An experimental infection with classical swine fever virus in pregnant sows: Transmission of the virus, course of the disease, antibody response and effect on gestation

An experimental infection with classical swine fever (CSF) virus in 12 conv entional gilts, housed in a sow-box housing system, was conducted in order to evaluate horizontal transmission, clinical, virological and serological response, and the effect on gestation. Two of the 12 gilts, of which 10 wer e pregnant, were experimentally inoculated. They became viraemic for the fi rst time 6 days post-inoculation (dpi). The contact gilts became viraemic b etween 18 and 21 days post-inoculation. On the basis of virological finding s and the martingale estimate of R-0 (13.0) it was concluded that the two e xperimentally inoculated gilts infected all contact gilts, although random contacts between gilts were not possible. The presence of CSF infection cou ld be diagnosed earlier and during a longer period when the leucocyte count or polymerase chain reaction were used in comparison with virus isolation in whole blood (P < 0.05). The observed clinical symptoms were atypical and highly variable between the gilts, which hampered clinical diagnosis. The pregnant gilts became infected between day 43 and 67 of gestation. In all c ases vertical virus transmission occurred and this resulted partially in ab ortion and/or mummification.