Climate Change Drives Wildlife Infections

By Michael J. Caduto 

In the case of snake fungal disease, if the Jedi Knight from Star Wars, Obi-Wan Kenobi, had summoned the power of nature by uttering, “The spores be with you,” he would have been spot on. This infectious organism features minute spores that produce a fungus capable of defeating powerful venomous snakes. Virtually unheard of in the wild prior to 2006, Ophidiomyces ophiodiicola has been found on snakes in nearly a dozen states, including Vermont, New Hampshire, New York, New Jersey, and Massachusetts in the Northeast, as well as Florida, Wisconsin, Ohio, Illinois, Tennessee, and Minnesota

Snake fungal disease, or SFD, causes snakes to develop opaque eyes, scabby scales, and misshapen nodules on their heads and bodies. Their skin swells and thickens, develops ulcers, and sheds prematurely. Because SFD occurs on animals in captivity, where it thrives in warm, moist conditions, some scientists suspect that the fungus may have migrated into the wild as temperatures and humidity have increased. Climate change is also making it easier for diseases to spread during the winter, when many snakes hibernate en masse underground.

Dr. Jeffrey Lorch of the University of Wisconsin-Madison has conducted most of the recent fungus cultures on snakeskins for the U.S. Geological Survey’s National Wildlife Health Center. According to Lorch, “Anecdotal field reports from herpetologists and field biologists suggest that SFD may have occurred in North America for quite some time. O. ophiodiicola appears to currently be widespread in the eastern United States, and we are not aware of O. ophiodiicola being found in wild snakes in other parts of the world. For these reasons, it is entirely possible that O. ophiodiicola is native to North America.” (Lorch’s previous research was instrumental in identifying the fungus that causes white-nose syndrome, which has killed millions of bats throughout the Northeast.)

SFD infects all kinds of snakes—from rat snakes to rattlers. “It is likely that most snake species in eastern North America can contract SFD,” says Lorch, “but we really do not know the population-level impacts at this time or how the infection varies between species. The greatest concern has arisen with snake species that occur in small, isolated populations, for which losses of even a few animals could severely limit the ability of those populations to persist or recover. These include timber rattlesnakes in the Northeast and massasauga rattlesnakes in the Midwest.” All of the massasauga rattlesnakes that were discovered infected with SFD in Illinois died, and the fungus is suspected of having wiped out half of a New Hampshire population of timber rattlesnakes between 2006 and 2007.

Timber rattlesnakes are endangered in Vermont, New Hampshire, Massachusetts, and Connecticut, and are believed to be extinct in Maine and Rhode Island. Wherever they do occur, rattlesnakes survive as relict populations that harbor little genetic diversity, so it’s less likely that an individual will emerge that is resistant to SFD. Vermont’s Rutland County is home to two populations that contain the state’s last few hundred individuals. In New Hampshire, rattlesnakes have been reduced to a single population.

The best way to monitor SFD is to report sightings of infected snakes to the appropriate state or federal agency. Take photographs, if you can do it safely. “Citizen reporting,” says Lorch, “can help determine how widespread SFD is, which species are affected, and whether the disease poses a significant risk to snakes across the eastern U.S.”

Lorch urges precautions to avoid spreading the disease, such as disinfecting equipment, clothing, and hands after handling captive and wild snakes. “It is a good idea to prevent wild and captive (particularly exotic) snakes from having any sort of contact with one another if one of the animals may be released back into the wild.”

But why care if snakes disappear? Ecologists and nature writers are rarely asked, “What use are people to the environment?” But we are often obliged to justify the existence of other animals, especially those, like snakes, that are feared and maligned. As predators that slither along the middle links of the food chain, snakes keep populations of prey in check, including grasshoppers, mice, voles, rats, and other critters that frequently damage and destroy crops and gardens. Snakes provide food for larger animals, such as hawks, owls, coyotes, raccoons, and foxes. As part of the natural diversity of life, they help ecosystems to be more resilient.

Snakes also have medical uses. Ironically, snake venom is employed to culture a serum for treating poisonous snakebites. Venom is administered in measured doses to horses and sheep; the antibodies to snake venom are then derived from the animals’ blood. Several drugs are based on snake-venom proteins, including eptifibatide and tirofiban, which are used to prevent blood clots in patients who are suffering minor heart attacks, or those who are having chest pains and other symptoms of an impending heart attack. When administered in time, these drugs can help prevent a full-blown infarction. 

And where would humans be without these iconic animals to challenge us and serve as a force against which we take our measure? Although many people revile them, snakes and other reptiles inspire a sense of excitement, awe, and mystery. As the Hydra to our Hercules, they keep us strong and make us feel alive.

The proliferation of fungal disease in snakes, bats and other animals in recent years has been catalyzed by global warming. Photo by Pavan-Krishna on Unsplash.

Portions of this article adapted with permission from Through a Naturalist’s Eyes: Exploring the Nature of New England by Michael J. Caduto.