Using the basic reproduction ratio to quantify transmission and identify data gaps for epizootic haemorrhagic disease virus

Epizootic haemorrhagic disease virus (EHDV) is an arbovirus transmitted by <i>Culicoides</i> biting midges that has recently emerged in Europe. Here, the basic reproduction ratio (<i>R</i> ₀) was used to quantify the transmission of EHDV and its dependence on temperature for cattle and deer. Using data from the published literature the parameters needed to calculate <i>R</i> ₀ were estimated with Bayesian methods to incorporate uncertainty in the calculations. The Sobol method of sensitivity analysis was used to determine the parameters having the greatest influence on <i>R</i> ₀ and, hence, to identify important data gaps. Depending on the strain, the maximum <i>R</i> ₀ for EHDV varied from 0.7 to 2.5 in cattle and 1.3 to 4.3 in deer. The maximum <i>R</i> ₀ occurred at temperatures between 22 and 25°C, while the lowest temperature at which <i>R</i> 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 the vector- to- host ratio as the most important parameters influencing <i>R</i> 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.