AbstractBackground: The aim of this study was to estimate variance components and to identify genomic regions andpathways associated with resistance to gastrointestinal parasites, particularly Haemonchus contortus, in a breed ofsheep adapted to tropical climate. Phenotypes evaluations were performed to verify resistance to gastrointestinalparasites, and were divided into two categories: i) farm phenotypes, assessing body condition score (BCS), degreeof anemia assessed by the famacha chart (FAM), fur score (FS) and feces consistency (FC); and ii) lab phenotypes,comprising blood analyses for hematocrit (HCT), white blood cell count (WBC), red blood cell count (RBC),hemoglobin (HGB), platelets (PLT) and transformed (log10) egg per gram of feces (EPGlog). A total of 576 animalswere genotyped with the Ovine SNP12k BeadChip (Illumina, Inc.), that contains 12,785 bialleleic SNP markers. Thevariance components were estimated using a single trait model by single step genomic BLUP procedure.Results: The overall linkage disequilibrium (LD) mean between pairs of markers measured by r2 was 0.23. The overallLD mean between markers considering windows up to 10 Mb was 0.07. The mean LD between adjacent SNPs acrossautosomes ranged from 0.02 to 0.10. Heritability estimates were low for EPGlog (0.11), moderate for RBC (0.18), PLT (0.17) HCT (0.20), HGB (0.16) and WBC (0.22), and high for FAM (0.35). A total of 22, 21, 23, 20, 26, 25 and 23 windows forEPGlog for FAM, WBC, RBC, PLT, HCT and HGB traits were identified, respectively. Among the associated windows, 10were shown to be common to HCT and HGB traits on OAR1, OAR2, OAR3, OAR5, OAR8 and OAR15.Conclusion: The traits indicating gastrointestinal parasites resistance presented an adequate genetic variability torespond to selection in Santa Inês breed, and it is expected a higher genetic gain for FAM trait when compared to theothers. The level of LD estimated for markers separated by less than 1 Mb indicated that the Ovine SNP12k BeadChipmight be a suitable tool for identifying genomic regions associated with traits related to gastrointestinal parasiteresistance. Several candidate genes related to immune system development and activation, inflammatory response,regulation of lymphocytes and leukocytes proliferation were found. These genes may help in the selection of animalswith higher resistance to parasites.