Non‐declining amphibians can be important reservoir hosts for amphibian chytrid fungus

• Published in: Animal conservation Vol. 21; no. 2; pp. 91 - 101
• Main Authors: Brannelly, L. A., Webb, R. J., Hunter, D. A., Clemann, N., Howard, K., Skerratt, L. F., Berger, L., Scheele, B. C.
• Format: Journal Article
• Language: English
• Published: London Wiley Subscription Services, Inc 01.04.2018
• Subjects: Adults; Age composition; Amphibians; Aquatic reptiles; Australia; Batrachochytrium dendrobatidis; Chytridiomycosis; Crinia signifera; Diseases; Dynamics; emerging infectious disease; Endangered & extinct species; Extinct species; Fungi; Hosts; Infections; Laboratories; Lethal effects; Population decline; Rare species; Reptiles & amphibians; reservoir host; Surveying; Survival; Sympatric populations; Threatened species; wildlife disease
• ISSN: 1367-9430; 1469-1795
• DOI: 10.1111/acv.12380

Amphibian chytridiomycosis, caused by infection with Batrachochytrium dendrobatidis (Bd), is the most devastating vertebrate disease on record. Reservoir hosts are likely to be important in the Bd‐amphibian system because many amphibian species can carry infections without experiencing mortality. However, while a variety of reservoirs have been proposed, few have been empirically demonstrated to act as competent reservoir hosts. In this study, we investigate whether the common eastern froglet, Crinia signifera, a non‐declining species that is widespread in eastern Australia, is a reservoir host for Bd infection. We conducted a long‐term, large‐scale field survey to investigate disease dynamics in C. signifera at sites where four sympatric, threatened anuran species have severely declined. We also monitored Bd‐infected C. signifera in the laboratory to determine susceptibility and survivorship. Finally, we assessed population age structure to investigate disease impact in the wild. We found that C. signifera is a competent reservoir host, maintaining high prevalence and infection intensities in the wild and in the laboratory, with no signs of sub‐lethal effects or clinical disease. In the wild, the modal age is 4 years with individuals living up to 6 years, indicating that adults can survive across multiple years despite high infection prevalence and intensity. The occurrence of C. signifera at sites with remnant populations of threatened species likely contributes to ongoing disease impact in declining species decades after the arrival of Bd. The presence of C. signifera at sites where threatened species have become extinct inhibits effective reintroductions, and we recommend avoiding sites with high reservoir host abundance when planning reintroductions. The wildlife disease chytridiomycosis is devastation amphibian populations worldwide.  In Australia, one common and abundant species of frog found in close proximity with endangered frog species have high infection in the wild yet experiences no symptoms of chytridiomycosis. We show that this common species is a competent reservoir host for a deadly disease and it appears to be an important player in the ecosystem for maintaining levels of disease within the habitat. Reservoir hosts like this species could threaten the population stability of declining species.