Investigating the genetic basis of ivermectin resistance in Haemonchus contortus

Rezansoff, Andrew Mischa

Investigating the genetic basis of ivermectin resistance in Haemonchus contortus

dc.contributor.advisor	Gilleard, John Stuart
dc.contributor.author	Rezansoff, Andrew Mischa
dc.contributor.committeemember	Hansen, David
dc.contributor.committeemember	Rogers, Sean M.
dc.contributor.committeemember	Mains, Paul E.
dc.contributor.committeemember	Wasmuth, James D.
dc.contributor.committeemember	Geary, Tim C.
dc.date	2018-06
dc.date.accessioned	2018-05-08T14:59:04Z
dc.date.available	2018-05-08T14:59:04Z
dc.date.issued	2018-04-30
dc.description.abstract	Parasitic nematodes have a major impact on human and animal health and their control is threatened by the emergence of resistance to the anthelmintic drugs on which control depends. Although resistance to ivermectin is widespread in many livestock parasites, the genetic mechanisms remain elusive. In this thesis, a number of approaches are undertaken to investigate the genetics of ivermectin resistance in Haemonchus contortus, an important parasitic nematode research model. A transcriptomic comparison of the susceptible MHco3(ISE) and two ivermectin resistant strains, MHco4(WRS) and MHco10(CAVR), was undertaken to investigate if differences in gene expression revealed insights into ivermectin resistance mechanisms. Although this approach did not reveal clear ivermectin resistance gene candidates, the results have some important implications for RNAseq analysis in genetically diverse organisms. First, extremely high levels of genetic diversity in H. contortus had a major impact on RNAseq analysis and needed to be accounted for reliable identification of differentially expressed genes. Second, there were a remarkably large number of genes differentially expressed between the three H. contortus strains. In a novel genetic crossing approach, two independent serially backcrossed H. contortus populations were utilized in which ivermectin resistance loci had been introgressed into the MHco3(ISE) genome. Markers for six leading candidate ivermectin resistance genes from the literature were examined and none were found to show evidence of introgression in the backcross populations. A seventh marker, Hcms8a20 showed clear evidence of introgression and was later confirmed by collaborators using a whole genome sequencing approach to show its location in a 11.2 Mb introgressed region. A set of 25 in vivo or in vitro phenotyped ivermectin resistant H. contortus field populations were then used to investigate evidence of selection on the Hcms8a20 marker and four other loci distributed across the 11.2 Mb introgressed region. A deep amplicon sequencing approach revealed that, of the loci tested, only Hcms8a20 showed consistent evidence of purifying selection in the ivermectin resistant field populations. Overall, the results provide strong evidence that a major ivermectin resistance locus is located within a few megabases of the Hcms8a20 locus in many different ivermectin resistant H. contortus field populations.	en_US
dc.identifier.citation	Rezansoff, A. M. (2018). Investigating the genetic basis of ivermectin resistance in Haemonchus contortus (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/31897	en_US
dc.identifier.doi	http://dx.doi.org/10.11575/PRISM/31897
dc.identifier.uri	http://hdl.handle.net/1880/106615
dc.language.iso	eng
dc.publisher.faculty	Graduate Studies
dc.publisher.faculty	Veterinary Medicine
dc.publisher.institution	University of Calgary	en
dc.publisher.place	Calgary	en
dc.rights	University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.
dc.subject	Haemonchus contortus
dc.subject	H. contortus
dc.subject	Drug Resistance
dc.subject	Ivermectin
dc.subject	Anthelmintic
dc.subject	Parasite
dc.subject	Nematode
dc.subject	Livestock
dc.subject	Sheep
dc.subject	RNAseq
dc.subject	Deep amplicon sequencing
dc.subject	Population genetics
dc.subject.classification	Bioinformatics	en_US
dc.subject.classification	Genetics	en_US
dc.subject.classification	Biology--Molecular	en_US
dc.subject.classification	Parasitology	en_US
dc.subject.classification	Veterinary Science	en_US
dc.title	Investigating the genetic basis of ivermectin resistance in Haemonchus contortus
dc.type	doctoral thesis
thesis.degree.grantor	University of Calgary
thesis.degree.name	Doctor of Philosophy (PhD)
ucalgary.item.requestcopy	true