This study aimed at identifying genomic regions that underlie genetic variation of worm egg count, as an indicator trait for parasite resistance in a large population of Australian sheep, which was genotyped with the high-density 600 K Ovine single nucleotide polymorphism array. This study included 7539 sheep from different locations across Australia that underwent a field challenge with mixed gastrointestinal parasite species. Faecal samples were collected and worm egg counts for three strongyle species, i.e. Teladorsagia circumcincta, Haemonchus contortus and Trichostrongylus colubriformis were determined. Data were analysed using genome-wide association studies (GWAS) and regional heritability mapping (RHM). Both RHM and GWAS detected a region on Ovis aries (OAR) chromosome 2 that was highly significantly associated with parasite resistance at a genome-wise false discovery rate of 5%. RHM revealed additional significant regions on OAR6, 18, and 24. Pathway analysis revealed 13 genes within these significant regions (SH3RF1, HERC2, MAP3K, CYFIP1, PTPN1, BIN1, HERC3, HERC5, HERC6, IBSP, SPP1, ISG20, and DET1), which have various roles in innate and acquired immune response mechanisms, as well as cytokine signalling. Other genes involved in haemostasis regulation and mucosal defence were also detected, which are important for protection of sheep against invading parasites. This study identified significant genomic regions on OAR2, 6, 18, and 24 that are associated with parasite resistance in sheep. RHM was more powerful in detecting regions that affect parasite resistance than GWAS. Our results support the hypothesis that parasite resistance is a complex trait and is determined by a large number of genes with small effects, rather than by a few major genes with large effects.

中文翻译：

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检测澳大利亚绵羊对胃肠道寄生虫的抵抗力的基因组区域

这项研究的目的是确定作为蠕虫卵计数遗传变异基础的基因组区域，以此作为大量澳大利亚绵羊的寄生虫抗药性的指示性状，该基因型已通过高密度600 K绵羊单核苷酸多态性阵列进行了基因分型。这项研究纳入了来自澳大利亚各地的7539只绵羊，这些绵羊受到混合胃肠道寄生虫物种的野外挑战。收集粪便样品，并测定三种圆虫种类的蠕虫卵计数，即圆头臭ador虫，弯曲变形杆菌和粘膜毛线虫。使用全基因组关联研究（GWAS）和区域遗传力作图（RHM）分析数据。RHM和GWAS都检测到Ovisaries（OAR）2号染色体上的一个区域，该区域与寄生虫抗性高度显着相关，在基因组方面的错误发现率为5％。RHM揭示了OAR6、18和24上的其他重要区域。通路分析揭示了这些重要区域内的13个基因（SH3RF1，HERC2，MAP3K，CYFIP1，PTPN1，BIN1，HERC3，HERC5，HERC6，IBSP，SSP1，ISG20和DET1） ，它们在先天和后天免疫应答机制以及细胞因子信号传导中具有多种作用。还检测到其他与止血调节和粘膜防御有关的基因，这些基因对于保护绵羊免受入侵的寄生虫很重要。这项研究确定了OAR2、6、18和24上与绵羊的寄生虫抗性相关的重要基因组区域。与GWAS相比，RHM在检测影响寄生虫抗性的区域中功能更强大。我们的结果支持以下假设：寄生虫抗性是一个复杂的性状，并由大量影响较小的基因决定，而不是由少数几个影响较大的主要基因决定。