Rat Lungworm, a Brain-Infecting Parasitic Disease, Found in Invasive Treefrogs in Florida

A deadly parasite that causes rat lungworm disease has been discovered in invasive Cuban treefrogs in Florida.

Researchers at the University of Florida said they had found examples of the parasitic worm, Angiostrongylus cantonensis, in several Cuban treefrogs in a study published in Journal of Wildlife Diseases.

Sixteen Cuban treefrogs in Volusia County were examined and examples of the rat lungworm parasite were found. This is the first time it had been detected in the county.

Rat lungworm infects the brain and spinal cord of humans and can be fatal. It is found in rats, snails, slugs and other animals, including dogs, which can act as hosts for the parasite.

The disease can cause symptoms of eosinophilic meningitis causing severe headaches, vomiting, cranial nerve palsies and various other side effects. The disease can cause brain damage and blindness in human hosts.

People can become infected with the parasite after eating host animals such as slugs by accident or deliberately. An Australian man who ate a garden slug for a dare died eight years after getting infected, having developed a series of complications from the disease.

Rat lungworm is very rare. The Centers for Disease Control and Prevention (CDC) recorded 12 cases of the disease between 2011 and 2017. In most cases, eating raw vegetables where the parasite was present was the cause.

In Florida, Cuban treefrogs are considered an invasive species. They are thought to have arrived in the state as stowaways on ships from Cuba during the 1920s.

Study author Heather Walden said treefrogs probably became a host species as a result of their diets: "They are eating native species, such as green treefrogs, and consuming not just the frogs and other food sources, but the parasites they carry with them," she said in a statement.

Rat lungworm parasites have also been found in snails, slugs and other species—including a gibbon and an orangutan—in the state. The parasites had been found in other counties in Florida including Miami-Dade, Orange, Hillsborough, Alachua, St. Johns and Leon. Cases have also been found in California, Texas, Utah, Colorado, Arizona, Alabama, Tennessee, and New York.

Walden also said dogs are at risk of the disease: "Although rare and not yet reported in Florida, dogs have become infected with rat lungworm by swallowing a snail or slug that carries infected larvae," she said. "It's very possible that a dog could eat a Cuban treefrog, or any other potential anuran host, and become infected as a result.

"The parasite itself is definitely a concern to humans and animals. You have to ask: What would eat the Cuban treefrog, and how would the parasite affect that particular host? And if it does spread to other frogs, it's the same question. What would eat those frogs? What we've found is just touching the surface."

Stock image of a Cuban treefrog
A stock image of a Cuban treefrog. The animals are considered an invasive species in Florida and researchers are concerned they are spreading rat lungworm disease. Alberto Carrera/Getty Images