Spatial and temporal risk assessment of Epizootic Hemorrhagic Disease Virus introduction in Europe: A comparative analysis of trade and wind dispersal pathways

Epizootic Hemorrhagic Disease Virus (EHDV), transmitted by Culicoides biting midges, is a threat for the livestock sector in Europe. A quantitative risk assessment model framework was developed to assess the risk of EHDV introduction in Europe, through wind dispersal of Culicoides and trade in live animals. The model integrates meteorological data, wind trajectories, vector biology, livestock trade information and considers disease dynamic in infected sources as well as disease susceptibility in potential destinations. The full risk zone combining both pathways encompassed 42 different countries with 30 in Europe and 12 outside, each with highly-variable levels of risk. The highest risk countries included three sources: France, Spain, Italy, and one disease-free, Germany. The period of highest risk corresponded to the favourable period of Culicoides activity, between May and October. Risk estimates were markedly higher for the wind pathway, spanning 20 countries mainly in Western Europe, compared to the trade pathway that covered 40 countries, including distant Eastern ones, like Romania. The Pathway Risk Ratio (PRR) showed a higher wind pathway contribution in most countries where both pathways were present. France was the primary source country, regardless of the pathway. Alternative scenarios suggested that limiting the source area to 2024 infected areas or considering long trade history could reduce the list of at-risk countries. However, underreporting or reducing PCR testing at borders could increase risk estimates. This research aims to guide disease risk management measures by providing insights into the risk of Culicoides-borne disease extension.