Trending Science: Killer frog disease wiping out species worldwide

The warning signs appeared several decades ago when frogs, toads and salamanders started mysteriously disappearing in places like Australia, Costa Rica and Ecuador. By 1990, scientists began to observe that amphibians were dying around the world. The reason was a fungus that attacks the skin and eats these animals alive.

Wildlife disease most destructive in history

Fast forward to today. Documented evidence reveals the extent of the disease and how devastating it has been. Research published in the journal ‘Science’ shows that a disease known as chytrid fungus (chytridiomycosis) has caused remarkable population declines in at least 501 amphibian species – including 90 extinctions – during the past 50 years.

“Highly virulent wildlife disease including chytridiomycosis is contributing to the Earth’s sixth mass extinction” lead author Dr Ben Scheele of the Australian National University (ANU) in Canberra told the ‘BBC’. “We’ve lost some really amazing species.”

The main causes of this global pandemic that are helping to spread chytrid are globalisation and the wildlife trade. “Humans are moving plants and animals around the world at an increasingly rapid rate, introducing pathogens into new areas,” he said.

Chytrid fungus responsible for greatest biodiversity loss

According to the paper the 501 species represent 6.5 % of the known total more than double previous estimates. Of those 124 have declined by more than 90 % and may not recover. “The results are pretty astounding” added Dr Scheele in the British newspaper ‘The Guardian’. “We’ve known that chytrid is really bad for the better part of two decades but actually researching and quantifying those declines that’s what this study does.” On a positive note some species have shown signs of natural recovery. About 12 % of the 501 species have begun to recover in some locations.

Led by the ANU, over 40 amphibian and wildlife disease experts from around the world used published records, survey data and museum collections to find out how many amphibian species have been affected by chytrid. It has spread to over 60 countries, with Australia, Central America and South America particularly hard hit because of their many different frog species and ideal conditions for disease growth. In many species, chytrid is the key factor in amphibian deaths. However, in others it combines with habitat loss, climate change and predation from invasive species to push species towards extinction. The international team also reveals that many species are still at high risk of extinction from chytrid during the next 10-20 years as a result of ongoing declines.

What can be done to prevent chytrid or other pathogens like it from spreading? The researchers say improved biosecurity and wildlife trade regulations are urgently needed on a global scale. “Biosecurity is targeted at threats to human health and agriculture,” Dr Scheele concluded. “We need to broaden that undertaking to also consider the environment and things that threaten plants and animals.”