Management of Bluetongue Outbreaks: The Practitioner's Perspective

Since the early 2000s, Bluetongue has emerged within the European Union, and a few years later, the adaptation of Palearctic Culicoides species to the transmission of BTV infections marked a major shift in the epidemiology of this disease. Since then, epidemic waves have followed one another, with new serotypes continually appearing or the emergence of new variants being observed. The characteristics of these viruses vary depending on the serotype, but certain features are now well established. First, the duration of viremia-closely linked to the lifespan of erythrocytes in the different affected species-is prolonged and plays a major role in the reactivation of outbreaks from one year to the next. Its tropism for the reproductive system and its ability to cross the placental barrier have significant consequences for fertility and offspring survival. Knowledge of Culicoides biology has also improved considerably. Moisture and the presence of organic matter are sufficient for their development. Their abundance continues to increase, and they are only minimally susceptible to the insecticides commonly used in ruminants. Control of this vector therefore appears highly challenging. One positive aspect is that they rarely enter livestock buildings, and housing animals indoors-particularly in well-ventilated facilities-can be an effective supportive measure in controlling bluetongue. Fortunately, shortly after the emergence of the first outbreaks, vaccines were developed within a very short timeframe. Vaccination therefore remains the only truly effective means of controlling these infections. The conditions for their use have improved significantly. What is still lacking is a product covering the range of circulating serotypes in order to achieve optimal protection of our herds. However, this requires sustained surveillance, particularly for the early detection of new serotypes.