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Table 1 Summary of the impact of wetland creation and management on British mosquito species, with a summary of potential for mitigation and possible nuisance/vector concern

From: Impacts of the creation, expansion and management of English wetlands on mosquito presence and abundance – developing strategies for future disease mitigation

Species Status Aquatic habitats Impact of wetland creation Impact of wetland management and possible mitigation Human nuisance biting or vector concern
Anopheles algeriensis Theobald + Fen, only in two local areas None N/A Not considered an important nuisance species or potential disease vector
Anopheles atroparvus van Thiel ++ Coastal, brackish No current evidence that newly created coastal wetlands created under managed re-alignment will be colonised by this species. N/A Causes nuisance in some coastal areas, however is of less concern than Ae. detritus. Has the potential to be a malaria vector, although the risk of local transmission is considered very low.
Anopheles claviger Meigen +++ Primarily breeds in permanent water such as ditches and pools, and generally favours heavily vegetated breeding sites. It may also be found in transient water habitats. New permanent wetlands with ditches and pools will provide new habitats for this ubiquitous species. This species will also be favoured where ditches are not regularly brinked or slubbed, or if they are left to dry out. This species can be kept in check by maintaining healthy ditches with plenty of predator competition, regular brinking of ditches to keep vegetation levels down and allow sunlight through. This species is already widespread and is not currently significantly associated with nuisance biting. Although new wetlands might create more habitat, there is no evidence to suggest that it will become problematic.
Anopheles messeae Falleroni /Anopheles daciae Nicolescu +++ Breeds primarily in open sunlit permanent freshwater pools and ditches, including in seasonally flooded grassland. New permanent wetlands with ditches and pools will provide new habitats for this ubiquitous species. This species also colonises the margins of open water in seasonally flooded grasslands, presumably the result of re-colonisation. Brinking of ditches is associated with higher abundances of immatures of this species. There is no evidence that this species is a nuisance biter; few adults are caught in mammal-lured traps or human landing catches, despite the local abundance of immatures. Although capable of transmitting malaria, owing to limited human biting this species is unlikely to be a concern.
Flooding wet grassland in late spring provides new habitats for this species.
Anopheles plumbeus Stephens ++ Tree-holes None N/A Potential malaria vector, although not previously considered to be a principal vector.
Species Status Aquatic habitats Impact of wetland creation Impact of wetland management and possible mitigation Nuisance or vector concern
Aedes vexans Meigen + Rare; flooded grassland Unknown, too rare N/A Potential vector of Rift Valley fever virus, however, this species is currently very rare in the UK.
Aedes cinereus Meigen /Aedes geminus Peus +++ Flooded fen/grassland Exploits a range of groundwater-fed summer flooded habitats, such as fens and wet grassland. How quickly they colonise new flooded grasslands is not yet known as very few immatures have been found in recently constructed wet grassland in the fens despite high adult densities in traps and resting in grazing exclosures. It is expected that colonisation will take place. High groundwater levels in the summer will dramatically enhance the density of this species where it occurs. This was proven in the Cambridgeshire study. The distribution of this species is patchy; however, where it does occur it can be a human biting nuisance. There is limited information on dispersal ranges. Owing to its anthropophagy and ornithophagy it has been implicated as a possible bridge vector of a number of arboviruses in Europe. This species will benefit from expansion of reedbeds, flooded meadows and seasonal summer flooding in open habitats.
It is possible that the timing of flooding could be planned so that the eggs are left high and dry. Winter flooding rather than spring flooding would be less favourable for this species, as immatures tend not to appear until April. Draining of flooded areas during spring would significantly reduce the survival of immatures.
Aedes geniculatus Olivier ++ Tree-holes None N/A Not considered an important nuisance species or potential disease vector
Aedes leucomelas Meigen + Rare, only in a few locations N/A N/A Too rare currently to be of concern as a nuisance or vector species
Aedes caspius Pallas +++ Coastal habitat; also flooded fen/grassland Historical records of this species are mainly coastal with a few around London. However data from the fens show that it can be very common in flooded fen and newly created wet grassland. Furthermore, it has been recorded to colonise newly created freshwater (or weakly saline) habitats in managed re-alignment sites in estuaries. Managing this species inland will be largely related to controlling water levels. High groundwater levels in summer, supplemented by precipitation leading to pooling and puddling in fen and wet grassland will provide submergence of dormant eggs. Summer flooding should be avoided Can be a nuisance species, and although not considered a primary vector of Rift Valley fever virus, it has been implicated as main vector in Egypt. Further work to establish the role of this mosquito in potential arbovirus transmission is recommended, particularly considering its potential for wet grassland colonisation.
