Evaluation of a real-time RT-PCR assay using minor groove binding probe for specific detection of Chinese wild-type classical swine fever virus.

A one-step real-time RT-PCR assay using a minor groove binding probe was developed for the specific detection of Chinese wild-type classical swine fever virus (CSFV). The assay detected wild-type CSFV strains representing different genotypes, but did not amplify viral RNA from the Hog Cholera Lipinized Virus (HCLV) vaccine-strain and other porcine viruses. The assay had a detection limit of 10 copies/reaction or 3.0 median tissue culture infective dose/reaction. In comparison to the sequencing nested RT-PCR assay, the sensitivity and specificity of the assay were 98.3% and 94.3%, respectively, when testing 515 veterinary samples. Wild-type CSFV RNA was detected in nasal swabs 2-4 days before detection in serum samples from pigs exposed to infection by contact, and 2-4 days prior to the onset of clinical disease. HCLV RNA remained undetectable in nasal swabs and serum samples from vaccinated pigs. In conclusion, the novel assay described in this study provides a rapid and sensitive method for differentiating between wild-type and the HCLV-strain of CSFV. It could be used for monitoring in CSF outbreak areas or as a screening method for CSFV eradication strategies.