Bait uptake by wild badgers and its implications for oral vaccination against tuberculosis

Abstract

The deployment of baits containing vaccines or toxins has been used successfully in the management of wildlife populations, including for disease control. Optimisation of deployment strategies seeks to maximise uptake by the targeted population whilst ensuring cost-effectiveness. Tuberculosis (TB) caused by infection with Mycobacterium bovis affects a broad range of mammalian hosts across the globe, including cattle, wildlife and humans. The control of TB in cattle in the UK and Republic of Ireland is hampered by persistent infection in European badgers (Meles meles). The present study aimed to determine the best strategy for maximising uptake of an oral vaccine by wild badgers, using a surrogate novel bait deployed at 40 badger social groups. Baits contained a blood-borne biomarker (Iophenoxic Acid, IPA) in order to measure consumption in badgers subsequently cage trapped at targeted setts. Evidence for the consumption of bait was found in 83% (199/240) of captured badgers. The probability that badgers had consumed at least one bait (IPA >10 μg ml-1) was significantly higher following deployment in spring than in summer. Lower uptake amongst social groups where more badgers were captured, suggested competition for baits. The probability of bait consumption was significantly higher at groups where main and outlier setts were provided with baits than at those where outliers were present but not baited. Badgers captured 10–14 days post bait feeding had significantly higher levels of bait uptake compared to those caught 24–28 days later. Uptake rates did not vary significantly in relation to badger age and whether bait was placed above ground or down setts. This study suggests that high levels of bait uptake can be achieved in wild badger populations and identifies factors influencing the potential success of different deployment strategies. The implications for the development of an oral badger vaccine are discussed.

Anti‐tick and pathogen transmission blocking vaccines

“…For example, a study in European badgers (Meles meles) showed carob and cocoa baits were most frequently investigated and removed, 112 with highest consumption rates in the spring. 113 Studies with Peromyscus leucopus mice showed that no attractant is needed to entice wild mice to bait consumption, 104 whereas the house mouse Mus musculus preferred canary and soft wheat baits. 110 In red deer, alfalfa baits were shown to have good consumption in target species with reduced consumption by nontarget species such as corvids.…”

“…Laboratory and field trials will inform bait formulation, ensuring the bait is consumed by target species. For example, a study in European badgers ( Meles meles ) showed carob and cocoa baits were most frequently investigated and removed, 112 with highest consumption rates in the spring 113 . Studies with Peromyscus leucopus mice showed that no attractant is needed to entice wild mice to bait consumption, 104 whereas the house mouse Mus musculus preferred canary and soft wheat baits 110 .…”

Breaking down population density into different components to better understand its spatial variation

“…In the present study, we aimed at determining badger densities in 13 different areas of metropolitan France, using a robust combination of methodological approaches. In moderate to high density populations, as the territory of a social group can encompass several setts [ 20 – 22 ], we grouped nearby setts together and considered clusters of setts instead of setts. We first estimated the density of sett clusters of each study site using distance sampling [ 23 , 24 ] on walked transects, and then estimated the proportion of occupied sett clusters (an approximation of the number of social groups in a given area).…”

Bioreactor-Grown Bacillus of Calmette and Guérin (BCG) Vaccine Protects Badgers against Virulent Mycobacterium bovis When Administered Orally: Identifying Limitations in Baited Vaccine Delivery

“…Success is dependent on combining a vaccine that is safe and efficacious via the oral route with attractive bait that can be delivered using a pragmatic and economical deployment protocol. Several studies report the successful development of an oral bait for use with wild badgers that is both attractive and highly palatable, as well as being compatible with the live, attenuated Bacillus of Calmette and Guérin (BCG) vaccine [7][8][9]. The vaccine itself has been shown to be efficacious when given orally to badgers, followed by experimental challenge with virulent M. bovis [10,11].…”