Microsatellite Polymorphism in DRB2 Gene and its Relation to Haemonchus Contortus Parasites Fecal Egg Count in Iranian Ghezel Sheep

Abstract

<strong>Gastrointestinal parasites are one of the main sources of economic decline in sheep production around the world. Resistant sheep do not completely reject the disease; they only harbor fewer parasites than susceptible sheep and therefore have a lower fecal egg count. The present research was designed to evaluate microsatellite polymorphism in intron 5 of DRB2 gene and its correlation with <em>H. contortus</em> fecal egg counts in Ghezel sheep breed. For this reason, blood samples were taken from 80 male lambs between 4-6 months of age and some phenotypic traits including fecal egg counts (FEC), FAMACHA test, and packed cell volume (PCV) were measured. Blood DNA was extracted using chloroform-isoamyl alcohol protocol; then, microsatellite regions in intron 5 of DRB2 gene were replicated. Afterward, 3% agarose gel electrophoresis using ethidium bromide staining was performed to evaluate 25 base pairs allele size products using UVidoc software. Finally, the correlation between genotype and phenotypic traits was analyzed by linear and nonlinear mixed models using SAS software. The results showed that lambs having present genotype homozygous 300 were low FEC with lower prevalence of this kind of parasite than lambs having other types of homozygous genotypes. Based on the results, correlation between FAMACHA and PCV was -0.625 (p­< 0.01); while, the correlation between FAMACHA and FEC was 0.731 (p< 0.01). Accordingly, the presence of allele 300 could be considered as a selecting indicator for animals with relatively higher resistance to <em>H. contortus</em> parasite. Also, the results suggested that PCV and FEC as well as FAMACHA can be used as reliable indicators for detecting <em>H. contortus</em> infection rate.</strong>