A reservoir species for the emerging Amphibian pathogen Batrachochytrium dendrobatidis thrives in a landscape decimated by disease

• Published in: PloS one Vol. 7; no. 3; p. e33567
• Main Authors: Reeder, Natalie M M, Pessier, Allan P, Vredenburg, Vance T
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 12.03.2012; Public Library of Science (PLoS)
• Subjects: Ambystoma tigrinum; Amphibians; Analysis of Variance; Animals; Anura - microbiology; Batrachochytrium dendrobatidis; Biology; California - epidemiology; Chorus; Chytridiomycosis; Chytridiomycota; Climate change; Disease Outbreaks - veterinary; Disease Reservoirs - microbiology; Disease Susceptibility - veterinary; Ecosystem; Extinct species; Frogs; Fungi; Histological Techniques - veterinary; Histology; Infection; Infections; Laboratories; Mortality; Mycoses - epidemiology; Mycoses - pathology; Mycoses - veterinary; Outbreaks; Pathogenesis; Pathogens; Prevalence; Protected areas; Pseudacris regilla; Rana catesbeiana; Rana muscosa; Reptiles & amphibians; Silurana; Skin; Species; Species Specificity; Spores, Fungal - isolation & purification; Sympatric populations; Tissues; Xenopus; Zoospores; California; San Francisco California
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0033567

Chytridiomycosis, a disease caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), is driving amphibian declines and extinctions in protected areas globally. The introduction of invasive reservoir species has been implicated in the spread of Bd but does not explain the appearance of the pathogen in remote protected areas. In the high elevation (>1500 m) Sierra Nevada of California, the native Pacific chorus frog, Pseudacris regilla, appears unaffected by chytridiomycosis while sympatric species experience catastrophic declines. We investigated whether P. regilla is a reservoir of Bd by comparing habitat occupancy before and after a major Bd outbreak and measuring infection in P. regilla in the field, monitoring susceptibility of P. regilla to Bd in the laboratory, examining tissues with histology to determine patterns of infection, and using an innovative soak technique to determine individual output of Bd zoospores in water. Pseudacris regilla persists at 100% of sites where a sympatric species has been extirpated from 72% in synchrony with a wave of Bd. In the laboratory, P. regilla carried loads of Bd as much as an order of magnitude higher than loads found lethal to sympatric species. Histology shows heavy Bd infection in patchy areas next to normal skin, a possible mechanism for tolerance. The soak technique was 77.8% effective at detecting Bd in water and showed an average output of 68 zoospores per minute per individual. The results of this study suggest P. regilla should act as a Bd reservoir and provide evidence of a tolerance mechanism in a reservoir species.