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Snake fungal disease: potential impacts on European snakes

In the past decade, snake populations in North America have declined – attributed to snake fungal disease. Snakes benefit ecosystems in a number of ways; one of the most important is to keep pest species such as rats under control. As I’m sure you’re aware, in the US snakes are heavily persecuted for events such as ‘rattlesnake roundups’ and harmless snakes are often targeted due to mistaken identity. Over the past few decades, conservationists have worked hard to help these populations recover but now a new nemesis is on the horizon.

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The causative agent for this is a fungus called Ophidiomyces ophiodiicola which has recently been found here in the UK and elsewhere in Europe. O. ophiodiicola has been found on captive snakes outside North America before, but until last year the pathogen had not been reported from wild snakes anywhere else in the world. In the US, the disease infects snake species indiscriminately with most cases leading to mortality or morbidity. In some snake populations such as the threatened Eastern Massasauga rattlesnake (Sistrurus catenatus catenatus), there have been unprecedented declines. You can find out more about the work to prevent this by watching this video.

Many dog walkers and outdoor enthusiasts often encounter snakes whilst they are basking, slipping away into the undergrowth after being disturbed. Snake fungal disease threatens precious chance encounters with these elusive animals as well as the natural balance of ecosystems, which could see prey species become more numerous. Signs of infection include skin lesions, thickened or ulcerated skin, abnormal skin shedding and nodule formation. Due to the deformities caused, snakes will often behave oddly (which is always a sign that’s something is wrong with a wild animal), if you observe what you believe to be an infected snake in the wild, it’s best that you report it through the Garden Wildlife Health project. It’s important to act quickly as infected snakes my die from dehydration or starvation.

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Unfortunately the symptoms listed above are not only restricted to snake fungal disease, but a number of diseases. Genetic investigation and microscopic diagnostic tests are therefore needed to confirm the presence of snake fungal disease. Swabs can be taken from live snakes in order to run the diagnostic genetic test, using equipment to test for the presence of snake fungal disease DNA (similar to that used on CSI). Evidence already collected by the Garden Wildlife Health project (and volunteers around the country) has shown that snake fungal disease is present in the UK where it was predominantly present in the grass snake (Natrix helvetica), but also in the adder (Vipera berus). Post-mortem examinations and archived sloughs were investigated using screening techniques in order to screen for O. ophiodiicola. Both of these snake species are declining across the UK due to habitat loss, persecution and fragmentation. Snake fungal disease adds yet another stressor that could impact these already threatened populations.

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What does this mean for our British snakes? Not much is currently known, but by looking at how the snakes of North America have been affected; the future unfortunately doesn’t look bright. Thanks to the research that has already been completed we know that snake fungal disease is already widespread within the UK. For my PhD, I’ll be researching the population dynamics of grass snakes whilst also investigating the potential effects on snake fungal disease on the species at a population level.

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Fortunately we only have three native snake species compared with fifty snake species found in the US, so untangling the effects will be simpler. Snake fungal disease could be the stressor that pushes the smooth snake (Coronella austriaca), Britain’s rarest snake to extinction. By learning how the disease works at a population level, we can try to mitigate its effects as it’s unlikely that we’ll ever be able to find a suitable cure to use at a landscape level.

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Unfortunately if we don’t act now then we will lose some truly spectacular species from our already impoverished amphibian and reptile assemblage. Without predators such as snakes to keep them in check, prey species such as frogs and rats could reach biblical proportions – which would be a disaster for us all!

steve author

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