And experts fear the illness, contracted by stepping in contaminated water, will only get worse for members of the famously hardy herd.

Assateague Island Ponies
Credit: sbonk/Getty Images

Sad news out of Assateague Island. A deadly infection known as "swamp cancer" has claimed the lives of seven of the barrier island's famed Chincoteague pony herd.

The fungus-like infection, believed to be contracted by stepping in contaminated water, is being blamed for the deaths of the majestic beauties, including four that had to be euthanized Friday.

"Shadow, Lightning, Calceti'n and Elusive Star as well as the others received the very best care money could buy," Denise Bowden, a spokeswoman for the Chincoteague Volunteer Fire Company, the organization that manages the herd on the Virginia side of Assateague Island, wrote on Facebook. "They just couldn't fight this off."

Unfortunately, experts fear that warmer temperatures come spring will only make things worse for the herd of roughly 150. The wild ponies have called the island off the coast of Virginia and Maryland home for centuries and are a popular tourist destination.

"We're not panicking, but we've never faced a situation like this before," Bowden told The Washington Post. "It's been very, very trying."

The scientific name for the deadly illness is pythiosis, an infection that can result when a horse steps in water carrying the organism Pythium insidiosum. These fungus-like pathogens make their way into the animal's body via small cuts or abrasions and can create itchy, swelling lesions that in some cases go on to become tumor-like growths.

The disease is usually associated with subtropical climates, including Florida. But changing weather patterns have caused it to move as far north as Minnesota.

Charles Cameron, the herd's primary veterinarian for 29 years, told The Post that the herd's problems with "swamp cancer" began two years ago and spiked significantly this past autumn. He added that he's never seen anything like it during his time with the herd—and the wild ponies like the Chincoteague are used to danger.

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Currently, treatment for the infection is both involved and expensive. The Post reports that the herd's caretakers have already spent more than $25,000 on treatments.

As Bowden pointed out on Facebook, this "isn't only a pony problem. It can affect any animal that comes in contact with it."

But the herd's caretakers aren't giving up. There's even a "preventive vaccine" currently awaiting FDA approval.

In the meantime, Chincoteague and its ponies are asking for support. "I ask that when you say your prayers for 2019 that you say an extra prayer for the ponies, the cowboys, the Chincoteague Vol Fire Co as well as the entire island community," Bowden wrote on Facebook.

If you would like to contribute to the care of Virginia's herd of wild ponies, donate here.