Ovine beta-globin gene: A new qPCR for rapid haplotype identification and association with susceptibility to Haemonchus contortus infection

Two beta-globin allelic haplotypes (A and B) were identified in domestic sheep, wherein animals which are homozygous for beta(B) allele (BB haplotype) have a deletion of pre-adult beta(c)-globin and consequently are less tolerant to anemia and hypoxia. Since Haemonchus contortus infection, is associated with severe anemia, studies performed from 1960s to 1990s investigated the association between beta-globin haplotype and resistance against this parasite. However, the findings were controversial, pointing out from increased resistance in animals harboring the beta(A) allele to inexistence of association. Thus, our study aimed to develop a qPCR for beta-globin haplotype identification, and to evaluate the association between beta-globin haplotype and resistance against H. contortus in a group of sheep submitted to artificial infection with this parasite. A total of 286 lambs of Morada Nova breed were experimentally challenged with 4000 H. contortus L3 and monitored for 112 days from weaning. Significantly improved (p < 0.05) phenotypic profiles (lower fecal egg counts, higher packed cell volume and birthweight) were observed for AA haplotype animals, especially when compared to BB animals, while AB animals were similar to BB. This is the first report of a qPCR assay for ovine beta-globin haplotype identification. In view of significant differences of phenotypic profiles between haplotype groups, the developed qPCR may constitute an important tool for sheep producers to improve genetic selection of parasite resistant animals. (AU)