Tick-borne fever (TBF), caused by Anaplasma phagocytophilum transmitted by Ixodes ricinus ticks, is a significant welfare and production concern in sheep on upland pastures across Europe.
Tick-borne fever causes significant acute welfare impacts through high fever, immune suppression, and the consequent vulnerability to multiple secondary infections. Pregnant ewes experiencing TBF may abort, while affected lambs may develop tick pyaemia — causing severe joint pain, abscess formation, and paralysis that often necessitates euthanasia. The immune suppression caused by TBF means that affected animals may simultaneously suffer from multiple concurrent diseases. Farmers managing sheep on tick-endemic pastures must balance the welfare cost of tick exposure against the practical limitations of acaricide use, including product availability, resistance concerns, and chemical residues in meat and milk. Integrated tick management combining strategic treatment, pasture management, and monitoring is the recommended approach.