Towards the penside detection of triclabendazole efficacy against Fasciola hepatica parasites of livestock

Abstract

Fasciolosis is an increasing global concern to animal welfare, agricultural productivity, public health and food security. Environmental changes are contributing to Fasciola hepatica expansion, which are set to worsen by predicted climatic trends. Independent emergences of anthelmintic resistant parasite populations worldwide are also threatening the sustainability of the few available flukicides, whilst exacerbating the economic impacts of fasciolosis on food production. Inappropriate flukicide applications, particularly for triclabendazole (TCBZ) as the drug of choice, will only continue to increase the risk and incidences of treatment failure and spread of anthelmintic-resistant parasite populations, which is particularly devastating to TCBZ-mediated parasite control in the continuing absence of a commercial vaccine. With these current prognoses, tools for to identify anthelmintic efficacy require improvement to sustain flukicidal activities and effective infection management. Furthermore, the development of new biomarker candidates for future penside application will lead to an easy and useful test for the farmer, veterinarian and researcher in pursuing the goal of monitoring infection, drug efficacy and ultimately parasite elimination. In this thesis, a representative profile of adult stage F. hepatica procathepsin L zymogens is dissected. Proteomic and immunologic methods identified the presence of zymogens within in vitro cultured adult excretory/secretory products, and a new polyclonal antibody raised to a recombinant mutant procathepsin L1A antigen was utilised to identify prominent immunodominance of the inhibitor (pro-) peptides in intact native procathepsins. Additionally, key phenotypic and proteomic characteristics were identified between a mixed wild type population and compared with a new confirmed TCBZ-resistant liver fluke strain isolated in Kilmarnock (Scotland, United Kingdom), providing knowledge towards the study of proteins potentially involved in the TCBZ resistance phenotype. In addition, following on from previous findings, a panel of biomarkers associated with TCBZ-sulphoxide (TCBZ-SO) challenge were bioinformatically characterised, cloned and recombinantly expressed, where possible, for use in pilot diagnostic tests. Hereon, the potential diagnostic utility of several candidates was found, including the procathepsin L1A antigen and counterpart polyclonal antibodies. In summary, this thesis has elucidated new findings about cathepsin protease antigens and has made progress towards the analysis and production of several new biomarkers, which are of potential significant value for future F. hepatica control in livestock

Date of Award	2019
Original language	English
Awarding Institution	Aberystwyth University
Supervisor	Peter Brophy (Supervisor) & Russ Morphew (Supervisor)