What is Angiostrongylus cantonensis?

Angiostrongylus cantonensis (Ann-gee-o-stronge-uh-luss can-tun-en-sis) is a parasitic worm of rats. It is also called the rat lungworm. The mature (adult) form of the parasite is found only in rodents (it is not found in people). Infected rats pass immature forms (larvae) of the parasite in their feces. Snails and slugs get infected by ingesting the larvae in rat feces. These larvae mature in snails and slugs but do not become adult worms. The life cycle comes full circle when rats eat infected snails or slugs and the larvae further mature to become adult worms.

Can people get infected with this parasite?

Yes. People can get infected, under unusual circumstances. However, even if infected, most people recover fully without treatment.

How can people get infected?

People can get infected by eating raw or undercooked snails or slugs that are infected with this parasite. In some cultures, snails are commonly eaten. Some children, in particular, have gotten infected by swallowing snails/slugs “on a dare.” People also can get infected by accident, by eating raw produce (such as lettuce) that contains a small snail or slug or part of one.

Other ways of getting infected may include eating raw or undercooked freshwater prawns, crabs, or frogs. Of note, fish do not spread this parasite.

Can an infected person infect other people?

No.

In what parts of the world have people become infected with this parasite?

In many parts. But most of the known cases of infection have been in parts of Asia and the Pacific Islands. Some have been in other areas of the world, such as in the Caribbean.

Have cases of this infection occurred in the United States?

Yes. Cases have occurred in Hawaii (and other Pacific Islands). Very few cases have been reported in the continental United States. In 1993, a boy in New Orleans got infected by swallowing a raw snail “on a dare.” The type of snail he swallowed isn't known. He became ill a few weeks later, with muscle aches, headache, stiff neck, a slight fever, and vomiting. His symptoms went away in about 2 weeks, without treatment of the infection.

Can giant African land snails be infected with this parasite?

Yes. This type of snail, which can grow larger than a person's hand, is just one of many types that can be infected. But snails can be infected only if they have ingested contaminated rat feces. We don't know if any of the giant African land snails in the continental United States are infected.

Of note, these snails pose a major threat to agriculture because they multiply quickly and have ravenous appetites for plants and produce. It is illegal to own these snails without a special government permit. For more information about these snails, go to the United States Department of Agriculture's Web site on Giant African Snails.

What are the symptoms of infection with this parasite?

Some infected people don't have any symptoms -- or have only mild symptoms that don't last very long. Sometimes the infection causes a rare type of meningitis (eosinophilic meningitis). The symptoms can include headache, stiff neck, tingling or painful feelings in the skin, low-grade fever, nausea, and vomiting.

What should I do if I think I might be infected with this parasite?

You should see your health care provider, who will examine you and ask about any symptoms, travel, and exposures you've had (for example, to snails/slugs). You might have some blood tests, as well as tests for meningitis.

Does infection with this parasite need to be treated?

Usually not. The parasite dies over time, even without treatment. Even people who develop eosinophilic meningitis usually don't need antibiotics. Sometimes the symptoms of the infection last for several weeks or months, while the body's immune system responds to the dying parasites. The most common types of treatment are for the symptoms of the infection (such as pain medication for headache) rather than for the infection itself. Patients with severe cases of meningitis may benefit from some other types of treatment.

How can I keep from getting infected with this parasite?

Don't eat raw or undercooked snails or slugs. If you handle snails or slugs, wear gloves and wash your hands. Always remember to thoroughly wash fresh produce.