Doyle, L.P.Courcier, E.A.Gordon, Alan WesleyO'Hagan, M.J.H.Johnston, P.McAleese, E.Buchanan, J.R.Stegeman, J.A.Menzies, F.D.2020-10-202020-10-202020-09-28Doyle, L. P., Courcier, E. A., Gordon, A. W., O’Hagan, M. J. H., Johnston, P., McAleese, E., Buchanan, J. R., Stegeman, J. A. and Menzies, F. D. (2020) ‘Northern Ireland farm-level management factors for prolonged bovine tuberculosis herd breakdowns’, Epidemiology and Infection. Cambridge University Press (CUP), 148. doi: 10.1017/s0950268820002241.1469-4409https://doi.org/10.1017/S0950268820002241Publication history: Accepted - 16 September 2020; Published online - 28 September 2020This study determined farm management factors associated with long-duration bovine tuberculosis (bTB) breakdowns disclosed in the period 23 May 2016 to 21 May 2018; a study area not previously subject to investigation in Northern Ireland. A farm-level epidemiological investigation (n = 2935) was completed when one or more Single Intradermal Comparative Cervical Test (SICCT) reactors or when one or more confirmed (positive histological and/or bacteriological result) lesion at routine slaughter were disclosed. A case-control study design was used to construct an explanatory set of management factors associated with long-duration bTB herd breakdowns; with a case (n = 191) defined as an investigation into a breakdown of 365 days or longer. Purchase of infected animal(s) had the strongest association as the most likely source of infection for long-duration bTB herd breakdowns followed by badgers and then cattle-to-cattle contiguous herd spread. However, 73.5% (95% CI 61.1–85.9%) of the herd type contributing to the purchase of infection source were defined as beef fattening herds. This result demonstrates two subpopulations of prolonged bTB breakdowns, the first being beef fattening herds with main source continuous purchase of infected animals and a second group of primary production herds (dairy, beef cows and mixed) with risk from multiple sources.en© The Author(s), 2020. Published by Cambridge University Press This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.Bovine tuberculosis, case-control study, cattle, chronic breakdowns, epidemiology, Mycobacterium bovisArticle