Temporal variation in the prevalence of the crayfish plague pathogen, Aphanomyces astaci , in three Czech spiny-cheek crayfish populations

Abstract

North American crayfish species are natural hosts of the crayfish plague pathogenAphanomyces astaci. The spiny-cheek crayfish Orconectes limosus, widespread in Central Europe, is the main reservoir of A. astaci in Czech Republic. We tested if there are temporal changes in the preva-lence of infected individuals (i.e., the proportion of individuals in which the pathogen is detected) in spiny-cheek crayfish populations. Crayfish from three populations shown previously to be infected to different extents (high, intermediate and low), were repeatedly sampled in different years (2004−2010) and seasons. The presence ofA. astaciin the soft abdom-inal crayfish cuticle was tested by specific amplification of the pathogen DNA. There was no substantial temporal variation in pathogen prevalence in the highly and very lowly infected populations. However, a significant long-term as well as seasonal decrease was found in the intermediately infected population. This decline could be related to a decrease in popu-lation density over the studied years, and to crayfish seasonal moulting, respectively. A reliable estimate of pathogen prevalence in American cray-fish populations thus requires repeated monitoring over years, preferably during the same season before the main period of crayfish moulting.