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 conventional 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 were pregnant, were experimentally inoculated. They became viraemic for the first time 6 days post-inoculation (dpi). The contact gilts became viraemic between 18 and 21 days post inoculation. On the basis of virological findings and the martingale estimate of R0 (13.0) it was concluded that the two experimentally inoculated gilts infected all contact gilts, although random contacts between gilts were not possible. The prescence of CSF infection could 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 cases vertical virus transmission occurred and this resulted partially in abortion and/or mummification.