Characterization of the duration of immunity of Brucella abortus strain RB51 vaccination in cattle after experimental challenge

Authors: Olsen, Steven; Boggiatto, Paola

Submitted to: Preventive Veterinary Medicine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/29/2022
Publication Date: 7/8/2022
Citation: Olsen, S.C., Boggiatto, P.M. 2022. Characterization of the duration of immunity of Brucella abortus strain RB51 vaccination in cattle after experimental challenge. Preventive Veterinary Medicine. 206. Article 105705. https://doi.org/10.1016/j.prevetmed.2022.105705.
DOI: https://doi.org/10.1016/j.prevetmed.2022.105705

Interpretive Summary: Brucellosis causes reproductive losses in cattle and is also a public health concern due to its potential for causing human disease. The United States has invested millions of dollars over the last 80 years in an effort to eradicate this disease. In this study we characterized the length of time that cattle are protected after calfhood vaccination with the commercial Brucella abortus strain RB51 vaccine. We found that immunity starts to wane after about 4 to 5 years after vaccination indicating that booster vaccination should be implemented in areas in which brucellosis is endemic. This data will be of interest to livestock producers and regulatory personnel as they design intervention strategies to prevent brucellosis infections in cattle.

Technical Abstract: Fifty-two, Hereford heifers were obtained from brucellosis-free herds and randomly assigned to B. abortus strain RB51 (RB51) vaccination (n=32) or control (n=20) treatments. Vaccinates received 10^10 colony-forming units (CFU) of a commercial lyophilized RB51 vaccine. Immunologic responses after inoculation demonstrated significantly greater (P<0.05) antibody, interferon-' responses, and proliferative responses to RB51 antigens in cattle vaccinated with RB51 as compared to controls. A subgroup of control and vaccinated cattle were experimentally challenged at approximately 4, 5, and 6 years after inoculation with 10^7 CFU of B. abortus strain 2308 at 170 to 180 days gestation. After experimental challenge, 6 of 14 (43 percent) control animals aborted at a higher rate (P less than 0.05) when compared to RB51 vaccinates in years 4 and 5, but not year 6 (0, 10, and 50 percent, respectively). When comparing recovery of Brucella from all tissue except head lymph nodes, RB51 vaccinates had reduced infection rates (P less than 0.05) after experimental challenge at 4 years (14 percent), but not at 5 or 6 years (78 and 67 percent, respectively) when compared to non-vaccinated cattle (93 percent). Our data suggests that calfhood vaccination with RB51 does not induce lifelong immunity and suggests implementation of booster vaccination by 4 to 5 years of age should be utilized in endemic areas to maintain high levels of protection.