(trichinosis) is caused by nematodes (roundworms) of the genus
Trichinella. In addition to the classical agent T. spiralis
(found worldwide in many carnivorous and omnivorous animals), several
other species of Trichinella are now recognized, including T.
pseudospiralis (mammals and birds worldwide), T. nativa
(Arctic bears), T. nelsoni (African predators and scavengers),
and T. britovi (carnivores of Europe and western Asia).
acquired by ingesting meat containing cysts (encysted larvae)
Trichinella. After exposure to gastric acid and pepsin, the
larvae are released
the cysts and invade the small bowel mucosa where they develop into
2.2 mm in length, males 1.2 mm; life span in the small bowel: 4 weeks).
After 1 week, the females release larvae
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).
common in parts of Europe and the United States.
may be asymptomatic. Intestinal invasion can be accompanied by
gastrointestinal symptoms (diarrhea, abdominal pain, vomiting). Larval
migration into muscle tissues (one week after infection) can cause
periorbital and facial edema, conjunctivitis, fever, myalgias, splinter
hemorrhages, rashes, and blood eosinophilia. Occasional
life-threatening manifestations include myocarditis, central nervous
system involvement, and pneumonitis. Larval encystment in the muscles
causes myalgia and weakness, followed by subsidence of symptoms.
The suspicion of
trichinellosis (trichinosis), based on clinical symptoms and
eosinophilia, can be confirmed by specific diagnostic tests, including
antibody detection, muscle biopsy, and microscopy.
Several safe and
effective prescription drugs are available to treat trichinellosis.
Treatment should begin as soon as possible and the decision to treat is
based upon symptoms, exposure to raw or undercooked meat, and laboratory
test results. Steroids are used for infections with severe symptoms,
plus mebendazole*, with albendazole* as an alternative.
* This drug is
approved by the FDA, but considered investigational for this purpose.