Characteristics of Northern Irish cattle herds without bovine tuberculosis infection.

Background Despite ongoing eradication efforts, bovine tuberculosis (bTB) is endemic in cattle herds in Northern Ireland (NI). This disease has serious implications for the economy, farming and animal welfare. Previous research identified a population of herds which have remained free from bTB infection for 10 years (2004-2014). Understanding the characteristics of these herds may have important implications for eradication efforts, such as spatially targeted interventions. Methods A cluster analysis and a retrospective case-control analysis was conducted to compare bTB- free herds with herds which experienced prolonged infection (ie, bTB breakdowns lasting more than >= 365 days). Results Only small, localised clusters of herds which have remained free from bTB were revealed, thus limiting the potential for spatially targeted interventions. The results illustrated the importance of herd size to disease status; over 27 per cent of the bTB-free herds had up to 10 animals. However, the data also showed that there were no inward movements in the year before the bTB skin test in those herds which remained free from bTB. Conclusions Attention should therefore be given to the cattle movement network in NI to better understand the risk associated with cattle purchasing.