners who were unwell following consumption of mussels in a restaurant 5 days earlier. The local authority had determined that the restaurant had had received a batch recall notice, also 5 days earlier, from the shellfish producer for the mussels because of elevated toxin levels but this was not seen before the mussels were served that day. On day 1, PHE South West received a report from the county neighbouring the first of gastrointestinal illness linked to mussels from the same producer. A multi-agency outbreak control team was therefore convened on day 2 and led by the PHE South West health protection team.

An alert was sent to all health protection teams across England on day 2 asking about any reported cases of gastrointestinal illness following consumption of mussels. Local authorities in areas of product distribution were informed of the identified risk by email. Persons reporting illness who were identified by local authorities as having consumed the affected mussels were asked by PHE to complete a bespoke questionnaire on exposure and clinical data.

A probable case of DSP was defined as an individual with diarrhoea, three or more loose stools in 24 h, or vomiting or abdominal cramps or nausea, with date of onset from 7 days before to 1 day after notification of the outbreak, and time of onset 30 min to 24 h following consumption of mussels harvested from the affected site. Confirmed cases were as probable, but with an absence of pathogens in a stool sample that would otherwise explain illness.

Thirteen individuals reported to have been unwell after consumption of mussels were contacted. Completed questionnaires were received from seven individuals, of which three were confirmed, and three probable cases. The cases ate at four separate venues. One respondent did not meet the case definition as symptom onset was more than 24 h following consumption.

The mean age of cases was 59 years (range: 37–76 years); three were male and three were female. All cases reported eating steamed mussels. Five cases ate mussels as a main course and one as a starter. Reported portion sizes ranged from 11 to 50 mussels.

The mussels were produced in an offshore marine area. A routine shellfish monitoring programme is in place throughout England and Wales, including at the affected site. As a part of this programme, the water column is sampled every 2 weeks from April to September and cell counts of potentially harmful algal species are measured. Shellfish flesh samples are also tested for the presence of selected European Union (EU)-regulated biotoxins every 4 weeks during April to September each year unless phytoplankton counts and/or shellfish toxins are quantified above specified warning limits that require further precautions, including re-testing and closure.

Lipophilic toxin determination, including that for OA-group toxins, is routinely carried out using the method specified in in the EU-Harmonised Standard Operating Procedure for determination of lipophilic marine biotoxins in molluscs by LC-MS/MS [1]. Additional flesh and water samples were taken in advance of the planned sampling date following a report to the local authority from a local fisherman of a red-coloured algal bloom six miles offshore from the production site.

The local authority determined the source of the mussels by questioning venues linked to reports of illness. Subsequently, the shellfish producer provided the outbreak control team with a complete list of all businesses who had received the affected mussels. Mussels from the site were harvested daily from 9 to 5 days before notification of the outbreak for commercial sale. The mussels were not tested by the producer for the presence of toxins. A large volume of mussels was distributed to seafood wholesalers, restaurants and pubs, and subject to the recall notice distributed by the producer 5 days before reports of illness to PHE. A limited number of businesses not linked to any known cases, including wholesalers, retailers, restaurants and pubs, responded to the recall stating they had sold some of the affected produce. No produce was found to still be in circulation at the time of the outbreak response.

Water column and shellfish flesh sampling results are summarised in Table 2. Measured densities of Dinophysis spp. in the water column increased rapidly from being undetectable 16 days before outbreak notification to 1,600 cells per litre 7 days before, coinciding with the time of harvesting of the affected batch and exceeding the England, Wales and Northern Ireland Food Standards Agency trigger level of 100 cells per litre. The level of total OA-group lipophilic toxins in mussel flesh was 338 µg OA equivalents (eq) per kg, following application of measurement uncertainty, 7 days before outbreak notification. This exceeded the maximum permitted limit (MPL) of 160 µg OA eq per kg defined by European Commission (EC) regulation 853/2004 [2]. Toxin concentrations quantified showed that an average of 94% of the OA-group toxins present in the mussels consisted of OA itself, with the remainder being dinophysistoxin 2 (DTX2).

