A recently published article has publicly confirmed suspicions dating back to June of 2012 that the highly invasive species Platydemus manokwari, commonly the New Guinea flatworm, is present in the mainland United States, particularly in Miami, Florida and surrounding areas. This relatively large (about 5.0 cm long and 0.5 cm wide), carnivorous land flatworm is the only organism of its kind to be given a spot on the “100 Worst Invasive Alien Species” list.
The planarian’s native range is unknown, but it is generally believed to be endemic to Papua New Guinea where it was first discovered in 1962. Over the last several decades the New Guinea flatworm has appeared on many Pacific islands, Australia, continental Europe, and now the United States. It persists in tropical and sub-tropical climates, and though it cannot survive in dry areas or anywhere that temperatures fall below about 50°F, it has been observed in a wide range of habitats such as agricultural areas, coastland, riparian zones and other wetlands, forests, and urban areas, typically found in leaf litter.
This hermaphroditic organism can reproduce quickly, but may have difficulty traveling long distances on its own: one study showed that the flatworm took a full year to disperse through urban gardens separated by about 30 meters of lawn. Less is known about its secondary dispersal rate in unfragmented habitat, but its primary mode of dispersal across international boundaries is thought to be the plant trade, as it has been showed to survive in soil and plant parts.
The spread of the New Guinea flatworm is significant for a number of reasons, but one has thus far been given the spotlight in terms of media coverage, that is its threat to native snail populations. This predator has the ability to track the scent of snails on the ground and even up trees; its well-known efficiency in killing snails lead to its intentional introduction to the Philippines in 1981 to control another invasive, the giant African land snail.
Besides being invasive species, the New Guinea flatworm and the giant African land snail have something in common: both are primary intermediate hosts for the rat lungworm, Angiostrongylus cantonensis, which causes meningoencephalitis in humans, an incidental host. A. cantonensis, a nematode, infects humans who ingest vegetables tainted with the worm’s larvae (left behind by the flatworm) which then travel through the bloodstream to the central nervous system.
The parasite’s invasion through the meninges (the lining of the brain) often causes inflammation which leads to headache, stiff neck, and fever. Localized physical brain damage occurs due to the movement of the worms, and the inflammatory response to the presence of dead and dying worms causes secondary damage such as paralysis, bladder dysfunction, visual disturbance, and coma. Long term symptoms include permanent nerve damage, mental retardation, permanent brain damage, and death.
If more articles covered the potential impacts to human life, more would probably be done to limit the spread of this ecological threat across the US and around the globe.