The search for answers to protect Central American frogs from extinction is giving scientists like UMass Boston Assistant Professor of Biology Douglas Woodhams clues on how to predict and respond to emerging diseases and epidemics in humans, other wildlife, and plants.
Woodhams is one of the coauthors of a paper published Thursday in Science that documents the recovery of some tropical amphibians following continued exposure to a lethal pathogen, Batrachochytrium dendrobatidis, which causes the disease chytridiomycosis and has been linked to population declines in amphibian species around the world. Disease outbreaks rarely annihilate the host species because pathogens need their hosts in order to survive and reproduce. Since diseases can shift to become less deadly over time, Woodhams and his fellow scientists tested whether this was happening in Panama.
“Because we have pathogen and host samples from before, during, and after the epidemic, we can ask whether some frogs survived because the pathogen grew weaker through time, or because the frogs’ immune systems or resistance increased through time,” said Jamie Voyles, a disease ecologist in the Department of Biology at the University of Nevada, Reno and the lead author of the paper. “We found that nearly a decade after the outbreak, the fungal pathogen is still equally deadly, but the frogs in Panama are surviving and may have better defenses against it. This suggests that some of Panama's frogs may be fighting back.”
The study found that nine species of Central American frogs that reached critically low numbers are showing evidence of recovery. Some species even developed defenses that are more effective than they were before the chytridiomycosis epidemic took hold. However, not all frog species rebounded; some species are still missing.
“This is hopeful news for amphibians, but it does not mean that the problem of amphibian population declines is solved,” Woodhams said. “Instead, this study provides clues for how amphibians are able to resist a deadly disease, clues that will be of great importance to better conserve amphibian diversity, and to inform us about outcomes of other wildlife diseases in our ever-changing world.”
For his part, Woodhams looked at immune defenses of amphibians before and after chytridiomycosis emerged in Panama.
“One of my personal highlights was finding Panama rocket frogs in January of this year that I haven't seen at the site for 10 years. I never thought they would return, but now the population seems to be recovering!” Woodhams said.
Understanding how amphibian communities are recovering after this disease outbreak is important for multiple reasons. The study’s findings suggest that recovery after epidemics is possible, but likely a slow and gradual process, which underscores the importance of continuing to monitor amphibian populations.
“Clarifying how disease outbreaks subside will help us predict, and respond to, other emerging pathogens in plants, wildlife, and in humans,” Voyles said. “These are increasingly important goals in a time when rapid globalization has increased the rate of introduction of pathogens to new host populations.”
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