Water column sampling 7 days before outbreak notification did not detect other harmful algal species apart from Pseudo-nitzschia spp., the causative diatom for domoic acid responsible for amnesic shellfish poisoning, at 1,320 cells per litre. This is below the trigger level of 150,000 cells per litre for this species.

Routine shellfish sampling at the same site during the same time period did not detect paralytic shellfish poisoning toxins. Trace levels of yessotoxins were detected, but along with traces of azaspiracids, they were well below regulatory levels. Amnesic shellfish poisoning toxins were below the limit of quantitation (LOQ).

In response to the elevated toxin levels quantified and reported 5 days before outbreak notification, the shellfish bed was immediately closed for harvesting as per standard practice in England. The Food Standards Agency urgently contacted local authorities of places where the affected product had been distributed to ensure that wholesalers and venues had acted upon the recall. Venues were asked whether any product had been frozen, for example in the form of stock, as this would not deactivate the toxin, but there was no evidence this had been done.

Discussion

We report on six cases of DSP associated with consumption of mussels harvested in the South West of England. Without an available validated test for relevant toxins in human samples, the diagnosis was made based on characteristic clinical symptoms, including diarrhoea, abdominal pain, nausea and fever/chills, elevated levels of OA-group toxins in the flesh of mussels from the same batch as those consumed, the absence of faecal pathogens in stool of cases and epidemiological evidence of exposure to the produce.

DSP occurs following consumption of seafood containing high levels of the heat-stable OA-group toxins produced by dinoflagellates including Dinophysis spp., and is characterised by a rapid-onset of self-limiting gastrointestinal illness [3,4]. Recognised outbreaks of DSP are rare. Seventy cases were identified in 2013 following consumption of mussels harvested around the Shetland Islands [5] and 49 cases were identified in 1998 following consumption of UK-harvested mussels in London [6]. Outbreaks have been recorded in recent years in China, the United States, France and Canada [4,7–9].

The lowest-observed-adverse-effect level of OA is 45 to 50 µg OA eq per person [4,10]. In our study, an average main course portion of mussels (500 g in shell) would provide 41 µg OA eq., using a flesh weight yield of 24% [11]. This level of exposure is consistent with DSP as the cause of illness considering variability in portion sizes, flesh yield, body weight and toxin levels at the production site. Individual mussel sizes served were unavailable but would likely vary. Therefore, overall estimated portion weight was used to calculate the exposure dose. A limitation is that body weight (bw) was not recorded for cases and because of this, OA eq per kg bw could not be calculated.

A shellfish biotoxin programme monitoring the occurrence of harmful algal blooms and toxins in classified shellfish production areas in the UK, alongside food business operator checks, remains a robust system to protect population health. Nonetheless, a rapid increase in concentrations of Dinophysis spp. cells within the waters of the production site may have contributed to the outbreak, in tandem with shellfish harvesting occurring before official control results were reported and site closure. Whyte et al. (2014) demonstrated that a similar rapid increase in Dinophysis levels, resulting from a change in prevailing wind direction, occurred in the 2013 Shetland Islands origin outbreak [5]. Transdisciplinary research is required to predict future risk and inform monitoring, particularly given likely changes in the distribution of potentially-toxic species particularly if temperature of ocean water increases [12]. Our investigation suggested that affected produce may have been sold by restaurants and pubs with no known linked cases. Given that DSP is a self-limiting illness that may be under-reported by cases and has low awareness among clinicians, the actual number of persons affected in this outbreak is likely to be higher [13].

This outbreak highlights that clinicians and public health professionals should be aware of algal-derived toxins as a potential cause of illness following seafood consumption, and that the need for effective end-product testing of shellfish to ensure food safety remains.

Outbreak of diarrhetic shellfish poisoning associated with consumption of mussels, United Kingdom, May to June 2019

28.aug.19

EuroSurveillance

Nick Young, Charlotte Robin, Et al

https://eurosurveillance.org/content/10.2807/1560-7917.ES.2019.24.35.1900513

Vibrio risk model development using various water inputs

Posted on August 30, 2019 by Douglas Powell

Vibrio parahaemolyticus is a leading cause of seafood-borne gastroenteritis. Given its natural presence in brackish waters, there is a need to develop operational forecast models that can sufficiently predict the bacterium’s spatial and temporal variation.

