Trichinella spiralis, or the pork worm as it is sometimes called, is a nematode parasite which can infest humans as well as pigs and rats, as well as a range of other carnivores (bears, foxes and some cats can also carry the worm). Larvae bore through the host's intestinal wall, enter and feed on the bloodstream. The bloodstream and lymphatic system will eventually carry them to striated muscle tissue, and there they become encysted, enclosing themselves in a hard capsule of tissue.
As an infestation develops, trichinella spiralis can cause the disease trichinellosis in humans, which can be fatal in cases of severe infection where the worms get into the central nervous system. In general, however, the parasites tend to mass and breed in the intestines, leading to all the symptoms of nausea, heartburn and diarrhea that one might expect from such an event. According to trichinella.org, symptoms of trichinellosis can begin to appear after just twelve hours following the consumption of infected meat, with the exact incubation time dependent on the quantity of trichinella spiralis ingested.
The trichinella group are among the smallest nematode parasites that affect humans. Males average 1.5mm in length, with female worms about twice that size. The female worms have a lifespan of approximately six weeks, and in that time can produce anything up to 1,500 larvae. As the larvae migrate through the host's circulatory system, they can find their way into delicate organs which can also lead to death in humans from myocarditis or encephalitis.
Trichinellosis is now considered endemic to Japan and China, but has also been reported in Lebanon, Korea and in isolated cases in parts of Europe and the United States. As of early 2011, trichinella spiralis has had a draft of its genome published, and research continues for a method to vaccinate humans against this aggressive and harmful parasite.
The 'pork worm' got its nickname through its association with being spread among the human population via undercooked pork products. It should be self-evident that anyone seeking to limit their risk of infestation with trichinella spiralis, or any nematode parasite, should make sure that any pork products they consume are cooked through thoroughly prior to eating.
Infestation with trichinella spiralis is very serious, and anyone who thinks they may be hosting the parasite should speak to a medical practitioner immediately. Diagnosis is often confirmed via a muscle biopsy of encysted larvae, and treatment can be an unpleasant affair involving antihelmintics to destroy the worms themselves, and steroids (to reduce pain cause by larvae migrating into muscle tissues). The trichinella spiralis is certainly a parasite to be avoided at all costs.