Paragonimus FAQs


What is Paragonimus?

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.

Where is Paragonimus found?

Paragonimus westermani and several other species are found throughout eastern, southwestern, and southeast Asia; (including China, the Philippines, Japan, Vietnam, South Korea, Taiwan, and Thailand). P. africanus is found in Africa, and P. mexicanus in Central and South America. There are several species of Paragonimus in other parts of the world that can infect humans. P. kellicotti is found in the midwestern and southern United States living in crayfish. Some human cases of infection have been associated with eating raw crayfish on river raft trips in the Midwest. Paragonimus has caused illness after ingestion of raw freshwater crabs.

How is Paragonimus transmitted?

The infection is transmitted 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.

What are the signs and symptoms?

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 is Paragonimus infection diagnosed?

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).

Is Paragonimus infection contagious?

No. Paragonimus infection is not contagious.

Is there treatment?

Yes, there is treatment. Once the diagnosis is made, effective treatment for paragonimiasis is available from a physician.

How can I prevent Paragonimus infection?

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.

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Page last reviewed: September 18, 2020