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?

• The impact of climatic and land use changes on the snail vector and transmission of infection.
• Role of temperature and moisture on egg development
• Survival of the snail and various parasite stages in the environment.
• How are parasites in refugia influenced under different environmental and management conditions?

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

Described in sections 1, 4, 11, 12.
Environmental correlates are well described but only for certain regions, e.g. in the UK, Ireland, and Belgium. Need to extend studies beyond these areas and transform understanding into predictive approaches that can be fairly applied under new and future conditions.
Use of environmental management to support fluke control is widely advocated but limited by practical obstacles (e.g.
incompatibility between economic factors / subsidy structures and alternative land uses) and other more powerful drivers of decisions at government and farm levels (e.g. flood control, agri environment schemes). A major challenge is to conduct theoretical and field-based investigations into how integration of topographical, environmental and management factors can effectively reduce impacts of liver fluke and reduce reliance on failing chemical control.

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

• Field studies are large, long, complicated and expensive and require appropriate levels of commitment from funders and stakeholders.
• Theoretical approaches are not a substitute for field data but could help to identify clearly testable hypotheses and select the most effective study designs.
• The potentially broad influence of interacting factors means that it would be very difficult to control for all the variables in such studies.
• Taking advantage of interventions driven for reasons other than fluke control, e.g. change in land management as a result of altered policy, might provide routes to test interventions against fluke.

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

Testing alternative strategies would require better tools for quantifying metacercariae load on pastures.

Existing knowledge including successes and failures

Existing risk predictions are based almost entirely on climatic drivers of infection (temperature and precipitation) and other environmental factors are neglected. Several have been shown to relate to infection levels (e.g. topography, soil type), but only in statistical and broader spatial models. There is a need to advance beyond this level of understanding such that changes in environmental drivers of infection can be used effectively to attenuate fluke transmission, or negative impact of environmental changes on disease risk anticipated and actions taken to protect animal health.