POLYMERASE CHAIN REACTION FOR IDENTIFICATION OF CYPRINID HERPESVIRUSES IN UKRAINE

The aim of the research was to investigate diseased fish species Labeo (Labeo bicolor) and Sack-gill Catfish (Heteropneustes fossilis) by testing several diagnostic systems targeting fish herpesviruses in purpose to determine the etiology of the outbreak infection in aquarium fishes at the Kуiv Zoo during summer 2017. During a fish health inspection of aquariums in Kyiv Zoo, an Cyprinid herpesvirus 3 − CyHV-3 was detected in Labeo and Sack-gill Catfish. Preliminary examination of infected fish revealed a range of lesions particularly in internal organs and tissues. The gills of diseased fish were characterized by hyperaemia and necrosis. The infringement of liver color and structure, kidney swelling and gallbladder necrosis were observed in both fish species. The virus did not grow in fish cell lines of RTG-2, FHM and EPC, that was evident by absence of any morphological changes in appropriate cell lines. Also initially fish were tested for parasitic and bacterial infections and they were determined to be non-infected. Our results demonstrated that specific oligonucleotide primers for thymidine kinase gene of CyHV-3 were successfully amplified the specific DNA fragments. The length of polymerase chain reaction product, as expected, was 264 nucleotide pairs. The amplified specific fragments were identical to the area of thymidine kinase gene CyHV-3, as was shown by sequence analysis. The identity of nucleotide sequences composed 97‒99%. The same positive results were obtained using primers that recommended by the International Epizootic Bureau, fragments in size of 409 and 292 were also obtained. In our opinion, CyHV-3 was brought to Ukraine by import of aquarium fish avoiding sanitary control of transboundary transportation. Therefore, the uncontrolled import of aquarium and cultured fish species is a serious problem because imported fish could be as a source of highly pathogenic infections for industrial aquaculture