Population Genetics of Culex tritaeniorhynchus (Diptera: Culicidae) in Türkiye.

PURPOSE: Mosquitoes are important vectors of pathogens that can affect humans and animals. Culex tritaeniorhynchus is an important vector of arboviruses such as Japanese encephalitis virus, West Nile virus among various human and animal communities. These diseases are of major public health concern and can have huge economic and health burdens in prevalent countries. Although populations of this important mosquito species have been detected in the Mediterranean and Aegean regions of Türkiye; little is known about its population structure. Our study is to examine the population genetics and genetic composition of Cx. tritaeniorhynchus mosquitoes collected from several localities using cytochrome oxidase subunit I (COI) and the NADH dehydrogenase subunit 5 genes (ND5). This is the first extensive study of Cx. tritaeniorhynchus in the mainland Türkiye with sampling spanning many of provinces. METHODS: In this study, DNA extraction, amplification of mitochondrial COI and ND5 genes and population genetic analyses were performed on ten geographic populations of Culex tritaeniorhynchus in the Aegean and Mediterranean region of Türkiye. RESULTS: Between 2019 and 2020, 96 samples were collected from 10 geographic populations in the Aegean and Mediterranean regions; they were molecularly analyzed and 139 sequences (50 sequence for COI and 89 sequence for ND5) were used to determine the population structure and genetic diversity. For ND5 gene region, the samples produced 24 haplotypes derived from 15 variable sites and for COI gene region, 43 haplotypes were derived from 17 variable sites. The haplotype for both gene regions was higher than nucleotide diversity. Haplotype phylogeny revealed two groups present in all populations. AMOVA test results show that the geographical populations were the same for all gene regions. Results suggest that Cx. tritaeniorhynchus is a native population in Türkiye, the species is progressing towards speciation and there is no genetic differentiation between provinces and regions. CONCLUSION: This study provides useful information on the molecular identifcation and genetic diversity of Cx. tritaeniorhynchus; these results are important to improve mosquito control programs.

[Comparison of the microbiota diversity between autogenous and anautogenous Culex pipiens pallens].

OBJECTIVE: To investigate the microbiota composition and diversity between autogenous and anautogenous Culex pipiens pallens, so as to provide insights into unraveling the pathogenesis of autogeny in Cx. pipiens pallens. METHODS: Autogenous and anautogenous adult Cx. pipiens pallens samples were collected at 25 ℃, and the hypervariable regions of the microbial 16S ribosomal RNA (16S rRNA) gene was sequenced on the Illumina NovaSeq 6000 sequencing platform. The microbiota abundance and diversity were evaluated using the alpha diversity index, and the difference in the microbiota structure was examined using the beta diversity index. The microbiota with significant differences in the abundance between autogenous and anautogenous adult Cx. pipiens pallens samples was identified using the linear discriminant analysis effect size (LEfSe). RESULTS: The microbiota in autogenous and anautogenous Cx. pipiens pallens samples belonged to 18 phyla, 28 classes, 70 orders, 113 families, and 170 genera, and the dominant phyla included Proteobacteria, Bacteroidetes, and so on. At the genus level, Wolbachia was a common dominant genus, and the relative abundance was (77.6 ± 11.3)% in autogenous Cx. pipiens pallens samples and (47.5 ± 8.5)% in anautogenous mosquito samples, while Faecalibaculum (0.4% ± 0.1%), Dubosiella (0.5% ± 0.0%) and Massilia (0.5% ± 0.1%) were specific species in autogenous Cx. pipiens pallens samples. Alpha diversity analysis showed that higher Chao1 index and ACE index in autogenous Cx. pipiens pallens samples than in anautogenous samples (both P values > 0.05), and lower Shannon index (P > 0.05) and Simpson index (P < 0.05) in autogenous Cx. pipiens pallens samples than in anautogenous samples. LEfSe analysis showed a total of 48 significantly different taxa between autogenous and anautogenous Cx. pipiens pallens samples (all P values < 0.05). CONCLUSIONS: There is a significant difference in the microbiota diversity between autogenous and anautogenous Cx. pipiens pallens.

Mosquitoes in urban green spaces and cemeteries in northern Spain.

