UBS microbiologist Kevin Allen led the study, which drew on purchases from seven large chain stores and 10 small retailers in the Vancouver metro area, including such products as lox, smoked tuna, candied salmon and fish jerky.
Their finding, published in the journal Food Microbiology, found that listeria was present in 20 percent of the ready-to-eat fish products, and of these five percent had the more virulent variety of listeria monocytogenes.
Allen said that while the listeria monocytogenes levels in the ready-to-eat fish products met federal guidelines, the bacteria can multiply during handling and storage, particularly toward the end of shelf life.
Additional handling of ready-to-eat foods in stores, such as slicing, weighing and packaging may increase the potential for cross-contamination” he said. “While listeria bacteria can be killed by high heat, most people eat these fish products without further cooking.”
Allen said pregnant women, the elderly and anyone with a compromised immune system should be aware of the health risks.
The problem is not with the fish itself, which arrives at processing facilities uncontaminated. The bacteria listeria can be picked up at a processing facility if it is not properly cleaned.
Two Alaska seafood processors interviewed for this story said the industry is well aware of the problems listeria can pose and take steps to avoid it, including routine sanitizing of all surfaces, swab tests and sending samples of product out for testing.
The standard procedure is wet down, wash down, soap down, rinse down and then sanitize, said one processor, speaking on condition of anonymity. There is rigorous adherence to protocols so that the listeria doesn’t show up in the facility. His facility is also frequently inspected, he said, by municipal, federal and state officials.
Leader Creek Fisheries’ Norm Van Vactor said the company’s plant does such cleaning and sanitizing routinely, as well as swabbing and testing product for listeria on a very systematic schedule during the fishing season. The environmental testing of the fish itself is done by a fisheries laboratory in Seattle, he said, while the quality assurance staff at Leader Creek oversees sanitizing of facilities.