Oral communication in 17th International Symposium of Veterinary Epidemiology and Economics (ISVEE 17)

November 14^th, 2024

Torre-Fuentes L., Pozo P., Ortega MJ., Fernadez-Oropesa R., Duran M., Saez JL. and Alvarez J.

Molecular typing techniques with a high discriminatory power can help to decipher the evolution of pathogens over time and assess the impact of control measures on their genetic diversity. Brucella abortus, causative agent of bovine brucellosis and among the most successful zoonotic pathogens in the world, was once endemic in the cattle population in Spain. However, national eradication programs based on vaccination (until 1996 except for high incidence zones), test-and-cull strategies and depopulation of infected herds in the last stages of the program, led to the declaration of the country as free of the disease in 2022. Here, we subjected a representative panel of 129 B. abortus biovar 3 strains retrieved over the 1991- 2020 period from 11 Autonomous Regions in Spain to whole-genome sequencing to evaluate the relatedness between isolates retrieved from different regions and over time and to investigate the potential effect of the control and eradication strategies (S19 or RB51 vaccination, whole-herd depopulation) implemented over the 30-year period. Sequences with sufficient quality along with other B. abortus genomes from different sources and countries, included to provide context, were subjected to phylogenetic and phylodynamic analyses. All successfully sequenced strains (N=120) belonged to the previously described clade C except one (clade D) and did not mix with strains from other geographically close Mediterranean countries. The 119 clade C strains were allocated into two subclades separated by a median of 50 SNPs (IQR 42-55), with a lower withinsubclade variability (mean 14-24 SNPs). Both clades were present in all regions and years, and no correlation between the genetic distance and the spatial or temporal distances between isolates was found, suggesting that long distance animal movements played a significant role in disease spread and certain strains were able to persist across multiple regions irrespective of measures applied

	Centro de Vigilancia Sanitaria Veterinaria (VISAVET). Universidad Complutense (UCM).
	Instituto de Investigación en Recursos Cinegéticos (IREC). Consejo Superior de Investigaciones Científicas (CSIC). Universidad de Castilla La Mancha (UCLM). Gobierno de Castilla-La Mancha (JCCM).
	Laboratorio Central de Veterinaria (LCV). Ministerio de Agricultura, Pesca y Alimentación (MAPA).
	Dirección General de la Producción Agraria. Ministerio de Agricultura, Pesca y Alimentación (MAPA).