BACKGROUND: Mosquitoes inhabiting urban green spaces and cemeteries in Europe represent a crucial facet of public health concern and contribute to the ecological balance. As urbanization intensifies, these areas increasingly serve as vital habitats for various mosquito species, fostering breeding grounds and increasing the risk of disease transmission. METHODS: A study was conducted in the three main cities (inland, coastal, and estuarine) of the Basque Country, northern Spain, to investigate the species composition, abundance, dynamic populations, larval habitats, and host preferences of mosquitoes in urban green spaces and cemeteries. CDC traps and dipping were used to collect mosquitoes for 2 years (2019-2020). RESULTS: A total of 21 mosquito species were identified, with Culex pipiens s.l. being the most abundant and widespread. The three ecological forms of Cx. pipiens were found, and Cx. pipiens pipiens was the most common in both green areas and cemeteries. Morphological identification together with molecular tools identified 65 COI sequences with high homology. The highest species richness was found in the inland city, followed by the coastal city and the estuarine city. Mosquito abundance was significantly higher in green areas compared to cemeteries and in the coastal and estuarine cities compared to the inland city. The investigation of larval breeding sites highlighted the dominance of Cx. pipiens s.l., particularly in semi-artificial ponds, diverse water-holding containers (tyres and buckets) and drainage systems in green areas; in cemeteries, most of the larvae were found in flowerpots and funerary urns. Seasonal activity exhibited variable peaks in mosquito abundance in the different cities, with a notable increase in July or August. Additionally, blood meal analysis revealed that Cx. pipiens s.l. fed on several common urban avian species. CONCLUSIONS: Studies on mosquitoes are essential to understand their role in disease transmission and to design targeted and sustainable management strategies to mitigate the associated risks.

Infection, dissemination, and transmission of lumpy skin disease virus in Aedes aegypti (Linnaeus), Culex tritaeniorhynchus (Giles), and Culex quinquefasciatus (Say) mosquitoes.

Lumpy skin disease virus (LSDV) is a transboundary viral disease in cattle and water buffaloes. Although this Poxvirus is supposedly transmitted by mechanical vectors, only a few studies have investigated the role of local vectors in the transmission of LSDV. This study examined the infection, dissemination, and transmission rates of LSDV in Aedes aegypti, Culex tritaeniorhynchus, and Culex quinquefasciatus following artificial membrane feeding of 102.7, 103.7, 104.7 TCID50/mL LSDV in sheep blood. The results demonstrated that these mosquito species were susceptible to LSDV, with Cx tritaeniorhynchus exhibiting significantly different characteristics from Ae. aegypti and Cx. quinquefasciatus. These three mosquito species were susceptible to LSDV. Ae. aegypti showed it as early as 2 days post-infection (dpi), indicating swift dissemination in this particular species. The extrinsic incubation period (EIP) of LSDV in Cx. tritaeniorhynchus and Cx. quinquefasciatus was 8 and 14 dpi, respectively. Ingestion of different viral titers in blood did not affect the infection, dissemination, or transmission rates of Cx. tritaeniorhynchus and Cx. quinquefasciatus. All rates remained consistently high at 8-14 dpi for Cx. tritaeniorhynchus. In all three species, LSDV remained detectable until 14 dpi. The present findings indicate that, Ae. aegypti, Cx. tritaeniorhynchus, and Cx. quinquefasciatus may act as vectors during the LSDV outbreak; their involvement may extend beyond being solely mechanical vectors.

Oxidative stress induction by essential oil from Piper alatipetiolatum (Piperaceae) triggers lethality in the larvae of Culex quinquefasciatus (Diptera: Culicidae).

