Withering syndrome of the small abalone, Haliotis diversicolor supertexta,is caused by Vibrio parahaemolyticus and associated with thermal induction

The susceptibility of the small abalone Haliotis diversicolor supertexta to Vibrio parahaemolyticus 880915 strain and its extracellular products (ECP) at different temperatures was investigated. The strain was previously isol ated from the haemolymph of the moribund small abalone with withering syndr ome during an outbreak of mass mortality among the cultured animals in Sept ember 1999 in I-Lan, Taiwan. The bacterium and its ECP were lethal to the s mall abalone. Onset of the withering syndrome in the moribund or dead anima ls could be observed at 4-7 d post-bacterial challenge. The same bacterial strain could be isolated from the haemolymph of the moribund animals with o r without the syndrome post-bacterial challenge. This syndrome could not be observed in the moribund or dead animals post-ECP challenge. The animals w ere more susceptible to the bacterium and ECP challenge at higher temperatu re (28 degreesC) indicating that the outbreak of the disease in warmer seas on is associated with thermal induction.