Herd-level risk factors for bovine tuberculosis and adoption of related biosecurity measures in Northern Ireland: A case-control study.

Bovine tuberculosis (bTB) is a zoonotic disease which is endemic in Northern Ireland. As it has proven difficult to eradicate this disease, partly due to a wildlife reservoir being present in the European badger (Meles meles), a case-control study was conducted in a high incidence area in 2010-2011. The aim was to identify risk factors for bTB breakdown relating to cattle and badgers, and to assess the adoption of bTB related biosecurity measures on farms. Face-to-face questionnaires with farmers and surveys of badger setts and farm boundaries were conducted on 117 farms with a recent bTB breakdown (cases) and 75 farms without a recent breakdown (controls). On logistic regression at univariable and multivariable levels, significant risk factors associated with being a case herd included having an accessible badger sett within the farm boundaries in a field grazed in the last year (odds ratio, OR, 4.14; 95% confidence interval, CI, 1.79, 9.55), observation of live badgers (OR 4.14; 95% CI 1.79, 9.55), purchase of beef cattle (OR 4.60; 95% CI 1.61, 13.13), use of contractors to spread slurry (OR 2.83; 95% CI 1.24, 6.49), feeding meal on top of silage (OR 3.55; 95% CI 1.53, 8.23) and feeding magnesium supplement (OR = 3.77; 95% CI 1.39, 10.17). The majority of setts within the farm boundary were stated to be accessible by cattle (77.1%; 95% CI 71.2, 83.0%) and 66.8% (95% CI 63.8, 69.7%) of farm boundaries provided opportunities for nose-to-nose contact between cattle. Adoption of bTB related biosecurity measures, especially with regards to purchasing cattle and badger-related measures, was lower than measures related to disinfection and washing.

Advances and prospects for management of TB transmission between badgers and cattle.

Bovine tuberculosis (bTB) is the most serious endemic disease facing the livestock industry in the United Kingdom (UK) and Republic of Ireland (RoI), where its management has been confounded by the presence of persistent infection in the Eurasian badger (Meles meles). Field evidence suggests that the social structure of badger populations can have an important influence on disease dynamics, and on the outcome of management interventions. Recent, large-scale badger culling experiments in the UK and RoI had complex epidemiological outcomes. In the UK, proactive culling led to reduced bTB incidence in cattle herds inside culled areas, but a temporary increase in adjacent areas. Reactive culling in response to herd breakdowns was associated with an increase in the incidence of bTB in cattle. In contrast, badger culling in RoI was reported to have only beneficial effects on bTB incidence in cattle. The reasons for these differences are not clear. The complexity of the evidence base for culling is highlighted by the different management approaches currently being adopted by the different authorities of the UK and RoI. It is generally accepted that a holistic approach to bTB management, which targets both cattle and wildlife, is necessary. Consequently recent research activities have also focussed on cattle and badger vaccines, and biosecurity on farms. This paper describes recent advances in our understanding of the epidemiology of bTB in badgers and the consequences of culling, and current research to develop approaches for the vaccination of badgers, and methods of managing the risks of contact between badgers and cattle in farm buildings.