Officials in Florida are again battling a highly invasive, extraordinarily destructive giant snail species that also happens to be capable of spreading parasitic worms that invade human brains.

The giant African land snail (GALS)—aka Lissachatina fulica—can grow up to 20 centimeters (8 inches) long and is considered "one of the most invasive pests on the planet," according to the Florida Department of Agriculture and Consumer Services. It ravenously feasts on over 500 plant species—including many valuable fruits, vegetables, and ornamentals—while prolifically spawning, pushing out several thousand eggs in its multiyear life span. //

While the snails are a grave threat to agriculture and natural vegetation in the state, the invasive mollusks also pose a health risk. They're known to transmit rat lungworm parasites, which can invade the human central nervous system and cause a type of meningitis. For this reason, officials warn people not to handle the mammoth snails without gloves.

Brain invasion
You may recall that rat lungworm made headlines a few years ago when Hawaii's health department tallied more than a dozen cases in 2018 and 2019. In 2018, the Centers for Disease Control and Prevention also published data on several unconnected cases from eight continental states between 2011 and 2017, suggesting a widespread presence.

The rat lungworm—aka Angiostrongylus cantonensis—gets its name by primarily infecting the lungs of rats and other rodents. In the lungs, adult worms mate and females lay eggs, which develop into larvae. The rats then cough up those young parasites and end up swallowing them, then pooping them out. //

From those laden logs, the larvae infect snails and slugs (intermediate hosts), via burrowing into their soft bodies or in the event that the mollusks feast on infected feces. In the last steps of this gut-turning life cycle, rats nosh on the infected snails and slugs, delivering late-stage larvae that migrate from the rodent's stomachs to their brains, where the worms develop into young adults. Those mature worms then migrate back to the rats' lungs for breezy breeding time.

Humans are accidental hosts in this cycle. People pick up an infection by eating undercooked snails or slugs; eating fruits and vegetables contaminated by infected snails or slugs; or eating undercooked animals that may have eaten snails and slugs, such as frogs or crabs. Just like in rats, when the worms are ingested by humans, they make their way to the central nervous system.