In 2008 Matthew Allender, a wildlife veterinarian affiliated with the University of Illinois at Urbana–Champaign, noticed something wrong with some of the rattlesnakes he'd been studying as part of a population-monitoring program near Carlyle, Ill. His team had found three eastern massasauga rattlesnakes ( Sistrurus catenatus catenatus ) with severe facial swelling and disfiguration. Allender brought them back to his lab for observation. The lesions ulcerated and progressed beneath the skin. When the snakes died just three weeks later the disease had deformed their mouths, nasal passages and fangs beyond recognition.