Rat Lungworm

Rat lungworm is a parasitic worm you can get from eating slugs, snails or unwashed raw vegetables. Most people get mild or no symptoms, but the parasite can infect your brain and cause headaches, neck stiffness, vomiting and neurological (brain and nerve) issues. Meningitis can be serious. Go to the ER if you have symptoms of meningitis.


What is rat lungworm (angiostrongyliasis)?

Rat lungworm is a parasitic worm (Angiostrongylus cantonensis) that can cause an infection in your brain. You can get it from eating uncooked slugs, snails or vegetables. It usually lives in the pulmonary artery of rats, which is why we call it “rat lungworm.”

Most people who get an infection don’t have symptoms, but sometimes the worm can travel to your brain and cause eosinophilic meningitis. Meningitis is an infection in the lining of your brain that causes inflammation. The parasite can also infect deeper parts of your brain.

Rat lungworm infections are also called angiostrongyliasis.

Some causes of meningitis are very serious. Go to the ER or seek immediate medical attention if you have symptoms of meningitis.


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Is rat lungworm found in the US?

Yes, rat lungworm cases have been reported in the U.S., mostly in Hawaii. There’ve been very few cases in other U.S. states. It’s most commonly found in Southeast Asia and the Pacific Islands.

Symptoms and Causes

What are the symptoms of rat lungworm?

Symptoms of eosinophilic meningitis caused by rat lungworm include:

  • Severe headache.
  • Neck pain or stiffness. It may be so severe that you can’t move your chin down toward your chest.
  • Nausea and vomiting.
  • Tingling or pins-and-needles feeling (paresthesia).
  • Vision changes.
  • Confusion.
  • Sensitivity to light (photophobia).

What causes a rat lungworm infection?

Rat lungworm is a parasitic roundworm (nematode). It reproduces in rats’ lungs, rats poop out the young worms (larvae), and snails and slugs (types of gastropods) eat the larvae. Rats eat the infected gastropods and become infected with adult worms, starting the cycle again.

How do people get rat lungworm?

Sometimes, humans eat a gastropod that’s infected with rat lungworm larvae or its slime (for instance, on vegetables a slug has crawled on). The larvae can develop into mature worms and travel to your brain, causing symptoms. It’s also possible you could get the parasite from eating infected freshwater shrimp, crabs or frogs. But this isn’t a common or well-documented way to get infected.

Is rat lungworm contagious?

No, rat lungworm isn’t contagious (you can’t get it from someone who’s infected).

What animals have rat lungworm?

Rats are the most common carrier of rat lungworm. Slugs, snails and other gastropods can carry the larvae. Frogs, shrimp, crabs, lizards and birds also sometimes get infected with larvae.

What are the complications of rat lungworm?

Most people with rat lungworm make a full recovery. Rarely, people who have eosinophilic meningitis can have complications and long-term health effects, including:


Diagnosis and Tests

How is rat lungworm diagnosed?

Providers usually diagnose a rat lungworm infection based on your symptoms and whether you could’ve eaten something contaminated with parasites. They might look for the worms, larvae or eosinophils (blood cells that increase during a parasitic infection) in your body fluids. They’d look for these using a lumbar puncture (spinal tap) or blood tests.

Management and Treatment

How is rat lungworm treated?

There’s no specific treatment for a rat lungworm infection. It usually goes away on its own. Treatments a provider might suggest at home or give you in the hospital include:


Can you prevent rat lungworm?

The best ways to prevent or reduce your risk of rat lungworm include:

  • Thoroughly cooking snails, crabs and shrimp before eating.
  • Thoroughly washing or cooking vegetables and checking them for slugs and snails before eating.
  • Avoiding eating raw vegetables in areas where rat lungworm is common.

Outlook / Prognosis

What can I expect if I have a rat lungworm infection?

Most people with a rat lungworm infection, even those with meningitis, make a full recovery. You may have symptoms on and off for weeks or months as the parasites cause inflammation and die. If your symptoms are severe, you may need treatment in a hospital.

When should I see my healthcare provider?

See a healthcare provider if you have symptoms of rat lungworm and could’ve eaten something that was contaminated. They can monitor you for severe illness and help you manage your symptoms.

When should I go to the ER?

Go to the emergency room or call 911 (or your local emergency services number) if you have symptoms of meningitis, including:

  • Severe headache or neck stiffness.
  • Seizures.
  • Confusion or other mental changes.
  • Sudden vision changes.

What questions should I ask my doctor?

It might be helpful to ask your healthcare provider:

  • How can I manage my symptoms?
  • What new or worsening symptoms should I look out for?
  • How long will it take to feel better?

A note from Cleveland Clinic

Just the name “rat lungworm” would give anyone the heebie-jeebies. Though it sounds scary, most people make a full recovery. But that doesn’t mean you should take it lightly — any kind of brain infection can be serious, especially if you don’t know the cause. If you have symptoms of meningitis, go to the ER or seek immediate medical treatment.

Medically Reviewed

Last reviewed by a Cleveland Clinic medical professional on 06/20/2023.

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