Horse Racing

Chincoteague Pony ‘Swamp Cancer’ Still Stumping Scientists


A particularly bad case of pythiosis. Photo courtesy Danette Wells

The Chincoteague National Wildlife Refuge is home to the beloved Chincoteague ponies. In the last three years, eight mares have been put down because of equine pythiosis , also called swamp cancer, a mysterious microorganism that thrives in warm, wet areas of the country, mostly on the Gulf Coast. With climate change, the disease has moved north, into Virginia.

Dr. Charles Cameron has been treating the Chincoteague ponies on the island for 30 years. There are 142 ponies today; he generally sees the lesions common with swamp cancer in August and September, when the weather has been warm for quite some time. However, one Chincoteague pony began exhibiting signs of the disease in early July.

As summers become hotter and wetter, scientists expect swamp cancer to become more prevalent in the environment. The organism is most likely living in the freshwater ponds in the Chincoteague National Wildlife Refuge, where the ponies live.

The organism that causes the disease is essentially a water mold that behaves like a fungus, creating coral-like lesions on the horse’s legs that spread up the legs and abdomen to the point where the horse must be euthanized because of pain.

The pathogen has long filaments that reach into the horse’s tissue to collect nutrients, like plant roots do, infecting tissue as it goes. Research into the disease is ongoing, as is research on disease prevention, through vaccines or other treatments.

However, the ponies that live on Assateague Island are not infected with swamp cancer. Part of this is believed to be because the watering holes contain salt water, in which equine pythiosis can’t survive.

A veterinarian from Oklahoma, Richard Hansen, has developed a vaccine for swamp cancer and has been trying to determine if horses that are immunocompromised are more likely to get the disease. Though promising, it’s still too soon to call the vaccine a success.

Moving the herd of horses elsewhere in the refuge where swamp cancer has not been detected has also been discussed in addition to vaccinations.

Read more at Fredericksburg.com





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