Sheep Liver Fluke: Welfare and Control

Liver fluke infection is a major cause of sheep mortality and welfare harm worldwide. Changing climate patterns are expanding its range, requiring updated control strategies.

Key Facts

Liver fluke (Fasciola hepatica) infects sheep through contaminated pasture, particularly in wet conditions
The parasite requires a mud snail (Galba truncatula) intermediate host that thrives in wet, muddy habitats
Acute fluke disease (from massive immature fluke burdens) causes sudden death with little prior warning
Chronic fluke disease causes bottle jaw, weight loss, reduced fleece quality, and poor reproductive performance
Climate change is expanding fluke risk to previously unaffected upland areas across the UK and Europe
Resistance to triclabendazole (the main treatment) is now widespread in parts of the UK and Ireland

Welfare Considerations

Liver fluke causes significant welfare harm at multiple stages — acute disease causes sudden death after a period of severe liver destruction; chronic disease causes prolonged debility, pain, and reduced quality of life. Subclinical infection suppresses immune function, allowing other diseases to establish more easily. Resistance to triclabendazole means that in some regions, effective treatment options are limited, threatening flocks with progressive welfare harm. Integrated control strategies (drainage, snail habitat management, targeted treatment, and strategic use of different flukicide classes) are essential.

What You Can Do

Work with a vet to develop a fluke control plan based on local risk assessment and resistance data
Drain wet areas and fence off muddy drainage channels where snail populations thrive
Use fecal egg count reduction tests to check flukicide efficacy and detect resistance early
Support rotational grazing strategies that reduce continuous fluke contamination of pastures