Aedes annulipes Meigen /Aedes cantans Meigen +++ Wet woodland Not all wetland creation schemes intend to create wet woodland, however, where this does occur, consideration needs to be given to the impact of these species. High amounts of winter flooding, and the persistence of flooded woodland in spring can significantly increase the densities of these species. Woodland ditches that are regularly slubbed and re-graded are less suitable for these species. However, if they are allowed to dry out and pools form, these habitats can become suitable breeding sties. These species are serious nuisance biters of humans, and unlike other species, they bite during the day as well as at dusk. Although they are known to disperse from their habitat to find a host, there is no information on dispersal ranges. The siting of new developments near wet woodland, or the creation of new wet woodland near dwellings run the risk of exposing people to high biting rates, especially during June-August. Both species have been implicated as potential arbovirus vectors based upon their host-feeding habits (human and bird blood), however, they are not classed as a primary vector of WNV or SINV.
Aedes communis De Geer + Rare, few old records Unknown, too rare N/A Too rare currently to be of concern as a nuisance or vector species
Aedes detritus Haliday +++ Coastal, brackish; also freshwater Likely to be the principal mosquito colonising newly created coastal habitats, particularly at the spring high tide mark in isolated pools and in saline borrow ditches capturing brackish water. This species exploits saline waters left by spring high tides. These areas generally occur at the limits of existing salt-marshes, in pasture or grassland subjected to flooding at high tides, or in vegetated ditches allowed to flood during high tides. Any regular tidal flushing usually reduces the suitability of these habitats for this species. Where possible, management of spring tide waters (through closure of sluices) mitigate the negative impact of this species. However, where tides regularly leave isolated pools with no drainage then biocidal treatment is required. This species is a persistent biting nuisance and responsible for several mosquito control programmes in the UK. Although it is not considered a principal potential vector, its human and bird biting makes it a candidate vector of arboviruses. However its nuisance value alone makes it worthy of consideration and control.
Aedes dorsalis Meigen + Rare, coastal Unknown, too localised N/A Not considered to be either a nuisance or vector species. Not widely distributed.
Aedes flavescens Müller ++ Coastal, brackish Coastal marshes, although the species is not common N/A May cause nuisance biting, but not widespread, and not considered as an important potential vector.
Aedes punctor Kirby ++ Acid pools, bogs Wet woodland sites on acid soils appear to favour this species. Therefore, not all wet woodland would be suitable, however in certain parts of England this species might benefit. Winter/spring flooding of acid habitats, particularly in bog/mire/lowland moor areas can dramatically increase the numbers of this species. These habitats are naturally flooded by rainfall rather than groundwater, so management might be difficult. Dwellings close to such habitats will likely be impacted by wet winters/springs. This species is not considered a principal vector of arboviruses although it is a nuisance species in areas adjacent to its favoured breeding habitat.
Aedes rusticus Rossi +++ Wet woodland, flooded rush pasture This species would benefit from wet woodland creation and has also been found in new wet grassland habitats, particularly those dominated by rushes. Spring flooding of wet grassland could provide a habitat for this species. Although they have not been found in high numbers, spring and winter flooding of wet woodland would create suitable habitat for this species. This species is not routinely considered a potential vector, and although it does bite humans, its pest status is not as high as Ae. cantans/annulipes or Ae. detritus. However it will cause nuisance biting and will benefit from transient habitats subjected to winter/spring flooding.
Aedes sticticus Meigen + Wet woodland, very rare Unknown, too rare. It may be unlikely that such a rare species would increase dramatically with wetland creation. Timing of winter and spring flooding of wet woodland where this species occurs would be a consideration. Nuisance and vector species elsewhere in Europe, but very rare in the UK. Where this species does occur, however, it can be a serious pest.
Coquillettidia richiardii (Ficalbi) +++ Permanent: ditches, vegetated pools Newly created ditches with emergent vegetation will provide a suitable habitat for this species in time. Owing to its enigmatic life cycle, the impact of management is difficult to determine. Vegetated ditches and ponds will provide a suitable habitat, but there is no clear evidence that management would be required, although this species can be abundant in July and cause a nuisance. Can be a persistent biter after dark in high summer and is known to enter dwellings to bite. Not considered a principal arbovirus vector, but does feed on both birds and humans.
Culex modestus Ficalbi ++ Localised in coastal ditches Not routinely found in newly created wetlands, although there are a few records from wet grassland. Currently considered localised to North Kent and parts of Essex along the Thames estuary. Newly created ditches in this area would provide suitable habitat. Management of this species in permanent ditches might require biocidal control as there are currently no clear examples of the impact of water or vegetation management. However, emergent and floating vegetation appears a pre-requisite. Known to be a nuisance species where it occurs along the Thames estuary and is also considered to be a principal vector of West Nile virus elsewhere in Europe.
