New Guinea Flatworm

Living in Florida there's always the next really bad invasive species that has just arrived or is about to arrive. Seeming the one thing that thrives in our climate more than anything else is the invasive species.

The latest invasive species of great concern is the New Guinea flatworm. This flatworm is a resident of the South Pacific. It feasts on snails and a few other mollusks. In fact they were introduced to many islands in the Pacific to fight invasive snails on the islands.

One more snail bites the dust.

I was confused by the reaction of a news station out of West Palm recently. This flatworm has been around the Pacific for some time. It's been widespread in Hawaii for years and has done some bad things to certain snail populations. But WPTV played up the potential for human disease and saved the devastation of the snail population to the final paragraphs.

The New Guinea flatworm has been occasionally seen in Miami-Dade for a few years. Recently it was found in some plants in Coral Gables.

Identifiable by dark orange stripe

I'm having trouble finding other citations about direct human harm from the flatworm. In I get the feeling that the TV station may have gotten in touch with an expert that really wanted to scare people. These flatworms can carry something called a rat lungworm. That can cause meningitis in humans but transmission from the flatworm to rat to human is pretty rare.

And this is the difference between the health official and a statistician. He has to talk about what can happen. A statistician has the freedom to talk about what's likely to happen. Here's a map of the flatworm distribution in Asia, it's home territory.

New Guinea Flatworm Asian Distribution

Note that the dots are on its home island of New Guinea and also on various islands in the region. Not much at all on the mainland. 

The US shows a similar pattern. They've become established in Hawaii (actually just on the island of Oahu) but almost unknown elsewhere.

Islands are notoriously easy for invasive species to take over. Frequently without predators a species can become widespread in a very short time. But that's not Florida or most mainland areas. Small mammals, birds, snakes, lizards and many other creatures will probably be sufficient to keep a large flatworm in check. In the flatworm preferred habitat of leaf litter in the forest we have lots of small reptiles and amphibians that may learn to like the taste of a large defenseless flatworm.

And it's not a given that these flatworms will cause no damage. Their most likely victims are the various Florida tree snails, a group that's already under pressure from collectors who like their colorful shells.

Florida Tree Snail

I don't know what impact this flatworm will have in Florida. Will the various Florida predators that usually prey on such flatworms keep them in check? Probably. The video from WPTV plays up the fact that the flatworm is away from its usual predators. But predation on islands is notoriously low. If the Florida predators like the taste of flatworm and aren't badly affected the New Guinea flatworm will held in check.