It has a goo-spewing mouth on its belly, is covered in toxic slime, hosts a brain-eating parasite and, like any ambitious mutant monster, the New Guinea flatworm is invading the U.S. by way of sunny Miami.
There’s also this: the worm is hermaphroditic, so it can multiply anywhere, anytime. No assistance needed.
Researchers last month confirmed for the first time that the Pacific island flatworm has been found on the U.S. mainland in four locations around Miami-Dade County. Even tony Coral Gables. The nocturnal creeper clocks in at just two inches, looking more like a smudge of snot than an agile predator. But don’t be fooled by its sluggish demeanor. At mealtime, the worm goes full-on Alien, posing a potentially serious threat to South Florida’s already fragile native snail population.
“It is really vile,” said David Robinson, the nation’s chief snail scientist at the U.S. Department of Agriculture. “As a biologist I can handle most things, but I find this really revolting.”
Sign Up and Save
Get six months of free digital access to the Bradenton Herald
Scientists worry the worm — which is listed by the International Union for Conservation of Nature as one of the planet’s 100 most invasive species — could spread by being transported in garden soil or on plants.
“From Miami, the flatworm can go anywhere in Florida and anywhere in the U.S.,” said Jean-Lou Justine, lead author of a study published June 23 in the online science journal PeerJ and a researcher at the National Museum of Natural History in Paris.
While humans face little risk from the worm, it thrives on snails and will eat any slug, worm or soft critter living in soil. And its appetite is voracious. Robinson has seen pictures of a Giant African Land Snail — another invasive marauder that is the target of a state eradication campaign — being attacked by a pack of 30 to 40 flatworms.
To get around a snail’s armor, the worm latches onto the shell’s opening, then spits its stomach out through the mouth on its belly. An acidic goo from the stomach dissolves the snail’s flesh so the worm can re-swallow both stomach and prey. Time for dessert.
The worm, native to New Guinea, has now been documented in 22 countries, mostly island nations, making its arrival on the U.S. mainland more alarming, said Justine, speaking to The Herald from Paris.
“In the beginning, we are going to find them mainly in gardens because they will be transported from garden to garden,” he said. “The real problem will be if they go into the wild.”
In his study, Justine said the worm was first reported in the U.S. on Southwest 122nd Street in Miami in June 2012. Four months later, another sighting was reported on Northwest Fifth Avenue. Two years passed before a third worm was reported on Southwest 192nd Terrace.
In August 2014, Makiri Sei, another malacologist — the official title for a snail scientist — was in Miami looking for live tropical snails at the Montgomery Botanical Garden on Old Cutler Road. Sei, who works two offices down from Robinson, was hoping to sequence their genomes as part of a project tracing the evolution of land snails in Jamaica.
Because it had been dry, another biologist suggested she look at night. So at about 4 a.m., Sei headed to a spot in the garden where the day before she had seen empty snail shells. Instead, Sei discovered a slimy flatworm and snapped a few pictures.
“I had no idea what they were,” said Sei, who had been to Florida only once before as a child. Back in Philadelphia, she showed the pictures to Robinson, who suspected Sei had found another flatworm.
While they get little attention, exotic snails and slugs have become an increasing threat with growing global trade. Robinson was hired as the first national malacologist in 1995 and has seen outbreaks of invasive snails threatening wheat crops in Montana, Detroit and Washington state. He has also been working with Florida officials to fight the massive African snails that can grow up to eight inches.
“All through the country we have little outbreaks that come through quarantine barriers,” he said. “They come in on pretty much everything: cut flowers, imported fruits and vegetables.”
While the snails can easily hitch their own rides, Robinson said he also has to battle the food and pet trade intentionally spreading snails. The Giant African Land Snail first reached the U.S. when a Miami boy brought back three from Hawaii as pets and let them loose in his grandmother’s backyard. The snail spread, but after a $1 million effort, they were believed to have been all captured or killed by 1975. They are now back, and have spread into Broward County.
Like the Giant African Land Snail, the New Guinea flatworm carries the rat lung parasite, which burrows into the brain and can spread to humans. In April health officials confirmed one case in Hawaii. Most people suffer muscle aches and sensitivity to light and recover without ever knowing they’ve been infected. But in severe cases, the brain can become infected. The flatworms are also coated in a toxic slime that can cause allergic reactions, so should not be handled.
Justine first documented the worm in France — where any threat to escargot is taken with particular concern — in 2013. Media coverage generated reports of hundreds of other flatworms, but none were confirmed as New Guinea, meaning they had not ventured beyond gardens and into the wild.
The worms have devastated snail populations in Guam and on the Mariana Islands, Robinson said, but not in Hawaii, possibly because native snails live in the highlands on Oahu and the Big Island. Populations of invasive snails in lowlands also appear unharmed, he said.
“In the case of Florida, we don’t really have a handle on what it could do,” he said, but pointed out that even after several years it does not appear to have had a significant impact.
“We can hope that Miami is not the best place for it to survive,” he said.
But should they spread, South Florida’s native snail population, already imperiled by shrinking habitat and threatened by climate change, collectors and invasive fire ants, could be in trouble.
“They are no where else to be found,” Sei said. “So once they are gone from South Florida, they are gone from the whole world.”