The famous equine inhabitants of coastal Virginia are being threatened by a mysterious illness. Per USA Today, four Chincoteague ponies have been euthanized by the area volunteer fire company that manages the herd, despite getting the best "care money can buy." Also known as Assateague horses, the ponies were suffering from a fungus-like infection that causes painful lesions and had already killed several of the animals earlier this year.
The so-called "swamp cancer," or pythiosis, is caused by Pythium insidiosum and enters the animals' bodies through cuts or abrasions when they step into the water where the pathogen lives. Per the Washington Post, the pathogen causes tumor-like growths that lead to death if left untreated. The four euthanized ponies were the last believed to have been suffering from pythiosis. Authorities said experts are currently working on developing a vaccine to prevent future infections. (In November, experts said a rat disease was proven to have jumped from the rodent to a human for just the second time.)