April 16, 2013  -- The giant African land snail may fit in the palm of your hand, but it is posing a big threat to Florida residents.

State officials are worried because the snails carry disease and eat most of the agricultural crops grown in the state, an official said.

When the Florida Department of Agriculture first discovered the current outbreak in Miami-Dade County, they found "massive amounts of these snails at every property we visited," said Mark Fagan, a spokesman.

Barely more than 18 months later, Fagan estimated officials have captured more than 120,000 snails. The largest had a 6.1 inch shell.

"We have a staff of 50 that's dedicated to nothing but snail hunting," Fagan said.

Giant African land snails carry rat lungworm, which the Centers for Disease Control said is the most common cause of human eosinophilic meningitis. The snails often contract the worms by eating rat feces.

Florida's food supply is threatened too, said Fagan.

"They eat 500 different plants," he said.

Florida has more than 9 million acres of farmland. The Florida agriculture industry employs 750,000 people and contributes more than $100 billion to the state's economy.

At least 20 neighborhoods are battling the snails.

According to Fagan, the snails can produce 100 eggs per month and live more than 8 years.

"It's a perfect environment for them here in South Florida," state entomologist Dr. Ian Stocks told ABC News station WPLG.

Fagan said the giant African land snails first came to South Florida in the 1940s as overseas military equipment returned home. Even today, he added, "they're hitchhiking on cargo."

That could mean they're coming in on something as small as a potted plant.

"When they're really small, they're easily undetected," Fagan said.

People usually spot giant African land snails in their backyards and on the sides of homes. In addition to leaves, the snails also eat stucco and concrete searching for calcium.

"Last week, when it rained, I came out and I saw so many that I took a plastic bag and I had more than 40 of them," Reinaldo Rodriguez, a local resident, told WPLG in an April 2012 interview.

It can be difficult to tell the giant African land snail apart for other kinds of snails. It gets easier as they grow larger.

"The stripes on their shell are a dark, caramel brown, with vertical rather than horizontal stripes," Fagan said. "They have a definite spiral."

According to WPLG, workers returned several times to leave bait and collect the snails.

Agriculture officials are treating snail outbreaks with the same compounds found at home and garden supply stores.

If you spot one in your backyard, Fagan said, don't smash or otherwise destroy it. Rather, he recommended calling an agricultural official to dispose of them. He added that officials are making headway in their battle against the giant African land snail.

"We are winning, but it won't be a short-term effort," Florida Department of Agriculture Division of Plant Industry Director Richard Gaskalla told WPLG.