Populations Of Culex Pipiens Research Articles

European Culex pipiens Populations Carry Different Strains of Wolbachia pipientis.

The mosquito Culex pipiens occurs in two ecotypes differing in their mating and overwintering behavior: pipiens mate in open environments and diapause, and molestus also mate in small spaces and is active throughout the year. Cx. pipiens carry Wolbachia endosymbionts of the wPip strain, but the frequency of infection differs between studied populations. Wolbachia infection affects the host reproductive success through cytoplasmic incompatibility. wPip Wolbachia is divided into five types, wPip I-V. The type of wPip carried varies among Cx. pipiens populations. In northern European locations different wPip types are found in the two ecotypes, whereas in southern locations, they often carry the same type, indicating differences in hybridization between ecotypes. In this study, Cx. pipiens specimens of both ecotypes were collected from Sweden and compared to specimens from Norway, England, Italy, and the Netherlands, as well as Cx. quinquefasciatus from Mali and Thailand. The abundance varied, but all specimens were infected by Wolbachia, while the tested specimens of other mosquito species were often uninfected. The wPip strains were determined through the sequence analysis of Wolbachia genes ank2 and pk1, showing that Cx. pipiens ecotypes in Scandinavia carry different wPip strains. The observed differences in wPip strains indicate that hybridization is not frequent and may contribute to barriers against hybridization of the ecotypes in Sweden and Norway.

Sensitivity of the Mosquito Culex pipiens Diptera: Culicidae towards Temephos in Southern Central Morocco

Mosquito species are responsible for the transmission of many parasitic diseases and their control leads to the phenomenon of resistance to insecticides including temephos, mostly used by hygienic services. This article reports the results of studies conducted using WHO sensitivity tests on larvae local populations of Culex pipiens collected in three lodging in the city of Marrakesh (Southern-Central, Morocco), towards temephos. Five concentrations of insecticide in addition to a control, were used to determine the DC50 and DC 90 of Culex pipiens species towards temephos. Sensitivity tests were carried out at the entomology unit and monitoring of insect sensitivity towards insecticides installed at the Regional Diagnostic Laboratory Epidemiological and Environmental Hygiene (LRDEHM), Marrakesh, under the Regional Directorate of Health of Marrakesh-Safi. The bioassay results affirmed the presence of resistance in Culex pipiens larvae towards temephos. This species has also developed similar and comparable resistance levels in the three lodgings studied, with resistance rates recorded varying between 15.2 and 128.5. This study results can be used as database for the control of mosquito resistance to insecticides at local and national level.

Host-feeding preferences and temperature shape the dynamics of West Nile virus: A mathematical model to predict the impacts of vector-host interactions and vector management on [formula omitted]

West Nile virus (WNV) is prevalent across the United States, but its transmission patterns and spatio-temporal intensity vary significantly, particularly in the Eastern United States. For instance, Chicago has long been a hotspot for WNV cases due to its high cumulative incidence of infection, with the number of cases varying considerably from year to year. The abilities of host species to maintain and disseminate WNV, along with eco-epidemiological factors that influence vector-host contact rates underlie WNV transmission potential. There is growing evidence that several vectors exhibit strong feeding preferences towards different host communities. In our research study, we construct a process based weather driven ordinary differential equation (ODE) model to understand the impact of one vector species (Culex pipiens), its preferred avian and non-preferred human hosts on the basic reproduction number (R0). In developing this WNV transmission model, we account for the feeding index, which is defined as the relative preference of the vectors for taking blood meals from a competent avian host versus a non-competent mammalian host. We also include continuous introduction of infected agents into the model during the simulations as the introduction of WNV is not a single event phenomenon. We derive an analytic form of R0 to predict the conditions under which there will be an outbreak of WNV and the relationship between the feeding index and the efficacy of adulticide is highly nonlinear. In our mechanistic model, we also demonstrate that adulticide treatments produced significant reductions in the Culex pipiens population. Sensitivity analysis demonstrates that feeding index and rate of introduction of infected agents are two important factors beside the efficacy of adulticide. We validate our model by comparing simulations to surveillance data collected for the Culex pipiens complex in Cook County, Illinois, USA. Our results reveal that the interaction between the feeding index and mosquito abatement strategy is intricate, especially considering the fluctuating temperature conditions. This induces heterogeneous transmission patterns that need to be incorporated when modelling multi-host, multi-vector transmission models.

