Today, writes Peter O’Neill, we all rely on microbiologists and pathologists who stick their swabs into the nooks and crannies of cold storage warehouses and chill cabinets. These Micronauts travel the 'Global Consumer' highways from hook to plate, and from sea cage to smoked salmon picnic sandwiches.
The lengthening of the mass production food chain means that when something goes wrong the results can be widespread. This year’s SEAFOODplus gathering of EU researchers showed why it is worth keeping an up-to-date eye on which bugs are out there and how they can be tackled. These are the unseen enemies which can destroy your reputation…and your business - bugs which affect fish, not just humans.
The Chilean farmed salmon harvest this year has gone into freefall as millions of fish have been killed by infectious salmon anaemia. The basic cause is alleged to be poor sanitary conditions and over-use of antibiotics. According to The New York Times this is not just small backyard operators in trouble, but the likes of Marine Harvest which by early April had to to lay off 1,200 workers. The newspaper quoted a local fisherman as saying the salmon companies were taking away the wild fishermen’s “wealth” because the sea cages were contaminating the wider waters.
Some food risks can be tackled with early vaccination of farmed fish and permitted antibiotics. Other bugs can hit if there has been contamination in the processing factory by handlers or waste water. Accidental breaks in the cold chain and poor storage can mean rising temperatures encourage harmful bacterial or viral breeding in the product.
Aliens
Fishermen and estuary managers are already aware that alien species can arrive in a region and wreak havoc. Certain crabs and crayfish can knock out weaker local species. They can also bring threats from the bugs they carry. It is in the interest of the industry to work closely with port authorities to monitor long-distance freight vessels which bring in beasts and bugs on hulls or in their ballast. This is what tougher EU ballast controls are about – they are a common sense measure to stop aliens getting into local aqua networks where port and sea meet rivers and estuaries.
The level of international bug-spotting collaboration is apparent from, for example, the project for “Seafood: Enhanced Assessment of Bacterial Associated Contamination” (SEABAC). It involves the Centre for Environment Fisheries and Aquaculture in the UK, United Kingdom; Instituto Superiore di Sanità, Italy; Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), France; University of Santiago, Spain; National Research Institute on Agriculture and Fisheries, Portugal; and the Icelandic Fisheries Laboratories Iceland.
They are developing new, rapid methods to detect vibrio species (a type of bacteria, not a virus) in seafoods. Our Indian readers will recall to their cost that reports of vibrio cholerae in a shipment of frozen seafood caused a ban (which later the WHO said had been unnecessary) on Indian product into Europe. Jumpy EU inspectors, with poor data on the actual danger, caused a $400 million-dollar hit on Indian producers and exporters. But it took WHO took months to say there had been no public health risk and the financial damage was done.
The SEABAC team told experts in Copenhagen that vibrios are a significant cause of seafood-associated illness worldwide and focused on the three main pathogens. V. cholerae, v. parahaemolyticus, v. vulnificus which need a salinity of 5-25ppt and a temperature of 15-30ºC. V. parahaemolyticus and v. vulnificus are commonly found in temperate and tropical coastal waters worldwide. Infection can arise when contaminated shellfish are eaten raw or are undercooked. So, correct cooking can kill the beasties.
But it is the source of the bacterium which may show why frontline fishermen should always be on the lookout, and processors keep their eye on traceability when some low-priced 'bargains' are offered - they could be from an area where there has been an outbreak of sickness. V. parahaemolyticus in Chinese mitten crabs (Eriocheirsinensis) is a vibrio which originated from Fukien Province in China. The crabs are considered a rare delicacy to be consumed raw. It turned up in the UK through ballast water and has become an invading 'nuisance species' in the UK and Europe. Disembarking from the bilges it can travel great distances.
The science looks very complex, but basically the SEABAC team has developed new, faster tools which helped them show when there are “unusually high levels of V. parahaemolyticus and the crabs are concentrating the bacteria in their flesh”. There have been a growing number of illnesses reported across Europe but they are still small in number and the team says that while “Vibrios are responsible for a significant proportion of the EU rapid alerts for seafood – the public health significance of many is doubtful. Eating mitten crabs reduces their number and the risk but they need “thorough cooking”, the team says. This kind of knowledge is what helps avoid unnecessary scares.
Viral warning
Researchers from the University of Barcelona and IFREMER’s Nantes lab, are developing good, fast tests for detecting viruses in bivalve molluscs. The problem is that “… current EU standards do not specify the monitoring for viral pathogens…and monitoring of shellfish and shellfish beds rely solely on bacteriological parameters…Gastroenteritis and hepatitis A cases have been associated with the consumption of shellfish [even though they were monitored] through legal standards,” the team warned.
Danes from the National Institute of Aquatic Resources (DTU Aqua) and the Technical University of Denmark (DTU) are focusing on histamine fish poisoning which they say has become a “common seafood safety issue”. Implicated are finfish with >500 mg histamine/kg and the symptoms they produce are flushing, rash, headache, diarrhoea and vomiting. One parameter is storage time and products cited are fresh tuna, dried sardines, tuna in chilli sauce, cold-smoked tuna and tuna heated in flexible film.
Researchers from the Marine Institute in Ireland and IFREMER propose controlling the upstream risks from viruses in rogue sewage before they hit shellfish beds. This includes real-time monitoring (once a week) of virus risk, not only for E. coli, but the 'vomiting' Norovirus. Never mind cruise ships, it hit swathes of people across London this winter with infection through poor personal toilet hygiene. Fishermen need to do some shouting on land to stop this kind of pollution. As we write, privatised UK water companies are alleged to be overusing their storm drain overflows, so raw sewage is allegedly being pumped into rivers and sea estuaries - at more than 3,500 points around the UK.
