They’re huge and slimy, and they’ve been spotted slinking across parts of southern Florida. Meet the giant African land snail, a dangerous invasive species spreading in Florida. Each of the animals can grow bigger than a person’s hand—up to 20 centimeters (8 inches) long and 10 cm (4 in.) wide. And they carry another unwelcome guest—a parasite that can cause a life-threatening infection in humans.
Scientists believe people first brought the snails, which are originally from East Africa, to the U.S. as pets. Some of the animals escaped or were released into the wild, where they thrived. The snails breed quickly. That’s because they can switch genders, allowing them to mate with any other giant African land snail. And each snail can lay up to 1,200 eggs a year. The creatures aren’t picky eaters, either—they can feed on plants not found in their natural habitat.
Testing of the snails in and around Miami, Florida, found that many carried a parasite called rat lungworm—a tiny worm-like animal. “Snails are good hosts for the parasites,” says Deborah Iwanowicz, a biologist at the U.S. Geological Survey. “There are a lot of different places for parasites to hide, whether it’s between the snail and its shell or in the snail’s body.”
Rat lungworm can infect people if they eat undercooked or raw snails or fruits and vegetables that have become contaminated by snails. The parasite can cause meningitis, an infection that leads to a dangerous inflammation of the membranes around the brain and spinal cord. Florida is hunting down the invaders and using pesticides to prevent the snails—and the disease they carry—from expanding further.