Mutations and intron polymorphisms in voltage-gated sodium channel genes of different geographic populations of Culex pipiens pallens/Culex pipiens quinquefasciatus in China

BackgroundCulex pipiens pallens and Culex pipiens quinquefasciatus are the dominant species of Culex mosquitoes in China and important disease vectors. Long-term use of insecticides can cause mutations in the voltage-gated sodium channel (vgsc) gene of mosquitoes, but little is known about the current status and evolutionary origins of vgsc gene in different geographic populations. Therefore, this study aimed to determine the current status of vgsc genes in Cx. p. pallens and Cx. p. quinquefasciatus in China and to investigate the evolutionary inheritance of neighboring downstream introns of the vgsc gene to determine the impact of insecticides on long-term evolution.MethodsSampling was conducted from July to September 2021 in representative habitats of 22 provincial-level administrative divisions in China. Genomic DNA was extracted from 1308 mosquitoes, the IIS6 fragment of the vgsc gene on the nerve cell membrane was amplified using polymerase chain reaction, and the sequence was used to evaluate allele frequency and knockdown resistance (kdr) frequency. MEGA 11 was used to construct neighbor-joining (NJ) tree. PopART was used to build a TCS network.ResultsThere were 6 alleles and 6 genotypes at the L1014 locus, which included the wild-type alleles TTA/L and CTA/L and the mutant alleles TTT/F, TTC/F, TCT/S and TCA/S. The geographic populations with a kdr frequency less than 20.00% were mainly concentrated in the regions north of 38° N, and the geographic populations with a kdr frequency greater than 80.00% were concentrated in the regions south of 30° N. kdr frequency increased with decreasing latitude. And within the same latitude, the frequency of kdr in large cities is relatively high. Mutations were correlated with the number of introns. The mutant allele TCA/S has only one intron, the mutant allele TTT/F has three introns, and the wild-type allele TTA/L has 17 introns.ConclusionsCx. p. pallens and Cx. p. quinquefasciatus have developed resistance to insecticides in most regions of China. The neighboring downstream introns of the vgsc gene gradually decreased to one intron with the mutation of the vgsc gene. Mutations may originate from multiple mutation events rather than from a single origin, and populations lacking mutations may be genetically isolated.Graphical

Unraveling biotypes of the northern house mosquito, Culex pipiens s.l. (Diptera: Culicidae): molecular differentiation and morphometric analysis.

Geometric morphometrics was used to determine whether geographic isolation could explain differences in wing size and shape between and within continental (27°S to 41°S) and insular (Rapa Nui) populations of Culex pipiens s.s. Linnaeus and their biotypes (f. pipiens and f. molestus). Molecular protocols based on polymorphisms in the second intron of nuclear locus ace-2 (acetylcholinesterase-2) were used to differentiate Cx. pipiens s.s. from Cx. quinquefasciatus Say, and an assay based on polymorphisms in the flanking region of a microsatellite locus (CQ11) was used to identify biotypes. Culex pipiens f. molestus and hybrids shared larval habitats in all continental sites, while Cx. pipiens f. pipiens was found in 5 of the 10 sites. Only biotype molestus was found in Rapa Nui (Easter Island) Pipiens and molestus biotypes occur sympatrically in aboveground locations, and only molestus was found in the underground site (ME). Biotype molestus was dominant in rural locations and preferably anthropophilic. These results agree with the ecological descriptions previously reported for the biotypes of Cx. pipiens s.s. Procrustes ANOVA only showed differences in centroid size between biotypes in females and males and did not show significant differences in wing shape. However, we found significant differences among the geographic areas in the centroid size and wing shape of both females and males. Particularly, the population of Rapa Nui Island had shorter wings than the continental populations. The results highlight the effects of geographic and environmental processes on morphotypes in vector mosquitoes.

CDC Bottle Bioassays for Detection of Insecticide Resistance in Culex Pipiens, Aedes Albopictus, and Aedes Koreicus Collected on US Army Garrisons, Republic of Korea.

