26 January, 2002 Coliform Update Reprint: Originally posted on the prawn listserve By DFO - 09 Jan 02 Information, Prawn and Shrimp, Coliform Bacteria Q: Is the presence of bacteria in prawns something new? A: Only our knowledge of the occurrence of coliform bacteria on prawns is new, as of 2001. Past checks did not indicate the presence of coliform bacteria. This year, a routine quality control check by the Canadian Food Inspection Agency found it to be present. That led to further investigation. Q: Are coliform bacteria commonly found in prawns? A: Faecal coliform bacteria are not produced in the digestive systems of crustaceans like they are in warm blooded animals. The presence of the bacteria indicates that human or animal waste is entering the water. Q: Did you find coliform bacteria or E. coli? A: We found both. E. coli is a type of coliform bacteria. Q: Coliform bacteria, is that E. coli? A: Coliform bacteria is the general croup of bacteria. Faecal bacteria is a type of coliform bacteria. E. coli is a type of faecal bacteria. They are found naturally in the digestive system of all warm blooded animals. Q: What is E. coli? A: The full name is Escherechia coli. It is a species of faecal coliform bacteria normally found in the digestive tract of all warm-blooded animals including domestic animals and wildlife. It is also found in high concentration within sewage/septic systems. E. coli exists as numerous strains; only a few are responsible for producing illness such as diarrhea. Q: Isn't E. coli dangerous? A: Most E. coli is natural in our digestive systems, and is not dangerous. However, one variant was associated with illness in eastern Canada. A set of prawn samples known to have coliform bacteria was further analyzed for that type of E. coli, and it was not present. Q: How contaminated are the prawns? A: Up to 30% of prawn samples in some areas had the detectable presence of coliform bacteria. 22% of prawn samples exceeded the detection limit of 20 MPN per 100 gm. Each sample consisted of 8 to 10 prawns, so the actual presence of bacteria may be considerably lower than this. For example, it may be that only 1 of the 8 or 10 prawns in the sample had been in contact with coliform bacteria. Only 7% of samples exceeded 400 MPN per 100 gm, which is an action level for the Canadian Food Inspection Agency, the level at which prawns require further treatment prior to export. Q: The results refer to "MPN per 100 gm or MPN per 100 ml". What is that? A: MPN is short for Most Probable Number, which is how the bacteriological analysis results are expressed. As the analysis is based on a series of dilutions, the results are estimates, or "Most Probable Number". Q: Was this unexpected? A: Yes, for prawns which are caught at depths. Coliform bacteria are common in near shore surface waters which are influenced by fresh water runoff, which may include bacteria from failing septic fields, or from farm sites, or from domestic animals or wild animals. So we typically find it in animals like clams and oysters, in affected areas. Salt water is a natural bactericide which kills coliform bacteria relatively rapidly, within hours. So we expect to find coliform bacteria in sea water, but not necessarily at depth and not associated with prawns. Q: Where was the bacteria found? A: This was first noticed on the Sunshine Coast, in waters offshore of Powell River and Lund. However, as the DFO sampling progressed, it was found in samples throughout the Gulf of Georgia, the Gulf Island and the Strait of Juan de Fuca. It has also been found in Prince Rupert harbour, and there are reports suggesting it may be present in areas between. Q: Is it only in the prawn head or gut? A: The Canadian Food Inspection Agency did some work testing heads and tails separately. In some cases, coliform bacteria were found in the head but not the tails. In other cases, the bacteria was found in the tails and not the head. Q: Is it associated with sewer outfalls? A: The presence of coliform bacteria in prawn and shrimp samples does not correlate to specific municipal discharges. Some higher levels of coliform bacteria were found in areas well removed from any sewer discharge. Q: Is it associated with cruise ships? A: There is no correlation of the location of coliform bacteria in samples, with cruise ship or other shipping routes. Q: Is it only found near population centres in the Gulf of Georgia? A: The majority of the sampling to date has been in the Gulf of Georgia. However, that does not mean that the presence of coliform on prawns is confined to this area. It only reflects the sampling pattern to date. Coliform bacteria can be found in the most remote areas of the coast, well removed from any human population influence, from wildlife. Q: Is this related to human pollution? A: We cannot tell if the bacteria is from human or non-human sources. Q: What does pelletized feed have to do with it? A: As a matter of convenience, many commercial prawn fishers use a pelletized fish feed for bait. Handy, easy to pack and so on. In recent years, at least one salmon farm feed manufacturer has prepared a variation of their product specifically