Culex quinquefasciatus is the main vector of lymphatic filariasis in Brazil, which present resistance to commercial insecticides. Nowadays, essential oils (EOs) exhibiting larvicidal activity, such as those derived from Piper alatipetiolatum, provide a promising alternative for vector control, including Culex species. This study aimed to investigate the larvicidal activity and the oxidative stress indicators of the EO from P. alatipetiolatum in Cx. quinquefasciatus larvae. The EO was extracted from P. alatipetiolatum leaves using the hydrodistillation method, resulting in a yield of 7.2 ± 0.1%, analysed by gas chromatography coupled with spectrometry and gas chromatography coupled with flame ionization detector (GC-MS and GC-FID), and evaluated against Cx. quinquefasciatus larvae. Reactive Oxygen and Nitrogen Species (RONS), Catalase (CAT), glutathione-S-transferase (GST), acetylcholinesterase (AChE), and Thiol levels were used as oxidative stress indicators. Analysis by CG-MS and CG-FID revealed that the main compound in the EO was the oxygenated sesquiterpene ishwarone, constituting 78.6% of the composition. Furthermore, the EO exhibited larvicidal activity, ranging from 26 to 100%, with an LC50 of 4.53 µg/mL and LC90 of 15.37 µg/mL. This activity was accompanied by a significant increase in RONS production, alterations in CAT, GST, AChE activity, and thiol levels compared to the control groups (p < 0.05). To the best of our knowledge, this is the first report describing the larvicidal activity and oxidative stress induced by the EO from P. alatipetiolatum against Cx. quinquefasciatus larvae. Therefore, we propose that this EO shows promise as larvicidal agent for the effective control of Cx. quinquefasciatus larvae.

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

BACKGROUND: Culex 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. METHODS: Sampling 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. RESULTS: There 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. CONCLUSIONS: Cx. 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.

Prediction and validation of potential transmission risk of Dirofilaria spp. infection in Serbia and its projection to 2080.

Animal and human dirofilariosis is a vector-borne zoonotic disease, being one of the most important diseases in Europe. In Serbia, there are extensive studies reporting the presence of Dirofilaria immitis and D. repens, mainly in the north of the country, where the human population is concentrated and where there is a presence of culicid mosquitoes that transmit the disease. Ecological niche modeling (ENM) has proven to be a very good tool to predict the appearance of parasitosis in very diverse areas, with distant orography and climatologies at a local, continental, and global level. Taking these factors into account, the objective of this study was to develop an environmental model for Serbia that reflects the suitability of the ecological niche for the risk of infection with Dirofilaria spp. with which the predictive power of existing studies is improved. A wide set of variables related to the transmission of the parasite were used. The potential number of generations of D. immitis and the ecological niche modeling method (ENM) were used to estimate the potential distribution of suitable habitats for Culex pipiens. The highest probability of infection risk was located in the north of the country, and the lowest in the southern regions, where there is more orographic relief and less human activity. The model was corroborated with the location of D. immitis-infected dogs, with 89.28% of the country having a high probability of infection. In addition, it was observed that the percentage of territory with optimal habitat for Culex spp. will increase significantly between now and 2080. This new model can be used as a tool in the control and prevention of heartworm disease in Serbia, due to its high predictive power, and will serve to alert veterinary and health personnel of the presence of the disease in the animal and human population, respectively.

Host-Feeding Behavior of Mosquitoes in the Florida Everglades.

Background: West Nile virus (WNV), Everglades virus (EVEV), and five species of Orthobunyavirus were isolated from mosquitoes collected in the Everglades in 2016-2017. Prior studies of blood meals of mosquitoes in southern Florida have related findings to acquisition and transmission of EVEV, St. Louis encephalitis virus, and WNV, but not the Orthobunyavirus viruses associated with the subgenus Melanoconion of the genus Culex. Materials and Methods: In the present study, blood-fed mosquitoes were collected in the Everglades in 2016, 2017, 2021, and 2022, and from an industrial site in Naples, FL in 2017. Blood meals were identified to host species by PCR assays using mitochondrial cytochrome b gene. Results: Blood meals were identified from Anopheles crucians complex and 11 mosquito species captured in the Florida Everglades and from 3 species collected from an industrial site. The largest numbers of blood-fed specimens were from Culex nigripalpus, Culex erraticus, Culex cedecei, and Aedes taeniorhynchus. Cx. erraticus fed on mammals, birds, and reptiles, particularly American alligator. This mosquito species could transmit WNV to American alligator in the wild. Cx. nigripalpus acquired blood meals primarily from birds and mammals and frequently fed on medium-sized mammals and white-tailed deer. Water and wading birds were the primary avian hosts for Cx. nigripalpus and Cx. erraticus in the Everglades. Wading birds are susceptible to WNV and could serve as reservoir hosts. Cx. cedecei fed on five species of rodents, particularly black and hispid cotton rats. EVEV and three different species of Orthobunyavirus have been isolated from the hispid cotton rat and Cx. cedecei in the Everglades. Cx. cedecei is likely acquiring and transmitting these viruses among hispid cotton rats and other rodents. The marsh rabbit was a frequent host for An. crucians complex. An. crucians complex, and other species could acquire Tensaw virus from rabbits. Conclusions: Our study contributes to a better understanding of the host and viral associations of mosquito species in southwestern Florida.

