Investigation of ornamental crayfish reveals new carrier species of the crayfish plague pathogen (Aphanomyces astaci)

Several North American crayfish species have so far been identified as carriers of the crayfish plague agent Aphanomyces astaci. The pathogen is responsible for the declines of thousands of European crayfish populations. Currently, one of the introduction pathways of North American crayfish species is the aquarium trade which may sometimes be followed by intentional release or unintentional escape of the pet species into the wild. We investigated 85 samples of North American and New Guinean species, available through the aquarium trade, for their possible infection with A. astaci. Crayfish plague infection was examined by applying real-time PCR. Besides morphological identification, we sequenced a fragment of the mitochondrial cytochrome c oxidase subunit I (COI) gene for crayfish species confirmation. Additionally, sequence analysis of nuclear DNA was conducted to identify the A. astaci lineage of moderate to highly infected crayfish. A total of 11 of the 85 analyzed crayfish individuals tested positive for an A. astaci infection, of which nine species are for the first time identified as carriers of A. astaci. No new genetic lineages of A. astaci were identified. The results confirm that, due to the positive carrier status of tested crayfish, the aquarium trade in Europe can facilitate the spread of A. astaci and can thus be a significant threat to the indigenous crayfish and the environment.