of
Trichinella. After exposure to gastric acid and pepsin, the larvae are
released
from the cysts and invade the small bowel mucosa where they develop into
adult worms
(female 2.2 mm in length, males 1.2 mm; life span in the small bowel: 4
weeks). After 1 week, the females release larvae
that migrate to the striated muscles where they encyst
.
Trichinella pseudospiralis, however, does not encyst. Encystment is
completed in 4 to 5 weeks and the encysted larvae may remain viable for
several years. Ingestion of the encysted larvae perpetuates the cycle.
Rats and rodents are primarily responsible for maintaining the endemicity of
this infection. Carnivorous/omnivorous animals, such as pigs or bears, feed
on infected rodents or meat from other animals. Different animal hosts are
implicated in the life cycle of the different species of Trichinella.
Humans are accidentally infected when eating improperly processed meat of
these carnivorous animals (or eating food contaminated with such meat).