Using the basic reproduction ratio to quantify transmission and identify data gaps for epizootic haemorrhagic disease, an emerging vector-borne disease in Europe

Epizootic haemorrhagic disease virus (EHDV) is an arbovirus transmitted by Culicoides biting midges that has recently emerged in Europe. In this paper, the basic reproduction ratio ( R ₀ ) was used to quantify the transmission of EHDV and its dependence on temperature for the most important livestock and wildlife hosts, cattle and deer, respectively. Using data from the published literature the parameters needed to calculate R ₀ were estimated with Bayesian methods to incorporate uncertainty in the calculations. Sensitivity analysis, specifically the Sobol method, was used to determine the most influential parameters determining the magnitude of R ₀ and, hence, to identify important data gaps. Results show that R ₀ for EHDV depends on strain, with maximum R ₀ varying from 0.7 to 2.5 in cattle and 1.3 to 4.3 in deer. The maximum R ₀ occurred at temperatures between 22 and 25 °C, while the lowest temperature at which R ₀ exceeded one was between 16 and 20 °C. The sensitivity analysis identified the threshold temperature for virus replication, the probability of transmission from host to vector and vector to host ratio as the most important parameters influencing R ₀ . Furthermore, there are only limited data on EHDV in European deer species and on transmission in wildlife and at the livestock/wildlife interface. These data gaps should be the focus of future research.