Wild snake populations plagued by a deadly skin disease have become an increasingly growing area of research in Wisconsin.
Jonathan Sleeman, center director at the National Wildlife Health Center located in Madison, said there is a growing number of new and emerging diseases, Snake Fungal Disease being one of the latest.
According to the NWHC website, Snake Fungal Disease gets its name because the fungus Ophidiomyces ophiodiicola has consistently been associated with the skin lesions on an infected snake.
“Once the fungus is established on the snake it’s capable of doing some nasty things,” Jeff Lorch, a research associate at University of Wisconsin School of Veterinary Medicine, said. “It starts outside and can go down into the living layers of skin and even down into the skeletal muscle and damaging bone.”
Lorch said when the first report of this disease came out in 2006, the problem was thought to be limited to the eastern U.S. where the study took place, and therefore not a cause for concern. The inherent challenges of studying snakes also made the research slow to start, Lorch said.
“Snakes are really secretive and hard to find, so it’s really difficult to prove that populations are declining,” Lorch said.
As researchers are finding ways around these challenges, more reports have been funneling in from other parts of the U.S., including the Midwest, Lorch said. The impact on infected populations, he said, results in a difficult recovery.
“Most people, when they think of snakes, probably think of something that lives for two or three years,” Lorch said. “But rattlesnakes can live for up to 30 years. They don’t sexually mature until they’re about 9 or 10, and they only give birth every two to three years.”
Although exposure to the fungus is usually not a problem if the snakes are able to shed their skins or fight off the infections by seeking warmer temperatures Lorch said, it’s whatever is causing them to be unable to fend off the infection in certain years that results in chronic infection and death.
“Climate change is an obvious factor here,” Lorch said. “I think reptiles and amphibians are interesting in that they’re probably the sentinels for how climate change can influence disease.”
He said a trend of years with warmer winters and wet spring times have been associated with worse outbreaks of Snake Fungal Disease. Warm winters may be facilitating fungal growth during hibernation, which could mean a greater likelihood of exposure. Combined with colder, wet spring times, snakes may not be able to get their immune systems “pumped up” when they come out of hibernation to rid themselves of the disease upon exposure.
“We’re dealing with a cold-blooded animal that’s at the mercy of its environmental conditions to regulate its immune system,” Lorch said.
Less work has been done to show the ecological impact that snake population declines could have, compared to other species threatened by fungal diseases, Lorch said. However, he said work is being done to show that snakes do play key roles in the food web, as far as what they consume and what eats them. For example, he said, certain rattlesnakes and other snakes may play a role in lime disease control by consuming rodents, which are primary reservoirs of the disease.
“Looking at the bigger picture context, we’re living in a global environment that’s very much favoring the emergence of these infectious diseases,” Sleeman said. “They’re having pretty profound consequences for public health, for the economy and for wildlife conservation.”