Two people got rat lungworm from eating raw centipedes. Could you be next? | Popular Science
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Two people got rat lungworm from eating raw centipedes. Could you be next?

The answer is yes—even if you don't like eating bugs.

lungworm angiostrongylus cantonensis

A beautiful lungworm.

Rat lungworm is, thankfully, one of the few parasites that sounds more disgusting than it is. Unfortunately, it’s even more terrifying than its gross name would suggest.

Two poor humans who recently got infected—as reported Monday in the journal American Journal of Tropical Medicine and Hygiene—contracted the parasite by eating raw centipedes, which might give you a false sense of security. ‘I don’t eat centipedes,’ you think, foolishly. Nor do you likely live in a small rural town in Guangzhou, China, where the mother and son pair reported to the hospital with persistent headaches. (Of course, you may live in a small rural town in Guangzhou and/or enjoy the occasional centipede snack, but our reader analytics tell us this is statistically unlikely).

But rat lungworm isn’t confined to Asia and the Caribbean anymore: It’s in the U.S., too. And you don’t have to indulge in conscious entomophagy for the disease to strike you.

First, though, let’s talk about what the heck rat lungworm is. As the name implies, the parasitic roundworm that causes angiostrongyliasis (the scientific name for the disease) lives inside rat lungs, specifically inside the pulmonary blood vessels. Infected rats excrete the worms in their feces, where it can go on to infect other critters like snails, slugs, frogs and, yes, centipedes. Cooking any of these animals kills the parasite, so escargot fans needn’t worry, but eating any of them raw may very well pass the roundworms on to you. You, a human, are what epidemiologists call an incidental host. Angiostrongylus cantonensis isn’t trying to infect you, but if it finds itself in your bloodstream it’ll make itself at home.

Once inside you, the worms can get into your central nervous system, where they can cause eosinophilic meningitis. Meningitis is, generally, inflammation of the meninges, which is the membrane surrounding your brain and spinal cord. The eosinophilic type is rare and is so-called because it involves a proliferation of eosinophils, a type of white blood cell that fights parasites. That is, in fact, how many cases of rat lungworm are diagnosed in humans. There’s no blood test, so diagnosis relies on doctors picking up on certain clues enough to think to test the cerebrospinal fluid for high levels of eosinophils.

That was the case for this mother and son, who reported to the hospital a few weeks apart complaining of persistent headaches. The mother, 78, also had cognitive impairment and sleepiness. The son, 46, had some neck rigidity. It was only after questioning that the doctors discovered both had eaten raw centipedes in the previous days, and thought to look at their cerebrospinal fluid.

Those symptoms aren’t exactly typical of rat lungworm, though. The neck stiffness and headaches are classic signs of meningitis in general—the inflammation in the meninges causes both. But most people with meningitis also have much more serious symptoms. Many report nausea, vomiting, fever, abnormal sensations in the arms and legs, and changes to vision. As the disease progresses, some people can develop other neurological problems and can even die. That being said, rat lungworm isn’t always horrifying. It doesn’t even always cause meningitis. Some people don’t have any symptoms, others get minor headaches or a stiff neck, but their bodies mostly fight off the parasite without them ever noticing.

The other parasite that causes rat lungworm, Angiostrongylus costaricensis, can also cause abdominal pain since it often travels to the intestines. The Centers for Disease Control notes that the pain can be severe enough to mimic appendicitis, and it’s often only once surgeons remove the appendix that they realize what’s actually causing the pain. If the worms stick around, though, people can develop internal hemorrhaging from their intestines as the worms get stuck in capillaries and cause inflammatory reactions as they die. (Okay, maybe this is grosser than it sounds after all…).

This used to be problem mostly in Asia and the Caribbean. That’s where the parasite circulated between the rat and snail/slug populations. A 2013 study found that the disease is spreading, though, largely as a result of global shipping patterns in cargo ships and planes, which can carry rats and snails or slugs without anyone realizing. That same study found infected apple snails in New Orleans and infected flatworms in Hawai’i, as well as other infected mollusks and many, many rats. A 2015 study found the parasite in the Giant African Land Snails that hang out in Florida, too. Some researchers have expressed concern that climate change could expand the reach of these critters, thus also broadening the area that the parasite can come in contact with humans.

Now, you may be thinking at this point that you still don’t eat uncooked snails and slugs. To that we will say that you don’t eat uncooked snails and slugs intentionally. Some people certainly do eat these creatures raw, whether for supposed medicinal purposes (which was why the two people in the case report consumed the centipedes raw) or on a dare, or simply because they enjoy it (no judgement). But many of us have probably eaten some raw slug unintentionally on a bit of poorly-washed lettuce. And you don’t have to eat the slug or snail itself—larvae can hide inside the slime. You can get infected without even realizing it. Besides, it’s not just slugs and snails. Shrimp, frogs, and crabs can give you the disease, too, and so can water that’s harbored any of those animals.

People living in Hawai’i have already gotten infected (and so did one teen who was just on vacation there). Several people have ended up in comas, and a study of the 84 cases of rat lungworm in Hawai’i from January 2001 to February 2005, researchers found that at least 24 of the cases were attributable to A. cantonensis.

These cases don’t seem to have been treated for the parasite specifically, but rather were given medicine to improve their symptoms. Similarly, the CDC doesn’t list a specific treatment for rat lungworm. Both of the Chinese patients in this recent case study were treated with albendazole (an anti-parasitic) for 21 days and dexamethasone (an anti-inflammatory steroid) for 15 days, which seems to have resolved the disease.

If you live around the Gulf of Mexico or in Hawai’i, rat lungworm could be a growing problem for you. So yes, avoid eating raw or undercooked slugs or snails (not that most of us would know the proper cooking technique for a garden slug), but also don’t drink from the garden hose or handle any of these critters that you find near your house without washing your hands afterwards. Thoroughly wash all your produce, too. And maybe just stay away from raw centipedes generally.

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