Bovine tuberculosis elimination: playing the long game

Bovine tuberculosis (bTB) has been around for centuries, with evidence of disease identified in prehistoric bovine remains1. It is likely that close contact between cattle, people and other animals has facilitated transmission since the agricultural revolution2. Mycobacterium bovis was first identified as the cause of bTB in the early 1900s, which lead to the elucidation of zoonotic transmission between cattle and people in the British and Irish dairy industries3. Since then many industrialised countries have tried to eliminate M. bovis from cattle populations to protect public health and trade, yet only some countries have achieved it. Australia took less than 30 years to coordinate intensive elimination of bTB. The national program was only successful after tackling herds or areas with persistent and recurrent breakdowns4. This historical snapshot highlights the ability for M. bovis to persist in cattle populations and why it is integral to understand the drivers for persistence in long-term bTB elimination programs.
In a study summarised on p xxx of this week’s Vet Record, Houtsma and others investigate the trend in bTB recurrence in Irish herds between 1998-2015. Like many other countries aiming to eliminate bTB, Ireland’s control strategy focuses on passive abattoir surveillance and active herd testing to identify infected animals to remove infected cattle5. Recurrence in herds decreased over the study period and exemplifies the importance in sustained elimination strategies. However, 30.2% of herds were still experiencing recurrence of bTB breakdowns in 2012-15. Highlighting that future research should look at the reasons for bTB persistence, including residual infection and re-introduction, to progress current elimination strategies.