Mosquitoes (Diptera: Culicidae) of Poland: An Update of Species Diversity and Current Challenges

Simple Summary This article presents the current state of knowledge of mosquito species occurring in Poland. The current work lists the presence of 51 species of mosquitoes from five genera: Aedes, Anopheles, Coquillettidia, Culiseta, and Culex, compared to 47 species recorded in works published before 2000. Aspects of the ecology and biology of the Polish mosquito fauna, with particular emphasis on newly recorded species, are discussed. Abstract This article presents the current state of knowledge of mosquito species (Diptera: Culicidae) occurring in Poland. In comparison to the most recently published checklists (1999 and 2007), which listed 47 mosquito species, four species (Aedes japonicus, Anopheles daciae, Anopheles hyrcanus, and Anopheles petragnani) are added to the Polish fauna. Our new checklist of Polish mosquito fauna includes 51 species of mosquitoes from five genera: Aedes (30), Anopheles (8), Coquillettidia (1), Culiseta (7), and Culex (5). Aspects of the ecology and biology of the Polish mosquito fauna, with particular emphasis on newly recorded species, are discussed.


Introduction
Mosquitoes (Diptera: Culicidae) are among the most important vectors of public health importance.Their enormous vector potential for infectious and potentially lethal pathogens and parasites makes them the most important blood-feeding arthropods in the world.Climate and land-use changes, globalization, and intensive transportation of humans and goods influence the spread of mosquitoes and pathogens, which results in expanding emerging or re-emerging diseases around the world [1][2][3].Knowledge of the presence and current range of mosquito species occurrence in a given area is therefore crucial to assessing the potential risk to human and animal health.This paper aims to present an up-to-date state of knowledge of the mosquito fauna in Poland.The previous checklist of mosquito species occurring in Poland was published at the end of the 20th century by Kubica-Biernat [4], who listed in her publication 47 mosquito species reported from 223 identifiable sites in Poland.The same list of 47 species was also given by Wegner in 2007 [5].

