Outbreak of viral nervous necrosis in endangered fish species Epinephelus costae and E. Marginatus in northern Tunisian coasts

In this study, we report outbreak of viral nervous necrosis (VNN) in wild Epinephelus species, which are of an endangered fish group, in different Tunisian coastal areas in 2012. Seven fish of E. marginatus and E. costae caught at dead or moribund condition were investigated. Betanodavirus was detected in the brain and retinal tissues of all fish by RT-PCR and at high infective titers (106.0-8.8 TCID50/g) in five of seven fish. Sequence and phylogenic analyses of the viral genes revealed that the viruses belonged to RGNNV genotype and were closely related to some previously reported Mediterranean betanodavirus strains, suggesting virus exchanges among different fish populations in the Mediterranean Sea.