Batrachochytrium dendrobatidis detected in Kihansi spray toads at a captive breeding facility (Kihansi, Tanzania)

Abstract

The chytrid fungus Batrachochytrium dendrobatidis (Bd) is the aetiological agent of amphibian chytridiomycosis, a disease associated with global amphibian population declines. In November 2012, mass mortalities of Kihansi spray toads Nectophrynoides asperginis were observed at the Kihansi captive breeding facility, located in the Udzungwa Mountains, Tanzania. Mortalities increased rapidly, and dead toads showed typical clinical signs of chytridiomycosis, including reddening of the skin that was especially evident on the toe pads. Treatment of toads with itraconazole rapidly reduced mortalities. Dead toads (n = 49) were collected and used to perform Bd-spedfic polymerase chain reaction and subsequent nucleotide sequencing. All toads collected at the facility were positive for Bd. The obtained Bd 5.8S rRNA gene and flanking internal transcribed spacer regions (ITS1 and ITS2) were not 100% identical to any other Bd sequences in GenBank, but closely resembled isolates from Ecuador, Japan, USA, Brazil, Korea, and South Africa. To our knowledge, this is the first study reporting molecular characteristics of Bd isolated from the Udzungwa Mountains. Strict biosecurity measures at the breeding facility and in Kihansi spray wetlands where toads have been reintroduced have been implemented. Further studies on Bd epidemiology in the Udzungwa Mountains are recommended in order to understand its origin, prevalence, and molecular characteristics in wild amphibian populations. This will be important for conservation of several endemic amphibian species in the Udzungwa Mountains, which are part of the Eastern Arc Mountains, a global biodiversity hotspot.