Current Knowledge
The knowledge of the distribution of Culicidae in Poland still remains fragmentary because regular monitoring of the presence of mosquito species is limited to only a few areas.Additionally, some data on mosquito species occurrence are included in papers concerning biocontrol [6][7][8], evening activity of synanthropic species [9], factors influencing the distribution of floodwater mosquito eggs [8], and the detection of pathogens [10][11][12][13].
Figure 1.NUTS 3 territorial units in Poland, where work on the species composition of mosquitoes was carried out between the years 2000-2023 (dark grey), light grey areas-units where Ae. japonicus was found in 2023 [29,30].
In recent years, records of mosquito species newly found in Poland have been published.Species not mentioned in the review by Kubica-Biernat [4] and described in original papers published after 2000 include three species of Anopheles: An. hyrcanus [20], An. daciae [19], and An.petragnani [30].Additionally, in 2023, Ae. japonicus was found in southern Poland [29,30].
The unequivocal evidence of An. daciaeʹs presence in Poland was shown for the first time by Rydzanicz et al. [19].They collected adult mosquitoes between July and September 2015 in the Wrocław area and applied a rapid PCR-RFLP assay on specimens of the Maculipennis Complex, resulting in the unambiguous identification of An. daciae, An. messeae, and An.maculipennis sensu stricto (s.s.).The potential occurrence of An. daciae was also suggested earlier by Kubica-Biernat and Kowalska-Ulczyńska [31] in north and north-eastern Poland (the voivodeships of Pomorskie, Warmińsko-Mazurskie, and Podlaskie).Here, An. maculipennis s.s. and the taxon An. messeae/daciae were identified among over a thousand mosquito specimens of the Maculipennis Complex.Anopheles messeae and An.daciae are morphologically and genetically almost similar, which challenges species identification.Both species prefer stagnant water bodies with unpolluted water on the banks of rivers and lakes with abundant submerged vegetation, ponds, and ditches, as well as larger water bodies in floodplains (Table 4).Anopheles daciae was originally distinguished from An. messeae based on five nucleotide substitutions in In recent years, records of mosquito species newly found in Poland have been published.Species not mentioned in the review by Kubica-Biernat [4] and described in original papers published after 2000 include three species of Anopheles: An. hyrcanus [20], An. daciae [19], and An.petragnani [30].Additionally, in 2023, Ae. japonicus was found in southern Poland [29,30].
The unequivocal evidence of An. daciae's presence in Poland was shown for the first time by Rydzanicz et al. [19].They collected adult mosquitoes between July and September 2015 in the Wrocław area and applied a rapid PCR-RFLP assay on specimens of the Maculipennis Complex, resulting in the unambiguous identification of An. daciae, An. messeae, and An.maculipennis sensu stricto (s.s.).The potential occurrence of An. daciae was also suggested earlier by Kubica-Biernat and Kowalska-Ulczy ńska [31] in north and northeastern Poland (the voivodeships of Pomorskie, Warmi ńsko-Mazurskie, and Podlaskie).Here, An. maculipennis s.s. and the taxon An. messeae/daciae were identified among over a thousand mosquito specimens of the Maculipennis Complex.Anopheles messeae and An.daciae are morphologically and genetically almost similar, which challenges species identification.Both species prefer stagnant water bodies with unpolluted water on the banks of rivers and lakes with abundant submerged vegetation, ponds, and ditches, as well as larger water bodies in floodplains (Table 4).Anopheles daciae was originally distinguished from An. messeae based on five nucleotide substitutions in its rDNA internal transcribed spacer 2 [32].Anopheles daciae occurs in Eurasia, including countries neighboring Poland.
The first report on the appearance of An. hyrcanus in Poland comes from Wrocław (southwest Poland), where this species was identified among mosquitoes collected in the years 2019-2020 [20].The identification of a well-established population of An. hyrcanus in Wrocław [20] suggests an increase in the range of this species because the described place of its occurrence is the most northern localization in Europe.Anopheles hyrcanus sensu lato is considered to be a species complex that includes about 30 species in the Palearctic and Oriental regions [42,43].In the Wrocław area, An. hyrcanus s.s. was discovered in wetlands containing numerous canals and permanent reservoirs situated in the valleys of the Odra and Oława rivers.This region is a natural area covered with riparian forests where white willow (Salix alba) and white poplar (Populus alba) are the dominant species.It is also recognized as a protected region under the European network of Natura 2000 areas and is covered by a sanitary protection zone [14].The banks of canals, lakes, and wet areas are covered with marsh vegetation-reeds and sedge communities with common sedge (Carex fusca), sharp sedge (Carex gracilis), common calamus (Acorus calamus), and common reed (Phragmites australis).The preference of habitat for An.hyrcanus in Wrocław is in line with data presented by Becker et al. [3], who described that the larvae of An. hyrcanus prefer to develop in more or less clear, sun-exposed water bodies with rich vegetation.The larvae of An. hyrcanus mosquitoes can be found in permanent reservoirs and slowly flowing channels that have rich riparian plants (Table 4).The presence of An. hyrcanus was documented in many European countries, including France [44], Croatia, Hungary, Austria [45], Czechia, Slovakia, Russia [43,46,47], Romania, Serbia [48], Italy [49], and Spain [44].
Anopheles petragnani was very recently found for the first time in Poland in the Kielce Upland [30].Larvae were collected in artificial water reservoirs (metal wadies) in allotment gardens in Kielce.The species is a sibling species of Anopheles claviger s.s., whose morphological differentiation is only possible on the basis of subtle differences in the structure of eggs and larvae [50,51].PCR methods are used to unambiguously distinguish these species [52].Anopheles petragnani is distributed in the western Mediterranean [3], whose larvae tolerate higher water temperatures than An.claviger s.s.[50].It is a zoophilic species capable of autogenous reproduction.In the past, it was sporadically recorded in southern Europe (Portugal, Spain, southern France, Italy, and North Africa) and more recently in Germany [51] and Luxembourg [53].It does not play any role in pathogen transmission [3].
Aedes japonicus was found in the southern part of Poland during a capacity building program organized by ECDC [29,30].All positive records are from southern regions close to the border of Czechia and Slovakia.In Czechia Ae. japonicus was found in 2021, close to the Czech-German and Czech-Austrian border [54] and recently in the north of the country [30].In Slovakia, the first records of Ae. japonicus were found in 2020 in a few places localized at border crossings with Austria and Hungary and in the urban and rural zones of five major cities [55].In Germany, Ae. japonicus was found for the first time in 2008 in the south German federal state of Baden-Wuerttemberg [56][57][58] and is now widespread over Germany [59].Aedes japonicus is a species native to Asia (Korea, Japan, Taiwan, southern China, and south-eastern Siberia), and it is recognized as the third invasive mosquito species reported in Europe, after Ae. albopictus and Ae.aegypti [2].
The mosquito species Ae. rossicus appears here for the first time at the species rank in a Polish checklist, while it was listed as a subspecies of Ae. esoensis in the review of Kubica-Biernat [4].Indeed, this taxon is nowadays recognized as a valid species [60].In recent two decades, the presence of Ae. rossicus was noted in Warsaw (Wilanów) in a study that listed 33 mosquito species (26 species recorded as larvae and 30 as adults) recorded in the years 2001-2009 in material that comprised more than 11,000 individuals, including larvae and adults of Ae. rossicus [23].Furthermore, Ae. rossicus was recorded in Warsaw for the first time.Aedes rossicus is a floodwater mosquito that lays eggs on the ground that is frequently flooded; it prefers small temporary water bodies, inundation areas of river valleys, and swampy woodlands with acid waters (Table 4).The presence of Ae. rossicus was also confirmed in other European countries, including Sweden [61], France [62], Germany [63], Czechia [64], and Russia [60,65].
Among the 47 mosquito species listed by Kubica-Biernat [4], during the last two decades, the presence of 8 species was not confirmed: Ae. detritus, Ae. hexodontus, Ae. nigripes, Ae. pionips, Ae. pullatus, An. atroparvus, Cs. fumipennis, and Cs.subochrea (Tables 1-3).The occurrence of Ae. geminus was recently confirmed [20] in Lower Silesia [30].The smaller number of mosquito species identified in recent years is most likely the result of the lack of monitoring in most areas of Poland and might not be related to the disappearance of species.It is worth emphasizing that the mosquito fauna in Poland includes species with different habitat preferences (Table 4).For development, they prefer different types of water bodies (e.g., clear or highly polluted); some species use inland brackish marshes and other snow-melt ponds [3,8,66,67].They can hatch in wild and synanthropic areas, in permanent and temporary water bodies, and in different types of water bodies along rivers, including flooded areas in river valleys.Species also differ in their development time (spring-most of them, or summer), number of generations (mono-or polycyclic), as well as host feeding preferences (anthropo-or zoophilic), and vector potential.Thus, mosquito fauna studies should cover diverse environments and different geographical areas to be comprehensive.

