Dr Bill Doré, of the Marine Institute, Galway, talks about the productive work being done to tackle the issue of shellfish contamination.
Shellfish is a popular choice for restaurant-goers, particularly in seaside towns and villages, but it can be one of the more high-risk food items. Thankfully, in the Republic of Ireland (ROI), there is an organisation dedicated to testing shellfish for viruses.
Dr Bill Doré is the Team Leader of the National Reference Laboratory in the Marine Institute in Galway, which focuses on the microbiological monitoring of shellfish. He moved to ROI from the UK in 2004 and has almost 30 years of experience in this field.
He explains: “We provide support for the industry in terms of testing for viruses in shellfish. We’re also involved in running the programme for E. coli testing in shellfish, which is used to classify shellfish production areas, and environmental monitoring for bacteria. Furthermore, we provide advice to the industry and the competent authorities in this area including the Sea-Fisheries Protection Authority (SFPA) and Food Safety Authority of Ireland (FSAI).”
The team offer food producers testing and advice on management procedures in order to control the risks associated with shellfish and reduce the chance of contamination.
“I guess the first thing to stress is that generally the shellfish that are produced in ROI are of a good standard; they’re pretty clean and most of the time don’t cause any problems. It’s not a big issue here,” Bill says. “However, the fact is that shellfish – and we’re talking about bivalve shellfish, so oysters and mussels – they filter feed, so they sit in the water and basically they filter anything in that water.
“The issue is then, like all countries around the world, we have a problem with what happens to human waste. Sewage does get discharged into the coast and while it’s usually treated, it is untreated at times (this usually happens when there’s excessive rainfall and there’s an overflow of the cisterns). Of course, sewage contains a lot of microbiological bacteria and viruses from the human population. As a result, shellfish can become contaminated with what can be human pathogens.
“The main problem we see from time to time is contamination with viruses which can cause illnesses. In particular, the main virus is norovirus, which gives you vomiting and diarrhoea. It’s a gastrointestinal illness and it’s fairly mild but can last 48 hours or so. It’s not a particularly significant illness but it’s very common. We seem to have a particular problem with this virus because it binds specifically to the shellfish, and it tends to be a problem with oysters because they’re eaten raw.”
While contamination can and does happen, Bill acknowledges the fact that there is a greater risk in other countries: “Potentially any virus or bacteria that is in sewage can end up in shellfish and could potentially be a risk, but in general we don’t see illness. In other countries, where it’s endemic, hepatitis A virus is also seen, but we don’t see it here because it’s just not really present in the population.”
This practical issue is exacerbated by the fact that there is currently no regulation for viruses in shellfish, as Bill explains: “It’s been a sort of emerging issue over the past 10 years and until recently we haven’t had particularly good methods to detect viruses in shellfish. That’s why it’s still an area that isn’t very well controlled at a regulatory level, although in the EU there’s now quite a lot of progress being made towards trying to implement a standard for shellfish. We are actually involved in a survey, along with lots of other countries in Europe, which looks at the prevalence of norovirus in shellfish across Europe and that’s all being moved towards regulation.
“But in the absence of regulation, there’s still a problem for quality control and quality assurance for producers.
Obviously, from their own point of view, it’s not good for business if they’re making customers sick. They’re keen to implement procedures and testing to ensure that they’re producing a safe product and also because a lot of our shellfish is being exported to other countries. There’s a lot of trade to the Far East, China and Hong Kong, where they have implemented testing and so there’s always the risk that producers will send products, they’ll get tested and rejected – that can be very costly. So we have been, and are, working with producers, doing testing for them for norovirus and that’s happening when they’re getting ready to send them.”
This testing process can also reveal trends and help shape processes to tackle the issues, says Bill: “For instance, norovirus is a particular problem in the winter so, during that time, we’ve helped one producer in particular to select another, less contaminated site. Basically, he moves shellfish there during the winter so that they’ll be less contaminated.
“There’s also a process called depuration where shellfish are put into tanks of clean sea water onshore and allowed to purge themselves of contaminants. This doesn’t work too well for viruses, but you can improve it by increasing the time and temperature of that process. It can help to reduce, to some extent, the level of virus.”
Another piece of advice that Bill suggests is that food business operators introduce their own risk management procedures. “There’s a bit of a grey area because, as I mentioned, there is no standard and there is no definite level that is considered a risk that’s definitely going to make you sick. The test that we use is a molecular method and when we detect the virus, we can’t tell from that test whether it’s infectious or not infectious, so technically the test can pick up ‘dead virus’ if you like.”
Bill believes that the ROI is approaching the topic carefully and thoroughly: “I think, because we’re exporting a lot and because we have this test available, there’s probably more testing going on here than in many other countries. This extra quality control is a very positive thing.
“There’s also close cooperation between ourselves, the FSAI, SFPA and industry. There’s a body that meets quite regularly called the Molluscan Shellfish Safety Committee as well and what we do is advertised through it. More and more producers now are asking for testing.”
While it is clear that more is needed in terms of official standards and regulations in this industry, it seems that working together is getting results.
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