Mosquito-borne pathogens are a threat to US troops stationed in the Republic of Korea (ROK). Insecticide resistance has been reported in mosquito vectors in the ROK, highlighting the need for a sustained ROK-wide resistance surveillance program. To address this need from April 2022 until October 2022, larvae and pupae of Aedes albopictus, Ae. koreicus, and Culex pipiens were collected from US Army Garrison (USAG) Daegu (Camps Carroll and Henry), USAG Yongsan-Casey (Camp Casey), and USAG Humphreys (Camp Humphreys) and screened for resistance to insecticides using the Centers for Disease Control and Prevention (CDC) bottle bioassay. No resistance to deltamethrin or chlorpyrifos was detected in Ae. albopictus populations, but one population showed possible resistance to permethrin. Aedes koreicus populations were found to be resistant to etofenprox and permethrin with possible resistance to deltamethrin but were susceptible to chlorpyrifos. Culex pipiens populations were found to be resistant to chlorpyrifos, permethrin, and deltamethrin. Screening using CDC bottle bioassays will continue, and efforts will be made to determine the operational impact of the assay results on military installation mosquito control programs.

No association between habitat, autogeny and genetics in Moroccan Culex pipiens populations

BackgroundMosquitoes of the Culex pipiens complex are found across the globe and are the focus of many research studies. Among the temperate species C. pipiens sensu stricto (s.s.), two forms are usually described: molestus and pipiens. These two forms are indistinguishable in terms of morphology but show behavioral and physiological differences that may have consequences for their associated epidemiology. The two forms are well defined in the northern part of the species distribution, where autogeny is strictly associated with the molestus form. However, whether the two remain distinct and show the characteristic differences in behavior is less clear in North Africa, at the southern edge of their range.MethodsThe association between autogeny, as determined by ovarian dissection, and molecular forms, based on the CQ11 microsatellite marker, was studied in six Moroccan populations of C. pipiens.ResultsAn overall low prevalence of autogeny was found at three of the Moroccan regions studied, although it reached 17.5% in the Agadir population. The prevalence of form-specific CQ11 alleles was quite similar across all populations, with the molestus allele being rarer (approx. 15%), except in the Agadir population where it reached 43.3%. We found significant deficits in heterozygotes at the diagnostic CQ11 locus in three populations, but the three other populations showed no significant departure from panmixia, which is in line with the results of a retrospective analysis of the published data. More importantly, we found no association between the autogeny status and CQ11 genotypes, despite the many females analyzed.ConclusionsThere was limited evidence for two discrete forms in Morocco, where individuals carrying pipiens and molestus alleles breed and mate in the same sites and are equally likely to be capable of autogeny. These observations are discussed in the epidemiological context of Morocco, where C. pipiens is the main vector of several arboviruses.Graphical

First evidence of pyrethroid resistance in Italian populations of West Nile virus vector Culex pipiens.

Culex pipiens (Linnaeus), one of the most abundant mosquito species in Europe, plays a crucial role in the endemic transmission of West Nile virus and caused the large outbreak with >1600 human cases in 2018. Although evidence of resistance to pyrethroids has been reported for Cx. pipiens populations from Spain and Greece, resistance monitoring has been largely neglected in Italy. Herein, we investigate susceptibility of Italian Cx. pipiens populations to the pyrethroids permethrin and deltamethrin. Results from WHO‐tube‐bioassays revealed mortalities ranging from 14–54%, indicating high levels of resistance, in four out of 10 populations exposed to permethrin (0.75%) and of 63% in one of three populations exposed to deltamethrin (0.05%). Reduced susceptibility (mortality<98%) was detected in almost all other populations. A clear association is shown between the resistant phenotype and the presence of kdr‐alleles in position 1014 of the VSSC, strongly suggesting its role in reducing susceptibility. The study provides the first evidence of pyrethroid‐resistance in Italian Cx. pipiens populations and reports levels of resistance paralleled in the European region only in Turkey. This highlights the urgent need to implement insecticide‐resistance management plans to restore the efficacy of the nowadays only chemical weapon available to control arbovirus transmission in Europe.

