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Syn:
Trichinellosis,
or trichiniasis
Trichinosis, an infection by the nematode Trichinella spiralis
, is most common in eastern and central Europe, North America, and
Central and south America.
Although it prevails in areas where pork is eaten,
many animals, including dogs, cats, rats, bears, foxes, and wolves,
are reservoirs of infection.
Humans become infected by eating
undercooked or raw meat containing encysted larvae, mainly pork.
The
cysts located in striated muscle, are digested , liberating larvae
that mature to adult worms that attach to the wall of the small
intestine.
Female worms there liberate larvae that invade the
intestinal wall, enter the circulation, and penetrate striated muscle,
where they encyst and remain viable for years.
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The clinical features are highly variable, depending
on the number of larvae ingested, and patients may be asymtomatic or
die of a fulminating disease.
In subclinical disease the only sign is
eosinophilia.
The invasion of muscle by the larvae is associated with
muscle pain, swelling of the eyelids and facial edema, eosinophilia,
and pronounced fever.
Respiratory and neurologic manifestatations may
appear.
Fatal cases are usually attributed to a severe myocarditis.
During the chronic phase of the disease the symptoms gradually
attenuate.
On invasion of the muscle the
larvae cause inflammation and destruction of muscle fibres. A fibrous
hyaline layer develops around a single coiled larva. Histiocytes and
giant cells may surround the cyst, which eventually calcifies.
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The
most frequently involved muscles are those of the limbs, diaphragm,
tongue, jaw, larynx, ribs and eye.
Larvae in other organs, including
the heart and brain, cause edema, necrosis, and focal infiltration of neutrophils, eosinophils, and lymphocytes, but they do not encyst.
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The
diagnosis is made by identifying larvae in muscle biopsies or by
serologic tests.
Antihelminthic drugs remove adult worms from the
intestine.
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