CHINCOTEAGUE, Va. (Delmarva Now) — The feral Chincoteague ponies may be different than a typical domestic horse, but they're currently facing a very traditional horse issue: "swamp cancer," an often-deadly disease that leaves the ponies with lesions on their bodies.
Seven ponies have been afflicted, said Denise Bowden, spokesperson for the Chincoteague Volunteer Fire Company, which manages the ponies. She estimated initial treatments for the disease will cost about $1,500 per pony.
Swamp cancer is not a true cancer, but rather a disease caused by the oomycete Pythium, which is similar to a fungus. Its medical name is "pythiosis," and the disease also has the ability to affect human beings, dogs and other large animals, although not as frequently, experts say.
Those people caring for the ponies have known about the disease for a while, but it came to the forefront of people's attention following the fall pony roundup Friday, Oct. 12, and Saturday, Oct. 13. Bowden said two ponies died from swamp cancer last year.
This year, however, the ponies are expected to be just fine for the most part. The ponies have not been responsive to an antibiotic, but they are undergoing a new treatment that has a success rate as high as 80 percent.
For a long time, the disease was considered expensive and almost entirely uncurable. In many veterinary schools, it is still taught that way, said Bob Glass, owner of Pan American Veterinary Labs in Lexington, Texas, about 50 miles from Austin.
"It used to be considered a curse because there weren't any treatments that really worked," Glass said. "It used to be that owners would spend between $5,000 and $10,000, and the horse would still die."
Glass has treated swamp cancer in horses before and is likely one of the people who can best be considered an expert on the disease, but he says even he doesn't know that much about it.
What is known is that the infectious agent Pythium insidiosum typically lives in plants that grow near water. When the plants are wet or are submerged in water for whatever reason, it releases zoospores, which are effectively spores that can swim, into the water.
Those zoospores can spread infection by getting into holes on an animal's body as small as a mosquito bite or a scrape. Glass said the disease has a low infection rate, but it can be very difficult to get rid of once it gets into a creature's body.
Swamp cancer creates an autoimmune response in horses that is similar to an allergic reaction, but the reaction doesn't kill off the pythium in the body. Glass, working with other experts, helped to develop an immunotherapy treatment similar to a vaccine to help a horse's body instead respond in a way that gets rid of the disease.
Bowden said those caring for the ponies were exploring a different treatment, one that involves surgery. It should begin soon and last for at least a few months.
"When humans and household pets come in contract with it through a small cut or scrape, it's easy to treat because it's detected early enough," Bowden said in an email. "Our wild ponies go for days without anyone seeing them so when the issue has been spotted and we bring in the pony, the fungus is running amuck."
People at the volunteer fire company are working with experts around the country, including veterinarians from Texas and biologists from the U.S. Fish and Wildlife Service, Bowden said. They are hoping they will be able to test areas in which the ponies roam to figure out more about the disease's origins in the Chincoteague ponies, although Bowden said it has been making its way up the coast for a while.
There are two key reasons the disease has grown in prominence in recent years, Glass said. The first is that 20 years ago, people didn't know what swamp cancer truly was, what caused it or how to treat it. The second, and perhaps the more causal one, is that recent weather patterns in Delmarva have made it more likely for plants with Pythium to grow and release spores.
"Pythium likes warm and wet areas, areas with a lot of flooding," Glass said. "When you have a hot summer that shrinks bodies of water, the plants will grow toward the water. When that water fills back in, the disease spreads."
Swamp cancer has been found in many parts of the southeastern United States as a result, Glass said.
Many fans of the Chincoteague ponies have expressed great concern for the animals on the Chincoteague Volunteer Fire Company's Facebook page, thanking those who care for the ponies and offering to raise money if necessary.
For now, Bowden emphasizes the ponies just need time and care.
"It’s going to take a lot of love and care (we have plenty of that!) to administer this medicine and procedures," a post written by Bowden on the fire company's Facebook page reads. "WE ARE CONFIDENT that we are going in the right direction. Will keep you posted!!"