Abstract
Brucella abortus S19 and RB51 are the most used vaccines to control bovine brucellosis worldwide; therefore, this study aimed to perform a systematic review on the effectiveness of these two vaccine strains (field trials to evaluate bovine brucellosis vaccines efficacy). The literature review was conducted on April 03rd, 2021 on five databases (CABI, Cochrane, PubMed, Scielo, Scopus and Web of Science) and included papers published between 1976 and 2014. The search strategy recovered a total of 6027 papers, which after selection based on title, abstract, full-text and considering the eligibility criteria ended up with 17 papers and 33 trials included. The strain most used in the trials was S19 (25/33, 75.75%), at the dose of 109 colony forming units (CFU) (18/25, 72%), by subcutaneous route (21/25, 84%), in a single dose (20/25, 80%), and in adult animals (23/25, 92%). RB51 was used in 8 (24.24%) trials, %), at the dose of 109 colony forming units (CFU)(5/8, 62.5%), mainly by subcutaneous route (8/8, 100%), in a single dose (4/8, 50%) and animals younger than 12 months (6/8, 75%). The higher field challenge (non-experimental) observed was 39% and the lower, 0.64% (mean 13.36% ± 12.89%). The incidence of brucellosis and/or abortion were the outcomes assessed in 12 (36.36%) trials, whereas reduction of abortion rate and/or reduction in brucellosis prevalence were the outcomes assessed in 21 trials (63.63%). The most used serology test to evaluate brucellosis infection was Complement Fixation test (26/33, 78.78%), followed by Rivanol test (24/33, 72.72%). The great heterogeneity in the initial prevalence of the disease before vaccination (natural challenge), in the vaccination protocols and doses used, and in the adoption or not of other control policies associated with vaccination, prevented a meta-analysis of the studies included in the systematic review. In conclusion, the systematicreview results suggest that the S19 at the dose of 109 CFU is effective to reduce brucellosis prevalence in the herds when used in adult animals.
