Roadmap for the development of control strategies for liver fluke

What are we trying to achieve and why? What is the problem we are trying to solve?

• What is the importance of different host species including wildlife reservoirs, management and animal movement on gene flow between populations?
• How do different parasite genotypes vary in virulence and other biological traits, including response to host defences and therapeutics, performance in intermediate hosts, etc.?
• Do susceptible and resistant parasite genotypes differ in biological fitness

What are the scientific and technological challenges (knowledge gaps needing to be addressed)?

In contrast to their application in viral and bacterial infections, population genetic studies are an underexploited approach to unravel host-parasite co-evolution and there are no agreed methods and limited neutral genetic markers to conduct such studies.

What approaches could/should be taken to address the research question?

Developing the methods for population genetic structure studies for F. hepatica and applying them to isolates collected from across the world. Including isolates from wildlife and combining with established livestock movement databases and standardized questionnaires on farm management.

What else needs to be done before we can solve this need?

• Deeper knowledge of fluke genetics, especially for genes relevant to resistance.
• Improved genetic map, better annotated genome resources, better understanding of heterogeneity and redundancy within key gene families.
• Population and distribution data for relevant wildlife species and ways of measuring movement within and between farms and its implications for gene flow.

Existing knowledge including successes and failures

The population genetic structure of a parasite species has important implications for evolutionary processes such as
adaptation to host defences and the development of AR. We still know surprisingly little about the population genetic structure of most species of parasitic helminths, in a livestock context. There is also widespread livestock movement at both national and international scale. Movement is normally undertaken with little or no monitoring or effective quarantine measures against helminth parasites. Wildlife, such as rabbits, hares, deer and others, may act as reservoirs of certain helminth infections for livestock. On the one hand, this may contribute to the parasite
population in refugia but, on the other act to disseminate parasites and resistant genotypes. Population genetic studies represent an as yet under-exploited approach to unravelling the scale and drivers of parasite movements between farms.