It’s rare, but snails and slugs can carry a parasite called rat lungworm, which, honestly, is a pretty gross but entirely appropriate name for this organism.
Infections with the parasite are rare in the continental US, but a new report from the Centers for Disease Control and Prevention (CDC) that looked at 12 people who got it between 2011 and 2017 suggests they can happen.
Eating raw veggies contaminated with a slug or snail — particularly in the South — was one way some of the people were infected, according to the CDC’s latest Morbidity and Mortality Weekly Report.
Rat lungworm is largely found in Asia and the Pacific Islands, including Hawaii, but sometimes in Africa, the Caribbean, and the US. They call the parasite a rat lungworm because it’s a worm that can infect the lungs of rats, so it’s 100% accurate nomenclature here.
Some people who come into contact with this parasite don’t have many symptoms and get better without treatment. Others progress to a very serious illness called angiostrongyliasis, after the name of the parasite, which is Angiostrongylus cantonensis.
It can include a rare inflammation of the lining of the brain that can cause a stiff neck, tingling, a low fever, and vomiting, which is called eosinophilic meningitis.
The CDC researchers tested 69 cerebrospinal fluid samples sent to the agency between 2011 and 2017, and found 12 that had DNA from Angiostrongylus cantonensis, a diagnosis of probably angiostrongyliasis, and enough information to confirm the diagnosis.
Overall, the number of cases they found was “reassuringly small,” the report’s co-author, Sue Montgomery, told BuzzFeed News, although it’s possible there have been more cases that have not been reported to the CDC.
Six of the 12 people had traveled outside of the US, and may have picked up the infection in Asia, the Caribbean, or the Pacific Islands. The other six — four from Texas and one each from Alabama and Tennessee — didn’t travel, so they probably picked it up in the US.
More than half of the patients, or 55%, reported eating raw vegetables.
Before this, there were only three cases of angiostrongyliasis reported in the medical literature that were from the continental US, said Montgomery, who is lead of the epidemiology team at the Parasitic Diseases Branch at the CDC’s Center for Global Health.
Those cases included one boy who ate a raw snail on a dare. He recovered about two weeks later without specific treatment for the infection, according to the CDC.
Patients can experience symptoms like fever, weakness, severe headache, and numbness and tingling, as well as a stiff neck, weakness in their lower body, difficulty speaking, light sensitivity, temporary face paralysis, and irritability. There is no specific treatment for the condition, although many patients in the CDC’s report were treated with steroids.
Rat lungworm disease has existed in Hawaii for decades, and 18 cases were seen in the state in 2017, according to the Hawaii State Department of Health.
However, It’s not clear if slime left behind on produce can transmit the infection.
You can also get rat lungworm from eating raw or undercooked frogs, land crabs, or freshwater shrimp that have eaten the contaminated snails, so you want to cook those thoroughly.
There are a couple of important take-home messages from the report, Montgomery said.
“We want people to thoroughly wash their fresh produce before eating it,” she said.
Although it’s possible for produce from the grocery store or garden to contain a snail or slug, it’s probably more likely from a backyard garden.
Either way, “it’s a good practice to thoroughly wash all fresh produce before you eat it,” Montgomery said.
It’s also not a bad idea to “keep rats, snails, and slugs away from your garden,” she added.
The federal agency also wants healthcare providers to check patients who have this type of meningitis for signs of the parasite.
“Doctors should think about this infection if they have a patient with eosinophilic meningitis,” Montgomery said.
The cases may be more common in the southern US because they have the right conditions for the normal life cycle of the rat lungworm.
Like the name suggests, the parasite infects the lungs of rats, which cough and introduce the worms into their own digestive tract. When the rats poop, the worms are shed in the feces, which may then be eaten by snails and slugs. The parasite is then passed back to rats when they eat the snails and slugs.
For more details about the the parasite, check out this nice, clear, and kind of gross video that explains the life cycle of the rat lungworm from the CDC.
And don’t eat snails and slugs, even on a dare.