Threatening Amphibian Fungus Could be Curbed Using eDNA Analysis
Amphibian chytridiomycosis caused by the fungus Batrachochytrium dendrobatidis (Bd) is an emerging infectious disease that has been associated with mass mortality and extinctions of amphibians worldwide.
World’s approximately 6,000 amphibian species and many of those species develop the disease chytridiomycosis. In fact, infection with Bd has been called “the worst infectious disease ever recorded among vertebrates in terms of the number of species impacted, and it’s propensity to drive them to extinction.
Amphibian population declines due to chytridiomycosis can occur very rapidly— sometimes over a just a few weeks and disproportionately eliminate species that are rare, specialized and endemic (e.g. those species that are most unique). Because of these characteristics—rapid progression of population declines and loss of very important amphibian species—urgent mobilization of efforts to preserve amphibian species are required.
A new system of analysis called the eDNA could now offer a solution. This new technology being developed at Washington State University could help save amphibians around the world.
Known as environmental DNA, the tool detects telltale bits of genetic material that living creatures shed into their environment, and enables wildlife scientists to confirm the presence of a wide variety of aquatic organisms
without the hassle of finding them. This new study demonstrated how eDNA could provide an early signal of where Bd die-offs may occur which would help conservationists take action to save amphibians afflicted by the pathogen.“If we can predict when an outbreak is imminent, we can proceed with management actions such as anti-fungal baths that kill Bd,” said author of the study, Colleen Kamoroff, a former WSU natural resources graduate student, who is now a wildlife biologist at Yosemite National Park. “Mountain yellow-legged frogs in the Sierra Nevada have experienced a population decrease of over 90 percent in recent years. Environmental DNA could help save these frogs and other species of amphibians around the world from extinction.”
Kamoroff originally went to California’s Sequoia Kings Canyon National Park in 2015 to determine whether eDNA techniques can be used to detect when non-native fish had been successfully removed from high alpine restoration lakes. The lakes are home to two federally endangered species of mountain yellow-legged frogs.
“I was curious if Bd would be detectable at the lakes I took samples from even though there were no sick looking frogs at the time,” Kamoroff said. “So I decided to run the eDNA samples I originally collected for the lake restoration project to test for the presence of Bd.”
Upon further investigation, the team found Bd in the eDNA samples from all three lakes where there was a die-off but did not detect the pathogen in the eDNA samples taken from the other lakes. Their research demonstrates eDNA could be a promising, non-invasive method to screen lakes and other bodies of water for the presence of Bd. Currently, the only way to test for the pathogen is take skin swabs from afflicted amphibians.
“Unlike skin swabs, eDNA does not require the capture or handling of the animals you are trying to protect,” Caren Goldberg, an assistant professor in the WSU School of the Environment said. “We think the technology will prove very useful in preventing the spread of Bd in the future.”
