Paragonimiasis is caused by lung fluke infection from eating raw or undercooked crabs or crayfish. It typically causes lung symptoms but can spread to the brain. While rare, cases have occurred in the US Midwest from eating raw crayfish. Diagnosis involves identifying eggs in sputum or biopsy samples. Infection is treatable with prescription medication. Risk of infection comes from dishes with undercooked freshwater shellfish in Asia and Central/South America. Prevention involves thoroughly cooking crabs and crayfish before eating.

1. Fitango Education
Health Topics
Paragonimiasis
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2. Overview
Paragonimus is a lung fluke (flatworm) that infects
the lungs of humans after eating an infected raw or
undercooked crab or crayfish. Less frequent, but
more serious cases of paragonimiasis occur when
the parasite travels to the central nervous system
instead of the lungs.
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3. Overview
Although rare, paragonimiasis has been acquired
in the United States, with multiple cases reported
from the Midwest. Treatment for paragonimiasis is
available from a physician after an accurate
diagnosis is made.
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4. Symptoms
Adult flukes living in the lung cause lung disease
that may never be diagnosed or is thought to be
tuberculosis. After 2-15 days, the initial signs and
symptoms may be diarrhea and abdominal pain.
This may be followed several days later by fever,
chest pain, and fatigue. The symptoms may also
include a dry cough initially, which later often
becomes productive with rusty-colored or blood-
tinged sputum on exertion.
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5. Diagnosis
The infection is usually diagnosed by identification
of Paragonimus eggs in sputum. The eggs are
sometimes found in stool samples (coughed-up
eggs are swallowed). A tissue biopsy is sometimes
performed to look for eggs in a tissue specimen.
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6. Diagnosis
Specific and sensitive antibody tests based on P.
westermani antigens are available through
CDC, and serologic tests using a variety of
techniques are available through commercial
laboratories.
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7. Treatment
Paragonimus infections are treatable by your
health care provider. Prescription medications are
available.
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8. Risks
Several species of Paragonimus cause most
infections; the most important is P. westermani,
which occurs primarily in Asia including China, the
Philippines, Japan, Vietnam, South Korea, Taiwan,
and Thailand. P. africanus causes infection in
Africa, and P. mexicanus in Central and South
America. Specialty dishes in which shellfish are
consumed raw or prepared only in vinegar, brine,
or wine without cooking play a key role in the
transmission of paragonimiasis. Raw crabs or
crayfish are also used i
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9. Risks
Although rare, human paragonimiasis from P.
kellicotti has been acquired in the United States,
with multiple cases from the Midwest. Several
cases have been associated with ingestion of
uncooked crawfish during river raft float trips in
Missouri.
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10. Prevention
Never eat raw freshwater crabs or crayfish. Ensure
crabs and crayfish are cooked properly. Travelers
should be advised to avoid traditional meals
containing undercooked freshwater crustaceans.
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