Preliminary investigations of disease-causing organisms in White-clawed crayfish Austropotamobius pallipes Complex from streams of Northern Italy

A total of 99 live and 3 dead white-clawed crayfish Austropotamobius pallipes were collected during summer-autumn 2003 from one creek in Emilia Romagna and four watercourses in Friuli Venezia Giulia in Northern Italy for experimental breeding and health status monitoring. Fifty-one animals coming from the Bidente river were maintained in tanks for breeding, reproduction and restocking, while another 30 specimens (27 living and 3 dead) were examined in the laboratory to evaluate their health status. Parasitological surveys were carried out on gills; mycological examinations on the exoskeleton, the walking legs and the cuticle of the abdomen; bacteriological examinations of inoculations from the haemolymph and histopathological analysis on full sections of cephalothoraxes and sections of the abdomen. In the gill-chambers, the gill filaments and the exoskeleton were observed for ectocommensal peritrich protozoans Epystilis sp. and Cothurnia sieboldii. In crayfish sampled from four creeks, Branchiobdella italica, B. astaci and B. parasita were isolated. Hyaline and dematiaceous hyphomycetes were frequently observed and Fusarium sp. and Saprolegnia sp. were isolated from cuticular lesions. Mortalities occurred in two tanks, after 2 and 4 weeks respectively, in the adult crayfish utilized for breeding, with approximately a 23.5% cumulative mortality rate. In both cases the crayfish were weak, anorexic and lethargic. Four and eight moribund samples respectively, coming from the two breeding tanks in which the mortalities occurred, underwent examination. In the first case, the mortalities were attributed to Thelohania-like organisms and, in the second case, the mortalities were associated with enteric bacteria. Bacterial lesions were observed in the dead crayfish found in the Chiarò and Bidente Rivers, and heavy damage of the gills in the presence of branchiobdellid cocoons was observed in the crayfish found dead in Orvenco creek.