Question: Is there a way I can find out if the rats I keep finding in my outdoor shed and the slugs that live in my yard carry the rat lungworm disease? I live in Manoa and have two dogs and am worried that they could acquire the disease. Also, my yard is a favorite spot for neighborhood dogs that love to sniff around on their daily walks.
Answer: You should consider all rats and slugs in your yard potentially infectious and reduce their populations, according to experts at the state Department of Health, the University of Hawaii at Manoa and the University of Hawaii at Hilo.
Rat lungworm disease is caused by a roundworm parasite that rats carry and shed in their feces. Snails, slugs, freshwater shrimp, land crabs and frogs might ingest the feces and become carriers, known as intermediate hosts. Humans (and dogs) can become infected by ingesting raw or undercooked intermediate hosts. The parasite affects the brain and spinal cord.
“Testing rats and snails/slugs in individual yards should absolutely not be thought of as a means to assess whether your yard is free of infected rats and snails/slugs. … A better approach is to implement efforts to reduce the rat and snail/slug populations in your yard,” said Robert H. Cowie, a research professor at UH-Manoa who is an expert on mollusks.
Sue Jarvi, a professor at the UH-Hilo pharmacy college and an authority on the disease, said her lab offers a molecular test that detects the parasite’s DNA in slugs. The test costs $25 per sample. However, it is mainly sought by people who have ingested part of a slug or found one on leafy greens they ate or were preparing to eat. Email Jarvi at jarvi@hawaii.edu for more information about this option.
Like Cowie, she emphasized that “testing one slug has no bearing on whether another one from the same area will be infected.” Her research has found a high infection rate in rats and a certain type of slug on the Big Island. “We tested samples from 545 rats over here, and 94 percent were positive,” she said by phone from Hilo.
Anna Koethe, a spokeswoman for the Health Department, advised:
>> Treat all rats, slugs and snails as if they are potentially infectious, regardless of whether that can be confirmed by a laboratory.
>> Control rats on your property. Clean regularly and clear debris to eliminate potential food sources. Use bait and traps to catch rats, following label directions. Keep pets and children away from any poison used. Monitor traps and dispose of rats in a sealed double bag. Always wear gloves; never touch rats directly. Rats perpetuate the life cycle of the parasite (Angiostrongylus cantonensis) that causes rat lungworm disease. Although rats cannot spread the parasite directly to humans, they spread it to slugs and snails, and also carry and spread other serious diseases such as leptospirosis and murine typhus.
>> Try to eliminate slugs and snails around homes, gardens and farms. Slug baits can be used; follow label instructions and keep away from pets and children. Dispose of slugs and snails in a liquid-tight container with a saline solution (seven parts water to one part salt). Wear gloves and use a device, such as tongs or chopsticks, to collect and dispose of them.
>> Never consume raw or undercooked slugs, snails or other intermediate hosts. Thoroughly rinse and rub all fruits and vegetables, especially leafy greens, under clean, running water to remove slugs, snails or other pathogens. Cooking food by boiling for three to five minutes or heating to an internal temperature of 165 degrees Fahrenheit for at least 15 seconds will kill the parasite and prevent any potential infection.
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