USDA recently updated its webpage on Trichinella, and this provides a nice reference on the topic. I thought it would be good to post this as well as an op-ed column in the NY Times on Trichinella in free range pigs (2009). In the 1930s, there were hundreds of cases per year that were reported (although it was not a reportable illness in many states). An estimate made from autopsies indicated that the level in the US population may have been as high as 12% (ref below). In the past decade, there have only been a handful of cases, mostly related to wild game, specifically bear. Much of this is due to industry practices and veterinary inspections. While there are some that refuted the NY Times piece based upon the lack of Trichinella cases related to free range pigs, in theory, it seems that if pigs are allowed to free range, there is potentially a higher risk of these pigs encountering this parasite (through the eating on infected rats or the feces of infected animals.)
While the mortality rate is low, symptoms of trichinosis can range from mild to severe.
“Nausea, diarrhea, vomiting, fatigue, fever, and abdominal discomfort are the first symptoms of trichinosis. Headaches, fevers, chills, cough, eye swelling, aching joints and muscle pains, itchy skin, diarrhea, or constipation follow the first symptoms. If the infection is heavy, patients may experience difficulty coordinating movements, and have heart and breathing problems. In severe cases, death can occur. The acute phase occurs after the mature warm lays eggs in the small intestine and these eggs hatch into larvae which enter the bloodstream and travel to muscle tissue within the body, such as the diaphragm. There they become encysted.
USDA’s review of Trichinella
A Focus on Trichinella -- Updated Version
A primer on trichinosis from CDC
A 1938 survey of trichinosis in the US
2009 NY Times Op-Ed on free range pigs and Trichinella