WNS in Europe

When WNS was discovered in 2006, it was thought to be a problem unique to the northeast. Of course, the syndrome then proceeded to creep south, and it's currently lurking pretty close to my playground on the Cumberland Plateau. But in a surprising twist, French biologists found several bats coated with a white fungus in 2009, and when they studied the DNA, the fungus on bats in France was identical to the fungus affecting bats in the US. The French bats didn't seem sick, though. Weird. Researchers then started to look back through their records and found photos from the mid 1990s of other bats with a white fungus. Back then, nobody paid much attention to this weird fungus since the bats were perfectly healthy. Fungi is really common in caves, so seeing some is usually no cause for alarm. Now, as a result of the revelation that WNS has likely been in Europe for some time, researchers started to theorize that WNS originated in Europe, perhaps many thousands of years ago, and bats co-evolved with the fungus. Perhaps that's why it's not deadly there.

But is it harmless to European bats?

A new paper out today on PLoS ONE titled "Increasing Incidence of Geomyces destructans Fungus in Bats from the Czech Republic and Slovakia" describes how WNS has been found in many new locations in the Czech Republic and Slovakia over the last several years. What these researchers found is disturbing and fascinating at the same time.

The first thing in the paper that interests me is how the number of European caves affected by the WNS fungus increased last winter. At the beginning of the winter, researchers found 33 sites with possibly infected bats. At the end of the winter, they checked again, and found 76 sites. That's a huge increase! But why? But even more disturbing is that some of these bats did appear sick. Some were emaciated or had skin lesions, just like bats in the US. And even more disturbing, bats populations had been growing very slowing, but starting in 2008, bat populations declined. The declines aren't catastrophic as in the US, but rather by a less shocking 8 to 11%. Maybe it's a coincidence. Maybe it's because of WNS. Maybe it's because of something completely unrelated. They don't know.

Even though WNS now appears to be having a negative impact on at least some of Europe's bats, researchers still think it's been there for a very long time. The paper even speculates that the reason European bats don't typically hibernate in huge clusters like in the US is because of evolutionary pressure from WNS. The idea is bats that hibernate in huge clusters are much more likely to be disturbed by other sick bats wiggling around during hibernation. Bats that hibernate in dense clusters also certainly spread disease very effectively among the group, too. So perhaps if WNS affected European bats tens of thousands of years ago, the bats that could adapt to roosting alone or in small groups were better able to deal with the WNS fungus and evolved into the species there today. Perhaps here in the US we're simply witnessing evolution in action. Neat idea, even though that would really suck for our bats.

But there are many unanswered questions with this study, just like there are many unanswered questions about WNS in general. First, if WNS has been in Europe for a long time, why is it showing up on bats right now? Why is it suddenly spreading to new roosts and affecting the health of bats? Is there some kind of environmental disturbance going on? Is there a common denominator between bats or their habitats on both continents? 

The mystery of WNS continues to deepen. I just hope biologists don't start to blame American cavers for this.