| Summary: | <p>Abstract</p> <p>Background</p> <p>Infestations on cattle by the ectoparasite <it>Boophilus (Rhipicephalus) microplus </it>(cattle tick) impact negatively on animal production systems. Host resistance to tick infestation has a low to moderate heritability in the range 0.13 - 0.64 in Australia. Previous studies identified a QTL on bovine chromosome 10 (BTA10) linked to tick burden in cattle.</p> <p>Results</p> <p>To confirm these associations, we collected genotypes of 17 SNP from BTA10, including three obtained by sequencing part of the <it>ITGA11 </it>(<it>Integrin alpha 11</it>) gene. Initially, we genotyped 1,055 dairy cattle for the 17 SNP, and then genotyped 557 Brahman and 216 Tropical Composite beef cattle for 11 of the 17 SNP. In total, 7 of the SNP were significantly (<it>P </it>< 0.05) associated with tick burden tested in any of the samples. One SNP, ss161109814, was significantly (<it>P </it>< 0.05) associated with tick burden in both the taurine and the Brahman sample, but the favourable allele was different. Haplotypes for three and for 10 SNP were more significantly (<it>P </it>< 0.001) associated with tick burden than SNP analysed individually. Some of the common haplotypes with the largest sample sizes explained between 1.3% and 1.5% of the residual variance in tick burden.</p> <p>Conclusions</p> <p>These analyses confirm the location of a QTL affecting tick burden on BTA10 and position it close to the <it>ITGA11 </it>gene. The presence of a significant association in such widely divergent animals suggests that further SNP discovery in this region to detect causal mutations would be warranted.</p>
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