Fitness cost of malathion resistance in Egyptian Culex pipiens populations.

The extensive use of insecticides in agriculture and public health has resulted in the rapid development of insecticide resistance in mosquito populations. Therefore, in this study, we aimed to evaluate insecticide resistance costs on the fitness of Culex pipiens. Two Cx. pipiens field populations (Beheira malathion-resistant and Gharbia malathion-susceptible) were compared to the reference (sensitive) population. The biochemical composition and expression of four genes relevant to insecticide resistance were estimated in third instar larvae. Adult survival, female fecundity and egg hatchability were also determined. As per our findings, it was found that the total protein and carbohydrate contents in Beheira malathion-resistant larvae were significantly lower than that in the reference larvae. Beheira malathion-resistant larvae had higher phenoloxidase (PO) specific activity than the reference population. In terms of the relevant genes, only cytochrome P450 (CYP6F1) expression showed elevated levels in the Gharbia malathion-susceptible population compared to the Beheira malathion-resistant population. In esterases (Estα and Estβ) and glutathione S-transferase, the tested populations did not show any significant differences. Compared to the reference mosquito population, Gharbia malathion-susceptible Cx. pipiens males exhibited significantly longer median survival. Female fecundity and hatchability showed nonsignificant differences among the populations tested. In conclusion, malathion resistance can induce lower protein and carbohydrate contents, but higher PO activity in larvae.

Modelling the temperature suitability for the risk of West Nile Virus establishment in European Culex pipiens populations.

Increases in temperature and extreme weather events due to global warming can create an environment that is beneficial to mosquito populations, changing and possibly increasing the suitable geographical range for many vector-borne diseases. West Nile Virus (WNV) is a flavivirus, maintained in a mosquito-avian host cycle that is usually asymptomatic but can cause primarily flu-like symptoms in human and equid accidental hosts. In rare circumstances, serious disease and death are possible outcomes for both humans and horses. The main European vector of WNV is the Culex pipiens mosquito. This study examines the effect of environmental temperature on WNV establishment in Europe via Culex pipiens populations through use of a basic reproduction number ( ) model. A metric of thermal suitability derived from was developed by collating thermal responses of different Culex pipiens traits and combining them through use of a next-generation matrix. WNV establishment was determined to be possible between 14°C and 34.3°C, with the optimal temperature at 23.7°C. The suitability measure was plotted against monthly average temperatures in 2020 and the number of months with high suitability mapped across Europe. The average number of suitable months for each year from 2013 to 2019 was also calculated and validated with reported equine West Nile fever cases from 2013 to 2019. The widespread thermal suitability for WNV establishment highlights the importance of European surveillance for this disease and the need for increased research into mosquito and bird distribution.

Historical samples reveal a combined role of agriculture and public-health applications in vector resistance to insecticides.

BACKGROUNDInsecticide resistance is the major threat to vector control and for the prevention of vector‐borne diseases. Because almost all insecticides used against insect vectors are or have been used in agriculture, a connection between agricultural insecticide use and resistance in insect vectors has been hypothesized. However, it is challenging to find a causal link between past agricultural use of insecticides and current resistance in vector populations without historical data series. Here we investigated the relative contribution across time of agricultural and public‐health insecticide applications in selecting for diflubenzuron (DFB) resistance in Culex pipiens populations. Using DNA sequencing, we looked for DFB resistant mutations in current and historical mosquito samples, dating back to the 1980s–1990s, when DFB was used in agriculture but not yet in mosquito control.RESULTSIn the samples collected before the introduction of DFB in vector control, we found the resistant mutation I1043M in rural regions but not any of the neighboring urban and natural areas, indicating that the selection pressure was derived by agriculture. However, after the introduction of DFB for vector control, the resistant mutations were found across all study areas showing that the initial selection from agriculture was further boosted by the selection pressure imposed by the mosquito control applications in the 2000s.CONCLUSIONSOur findings support a combined role of agricultural and public‐health use of insecticides in vector resistance across time and call for specific actions in integrated resistance management, including increased communication between agriculture and health practitioners. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Evaluation of the feeding patterns of important mosquito vector species using molecular techniques

