Peracetic acid (PAA) treatment is an effective disinfectant against crayfish plague (Aphanomyces astaci) spores in aquaculture

We tested the efficacy of peracetic acid (PAA) and used 5 μm absolute filtration as an control on the disinfection or removal of crayfish plague (Aphanomyces astaci) spores in aquatic environment. The laboratory tests indicated that a concentration of 10 mg L− 1 PAA inactivated A. astaci spore germination and was chosen to be tested as a disinfectant in infection trials on noble crayfish (Astacus astacus). The same PAA concentration, 10 mg L− 1, was effective, when crayfish were exposed to PAA treated spore solution while crayfish exposed to untreated spore solution died. We observed that a minimum time lag of 4 h was sufficient for the breakdown of PAA under practical conditions since there was a 100% crayfish survival in test groups over two weeks when exposed to PAA treated water after a treatment time lag of more than 2 h. Furthermore, the absolute 5 μm filtration used as control also removed all infectious A. astaci spores and resulted in high survival rate in the group exposed to filtered spore suspension, similarly to the control group. The tested treatments could be used in freshwater crayfish aquaculture to prevent A. astaci infections, since the substitute freshwater requirement in crayfish aquaculture is low and thus allows effective disinfection. The methods could also be applied to other aquaculture activities, such as treatment of stockling transfer water to prevent the spread of disease agents, especially A. astaci spores.