Genetic markers identification and genotyping for resistance to internal parasites in sheep and goat infected with Haemonchus contortus

TitleGenetic markers identification and genotyping for resistance to internal parasites in sheep and goat infected with Haemonchus contortus
Publication TypeJournal Article
Year of Publication2016
AuthorsReyes, ZMEstrada, Goetsch, AL, Gipson, TA, Wang, Z, Rolf, M, Sahlu, T, Puchala, R, Zeng, S, Mateescu, R
JournalJournal of Animal Science
Pagination159 - 160
Date PublishedJan-10-2016
AbstractGastrointestinal nematode infections (GNI) have a great economic impact for small ruminant production in humid areas. In these regions, Haemonchus contortus is the most important gastroenteric nematode. Unfortunately, the indiscriminate use of anthelmintic drugs to control GNI has generated resistance to these chemical compounds. Among the alternative strategies proposed, the genotypic and phenotypic variability of the small ruminants have encouraged the identification of the most resistant animals. To identify genetic markers associated with the control of nematode populations within the host, the detection of single nucleotide polymorphisms (SNPs) OLA-DRA20 gene was performed in sheep and goats experimentally infected with H. contortus. Animals from 3 different breeds of sheep and goat were used for the study during 3 yr of evaluation. Individuals were selected by using positive assortative mating of the most resistant individuals each year and received a complete diet (15% Crude Protein) ad libitum for the duration of the trial. Animals were treated with levamisole (7.5 mg/kg of live weight) 3 wk before the start of the trial. After deworming, each experimental animal was infected with 10,000 L3 of H. contortus per kg of body weight per oral route. Fecal samples were obtained to determine fecal egg count using the modified McMaster technique. Blood samples were collected from the jugular vein with sterile vacuum tubes with sodium heparin to evaluate blood package cell volume (PCV) and levels of IgA, IgM and IgG. DNA was purified from blood samples using DNeasy Blood & Tissue Kit (Qiagen). One SNP in the OLA-DRA20 segregating in this population was analyzed using High Resolution Melting assays and three genotypes were observed (AA, GA, GG). A GLM was fitted with MPCV, DMI, ADG, RFI, IgM, IgG, IgA levels and genotype as predictors and the square root of the mean of FEC as the response variable. According the results, the best significant predictors to fit the model were Genotype, Breed (Species), MPCV, DMI, ADG and genotype (P < 0.05). In conclusion, the polymorphism in the OLA-DRA20 gene could have an important role in the immune mechanisms against H. contortus infections in sheep and goats. Indeed, these results provided evidence that there is a significant effect among the square root of the mean of FEC and production traits between breeds within species.