Batrachochytrium dendrobatidis infection dynamics in the Columbia spotted frog Rana luteiventris in north Idaho, USA

Abstract

The pathogenic chytrid fungus Batrachochytrium dendrobatidis (Bd) is contributing to amphibian declines worldwide. Temperature plays an important role in both pathogen growth and host immune function, but little is known about seasonal dynamics of Bd infection in north temperate regions. Our objective was to increase understanding of Bd disease ecology by investigating patterns of Bd infection of Columbia spotted frogs Rana luteiventris across seasons, age classes, and sexes in north Idaho, USA. We collected skin swabs from 223 R. luteiventris in spring, summer, and fall 2009 at 7 ponds in the Palouse region and quantified Bd zoospores for each sample using quantitative PCR. Across seasons, Bd prevalence of adults was higher in summer than in spring or fall, suggesting that individuals may be clearing low-level infections over the summer. Among age classes, all but one late stage tadpole (Gosner stage 43-45) tested negative for Bd. Conversely, 100% of metamorphs tested positive for Bd and had the highest Bd loads of all age classes, suggesting they may be the most vulnerable age class. Adult R. luteiventris had high infection prevalence (> 60%) in all seasons, indicating that Bd infection is maintained within populations and that adults likely serve as disease reservoirs across seasons. Among adults, we also found weak evidence for females having higher infection prevalence than males. Further laboratory and field studies are needed to determine whether there are individual and population impacts from Bd on R. luteiventris and other amphibians in north Idaho. KEY WORDS:Amphibian declines · Batrachochytrium dendrobatidis · Chytrid · Idaho · Rana luteiventris Resale or republication not permitted without written consent of the publisherContribution to DAO Special 4 'Chytridiomycosis: an emerging disease'

Elevation, Temperature, and Aquatic Connectivity All Influence the Infection Dynamics of the Amphibian Chytrid Fungus in Adult Frogs

“…We also demonstrated that the dynamics of Bd infections on L. rheocola were influenced by temperature and season, effects that have been reported in previous studies on several species in Australia and elsewhere [15,18-20,35-37]. Prevalence of Bd in adult frogs was higher in cooler than in warmer months, and was higher at higher elevations, as has been reported elsewhere [18,38,39].…”

Distribution of the disease pathogen Batrachochytrium dendrobatidis in non‐epidemic amphibian communities of western Canada

“…Previous research has suggested higher susceptibility (greater mortality rates) to Bd in western toads A. boreas (Blaustein et al ) and wood frogs L. sylvaticus (Searle et al ), and lower susceptibility in chorus tree frogs P. regilla (Reeder et al ). Prevalence of Bd observed in Idaho populations of the Columbia spotted frog R. luteiventris was high (67.6%) in adults and low in tadpoles (4.8%) (Russell et al ). We found similar, although less extreme results of 46% (90% CI: 30.5–66.5%) in adults, 96% in juveniles (90% CI: 77.6–99.9%), and 10% (90% CI: 0.8–34.1%) in larvae.…”

Ecological functions of zoosporic hyperparasites

“…Thus, more zoospores would be available to spread chytridiomycosis through the populations of amphibians. In adult frogs B. dendrobatidis prevalence is highest during late summer and winter, while infection takes place from late spring to early summer (Russell et al, 2010; Sapsford et al, 2013). This coincides with the breakdown of the chytrid epidemics.…”