What Is Rat Lungworm?

Medically Reviewed by Brunilda Nazario, MD on June 26, 2023
Written by Kristen Fischer
5 min read

Whether you’re eating snails as part of a meal or you swallow a slug on a dare, you may be prone to get rat lungworm. Though it’s rare and most people get better without treatment, this parasite can cause an infection. 

Rat lungworm is a parasitic worm that infects rats. It’s also called Angiostrongylus cantonensis. The worms live in the rats. The worms reproduce in the rat’s pulmonary arteries. They only develop to adult form in the rat. (In other animals, the larvae or younger forms of the worms live and then die off.)

When a human gets this parasite, it can cause a disease known as angiostrongyliasis, or neural angiostrongyliasis (NAS). Some people call this rat lungworm disease.

Being infected with rat lungworm can lead to a rare disease called eosinophilic meningitis. This can be mild and you can recover, but severe cases can be deadly. This form of meningitis is not contagious.

There were about 12 cases of rat lungworm disease in the U.S. between 2011 and 2017, the CDC reports.

 

When a rat is infected, it passes rat lungworm larvae through its poop. If snails and slugs feed on the poop, they eat the larvae and can get infected. The larvae can mature in snails and slugs, but they don’t turn into adult worms – those are only found in the rats. Rats may eat infected slugs or snails too, and then the larvae go through the life cycle to become adult worms.

When a person eats an animal, produce, or water infected with the rat lungworm parasite, it can cause rat lungworm disease. This affects your central nervous system.  

 

For the most part, rat lungworm occurs in the tropics and subtropical areas of the world.

It’s common in South and Southeast Asia, where experts think it originated. Rat lungworm also occurs in China, Japan, Brazil, Australia, the Caribbean, Taiwan, and Spain. In the U.S., rat lungworm is found in the Southeast, but mostly in Hawaii.

If you happen to eat raw or undercooked snails or slugs that have the parasite, you can get infected. In some cultures, snails are often on the menu. In other cases, children dare each other to eat a slug and wind up getting infected.

People used to think that you could only get rat lungworm from snails or slugs, but that’s not the case. Recent research shows other creatures can pass it to humans, too. 

Rat lungworm has been found in:

  • Cattle
  • Crabs
  • Flatworms
  • Fish
  • Frogs
  • Lizards
  • Pigs
  • Shrimp
  • Toads

Animals linked to infections in humans include:

  • Centipedes
  • Fish
  • Flatworms
  • Frogs
  • Lizards
  • Shrimp
  • Toads

Make sure that your produce is washed well and does not have any slugs or snails on it. If you live in an area where rat lungworm is found, watch out not to eat any of the animals above and pay attention to produce.

The parasite can live in contaminated drinking water for up to 72 hours. If your produce was rinsed in contaminated water, it could affect the produce, too. But research says there’s little risk for that.

Good news here: You cannot give another person lung rat lungworm if you have it.

 

The parasite gets into your brain, where it feeds and grows. This can cause damage in your brain. Even though the worms die off and never reach the adult stage, that causes inflammation in your body. 

Some people don’t have any symptoms. You may have only mild symptoms that don’t last long. 

But if you get eosinophilic meningitis, those symptoms can be evident. They can start within a few weeks of exposure. They tend to last from 2 to 8 weeks.

The symptoms may include:

  • Headache
  • Stiff neck
  • Fever
  • Nausea
  • Vomiting
  • Pain or tingling on your skin

The doctor will ask about your symptoms. They’ll want to know if you’ve been exposed to things like raw snails or slugs. Knowing if you’ve eaten any animals or produce potentially affected by rat lungworm may be enough to make the diagnosis.

They may do some bloodwork or do other tests to see if you have meningitis. This can include a CT scan or spinal tap, which lets them see if there are worms in your cerebrospinal fluid, which flows around your spinal cord and brain. (During a spinal tap, the doctor would numb your back and put a needle between your bones to draw out this fluid.) 

 

Children may have a higher risk for rat lungworm because they’re naturally curious about snails or slugs. Others may eat them if a peer dares them to do so. 

Symptoms of eosinophilic meningitis in kids can include:

  • High fever
  • Lethargy
  • Gastrointestinal symptoms
  • Crankiness
  • Muscle twitching or convulsions
  • Weakness

Children can have a few days to weeks of no symptoms and then have neurologic symptoms.

If you think your child may have rat lungworm or meningitis, see your doctor. They can decide how to treat it based on the child’s age and health history. 

 

Your doctor may not treat rat lungworm because it eventually dies off. Even if you get eosinophilic meningitis, you may not need medication.

In some cases, symptoms last for weeks or months because it takes your body time to respond to the parasites dying off. 

If your doctor gives you medication, it may be pain medication instead of drugs to treat the infection. You may get medication if you have a severe rat lungworm infection.

Some doctors say people should get an anti-parasitic medication like albendazole to kill the parasites before they can cause more damage to your brain. They may give you a steroid to lower inflammation as well.

In some cases, symptoms may persist indefinitely. Some people look to acupuncture and vitamins, while others focus on managing the pain. There’s no research on long-term recovery from rat lungworm.

Here are a few things you can do to avoid getting a rat lungworm infection:

  • Don’t eat raw or undercooked snails, slugs, frogs, or shrimp.
  • Wear gloves and wash your hands if you’re handling snails or slugs.
  • Wash all of your produce thoroughly.
  • Avoid raw vegetables if you’re traveling to an area where rat lungworm is common (or if you live in one).

Giant African land snails are a damaging species of snail because they feast on plants. They can also carry rat lungworm. They reproduce very quickly, and they don’t have any natural enemies to help control the population. In the U.S., you need a permit to have one.  

In 2023, the snails were sighted in Florida, and a few areas were put under quarantine to prevent the spread of rat lungworm.