Bummer: A Brain-Infesting Worm in Rats Can Also Attack Humans

You’ll never look at lettuce the same way again.

A new report in Emerging Infectious Diseases, a journal published by the Centers for Disease Control and Prevention, indicates that a parasite with the charming name of rat lungworm has become established in the Atlanta, Georgia area. And while a parasitic problem in rats may not sound like it could affect you, there’s actually a route of transmission that makes having a rat worm in a human brain very possible.

Angiostrongylus cantonensis is a worm that lives the arteries near a rat’s lungs. According to Ars Technica author Beth Mole, the worm experiences an utterly disgusting journey. It lays eggs in the lung tissue, and then the larvae burst out of their pulmonary nursery, only to be coughed up by the rats, swallowed, and evacuated as part of the rat’s waste.

As most people don’t willingly eat rat poop, this sounds like it’s only of minimal concern. Unfortunately, the durable rat lungworm doesn’t stop there. Slugs and snails like to munch on rat feces, which introduce the larvae into their bodies. Rats then eat the snails, re-infecting themselves and allowing the maturing larvae to enter their central nervous system.

Humans get introduced into this vile life cycle when they consume slugs or snails. Sometimes that’s intentional, as in the case of escargot, and other times it’s not. You may consume undercooked seafood (shrimp, crab) that ate an infected snail, or you may find one in leafy greens that haven’t been washed properly. A slug might even contaminate a garden hose, which a person then drinks from.

If rat lungworm enters the human body, it will also attempt to set up housing in the lungs and brain, where the resulting eosinophilic meningitis infection can cause everything from headache to seizures and sometimes prove fatal, though the CDC notes that “most” people make a full recovery. The worms can’t reproduce in humans, so they’ll die—eventually.

This isn’t the first sign of the parasite in the country. In 2018, NBC reported roughly 12 cases confirmed in recent years. Hawaii has recorded five cases of rat lungworm infection in 2022 and 2023.

Should anyone be truly worried? The research conducted by University of Georgia College of Veterinary Medicine asserts the parasite has become comfortable in the southeastern U.S., though the sample size of rats checked was small. Of 33 collected rats, seven had it. More concerning is that the samples were taken over a period of years, from 2019 to 2022. That demonstrates the rat lungworm is persistent.

Still, it does take a unique series of events for A. cantonensis to invade the human body. Providing people avoid eating slugs and are diligent about washing produce, there should be little cause for concern. But definitely stop drinking from the hose.