Genetic analysis of classical swine fever virus isolates from a small geographic area

Twenty-eight field CSFV samples were isolated from outbreaks of CSF which have occurred in three small geographic areas in Slovakia in the period of December 1993-November 1994. All the organ homogenates were positive by virus isolation and RT-PCR assay using general pestivirus 324/326 primers selected from 5'-noncoding (5'-NC) genomic region. Specific discrimination of CSFV was confirmed by the cleavage of amplicons using Bgl1 and Ava 1. Four viral isolates (A, B, C, E) were selected for a comparative sequencing study. Sequencing of amplicons in the 5'-NC, gp55 (E2), p54 (NS2) and NS5B genomic regions revealed that A, B isolates (originated from SR geographic area) were the same but different from identical C (NR geographic area) and E (ER geographic area) isolates. Results of molecular-genetic study were very well supported with epizootological data. All CSFV isolates from Slovakia phylogenetically fell into the group of recent European isolates clearly separated from old European and American strains.