Trichinella spiralis

The worm that causes trichinosis. Trichinella spiralis larvae can infest pigs and wild game, hibernating in muscle tissue within a protective cyst. Trichinosis can be correspondingly defined as a disease caused by eating raw or undercooked pork or wild game infested with the larvae of the worm Trichinella spiralis. When a human or an animal eats meat that contains infective Trichinella cysts, the acid in the stomach dissolves the hard covering of the cyst and releases the worms. The worms pass into the small intestine and, in 1-2 days, become mature. After mating, adult females lay eggs. Eggs develop into immature worms, travel through the arteries, and are transported to muscles. Within the muscles, the worms curl into a ball and encyst (become enclosed in a capsule). Infection occurs when these encysted worms are consumed in meat.

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the species that is the usual etiologic agent of trichinosis; it is small, usually around 1.5 mm long, and is found coiled in cysts in the muscles of bears, rats, pigs, and humans. When infected meat is eaten without proper cooking, the cyst dissolves and the parasite matures and deposits its larvae in the deep mucosa; larvae then enter the lymphatics, are carried to all parts of the body, and again encyst. Called also pork worm.

Trichinella spiralis nurse cell–larva complex (A) and larva migrating outward in muscle from a capillary (B).