5 research outputs found
Oral Vaccination of Free-Living Badgers (<i>Meles meles</i>) with Bacille Calmette Guérin (BCG) Vaccine Confers Protection against Tuberculosis
<div><p>A field trial was conducted to investigate the impact of oral vaccination of free-living badgers against natural-transmitted <i>Mycobacterium bovis</i> infection. For a period of three years badgers were captured over seven sweeps in three zones and assigned for oral vaccination with a lipid-encapsulated BCG vaccine (Liporale-BCG) or with placebo. Badgers enrolled in Zone A were administered placebo while all badgers enrolled in Zone C were vaccinated with BCG. Badgers enrolled in the middle area, Zone B, were randomly assigned 50:50 for treatment with vaccine or placebo. Treatment in each zone remained blinded until the end of the study period. The outcome of interest was incident cases of tuberculosis measured as time to seroconversion events using the BrockTB Stat-Pak lateral flow serology test, supplemented with post-mortem examination. Among the vaccinated badgers that seroconverted, the median time to seroconversion (413 days) was significantly longer (p = 0.04) when compared with non-vaccinated animals (230 days). Survival analysis (modelling time to seroconversion) revealed that there was a significant difference in the rate of seroconversion between vaccinated and non-vaccinated badgers in Zones A and C throughout the trial period (p = 0.015). For badgers enrolled during sweeps 1–2 the Vaccine Efficacy (VE) determined from hazard rate ratios was 36% (95% CI: -62%– 75%). For badgers enrolled in these zones during sweeps 3–6, the VE was 84% (95% CI: 29%– 97%). This indicated that VE increased with the level of vaccine coverage. Post-mortem examination of badgers at the end of the trial also revealed a significant difference in the proportion of animals presenting with <i>M</i>. <i>bovis</i> culture confirmed lesions in vaccinated Zone C (9%) compared with non-vaccinated Zone A (26%). These results demonstrate that oral BCG vaccination confers protection to badgers and could be used to reduce incident rates in tuberculosis-infected populations of badgers.</p></div
Kaplan-Meier survival curves (time to seroconversion) for non-vaccinated and vaccinated badgers during the whole period of study.
<p>Kaplan-Meier survival curves (time to seroconversion) for non-vaccinated and vaccinated badgers during the whole period of study.</p
Kaplan-Meier survival curves (time to seroconversion) for non-vaccinated and vaccinated badgers enrolled in sweeps 1–2 (A) and in sweeps 3–6 (B).
<p>Kaplan-Meier survival curves (time to seroconversion) for non-vaccinated and vaccinated badgers enrolled in sweeps 1–2 (A) and in sweeps 3–6 (B).</p
Distribution of badgers enrolled in vaccine field trial by age, sex and zone of capture.
<p>Distribution of badgers enrolled in vaccine field trial by age, sex and zone of capture.</p
Time (days) to seroconversion for all badgers that seroconverted during the trial: non-vaccinated (N = 30), vaccinated (N = 21).
<p>Time (days) to seroconversion for all badgers that seroconverted during the trial: non-vaccinated (N = 30), vaccinated (N = 21).</p