A survey of viral haemorrhagic septicaemia virus in cultured sea bass and its virulence on juveniles of sea bass, Dicentrarchus labrax (Actinopterygii: Perciformes: Moronidae) and gilthead sea bream, Sparus aurata (Sparidae)

Abstract

Background. Turkey is one of the major European seed producers of European sea bass, Dicentrarchus labrax (Linnaeus, 1758), and gilthead sea bream Sparus aurata Linnaeus, 1758.  Determination of susceptibility to viral haemorrhagic septicaemia (VHS), a notifiable disease in Europe, is crucial particularly for sea bass and sea bream seed production to develop control measures and to take necessary actions in case of a VHS outbreak.  We hypothesized that VHS virus does not replicate at 16°C and above—the temperature range typical for hatcheries in the Aegean region. Materials and methods. To assess the seasonal occurrence and virulence of viral haemorrhagic septicaemia virus genogroup Ie (VHSV-Ie), a virological survey was conducted in cultured sea bass in the Black Sea. Thirty-five sea bass were sampled monthly from a local marine farm, and examined virologically.  Triplicate groups of juvenile of sea bass (n = 30 per replicate or n = 40 per replicate) and gilthead sea bream (n = 20 per replicate) were challenged by immersion with VHSV-Ie at 12°C and 16°C to determine the occurrence of pathogen transfer and viral replication.  Results. VHSV-Ie, or any other viral pathogen able to infect BF-2 and CHSE-214 cells, did not occur in cultured sea bass of the Turkish Black Sea region. It was impossible to infect sea bass at 16°C but moderate levels of mortality occurred at 12°C. Sea bream, however, were susceptible to VHSV-Ie, presenting low levels of mortality (15%). Conclusion. VHSV-Ie poses no risk to the production of sea bass seed carried out at 16°C and above, but sea bass and sea bream should be monitored for VHSV-Ie where ambient water temperature is below 16°C since the risk of introduction is present.