This work attempted to develop V. parahaemolyticus prediction models using frequently measured time-indexed and -lagged water quality measures. Models were built using a large data set (n = 1,043) of surface water samples from 2007 to 2010 previously analyzed for V. parahaemolyticus in the Chesapeake Bay. Water quality variables were classified as time indexed, 1-month lag, and 2-month lag. Tobit regression models were used to account for V. parahaemolyticus measures below the limit of quantification and to simultaneously estimate the presence and abundance of the bacterium. Models were evaluated using cross-validation and metrics that quantify prediction bias and uncertainty.

Presence classification models containing only one type of water quality parameter (e.g., temperature) performed poorly, while models with additional water quality parameters (i.e., salinity, clarity, and dissolved oxygen) performed well. Lagged variable models performed similarly to time-indexed models, and lagged variables occasionally contained a predictive power that was independent of or superior to that of time-indexed variables. Abundance estimation models were less effective, primarily due to a restricted number of samples with abundances above the limit of quantification. These findings indicate that an operational in situ prediction model is attainable but will require a variety of water quality measurements and that lagged measurements will be particularly useful for forecasting.

Future work will expand variable selection for prediction models and extend the spatial-temporal extent of predictions by using geostatistical interpolation techniques.

IMPORTANCE Vibrio parahaemolyticus is one of the leading causes of seafood-borne illness in the United States and across the globe. Exposure often occurs from the consumption of raw shellfish. Despite public health concerns, there have been only sporadic efforts to develop environmental prediction and forecast models for the bacterium preharvest.

This analysis used commonly sampled water quality measurements of temperature, salinity, dissolved oxygen, and clarity to develop models for V. parahaemolyticus in surface water. Predictors also included measurements taken months before water was tested for the bacterium. Results revealed that the use of multiple water quality measurements is necessary for satisfactory prediction performance, challenging current efforts to manage the risk of infection based upon water temperature alone.

The results also highlight the potential advantage of including historical water quality measurements. This analysis shows promise and lays the groundwork for future operational prediction and forecast models.

Vibrio parahaemolyticus in the Chesapeake Bay: Operational in situ predition and forecast models can benefit from inclusion of lagged water quality measurements

Public and Environmental Health Microbiology

Benjamin J. K. Davis, John M. Jacobs, Benjamin Zaitchik, Angelo DePaola, Frank C. Curriero

DOI: 10.1128/AEM.01007-19

https://aem.asm.org/content/85/17/e01007-19.abstract?etoc

Kelly oysters brand Gigas Oysters recalled due to domoic acid

Posted on May 14, 2017 by Douglas Powell

One of the first science columns I ever wrote for a newspaper 36-years ago was about domoic acid in shellfish.

Everything old is new again.

According to the Canadian Food Inspection Agency DOM International Limited is recalling Kelly Oysters brand Gigas Oysters from the marketplace due to marine biotoxin which causes amnesic shellfish poisoning. Consumers should not consume and retailers, hotels, restaurants and institutions should not sell, serve or use the recalled product described below.

This recall was triggered by the company. The Canadian Food Inspection Agency (CFIA) is conducting a food safety investigation, which may lead to the recall of other products. If other high-risk products are recalled, the CFIA will notify the public through updated Food Recall Warnings.

There have been no reported illnesses associated with the consumption of this product.

This is what creativity looks like at its ugly peak (even though this was filmed with makeup and tricks 7 years after being written, it’s still the best vid)

STECs in shellfish, France

Posted on June 14, 2016 by Douglas Powell

Shiga toxin-producing Escherichia coli (STEC) and enteropathogenic E. coli (EPEC) strains may be responsible for foodborne infections in humans.

