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Diseases of Aquatic Organisms

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DAO 72:77-85 (2006)  -  doi:10.3354/dao072077

A non-lethal technique for detecting the chytrid fungus Batrachochytrium dendrobatidis on tadpoles

Richard W. R. Retallick1,3,*, Verma Miera1, Kathryn L. Richards1,4, Kimberleigh J. Field2,5, James P. Collins1

1School of Life Sciences, Arizona State University, PO Box 874501, Tempe, Arizona 85287-4501, USA
2Arizona Game and Fish Department, 2221 W. Greenway Rd., Phoenix, Arizona 85023-4399, USA
3Present address: 1 Walter Street, South Yarra, Victoria 3141, Australia
4Present address: Yale University, School of Forestry & Environmental Studies, 370 Prospect St., New Haven, Connecticut 06511, USA
5Present address: U.S. Fish and Wildlife Service, 1340 Financial Blvd. #234, Reno, Nevada 89502, USA

ABSTRACT: Batrachochytrium dendrobatidis (Bd) infection on post-metamorphic frogs and salamanders is commonly diagnosed using polymerase chain reaction (PCR) of skin scrapings taken with mildly abrasive swabs. The technique is sensitive, non-lethal, and repeatable for live animals. Tadpoles are generally not sampled by swabbing but are usually killed and their mouthparts excised to test for the pathogen. We evaluated a technique for non-lethal Bd diagnosis using quantitative PCR (qPCR) on swabs scraped over the mouthparts of live tadpoles. The sensitivity of non-lethal (swabbing) and lethal (removal of mouthparts) sampling was assessed using 150 Bd-infected Rana subaquavocalis tadpoles. Swabbing was consistently less sensitive than lethal sampling, but still detected Bd. Experimental Bd prevalence was 41.1% when estimated by destructively sampling mouthparts and 4.7 to 36.6% (mean = 21.4%) when estimated with swabs. Detection rates from swabbing varied with investigator and time since infection. The likelihood of detecting Bd-infected tadpoles was similar regardless of size and developmental stage. Swabbing mouthparts of live tadpoles is a feasible and effective survey technique for Bd, but, because it is less sensitive, more tadpoles must be sampled to estimate prevalence at a confidence level comparable to destructive sampling.

KEY WORDS: Batrachochytrium dendrobatidis · Tadpole · Detection · PCR · Technique · Chytridiomycosis

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