Preventing Rat Lungworm
Rat lungworm, a parasitic disease carried by slugs and snails, is making headlines in Hawaii and causing widespread concern. Department of Health (DOH)’s District Health Officer Dr. Lorrin Pang visited Molokai at the end of last month to share facts about the disease and its prevention, along with other local speakers. So far no cases have been reported on Molokai, but Pang said the island does have all the factors necessary to spread rat lungworm.
Rat lungworm is spread by Angiostronylus, a worm that carries the disease. Pang said the parasitic worm thrives living in rats, but can also affect humans.
“The worm goes between the rat and slug or snail and back to rat and goes back and forth,” explained Pang of its lifecycle. “It is happy without a human. Once in a while we eat a slug and it treats the human like a rat.”
However, we can’t contact the disease directly from rat feces; the parasite must first mature in a slug or snail. And unlike rats, humans are a “dead end host,” meaning the parasite dies inside humans and does not continue its lifecycle.
The adult worm lives in the pulmonary arteries of rats, where it lays eggs. The hatched larvae migrate to the rat’s airway, where they are swallowed and passed in their feces. They are then ingested by the snail or slug, where the parasite develops into the third stage of its lifecycle. Rats then eat the slugs, and the worm travels to the rat’s brain to mature before the cycle begins again.
If an infected slug or snail is eaten by a human, Pang said the parasite heads to the brain but unlike the rat’s brain, our brain cells attack and kill the intruder.
“There’s a lot of collateral damage…when you kill the worm,” he said. “You harm your own brain.”
Slugs can carry thousands of stage three worms, and Pang said the more parasites you happen to ingest, the worse the damage can be.
Experts agree the best prevention is to thoroughly wash all produce before eating it. Pang said to hand rinse each vegetable leaf — soaking in water won’t work. Alternatively, you can “cook the heck out of it, or freeze it for 24 hours.” Pang said boiling for at least three to five minutes will kill the parasite.
Pang said though rat lungworm has existed for years around the world, the Hawaii cases increased after the invasive semi-slug came to the islands in the early 2000s. Since it was first found on Hawaii Island in 2004, he said there have been 50 cases, with a recent rise in incidents. On Maui, there have been 10 cases in the last 10 years, and six since January of this year in East Maui, according to Pang.
The semi-slug is small and the babies are clear so are difficult to detect on produce. Pang said 80 percent of the species carry the parasitic worm, and though other species of slugs and snails can also carry the disease, the likelihood is lower. Semi slugs can travel surprising distances and climb papaya and banana plants; they like to rest in dark, smooth and moist locations. Even the slime of the slugs can transmit the disease.
While symptoms generally include extremely painful headaches, Pang said an infected individual won’t notice any symptoms until the parasite has reached the brain — which happens within about 18 hours. Once in the brain, he said there is no treatment and it cannot be removed. About 5 to 10 percent of people will suffer brain damage.
The DOH showed an interview with Maui resident Tricia Mynar, who contracted rat lungworm while on Hawaii Island. She suffered extremely painful nerve damage and now uses a wheelchair; doctors are not yet sure whether the damage will be permanent. Yet even after her harrowing experience, she advises people not to stop eating vegetables.
“It’s not the fear of eating vegetables, it’s learning how to prepare it and take your time to wash it and prepare it,” she said in the taped interview. “I just want people to learn from one another.”
Harmonee Williams is director of nonprofit Sust`aina-ble Molokai’s Food Sovereignty program. She plays a direct tole in getting local produce to island residents through school gardening programs, the federally funded Fresh Fruit ad Vegetable program in schools, and the organization’s new Mobile Market that connects farmers and consumers.
“We take this issue [rat lungworm] seriously and we’re getting trained in food safety protocol,” Williams assured residents. She said they educate students, growers and consumers on the risks and prevention methods.
Alton Arakaki from UH’s College of Tropical Agriculture and Human Resources on Molokai discussed ways to “break the cycle” by controlling rats and slugs.
“You’re going to have to think like a snail to do battle with these guys,” he said, advising setting poison or traps in protected, dark and moist locations that are attractive to slugs but won’t target unintended species.
Attendee Dano Gorsich, who has been farming for decades on Molokai’s east end at Waialua Permafarm, said they haven’t had a snail or slug in their gardens since they enclosed the area and got a flock of ducks.
Though contracting rat lungworm can have frightening effects and preventing it can appear challenging, Pang reminded residents that they have the power to mitigate it.
“You have some control over this disease, you have some responsibility in washing it,” he said.