Dangerous ‘rat lungworms’ show up in Florida snails

The rat lungworm uses snails as hosts and can be dangerous to people, dogs, horses, birds, and other animals. (Credit: Twitter: @NikonHiker/Flickr)

A parasite that can make humans and animals sick is colonizing several species of snails in Florida.

Scientists made the discovery after an orangutan being treated at the University of Florida died from eating snails that carried the parasite Angiostrongylus cantonensis, known as the rat lungworm.

Rat lungworm has been known to be established in snail populations in Hawaii, but until now has not been commonly seen in the continental United States.

Plant transports

The findings, which show the parasite may now be established in South Florida, raise concerns about how it got there and the potential implications for both animal and human health, researchers say.

“Determining the geographic distribution of this parasite in Florida is important due to the hazards to human health,” says Heather Walden, assistant professor of parasitology at UF’s College of Veterinary Medicine and lead author of a new study published online in the Journal of Parasitology.

The rat lungworm, a nematode that can affect both animals and humans, uses the rat as a definitive host and gastropods, such as snails, as intermediate hosts.

Florida’s large horticultural industry makes the parasite’s presence in the state particularly disturbing because plant nurseries are one of its most important modes of transport.

“Most of the snails found to be intermediate hosts for this parasite in our study are invasive and some feed on or shelter on ornamental plants, which have the potential for distribution throughout Florida and in other areas of the United States,” Walden says.

Snail mucus

The new research builds on a previous study, which reported that a 6-year-old orangutan treated in 2012 after exhibiting neurological symptoms, was infected with the rat lungworm. The animal had a history of eating snails.

In 2013, Walden and a colleague visited the Miami area to collect terrestrial snails from the orangutan’s infection site. They sorted snails by size, shape, and color and identified them by species.

The scientists collected mucus from all of the snails and analyzed specimens for the presence of nematodes. Additionally, rat fecal samples were collected from the original infection site and examined for nematodes.

Of five species of terrestrial snails tested, three tested positive for the rat lungworm. One species was the same as the orangutan had ingested, one is a known intermediate host, and the other had never previously been identified as an intermediate host. All of the rat fecal samples contained the nematode.


Walden and study coauthor John Slapcinsky, an invertebrate zoologist who specializes in the study of mollusks at the Florida Museum of Natural History, are now working to identify and process all of the snails collected in the project.

In addition to the danger to humans, rat lungworms can also affect dogs, horses, and birds.

“These species all get similar diseases,” Walden says. “So these findings are of interest not only to companion animal medicine but to human medicine as well.”

The parasite causes a rare and potentially fatal form of meningitis in people, according to the Centers for Disease Control and Prevention, but humans can’t become infected unless they eat an undercooked or raw snail, Walden says.

“Some animal species can harbor the infective larvae, like different crustaceans or frogs. As long as food is cooked and you wash your produce, you will most likely never ingest it.”

Source: University of Florida