Oral Vaccination of Free-Living Badgers (Meles meles) with Bacille Calmette Guérin (BCG) Vaccine Confers Protection against Tuberculosis

Abstract

A field trial was conducted to investigate the impact of oral vaccination of free-living badgers against natural-transmitted Mycobacterium bovis 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 M. bovis 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.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): bovine tuberculosis

“…When more than a third of their social group had been vaccinated, the risk to unvaccinated cubs was reduced by 79% (Odds ratio = 0.21, 95% CI 0.05-0.81; p = 0.02) (Chambers et al, 2011;Carter et al, 2012). The results of an oral BCG vaccination field trial conducted in Ireland on wild free-living badgers has also recently been published which has established that oral vaccination of free-living badgers can reduce the incidence of tuberculosis in free-ranging badger populations (Gormley et al, 2017).…”

“…The results of an oral BCG vaccination field trial conducted in Ireland on wild free‐living badgers has also recently been published which has established that oral vaccination of free‐living badgers can reduce the incidence of tuberculosis in free‐ranging badger populations (Gormley et al., ).…”

Mucosal vaccines and technology

“…oocysts, and significantly higher weight gain post-challenge infection [26]. Oral administration of BCG has been shown to reduce M. bovis lesions in badgers [32], with 75% of captured badgers in a further study testing positive for BCG vaccine markers where the vaccine was administered in bait [33]. Mucosal delivery of vaccines through baiting allows free-ranging animals to voluntarily uptake vaccines, in order to break down interspecies transmission of infectious disease between wild and domesticated animals.…”

BCG vaccination for bovine tuberculosis; conclusions from the Jerusalem One Health workshop

“…Therefore, induction of mucosal immunity could be beneficial and oral vaccination with BCG might be advantageous. Preliminary research into the use of oral BCG to protect cattle against bTB has been encouraging,(Buddle, Vordermeier, Chambers, & de Klerk‐Lorist, ; Nugent, Yockney, Whitford, Aldwell, & Buddle, ) as has been its application in wildlife reservoirs, such as possums in New Zealand (Tompkins et al., ) and badgers in Ireland (Gormley, Ní Bhuachalla, O'Keeffe, Murphy, & Aldwell, ). This experience, as well as the effective administration of rabies vaccine using bait, suggests that oral administration of BCG vaccine might be the most cost‐effective means of vaccinating wildlife (Pastoret & Brochier, ).…”

“…Vaccination would mainly aim to decrease TB transmission among wildlife and spread to domestic animals. The use of bait BCG vaccines for possums in New Zealand and badgers in Ireland resulted in significant TB protection (Gormley et al., ; Tompkins et al., ). Oral BCG vaccination of wild boar and deer also induced protection against challenge with M. bovis (Gortázar et al., ; Nol et al., ).…”