Passive immunity evaluation in piglets originating from sows vaccinated with China strain of classical swine fever virus

An experimental study was conducted to investigate the course of classical swine fever (CSF) infection in piglets originating from sows vaccinated with China strain vaccine. The experiment was carried out on 24 piglets (age 28, 35, 44 and 54 days) from vaccinated sows and on 11 non vaccinated piglets, originated from non CSF vaccinated sows. Two piglets from the each age group originating from vaccinated sows were challenged by intramuscular injection with CSF virus. Four piglets of the same age from vaccinated sows, and two piglets derived from unvaccinated sows were added to the challenged group to determine contact (horizontal) infection. After challenge, clinical examination and blood sampling from every animal was carried out on day 0, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27 and 29. Blood samples were examined for CSF virus specific antibodies by ELISA test, and for viral antigen i. e. viral RNA by RT-PCR technique. After death or sacrifice pathomorphological changes, presence and distribution of CSF virus antigen were detected in piglet tissue samples by ELISA test. On the basis of the obtained results it can be concluded that not all piglets born to vaccinated sows have maternal antibodies at a detectable level, and the issue of the efficiency of passive immunization needs to be evaluated in the future.