Virulence of Vibrio parahaemolyticus isolated from cultured small abalone, Haliotis diversicolor supertexta, with withering syndrome

Outbreaks of mass mortality among cultured small abalone Haliotis diversicolor supertexta with withering syndrome occurred in May and September 1998 in Kao-Hsiung, Taiwan. Bacterial strains CH-1 and B4 were isolated from the haemolymph of the moribund small abalone using tryptic soy agar supplemented with 3% NaCl and/or thiosulphate citrate bile salt sucrose agar. These two strains were characterized and identified as Vibrio parahaemolyticus on the basis of various biochemical tests. The B4 strain and its extracellular products were virulent to small abalone with LD(50) values of 1.6 x 10(5) colony-forming units and 7.58 microg protein g-1 body weight, respectively.