Title: Identification of single nucleotide polymorphisms (SNPs) associated to Red Maasai x Dorper resistance to gastrointestinal parasite infections Authors
Submitted to: BARC Poster Day
Publication Type: Abstract Only
Publication Acceptance Date: March 26, 2012
Publication Date: N/A
Technical Abstract: Gastrointestinal (GI) parasitic infection is a main health constraint that affects small ruminant production. Death may occur in severely affected animals, decreasing profits even further. Anthelmintic drugs are used to control parasites in hosts and their long-term use has led to a massive selection pressure, leading to parasite resistance against all current chemical interventions available in the market. Despite ongoing studies into alternative methods to control internal parasites, anthelmintic treatments remain the only viable option for control. The aim of this study is to identify polymorphisms strongly associated with sheep host resistance against gastrointestinal parasite infections. A double backcross population of Red Maasai and Dorper sheep from the International Livestock Research Institute (ILRI) was genotyped with the OvineSNP50K BeadChip. Data for average faecal egg counts (AVFEC), packed cell volume (AVPCV), and live weight (AVLWT) were adjusted for fixed effects prior to setting the threshold for the tails of the distributions (10% most resistant and 10% most susceptible lambs). Single nucleotide markers were filtered down to 31,904 following removing data where the minor allele frequency was less than 0.01%, call rates per marker less than 99.9%, and Hardy-Weinberg equilibrium criteria of less than 0.001% using PLink. Association analyses were calculated using QxPak v5.05 and significant SNPs with -Log10 p-values >=3 were observed on 15, 23 and 15 chromosomes for AVFEC, AVPCV and AVLWT, respectively. Three individual SNPs on chromosomes 7, 15 and 26 had significant estimate effects on AVPCV and AVLWT and other four individual SNPs on chromosomes 13, 14, 15 and 17 had concomitant estimate effects on AVPCV and AVFEC. Revised significance levels are being calculated using permutation tests. It is expected the results generated here will enable the identification of a subset of SNP to potentially allow selection for sheep resistance to gastrointestinal parasites based on a reduced density SNP panel.