3 Jul 20265 min read

England and Wales get their first nationwide Culex mosquito map

For the first time, England and Wales have a peer-reviewed, climate-aware nationwide map of where their *Culex* mosquitoes actually live. The 2026 *BMC Public Health* paper from Liverpool, UKHSA and APHA models *Cx. p. pipiens*, *Cx. p. molestus* and *Cx. torrentium* separately, and shows that the eastern and estuarine half of England carries the highest vector density. The work is the load-bearing baseline for WNV and USUV preparedness in the UK.

Mosticare Editorial
Last updated Ā· 3 Jul 2026
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For the first time, England and Wales have a nationwide, climate-aware map of where their Culex mosquitoes actually live. A peer-reviewed study published on 23 June 2026 in BMC Public Health, led by a team at the University of Liverpool and the UK Health Security Agency, draws on two field seasons of stratified active mosquito surveillance, 2023 as the baseline, 2024 as the adaptive follow-up, and uses generalised linear mixed-effects models (GLMMs) to predict the abundance of three Culex taxa across the territory. The work is the load-bearing baseline for any serious conversation about West Nile virus (WNV) and Usutu virus (USUV) preparedness in the UK.

The three taxa and why they matter

Culex pipiens sensu lato is the common European house mosquito and the principal WNV vector in Europe. Culex pipiens in its strict sense, however, is two biologically distinct forms, Cx. pipiens pipiens, the bird-feeding rural and suburban form, and Cx. pipiens molestus, the mammal-feeding (including human-biting) form that thrives in underground and urban habitats, plus the sibling species Culex torrentium, which is morphologically near-identical to Cx. pipiens but ecologically and behaviourally distinct. The three taxa are not interchangeable as WNV vectors; the molestus form in particular is the one that bites humans and bridges the rural bird cycle into the human population.

The Liverpool team's analytical step, modelling each taxon separately rather than pooling Cx. pipiens s.l., is the methodological point that the paper turns on. Earlier work, the authors argue, has tended to treat Cx. pipiens s.l. as a single entity, which dilutes the public-health signal.

What the map shows

The species distribution models predict higher Cx. p. pipiens abundance than the other two taxa across most of England. Regions of high abundance occurred across most of England, particularly in the east and in estuarine areas. The lowest abundances clustered in the northwest of England, in most of Wales, in the North Pennines and in the Yorkshire Dales. Higher elevation areas, the authors note, "showed markedly lower abundances" for Cx. p. pipiens.

The geographic pattern is consistent with what field entomologists have long suspected anecdotally, and what the 2023-24 stratified surveillance programme now confirms systematically. The eastern and estuarine signal aligns with the established Cx. pipiens preference for nutrient-rich standing water associated with lowland agricultural drainage, river floodplains and coastal wetlands. The northwestern and upland signal aligns with the cooler, wetter upland climate that suppresses Cx. pipiens population density.

What drives each form

The environmental drivers differ between the two Cx. pipiens forms in ways that matter for forecasting.

Culex p. pipiens abundance is strongly associated with precipitation-related covariates, wetter conditions support the surface-water larval habitats that the bird-feeding rural form prefers.

Culex p. molestus, by contrast, is mostly influenced by temperature covariates. The molestus form is adapted to warmer urban and underground environments, metro systems, large building basements, utility conduits, and warmer ambient conditions support year-round breeding and a longer adult-biting season.

The practical implication, the authors argue, is that "the two forms" of Cx. pipiens should be modelled separately in any risk analysis or distribution study, pooling them risks underestimating human-biting exposure in warm urban areas and overestimating rural exposure where Cx. p. pipiens dominates but does not bite humans preferentially.

Why this matters for West Nile and Usutu

The reason the paper exists at all is the northward expansion of West Nile virus in Europe over the last decade, including the first WNV-positive mosquito detections in the Netherlands, Germany and the UK over the same window. Usutu virus, a related flavivirus maintained in a bird, mosquito cycle with occasional spillover to humans, has been detected in birds and mosquitoes across northern Europe and is now considered endemic in parts of Germany, Belgium, the Netherlands and France. The UK has not yet recorded an autochthonous WNV or USUV transmission event in humans, but the vector is present in significant density across the eastern half of England and the vector competence is established.

The preparedness gap, until now, has been the absence of a baseline map that says where the vector actually is and at what density. Targeted surveillance, risk communication to clinicians, blood-donor deferral frameworks, and equine and avian surveillance all require an underlying distribution map. The Liverpool team's work is the first peer-reviewed nationwide map of that baseline for England and Wales.

The funding and the institutional frame

The work was funded under grant BB/X018172/1 from UK Research and Innovation and the Department for Environment, Food and Rural Affairs (Defra), the UK's joint biosecurity and public-health funding line for vector-borne disease preparedness. The author team spans the University of Liverpool (the senior author, Luigi Sedda), the UK Health Security Agency's Medical Entomology group, the Animal and Plant Health Agency, and several regional public-health partners. The publication in BMC Public Health, open-access, public-health-facing rather than pure-entomology-facing, signals an institutional intent to put the baseline data into operational use.

What to watch next

The 2025 field season's data, when published, will be the first test of the adaptive-surveillance methodology and will refine the GLMM maps with a third year's data. The Liverpool team and the UKHSA Medical Entomology group are also the natural partners for any future UK deployment of WNV or USUV genomic surveillance in mosquitoes, the European literature is moving towards routine mosquito-pool PCR for flavivirus detection, and the UK has not yet committed to that layer.

For readers in the eastern and estuarine half of England, particularly East Anglia, the Humber estuary, the Thames estuary, and the Kent and Essex coastal belt, the message is not panic but awareness. The vector is there, in density, in summer. Standard personal-protection measures (long sleeves at dusk, DEET- or picaridin-based repellent, treated netting in rural and peri-urban accommodation, empty standing water weekly from gardens) reduce bite risk against Cx. pipiens to the same extent as against any other European mosquito.

For clinicians and public-health teams in the same areas, the paper is the signal that the preparedness conversation has moved from hypothetical to operational. The first autochthonous UK WNV or USUV detection, when it comes, will land in the geography this map already describes.

What we know

Sources cited

  1. de Klerk JN, Haziqah-Rashid A, Widlake E, Wilson R, Pilgrim J, Vaux AGC, Tanianis-Hughes J, Delnicka A, Jealous AS, Abbott AJ, Haines C, Johnston CJ, Miller F, Sherlock K, Bursali F, Gandy S, Biddlecombe SM, Medlock JM, Blagrove MSC, Baylis M, Sedda L. Climate-based forecasting from national Culex mosquito surveillance to support West Nile and Usutu virus preparedness in England and Wales. BMC Public Health 2026 Jun 23 (online ahead of print). DOI: 10.1186/s12889-026-28033-5. PMID 42337508. https://pubmed.ncbi.nlm.nih.gov/42337508/
  2. UK Research and Innovation / Department for Environment, Food and Rural Affairs (UKRI/Defra), grant BB/X018172/1, vector-borne disease preparedness programme. https://www.ukri.org/
  3. UK Health Security Agency, Medical Entomology group, research and surveillance portal. https://www.gov.uk/government/collections/medical-entomology