Spatiotemporal analysis of caprine tuberculosis in Castilla y León, Spain, 2011–2023: using molecular epidemiology to guide eradication efforts

Caprine tuberculosis (cTB) is a chronic zoonotic disease primarily caused by Mycobacterium caprae and M. bovis affecting mainly goats, but also other mammalian species, including humans. Despite its epidemiological significance, Spain lacks a national eradication programme in goats, but regional efforts have been implemented, mainly based on a test and cull strategy. This 13-year longitudinal study (2011–2023) aimed to analyze spatiotemporal trends in cTB distribution to assess the programme's effectiveness and to identify persistent 'hot spots' of the disease. The cTB programme in Castilla y León has reduced the apparent herd prevalence from 5.5% in 2011 to 1.1% in 2023, leading to the declaration of several provinces (7/9) as cTB-free. Ávila was the province with the highest prevalence and contained a significant ( p < 0.001) spatial cluster of positive dairy herds and most outbreaks detected during the study period. Whole Genome Sequencing (WGS) and SNP analysis of the dominant M. bovis SB0121 genotype identified six genetic clusters of isolates with putative epidemiological relations (≤ 12 SNPs) circulating in 17 flocks located in the municipality where was present the cluster and the neighboring municipality. This study highlights the reduction in TB prevalence in goats due to a cTB eradication programme. However, persistent high-risk areas with recurrent outbreaks were still identified, suggesting that local transmission continues despite the overall decline in prevalence. For this reason, the integration of spatiotemporal analysis, WGS and SNP analysis in tracking the sources of recurrent TB outbreaks to guide targeted eradication measures in these high-risk areas could be a valuable strategy.