Isolation of viral haemorrhagic septicemiae virus in fish in the black sea region and determination of its pathogenicity

Viral haemorrhagic septicemiae (VHS) is an important viral disease which is commonly seen in fishes around the world. The aim of this thesis was to isolate viral haemorrhagic septicemiae virus (VHSV) from fish living in the Black Sea region and to determine pathogenicity of the isolates. For this purpose, samples were collected from 3378 fish from 12 species in the Black Sea coast and 2589 rainbow trouts from 62 aquaculture farms in this region. Presence of VHSV was determined by using reverse transcription-polymerase chain reaction (RT-PCR) from the RNA samples isolated from fish tissues. Later, the virus isolation from cell culture was performed from the VHSV detected samples by RT-PCR. Additionally, genomic identification and pathogenicity of the viruses were studied. RNA of VHSV was detected from five turbots only. In the pathogenicity tests, four of the virus isolates were found very pathogenic on turbot. On the other hand, one of the isolates was found not pathogenic. All the isolates were seen not to be pathogenic on trouts. According to the DNA sequence analysis, all the isolates were recorded to belong to genogroup I. In conclusion, VHS was found to be endemic in Black sea turbots. We suggest that there may be a relation between VHS and reduce in the turbot stocks in the Black sea in recent years. It is therefore required to conduct detailed studies on VHSV in order to have a better understanding of the epidemiology of the disease.Key Words: Viral Haemorrhagic Septicemiae (VHS), virus isolation, survey, DNA sequencing, mortality.