Monitoring the prevalence and distribution of chytrid fungus (Batrachochytrium dendrobatidis) in the Kihansi Spray Toad (Nectophrynoides asperginis) population in the Kihansi Gorge spray wetlands, Tanzania

Résumé fourni par la source

Chytridiomycosis, caused by Batrachochytrium dendrobatidis (Bd), is a fungal disease only fatal to some amphibian species. Among the vulnerable species is the Nectophrynoides asperginis, endemic to the Kihansi Gorge spray wetlands in Tanzania’s Udzungwa Mountains. By 2009, chytridiomycosis had driven N. asperginis to extinction in the wild, though it survives in captivity. Reintroduction efforts have faced difficulties, underlining the importance of understanding Bd’s prevalence in the wild to guide re-introduction programs. We assessed Bd’s presence 20 years after its initial detection in Tanzania and determined whether it was responsible for the 98% mortality of 1000 captive-bred N. asperginis released in Feb 2022. In December 2022, time-constrained surveys were conducted across three spray wetlands covering N. asperginis habitats. Amphibians were skin-swabbed following a protocol developed by the University of California, resulting in two sets of 44 samples from seven species. These samples were analyzed for Bd presence using conventional and real-time quantitative polymerase chain reaction, followed by nucleotide sequencing of PCR products. Bd was detected in 32% of samples, affecting four species: Arthroleptides yakusini (14%), N. asperginis (9%), Ptychadena anchietae (7%) and Hyperolius substriatus (2%). Whereas N. asperginis was severely affected, the other species were healthy carriers. Bd-CAPE was confirmed as the cause of the mass deaths of the released toads. The continuing presence of Bd-CAPE in the spray wetlands remains a barrier to the successful re-introduction of N. asperginis, necessitating further experimentation to develop strategies for coexistence.

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