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Functions and diagnostic applications of liver fluke microRNAs Caoimhe Herron (24169194) PUREID: 616435227 miRNA Fasciola hepatica fasciolosis extracellular vesicles fluke diagnostics Phylum Platyhelminthes represents a group of highly divergent species many of which cause major detrimental impacts on both human and animal health globally. In terms of veterinary health, they can cause death in young animals. In cattle, this can cause a loss in production through reduced weight gain and milk production. These platyhelminth species include Fasciola hepatica or liver fluke which cause a remerging disease in some areas and a newly emerging disease in others. Diagnostic methods predominantly rely on faecal microscopy which is relatively insensitive and cannot identify pre-patent juvenile parasites. In most cases, flukicide treatments are administered to entire herds when infection is detected or suspected. The resulting over-use of anthelmintics has led to resistance against most available drugs. This project investigated microRNAs (miRNAs) as a source of novel diagnostics and therapeutics for F. hepatica. These miRNAs are often secreted into host serum within extracellular vesicles (EVs), which are mediators of miRNA interaction within host immune cells. Extracellular miRNAs are recognised as potential diagnostic biomarkers since they are stable within host biofluids and correlate with disease states. Some miRNAs secreted by other helminth parasites have been shown to impact host immune function to promote parasite survival, making them appealing therapeutic targets.<br><br>This thesis expands upon the miRNome of F. hepatica and reveals issues with the current state of the phylum Platyhelminthes miRNome, with duplicated sequences being identified under different names. Work included in this thesis addressed miRNA naming in phylum Platyhelminthes to make future work more straightforward. In addition, this thesis expanded the known complement of miRNAs in F. hepatica by identifying novel miRNAs through small RNA-sequencing, and demonstrating differential expression amongst different life stages. Targeting of these parasite-specific miRNAs may reveal host-parasite interactions.<br><br>Follow-up analyses included in this thesis investigated whether the most the most abundant miRNAs in adult fluke EVs were detectable in sera from F. hepatica-infected sheep. One of these, Fhe-miR-750, was found across acute and chronic disease timepoints suggesting promise as a diagnostic biomarker. In addition, EV dynamics were investigated for the first time across an experimentally induced F. hepatica infection in sheep. This quantitative analysis revealed a peak of putative vesicles at the 4-weeks post infection timepoint suggesting either fluke secretion into the host or an elevation of host EVs in response to fluke infection. This thesis improves the current knowledge of the miRNome within phylum Platyhelminthes. It also expands and improves our understanding of the F. hepatica miRNome and fluke-host interactions. This is an important step in identifying vitally needed new targets for therapeutics and diagnostics for fasciolosis.<br><br> 2026-10-01T16:32:08Z Text Thesis 10.17034/32640330.v1 https://figshare.com/articles/thesis/Functions_and_diagnostic_applications_of_liver_fluke_microRNAs/32640330 All Rights Reserved