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第25号公告板 - Summer 2006
VirologyClassical Swine Fever
DEWULF J, KOENEN F, RIBBENS S, HAEGEMAN A, LAEVENS H, KRUIF A
Evaluation of the epidemiological importance of classical swine fever infected, E2 sub-unit marker vaccinated animals with RT-nPCR positive blood samples.
Journal of Veterinary Medicine. B, 2005, Volume 52, N°9, 367-371
An E2 subunit marker vaccine for classical swine fever (CSF) was demonstrated to protect animals from clinical disease but not from infection. However, in spite of positive RT-nPCR results, the presence, in blood, of the virus as such, could not be demonstrated. In that case can vaccinated-infected animals spread CSF virus? In a first experiment serum of vaccinated-RT-nPCR-positive animals was inoculated to BVD-free and CSF-free pigs. All remained CSFV-negative by virus isolation and RT-nPCR, and showed no histopathological lesions of CSF. The second experiment consisted in housing fully susceptible pigs together with pigs vaccinated with E2 subunnit vaccine which had been in contact with non-vaccinated CSF-infected pigs for 16 days. None of the susceptible pigs showed clinical signs nor became CSFV-positive by virus isolation or RT-nPCR. A third experiment involved ten pregnant gilts: two unvaccinated CSFV-infected gilts were housed in indidual boxes, each located between two boxes containing two vaccinated gilts. All gilts were euthanized one week before term. All gilts were tested negative by virus isolation but 7/8 were positive by RT-nPCR and the virus was isolated in the offspring of three of them. These three experiments demonstrate that pigs vaccinated with an E2 subunit marker vaccine and resulting positive by RT-nPCR but, in any case, negative by virus isolation did not achieve horizontal spread of CSFV. On the other hand, vertical transmission of CSFV did occur, suggesting that the transplacental route requires lower amounts of virus than horizontal tramsmission does.
