Washington, Jun 24 (IANS): As the virus responsible for Covid-19, SARS-CoV-2, puts new focus on zoonotic pathogens, a researcher at Washington State University has developed a method to use environmental DNA (eDNA) to detect disease in the vast international trade of aquatic animals.

Currently, creating a "clean trade" by detecting infections in these populations requires huge sample sizes, a labour-intensive and costly process.

In a paper published in the journal Scientific Reports, Associate Professor of Disease Ecology Jesse Brunner outlined two potential ways to test captive animals for pathogen DNA: batching test samples from individuals and sampling eDNA from the water in the animals' tanks.

The eDNA method proved to be much more efficient, Brunner said.

"The best way to prevent the emergence of these pathogens, and the diseases that come from them, is to keep them from getting here in the first place," said Brunner.

"It's an important goal but a really hard one because of the scale of the problem. With the eDNA method you are theoretically sampling an entire population at once, so you are more likely to detect whatever is there, and you can do that much more efficiently than with traditional approaches."

Brunner thought it might be useful to sample water from the tanks of captive species being transported in the pet trade since infected animals will shed pathogens into their water.

As an example, Brunner used Bsal (Batrachochochytrium salamandrivorans), a chytrid fungus which threatens salamander populations.

Bsal is a cousin of the devastating Bd (Batrachocytrium dendrobatidis) that was responsible for the decline of more than 500 amphibian species around the world, including 90 that likely went extinct.

Now Bsal has jumped into wild salamander populations in Europe from imported pets from Southeastern Asia.

While it has not yet been found in North America, the threat of Bsal prompted the US Fish and Wildlife Service to enact a ban in 2016 on the import of 201 species of salamanders into the US, which is home to tremendous salamander diversity.