MIAMI — The giant African land snail, which can grow to the size of a fist and carries a parasite that causes meningitis, was declared extirpated from South Florida last year after a decades-long human-versus-pest battle.
They are baaaack.
The fearsome slugs — 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 found outside of South Florida.
To try to contain them, state officials placed part of Pasco County in the New Port Richey area under quarantine this week. No plants, yard waste, debris, compost, or building materials can legally be removed without a permit, for fear that clinging molluscs will spread. The quarantine extends within about a half-mile radius of the identified snail population and may change or increase if more snails are found.
The snails’ comeback was a surprising and unwelcome development in a state where wildlife regularly makes headlines — a record-breaking, 215-pound Burmese python was captured in the Everglades late last year — and where invasive species routinely wreak havoc. During one particularly rainy spring a few years ago, exterminators in Palm Beach County received a flurry of calls about Bufo frogs, whose toxin is so poisonous it can kill dogs found mating in swimming pools.
“Pasco County is a lot drier than South Florida because you have a lot of brush,” said Bill Kern, an associate professor at the University of Florida who specializes in nuisance wildlife management. Giant African land snails generally “like moist and dense vegetation.”
“Of course, in areas that are irrigated, such as 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 plaster, “as a source of calcium”. They hide in cool, moist places during the day, feed at night, and lay many thousands of eggs in their lifetime. Some snails can grow up to eight inches long and five inches wide.
They can also carry a parasite, the rat lungworm, which causes meningitis in humans and animals—if, say, people eat unwashed lettuce or other produce on which the host snail has slithered, leaving behind a trail of mucus.
“DO NOT HANDLE SNAILS WITHOUT GLOVES!” warned the Ministry of Agriculture.
Dealing with invasive species that are destructive rather than just a nuisance can be very expensive, Dr. Kern noted. Florida residents spend about $100 million a year to fight a single pest: the West Indian drywood termite.
On Wednesday, the state began treating a quarantine area in Pasco County with snail bait that contains metaldehyde, a pesticide approved for use on vegetable and ornamental crops, fruit trees and other plants that disrupts the digestive system of giant African land snails and kills them.
Mellon, a rescue Labrador specifically trained to detect giant African land snails, was “actively scouting” the area, according to the Agriculture Department, which has several pest-sniffing dogs. (They sit down when they smell a snail.)
Florida has exterminated snails twice before: last year, after they appeared in Miami-Dade County in 2011, and in 1975, after they were first discovered in the state in 1969. The Department of Agriculture announced in 2021. , that the giant African land snail had not been found in Miami-Dade County since 2017 after an eradication effort that collected more than 168,000 snails.
The snails identified in Pasco County look different than those previously seen in Miami-Dade County: Their flesh is creamy white, not grayish brown.
The discoloration has state officials suspecting that Pasco County’s snail population may have started from a pet snail released into the wild. The creamy white flesh “is the more desirable trait for the illegal pet trade,” said Christina Chitti, director of public information for the Agriculture Department’s Plant Industry Division. Giant African land snails are illegal to import into the United States without a permit.
It’s just a hunch, though. “We probably won’t know how the population of Pasco County came to be,” Dr. Kern said.
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