Twenty-eight STEC and 75 EPEC strains previously isolated from French shellfish-harvesting areas and their watersheds and belonging to 68 distinguishable serotypes were characterized in this study.

High-throughput real-time PCR was used to search for the presence of 75 E. coli virulence-associated gene targets, and genes encoding Shiga toxin (stx) and intimin (eae) were subtyped using PCR tests and DNA sequencing, respectively.

The results showed a high level of diversity between strains, with 17 unique virulence gene profiles for STEC and 56 for EPEC. Seven STEC and 15 EPEC strains were found to display a large number or a particular combination of genetic markers of virulence and the presence of stx and/or eae variants, suggesting their potential pathogenicity for humans. Among these, an O26:H11 stx1a eae-β1 strain was associated with a large number of virulence-associated genes (n = 47), including genes carried on the locus of enterocyte effacement (LEE) or other pathogenicity islands, such as OI-122, OI-71, OI-43/48, OI-50, OI-57, and the high-pathogenicity island (HPI). One O91:H21 STEC strain containing 4 stx variants (stx1a, stx2a, stx2c, and stx2d) was found to possess genes associated with pathogenicity islands OI-122, OI-43/48, and OI-15. Among EPEC strains harboring a large number of virulence genes (n, 34 to 50), eight belonged to serotype O26:H11, O103:H2, O103:H25, O145:H28, O157:H7, or O153:H2.

Molecular profiling of Shiga toxin-producing Escherichia coli and enteropathogenic E. coli strains isolated from French coastal environments

Appl. Environ. Microbiol. July 2016 vol. 82 no. 13 3913-3927, DOI: 10.1128/AEM.00271-16

Balière, A. Rincé, S. Delannoy, P. Fach and M. Gourmelon

http://aem.asm.org/content/82/13/3913.abstract?etoc

Increased action required to protect those with food allergies

Posted on April 28, 2016 by Douglas Powell

Our daughter has been diagnosed with a moderate shellfish allergy, which is a shame with all the great shellfish in and around Brisbane, but more importantly it means we carry an epi pen and know how to use it.

It’s made me more empathetic to those with severe allergies.

An independent review of the UK’s food system has concluded more action needs to be taken in order to better protect people with food allergies. That’s according to a report from a leading UK team of food safety experts, including Professor Chris Elliott from Queen’s University Belfast, a co-author of a paper published in The Royal Society of Chemistry’s journal Analyst, outlining a strategy to close the gaps in current processes for detecting and measuring allergens – substances in foods that can trigger an allergic reaction. The publication comes during the UK’s Allergy Awareness Week (25th April – 1 May).

Food allergy is a rapidly growing problem in the developed world, affecting up to 10 per cent of children and 2-3 per cent of adults. Allergic reactions can range from a mild runny nose, skin irritation or stomach upset to severe anaphylaxis, which can be fatal.

Food allergies have significant impact on quality of life and usually require lifelong avoidance of the offending foods. There are also burdens on health care, the food industry and regulators.

Professor Elliott and Professor Duncan Burns, Emeritus Professor at Queen’s Institute for Global Food Security, are among a team of experts led by Michael Walker from the Government Chemist Programme at LGC, which has outlined a ‘grand vision’ to address the key challenges in allergen measurement and analysis. They make a series of recommendations primarily addressed to the European Commission’s Health and Food Safety Directorate, DG Santé, aimed at securing a food chain which is reliable, resistant to fraud and ultimately safe for consumers.

Professor Elliott is a world-renowned expert on food fraud and traceability and led the independent review of the UK’s food system following the 2013 horsemeat scandal. He said: “The food supply chain is highly vulnerable to fraud involving food allergens, risking consumer health and reputational damage to the food industry. Cross-contamination during production, processing and transport is also a problem. While efforts have been made to improve food labelling and introduce the concept of threshold quantities for allergens, these depend on being able to accurately detect and quantify allergens in the first instance. Gaps in the current system mean that it is difficult to achieve this.

