Liver fluke (Fasciola hepatica) is a major parasitic disease of cattle causing liver damage, production losses, and significant welfare harm, with control complicated by emerging triclabendazole resistance.
Liver fluke causes a spectrum of welfare harm from catastrophic acute mortality to the slow, insidious deterioration of chronic disease. Acute fasciolosis from massive autumn challenge kills cattle that appeared healthy days before — haemorrhagic liver destruction is rapid and the clinical course to death spans only 24-72 hours in severe cases. Chronic fluke is subtler but affects far more animals: cattle with significant fluke burdens are chronically immunosuppressed, anaemic, and in negative energy balance, with reduced appetite, poor body condition, and inferior response to other disease challenges. The triclabendazole resistance crisis has significant welfare implications because no alternative flukicide is effective against the immature stages that cause the most acute pathology. Resistance management requires combination strategies: strategic dosing with alternative products for adult fluke, accurate faecal egg count monitoring to guide treatment timing, and pasture management to reduce snail habitat through drainage and fencing of wet areas.