title: A non-lethal technique for detecting the chytrid fungus Batrachochytrium dendrobatidis on tadpoles.
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.
authors.affiliation: School of Life Sciences, Arizona State University, PO Box 874501, Tempe, Arizona 85287-4501, USA. richard.retallick@graduates.jcu.edu.au
authors.forename: Richard W R
authors.initials: RW
authors.lastname: Retallick
authors.forename: Verma
authors.initials: V
authors.lastname: Miera
authors.forename: Kathryn L
authors.initials: KL
authors.lastname: Richards
authors.forename: Kimberleigh J
authors.initials: KJ
authors.lastname: Field
authors.forename: James P
authors.initials: JP
authors.lastname: Collins
mesh_terms: D000818:Animals; D008411:Chytridiomycota / Q000235:genetics / Q000302:isolation & purification*; D007814:Larva / Q000254:growth & development / Q000382:microbiology; D009181:Mycoses / Q000175:diagnosis / Q000453:epidemiology / Q000662:veterinary*; D016133:Polymerase Chain Reaction / Q000379:methods / Q000662:veterinary*; D015995:Prevalence; D011898:Ranidae / Q000254:growth & development / Q000382:microbiology*; D015203:Reproducibility of Results; D016019:Survival Analysis; D013997:Time Factors