Ask A Maui Doctor: What Do I Need to Know About Rat Lungworm?
Doctors at Minit Medical answer some of the questions submitted by readers.
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Below are a series of questions regarding Rat Lungworm.
Q: What is Rat Lungworm (Angiostrongylus cantonensis)?
A: Angiostrongylus cantonensis is a parasitic worm of rats. It is also called the rat lungworm. The adult form of the parasite is found only in rodents. Infected rats pass larvae of the parasite in their feces. Snails and slugs get infected by ingesting the larvae. These larvae mature in snails and slugs but do not become adult worms. The life cycle is completed only if the rat eats the infected snails or slugs and the larvae further matures 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 under cooked snails or slugs that are infected or by eating raw produce that contains a small piece of a snail or slug or slime.
Certain animals such freshwater shrimp, crabs, or frogs, have been found to be infected with larvae of the parasite. It is possible that eating under cooked or raw animals that are infected could result in people becoming infected, though the evidence for this is not as clear as for eating infected snails and slugs. Of note, fish do not spread this parasite.
Can an infected person infect other people?
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 and Africa.
Have cases of this infection occurred in the United States?
Yes. Cases have occurred in Hawaiʻi (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.
What are the signs and 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. The skin may feel itchy and can become extremely sensitive to touch.
What should I do if I think I might be infected with this parasite?
You should see a medical provider as soon as possible. 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 or medications to reduce the body’s reaction to the parasite, 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?
Extreme caution is your best protection. Don’t eat raw or under cooked snails or slugs, frogs or shrimp/prawns. If you handle snails or slugs, wear gloves and wash your hands. Always remember to thoroughly wash fresh produce. If you cannot be sure the produce is carefully washed then you can avoid eating uncooked vegetables. Rat lungworm affects everyone living in Hawaiʻi, whether you buy your produce at Costco or at the local farmers’ market.
Take more time with curly leafy vegetables, wash leaves individually. Some people advise soaking veggies in grapefruit seed extract, hydrogen peroxide, salt water, etc., but there has been no research done to show that any of these will kill the parasite. Check pineapple tops or twist tops off just above the leaf base and leave outside.
Animals can also get rat lungworm. There have been reports of people’s cats and horses contacting it.
Flatworms prey on the semi-slug and it is suspected that they may carry even higher loads of parasites. They easily hide in leaves or tight heads of produce and their soft bodies fall apart into small pieces when handled or under water pressure. Cooking food will kill the parasite however the exact time/temperature has not been scientifically determined. Err on the side of caution.
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If you think you may have a medical emergency, call your doctor or 911 immediately. Reliance on any information provided by in this article is solely at your own risk.