A highly contagious and deadly fungal disease — believed to be the worst in recorded history — is spreading, threatening amphibians across a continent.
The deadly disease, known as chytridiomycosis, is caused by a microscopic fungus Batrachochytrium dendrobatidis (vol). Infection with this fungus has devastating effects on frogs, toads and other amphibians.
The disease causes the skin of these animals to shed, leading to other symptoms such as lethargy, weight loss and eventually heart failure. The disease is highly contagious and is transmitted by spores released by the fungus.
“The risks are significant,” said Vance Vredenburg, a professor in the Department of Biology at San Francisco State University news week. “In fact, this disease is the worst in recorded history. It has infected over 1,000 amphibian species and caused about 500 species to decline – dozens have gone extinct.”
Since the 1980s, the pathogen has spread and led to the mass extinction of amphibians worldwide. It’s still spreading today.
A study published in the journal Frontiers in Conservation Science has now found that the fungal pathogen is spreading across the African continent, a region scientists believe may have been spared the worst of the disease.
But Vredenburg and his colleagues noted that the disease is already well established in Africa and that its spread in the region appears to have been overlooked over the past two decades. The researchers found that it is likely to become more common and that amphibian declines and extinctions could be happening there already under the radar.
“Since 2000, Bd has spread across Africa and can threaten species across the continent,” Vredenburg said.
Africa is home to about 16 percent of known living amphibian species, but there have been no reported Bd epidemics – a disease event in an animal population that resembles an epidemic in humans – in Africa, although the disease is known to occur there.
Researchers said the lack of outbreak reports was likely due to lower Bd sampling efforts in Africa compared to other continents, rather than an actual lack of events.
The authors of limits The study came to its conclusions after analyzing thousands of museum specimens collected from various locations in Africa between 1908 and 2013. They also tested skin swabs from live amphibians caught between 2011 and 2013, as well as scientific records from the period 1852-2017.
They found a pattern of Bd formation in Africa that began largely around the turn of the century. From 1852 to 1999, they observed low Bd prevalence (about 3 percent overall) and small geographic distribution on the continent.
But after 2000, they documented a sharp increase in prevalence, rising to over 21 percent in the 2010s. In some countries for which more data was available, the increase was even higher – in Burundi, for example, to over 70 percent.
“We should be worried,” said Vredenburg. “This is the first fungal pathogen to cause this mortality rate in vertebrates. Although this is not The last of us Wait for humanity, we should try to learn from this to better understand what factors led to a fungal pathogen having such a profound effect on hosts.”