News Mysterious swamp cancer is killing Chincoteague ponies on Virginia island famous for them December 31, 2018Hayley Harding, Salisbury Daily TimesComments Off on Mysterious swamp cancer is killing Chincoteague ponies on Virginia island famous for them The mysterious disease in Chincoteague killed three other ponies this year and two in 2017. It's a painful disease that covers ponies with lesions.