Submitted to: Clinical and Vaccine Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 30, 2012
Publication Date: June 1, 2012
Citation: Olsen, S.C., Johnson, C.S. 2012. Efficacy of dart or booster vaccination with strain RB51 in protecting bison against experimental Brucella abortus challenge. Clinical and Vaccine Immunology. 19(6):886-890. Interpretive Summary: Brucella abortus is an intracellular pathogen that causes reproductive losses in cattle, bison and elk and which also causes zoonotic infections in people. Regulatory programs in domestic livestock, which include vaccination of livestock, are the most cost-efficient way to control Brucella abortus and prevent human infection. The persistence of brucellosis in bison in Yellowstone National Park may pose a threat for reintroduction of brucellosis to cattle in the United States. In this paper, we evaluated the protection induced by single vaccination, booster vaccination, or dart delivery of RB51 vaccine in bison. Only bison that had been booster vaccinated with the RB51 vaccine had reduced infections of abortion and reproductive infection as compared to non-vaccinated bison. However, all three RB51 vaccination schemes reduced infection in four target tissues after experimental challenge as compared to non-vaccinated bison. This data will be of interest to regulatory personnel, people with responsibilities for management of brucellosis in bison, livestock owners, and other parties with interests regarding brucellosis management.
Technical Abstract: Vaccination is an effective tool for reducing the prevalence of brucellosis in natural hosts. In this study, we characterized the efficacy of the Brucella abortus strain RB51 (RB51) vaccine in bison when delivered by single intramuscular vaccination (Hand RB51), single pneumatic dart delivery (Dart RB51), or after two vaccinations approximately 13 months apart (Booster RB51). Additional bison received intramuscular injections of saline (Control). All bison were experimentally challenged in midgestation by intraconjunctival administration of 107 CFU of B. abortus strain 2308 in accordance with the standard challenge model in the U.S. Bison were necropsied and tissues obtained for bacteriologic evaluation within 72 hr of abortion or delivery of a live, viable calf. When compared to rates in non-vaccinated bison, bison booster vaccinated with RB51 had a reduced (P<0.05) incidence of abortion, uterine infection, or infection in maternal tissues other than the mammary gland after experimental challenge with 2308. Bison in the single vaccination treatments (Hand RB51 and Dart RB51) did not differ (P>0.05) from the control group in the incidence of abortion, or recovery of S2308 from uterine, mammary, fetal, or maternal tissues at necropsy. When compared to control bison, all RB51 vaccination groups had reduced (P<0.05) mean colonization or incidence of infection in four target tissues taken at necropsy. In addition, Hand RB51 and Booster RB51 vaccinates had a reduced (P<0.05) incidence of infection in tissues obtained at necropsy as compared to samples obtained from non-vaccianted bison. The results of this study suggest that booster vaccination of bison with RB51 enhances protective immunity against experimental Brucella challenge when compared to single vaccination with RB51 by hand or by pneumatic dart. Our study suggests that an initial vaccination of calves followed by booster vaccination as yearlings will be an effective strategy for brucellosis control in bison.