Detection and phylogeny of Lymphocystivirus in sea bream Sparus aurata based on the DNA polymerase gene and major capsid protein sequences

Lymphocystis disease virus (LCDV) is the causative agent of a condition affecting marine and freshwater fish worldwide. In this study, PCR primers based on the DNA polymerase gene sequence were employed for the detection of LCDV in gilthead sea bream Sparus aurata and for monitoring the course of the disease from onset to full clinical recovery. In spontaneously infected fish, viral DNA was detected in different organs, including skin, caudal fin, eyeball, brain, liver and kidney, and a correlation was found between PCR intensity and the persistence of the virus in organs of recovered fish with no residual clinical symptoms. In experimentally infected fish, PCR detection was achieved almost two weeks before appearance of external signs. LCDV remained detectable in skin, caudal fin and eyeball for up to four weeks after external signs of infection had cleared. A phylogenetic analysis based on the major capsid protein (MCP) gene sequence revealed that LCDV from sea bream cultured in Eilat, Israel, clusters within a genotype that includes two sub-clusters: one consisting of Japanese flounder isolates, the second of three isolates from three distinct host species belonging to different perciform families: sea bass Lateolabrax sp. (Lateolabracidae), sea bream S. aurata (Sparidae) and cobia Rachycentron canadum (Rachycentridae).