Behaviour of European badgers and non-target species towards candidate baits for oral delivery of a tuberculosis vaccine

Abstract

In the UK and the Republic of Ireland, the European badger (Meles meles) is a maintenance host for Mycobacterium bovis, and may transmit the infection to cattle causing bovine tuberculosis (TB). Vaccination of badgers using an injectable Bacillus Calmette-Guerin (BCG) vaccine is undertaken in some areas of the UK with the intention of interrupting this transmission, and vaccination research is underway in Ireland. An oral badger TB vaccine is also under development. We investigated the behaviour of badgers and non-target wildlife species towards three candidate baits being considered for delivering BCG to badgers orally. Bait preference was investigated by recording removal rates of baits and through the use of video surveillance at 16 badger setts. We found high variation in rates of bait removal by badgers among setts but no significant differences in removal rates among bait types or in preference behaviour from video footage. Variation in bait removal among setts correlated with the number of nights on which badgers were seen at the sett, with most baits being removed where badgers were seen on >50% of nights during the ten-day study period. Relatively few baits were removed at setts with low levels of recorded badger activity. Monitoring badger activity prior to bait deployment may therefore be useful in increasing bait uptake and vaccine coverage. Bait removal by badgers increased over the ten-day study period, suggesting initial neophobic behaviour at some setts and that a period of 'pre-feeding' may be required prior to vaccine deployment. Our results indicate that all three candidate baits are attractive to badgers. Removal of baits by non-target wildlife species was generally low, but varied among bait types, with smaller baits in packaging less likely to be removed. Enclosing baits in packaging is likely to deter non-target species, although in some cases non-target species did remove up to 13% of packaged baits.

The Effect of Oral Vaccination with Mycobacterium bovis BCG on the Development of Tuberculosis in Captive European Badgers (Meles meles)

“…We achieved those objectives. Ultimately BCG will need to be delivered to wild badgers in bait and we are making progress toward that objective (Robertson et al, 2016). For the purposes of this study it was important that we could control the dose of BCG each badger received so the animals were dosed manually.…”

Testing of a palatable bait and compatible vaccine carrier for the oral vaccination of European badgers (Meles meles) against tuberculosis

“…There are unavoidable limitations associated with the use of captive animals for bait tests, namely the limited sample size and the possible effects of an artificial diet on bait preference and consumption. However, promising materials were always field-tested and these tests reflected the high attractiveness and palatability of the PT-HPO baits observed with captive animals [17].…”

“…90 x 170 mm). Different types of packaging were being evaluated in order to inform packaging field tests[17]. Materials such as plastic-lined paper may offer increased protection to the bait against moisture, relative to a paper bag.Individual animals were trapped overnight in cages with a single bait for one night only;water was provided in a bowl.…”

Baited vaccines: A strategy to mitigate rodent‐borne viral zoonoses in humans

“…If a vertebrate community contains multiple reservoir host species, then the vaccine bait must be palatable to all, as only vaccinating a part of the reservoir community will of course result in lower efficacy (Tsao et al, ). Of course, if the community of vertebrates is diverse but contains only one reservoir competent species, it would be preferable if vaccine‐containing bait is not appetizing for a wide range of species, otherwise a lot of bait will be consumed to no effect by non‐reservoir species, which would compete with the reservoir species for the bait (Robertson et al, ). In diverse vertebrate host communities, negative effects of vaccines, baits or other aspects of vaccination regimes on non‐target species need to be identified and eliminated as far as is feasible (Fry et al, ).…”