Tick-borne fever (TBF), caused by Anaplasma phagocytophilum transmitted by the sheep tick Ixodes ricinus, causes fever, immunosuppression, and reproductive losses in sheep in tick-endemic areas.
Tick-borne fever causes acute suffering through severe fever, depression, and the systemic effects of bacterial invasion of neutrophils. Affected sheep stop eating, separate from the flock, and show signs of significant discomfort. The welfare impact is compounded by immunosuppression lasting 2-4 weeks after the febrile period — during this window, secondary infections including fatal louping-ill encephalitis cause additional suffering. Ewes infected in early pregnancy frequently abort, representing significant suffering and reproductive loss. Farmers in endemic hill areas should have a tick management protocol that includes monitoring tick burdens, strategic acaricide treatment before high-risk periods, and standing orders for oxytetracycline treatment of febrile animals. Tick-naive animals — including introduced breeding stock or animals moved from tick-free farms — require particular attention, as they lack partial immunity and suffer the most severe disease.