Scientists have traced a deadly fungus responsible for killing frogs, toads, and newts worldwide to the Korean peninsula, sparking new calls for a halt to the international amphibian pet trade.
A dangerous infectious disease with the potential to drive species to extinction, Batrachochytrium dendrobatidis (Bd) is also known as chytrid fungus.
The skin infection, passed from animals in the wild to pets, causes chytridiomycosis, which affects amphibians' ability to regulate water and electrolytes and may lead to heart failure.
"Biologists have known since the 1990s that Bd was behind the decline of many amphibian species, but until now we haven't been able to identify exactly where it came from," said Simon O'Hanlon of the department of infectious disease epidemiology at Imperial College London, co-author of the report in the journal Science. "In our paper, we solve this problem and show that the lineage which has caused such devastation can be traced back to East Asia."
An international team of scientists gathered samples of the pathogen from around the world and sequenced the genomes.
They found four, main genetic lineages of the fungus — three of which are found around the world and a fourth found only in native frogs in Korea.
The genetic analysis showed that "the range of the disease expanded greatly between 50 and 120 years ago, coinciding with the rapid global expansion of intercontinental trade," said the report.
The findings offer "strong evidence for a ban on trade in amphibians from Asia due to the high risk associated with exporting previously unknown strains of chytrid out of this region," it added.
Another pathogen affecting salamanders in Europe — B. salamandrivorans, or BSal — also emerged from Asia and is spreading via the global trade in pet amphibians.
"Our research not only points to East Asia as ground zero for this deadly fungal pathogen, but suggests we have only uncovered the tip of the iceberg of chytrid diversity in Asia," said Imperial College London professor Matthew Fisher.
"Therefore, until the ongoing trade in infected amphibians is halted, we will continue to put our irreplaceable global amphibian biodiversity recklessly at risk."
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In an accompanying article in Science, Karen Lips of the University of Maryland's biology department concurred, saying the findings show that current efforts to control the deadly fungus have not been successful.
"The authors show that all Bd variants are present in the commercial trade of amphibians (including food, pets, and scientific specimens)," she wrote.
This demonstrates "contemporary intercontinental transmission and the failure of international biosecurity measures to control the spread of this pathogen."