Detection of low-virulent classical swine fever virus in blood of experimentally infected animals: Comparison of different methods

The effectiveness of virus isolation, commercial antigen enzyme-linked immu nosorbent assay (ELISA), reverse transcriptase-polymerase chain reaction (R T-PCR), and flow cytometry in detection of a low-virulent classical swine f ever virus (CSFV) in blood in the early period of infection was evaluated. Domestic pigs at the age of 6-8 weeks and young wild boars were inoculated with a low-virulent field isolate of CSFV originating from a wild boar. Thi s virus induced serious clinical reaction in only one pig which was natural ly infected with Pasteurella. Nine of 13 infected domestic pigs showed vire mia. All infected weanling pigs were found viraemic by virus isolation on d ay 6 post infection (p.i.) but virus-free by RT-PCR. The flow cytometry was apparently not as sensitive as the virus isolation. Two young wild boars i nfected with the virus were viremic only for the first 2 days p.i. Virus is olation and RT-PCR were of similar sensitivity. Three different commercial antigen ELISAs used were not able to detect viral antigen in any animal.