Biologists at the University of California have highlighted a troubling trend: more than 40 percent of amphibian species face extinction risk due to the contagious fungal pathogen chytridiomycosis. The study, published in Frontiers in Conservation Science, examines how this disease spreads and its impact on amphibian populations across Africa.
The culprit is the fungus Batrachochytrium dendrobatidis, commonly abbreviated as Bd. This microorganism is highly transmissible and attacks skin, a vital organ for amphibians, including salamanders, frogs, and toads. While tadpoles are less often fatally affected, adults can suffer serious outcomes. The infection can cause skin thickening and shedding, lethargy, weight loss, and ultimately cardiac arrest in affected individuals.
In pursuit of a clearer picture, the researchers reviewed scientific literature dating back to 1852 and extending to 2017 to assess records of visible chytrid infections in African amphibians. They complemented this historical review with molecular testing, performing PCR analyses for Bd on nearly 3,000 preserved museum specimens. Field work took place between 1908 and 2013 in Cameroon, Ethiopia, Kenya, Lesotho, Tanzania, and Uganda. Additionally, skin swabs were collected from 1,651 live amphibians in Burundi, Equatorial Guinea, Cameroon, and the Democratic Republic of Congo during 2011 to 2013.
Findings show that the earliest detection of Bd in an amphibian specimen traces back to Cameroon in 1933. Before the year 2000, Bd presence remained under 5 percent, but a rapid rise followed, reaching 17 percent and then 21 percent in the 2010s. In some nations, prevalence has surged to as high as 74 percent, signaling a steep and ongoing spread across the continent.
The researchers emphasize that since 2000 there has been a noticeable, though underappreciated, rise in Bd infections, elevating the risk to African amphibians, particularly in eastern, central, and western regions. The team proposes that climate-related stressors may increase susceptibility to Bd, suggesting that while eradicating the pathogen in the wild is not feasible, mitigating its effects on wildlife remains essential. The authors stress the need for monitoring, habitat protection, and strategies to bolster amphibian resilience as part of conservation efforts (Frontiers in Conservation Science).
Overall, the study underscores a growing conservation concern for amphibians in Africa, where climate variability, habitat loss, and disease intersect to threaten diverse species. By documenting historical presence and mapping recent shifts in Bd prevalence, researchers aim to inform regional conservation planning and inspire coordinated actions to safeguard vulnerable amphibian communities across the continent.