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Sustainable use of levamisole through elucidation of genetic markers of resistance and molecular diagnostics in Haemonchus contortus," investigates the use of levamisole to control the parasitic nematode Haemonchus contortus. The thesis aims to improve resistance monitoring by identifying genetic markers of levamisole resistance and developing molecular diagnostic assays. Whole genome sequencing data from a controlled genetic cross identified two quantitative trait loci and a single non-synonymous SNP variant, S168T, associated with levamisole resistance. The S168T variant was found to be predictive of a levamisole-resistant phenotype in all resistant isolates examined. The thesis also developed and validated several molecular diagnostic assays, including a two-step nested allele-specific PCR and loop-mediated isothermal amplification (LAMP) technologies, for the detection of the S168T variant. The results provide a foundation for establishing reliable and accurate laboratory-based molecular diagnostics for the detection of levamisole resistance in H. contortus.