Among the 14 countries that do not conduct Cu/ex control, the reasons mentioned for not implementing control are: the mosquito species group is not present (Iceland), it is not a public or veterinary health problem (7/14 countries), we do not have reliable mosquito control options (Portugal), or there is a lack of resources to implement mosquito control (Bosnia and Herzegovina, Kosovo and Portugal). One country (Slovenia) reported that control activities are only considered as an emergency response, triggered by the detection of a disease outbreak, rather than as part of an ongoing, proactive public health strategy. One country (the Netherlands) stated that it does not yet have evidence of reliable mosquito control options in the event of an outbreak and clarified that it only has some evidence on the reduction of Cu/ex populations in urban areas with active Aedes albopictus eradication activities. Whereas various larvices have been registered for use by pest management professionals, this is not yet the case for adulticides against Cu/ex, and this will require approval from the responsible Dutch governmental agency.
Figure 2. Overview of the countries that implement vector surveillance and control of Culex mosquitoes that are WNV vectors
For most of the countries (10/17 countries) that have implemented Cu/ex vector surveillance, WNV is a public or veterinary health problem which informs the national response (9/10 countries) (Table). Other reasons provided for the implementation of WNV vector surveillance are: surveillance is part of the early detection of flaviviruses, tracking changes of vector population due to climate and land use changes, relevant for animal health (horses, domestic birds), as part of the insecticide resistance monitoring, out of research interest (project based), or to support risk assessment requested by the Ministry.