Seroprevalence and factors associated with seropositivity to equine arteritis virus in Spanish Purebred horses in Spain

Summary Reasons for performing study Equine viral arteritis (EVA), a disease caused by infection with the equine arteritis virus (EAV), is present in many European countries. In Spain, the last confirmed outbreak was reported in 1992 and there is a paucity of seroprevalence studies. The disease has a major impact on the equine breeding industry, which is mainly represented by Spanish Purebred (SP) horses in Spain. Objectives To estimate the seroprevalence of EAV in the breeding SP horse population in central Spain and identify potential horse and studfarm level factors associated with seropositivity to EAV. Study design Cross‐sectional study. Methods Individual serum samples from 555 SP horses, collected between September 2011 and November 2013 at 35 studfarms, were tested using a commercially available EAV antibody ELISA and seroneutralisation as the World Organisation for Animal Health reference confirmation test for samples with positive and equivocal results. Data on factors putatively associated with seropositivity to EAV were collected via a questionnaire and examined using random effects logistic regression for analysis of clustered data. Results Equine arteritis virus seroprevalence in the SP breeding population in central Spain standardised for the sex distribution of the reference horse population, was estimated to be 16.8% (95% confidence interval 5.2–28.5%). Increasing numbers of breeding mares on the studfarm and increasing percentage of mares with reproductive problems during the last 12 months were identified as being positively associated with EAV seropositivity. Mares vaccinated against Equine herpesvirus‐1 (EHV‐1) and/or ‐4 (EHV‐4) were also positively associated with EAV seropositivity. Conclusions These findings are of importance to ensure appropriate biosecurity measures for studfarms are carried out and may help facilitate the development of an EVA surveillance programme in the SP breeding horse population.