Talk about a nightmare in slow motion.

Giant African land snails, which abound in south Florida, are not only threatening to move beyond the Miami area, they’re hauling some ugly passengers. A U.S. Geological Survey study released this week says previous research underestimated the number of snails that carry a parasitic worm that can burrow into humans and cause meningitis.

Researchers led by USGS biologist Deborah Iwanowicz collected the snails in seven of the 21 areas where Florida agriculture officials say they’re concentrated two years ago. They extracted tissue samples for the study and found the rat lungworm parasite in a some of the snails they captured.

But unlike previous studies that examined a single tissue sample about the size of a pencil eraser from each snail, Iwanowicz went a step further. She insisted on taking a second sample from a different part of their large bodies.

“Collecting just one additional sample per snail increased the number of snails testing positive for the rat lungworm by 13 percent,” she said.

That spike is reason to believe that previous estimates of the parasite’s prevalence in giant snails were off. A single tissue sample taken from one part of so large an animal, she said, isn’t enough. “This allowed us to confirm that the parasite is not uniformly distributed throughout the snail,” Iwanowicz said.

The research was  published in the Journal of Wildlife Diseases. Other authors include Yvonne Qvarnstrom of the Centers for Disease Control and Prevention, Trevor Smith of the Florida Department of Agriculture and Consumer Services, Lakyn R. Sanders of Cherokee Nation Technology Solutions and W. Bane Schill of USGS.

As giant land snails increase their range in the United States, so does the rat lungworm. The parasite wasn’t previously identified in the areas where the researchers found the snails. Infection is rarely life-threatening to humans, but anyone who picks up a snail to gawk at its awesome girth risks picking up a parasite that causes painful headaches, vomiting and a stiff neck.

Native to East Africa, the giant snails were first imported to this country as pets and educational props in 1966. A Florida invasion was halted by an all-out eradication program in the 1970s, or so officials thought. A reemergence was discovered four years ago in Miami and Fort Lauderdale.

Last year, the Florida department of agriculture went door-to-door in the Miami area as part of a vain attempt to get rid of them again. In all, 150,000 snails were found. Two properties alone were crawling with 700 snails.

Like humans, it takes two snails to make babies. But snails have skills that humans don’t. They’re hermaphrodites that can make eggs without a mate. Or a pair of females can bump into each other and one can switch sexes.

That ability sets Giant African land snails apart from hundreds of other invasive creatures crowding out native animals in Florida — Burmese pythons, Argentine tegus, Cuban tree frogs, Nile monitor lizards and lionfish, to name a few.

African land snails mature sexually in six months. They spawn at least twice a year and lay up to 400 eggs. Thousands can hatch in a year. With production like that, these giants aren’t limited to Miami or Florida.

The Sunshine State isn’t the only suitable habitat, says the U.S. Department of Agriculture Animal and Plant Health Inspection Service. Virginia, Maryland, Alabama, Arizona, California, Georgia, Kentucky, Louisiana, Mississippi, New Mexico, North Carolina, Oklahoma, South Carolina and Texas.

They’ve “expanded globally to areas such as Sierra Lion, Liberia, Ivory Coast, American Samoa, Guadaloupe, East Asia, India and Ghana,” the USGS says. “There are established populations in Hawaii.”

How can they survive in cold areas such as the Chesapeake Bay, well beyond their native tropic?

“These land snails …can withstand severe weather by going dormant for a couple months to over a year,” the USGS says.

Food isn’t much of a problem. “They are known to consume over 500 species of plants, and their range expansion could have deleterious effects on food crops and spread disease well north of the Miami area,” Iwanowicz said.

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