eDNA-based crayfish plague monitoring is superior to conventional trap-based assessments in year-round detection probability
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The crayfish plague disease agent Aphanomyces astaci is a major threat to European crayfish populations, leading to mass extinctions when spores are transmitted into habitats of native species by infected invasive crayfish species. Current methods for detecting crayfish plague in carrier crayfish populations depend on time-consuming capture of individuals and screening via molecular methods. Highly sensitive environmental DNA (eDNA) methods are a promising tool for rapid and cost-efficient monitoring of pathogens in freshwater systems directly in water samples. For evaluating the usefulness of eDNA for A. astaci detection, the trap-based crayfish plague monitoring followed by qPCR screening of tissue samples was compared to an eDNA-based system to detect A. astaci- spores at a stream inhabited by an infected carrier crayfish population of Pacifastacus leniusculus. The presence of A. astaci was confirmed at all investigated sites with both sample types. Both methods showed comparable A. astaci prevalence, with the eDNA method being applicable across a longer annual time span, including winter, with greater reliability than the conventional method. Given the speed and reliability of the eDNA method for crayfish plague detection, this method might be the best choice for routine monitoring and evaluation of crayfish habitats to hinder the disease spread.
KeywordsAphanomyces astaci Environmental DNA Filtration Pacifastacus leniusculus Pathogen detection Seasonal variation
We would like to acknowledge the upper fisheries administrations of the State of Hessen for financial and logistical support, namely Dr. Christian Köhler and Patrick Heinz (regional authority Darmstadt), Guntram Ohm-Winter and Marlene Höfner (regional authority Gießen) and Christoph Laczny (regional authority Kassel). We are also thankful to Dr. Anne Schrimpf who provided technical support that greatly assisted the research in the initial stages. We thank Berardino Cocchiararo for his valuable assistance in qPCR data analysis and his helpful advices in laboratory practice during this project. We would like to thank Philippa Breyer, Silvia Mort-Farre and Julia Mann for their assistance in sampling and laboratory work and are thankful to Rainer Hennings for useful suggestions concerning crayfish trapping. We are also very grateful to the two unknown reviewers for their comments, which improved the manuscript.
This work was funded (Grant F7/2012) and fishing permits were granted by the State of Hessen, represented by the regional authorities Darmstadt, Gießen and Kassel. The contributions conducted by D. Strand and T. Vrålstad were funded by the Norwegian Research Council Project NRC-243907/TARGET.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All applicable international, national, and/or institutional guidelines for the care and use of animals were followed.
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