Bacteriological investigation on allochthonous crayfish in Northern Italy.

In our 1999 investigations concerning the presence of Aphanomyces astaci on allochthonous freshwater crayfish living in Northern Italy, 72 red swamp crayfish (Procambarus clarkii) were captured in canals of the Province of Bologna (July) and 15 signal crayfish (Pacifastacus leniusculus) in the Auenbachl creek in the Province of Bolzano (September). In both species there was a high mortality rate following transfer to the laboratory (82% in P. clarkii and 53% in P. leniusculus). All the moribund or dead crayfish were submitted for necropsy and microbiological, parasitological, mycological and histopathological examinations. From the red swamp crayfish, Citrobacter freundii and Aeromonas sobria were constantly isolated. Aeromonas hydrophila was found in all the signal crayfish examined and Citrobacter youngae as well as Fusarium spp. was present in only one. The histopathological lesions are described.