Medical Importance
Among the mosquito species found in Poland, 40% are potential or documented vectors of pathogens (Table 4) [2,20,26,68].These species can transmit malaria plasmodia (currently in Poland, only imported malaria cases are reported), arboviruses, or zoonotic parasites.Among them, mosquito species recorded in Poland, Ae. vexans and Cx.pipiens s.l. are of particular importance because they are widespread throughout the country and have documented vector roles.They are multi-voltine species that can thrive in large numbers under favorable conditions.
Aedes vexans is a floodwater species common in the Holarctic region, showing high abundance in Eastern Europe [3].It thrives in a variety of habitats, particularly in rural areas, and is commonly found in floodplains of river valleys.Like many floodplain mosquitoes, Ae. vexans prefer to lay eggs on the ground of temporary or semi-permanent pools that are prone to seasonal flooding.Their eggs enter a state of diapause, which allows them to survive longer periods of drought before hatching in large numbers after floods.Aedes vexans has an extremely short aquatic phase in summer (6-7 days), which leads to a rapid increase in population density.Adult females are known for aggressive biting behavior, showing little host specificity among mammals and humans.This feature is important for the potential transmission of pathogens.In regions such as North America and Europe, Ae. vexans transmits a variety of arboviruses, including West Nile virus (WNV), snow hare virus (SSHV), Jamestown Canyon virus (JCV), Tahyna virus (TAHV), and Batai virus (BATV).In Africa, Ae. vexans is considered one of the main vectors of the Rift Valley fever virus (RVFV).Experimental studies have confirmed its ability to transmit RVFV in both African and American populations [68,69].
From a medical point of view, the emergence of invasive mosquito species may be of particular importance because some of them play a key role in the spread of many mosquito-borne diseases worldwide [2].In Europe, the most important invasive mosquito species include: Ae. albopictus, Ae. aegypti, Ae. japonicus, and Ae.koreicus.In Poland, so far only the presence of Ae. japonicus has been confirmed; however, the presence of other invasive species (Ae.albopictus, Ae. koreicus) is increasingly noted in countries bordering Poland [74][75][76][77].Aedes japonicus, native to Japan, Korea, Taiwan, southern China, and parts of Russia, did spread to North America and Central Europe.Aedes japonicus shows early emergence and a longer activity season compared to other invasive species, as well as the ability to disperse over long distances and to withstand lower temperatures.However, it cannot tolerate aquatic habitats exceeding 30 • C, limiting its spread in Southern Europe.Similarly to Ae. albopictus, it produces cold-resistant eggs and feeds on mammals primarily.It adapts well to various environments, including urban areas with artificial containers, but prefers vegetation-rich suburban or rural settings and agricultural environments.Its minimal habitat requirements and tolerance to organic matter facilitate its spread even in eutrophic and polluted water basins.Aedes japonicus has been linked to outbreaks of the Japanese encephalitis virus (JEV) in Asia and to La Crosse virus and WNV cycles in North America [59].Its presence in new areas has led to an increase in its own abundance and the displacement or reduction in native mosquitoes, which may affect mosquito diversity as well as the epidemiology of associated arboviruses.Although not very widespread yet, there is concern that the range and abundance of this species will expand in Poland [78].
The southern part of Poland appears to be suitable for the emergence of further invasive mosquito species due to higher average temperatures than in other areas of the country and the proximity of invasive mosquito populations in neighboring countries.Therefore, it is necessary to continuously monitor and survey mosquito species composition along known transmission routes-motorways, airports, etc. Understanding the biology and ecology of native and invasive mosquito species is essential for developing strategies to prevent and control the spread of mosquito-borne diseases.Furthermore, the rapid process of globalization, coupled with climate change, which affects mosquito populations, highlights the need for capacities for applying effective vector control measures to mitigate pathogen transmission.

