South Florida residents are being warned to be on the lookout for one of the world's most destructive invasive species: the giant African land snail, which can grow as big as a rat.

The huge mollusks were first spotted in Florida in 2011, and their numbers are growing, Reuters reports. More than 1,000 are being caught each week in Miami-Dade County and more will continue to emerge from hibernation in the coming weeks.

The snails can gnaw through stucco and plastic, and attack "over 500 known species of plants ... pretty much anything that's in their path and green," Denise Feiber, a spokeswoman for the Florida Department of Agriculture and Consumer Services, told Reuters.

In some Caribbean countries, such as Barbados, which are overrun with the creatures, the snails' shells blow out tires on the highway and turn into hurling projectiles from lawnmower blades, while their slime and excrement coat walls and pavement.

"It becomes a slick mess," Feiber said

A typical snail can produce about 1,200 eggs a year and the creatures are a particular pest in homes because of their fondness for stucco, devoured for the calcium content they need for their shells.

The snails also carry a parasitic rat lungworm that can cause illness in humans, including a form of meningitis, Feiber said, although no such cases have yet been identified in the United States.

Experts gathered last week in Gainesville, Florida, for a Giant African Land Snail Science Symposium, to seek the best ways to eradicate the mollusks, including use of a stronger bait approved recently by the federal government.

Authorities are also expanding a series of ads across the state on buses, billboards and movie theaters, urging the public to be on the lookout.

"They're huge, they move around, they look like they're looking at you ... communicating with you, and people enjoy them for that," Feiber said. "But they don't realize the devastation they can create if they are released into the environment where they don't have any natural enemies and they thrive."

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