Big Island Invasive Species Committee (BIISC)

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Rat Lungworm

Rat Lungworm Disease

If you believe you may have ingested a snail or slug, or have symptoms characteristic of rat lungworm disease, please seek medical attention immediately.

Below are the published guidelines in Hawai‛i for medical treatment. Please print & share with your provider:

Caused by the parasite Angiostrongylus cantonensis, rat lungworm disease (RLWD) is a serious health concern in Hawai‛i. The parasite is a nematode (worm) with a two-host life cycle, meaning that to move completely from egg to reproducing adult, it must spend part of its life in two different animals. This cycle starts in the lungs of a rat, where eggs hatch into larvae that are passed in feces. Gastropods (slugs and snails) will then consume the rat feces, and the larvae will continue their development in the slug or snail until they are eaten by a rat, where they can reproduce and begin the next generation.

The danger for humans comes when we interrupt the second transition, by accidentally eating a slug or snail which has been infected with A. cantonensis larvae (rats do not shed larvae at a stage that is infectious to humans, but as other human diseases are spread in rats feces, contact and ingestion should be avoided). Disease symptoms range from mild illness to severe debilitation, coma, and even death. Many survivors of RLWD report permanent injury from the disease.

All snails and slugs – even endangered native snails – can carry the parasite, although one slug, in particular, has been associated with increased incidence and severity of disease. The Parmarion martensi, or “semi-slug,” has been show to have the ability to carry a very high parasite load, which may be associated with the level of severity of RLW disease. As of early 2019, the semi-slug has been confirmed as established from Volcano to Kalapana, through Hilo, and up the coast into North Kohala, and is quickly continuing to spread across the Big Island.

Jan 2020 Update: After the 6th International RLW Workshop, new information was made available that could help residents and visitors who accidentally consume a snail or slug. Based on guidelines from Australia and on preliminary research by collaborators including the Jarvi Lab, the commonly available OTC pinworm medicine containing the active ingredient pyrantel pamoate has been suggested as potentially helping to mitigate the development of serious disease. Remember to freeze any snail or slug pieces for testing to determine presence of the RLW parasite!  Click here to read the full advisory.

How to reduce your risk

Rats have long been recognized as a very damaging invasive species, in Hawaii and around the world.  The semi-slug, along with other introduced gastropods like African snails, Cuban slugs, rosy wolf snails and more, are considered agricultural pests and are the bane of Hawaii agriculturalists.  Control of these pests has long been a struggle, but all residents of the Big Island are encouraged to control them as much as possible. 

An Integrated Pest Management (IPM) approach which includes poisonous baits, trapping, reduction of habitat, and repellants that is appropriate for the location should be developed.

Be careful of all leafy greens. The only safe way to eat raw leafy greens is to thoroughly inspect and wash each leaf individually, and allow the leaves to dry before eating (parasites cannot survive drying out). Freezing for 24 hours or cooking are the safest approaches for consuming leafy greens. Other vegetables and fruits should be carefully inspected and washed thoroughly before consuming.

Resources

We, at BIISC, are not disease specialists, and we rely on research by the Jarvi Lab at the University of Hawai‛i-Hilo Daniel K. Inouye College of Pharmacy, as well as information received from the Hawai‛i State Department of Health and the CDC. We have collected resources for RLW and compiled them here in an effort to help people who are seeking assistance with these invasive pests and trying to protect themselves from RLW disease. If you have any additional resources that you believe would be helpful to add, please email us at biisc@hawaii.edu.

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