CXCL16-associated genetic susceptibility to equine viral arteritis in export-bound horses from Spain

Abstract

Background: Equine viral arteritis (EVA) remains a relevant health and economic concern due to the ability of some infected stallions to establish long-term persistent infection with equine arteritis virus (EAV). Allelic variation in the CXCL16 gene has been identified as a determinant of susceptibility or resistance to the carrier state, positioning genotyping as a useful tool for risk-based reproductive and health management.ObjectivesTo characterise the distribution of CXCL16 genotypes in export-bound horses from Spain and to assess the utility of CXCL16 genotyping for EVA prevention and control.Study DesignCross-sectional observational study.MethodsA total of 1004 horses of multiple breeds and geographic origins were included. CXCL16 genotypes were determined in all animals, and EAV serological status was assessed in a subset of 358 samples using ELISA. Genotypic frequencies were calculated, and associations with breed and sex were analysed. Results: The resistant genotype (CXCL16r/r) predominated in the study population (57.3%), although marked breed-related variability was observed. Lower frequencies of the resistant genotype were detected in Iberian breeds, including Spanish Purebred (53.3%) and Lusitano (38.3%), with higher frequencies observed in Thoroughbreds (77.6%) and European sport horse breeds. Breed composition was the main factor associated with differences in CXCL16-associated susceptibility profiles, while the effect of sex was limited. Among the 358 horses tested by ELISA, 3.9% (n = 14) were seropositive for EAV. Main Limitations: The study population was restricted to export-bound horses; some breeds were underrepresented, and the cross-sectional design did not allow direct assessment of long-term viral persistence. Conclusions: This is the first large-scale characterisation of CXCL16 genotype distribution in export-bound horses in Spain and demonstrates marked breed-related differences in genetic susceptibility to EAV persistence. CXCL16 genotyping represents a valuable complementary tool to serological surveillance for supporting risk-based EVA management and informed decision-making in breeding and export programmes.