In a case of illegal snail mail, officials at Los Angeles International Airport intercepted a shipment of 67 live giant African land snails from Nigeria earlier this month.

The mollusks—which can measure nearly 8 inches (about 20 centimeters) long and weigh more than 1 pound (500 grams)—are considered a delicacy in parts of their native Africa. But in the U.S. they're an agricultural pest that does extreme damage.

Authorities believe that the incident—the largest giant African land snail seizure to date in the U.S.—is not a case of smuggling, because neither the sender nor the recipient were aware that the snail is illegal in the United States, the Associated Press reported.

This species was first brought to the continental U.S. in 1966, when a boy smuggled three into Miami as pets. The boy's grandmother later released them into her garden. Just seven years later their population had exploded to 18,000, which cost the state of Florida more than $1 million dollars and took ten years to wipe out.

In 2011, Floridians began noticing a second outbreak of snails, which may have arrived in the state as pets or accidentally in cargo. The pests are well established in Hawaii and the Caribbean.

Each hefty invertebrate can eat up to 500 kinds of agricultural crops and carry a parasite called rat lungworm that can transmit meningitis to people and pets.

The snails are also fond of munching on the Sunshine State's stucco houses to get more calcium for their shells, noted Richard Gaskalla, director of the Division of Plant Industry for the Florida Department of Agriculture and Consumer Services.

"It's like the trifecta of pests—it [can] eat your house, eat your plants, and make you sick," he said. (To date there have been no reported cases of rat lungworm in people or pets in Florida.)

Because the snails have no natural enemies in the U.S., "when they get a foothold, particularly in urban or suburban areas, they multiply quickly," Gaskalla said. The prolific breeders lay up to 1,200 eggs a year-and they live as long as ten years. (Related: "Giant Snails Invading Florida, 'Major Threat' to Crops.")

U.S. restaurants don't use African giant land snails as escargot, which typically comes from smaller land snails that are farmed in Europe and elsewhere, Gaskalla added. (See "Giant Snails, Once a Delicacy, Overrun Brazil.")

Getting Rid of Snails

The good thing, Gaskalla said, is that "because they are such a nuisance, people notice them pretty quick" and call authorities.

That vigilance is paying off. Since 2011, a snail-removal program in Miami-Dade County, run by the Florida Department of Agriculture and Consumer Services, has collected over 140,000 invasive giant African land snails.

"We've made really good progress toward eradication," Gaskalla said.

But, he added, the recent intercepted shipment of snails in Los Angeles—which were later burned by the U.S. Department of Agriculture—is of concern.

"We don't want them moving in the U.S. for any purpose. I've tried to get the word out that it's an invasive species" and that people should not eat them or keep them as pets, he said.