Latent crayfish plague (Aphanomyces astaci) infection in a robust wild noble crayfish (Astacus astacus) population

Apparently healthy wild noble crayfish (Astacus astacus) sampled from Lake Mikitänjärvi, Kainuu, Finland in 2009 and 2010 were discovered to be PCR-positive for Aphanomyces astaci. Detection prevalence was lower in 2009 than in 2010. Despite the detected sublethal infection, the Lake Mikitänjärvi population has been productive and is being under commercial exploitation. Even though it has been suggested frequently that noble crayfish might harbor subclinical crayfish plague infections, this is the first confirmed report, based on molecular evidence, of healthy A. astacus carrying A. astaci.

► A novel finding of noble crayfish as latent carrier of crayfish plague.
► The carrier population is still strong and commercially exploited.
► The observation sheds light to previously discussed chronic crayfish plague theories.