Genome-Wide Association Study (GWAS) with resistance of Girolando cattle to ticks Rhipicephalus microplus

• Grant number: 14/12506-9
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: September 01, 2014
• End date: December 31, 2017
• Field of knowledge: Biological Sciences - Genetics - Animal Genetics
• Agreement: Coordination of Improvement of Higher Education Personnel (CAPES)
• Principal Investigator: Isabel Kinney Ferreira de Miranda Santos
• Grantee: Priscila Silva Oliveira
• Host Institution: Faculdade de Medicina de Ribeirão Preto (FMRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil

Abstract

Tick infestations in cattle are one of the main causes of economic losses in Brazilian cattle mainly due transmission of pathogens that lead to the development of various diseases with high morbidity and mortality in herds. The control of this ectoparasite is accomplished primarily through chemical acaricides used most often intensely and opportunistically, whereby frequent exposure to the various compounds employed leads to development of resistance of ticks to these acaricides, which become increasingly more inefficient. Moreover, the presence of residues of these chemicals in foods of animal origin compromises food security and may cause serious problems in public and environmental health. Thus, the search for effective alternatives for tick control has been steady and in this context, the study of genetic variability between individuals by Genome-Wide Association Studies (GWAS) is highlighted, since it identifies regions of the genome that are closely related to the resistance/susceptibility of cattle to infestation. Thus, the objective of this project is to conduct a GWAS with the phenotypes involved in the resistance of Girolando cattle to infestations by Rhipicephalus microplus ticks, cattle being genotyped by BovineHD Beadchip® of Illumina. The phenotypes chosen for analyses will be: visual evaluation and per image of the degree of infestation; pattern of coat and coat coloring; red blood cell counts; quantification of serum immunoglobulins; evaluation of the density, thickness and length of the hairs of the animals; reproductive capacity of engorged female ticks removed from animals' hindquarters; identification in skin of individuals considered extremes of volatiles produced in skin (semiochemicals) that act in repellency/attraction of ticks; identification of genes differentially expressed between these extreme animals through RNAseq. The results obtained will contribute to better understanding of the fundamental factors related to genetic variation and resistance of hosts to ticks, thus enabling sustainable improvements in control of this ectoparasite, primary responsible for substantial economic losses in cattle. (AU)