Animal Health Matters: A lesson in Trichinella
Last month, Sioux Falls was the staging area for an eye-opening experience for a unique group of public servants. The National Institute for Animal Agriculture, with the National Pork Board and the Pipestone system, brought state and federal public health officials here to tour sow farms, wean-to-finish barns, and pork processing plants. Most of the participants had not experienced modern pork production first hand like this. In the process, they learned about the steps producers and processors take to maintain the health of their animals and the safety of the food they produce.
A fractured ankle prevented me from joining the group for most of their activities; crutches and a walking boot are not conducive to shower-in/shower-out biosecurity procedures. But I did join the group for introductory conversations and a great pork (of course) supper.
Speaking of supper, my interest was piqued by a food-related point raised by the pork producers that night. The pork industry has been on the informational bandwagon about how well-cooked your pork chops and roasts should be.
You likely are familiar with the admonition to basically cook the heck out of pork because of the disease trichinellosis. Cooking your pork chop to an internal temperature of 160 degrees will take care of pathogens but also results in meat of shoe leather consistency – not the flavorful, juicy cut pork producers wish for their consumers. New guidelines advise that an internal temperature of 145 degrees is sufficient – the result being a much more enjoyable dining experience!
What changed? Pork food safety risks have changed. Trichinellosis isn’t really around anymore, thanks to modern pig management practices.
Trichinellosis is caused by a tiny parasitic worm that affects certain animal species. It’s only spread when carnivorous or omnivorous animals consume an infected animal. In old-fashioned pig raising, this commonly occurred when outdoor pigs ate infected rats and mice that entered their enclosures. In these rodents, the Trichinella worm took up residence in their muscle tissue as immune system-resistant cysts. When that muscle tissue is consumed by another animal, the worms activate and migrate into that animal’s muscles. If that other animal is a pig, the cysts set up in the pig’s muscle tissue.
Trichinella cysts in a rodent or pig don’t make those species sick. But if they develop in a person, severe illness can result. As the worms migrate through the intestinal tract, digestive symptoms common to many foodborne illnesses can result. Once in the muscle, eye and face swelling, fever, and bad body aches can result, with severe complications in some affected people.
Pork is no longer considered a source of human Trichinella infections because pigs are predominantly raised in confinement nowadays: tighter controls on buildings and feed supplies mean that modern pigs just aren’t exposed to the parasite anymore. As a result, cooking pork to high temperatures is no longer necessary.
(Ground pork should still be cooked to 160 degrees – not because of Trichinella, but because of other potential foodborne pathogens that similarly affect ground beef).
Despite the parasite’s elimination from confinement-raised pigs, human trichinellosis still occurs. The source for most of these illnesses is a different kind of food source – bear meat!
A recent outbreak of trichinellosis affecting six people occurred right here in South Dakota. On the menu for a family reunion was bear meat obtained from a family member’s Saskatchewan hunting trip. Trouble was, the bear meat was served quite undercooked to the guests before the cook realized it. Three of the sick people ended up in the hospital, where it took considerable time for doctors to diagnose the illness.
Being omnivorous, bears pick up Trichinella from the other animal species they dine on. Some estimate up to 24% of black bears in Canada and Alaska are infected. The hunter followed advice to inactivate any cysts by freezing the bear meat prior to cooking, however the Trichinella species common to bears happens to be very resistant to freezing.
The reduction of pork-related trichinellosis is a pertinent example of how modern swine confinement and management practices have not only aided animal health, but our risk of foodborne illnesses as well. So take that juicy pork loin off the grill when it hits 145 degrees. But leave the bear meat on until 165!
Russ Daly, DVM, is the Extension Veterinarian at South Dakota State University. He can be reached via e-mail at[email protected] or at 605-688-5171.
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