Prenatal Immunization and Protection of the Newborn: Ovine and Bovine Fetuses Vaccinated with Escherichia coli Antigen by the Oral Route and Exposed to Challenge Inoculum at Birth

SUMMARY Ovine fetuses (6 to 51 days to term) and bovine fetuses (9 to 49 days to term) were vaccinated with Escherichia coli antigen deposited in fetal fluids, presumably amniotic fluid. The vaccinal antigens were E. coli serotypes O78:K80:NM for the ovine fetuses and O26:K60:H11 for the bovine fetuses. The prenatal vaccination seemed to protect newborn lambs and calves exposed to oral challenge inoculum of E. coli capable of causing death of nonvaccinated neonates. Of 5 single lambs vaccinated in utero, all survived the challenge exposure. In each of 5 sets of twin lambs, 1 twin survived challenge exposure and 1 died (only 1 of the twins was vaccinated in utero). Of 5 calves vaccinated in utero, 3 were healthy at birth and these 3 survived challenge exposure. Humoral E. coli agglutinin was present in some, but not all, of the prenatally immunized lambs and calves at birth. Protection against challenge was independent of humoral agglutinin detectable by macro-methods.