A total of 16,900 historical and contemporary museum specimens, individuals living in the wild, and literature accounts of amphibians from Africa were examined by researchers to determine the frequency of the fungus Batrachochytrium dendrobatidis (Bd). Chytridiomycosis, which is contagious and fatal in amphibians and has wiped out hundreds of species worldwide, is brought on by Bd. The current study indicates that the reprieve from chytridiomycosis epidemics, which had only so far spared amphibian species in Africa, is now probably over.
The earliest Bd-positive specimen was from 1933, but until 2000, the prevalence in all of Africa remained below 5%. The prevalence increased further after that year, peaking at 17.2%. The authors come to the conclusion that Bd spread across Africa in 2000 and may be responsible for currently unrecognized diseases.
It’s not just in science fiction that massive fungal infections bring populations to the brink of extinction. Around the world, hundreds of species of amphibians have already been wiped out by chytridiomycosis, the worst vertebrate disease in recorded history. The extinction of 41% of amphibians is currently threatened, in large part because of this fungal disease. Only species found in Africa appeared to, at least thus far, have largely escaped the chytridiomycosis scourge.
The fungus Batrachochytrium dendrobatidis (Bd), the pathogen that causes chytridiomycosis, is now firmly established throughout Africa, according to a study published in Frontiers in Conservation Science, indicating that this respite was probably only temporary. Although it might have gone unnoticed up until now, it’s likely that the pathogen will spread further and cause epizootics across Africa in the near future.Bd is a chytridiomycid fungus, a basic group of fungi that produces asexual ‘swarm spores’, which use a whip-like flagellum to swim. Bd spores thrive in cool, moist habitats, and become embedded and multiply in the keratinized mouthparts and skin of salamanders, newts, and caecilians, but especially frogs and toads. Chytridiomycosis is exceptionally contagious, since it doesn’t need an animal vector to spread, while the spores can infect at least 1,000 distantly related species. The disease rarely kills tadpoles, but often kills adults, in which it causes the sloughing off of skin, lethargy, weight loss, and ultimately cardiac arrest.
The first known chytridiomycosis epizootics occurred in the late 1970s and early 1980s in western North America, in the late 1990s in Central America and Australia, and in the early 2000s in South America. Genetic analyses has shown that besides the strain Bd-GPL (‘Global Pandemic Lineage’), thought to be responsible for most chytridiomycosis epizootics, at least four other, possibly less virulent strains from South Korea, Switzerland, South America, and southern Africa exist today.