Evaluating the application of the dual path platform VetTB test for badgers (Meles meles) in the test and vaccinate or remove (TVR) wildlife research intervention project in Northern Ireland

Abstract

European badgers (Meles meles) are accepted as a wildlife reservoir host for Mycobacterium bovis, which causes bovine tuberculosis (bTB) in the British Isles. The objective of this study was to evaluate the use of Dual Path Platform (DPP) VetTB test (Chembio Diagnostic Systems Inc., Medford, NY, USA) within a Test and Vaccinate or Remove (TVR) wildlife research intervention project. Blood samples were collected from 456 individual badgers, trapped in 2015 and 2016, and tested in the field with DPP VetTB test using whole blood. Additionally, whole blood and serum samples were taken to the laboratory for further DPP VetTB testing and for gamma interferon (IFN-γ) testing. Swabs were taken from the oropharynx and trachea and submitted for bacteriological culture as were swabs from wounds, if present. Field DPP VetTB test positive badgers were euthanised and underwent post-mortem examination and bTB confirmatory testing. The results demonstrated that the test performed as well in the field using whole blood as DPP Vet TB tests in the laboratory using sera or whole blood, and as well as other established tests for M. bovis. Visual assessment of the DPP VetTB test using serum under laboratory conditions showed a high degree of consistency between raters. Using a relative gold standard (parallel interpretation of IFN-γ assay and oropharyngeal/tracheal sample/culture), sensitivity estimates for the DPP VetTB test using sera and whole blood were 0.5 (95%CI 0.34–0.66) and 0.42 (95%CI 0.24–0.66), respectively. Specificity estimates were 0.95 (95%CI 0.93–0.97) for sera and 0.89 (95%CI 0.86–0.92) for whole blood. Parallel interpretation of Band 1 (MPB83) and Band 2 (CFP-10/ESAT-6) of the DPP VetTB test was not superior to interpretation of Band 1 only. The results give confidence in the reliability and reproducibility of the DPP VetTB test for badgers under field conditions and therefore it is considered appropriate for use in a badger bTB control campaign.