Atmospheric Dispersion Modelling in Response to Bluetongue Outbreaks on the Near Continent

Abstract: Bluetongue is an infectious, non-contagious, vector-borne disease of ruminants, particularly sheep and cattle, caused by the bluetongue virus (BTV). Infection with BTV can cause abortion, stillbirth, birth abnormalities and reduced milk production. Mortality in cattle is usually low, but mortality in sheep can exceed 50%. In addition to the direct effects of bluetongue disease, it is also economically important due to the export restrictions and surveillance measures introduced to limit its spread. BTV is transmitted by various species of Culicoides biting midges, which are active in warm conditions and can carry the disease hundreds of kilometres when blown on the wind.

On 3rd September 2023, BTV was detected on farms in the central Netherlands, and subsequently identified as the BTV-3 the serotype, which had previously never been seen in Europe other than on the Mediterranean islands of Sicily and Sardinia. BTV-3 spread quickly, due to a warm early autumn and the ruminant population being immunologically naïve, so that by the end of October nearly 4000 farms throughout the Netherlands had confirmed BTV-3 cases, with the excess mortality in sheep estimated at over 37,000 animals.

In this presentation we will illustrate the ways in which the NAME atmospheric dispersion model was used to contribute to risk assessments, identifying regions of the UK most at risk from airborne incursions of BTV-3—carrying midges from the Netherlands. This led to the detection of a BTV positive cattle in Kent in early November 2023, the first airborne incursion of BTV to the UK since 2007, and further NAME simulations contributed to the Defra response to BTV cases detected in the UK.

Biography: Will is in the Atmospheric Dispersion & Air Quality team at the Met Office, working on the development and deployment of NAME-based forecasting systems for biological dispersion applications. These typically involve the spread of windborne pests and pathogens of relevance to global and national food security, requiring both close collaboration with domain experts and communication of results directly to government stakeholders. Recent work includes leading on the forecasting of i) desert locust migration in Africa; ii) wheat rust fungal spore spread in South Asia; and iii) risk assessment of airborne incursions of bluetongue disease from the continent to the UK.