Frog Herbicide Exposure Increases Risk of Dying from Fungal Disease

Amphibians are declining across the globe. The increase of pollution and changing climate are drastically impacting these animal populations. Now, scientists have discovered something else about this amphibian decline. It turns out that the combination of the herbicide atrazine and a fungal disease is particularly deadly to frogs. The findings could help inform future decisions about where and when to use this particular chemical.

"Understanding how stressors cause enduring health effects is important because these stressors might then be avoided or mitigated during formative developmental stages to prevent lasting increases in disease susceptibility," said Jason Rohr, one of the researchers, in a news release.

In order to examine how atrazine might impact frogs, the researchers exposed frogs to the compound. They found that a six-day exposure to environmentally relevant concentrations of atrazine, one of the most common herbicides in the world, increased frog mortality 46 days after the exposure, but only when the frogs were also exposed to the chytrid fungus. It's likely that the atrazine exposure reduced the frogs' tolerance of the infection.

That's not all the researchers found, though. They also discovered that there was no evidence of recovery from the atrazine exposure and the atrazine-induced increase in disease susceptibility was independent of when the atrazine exposure occurred during tadpole development.

"These findings are important because they suggest that amphibians might need to be exposed only to atrazine briefly as larvae for atrazine to cause persistent increases in their risk of chytri-induced mortality," said Rohr in a news release. "Our findings suggest that reducing early-life exposure of amphibians to atrazine could reduce lasting increases in the risk of mortality from a disease associated with worldwide amphibian declines."

The research not only reveals that chemicals can impact amphibians throughout their lives, but also show the complicated interplay between pollutants and disease. Fungal infections are severely impacting amphibian populations. The fact that there are more pollutants in the environment could be partly to blame for this issue. By identifying which, when, and how stressors cause enduring effects on disease could lead to preventative measures that might help amphibians in the future.

The findings are published in the journal Proceedings of the Royal Society B: Biological Sciences.