PROTECTION OF PIGS BY VACCINATION OF PREGNANT SOWS AGAINST EASTERN EQUINE ENCEPHALOMYELITIS VIRUS

Serum-virus neutralizing antibodies were detected in serum and colostr um of sows vaccinated during pregnancy with commercially available vac cines against eastern equine encephalomyelitis virus (EEEV), and antib odies were detected in serum from nearly all pigs from vaccinated sows following colostrum uptake. Serum-virus neutralizing antibody (SVN) t est titers were measured in colostrum and pigs at the next farrowing, and additional vaccination of sows prior to the third farrowing led to elevated SVN titers in serum, colostrum and all pigs. Six pigs from v accinated sows challenged at 8 to 9 days of age with 1 X 10(6) TCID50 EEEV did not develop the high temperatures or signs of central nervous system disease that 6 pigs from non-vaccinated sows developed. Virus was isolated from blood and oropharyngeal swabs from all pigs from non -vaccinated sows with blood virus titers as high as 9.3 X 10(4) TCID50 , while only low levels of virus were detected in blood and oropharyng eal swabs from pigs from vaccinated sows. Virus was also isolated from tonsils collected at necropsy from 3 pigs from non-vaccinated and 1 p ig from vaccinated sows. Vaccination of pregnant sows leads to develop ment of maternal antibodies that are transmitted via colostrum to pigs and are protective against clinical EEEV related disease after experi mental challenge with EEEV. In addition, vaccination prevents amplific ation of virus in infected pigs and could result in protection of anim als and farm labor in the environment of infected pigs.