Classical swine fever (CSF) marker vaccine - Trial II. Challenge study in pregnant sows

The efficacy of two marker vaccines against classical swine fever (CSF) was tested in a large scale laboratory trial in several National Swine Fever L aboratories (NSFL) of the EU member states. The vaccines were: BAYOVAC CSF Marker (Vaccine A) from Bayer, Leverkusen, Germany and PORCILIS PESTI (Vacc ine B) from Intervet, Boxmccr, The Netherlands. At the NSFL of Belgium, The Netherlands and Germany experiments were carried out to examine the abilit y of the vaccines to prevent transplacental transmission of CSF virus. In B elgium and The Netherlands pregnant sows were vaccinated once and challenge d with virulent CSF virus 14 days later, which was around day 60 of gestati on. At the NSFL in Germany sows were vaccinated twice, on days 25 and 46 of pregnancy and were challenged fourteen days after booster vaccination (day 60 of gestation). Apart from minor inflammatory reactions in some sows, no reactions post vac cination were noticed in either vaccine group. Sows vaccinated with Vaccine A were better protected against clinical CSF than sows vaccinated with Vac cine B. The antibody response after vaccination with Vaccine A was more pro nounced than after vaccination with Vaccine B. After single vaccination six out of eight sows vaccinated with Vaccine A and all eight sows vaccinated with Vaccine B had viraemic piglets. After double vaccination one out of fo ur litters from sows vaccinated with Vaccine A and four out of five litters from sows vaccinated with Vaccine B were found to be viraemic. However, bo th vaccines reduced the transmission probability significantly (Vaccine A: P = 0.004, Vaccine B: P = 0.024) after booster vaccination. However, Vaccin e A appeared in this regard more potent as the estimated probability of fet al infections was lower. Nevertheless the risk of virus spreading after vac cination via transplacental transmission is still present and has to be add ressed from an epidemiological point of view. (C) 2001 Elsevier Science B.V . All rights reserved.