With white-nose syndrome, a deadly bat disease, continuing to spread across North America, scientists have turned to the examination of bats in China in order to determine how they have lived with an infection that has wiped out millions of North American bats. Now, through the comparison of disease dynamics in North American and Asian bat populations, a team of researchers from the University of California, Santa Cruz, has revealed that Asian bat species are resistant to the fungus that causes the infection.
The team examined hibernating bats at five sites in China and five sites in the United States, ensuring that the samples collected from both countries where taken from areas where the latitude and winter climate are very similar.
Using a standardized swabbing technique, the scientists detected and quantified the amount of fungus present on each bat.
"Uniformly, across all the species we sampled in China, we found much lower levels of infection - both the fraction of bats infected and the amount of fungus on infected bats were lower than in North America," said Joseph Hoyt, first author of the study.
The fungus at the root of white-nose syndrome is endemic to Asia and Europe, where bats have successfully coexisted with it for a many years. Conversely, the disease has only recently invaded North America, with its first discovery dating back to 2006.
"This is the first study to compare disease dynamics in an endemic region and a region where the pathogen is invading, and the results can help us understand the course it might take in North America," Hoyt said.
After numerous tests, the team concluded that Asian bats were likely able to survive with the fungus due to host resistance. In addition, they found that the infection intensity varied between North American species, with big brown bats suffering the least and northern long-eared bats the most.
"The northern long-eared bat suffers really high fungal loads, and nearly all individuals are infected - there's no overlap with the Asian species," said Kate Langwig, co-first author of the study. "From previous work, we've seen their populations crashing toward extinction, so it could be a poor omen for that species."
Although the biological mechanisms responsible for the resistance found in Asian bat species are still not known, they may not be species-specific.
"It doesn't have to be the same strategy for every species - it could be differences in the skin microbiome in one and hibernation behavior in another - but we just don't have those details yet," Langwig said.
The findings were published in the March 9 issue of the Proceedings of the Royal Society B: Biological Sciences.