Effect of textile colour on vector mosquito host selection: a simulated field study in Mali, West Africa.

BACKGROUND: The effect of clothing colour on the biting rates of different vector mosquito species is not well understood. Studies under tropical field conditions are lacking. This study aimed to determine the influence of clothing colours on mosquito biting rates in rural and suburban settings in West Africa. METHODS: We performed a simulated field study in a suburban and a rural site in Mali using Mosquito-Magnet traps utilizing CO2 and other attractants, which were covered with black, white, and black/white striped textile sheets covers. These targets operated continuously for 10 consecutive days with bright nights (around full moon) and 10 consecutive days with dark nights (around new moon). Trapped mosquitoes were collected and catch rates counted hourly. Mosquitoes were morphologically identified to the species complex level (Anopheles gambiae s.l. and Culex pipiens s.l.) or species level (Aedes aegypti). A subset of Anopheles specimens were further identified by molecular methods. RESULTS: Under bright-night conditions, An. gambiae s.l. was significantly more attracted to black targets than to white and striped targets; during dark nights, no target preference was noted. During bright nights, Cx. pipiens s.l. was significantly more attracted to black and striped targets than to white targets; a similar trend was noted during dark nights (not significant). For day-active Ae. aegypti, striped targets were more attractive than the other targets and black were more attractive than white targets. CONCLUSIONS: The study firstly demonstrated that under field conditions in Mali, West Africa, mosquito catch rates were influenced by different clothing colours, depending on mosquito species and light conditions. Overall, light colours were least attractive to host-seeking mosquitoes. Using white or other light-coloured clothing can potentially reduce bite exposure and risk of disease transmission in endemic tropical regions.

Vector competence of Swedish Culex pipiens mosquitoes for Usutu virus.

Usutu virus (USUV) is an emerging mosquito-borne flavivirus with increasing prevalence in Europe. Understanding the role of mosquito species in USUV transmission is crucial for predicting and controlling potential outbreaks. This study aimed to assess the vector competence of Swedish Culex pipiens for USUV. The mosquitoes were orally infected with an Italian strain of USUV (Bologna 2009) and infection rates (IR), dissemination rates (DR), and transmission rates (TR) were evaluated over 7 to 28 days post-infection. The study revealed that Swedish Cx. pipiens are susceptible to USUV infection, with a gradual decrease in IR over time. However, the percentage of mosquitoes with the ability to transmit the virus remained consistent across all time points, indicating a relatively short extrinsic incubation period. Overall, this research highlights the potential of Swedish Cx. pipiens as vectors for USUV and emphasizes the importance of surveillance and monitoring to prevent future outbreaks of mosquito-borne diseases.

The infection kinetics and transmission potential of two Guaico Culex viruses in Culex quinquefasciatus mosquitoes.

Guaico Culex virus (GCXV) is a newly identified segmented Jingmenvirus from Culex spp. mosquitoes in Central and South America. The genome of GCXV is composed of four or five single-stranded positive RNA segments. However, the infection kinetics and transmission capability of GCXV in mosquitoes remain unknown. In this study, we used reverse genetics to rescue two GCXVs (4S and 5S) that contained four and five RNA segments, respectively, in C6/36 â€‹cells. Further in vitro characterization revealed that the two GCXVs exhibited comparable replication kinetics, protein expression and viral titers. Importantly, GCXV RNAs were detected in the bodies, salivary glands, midguts and ovaries of Culex quinquefasciatus at 4-10 days after oral infection. In addition, two GCXVs can colonize Cx. quinquefasciatus eggs, resulting in positive rates of 15%-35% for the second gonotrophic cycle. In conclusion, our results demonstrated that GCXVs with four or five RNA segments can be detected in Cx. quinquefasciatus eggs during the first and second gonotrophic cycles after oral infection.