Culex territans Walker + Rare, permanent habitats Unknown, too under-recorded N/A Not considered an important nuisance species or potential disease vector
Culex pipiens s.l. Linnaeus /Culex torrentium Martini +++ All transient (e.g. dried ditches, flooded grasslands) and container habitats The typical biotype of Cx. pipiens and Cx. torrentium colonise transient habitats post-flooding, and will, therefore, benefit hugely from wetland creation, particularly in the early pioneer stages of wetland development. It is unclear which species dominates and further studies are required. Any nutrient rich wet grassland or nutrient rich permanent habitat (i.e. polluted ditches, post-drought ditches, or sewage treatment reedbeds) will provide aquatic habitats for this species. In aquatic habitats hostile to predators/competitors these mosquitoes will increase to large densities. It is unclear whether the molestus form of pipiens will be affected by wetland creation. Container habitats for these species are unlikely to be affected by wetland creation. For transient aquatic habitats, water-level management and precipitation will be crucial. Drying and re-wetting cycles of transient habitats, or unnatural drying of permanent habitats needs to be considered in relation to the rapid colonisation by these species. Raising water levels in wet grassland or wet fen in summer could be avoided to mitigate the impact of this species. Furthermore, permanent aquatic habitats should not be allowed to dry out. Mosquitoes associated with sewage treatment reedbeds may require biocidal control if deemed necessary, although this may not be efficient in nutrient-rich waters. Neither the typical biotype of Cx. pipiens nor Cx. torrentium are nuisance species as they almost exclusively feed on birds. They are both considered important enzootic vectors of WNV and Sindbis virus respectively. In the event of such an outbreak, management of their populations will be crucial in managing the enzootic transmission of the viruses. The molestus form is also a potential WNV vector, but is unlikely to be affected by wetland management given its predilection for underground and cloistered container habitats.
Culiseta longiareolata (Macquart) + Rare, too few records Unknown, too rare N/A N/A
Culiseta fumipennis (Stephens) + Rare, too few records Unknown, too rare N/A Not considered an important nuisance species or potential disease vector
Culiseta litorea (Shute) + Coastal, rare, too few records Unknown, too rare N/A Not considered an important nuisance species or potential disease vector
Culiseta morsitans (Theobald) ++ Permanent waters It is expected that this species would benefit from the development of permanent waters, although they have been caught in such low numbers, there is insufficient data to determine the full impact of wetland creation. There is little available information on the impact of wetland management, although vegetated ditches and reedbed that are subjected to drying and remain wet thereafter do provide a habitat for this species. It may not be necessary to control this species, but if required, certainly water level management will be crucial. Not considered an important nuisance species owing to its largely ornithophagic tendencies. However, it is a potential enzootic disease vector in Europe and they have been reported to bite humans. However, they are heavily under-recorded in adult mosquito sampling.
Culiseta alaskaensis (Ludlow) + Northern species: rare, too few records Unknown, too rare N/A Not considered an important nuisance species or potential disease vector
Culiseta annulata (Schrank) +++ Exploits a range of permanent, transient and container habitats Will benefit from a range of wetland creation schemes, such as ditches subjected to drying, wet woodland with water persisting through to late summer, nutrient-rich wet grassland in late summer and drying nutrient rich reedbeds. Wet woodland that remains wet throughout the year will provide a suitable breeding habitat for this species, which would also dominate in nutrient rich wet grassland. If this species is a problem then late summer flooding will be significant. Ditches allowed to dry and re-wet will also provide a suitable habitat. This species will also colonise polluted container habitats in urban areas, where they may be more of an issue. This species is one of the most common nuisance species in the UK, although not necessarily biting in as high numbers as other species. It is large and owing to its colouration is often confused with some much smaller invasive species. Although not a principal arbovirus vector, its ability to feed on humans and birds (in urban areas) makes it a candidate vector.
Culiseta subochrea (Edwards) + Similar to Cs. annulata, likely under-recorded. Ecology not considered distinct from Cs. annulata N/A N/A Not considered an important nuisance species or potential disease vector
Orthopodomyia pulcripalpis Rondani + Tree holes, rare N/A N/A Owing to its ornithophagic tendencies, this species is not considered an important nuisance species or a potential disease vector
  1. Key references: [5,29,32,34-46].
  2. Status: +++ widespread, ++ more localised but locally abundant, + very focal or rare.