Sammendrag
The oomycete Aphanomyces astaci is a specialized parasite on freshwater crayfish of North American origin, but also the causative agent for crayfish plague. A. astaci is ranked among the world’s top 100 invasive alien species, as it has caused (and still causes) large economical and ecological damage since its introduction into Europe, destroying indigenous European freshwater crayfish populations. Recently developed polymerase chain reaction (PCR) and real-time PCR assays for the specific detection of A. astaci in crayfish tissues have drastically improved crayfish plague diagnostics compared to earlier methods. However, little is known about the presence and dynamic of A. astaci spores in infected water systems. Here, we present an approach for detecting and quantifying A. astaci directly from water samples using a species specific TaqMan® MGB real-time PCR assay, thus providing new tools for further research, and for surveillance of crayfish plague in aquatic environments. Samples of a 10-fold dilution series from ~10000 to ~1 spore of A. astaci were repeatedly tested, demonstrating reliable detection down to one spore. Further, to simulate practical samples from natural water bodies, water samples from lakes with different water quality were spiked with spores. The results demonstrated that co-extracted impurities inhibit detection, but the use of bovine serum albumin (BSA) or the TaqMan® Environmental Master Mix largely removes this problem. Finally, we demonstrate the practical performance of the approach on samples from aquatic environments hosting infected North American signal crayfish (Pacifastacus leniusculus).
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