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Chincoteague Ponies Battle Swamp Cancer with New Vaccine

Swamp Cancer: A Deadly Threat to Chincoteague Ponies

For over three centuries, the wild ponies of Chincoteague National Wildlife Refuge have roamed the barrier island of Assateague Island. However, a new threat has emerged in recent years: swamp cancer, a deadly ailment caused by the fungus-like microorganism Pythium insidiosum. This disease has claimed the lives of seven ponies since 2017, leaving the herd’s fans and custodians worried.

Swamp cancer primarily infects horses, dogs, and humans. Infection typically occurs through contact with water containing the swimming zoospores of P. insidiosum, which are attracted to open wounds. Once inside a host, the microbe spreads via snaking filaments that it uses to feed on the animal’s tissues.

Climate Change and the Spread of Swamp Cancer

P. insidiosum is primarily found in tropical climates. However, as climate change heats up the globe, cases of swamp cancer have begun to creep northward. The Chincoteague National Wildlife Refuge has conditions that are ideal for the parasite: wetlands with stagnant water and summer temperatures exceeding 100 degrees Fahrenheit. Preliminary tests have shown that the microbe is “fairly ubiquitous” across the refuge.

The Vaccine: A Hope for the Ponies

In response to the threat of swamp cancer, the Chincoteague Volunteer Fire Company, which owns and cares for the ponies, began testing a vaccine in 2019. The vaccine targets P. insidiosum and aims to protect the ponies from infection. While the treatment is still in early stages, it appears to be working. Spokeswoman Denise Bowden said, “We need to continue to vaccinate over the next [two to three] years to tell better if this vaccine was/is an effective tool in this herd along with environmental management practices.”

Saltwater’s Potential Role in Combating Swamp Cancer

Interestingly, the scourge of swamp cancer has spared the herd of ponies on the Maryland side of Assateague Island. Scientists are investigating whether the saltwater in the standing water on the Maryland side may be killing the disease-causing microbe.

Annual Pony Roundup: Monitoring the Herd’s Health

Each spring, the ponies undergo a health checkup. As of April 18, all 160 Virginia ponies were free of swamp cancer. The roundup also targeted a dozen ponies that had yet to receive the experimental vaccine.

Cautious Optimism for the Future

Richard Hansen, the creator of the vaccine, is “cautiously optimistic” about its potential to keep the ponies healthy. “So far, it seems to be doing really well,” said Bowden. “We didn’t have an extremely wet, rainy end of summer last year. I’m thinking that between that and the vaccine, we’re on the right path here.”

The fight against swamp cancer is ongoing, but the new vaccine offers hope for the survival of the Chincoteague ponies. Continued vaccination and environmental management practices will be crucial in protecting this iconic herd.