RESUMO
The origin and evolution of the classical swine fever (CSF) epizootic that occurred in Cuba from 1993 to 1997 has been investigated by the analysis of E2 gene sequences from 15 representative viral isolates as well as the vaccine and the challenge strains used in this country. In the phylogenetic tree derived from these sequences, the Cuban isolates were located in a defined cluster within the previously reported genomic subgroup 1.2. This cluster was related, although distinguishable, from the live vaccine used in Cuba since 1965. Two further groups were identified. One of them included the early viruses isolated in the western part of Cuba until 1996 and the strain Margarita, used for vaccine potency tests since 1965. These results are consistent with the strain Margarita being the origin of the western outbreaks. The viruses isolated from 1996 in eastern Cuba defined a related, but independent group. The level of sequence variation observed in this group does not exclude an independent origin for the eastern isolates.
Assuntos
Vírus da Febre Suína Clássica/genética , Peste Suína Clássica/epidemiologia , Proteínas do Envelope Viral/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Peste Suína Clássica/fisiopatologia , Peste Suína Clássica/virologia , Vírus da Febre Suína Clássica/classificação , Vírus da Febre Suína Clássica/isolamento & purificação , Cuba/epidemiologia , DNA Viral/química , DNA Viral/genética , Epidemiologia Molecular , Dados de Sequência Molecular , Filogenia , Suínos , Proteínas do Envelope Viral/químicaRESUMO
A simple reverse transcriptase-polymerase chain reaction (RT-PCR) assay has been developed for the specific amplification of DNA after reverse transcription of RNA from the classical swine fever virus (CSFV). A pair of oligonucleotides was selected from an area of high homology in the genome of CSFV strains, but which differed from the corresponding sequences in the genome of bovine viral diarrhea virus (BVDV) strains. Using these primers (CSFV1-CSFV2), a CSFV specific DNA band of 174 bp was amplified from the CSFV RNA extracted from four reference strains and 14 field isolates, as well as from 25 organ extracts and eight buffy coats and serum samples of experimentally infected animals. No amplification was observed with the RNA from four BVDV reference and vaccine strains and seven field isolates. This RT-PCR assay made it possible, in a one-step reaction, to detect CSFV rapidly, sensitively and specifically in cell culture supernatants and in clinical specimens.