Defining the genetic diversity of free living and intramolluscan stages of fasciola hepatica (PhD)

The Challenge

Fasciola hepatica, the common liver fluke, is an important cause of morbidity and mortality in ruminants worldwide. Effects of sub-clinical infection on growth rate and milk yield is estimated to cost the UK cattle industry up to £300 million annually. Currently control of fasciolosis is based on anthelmintic drugs including triclabendazole, however drug resistance is increasingly being reported throughout the UK. Previously we have identified that liver fluke populations infecting sheep and cattle in the UK are highly variable (genetically diverse).The aim of this project is to better understand how genetic diversity is maintained in liver fluke populations in order to appreciate how drug resistance emerges and spreads.

The Project

The project has three specific objectives:

1. Can the infective F.hepatica stage (metacercariae) remain viable on stored forage (e.g. after the ensiling process)?
2. How does the prevalence of infection in the mud snail intermediate host, G.truncatula, influence the genetic diversity of F.hepatica populations?
3. How long can metacercariae survive on pasture and how does this impact on genetic diversity of liver fluke populations infecting sheep and cattle?

By highlighting the contribution different stages of the liver fluke life cycle make to parasite diversity, the project will provide a deeper understanding of the emergence and spread of triclabendazole resistance. The outcomes of the project will identify what risk feeding stored forage poses to liver fluke infection in livestock (e.g. silage, hay and haylage) and provide information on the distribution of infective metacercariae on pasture.  This will lead to advice for farmers on how best to reduce livestock exposure to liver fluke infection on farm and in the longer term it will enable the design of evidence-based control programmes to mitigate the spread of drug resistance.

The Student

Bethan John