New clues on responding to outbreaks

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Researchers at the University of Nevada, Reno, in the US have inadvertently discovered clues on how to predict and respond to emerging diseases in humans, plants and other wildlife while searching for answers to protect Central American frogs from extinction.

“Diseases often shift to be less deadly over time,” said the University’s Jamie Voyles, Assistant Professor in the Department of Biology and lead author on the study. “But we don't fully understand why. In our study, we found that the pathogen, in this case a lethal fungus, remains just as deadly to hosts a decade after it first appeared.”

The researchers discovered that a handful of amphibian species, some of which were thought to have been completely wiped out, are persisting, and may even be recovering, after lethal disease outbreaks. The team has pathogen and host samples from before, during and after an outbreak of chytridiomycosis, an infectious disease in amphibians, which enabled them to ask whether some frogs survived because the pathogen grew weaker through time, or because the frogs' immune systems or resistance increased through time.

“The evidence suggests that the pathogen has not changed. It's possible that the hosts have evolved better defences over a relatively short period of time,” said Voyles. “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 defences against it. This suggests that some of Panama's frogs may be fighting back.”

Voyes said that clarifying how disease outbreaks subside will predict, and respond to, other emerging pathogens in plants, wildlife and humans. “These are increasingly important goals in a time when rapid globalisation has increased the rate of introduction of pathogens to new host populations.”