Development of a TaqMan PCR assay with internal amplification control for the detection of African swine fever virus

A closed-tube polymerase chain reaction (PCR) was developed to allow the rapid detection of African swine fever virus (ASFV) DNA. This assay targets the VP72 gene of ASFV and uses the 5'-nuclease assay (TaqMan) system to detect PCR amplicons, avoiding tube opening and potential cross-contamination of post-PCR products. An artificial mimic was engineered with the TaqMan probe site replaced by a larger irrelevant DNA fragment allowing discrimination from ASFV by using two-colour TaqMan probe reporters. When added to the samples, successful amplification of this mimic demonstrated the absence of substances inhibitory to PCR, thereby validating negative results. Assay sensitivity was confirmed by obtaining positive signals with a representative selection of ASFV isolates. Many of the clinical and post-mortem features of ASF resemble those of classical swine fever (CSF) and porcine dermatitis and nephropathy syndrome (PDNS). Therefore, fast and reliable detection of ASFV is essential not only for the implementation of control measures to prevent the spread of ASF, but also in the differential diagnosis from CSF and PDNS. This assay should prove to be a valuable tool in the laboratory diagnosis of ASF and will complement existing molecular methods to provide rapid differential diagnosis in cases of suspected swine fever.