First detection of the crayfish plague pathogen Aphanomyces astaci in South America: a high potential risk to native crayfish

The crayfish plague pathogen, Aphanomyces astaci , is a fungal-like organism (Oomycetes), specialized in parasitizing freshwater crayfish species. Crayfish plague is a disease that has caused losses of indigenous crayfish populations, especially in Europe. The pathogen chronically infects North American endemic crayfish, such as Procambarus clarkii , which is considered an invasive species in several continents, including South America. Using molecular tools, quantitative PCR, and conventional PCR, we detected this pathogen in feral P. clarkii populations established in southeastern Brazil. This is an alarming result because in South America, especially in Brazil, there is considerable endemic crayfish species diversity, especially in the genus Parastacus . Possible contacts between P. clarkii and the endemic crayfish could be seen as a major threat to the native crayfish, mainly because of the possibility of A. astaci transmission. Furthermore, our results indicate preliminary evidence of possible A. astaci infection, agent level A2, in two sympatric native species, namely Parastacus defossus and Parastacus pilimanus . In this study, we provide the first overview concerning the presence of the crayfish plague pathogen, A. astaci , in South America.