New Infectious Tadpole Disease Discovered

By Dana Kobilinsky

Tadpoles swim through a garden pond. Scientists recently discovered a new infectious disease that is infecting tadpoles and frogs globally.

Image Credit: Timo Netwon-Syms, licensed under cc 2.0

Scientists have discovered that a newly identified infectious tadpole disease exists in a wide range of frog populations around the world.

In a new study published in the Proceedings of the National Academy of Sciences, researchers from the University of Exeter and the Natural History Museum in London explained the molecular methods they used to test tadpoles around the world for the disease.

The researchers tested tadpoles from six countries across three continents including the United States, the United Kingdom, Tanzania and Cameroon for protists, or single-celled microbes that store their DNA in a nucleus. They detected the parasite that causes the disease in the livers of tadpoles in tropical and temperate sites as well as in tadpoles in all of the continents that they tested.

“Global frog populations are suffering serious declines and infectious disease has been shown to be a significant factor,” said Thomas Richards, a professor at the University of Exeter in a press release. “Our work has revealed a previously unidentified microbial group that infects tadpole livers in frog populations across the globe.”

The researchers identified the infectious agent as a distant relative of Perkinsea sp., a parasite found in marine animals and algae and is known for causing mass-mortality events in commercial shellfish. They believe that this particular infectious disease, which causes frog tadpoles to develop an enlarged yellow-color liver filled with protist cells of the parasite, is likely aiding in the species decline.

Amphibians, including frogs and tadpoles, are one of the most threatened types of wildlife. Further, amphibian population decline is often used as an example when researchers consider the earth’s sixth mass extinction event — extreme biodiversity loss due to human activity.

While researchers have only just scratched the surface of infectious agents like this parasite, the researchers say that more research must be done on the diversity and geographic distribution of diseases caused by agents such as this, especially since amphibians tend to be more prone to emerging diseases whether they are viral or fungal.

“We now need to figure out if this novel microbe — a distant relative of oyster parasites — causes significant disease and could be contributing to frog population declines,” Richards said.

Dana KobilinskyDana Kobilinsky is a science writer at The Wildlife Society. Contact her at dkobilinsky@wildlife.org with any questions or comments about her article. You can follow her on Twitter at @DanaKobi.

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