Methods

General overview of the questionnaire

The information on the organisation of surveillance and control of Culex mosquitoes and Aedes invasive mosquitoes was collected through an online questionnaire constructed and implemented using EUSurvey (https://ec.europa.eu/eusurvey/home/welcome). The questionnaire addressed Culex mosquitoes (WNV vectors) and Aedes invasive mosquitoes and was divided into six parts (see Annex 1 for details):

• Part 1 asked for general information;
• Part 2 and 3 covered the vector surveillance organisation of Culex mosquitoes and Aedes invasive mosquitoes in the country:
• Part 4 and 5 covered the vector control organisation of Culex mosquitoes and Aedes invasive mosquitoes in the country;
• Part 6 concluded with an open-ended question allowing respondents to share any additional information that could help clarify how mosquito surveillance and control are organized in their country.

In the questionnaire and report we use:

• WNV vectors referring to vectors of WNV including Culex pipiens, Culex torrentium, Culex modestus, Culex perexiguus/univittatus;
• Aedes invasive mosquitoes referring to two invasive Aedes mosquitoes in Europe that have high medical importance: Aedes albopictus and Aedes aegypti.

The respondents and target countries

On 28 May 2025, the questionnaire was sent to the officially nominated national contact points for mosquito surveillance and control: ECDC Operational Contact Points (OCPs) for Entomology in 30 EU/EEA countries, the Contact Points for Operations (CPOs) in seven EU enlargement policy countries, and the UK contact point. The invitations were administered through EUSurvey, so each respondent received a personal uniquely coded email invitation providing a unique link to the online survey document. Two reminders were sent.

Terms and framework

Levels of organisation

We considered three levels in the organisation of vector surveillance and control:

1. Policy making;
2. Decision-making, planning and evaluation;
3. Operational execution.

For the policy-making level, we aimed to identify the ministry with overall responsibility and legal authority for vector surveillance or control. At level two, we focused on the organisation or agency in charge of designing, planning, and evaluating the surveillance or control strategy — defining what needs to be done, when, and where. For the third level, operational execution, we asked about the organisation or agency responsible for carrying out the daily activities related to vector surveillance or control.