Systematic literature review on the geographic distribution of rift valley fever vectors in Europe and the neighbouring countries of the Mediterranean Basin

Abstract

Although Rift Valley Fever (RVF) is mainly affecting large parts of sub-Saharan Africa, there is an increased concern that this vector-borne disease could be introduced into the Europe. Transmission of this viral zoonosis can occur through various pathways of which infected mosquitoes are one of the most important. Several species have been suspected as putative vector, mainly of the genus Aedes and Culex. The possible occurrence and/or distribution of at least nine of these species in the Mediterranean Basin are not fully clarified though crucial for the development of a risk assessment for the Europe. To acquire this information a stepwise approach was adopted. Firstly, a systematic literature review was initiated to compile all existing presence/absence data of these eight species in the proposed countries from different data sources. Relevant environmental and eco-climatic data needed to model the distribution and potential areas of spread were also extracted. All information was used to generate predicted presence maps using Random Classification Forest. Outputs were validated using accuracy assessment and compared to existing maps. For six of the nine species sufficient data was obtained from a large range of publications, for Culex tritaenorhynchus and Culex antennatus only few publications and/or scattered data was available. Despite lacking data, predicted presence maps were created for all species with an adequately high accuracy with Area Under the Receiver Operating Curve (AUC) values ranging from 0.905 to 0.995. The created maps highlight however specific regions in Europe and countries around the Mediterranean Basin that seems to be highly suitable for the occurrence of putative vectors of RVF. With these maps, one of the first prerequisite to advance the restricted knowledge on vector ecology and distribution is fulfilled.