In utero immunization of calves against colisepticemia.

A total of 21 bovine fetuses was inoculated in utero with Escherichia coli antigen to determine if nonserotype-specific resistance to colisepticemia could be induced. (Seven of these fetuses were inoculated through the intact flank of the dam.) After birth, the calves were deprived of colostrum and challenge exposed to a serologically distinct E coli which killed nonvaccinated controls. Of 21 calves vaccinated as fetuses, 10 survived challenge exposure, 8 died of colisepticemia, and 3 were stillborn. Premature birth precluded an adequate period of vaccination in 6 of the calves that died of colisepticemia. A relationship was not observed between E coli serum antibody and survival after challenge exposure. The results indicate that in utero vaccination with a single serotype of E coli can result in heterogenetic protection against neonatal colisepticemia. However, the occurrence of stillbirth and premature birth in calves vaccinated in utero indicates need for furthur research before field application of this technique.