RESUMEN
The quasispecies nature of three animal pathogenic RNA viruses of field origin was examined by testing variants of classical swine fever virus (CSFV) originating from geographically different areas, feline coronavirus (FCoV) detected from the same animal by successive sampling, and rabbit haemorrhagic disease virus (RHDV) originating from successive outbreaks in the same geographic area. Clinical samples were investigated using reverse transcriptase polymerase chain reaction (RT-PCR) and ensuing single strand conformational polymorphism (SSCP) assay. By the combination of these methods even subtle differences could be detected among the amplified fragments of the same virus species of different origin. FCoV proved to comprise the most and CSFV the less heterogeneous virus quasispecies. The results show that the combination of RT-PCR and SSCP provides novel and highly sensitive means for the characterisation of RNA viruses, with special regard to genome composition, evolution, features of pathogenicity and molecular epizootiology.