title: BCG vaccination reduces risk of tuberculosis infection in vaccinated badgers and unvaccinated badger cubs.
abstract: Wildlife is a global source of endemic and emerging infectious diseases. The control of tuberculosis (TB) in cattle in Britain and Ireland is hindered by persistent infection in wild badgers (Meles meles). Vaccination with Bacillus Calmette-Guérin (BCG) has been shown to reduce the severity and progression of experimentally induced TB in captive badgers. Analysis of data from a four-year clinical field study, conducted at the social group level, suggested a similar, direct protective effect of BCG in a wild badger population. Here we present new evidence from the same study identifying both a direct beneficial effect of vaccination in individual badgers and an indirect protective effect in unvaccinated cubs. We show that intramuscular injection of BCG reduced by 76% (Odds ratio = 0.24, 95% confidence interval (CI) 0.11-0.52) the risk of free-living vaccinated individuals testing positive to a diagnostic test combination to detect progressive infection. A more sensitive panel of tests for the detection of infection per se identified a reduction of 54% (Odds ratio = 0.46, 95% CI 0.26-0.88) in the risk of a positive result following vaccination. In addition, we show the risk of unvaccinated badger cubs, but not adults, testing positive to an even more sensitive panel of diagnostic tests decreased significantly as the proportion of vaccinated individuals in their social group increased (Odds ratio = 0.08, 95% CI 0.01-0.76; P = 0.03). 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).
authors.affiliation: The Food and Environment Research Agency, York, North Yorkshire, United Kingdom. steve.carter@fera.gsi.gov.uk
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Carter
authors.forename: Mark A
authors.initials: MA
authors.lastname: Chambers
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Rushton
authors.forename: Mark D F
authors.initials: MD
authors.lastname: Shirley
authors.forename: Pia
authors.initials: P
authors.lastname: Schuchert
authors.forename: Stéphane
authors.initials: S
authors.lastname: Pietravalle
authors.forename: Alistair
authors.initials: A
authors.lastname: Murray
authors.forename: Fiona
authors.initials: F
authors.lastname: Rogers
authors.forename: George
authors.initials: G
authors.lastname: Gettinby
authors.forename: Graham C
authors.initials: GC
authors.lastname: Smith
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Delahay
authors.forename: R Glyn
authors.initials: RG
authors.lastname: Hewinson
authors.forename: Robbie A
authors.initials: RA
authors.lastname: McDonald
mesh_terms: D000818:Animals; D002417:Cattle; D004197:Disease Reservoirs / Q000662:veterinary*; D045969:Mustelidae / Q000276:immunology*; D009163:Mycobacterium bovis / Q000276:immunology; D014376:Tuberculosis / Q000517:prevention & control / Q000662:veterinary*; D032581:Tuberculosis Vaccines; D014380:Tuberculosis, Bovine / Q000517:prevention & control; D014611:Vaccination / Q000662:veterinary*
chemical_list: D032581:Tuberculosis Vaccines