Evaluation of the role of environmental factors on the transmission of West Nile Virus in the European Union and Mediterranean countries

Abstract

Purpose: West Nile virus (WNV) is one of the most widely distributed flaviviruses worldwide, and it is considered an endemic and emerging pathogen in different areas of Europe and the Mediterranean. Mosquitoes of the genus Culex spp. transmit it, and its main vertebrate hosts are birds, although it can occasionally infect mammals, including humans. Different environmental factors, mainly climatic, can influence the distribution and transmission of the virus, through its effects on vector and/or host populations. The objective of this study is to carry out a systematic review to determine the environmental factors associated with the distribution of vectors and the transmission of WNV in the European Union (EU) and Mediterranean countries. Methods & Materials: Systematic peer review of indexed articles in PubMed, Scopus, Embase and CENTRAL published between 2000 and 2020. We selected studies on WNV and its vector Culex spp. carried out in the EU and Mediterranean countries in the last two decades. The search included terms referring to climatic factors such as temperature, precipitation, humidity, drought and flood events, as well as other environmental factors such as the altitude of the study area and changes in habitat or land use. Results: We registered the protocol of the systematic review in PROSPERO. The search, selection and inclusion of studies, as well as data extraction, has been carried out. Preliminary results are as follows: 63 included studies, 32% conducted in Italy. Culex spp is studied in 43% of the studies, in 40% host animals (mainly birds and horses) and in 21% humans, among others. In 56% and 29% of the studies, a significant relationship was observed between changes in temperature and precipitation patterns and the epidemiology of WNV, respectively. Conclusion: The epidemiology of WNV seems to be related to climatic factors; mainly temperature and precipitation are associated with changes in the transmission dynamics of WNV in the study area. To improve the surveillance and control of this emerging disease, it would be necessary to monitor these changes as well.