Use of Brucella abortus vaccine strain RB51 in pregnant cows after calfhood vaccination with strain 19 in Argentina

One hundred and seven pregnant cows, which had been calfhood vaccinated wit h Brucella abortus strain 19 (S-19) were revaccinated with either S-19 or s train RB51 (S-RB51). All S-19-revaccinated animals seroconverted, while non e of the RB51-revaccinated animals seroconverted. Two out of 25 (8%) S-19-r evaccinated animals aborted, while none of the 57 RB51-revaccinated group a borted. Four of the S-19-revaccinated animals shed S-19 in the milk for at least 7 days, while only 1 cow shed S-RB51 for at least 3 days (but <7 days ) post-parturition. Revaccination of strain 19 calfhood-vaccinated, pregnan t cattle with S-RB51 appears to be a safe procedure with no diagnostically negative consequences. (C) 2000 Elsevier Science B.V. All rights reserved.