The importance of vector abundance and seasonality: results from an expert consultation

Knowing where vector species occur is crucial for the assessment of vector-borne disease risk. This was recognised by EFSA and ECDC, who, over the period 2014–2018, funded VectorNet, a European network for gathering and sharing data on the geographic distribution of arthropod vectors of disease agents affecting humans and livestock. The VectorNet database contains distribution data on four vector groups: mosquitoes, sandflies, Culicoides midges and ticks. The majority of these data are on vector presence or absence, but since 2015, count data from a number of targeted field surveys, which used standardised sampling methods and that were funded through the network, have been added. The objective of this document is to describe an assessment, for each vector group, of whether vector count data (abundance) and the way these change throughout the year (seasonality) can provide useful information about epidemiological processes of interest, and therefore, whether resources should be devoted to collecting such data. The document also summarises what measures of abundance and seasonality can be collected for each group, what gaps remain in the sampling coverage and what can be done to fill these gaps. Furthermore, it provides guidance for prioritising the acquisition of information.