for the commercial prawn and shrimp trap fishery. Early in the investigations, some fishers thought that pellet bait might be a source of the problem. This was not born out by the sampling. Although coliform bacteria can show up in some bait, it does not always show up in the prawns caught with that bait. And prawns have shown up with coliform bacteria, when the bait was clean. Finally, other shrimp species have shown up with evidence of coliform bacteria caught in trawl gear where no bait is used. When bait was tested, bait which included fish remains appeared to have coliform bacteria more often than bait which was strictly composed of pellets, although this pattern was not always consistent. Prepared properly, pellet bait consists of wheat, fishmeal and fish oil retorted at 190 deg. which would be sufficiently high to kill all coliform bacteria. Q: Has anyone got sick yet? A: No one has reported illness associated with eating prawns or other shrimp (except if they are allergic to seafood) this year or in any previous year, and it's not considered likely. The coliform bacteria are indicator organisms of unsanitation. Only a few varieties are known of health concern. Prawns have been tested for the variant that caused health concerns in eastern Canada, and it was not found. Coliform bacteria, and in particular E. coli is a naturally occurring bacteria present all of the time in the digestive tract of all warm blooded animals. In the same manner that we are not normally and usually ill even though our digestive tracts are full of coliform bacteria, the presence of coliform bacteria in the ocean or in seafood is not of itself an indication that illness will occur. Q: Why isn't there a closure? A: The coliform bacteria found in the marine environment is just an indicator, not an organism that directly causes illness. Q: Is this only found with prawns? A: No. Further sampling by DFO this fall has also found coliform bacteria on other shrimp species, humpback shrimp and sidestripe shrimp. Q: What is DFO doing? A: Improved vessel and plant sanitation and handling procedures were introduced to the commercial fishery in 2001. This information will be redistributed to all commercial fishing vessels and buying plants prior to the fishing season in 2002. Sampling has continued in the fall of 2001. We are expecting some additional results within a week at which time all results will be summarized and provided to other federal and provincial regulatory agencies which have responsibilities or an interest in this matter. We will act on any advice provided from federal or provincial health authorities, regarding advisories if that is considered that to be necessary. Q: Is DFO doing more sampling? A: Not at this time. We know t hat we can find it almost anywhere if we look hard enough. Our goal at this time is to provide advice about vessel sanitation and handling practices that will ensure or improve quality. Q: Does DFO have any advice for consumers or recreational fishers? A: Yes. It's recommendations that are common for all seafood. Consumers and restaurants are advised to purchase prawns from reputable sources so that you can be assured that they have been handled and stored properly to maintain quality before purchase. If you are recreational fishing, fish in areas that are not obviously influenced by man made discharges. Keep seafood refrigerated prior to consumption. Wash the prawns prior to consumption. Cooking will destroy bacteria. Quick facts: * 252 prawn and shrimp by trap "W" licence holders * commercial fishery valued at $29M landed value, $32M wholesale value in 2000 * 6th most valuable commercial fishery on Canada's Pacific coast in 2000 * 90 - 95% of commercial catch is exported to Japan * recreational fishery has increased dramatically in some areas near population centres, as salmon and rockfish fishing opportunity has declined. * 244 shrimp trawl "S" licences (some directed effort on sidestripe and humpback shrimp) * commercial fishery valued at $4M landed value, $7.9M wholesale value in 2000 * 128 samples were collected by DFO during the commercial prawn fishing season which ran from May to to July 18, 2001. This included 8 samples of hold water, 43 samples of bait and 77 samples of prawns. Each prawn sample consisted of 8 to 10 individual prawns. * Since then, 11 prawn samples have been collected from a pristine offshore area on the west coast of Vancouver Island * 37 samples of several shrimp species were collected in the Gulf, from a research trawl survey. 5 samples showed signs of coliform bacteria. Of these, 3 were sidestripe shrimp samples. The other 2 were prawns. 3 coonstripe shrimp samples had no evidence of coliform bacteria, but the sample quantity is insufficient to make a definitive statement for this species. * 16 samples have been collected in Prince Rupert Harbour of which 12 are tissue samples for humpback shrimp. 8 showed signs of coliform bactera. The other 4 are bait samples which did have coliform bacteria present. * 20 prawn samples have been collected from a DFO Science Stock Assessment research survey in Howe Sound and the results are expected shortly.