Trichinella spiralis

The species Trichinella spiralis is an important parasite, occurring in rats, pigs, and humans, and is responsible for the disease trichinosis. It is sometimes referred to as the "pork worm" due to it being found commonly in pork products that are undercooked.

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Maturity

The small adult worms mature in the intestine of an intermediate host such as a pig. Each adult female produces batches of live larvae, which bore through the intestinal wall, enter the blood (to feed on it) and lymphatic system, and are carried to striated muscle tissue. Once in the muscle, they encyst, or become enclosed in a capsule.

Larvae encysted in the muscles remain viable for some time. When the muscle tissue is eaten by a human, the cysts are digested in the stomach; the released larvae migrate to the intestine to begin a new life cycle. Female trichina worms live about six weeks and in that time may release larvae. The migration and encystment of larvae can cause fever, pain, and even death because of their potential to eat living tissue. One of the classic signs of Trichinella spiralis infection is a combination of splinter hemorrhages (not to be confused with those of bacterial endocarditis) and periorbital edema (eye swelling). Trichina are classified in the phylum Nematoda.