Isolation of Birnavirus from Japanese Pearl Oyster <i>Pinctada fucata</i>

Abstract

Since 1994, mass mortality of the Japanese pearl oyster Pinctada fucata has widely occurred in the southwestern part of Japan. The cause of mass mortality was investigat ed in terms of change of current, decrease in feed plankton, increase in seawater temperature, genetic fac tors, and water pollution. However, the cause of mortality has not been identified. Virus infection is thought to be one of the causes because it has been reported in the past that herpes virus-like particles1) and birnaviruses2) were found in several bivalves. Pathogenicity of birnavirus against hard clam Meretrix lusoria has been reported.3) The authors recently isolated the birnaviruses from Agemaki (jack knife clam) Sinonovacura consticta which originated in Ariake Bay, Saga Prefecture, Japan, as well as in an area on the Korean coast.4) The strain AGJ-90 that was isolated from the Ariake Bay samples showed patho genicity against Agemaki when the shells were exposed to physiological stress.4) The birnavirus genome was detected in high ratios by PCR, suggesting that the birnavirus is widely distributed in Agemaki.4) Therefore, we investigat ed the existence of viruses in Japanese pearl oyster. In this report, we describe the isolation and detection of birnavi rus from Javanese vearl oyster.