Conclusions
The current checklist of mosquito species in Poland includes 51 species of five genera: Aedes, Anopheles, Coquillettidia, Culiseta, and Culex.It is worth emphasizing that two first records (An.daciae and An.hyrcanus) were located in Wrocław-an area under regular mosquito monitoring [19,20].In addition, Ae. japonicus was found to be well established in southern Poland in seven voivodships, in 2023, after remaining undetected for several years, probably due to the lack of earlier monitoring in these areas [30].Surveys conducted in 2023 also resulted in the identification of An. petragnani in central Poland, in the Kielce Upland [30].Both species were found in the country for the first time ever.Considering the ecological diversity of mosquito species occurring in Poland, and the limited area of mosquito fauna monitoring conducted in recent years, the accurate knowledge of the distribution of individual mosquito species in Poland requires further, comprehensive research to be conducted throughout the country.Research conducted during the last few decades focused mainly on urban areas.It would be worthwhile in the future to extend monitoring and research of the mosquito fauna to rural and natural areas.Moreover, due to the emergence of invasive species such as Ae.japonicus, Ae. albopictus, and Ae.koreicus in countries bordering Poland [74][75][76][77], it seems necessary to continue to track changes at the border of their range of occurrence and further investigate the possible occurrence of invasive mosquito species in Poland.
Globalization and climate change around the world and in Europe will favor the further spread of mosquitoes to new areas.Invasive species such as Ae.albopictus are a good example.The emergence of additional mosquito species raises challenges in terms of eliminating introduced specimens or suppressing established populations over larger areas.Additionally, invasive species are often competent vectors of disease pathogens that can emerge subsequently.Preventing or controlling mosquito-borne diseases will be a major challenge for the health services of many countries, not least for Poland, which has little mosquito control experience and capacity and is unprepared for facing mosquito-borne diseases.

Figure 1 .
Figure 1.NUTS 3 territorial units in Poland, where work on the species composition of mosquitoes was carried out between the years 2000-2023 (dark grey), light grey areas-units where Ae. japonicus was found in 2023 [29,30].

Table 1 .
The occurrence of Aedes mosquitoes in Poland.

Table 2 .
The occurrence of Anopheles mosquitoes in Poland.Species identified as An.messeae/daciae; ** species identified as Anopheles claviger/Anopheles petragnani; # the complex of several species not distinguished in many works. *

Table 3 .
The occurrence of Coquillettidia, Culiseta, and Culex mosquitoes in Poland.