MIAMI — The giant African land snail, which can grow to the size of a fist and carry a parasite that causes meningitis, was declared eradicated from South Florida last year after a decadelong battle of people versus pests.
The dreaded snails — known to invasive-species connoisseurs as GALS — were spotted in June by a gardener in Pasco County, north of Tampa, the first time a population of them has been detected outside South Florida.
To try to contain them, state officials placed a portion of Pasco County in the New Port Richey area under quarantine this week. No plants, yard waste, debris, compost or building materials can lawfully be moved out without permission, for fear that the clingy mollusks will spread. The quarantine extends from a radius of about a half-mile from the identified snail population and may change or grow if more snails are found.
The snails’ return was a surprising and unwelcome development in a state where the wildlife routinely makes headlines — a record-breaking, 215-pound Burmese python was caught in the Everglades late last year — and where invasive species routinely wreak havoc. During an especially rainy spring a few years ago, exterminators in Palm Beach County received a surge of calls about Bufo toads, whose toxin is so poisonous that it can kill dogs, found mating in pools.
“Pasco County is quite a bit drier than South Florida because you’ve got that large area of scrub habitat,” said Bill Kern, an associate professor at the University of Florida who specializes in nuisance wildlife management. Giant African land snails typically “like humid, and they like dense vegetation.”
“Of course, in areas that are irrigated, like in nurseries or in home landscapes, they will be perfectly happy,” he added.
Giant African land snails are “one of the most invasive pests on the planet,” according to the Florida Department of Agriculture and Consumer Services. They eat more than 500 types of plants — and also feed on stucco, “as a source of calcium.” They hide in cool, damp places during the day, feed at night and lay many thousands of eggs over their lifetimes. Some snails can grow to 8 inches long and 5 inches wide.
They can also carry a parasite, rat lungworm, that causes meningitis in humans and animals — if, say, people eat unwashed lettuce or other produce that the carrier snail has slid across, leaving behind a trail of slime.
“DO NOT HANDLE SNAILS WITHOUT WEARING GLOVES!” the agriculture department warned.
Dealing with invasive species that are destructive and not just a nuisance can be very costly, Kern noted. Floridians spend an estimated $100 million a year to battle a single pest: the West Indian drywood termite.
On Wednesday, the state began treating the quarantine area in Pasco County with a snail bait that contains metaldehyde, a pesticide approved for use in vegetable and ornamental crops, fruit trees and other plants that disrupts the giant African land snails’ digestive systems and kills them.
Mellon, a rescue Labrador trained specifically to detect giant African land snails, has been “actively surveying” the area, according to the agriculture department, which owns several pest-sniffing dogs. (They sit when they smell a snail.)
Florida has twice eradicated the snails before: last year, after they had appeared in Miami-Dade County in 2011, and in 1975, following their initial detection in the state in 1969. The agriculture department announced in 2021 that a giant African land snail had not been found in Miami-Dade County since 2017, following an eradication effort in which more than 168,000 snails were collected.
The snails identified in Pasco County look different from the ones previously seen in Miami-Dade County: Their flesh is creamy white, rather than grayish brown.
The coloring makes state officials suspect that the Pasco County snail population may have begun from a pet snail released into the wild. The creamy white flesh “is the more desirable trait for the illegal pet trade,” said Christina Chitty, the public information director for the agriculture department’s plant industry division. Giant African land snails are illegal to import into the United States without a permit.
Still, that is just a hunch. “We probably won’t know how the Pasco County population came to be,” Kern said.