About Paragonimiasis

Key points

  • Paragonimus is a parasitic lung fluke that infects a person's lungs and causes paragonimiasis.
  • You can get paragonimiasis by eating raw or undercooked crabs or crayfish.
  • Initial symptoms include diarrhea and abdominal pain, followed by fever, chest pain, and fatigue.
  • Treatment is available through prescription drugs.


Paragonimus is a parasitic lung fluke (flat worm). Cases of illness from infection occur after a person eats raw or undercooked infected crab or crayfish. The illness is known as paragonimiasis. Paragonimus infection also can be very serious if the fluke travels to the central nervous system, where it can cause symptoms of meningitis.


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 in traditional medicine practices in Korea, Japan, and some parts of Africa.

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.


Adult flukes living in the lung cause lung disease. 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. The symptoms of paragonimiasis can be similar to those of tuberculosis.

How it spreads

The infection is spread by eating infected crab or crawfish that is either, raw, partially cooked, pickled, or salted. The larval stages of the parasite are released when the crab or crawfish is digested. They then migrate within the body, most often ending up in the lungs. In 6 – 10 weeks, the larvae mature into adult flukes.


Never eat raw freshwater crabs or crayfish. Cook crabs and crayfish to at least 145°F (~63°C). Travelers should be advised to avoid traditional meals containing undercooked freshwater crustaceans.


The diagnosis is usually made by identifying Paragonimus eggs in the sputum or sometimes in the stool (from ingesting eggs after coughing them up, then passing the eggs in the stool).


Paragonimus infections, or paragonimiasis, are treated with medications prescribed by your healthcare provider.