The Enferplex Bovine TB antibody test shows a significant degree of positivity in both restricted and officially tuberculosis free herds in a national study of bulk tank milk samples from dairy herds in Great Britain

Background Herd level bovine tuberculosis (bTB) surveillance worldwide is based on tuberculin testing (TT). The World Organisation for Animal Health has approved Enferplex Bovine TB antibody test (EP) for diagnosing bTB using bulk tank milk (BTM) samples and the use of this methodology provides the potential for a more resource efficient system of herd surveillance for bTB than is the case with TT. We aimed to assess whether there would be any benefit of routine BTM testing in Great Britain (GB) with the EP to the surveillance and control of bTB. Methods We enrolled 4,830 dairy herds. Three sets of BTM samples were collected at three-month intervals from each herd without knowledge of their bTB status and analysed independently. A smaller cohort of 73 herds, that provided monthly samples over six months, was independently recruited. To provide a high confidence in the positive results, the risk of false positive results was minimised via minor adjustments to the test algorithm. To examine the impact on surveillance we assessed the prevalence and incidence of EP positive herds by the bTB risk area they were located and their bTB status based on Government surveillance data. Results Twenty-five percent of herds tested positive at least once. In herds under restriction throughout the study, and whose tuberculin reactor animals had been removed (n=240), the test detected 40.4% (95% CI: 34.2-46.9) as positive. Monthly BTM sampling significantly increased the percentage of positive herds over quarterly sampling from 45% (95% CI: 26.9-65.4) to 64% (95% CI: 42.9-80.4) (P< 0.001). In herds designated as Officially Tuberculosis Free (OTF) throughout the study, 19.4% (95% CI: 18.1-20.7) tested positive. Conclusion EP BTM testing registers substantial proportions of restricted and OTF herds as positive. EP adoption in surveillance programmes offers the potential for an overt improvement in bTB detection and thereby control.