Bat-killing disease identified as fungus

Map showing the transmission of White-Nose Syndrome
www.batcon.org
bats with White-Nose Syndrome hang in a cave in 2006
www.fws.gov

Researchers confirmed the source of White-Nose Syndrome, a fatal disease to bats, to be the fungus Geomyces destructans, an invasive species in North America. The discovery was made last week.

“This is a key step in any new disease that emerges, we need to be able to understand what is causing the disease and what is causing the animals to be impacted by that disease,” said Michelle Verent, a post doctorate researcher who worked on the project with a team of scientists from multiple disciplines organized by the United States Geological Survey.

The exact number of bats that have died is unknown because there were no verifiable numbers of the population prior to the spread of WNS beginning in 2006. The disease was first identified in Schoharie County and in 2008 it was confirmed WNS was killing bats in the Central New York region around Syracuse. The disease affects six species of bats.

Experts conservatively estimate that over 1 million bats have died from WNS in the last five years, which poses a threat to the human population to acquire more insect-transmitted diseases.

A four-year-old girl from the town of New Haven died in August due to Eastern Equine Encephalitis, a rare but serious mosquito-borne disease.

“Bats are a really important part of the ecosystem because of how many insects they consume each year, and that is important both in the potential spread of insect born diseases, such as West Nile and malaria, and things that we can get from mosquitoes,” Verent said.

With a reduction of bats and an increase in insects, there is an additional strain on the agriculture community and the potential for more environmental destruction.

“If we don’t have those bats there to help control those pests, it costs the [agriculture] industry a lot more money, in pesticide application and as well as causes more harm to the environment because we have to use more chemical means of pest control versus having the more natural control,” Verent said.

The fungus, which had been the suspected culprit, was confirmed by Verent and David Blehert through their research with the United States Geological Survey and other organizations.

“Finding out that the fungus is the true cause of White-Nose is not necessarily surprising for us, it is just reaffirming what most people believed and that is an important step because it allows us to focus our efforts further and takes away that temptation to get pulled off in other directions,” said Mylea Bayless, a conservation biologist at Bat Conservation International.

Experts had already been generally operating under the assumption that Geomyces destructans was the cause and will continue to follow the procedures they had been following such as cave closures. They will now be able to focus more closely on the fungus.

“Knowing that will let us then go forth with future studies, trying to look into disease mechanisms and epidemiology of the fungus and ways we can then target the fungus in order to mitigate the disease effects on bats,” Vernet said.

The fungus spores, which cover the nose, wings and ears, eat at the skin of the bat, cause a change in temperature and water levels, and force the bats out of hibernation.

During the time that they are awake, they burn through their hibernation’s fat reserves, said Mylea Bayless, a conservation biologist at Bat Conservation International. This forces the bats to come out of hibernation early, often in mid-winter, to find insects in order to replenish their fat reserves. Many bats to freeze or starve to death.

There is a near 100 percent mortality rate in most caves, often the fungus is most deadly in its second or third year, Verent said. If a cure is found, it is unknown how long it will take for the bat population to return to previous levels, if it can recover.

Since 2006, when the disease was first identified in Howe Caverns, in Howes Cave N.Y., the bat population has been decimated across the eastern portion of North America with deaths in 17 states and four Canadian provinces.

“In order for a disease to occur, you have to have a host as one side of the triangle, a pathogen as the other side of the triangle, and the environment as the last side,” Bayless said. In this instance, the host would be the bats; the pathogen would be the fungus and the environment would be a cave.

One avenue that researchers are investigating is that bats in Oklahoma and Missouri, where the fungus is present, do not seem to be contracting the disease, Bayless said. She speculated that there may be something in those cave environments that changes how the fungus and disease operates.

Humans are unable to contract the disease because they are too warm to be hosts, so the triangle paradigm remains incomplete. However, they can carry the disease so many caves encourage guests to avoid wearing the same article of clothing between caves. Many caves have been closed off to spelunkers to stem the transmission of the disease.