Immune response to co-administration of Bacillus Calmette-Guérin (BCG) and contraceptive vaccines in badgers (Meles meles)

Controlling bovine tuberculosis (bTB) in livestock is often hindered by the presence of a wildlife reservoir, such as the Eurasian badger in the UK and Ireland. Vaccinating badgers against bTB can reduce the severity of Mycobacterium bovis infection and potential onwards transmission to cattle, badgers and other species; additional benefits may be achieved by combining this with fertility control to reduce population levels. To evaluate the effects of co-administering a bTB vaccine (BCG) and contraceptive vaccine (GonaCon), captive badgers were given either BCG only, GonaCon only or BCG + GonaCon (phase 1). The duration of immune response to BCG vaccination and booster vaccination was also evaluated in the BCG only group over a 24-month period (phase 2). The immune responses to purified protein derivatives PPDA and PPDB, used to measure the effects of BCG, did not differ significantly between the BCG only and BCG + GonaCon badgers but differed significantly between the BCG only and GonaCon only badgers. Anti-GnRH antibody titres, quantified to measure the effect of GonaCon, peaked at the first sampling point for most badgers in the GonaCon only and BCG + GonaCon groups. Throughout phase 1, lasting three months, badgers in both GonaCon treatment groups maintained high anti-GnRH antibody titres (1,128,000 or above) that are associated with infertility in this species, with no significant difference between the two GonaCon groups. The immune responses to BCG vaccination in the BCG only badgers (phase 2) were elevated at the first sampling point, approximately three weeks after initial and booster vaccination, generally declining thereafter. The results suggest that co-administering BCG and GonaCon did not affect the measured responses of each vaccine, and the cell-mediated responses were enhanced by booster vaccination. The protective effects afforded by both vaccines when given together, in terms of reduced disease burden or fecundity, should be determined by further studies.