ON THE MOLECULAR EPIZOOTIOLOGY OF THE CLA SSICAL SWINE FEVER - IMPORTANCE OF ISOLATION OF THE FRIJTERS STRAIN IN THE DIAGNOSIS AND ERADICATION OF THE DISEASE - COMPILATORY COMMUNICATION

Recent advances of pestivirus research are reviewed in connection with the studies, performed at the Department of Virology of The National Veterinary Institute, Uppsala, Sweden. The results, which have been re ported in details in the publications of VILCEK and BELAK (1996) and V ILCEK et al. (1996) are shortly summarized in the present article. A p ig pestivirus isolate, the Frijters (F) strain, was characterized by u sing reverse transcription-PCR (RT-PCR), followed by studies of restri ction fragment length polymorphism (RFLP) and direct sequencing of the amplicons. Restriction endonuclease enzyme digestion of 5'NC genomic region of PCR products suggested that F strain belongs to the border d isease viruses (BDV). These findings were confirmed by nucleotide sequ encing of the amplified part of the 5'NC genomic region, which reveale d 94% and 95% nucleotide similarity between the F strain and the BDV p rototype strains Moredun cp and Moredun ncp, respectively. Natural pes tivirus infections in various animal species represent a practical pro blem of great epizootiological importance. The presence of BDV in swin e herds might be a confusing factor during the classical swine fever v irus (CSFV) eradication programmes. The present finding indicate that there is a high need for careful genomic characterization of pestiviru s isolates in order to obtain a safe identification of these agents in various animal species. The genetic variability of CSFV has been stud ied by comparative nucleotide sequence analysis of virus isolates and vaccine strains. The comparative sequence analysis of the E2 region re vealed two main phylogenetic groups of CSFV, indicating that the virus apparently evolved from two ancestor nodes. Group I consisted of old and recent American and Asian viruses, as well as old English isolates from the 1950s. Group II consisted of relatively recent isolates from Europe. All 11 vaccine strains tested were branched in group I, imply ing a common ancestor. Useful epidemiological conclusions can be drawn from the phylogenetic analysis of the CSFV genome.