Bluetongue is a notifiable disease of ruminants affecting both cattle and sheep.
It is caused by infection with the bluetongue virus (BTV). There are a number of different strains or serotypes of the virus, and the virus affecting France in 2016 and of concern to the UK is serotype 8 (BTV-8).
The main route of transmission of disease is via the Culicoides biting midge. Climate change and warmer winters has allowed wider distribution of these midges allowing bluetongue in recent years to extend into most of Europe and the UK.
Infection is transmitted when biting midges are most active between May and October. Originally winter was seen as a ‘vector free’ period, however the virus is now known to be able to overwinter in both the midges and the host ruminant. BTV-8 can also pass from dam to offspring via the placenta.
Whilst BTV-8 did not enter the UK in 2016, there is a risk for 2017. Cases continued to be reported in France throughout 2016 and into 2017, with 406 new outbreaks reported in December 2016, and 154 in January 2017. As temperatures rise, and midge activity increases, the risk of disease spreading in France, and therefore the risk to the UK increases.