“This paper sets out a strategy to address those gaps and calls on the EC to take action in three particular areas. Firstly, the use of bioinformatics studies for modelling how best to predict what allergens present in foods, and specifically what quantities of these allergens, will adversely affect the health of someone with food allergies. Secondly, the development of reference methods which will provide a ‘gold standard’ for the detection and measurement of allergens in food. And thirdly, the production of reference materials which can support threshold decisions -samples of foods with known, controlled amounts of allergens present, to allow for checks on the accuracy of allergen testing methods.”

Significant international effort and an inter-disciplinary approach will be required to achieve these aims and protect those at risk of food allergies. Lead author of the report, Michael Walker from LCG said: “If we fail to realise the promise of future risk management of food allergens through lack of the ability to measure food allergens properly, the analytical community will have failed a significant societal challenge. Our recommendations are complex with associated resource demand but rarely has such an exciting interdisciplinary scientific endeavour arisen as a solution to a key socially relevant problem.”

The open access paper in Analyst is available at http://pubs.rsc.org/en/content/articlehtml/2016/an/c5an01457c?page=search.

Raw is risky: Taiwan regulators warn of food poisoning from shellfish

Posted on March 7, 2016 by Douglas Powell

The Taiwan Food and Drug Administration (FDA) yesterday urged people not to eat raw shellfish to avoid food poisoning, such as norovirus infection, as several recently reported cases of food poisoning were all caused by eating raw shellfish.

Raw shellfish, including raw clams and oysters, can easily be contaminated by norovirus or Vibrio parahaemolyticus in their growing environment, the agency said, adding that norovirus is one of the most common viruses that cause viral gastroenteritis.

The transmission of norovirus is primarily fecal-oral, and as few as 10 or less viral particles can cause an infection, Division of Food Safety official Hsu Chao-kai (許朝凱) said, adding that norovirus infection can cause an infected person to exhibit symptoms such as vomiting, stomach pain, watery diarrhea and, in some cases, a fever.

The agency said people should not risk their health to enjoy the taste of raw shellfish and urged the public to wash and cook shellfish thoroughly before eating.

35 sick: raw is risky in rising temperatures in BC

Posted on July 31, 2015 by Douglas Powell

A warning from the BC Centre for Disease Control about eating raw shellfish:

So far this summer, there have been an unprecedented number of shellfish-related illnesses thanks to the warm weather.

The majority of illnesses have been linked to eating raw oysters sourced in BC and served in restaurants.

Spokesperson Marsha Taylor says 35 people have become ill from eating the uncooked shellfish…

“We’re putting this message out both to the public that will also hit the restaurants and we’re also doing follow up with every restaurant to make sure they are aware of the issue and we’re inspecting the premises.”

Some illnesses have also been linked with raw oysters purchased or self-harvested.

Taylor says if you happen to get sick…

“People who are experiencing symptoms of the Vibrio Parahaemolyticus most often experience typical food-borne illness like nausea and vomiting, headaches, and feel pretty badly for a couple of days…but most people will recover on their own.”

To reduce risk of illness consumers are being told to eat only cooked shellfish.

Inconceivable: UK shellfish farms closed amid sewage fears

Posted on July 24, 2015 by Douglas Powell

Sewage bacteria, thought to be E. coli, was found in the Camel Estuary, St Austell and Falmouth Bays, said the Food Standards Agency (FSA).

The Shellfish Association of Great Britain contests the move, claiming the test results are “inconceivable”.

The FSA said it was “monitoring the situation” but the shellfish beds would remain closed.

David Jarrard, of the Shellfish Association, said: “The industry treats food safety as paramount.

“But I was astonished with these results, we have never seen any of this magnitude before and I just don’t believe them.

“The results we have had are akin to raw sewage and for that to happen in one river might be possible but to find it in all these areas is inconceivable.”

It has asked the FSA to disregard the results while an investigation takes place.

An FSA spokesperson said: “The results are unusually high which is why they require further investigation.

“We are monitoring the situation by taking further samples but until we have evidence to the contrary the beds must remain closed to protect public health.”

