Protection by oral administration of brucella abortus strain 19 against an oral challenge exposure with a pathogenic strain of Brucella.

Twenty heifers were vaccinated orally with Brucella abortus strain 19. These heifers and 21 control heifers were challenge exposed in midgestation with strain 2308 by the oral route. Ten of 19 pregnant control heifers aborted and 14 were culture positive. Two additional heifers were seropositive at slaughter. Strain 2308 was recovered from 4 vaccinates at slaughter; none of the vaccinates aborted. Titers after oral vaccination persisted for less than 82 days.