A fungus that kills frogs and amphibians is spreading rapidly across Africa

A deadly fungus that feeds on the skin of frogs and other amphibians is spreading rapidly across Africa. Batrachochytrium dendrobatidis – Bd to be short – over the past two decades, the continent has experienced a dramatic increase, raising fears that it could wipe out amphibian populations in Africa, as it does in other parts of the world.

bd causes a disease called chytridiomycosis, which leads to heart failure in amphibians and has been blamed for the drastic population decline in America and Australia. “We are talking about hundreds of species that have been driven to extinction or are close to extinction due to a single pathogen,” says Vance Vredenburg of San Francisco State University in California.

Researchers believe bd originated in Asia and by the end of the 1900s had reached all continents except Antarctica. However, its impact on Africa remains relatively unexplored. Previous research suggests that it has been present on the continent since the 1930s, albeit in small quantities. Some studies hint at higher infection rates recently, but this may just be an artifact of researchers looking for bd more now than in the past.

To find out more, Vredenburg and his colleagues turned to museum collections of amphibians. Fungi and other parasites are often preserved with the animals they inhabit, allowing museum exhibits to be used to study the history of infectious disease.

The team took skin swabs from nearly 3,000 specimens collected in Africa over the past century. They also tested the skin of 1,651 live amphibians found in the wild and collected thousands of additional records from other studies of specimens collected between 1852 and 2017.

Combining all this information, they found that bd went unnoticed in Africa in the 1900s, consistently appearing in less than 5 percent of animals tested. But that all changed at the turn of the century, and in the early 2000s, the prevalence of the virus on the continent rose to about 20 percent.

It is not clear what caused this increase, but one possible explanation is that trade and the associated movement of people and goods bd into new areas — as it has already happened in other parts of the world,” says Vredenburg.

The team has collected “an impressive amount of new data” in addition to existing research, says Breda Zimkus of the Museum of Comparative Zoology at Harvard University in Massachusetts. She says that many of the regions that are seeing growth bd also experienced a decline in amphibian populations, which the researchers suggest is no coincidence.

For example, in Cameroon, where these groups showed bd With prevalence reaching nearly 40 percent in the 2010s, once common amphibians such as puddle frogs and long-toed frogs are rapidly declining.

The researchers also used the trends they found along with existing data on bdpreferred climate and hosts to predict where the fungus might go next. They showed that parts of West Africa that have not had chytrid mycosis reported so far may be particularly at risk.

Dina Olson of the USDA Forest Service says she is pleased to see this kind of risk assessment being applied to bd in Africa. “These are tools that managers can use to identify the most critical areas that conservation planning may need to… to prevent further disasters for vulnerable species.”

Vredenburg says he hopes the results will spur further research into Africa’s amphibians. According to him, these animals are “extremely little studied.” “Maybe we could do a lot [to help them] if only we had more information.”