I don’t eat raw oysters: Iron overload disease causes rapid growth of Vibrio

Posted on January 14, 2015 by Douglas Powell

Every summer, the news reports on a bacterium called Vibrio vulnificus found in warm saltwater that causes people to get sick, or die, after they eat raw tainted shellfish or when an open wound comes in contact with seawater.

People with a weakened immune system, chronic liver disease or iron overload disease are most at risk for severe illness. Vibrio vulnificus infections in high-risk individuals are fatal 50 percent of the time.

Now, researchers at UCLA have figured out why those with iron overload disease are so vulnerable. People with the common genetic iron overload disease called hereditary hemochromatosis have a deficiency of the iron-regulating hormone hepcidin and thus develop excess iron in their blood and tissue, providing prime growth conditions for Vibrio vulnificus.

The study also found that minihepcidin, a medicinal form of the hormone hepcidin that lowers iron levels in blood, could cure the infection by restricting bacterial growth.

The early findings were reported online Jan. 14 in the journal Cell Host and Microbe.

“This is the first time that the association of hepcidin deficiency and susceptibility to Vibrio vulnificus infection was tested,” said senior author Dr. Yonca Bulut, a clinical professor of pediatrics at Mattel Children’s Hospital at UCLA and a researcher with the UCLA Children’s Discovery and Innovation Institute. “The dramatic effectiveness of the new treatment, even after the infection was established, was impressive.”

To conduct the study, researchers compared the fatality of Vibrio vulnificus infection in healthy mice with mice that lacked hepcidin, modeling human hereditary hemochromatosis. The results showed that the infection was much more lethal in hepcidin-deficient mice because they could not decrease iron levels in the blood in response to infection, a process mediated by hepcidin in healthy mice.

Giving minihepcidin to susceptible hepcidin-deficient mice to lower the amount of iron in the blood prevented infection if the hormone was given before the Vibrio vulnificus was introduced. Additionally, mice given minihepcidin three hours after the bacterium was introduced were cured of any infection.

Hereditary hemochromatosis is a genetic disease that causes the body to absorb and store too much iron. It affects as many as 1 in every 200 people in the United States. Since it can take decades for the body to store damaging levels of iron, many people may not be aware that they have the disease until signs of the condition begin to appear later in life.

The co-directors of the UCLA Center for Iron Disorders, Dr. Tomas Ganz, a professor of medicine and pathology at the David Geffen School of Medicine at UCLA, and Elizabeta Nemeth, a professor of medicine at UCLA, led the invention of minihepcidins at UCLA. Minihepcidins are being developed for treatment of iron-overload disorders, such as hereditary hemochromatosis and Cooley’s anemia. The use of minihepcidin to treat potentially lethal infections is a possible new application.

“We found that hepcidin is required for resistance to a Vibrio vulnificus infection,” said the study’s lead author Joao Arezes, a visiting graduate student from the University of Porto in Portugal. “The development of the treatment tested in mouse models could reduce the high mortality rate of this disease.”

The next stage of research is to understand why Vibrio vulnificus bacteria become so lethal when iron levels are high, and to learn which other microbes respond similarly to excess iron.

Journal reference: Cell Host and Microbe

Provided by University of California, Los Angeles

Raw and risky: Hepatitis A cluster linked to oysters and clams in Taiwan

Posted on December 9, 2014 by Douglas Powell

Our friends are off to China and Indonesia at the end of the week (start of summer holidays) so we’re having them over for dinner tomorrow, where I’ll offer up a seafood pasta (I simply cannot compete with Susan’s stir-fry and other Chinese dishes).

But with the holiday season approaching, there will – like no raw egg dishes — be no raw shellfish served in this house.

The Taiwan CDC reports 30 indigenous cases of Hepatitis A from Oct. to Nov. 2014, in which more than 80 percent of the patients required hospitalization for their illness.

According to the epidemiological investigation, most patients consumed raw bivalves such as oyster and clams during the disease incubation period.

This has prompted the Taiwan CDC to remind the public to pay attention to personal dietary hygiene and consume only thoroughly cooked bivalves.

Bivalves such as oysters and clams concentrate the pathogens that are present in harvest waters.

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