Evaluation of Single Step TaqMan Real-time PCR Assay Lateral to Conventional RT-PCR and Antigen-Capture ELISA for Pre-Clinical Detection of Classical swine fever virus

Classical swine fever (CSF) is a highly contagious and devastating viral disease, causing serious losses in the pig industry worldwide. Rapid detection and identification of the causative agent is a crucial step in controlling CSF infection in pig population. In the present study, a fluorogenic-probe hydrolysis (TaqMan)-reverse transcriptase real time PCR assay (RT-qPCR)was evaluated parallel to conventional RT-PCR and antigen capture ELISA to detect Classical swine fever virus (CSFV) in the pre-clinical phase of the disease. In addition, hematological analysis was performed at different clinical phases in order to diagnose CSF pre-clinically. Thrombocytopenia and leucopenia were early clinical clues recorded in CSFV infected pigs. Single step RT-qPCR confirmed the presence of CSFV nucleic acid in blood, nasal swabs, ocular swabs as well as in tonsillar scrapings in the pre-clinical phase. CSFV nucleic acid was detected with maximum positivity in blood and tonsillar scrapings (70-73%) using RT-qPCR as compared to 60% and 33.33-40% positivity in conventional RT-PCR and Ag-ELISA, respectively. Thus, TaqMan based RT-qPCR assay can be used as an efficient assay for rapid CSFV detection at pre-clinical phase of the disease to contain the disease from in-contact infected pigs to susceptible population.