This study investigated the feeding patterns of populations of Anopheles sacharovi, Culex tritaeniorhynchus, and Culex pipiens in the Mediterranean and Aegean regions of Turkey. Blood-fed females resting inside barns, houses, and chicken coops in the rural areas were collected between May 2017 and September 2019, and the genomic DNA from each female was isolated to determine the blood source after amplification of the mitochondrial cytochrome b gene region. Cytb results showed that out of 445 blood-fed An. sacharovi females 2 blood-fed from dogs, 9 from birds, and 434 from cows. The results also showed that all 216 blood-fed females Cx. tritaeniorhynchus captured fed from cows, 6 out of 97 Cx. pipiens females fed from horses and 91 from birds. The feeding pattern of mosquito populations can be affected by numerous factors such as sampling method, sample size, and host abundance. Although field studies on mosquito feeding patterns do not reveal the feeding preference of such vectors, they provide vital information to understanding of vector and host interactions in the research area. Moreover, these data can give an idea of possible human contact in an environment where various hosts are readily accessible to a given vector mosquito; this is important for the prevention of various human diseases caused by vector mosquitoes.

Insecticide Resistance Variation among Three Culex pipiens (Diptera: Culicidae) Populations in Egypt

Several studies have reported on insecticide resistance in mosquitoes; however, there is a lack of information about the resistance of Culex pipiens in Egypt. This study was conducted to investigate insecticide resistance status in three Cx. pipiens populations. These populations were collected from two rural breeding sites and one urban site in Egypt. Al-Beshlawy drainage canal and El-Khartoum irrigation ditch were selected to represent rural sites in Giza and Beheira governorates, respectively. One man-made ground hole was selected in Tanta, Gharbia Governorate, as an urban breeding site. Insecticide residues were analysed in water samples collected from the three breeding sites. Four insecticides, malathion chlorpyrifos, deltamethrin and fipronil, were tested against Cx. pipiens third-instar larvae of three field populations and one insecticide-susceptible (reference) population. Four insecticide residues and one additive (piperonyl butoxide) were detected; only malathion and piperonyl butoxide concentrations exhibited significant differences among all breeding sites. The level of malathion residue in the Giza breeding site was significantly higher than those in the Gharbia and Beheira breeding sites. According to the lethal concentrations (LC50) of the applied insecticides, the susceptibility of Cx. pipiens third-instar larvae to different insecticides demonstrated the order fipronil > chlorpyrifos > deltamethrin > malathion. Variations in the percentage mortality of Cx. pipiens were observed following malathion application between the Gharbia population and with both Giza and Beheira populations. Culex pipiens populations exhibited low resistance to most tested insecticides; however, the populations of Giza and Beheira exhibited moderate resistance to malathion. The variation in the resistance of Cx. pipiens populations to malathion could provide new information about the intraspecific variation among some mosquito populations in Egypt.

Evolution of Resistance to Chlorpyrifos and lambda-cyhalothrin Insecticides against Culex Pipiens Populations

The susceptibility of Culex pipiens larvae collected from Al-Asher of Ramadan, Sharkia Governorate, to chlorpyrifos and lambda-cyhalothrin insecticides was investigated for 20 successive generations. For multiple generations, the instar larvae of field parent strain were exposed to LC30 of the previous generation to that insecticide. Total protein and lipids content as well as activities of detoxifying enzymes (i.e. acetylcholinesterase, non-specific esterases and glutathione-S-transferase) were determined in each generation. Bioassay tests showed that larval Cx. pipiens developed 144.31 and 761.85-fold resistance to chlorpyrifos and lambda-cyhalothrin, respectively, after 20 successive generations of selected pressure. Total protein content declined while total lipids increased gradually with proceeded the generations. In general, the activities of detoxifying enzymes increased gradually with raising generation numbers which indicate that the increased resistance is likely to be associated with the increased activity of target and metabolic enzyme systems.

