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A Deadly Fungal Disease Threatens Snakes Across The Globe

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Rachel Baxter

Copy Editor & Staff Writer

clockDec 21 2017, 14:07 UTC

An eastern racer (Coluber constrictor) showing signs of fungal skin infection, with a characteristic opaque infected eye. © USGS National Wildlife Health Center/D.E. Green

In recent times, nasty fungal infections have led to the deaths of millions of bats and entire species of amphibians. Now it seems that snakes are next on this list of unlucky critters, as a fungal infection threatens their survival worldwide. 

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The disease, known as Snake Fungal Disease (SFD), is caused by the fungus Ophidiomyces ophidiodiicola. So far, it has been identified in snakes in at least 16 states in the US, with three cases being recorded in Europe. While diseases can often be specific to certain species, the fungus seems to infect snakes indiscriminately, causing symptoms in rat snakes, milk snakes, vipers, and more. In fact, it has infected 23 American species and three European ones thus far.

“It's about as bad as you can get,” Dr Frank Burbrink from the American Museum of Natural History told Science News. “It seems like any snake could be a candidate.”  

The disease is picked up by snakes from spores in the soil. It causes lesions in the snake’s skin, and can spread across the body very rapidly. Symptoms include opaque infected eyes and discolored, crusty scales. 

"They start getting these blisters and then all kinds of secondary infections from it, it can kill snakes quite rapidly actually, I've seen them go down in a matter of a few days," Burbrink told BBC News. He added that “it can have 100 percent mortality in some" populations.

This is a northern water snake (Nerodia sipedon) with crusty and thickened scales overlaying raised blisters as a result of a fungal skin infection. © USGS National Wildlife Health Center/D.E. Green

As well as causing nasty skin lesions, SFD can alter a snake’s behavior. Those infected spend more time basking in the sunshine when molting, making them more vulnerable to predators and more likely to starve to death.

Not enough is known about the disease, so Burbrink and a team of researchers decided to investigate further. They created a model based on data on the infected species, including their physical features and evolutionary history. Using the model, they could work out which other species of snake might be at risk.

The team found that the 98 “phylogenetically and ecologically diverse” snake groups found in the eastern US were all susceptible to the disease. Their findings also suggest that SFD could spread around the world, creating a pandemic that would threaten the survival of snakes across the globe. The findings are published in the journal Science Advances.

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This is not the first time this kind of outbreak has been witnessed. Over the past few years, amphibians around the world have been under attack from a kind of chytrid fungus called Batrachochytrium dendrobatidis. In fact, the disease has been described as “the worst infectious disease ever recorded among vertebrates in terms of the number of species impacted, and its propensity to drive them to extinction.” Scientists are concerned that SFD could go the same way.

Many frog species are only just clinging on, let's hope snakes don't go the same way. Ghiglione Claudio/Shutterstock

"We don't really know if it's getting worse all of a sudden, there are a lot of question marks, we have got to start getting a handle on this and assess how really bad this is,” Burbrink told BBC News. “We know it can be bad but we don't how bad it really is."

From witnessing the demise of amphibians, scientists know the terrible impact that fungal diseases can have on wildlife. Therefore, the team behind this recent study emphasize that action must be taken, both by researchers and decision makers, to better understand the disease, find ways to treat it, and determine how to prevent its spread.


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