PCR as a diagnostic tool for the diagnosis and epizootological investigation of swine fever

The economical losses and the difficulties of prevention and control of swi ne fever demand the most sensitive, specific and the quickest tools for its diagnosis, such as the reverse transcription-polimerase chain reaction (RT -PCR). However, this method alone does not inform about "polymorphism", i.e . the genetic heterogeneity of the amplified RT-PCR product. This can be ex amined with the single-strand conformational polymorphism (SSCP) method whe re the double-strand RT-PCR product is run on a polyacrylamide gel after de naturation. This method enables conclusions to be drawn about the "wild" or "mutant" nature of the virus that is represented by the RT-PCR product and the number and complexity of subpopulations in the sample. These methods w ere used to examine 57 deep frozen samples from previous outbreaks categori sed into five groups on the basis of pathology. Directed to the E2 region o f the viral genome, RT-PCR quickly and reliably showed evidence of the viru s from separated lymphocytes and various organs (most sensitively from the spleen and from tonsils) even after prolonged exposure of the sample to amb ient room temperature. Specificity and sensitivity of the RT-PCR was furthe r enhanced by the use of nested primers and a restriction endonuclease (Hae III). It was shown with SSCP that the RT-PCR products did have different ru nning patterns thus they were assumed to have derived from different subpop ulations of the virus. The authors conclude that these techniques can prove useful tools in the prevention and control of infectious diseases.