Pathogenicity of a Birnavirus to Hard Clam(Meretrix lusoria) and Effect of Temperature Stress on Its Virulence.

Abstract

A birnavirus, CV-TS-1 strain isolated from cultured hard clam (Meretrix lusoria) was inoculated to the hard clam by means of intrapalleal cavity injection or water borne method at 25 degree C. Cumulative mortalities of clams injected with the virus at the concentrations of 10-4.7, 10-3.7 and 10-2.7TCID-50/clam were 37.5%, 32.5% and 25%, and those of clams immersed to virus solutions of 10-6.0, 10-5.0 and TCID-50/ml were 30%, 25% and 15%, respectively. Temperature stress (increase from 25 degree C to 33 degree C or decrease from 25 degree C to 15 degree C) was given to clams before and after virus challenge by exposure to a virus solution of 10-5.0TCID-50 ml. Mortality increased markedly when temperature was increased after virus infection, though either the decrease in temperature after virus challenge or increase or decrease in temperature before the challenge did not affect the mortality.