Features — Need to Know: Rat Lungworm Disease

ratBy Barbara Fahs

When you hear the name “rat lungworm disease,” you might find it revolting. But the symptoms it creates, and the long-lasting physical effects, are even worse.

First reported in Hawai‘i in the 1960s, rat lungworm and the disease it causes (Eosinophilic meningitis or angiostrongyliasis) have not been widely reported.

Throughout Hawai‘i, only 42 cases have been reported since 2007, with 38 of them occurring on the Big Island. However, the Department of Health acknowledges that case numbers are probably higher, since diagnosis is difficult. According to Dr. Sue Jarvi of the Daniel K. Inouye College of Pharmacy at UH Hilo, the disease “was originally discovered in Canton, China in the 1930’s… Since then it has spread to at least 30 countries, likely by rats on shipping vessels.” 

What causes this disease?

Rat lungworm is caused by a nematode, or roundworm, and the critters that transmit it to humans and other animals (including dogs and horses) are slugs and other mollusks — the semi-slug, giant African snail and the Cuban slug. So can flatworms, fresh water prawns and possibly fresh water opihi. The slugs, snails and rats are species that have been introduced to Hawai‘i, and when you put them together, it equals serious danger to humans. When slugs and snails eat the feces of an infected rat, they acquire the nematode parasite, which can easily be transmitted to unsuspecting humans who feast on unwashed lettuce and other produce that contains pieces of the creatures, or possibly the creature’s slime trail.

Kay Howe, a graduate student at UHH, reported recent findings on March 23: “We have molecular confirmation that at least some of the larvae that were shed from drowned slugs in rainwater were indeed rat lungworms and were capable of surviving at least 56 days out of the slug and in water.” This adds an additional caution to residents who rely on water catchment.

What are the effects

and symptoms?

Early symptoms include severe headache, skin sensitivity, vision problems and photosensitivity as well as inability to urinate. “Symptoms generally are flu-like,” said Howe, who works with Dr. Jarvi and is also the mother of a victim. If you or a loved one exhibits similar symptoms, seek immediate medical attention. Hilo Medical Center officials are now admitting patients when they first start showing symptoms, according to Dr. Jon Martell.


Remove lettuce, spinach, kale, bok choy, celery, cabbage and other greens from the head so each leaf floats freely in a sink filled with water. Howe reports, “Studies show there are few additives that will kill the larvae. Neither vinegar, hydrogen peroxide, or grapefruit seed extract are effective. Careful washing in POTABLE water is the best way to clean any produce that is to be eaten raw.” Strip away the outer leaves of veggies like this and examine closely inside. If you find a slug, do not eat that vegetable. Rinse quickly and then drain: as Howe reported, suspect larvae can live for up to two months in water.

It’s equally important to thoroughly wash fruit: if a slug or snail that carries the disease-causing nematode has traveled over the surface, when you cut the fruit your knife can push the slime trail inside: it has been proven that at least a small amount of the pathogen exists in the slime.

Howe mentioned that a simple 20-micron filter with a 5-micron filter inside will prevent larvae from entering your home through your water pipes. This filter fits in standard water filter housings and costs about $11, according to Hawai‘i Catchment Company, which sells them at their Kea‘au location.

Keeping Slugs and Snails Away

If you’re growing any of your own fruits and vegetables and you prefer not to use chemical pesticides such as snail bait, there is a natural product called Sluggo, which contains iron phosphate. Scatter it around the border of lettuce beds and around the base of fruit trees.

Howe adds, “You can also trap slugs by placing pieces of plastic, cardboard, or wood in shady, moist areas and then turning them over and collecting the slugs. Use tongs or chopsticks to pick them up (no bare hands) and put into a slug jug (1/2 gal water + 1-1/8 cup salt). Close the lid and shake. The high saline solution will kill the mollusk and the parasite.”

Recent cases

Phoenix Roewe, 23, contracted the disease in March of this year. According to Hawai‘i News Now on April 14, “He believes he may have been infected by siphoning water out of his catchment tank with a hose.” He described his symptoms in the same article: “It got pretty bad. I’d be up all night with unbearable pain until four in the morning… all night I’m throbbing. I feel like I got pretty lucky though — it could have been worse.”

“It’s been a rough road.  He’s hanging in there. He can walk and talk.  It’s been hell and back for him, Roewe’s mother Smiley Burrows told Big Island Chronicle.

“The good news is we are learning how scuzzy water tanks are, we’re learning how to clean them, and we are really seriously educating people on how  important maintaining the water is.

Burrows noted the high percentage of people in Puna who rely on water catchment tanks and the need for researchers to conduct a water filter micron test.

“Bleach doesn’t kill parasite.  Vinegar doesn’t kill it.  It lives in stomach acid.” Only a certain size of filter will stop from entering, Burrows said

While Roewe has been spared and his family is helping to warn people about the disease, Stefan Bell, 66, was not so lucky. After showing symptoms of rat lungworm in March of this year, his heart gave out during a hospital test and he passed away on March 14. His family continues to question whether the disease caused his death or whether the medical testing contributed to it.


Hawai‘i Catchment Co. (16-643 Kipimana St., Bay 19, Shipman Business Park, Kea‘au. 982-8888) is cooperating by lending the researchers the equipment to do a proper filter study. spreads-fear-across-hawaii-island

More on Rat Lungworm Disease: www.malamaopuna.org/ratlung/ratlung.php

Centers for Disease Control: http://dpd.cdc.gov/dpdx/html/Angiostrongyliasis.htm http://pharmacy.uhh.hawaii.edu/rlw/

Barbara Fahs is the owner and creator of Hi‘iaka’s Healing Herb Garden, LLC in Kea‘au and author of the book Super Simple Guide to Creating Hawaiian Gardens. She teaches workshops on herbs and how to make healthful products from them. “Friend” her at the “Healthful Herbalist” page on Facebook for info.


2 replies
  1. Kit
    Kit says:

    The point about the 5 micron filter is well taken. However, where can we test our catchment water? What are the newer methods of cleaning mentioned by Smiley?

  2. eve
    eve says:

    what about the UV filters for catchment water? i know still have to watch it if power goes out… but has this been shown to kill the parasite?

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