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Changing Climate May Be Moving A Subtropical 'Swamp Cancer' North To Chincoteague

Pamela D'Angelo

For the last three years, a herd of wild ponies that live at Chincoteague National Wildlife Refuge, have been under attack by a deadly microorganism usually found in tropical and subtropical climates. So far, eight female ponies have died. 

Scientists from the University of Florida and North Carolina State University have been  brought in by the U.S. Fish and Wildlife Service to help determine where the organism, called Pythium insidiosum, is living in the refuge.

“We're trying to find out where the organism is and what habitat it might hang out in,” said Refuge Manager Nancy Finley. “And then there's the other front the fire company is taking the lead on, which is to find out what's going on with the health of the horses and what we can do to prevent the disease through vaccines or treatments.”

The organism has been infecting the ponies with the disease pythiosis, which causes coral-like lesions called kunkers, on the legs or abdomen of the ponies. It moves quickly through the animal.

Local veterinarian, Charles Cameron has been treating the ponies since the disease first appeared. He says another pony began exhibiting the disease's tell-tale lesions in early July and had to be put down. “This was unusual," he said typically, they've seen the lesions in late August and September. “It's a factor of temperature, warm weather and stagnant water. The last few years we've had pretty wet springs, a lot of standing water and warm weather."

The region's changing climate is creating an ideal environment for the disease.

Erica Goss, a scientist from the University of Florida, is taking water samples in fresh water reservoirs and ephemeral ponds that fill and empty naturally.  

Credit Erica Goss / University of Florida
University of Florida
petri dish growing the oomycete Pythium insidiosum

“We got some samples from Chincoteague in June, and some of the water temperatures where those water samples were taken were up to 100 degrees,” she said. “This pathogen thrives in the wet. It can only reproduce and spread when there's available water. So, as the summers become hotter and wetter, we do expect it to be more prevalent in the environment.”

Gustavo Machado, a scientist from North Carolina State Univeristy who studies the evolution and spread of infectious diseases in swine, poultry and horses, is assisting the effort. He says the microorganisms living in the refuge may enter a pony's body through a bug bite or a cut.

“It's super hard to tell, exactly,” Machado said. "There's not much research on that. That's one of the reasons why we're here trying to understand more or less how this is spreading in this area."

Machado, Goss and Finley believe the organism may be found naturally throughout the Eastern Shore.

“It's an organism that's in the environment,” said Finley. “So, there may be the same organism here as there may be in Chincoteague itself or anywhere else in the Eastern Shore.”

Just an hour's drive north of Chincoteague, in Assateague Island National Seashore, a park ranger waves wild ponies away from the state road that leads into the park. Here, the ponies have free range in the park's 6,000 acres.

Allison Turner is a biological technician who helps maintain the herd. She says they've had no cases of equine pythiosis here. “We do monitor the horses, do a complete survey six times a year,” she said. "We have so many people that are very interested in [the ponies] and they're looking at them all the time. So, if this was to show up in our population we would see it.”

Turner said the habitat in Assateague is different than in Chincoteague. The watering holes are small and widely spaced, and salt water washes in. Pythium can't live in salt water.

“So that would prevent the spread of it,” she said, quickly adding, “That's speculation, we don't know that for a fact but that could be the reason we don't have it up here. We don't know, we really don't know."

Back at the Chincoteague Refuge, Machado has already used data to map out areas he considers hot spots for the microorganism. Pythiosis is normally found in tropical and subtropical places like Brazil, where Machado is from. He will look at how climate change might affect the spread of the organism along the Eastern Shore.

“With climate change, we don't know yet how this is affecting things,” he said. “There is a possibility to try to project to the future to see where within this region where this is likely to be present. So, still a lot of work to be done one that.”

The team hopes to return to continue their research in the fall.

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