2015 ACVIM Forum Research Abstract Program

A total of 129 horses (61 affected, 68 unaffected) from experimental and natural infections were included in a genome wide association study (GWAS) to identify host genetic variation associated with EHM. Genotyping was performed using the Illumina SNP50 and SNP70 arrays and a custom Sequenom array. Mixed linear model (MLM) analysis using a dominant model identified one marker that surpassed the threshold for genome-wide significance (P = 9.50 9 10 À7 ) after Bonferroni correction. The marker is in an intron of TSPAN9, a gene expressed in endothelium and platelets. Four of the top 20 markers (P ≤ 2.58 9 10 À4 ) were in an immune gene cluster including an interferon gamma receptor. A separate Bayesian analysis of the same marker set identified four windows that each accounted for >1% of the genetic variance and harbored significant quantitative trait loci.