Inter-annual variability of the effects of intrinsic and extrinsic drivers affecting West Nile virus vector Culex pipiens population dynamics in northeastern Italy

BackgroundVector-borne infectious diseases (VBDs) represent a major public health concern worldwide. Among VBDs, West Nile virus (WNV) showed an increasingly wider spread in temperate regions of Europe, including Italy. During the last decade, WNV outbreaks have been recurrently reported in mosquitoes, horses, wild birds, and humans, showing great variability in the temporal and spatial distribution pattern. Due to the complexity of the environment–host–vector–pathogen interaction and the incomplete understanding of the epidemiological pattern of the disease, WNV occurrences can be difficult to predict. The analyses of ecological drivers responsible for the earlier WNV reactivation and transmission are pivotal; in particular, variations in the vector population dynamics may represent a key point of the recent success of WNV and, more in general, of the VBDs.MethodsWe investigated the variations of Culex pipiens population abundance using environmental, climatic and trapping data obtained over nine years (2010 to 2018) through the WNV entomological surveillance programme implemented in northeastern Italy. An information theoretic approach (IT-AICc) and model-averaging algorithms were implemented to examine the relationship between the seasonal mosquito population growth rates and both intrinsic (e.g. intraspecific competition) and extrinsic (e.g. environmental and climatic variables) predictors, to identify the most significant combinations of variables outlining the Cx. pipiens population dynamics.ResultsPopulation abundance (proxy for intraspecific competition) and length of daylight were the predominant factors regulating the mosquito population dynamics; however, other drivers encompassing environmental and climatic variables also had a significant impact, although sometimes counterintuitive and not univocal. The analyses of the single-year datasets, and the comparison with the results obtained from the overall model (all data available from 2010 to 2018), highlighted remarkable differences in coefficients magnitude, sign and significance. These outcomes indicate that different combinations of factors might have distinctive, and sometimes divergent, effects on mosquito population dynamics.ConclusionsA more realistic acquaintance of the intrinsic and extrinsic mechanisms of mosquito population fluctuations in relation to continuous changes in environmental and climatic conditions is paramount to properly reinforce VBDs risk-based surveillance activities, to plan targeted density control measures and to implement effective early detection programmes.

Phenotypic insecticide resistance in arbovirus mosquito vectors in Catalonia and its capital Barcelona (Spain).

A range of mosquito species that belong to the Culicidae family are responsible for the worldwide transmission of infectious arboviral diseases such as dengue fever, Zika, West Nile fever and Chikungunya fever. Spain is at risk of arbovirus outbreaks, as various arboviral diseases are frequently introduced and it has established competent vector populations. Autochthonous human cases of West Nile virus have been reported infrequently since 2004, and since October 2018 three autochthonous human case of dengue fever have been confirmed. In response to an outbreak of any arboviral disease, space spraying or fogging will be implemented to control adult mosquito populations. To ensure adulticiding is cost-effective, the insecticide susceptibility status of vectors throughout Catalonia, an autonomous region in north-eastern Spain, was assessed through standardized WHO tube and CDC bottle bioassays. All Culex pipiens populations tested were resistant to at least one of the pyrethroids tested, whereas Aedes albopictus populations were susceptible to all pyrethroids tested. More detailed studies on the Cx. pipiens populations from the Barcelona area (the capital and largest city of Catalonia) revealed resistance to all four classes of public health insecticides available (pyrethroids, carbamates, organophosphates and organochlorides). All Ae. albopictus populations were susceptible to those classes, except for one of the tests performed with pirimiphos-methyl (an organophosphate). Pyrethroids are currently the first line chemical class to be used in space spray operations in response to an outbreak of an arboviral disease. While pyrethroids can be effective in reducing Ae. albopictus populations, this class may not be effective to control Cx. pipiens populations.

Identification of Eilat virus and prevalence of infection among Culex pipiens L. populations, Morocco, 2016

Eilat virus (EILV) is described as one of the few alphaviruses restricted to insects. We report the record of a nearly-complete sequence of an alphavirus genome showing 95% identity with EILV during a metagenomic analysis performed on 1488 unblood-fed females and 1076 larvae of the mosquito Culex pipiens captured in Rabat (Morocco). Genetic distance and phylogenetic analyses placed the EILV-Morocco as a variant of EILV. The observed infection rates in both larvae and adults suggested an active circulation of the virus in Rabat and its maintenance in the environment either through vertical transmission or through horizontal infection of larvae in breeding sites. This is the first report of EILV out of Israel and in Culex pipiens populations.

