Two vaccines given together show promise for badger TB and fertility control

Bovine tuberculosis (bTB) in livestock is hard to control when wildlife species act as a reservoir for Mycobacterium bovis. In the UK and Ireland, the Eurasian badger (Meles meles) is one such reservoir, and this has prompted research into ways to reduce infection in badgers to protect cattle and other animals. One idea is to combine disease vaccination with fertility control to both lower the severity or spread of bTB and reduce population growth. To explore whether two vaccines can be given together safely, researchers led by corresponding author Kate L. Palphramand tested co-administration of a bTB vaccine and a contraceptive vaccine in captive badgers. Badgers were injected intramuscularly and split into treatment groups: BCG only, GonaCon only, or BCG+GonaCon for a short-term study (phase 1). The team also followed a BCG only group over a longer period, including booster vaccination, to track the duration of the immune response (phase 2). The study focused on measurable immune markers to see if giving both vaccines at once changed how badgers responded to either vaccine.

The study used established immune tests and tracked responses over time. Cellular immune responses to purified protein derivatives PPDA and PPDB, which are used to measure the effects of BCG vaccination, were compared among groups. Those responses did not differ significantly between the BCG only and BCG+GonaCon badgers, indicating that adding GonaCon did not blunt the BCG cellular response; however, responses were significantly different between the BCG only and GonaCon only badgers. To measure contraceptive response, the team quantified anti-GnRH antibody titres after GonaCon vaccination. In both the GonaCon only and the BCG+GonaCon groups, anti-GnRH antibody titres peaked at the first sampling point for most badgers and remained high through phase 1 (lasting three months post-vaccination). Titres stayed at or above 1:128,000, a level associated with infertility in this species, and there was no significant difference between the two GonaCon groups. In the longer phase 2 follow-up for the BCG only badgers, immune responses were elevated about three weeks after initial vaccination and booster vaccination and generally declined thereafter. All vaccines were administered intramuscularly.

Taken together, the results suggest that co-administration of BCG and GonaCon in captive badgers did not produce notable harmful effects on the immune responses measured for either vaccine. The finding that cellular responses to PPDA and PPDB were similar in BCG treated badgers whether or not they also received GonaCon supports the view that the two vaccines can be given together without obvious interference. Meanwhile, GonaCon induced strong anti-GnRH antibody titres associated with infertility that were maintained for at least three months, and booster vaccination appeared to enhance the BCG immune response. The authors are careful to point out that while immune markers are encouraging, the actual protective effects—meaning reduced disease burden from bTB or reduced fecundity when the vaccines are given together—remain to be demonstrated. Further studies, especially field trials that measure disease outcomes and reproduction, are needed before managers can adopt combined vaccination as a tool for bTB control and wildlife population management.