The importance of vector abundance and seasonality

Abundance, seasonality, mosquitoes, sandflies, biting midges and ticks
First published in EFSA Supporting Publications
12 November 2018
2 October 2018
External Scientific Report

The present document has been produced and adopted by the bodies identified above as authors. This task has been carried out exclusively by the authors in the context of a contract between the European Food Safety Authority and the authors, awarded following a tender procedure. The present document is published complying with the transparency principle to which the Authority is subject. It may not be considered as an output adopted by the Authority. The European Food Safety Authority reserves its rights, view and position as regards the issues addressed and the conclusions reached in the present document, without prejudice to the rights of the authors.


This joint ECDC‐EFSA report assesses whether vector count data (abundance) and the way these change throughout the year (seasonality) can provide useful information about vector‐borne diseases 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 vector group (mosquitoes, sandflies, midges and ticks), lists the gaps in the sampling coverage and provides guidance for prioritising the acquisition of information. Knowing where vector species occur is crucial for the assessment of vector‐borne disease risk. Collecting abundance and seasonality data through field sampling is, however, more expensive and time consuming than collecting most other vector‐related data. The importance of abundance and seasonality data varies considerably according to the vector group and the epidemiological concept of interest. Epidemiological concepts of tick‐borne disease are less informed by abundance data than are those of the other vector groups, and presence/absence data of ticks may be sufficient in conjunction with other factors. Abundance data are generally considered relevant to pathogen establishment and transmission but less useful to inform early warning systems, estimates of the likelihood of pathogen persistence and –for sandflies, midges and ticks– to inform targeting of control measures. The conclusions on this report were based on VectorNet group discussions, field sampling studies, and review of both peer‐reviewed and grey literature. VectorNet is a European network for gathering and sharing data on the geographic distribution of arthropod vectors of disease agents affecting humans and livestock. Finally, the report notes that any form of extensive vector sampling depends not only on resources to fund the sampling programmes, but also on the availability of entomologists that have the skills to implement surveillance and monitoring programmes.

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