Hawaii public health authorities are urging both islanders and tourists to take precautions against rat lungworm, a parasitic worm that has infected five people in the state this year.
Officials with Hawaii’s Department of Health announced last week that lab tests have confirmed two visitors contracted rat lungworm disease while traveling in western Hawaii earlier this year. Over the past several months, three residents have also been sickened by the parasite, and 10 cases were confirmed statewide in 2018, officials said.
“It’s important that we ensure our visitors know the precautions to take to prevent rat lungworm disease, which can have severe long-term effects,” Bruce Anderson, director of Hawaii’s Department of Health, said in a statement Thursday. “Getting information to visitors about the disease is just as critical as raising awareness amongst our residents.”
None of the five confirmed cases this year in Hawaii could be traced to a precise source of infection. However, health officials said one resident may have become infected by eating produce from a home garden that may have had a slug or snail infestation; one visitor ate homemade salads on vacation; and another visitor is believed to have been infected while “grazing” on unwashed produce from the island.
Those who have been infected this year are adults, but the cases last year included three toddlers and one adolescent, officials said.
A rat lungworm is a parasitic worm (Angiostrongylus cantonensis) that lives in rodents’ lungs and can be passed onto snails and slugs — and then to humans, according to the Centers for Disease Control and Prevention.
As the CDC explained in a video, the rodent — typically a rat — coughs up the worms and then swallows them, forcing them into its stomach. Eventually, the rat excretes the worms. Snails or slugs can become infected by eating the rat’s feces, according to the CDC, and people can become infected by eating those snails or slugs.
However, the CDC stated, an infected person cannot pass it on to others.
People can get infected by eating raw or undercooked snails or slugs that are infected with this parasite. In some cultures, snails are commonly eaten. Some children, in particular, have gotten infected by swallowing snails/slugs ‘on a dare.’ People also can get infected by accident, by eating raw produce (such as lettuce) that contains a small snail or slug or part of one.
Certain animals such freshwater shrimp, crabs, or frogs, have been found to be infected with larvae of the parasite. It is possible that eating undercooked or raw animals that are infected could result in people becoming infected, though the evidence for this is not as clear as for eating infected snails and slugs. Of note, fish do not spread this parasite.
So how can people avoid it?
Don’t eat raw or undercooked snails or slugs, frogs or shrimp/prawns. If you handle snails or slugs, wear gloves and wash your hands. Always remember to thoroughly wash fresh produce. When travelling in areas where the parasite is common, avoid eating uncooked vegetables.
Some people who have contracted rat lungworm disease do not experience symptoms or symptoms are mild and often subside without medical intervention, according to the CDC. But in rare instances, the CDC said, the disease can lead to eosinophilic meningitis, an extremely rare infection that can cause muscle weakness, paralysis, coma and death.
In late 2018, a young Australian rugby player who had swallowed a slug on a dare — and contracted rat lungworm disease — died, eight years after the parasite invaded his brain, leaving him paralyzed and unable to care for himself, according to local reports.
Heather Stockdale Walden, an assistant professor of parasitology at the University of Florida’s College of Veterinary Medicine, said rat lungworm disease has been seen in Hawaii for decades.
“It has had a long time to spread throughout the islands and make its way into native snail populations and Hawaii has several potential intermediate hosts for this parasite,” she wrote in an email to The Washington Post. “This puts it in closer proximity to humans and accidental consumption.”
Walden added that in the continental United States, “we have known about the presence of the rat lungworm since the 1980s when it was found in Louisiana. Since then, it has been reported in a handful of states, and we found it throughout Florida — from Miami to the Panhandle.”
Though, according to the CDC, there have been “very few” confirmed cases reported in the continental United States.
“It’s an extraordinary parasite that we need to pay attention to, but not something that should cause fear,” Walden wrote. “Educating those living in endemic areas, areas where this parasite has been reported, or those traveling to endemic areas is important in order to limit accidental infections through ingestion of the infected mollusks."
The parasitologist added, “Keeping an eye on children and talking to them about the mollusks and also making sure pets are not ingesting the mollusks is important.”