Influence of Temperature Change on the Growth and Susceptibility of the Common House Mosquito, &amp;lt;i&amp;gt;Culex pipiens&amp;lt;/i&amp;gt; in Egypt to Some Insecticides

By transmitting major human diseases, mosquito species represent a serious threat worldwide in terms of public health. Most vector control programmes aiming to control life-threatening mosquitoes rely on the use of chemical insecticides. For the reason that only a few insecticides are used for public health, maintaining the efficacy of control programmes mostly relies on resistance management strategies. Development of such strategies requires understanding the factors influencing resistance together with characterizing the mechanisms involved. In this context, the present study aims to update current knowledge about the effect of temperature on the mosquito Culex pipiens population response to chemical insecticides. The results demonstrated that alteration of the temperature significantly affects Cx. pipiens populations. High temperature (25, 30°C) resulted in high survival rate (90, 95% respectively); while at temperature 20°C the survival rate was 80%. Egg hatching percentage was 95% after 24 h, at temperature 30°C and 50% after 24h, 50% after 48h at 25°C; however at 20°C egg hatching percentage was 100% after 48 h. In case of Cx. pipiens larvae that were reared under various temperatures pupated on day 5, 9 and 12 at 30°C, 25°C and 20°C, respectively. At high temperature 30°C, females emerged before males. On the other hand resistance of all Cx. pipiens populations to the selected chemical insecticides decreased with raising temperature. The obtained results also showed that there was significant change in acetylcholinesterase and glutathione -S-transferase level in both larvae and adult due to temperature changing. These results indicate that temperature is an important parameter that must be considered during the application of chemical assays or control of Cx. pipiens populations.

Wolbachia diversity and cytoplasmic incompatibility patterns in Culex pipiens populations in Turkey

BackgroundWolbachia are maternally transmitted bacteria that can manipulate their hosts’ reproduction causing cytoplasmic incompatibility (CI). CI is a sperm-egg incompatibility resulting in embryonic death. Due to this sterilising effect on mosquitoes, Wolbachia are considered for vector control strategies. Important vectors for arboviruses, filarial nematodes and avian malaria, mosquitoes of Culex pipiens complex are suitable for Wolbachia-based vector control. They are infected with Wolbachia wPip strains belonging to five genetically distinct groups (wPip-I to V) within the Wolbachia B supergroup. CI properties of wPip strongly correlate with this genetic diversity: mosquitoes infected with wPip strains from a different wPip group are more likely to be incompatible with each other. Turkey is a critical spot for vector-borne diseases due to its unique geographical position as a natural bridge between Asia, Europe and Africa. However, general wPip diversity, distribution and CI patterns in natural Cx. pipiens (s.l.) populations in the region are unknown. In this study, we first identified wPip diversity in Turkish Cx. pipiens (s.l.) populations, by assigning them to one of the five groups within wPip (wPip-Ito V). We further investigated CI properties between different wPip strains from this region.ResultsWe showed a wPip fixation in Cx. pipiens (s.l.) populations in Turkey by analysing 753 samples from 59 sampling sites. Three wPip groups were detected in the region: wPip-I, wPip-II and wPip-IV. The most dominant group was wPip-II. While wPip-IV was restricted to only two locations, wPip-I and wPip-II had wider distributions. Individuals infected with wPip-II were found co-existing with individuals infected with wPip-I or wPip-IV in some sampling sites. Two mosquito isofemale lines harbouring either a wPip-I or a wPip-II strain were established from a population in northwestern Turkey. Reciprocal crosses between these lines showed that they were fully compatible with each other but bidirectionally incompatible with wPip-IV Istanbul infected line.ConclusionOur findings reveal a high diversity of wPip and CI properties in Cx. pipiens (s.l.) populations in Turkey. Knowledge on naturally occurring CI patterns caused by wPip diversity in Turkey might be useful for Cx. pipiens (s.l.) control in the region.

Insecticide Resistance Development in Culex Pipiens Population under Selection Pressures with Temephos

Insecticide Resistance Development in Culex Pipiens Population under Selection Pressures with Temephos