Several herpes-like virus infections have been reported since 1991 among different bivalve species around the world (Nicolas et al., 1992; Comps and Cochennec, 1993; Renault et al., 1994; Hine and Thome, 1997; Hine 1997). To date, detection of these infections has been strongly correlated with severe losses of oyster larvae and spat. The virus infections are currently diagnosed by laborious histologicai and transmission electron microscopical examinations. These techniques, however, facilitate neither rapid diagnosis nor the ability to analyse large sample numbers.