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. Objectives To 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 Design Cross‐sectional observational study. Methods A 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 ( CXCL16 r/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.
Gago et al. (Thu,) studied this question.