July 8, 2020

A necropsy of a native Florida snake reveals pentastomes in the snake's lung.

MELISSA A. MILLER/Contributed A necropsy of a native Florida snake reveals pentastomes in the snake's lung.

FLORIDA — An invasive worm parasite that preys on Burmese pythons has spread to native snakes and invaded farther north than its traditional host’s range, creating a deadly “spillover” effect, according to scientists.

“R. orientalis, this worm parasite, is spreading so well, advancing northward and in areas north of the python invasion. The parasite no longer needs the pythons present to spread,” said Melissa Miller, lead research author and University of Florida/IFAS Fort Lauderdale Research and Education Center coordinator of invasive species research.

Miller first discovered the nefarious blood-sucking worm in native snakes in 2018. R. orientalis, a tongue-shaped parasitic pentastome, is native to Southeast Asia and was brought to Florida by the Burmese python trade in the early 1980s and spread into the wild by released pythons.

It has since been carried by native snakes hundreds of miles north beyond the Burmese python’s usual range. Miller and her team have discovered the parasite between Orlando and Ocala in Lake County. The parasite spreads easily through molted skins and snake feces in soil and could pose a threat to native snake species.

“We found an infected native snake 348 km [216 miles] north of the northernmost infected python. Our data show that native snakes are highly competent hosts of R. orientalis and have facilitated the rapid spread of this nonnative pentastome beyond the range of its invasive host,” biologists wrote in a newly published research paper.

Biologists examined 523 native snakes, 13 species of which were native to the core python region. All 13 native snake species were infected with R. orientalis, according to Miller.

Biologists also examined 1,003 pythons to determine the prevalence and intensity of R. orientalis, 43 of which were from the invasion front. A total of 255 R. orientalis was recovered from 120 infected pythons. All but two of these parasites were from the core region of the python invasion.

Consequently, the parasite’s range has doubled.

“We could have ecosystem-wide impacts from this parasite as it is already spreading up the state, and if it continues to spread across North America, we could see even larger impacts,” Miller said.

Just last year, research led by Terence Farrell, a professor of biology at Stetson University, discovered that the spillover range of R. orientalis exceeded the Burmese pythons range by more than 100 miles.

Farrell and his research associates were alarmed to observe three pygmy rattlesnakes with the parasites crawling out of their mouths.

Native snakes make an ideal host for this pentastome and its health risk to the snakes is unknown.

“Usually, a parasite doesn’t want to kill its host, but in the instance where this species co-invades an area in North America, then our native snakes have not dealt with this species. They have no adaptations or defenses to combat this. They are naïve to this parasite,” Farrell said.

The worm parasite can cause reduced pulmonary function and infection, Farrell said.

The parasites appear to be thriving in native snakes. A female worm can produce thousands of eggs in her lifetime, so the impacts of this invasive species could be far reaching.

“Native snakes are more likely to be infected and have more worms than Burmese pythons,” Miller said. “We also saw that female worms become larger in native snakes than they do in pythons. They’re more fecund and reproductive in the native snake population.

“[The worms] have an indirect lifecycle where they lay eggs in the primary host and they’re expelled through defecation in water and soil then ingested to the intermediate host.”

In Miller’s previous 2018 study, she documented R. orientalis in a shrew.

“That was the first time that we documented a small mammal carrying this parasite. Frog-eating snakes are very likely to spread this worm. It’s likely that amphibians carry it. Invasive tegus carry it. You get a Southeast Asia parasite brought over and it’s now in another non-native tegu species from South America. Native lizards are most likely carrying it, too.”

Miller says the parasite has been found in at least one python in the Keys.

“We looked at about a dozen pythons from the Keys and we did find an infected python from Marathon. The pythons from Big Pine Key and Key Largo were not infected,” she said.

Miller urges people to report python sightings to the Florida Fish and Wildlife Conservation Commission. Take a picture, note the location and report the sighting by phone at 1-888-IVE-GOT1 or online at IveGot1.org.