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Trichinosis is caused by the larvae (immature form) of a highly versatile parasitic roundworm, Trichinella spiralis. This parasite can infect virtually every meat-eating mammal. The parasite is especially common in rats and in swine that feed on raw-meat garbage.

Unlike some of the other parasitic roundworm diseases, trichinosis is not an intestinal infection in the usual sense. Symptoms are caused by the movement of the larvae from the intestines throughout the body, and also by their encystment (becoming enclosed in a capsule) in muscle tissue.

Typically, the life cycle of the parasite follows these steps:

  1. A person or an animal eats contaminated meat containing parasite larvae.
  2. Digestive juices from the stomach dissolve the capsule-like cyst and release the larvae.
  3. The larvae then enter the intestine where they mature into worms and mate.
  4. Female worms pass larvae into the bloodstream where they make their way through the capillaries (tiny blood vessels) into the muscle fibers.
  5. The larvae encyst in the muscle fibers, where they can live for a long time.

Last Updated June 21, 2013