Maistrenko M. Emerging of viral infections in carp (Cyprinus carpio) and rainbow trout (Oncorhynchus mykiss) species

This dissertation is dedicated to the diagnosis and study of some of the biological emerging highly contagious viral infections properties in carp (Cyprinus carpio), specifically cyprinid herpesvirus 3 (CyHV-3) and fish birnavirus – infectious pancreatic necrosis virus (IPNV) in rainbow trout (Oncorhynchus mykiss). Oligonucleotide primers specific for the CyHV3 thymidine kinase gene region were used to identify the virus by PCR. With the help of the PCR developed by us, the virus was detected in koi carp and aquarium fish of the Kyiv Zoo. The virus CyHV3 was first detected in labeo carp (Labeo bicolor) and bagfish (Heteropneustes fossilis). The nucleotide sequences of the three amplified fragments of segment A of the Ukrainian isolate IPNV "Carpathians" (150 bp for the NS gene and 175 and 480 bp for the N- and C-terminal regions of the VP2 gene, respectively) were analyzed. After analyzing the data, it was found that the most effective sites of RNA of IPNV virus for the selection of oligonucleotide primers and specific amplification are areas encoding the structural protein VP2 and non-structural protein NS. Studies have shown that selected oligonucleotide primers specific for the non-structural protein genes of the NS protein and the structural protein VP2 IPNV amplified the expected cDNA fragments. The size of the amplicons for IPN primers was 620 nucleotide pairs (bp), for WB - about 200 bp, and a fragment length of 175 bp. was characteristic of PrD primers. According to the results of our research, the Ukrainian isolate IPNV belongs to the strain Sp, first isolated in Denmark. Comparison of the nucleotide sequence of the isolate "Carpathians" with nucleotide sequences from the database of the National Center for Biotechnology Information (NCBI) showed that the amplified cDNA fragments are 95-99% identical to the gene sequences of NS and VP2 strain Sp. Using newly developed diagnostical methods based on PCR, it is now possible to reduce financial losses caused by diseases, significantly improve the epizootic situation and increase fish productivity in fisheries. According to the results of our experiments to study the effect of the virus on the activity of some enzymes, it is shown that the most informative is aspartate aminotransferase (AST). Given the simplicity of the analysis to determine its activity, this method can be an effective rapid method of detecting IPNV in trout farms.