Bluetongue is a viral disease of ruminants transmitted by Culicoides biting midges, causing significant suffering in affected sheep and presenting increasing challenges to European flocks as the disease's geographic range expands northward with changing climate conditions.
Disease Welfare Impact
Bluetongue causes severe clinical disease in sheep. Affected sheep develop fever, facial oedema, conjunctivitis, nasal discharge, and the characteristic cyanotic (blue) tongue and coronary band hyperaemia that give the disease its name. Severe cases involve sloughing of the tongue epithelium, oral ulcers, lameness from coronary band lesions, and respiratory distress. Mortality rates in highly susceptible sheep populations can reach 30-50% in severe outbreaks.
The welfare cost of clinical bluetongue is substantial: affected sheep experience acute and prolonged pain from oral lesions, lameness, and systemic illness. High fever causes profound depression and anorexia. Recovery, where it occurs, is slow — weeks to months — during which welfare is compromised. The suffering caused by bluetongue makes prevention through vaccination a clear welfare priority in at-risk populations.
Bluetongue in Northern Europe: Expanding Range
Historically limited to southern Europe and the Mediterranean, bluetongue has expanded northward with the establishment of Culicoides imicola (the primary vector) in new areas and the adaptation of northern Culicoides species as vectors. Bluetongue serotype 3 spread through northwest Europe in 2023-24, affecting the Netherlands, Belgium, Germany, and reaching the UK, causing significant welfare losses in sheep flocks unprepared for the disease.
Vaccination: The Primary Welfare Intervention
Effective vaccines against bluetongue serotypes 1, 2, 3, 4, and 8 are available. Vaccination of sheep in at-risk areas before the vector season is the most effective welfare intervention. The rapid geographic expansion of bluetongue in Europe has required emergency vaccine procurement and accelerated vaccination programs in newly affected countries. Welfare-focused policy frameworks prioritize vaccination access and affordability to protect sheep welfare at national scale.
Midge Control and Welfare
Reducing midge biting pressure through insecticide treatment of sheep and housing during peak midge activity provides partial protection where vaccination is unavailable or incomplete. These measures also benefit sheep welfare by reducing the distress of biting midge attack independent of disease transmission, which can cause significant behavioral disturbance during peak midge seasons in affected areas.