Cases of eosinophilic meningitis caused by the rat lungworm parasite have risen sharply in Hawaii over the past 5 years. The parasite, a nematode (Angiostrongylus cantenosis), was carried from SE Asia to Hawaii by rats, which are the host. There is a possibility that there may be two species of the parasite in Hawaii. Angiostrongylus cantonensis has been identified in Hawaii, which causes human eosinophylic meningitis. Angiostongylus costaricensis has not yet been identified here but causes human abdominal angiostrongylisasis, affecting the digestive track and bowels. Many victims in Hawaii have had symptoms that suggest infection by Angiostongylus costaricensis.

The parasite can be transferred to slugs, and snails in the 3rd larval stage; it has also been found in flatworms. Humans pick up the parasite by ingesting slugs/slug slime contaminated fruits /vegetables/water or raw or undercooked slugs, snails, mollusks, prawns and monitor lizards. Humans are a dead end host, the parasite will not develop to sexual maturity and may live for up to a year in the human body but will eventually die. While the parasite has been in Hawaii a long time, cases of illness have risen with the introduction and increase in the population of an invasive semi-slug (Parmarion martensi), which is native to SE Asia.

Studies done in Hawaii in 2005 have shown 75.5% of semi-slugs collected on the Big Island to be infected with the parasite.

To best protect yourself from getting the parasite be informed & proactive.

There has been little research done in the U.S., most comes from South America and SE Asia.

Extreme caution is your best protection.

Most people we have asked do not know how they got it. It is mostly through ingestion of a slug or slug contaminated vegetables/fruits, however, one person who had a severe case of rat lung this winter believes she contracted it by stepping on a slug and another believes she got it from handling them. As no research yet disproves this, take extreme caution and wear shoes and gloves. Collecting slugs is a good way to keep numbers down, but use a tongs to pick them up and deposit them in a jar of 10% vinegar, bleach etc. They usually come out a few hours after dark and are numerous in the cooler wetter months. The semi slug seems to be less active in the summer hotter season but in early fall the tiny babies can be found and they too can carry the parasite. The semi slugs love the food that we and our pets eat. They can crawl up the sides of houses and get into homes. They can crawl into water systems where the slug will drown and release the parasites which can survive for up to 72 hours in water. Slugs will get into compost bins and trash cans, crawl under tarps, weed cloth, plastic, and plastic plant pots. They appear soon after food sources (including pet foods) become available.

Slugs may leave parasites in their slime trails including on countertops, cooking /eating implements and even toothbrushes. A very small piece of a slug can contain as many as a thousand parasites. Developing slugs (neonates) carry the parasite as well; they are very small, approx. 2mm in length, and can be difficult to see.

Animals can also get rat lungworm. A sloth at the Hilo Zoo got rat lungworm and became paralyzed in the hind legs. There have been reports of people’s cats and horses contacting it.

To avoid ingestion of a slug or slug slime look closely (put on your glasses if you wear them) and thoroughly wash all vegetables and fruit under running water.

Take more time with curly leafy vegetables, wash leaves individually. People advise soaking veggies in grapefruit seed extract, hydrogen peroxide, salt water, etc., but there has been no research done to show that any of these will kill the parasite. Avoid bringing slugs into your home with locally grown produce. Check pineapple tops or twist tops off just above the leaf base and leave outside.

Flatworms prey on the semi-slug and it is suspected that they may carry even higher loads of parasites. They easily hide in leaves or tight heads of produce and their soft bodies fall apart into small pieces when handled or under water pressure. Cooking food will kill the parasite however the exact time/temperature has not been scientifically determined. Err on the side of caution.

People in SE Asia do not eat raw vegetables or salads; cases there result from eating raw or undercooked snails.

Do not eat salads or other raw food dishes if you are at a potluck or out for dinner at friends or a restaurant unless you know for a fact that the person /people preparing the dish know about rat lungworm and are careful about food preparation. Slugs can crawl onto food left uncovered at potlucks and picnics. KEEP FOOD COVERED!

How do you know if you have rat lungworm and what do you do?

We all need to know this, even guests visiting the island. What if you have been vacationing in Hawaii and get sick when you go home? Doctors on the mainland know even less about this than doctors in Hawaii. The number of cases of rat lungworm this past year has changed the medical protocol at Hilo Medical Center for early diagnosis and treatment. It is important that we all know symptoms of rat lungworm as early treatment is much more effective in preventing serious neurological damage. Diagnosis is usually done with a lumbar puncture and collection of cerebral spinal fluid, which is examined to determine if eosinophils (a specific type of immune cell) are present. There is also a blood test that has been developed which shows antigens the body develops to combat the parasite, however the antigens will not be present in the blood until 3 or more weeks after infection.

Symptoms are flu-like and usually start with a headache, most often severe, and stiffness in the neck. There may be fever, joint pain, fatigue and nausea. The skin may feel itchy, like something crawling under it, and then become extremely sensitive to touch.

There are reports of people who years after having had rat lung cannot wear shirts or long pants because their skin is still so sensitive. There are victims who take daily doses of morphine to help them endure the nerve pain they still experience 2 and 3 years later. The inability to urinate, called Elsberg Syndrome, has been reported in other cases of rat lungworm. Rat lung victims may also experience hallucinations, disorientation, vision problems and visual impairment. Complete paralysis may set in. Short-term memory loss seems to be common in serious cases.

Hawai’i and US mainland medical centers have very little or no experience with rat lungworm, and scientific and medical research is sorely lacking. Medical treatment in Hawaii is currently based on that used in China, Thailand and Taiwan for rat lungworm victims. If a person is hospitalized, steroids and possibly anti-parasite medication will be administered. The steroids dampen the body’s immune system response, which goes into overdrive attacking the parasite. Inflammation in the brain (meningitis) becomes the major concern, spinal taps may be used to reduce pressure in the brain/spinal column and the patient will be put on pain medication. Whether to give the patient anti-parasitic medications will be carefully weighed, as they can cause a die off of parasites and create even more inflammation.

If a person is hospitalized, steroids, pain medication and possibly anti-parasite medication may be administered. The steroids decrease inflammation caused by the body’s overactive immune system response, to the parasite. Inflammation in the brain (meningitis) becomes the major concern. Spinal taps may be used to reduce pressure in the brain/spinal column. Whether to give the patient anti-parasitic medications will be carefully weighed, as some medications can cause a die off of parasites which can create a greater inflammation reaction. Doctors and medical centers on the Big Island are beginning to recognize the problem due to the number of recent cases. Early diagnosis and treatment are essential.

As the rainy season begins, slugs will begin to emerge and the potential for infection will become greater. Personal diligence is key to prevention until science can provide us with more knowledgeable information.

Rat lungworm affects everyone living in Hawaii, whether you buy your vegetables in Costco or at the local market. The problem is not with home gardens or locally grown food, it lies with invasive species finding their way to Hawai’i, such as rats, the primary carrier, snails and slugs that carry high loads of the parasite and whose populations are increasing and spreading on the islands. It would be wise for scientists to determine if mongooses also carry the parasite, as they are quite similar to rats.