Experimental herpes-like viral infections in marine bivalves: demonstration of interspecies transmission.

Since 1972, herpes-like virus infections have been reported in several marine bivalve species around the world. Viral detection was often associated with high mortality rates in larvae and spat. To determine whether a single virus is able to infect different bivalve host species, we carried out experimental transmission assays. As a first step, 8 assays were performed to infect axenic Crassostrea gigas larvae with virus from infected C. gigas larvae using a previously described protocol. The protocol appeared reliable and PCR was confirmed as a powerful technique for detecting viral DNA in experimentally infected oysters. The defined protocol was then applied to infect different bivalve species. Interspecies viral transmission was demonstrated under laboratory conditions. The same phenomenon may occur in private hatcheries and may be promoted by intensive rearing conditions. This hypothesis is reinforced by reports of concomitant mortalities in the larvae of several bivalve species and by the first molecular analysis of infected larval samples.