Temporal and seasonal trends of bovine tuberculosis in the Irish cattle population (2008–2024)
Jamie M. Madden, Eamonn Gormley, Philip Breslin, Damien Barrett, Jonas Brock, Jamie A. Tratalos, John Griffin, Mike Horan, Miriam Casey‐BryarsAbstract
Background
Bovine tuberculosis (bTB) has substantial impacts on the Irish cattle industry. Between 2016 and 2024, its burden increased in Irish cattle. As an initial step towards understanding drivers of this increase, we explore long‐term trends in measures of bTB burden and cattle demographics in Ireland.
Methods
Using data from 2008 to 2024, we describe changes in cattle management and demographics over time, as well as measures of bTB burden at herd‐ and animal‐level. A negative binomial regression model was implemented to explore the association between year and herd type and the count of bTB cases.
Results
Between 2008 and 2024, dairy herd numbers remained stable (∼12% of all herds), but expanded significantly in herd size (median increased from 119 to 172), with the proportion of national cattle in dairy herds increasing from 23% to 34%. The proportion of bTB cases from dairy farms doubled. In 2024, 51% of all individual bTB cases were from dairy herds compared to 26% in 2008.
Limitations
There may be misclassification biases in the disclosure of bTB cases across years due to policy changes in response to emerging evidence.
Conclusion
The burden of bTB has increased substantially since 2015, which has coincided with a large increase in median dairy herd size.