THE CRAYFISH PLAGUE IN THE CZECH REPUBLIC - REVIEW OF RECENT SUSPECT CASES AND A PILOT DETECTION STUDY

There are only very limited reports about the occurrence of the crayfish plague in Czechia. In recent years, mass mortalities of Astacus spp. with symptoms of possible crayfish plague were noticed in three streams in the country – two in Central Bohemia (1998-9) and one in Silesia (2004). Three dead individuals from the last outbreak were examined for the presence of the crayfish plague pathogen, Aphanomyces astaci, by observation of the presence of hyphae in their cuticle and by a PCR-based diagnostic method. In all three cases the detection was positive. Although causes of mass mortalities from two other localities lack such a direct confirmation, the indirect evidence supports the same conclusion. The main potential vector of A. astaci in Czechia is the American spiny-cheeck crayfish Orconectes limosus, widespread in large rivers of the western part of the country and in various isolated standing waters. Using the same molecular method, we investigated the presence of A. astaci in living O. limosus individuals from six localities (three running and three standing waters). The analysis indicated the presence of the pathogen in animals from five out of six investigated Orconectes populations. One of them is present in the stream where two European Astacus species had gone extinct in 1998-9. Our results suggest that the crayfish plague is still present in Czechia, and that populations of O. limosus represent a reservoir for the crayfish plague pathogen, which directly endangers populations of the native crayfish.