Landscape level associations between birds, mosquitoes and microclimates: possible consequences for disease transmission?

BACKGROUND: Mosquito-borne diseases are on the rise. While climatic factors have been linked to disease occurrences, they do not explain the non-random spatial distribution in disease outbreaks. Landscape-related factors, such as vegetation structure, likely play a crucial but hitherto unquantified role. METHODS: We explored how three critically important factors that are associated with mosquito-borne disease outbreaks: microclimate, mosquito abundance and bird communities, vary at the landscape scale. We compared the co-occurrence of these three factors in two contrasting habitat types (forest versus grassland) across five rural locations in the central part of the Netherlands between June and September 2021. RESULTS: Our results show that forest patches provide a more sheltered microclimate, and a higher overall abundance of birds. When accounting for differences in landscape characteristics, we also observed that the number of mosquitoes was higher in isolated forest patches. CONCLUSIONS: Our findings indicate that, at the landscape scale, variation in tree cover coincides with suitable microclimate and high Culex pipiens and bird abundance. Overall, these factors can help understand the non-random spatial distribution of mosquito-borne disease outbreaks.

The Perpetual Vector Mosquito Threat and Its Eco-Friendly Nemeses.

Mosquitoes are the most notorious arthropod vectors of viral and parasitic diseases for which approximately half the world's population, ~4,000,000,000, is at risk. Integrated pest management programs (IPMPs) have achieved some success in mitigating the regional transmission and persistence of these diseases. However, as many vector-borne diseases remain pervasive, it is obvious that IPMP successes have not been absolute in eradicating the threat imposed by mosquitoes. Moreover, the expanding mosquito geographic ranges caused by factors related to climate change and globalization (travel, trade, and migration), and the evolution of resistance to synthetic pesticides, present ongoing challenges to reducing or eliminating the local and global burden of these diseases, especially in economically and medically disadvantaged societies. Abatement strategies include the control of vector populations with synthetic pesticides and eco-friendly technologies. These "green" technologies include SIT, IIT, RIDL, CRISPR/Cas9 gene drive, and biological control that specifically targets the aquatic larval stages of mosquitoes. Regarding the latter, the most effective continues to be the widespread use of Lysinibacillus sphaericus (Ls) and Bacillus thuringiensis subsp. israelensis (Bti). Here, we present a review of the health issues elicited by vector mosquitoes, control strategies, and lastly, focus on the biology of Ls and Bti, with an emphasis on the latter, to which no resistance has been observed in the field.

Geographical Characteristics of Culex tritaeniorhynchus and Culex orientalis Microbiomes in Korea.

Mosquitoes, the primary vectors of arboviruses, harbor a diverse microbiome that plays a crucial role in their development, immunity, and vector competence. The composition of the mosquito microbiome is heavily influenced by the environment and habitats. Therefore, identifying the relationship between the habitat and the mosquito's microbial community can improve the overall understanding of mosquito biology. However, The microbiome profiles of Culex tritaeniorhynchus and Culex orientalis, known as transmission vectors of the Japanese encephalitis virus, are poorly understood. Using 16S rRNA Illumina sequencing, we hereby investigated the microbial profiles in these two mosquito species collected in several areas in the Republic of Korea. Thirty-six prevalent bacterial families were identified from these mosquito species. The microbial composition variations were primarily influenced by the mosquito collecting sites. Moreover, species biomarkers were identified by utilizing the regional specificity of the mosquito microbiome. Based on the microbiome profiles representing high similarity, Culex orientalis may share an ecological niche with Culex tritaeniorhynchus.

Ecological niche modeling analysis (Cx. pipiens), potential risk and projection of Dirofilaria spp. infection in Greece.

Vector-borne diseases continue to increase worldwide. Dirofilariosis is one of the most common vector-borne zoonotic diseases, mainly caused by Dirofilaria spp. (D. immitis and D. repens) and spread by culicid mosquitoes of different species. Greece is one of the countries in southern Europe where it is traditionally endemic, and its distribution is not homogeneous. The aim of this study was to develop an environmental model for Greece that reflects the suitability of the ecological niche for Dirofilaria spp. infection risk and its projection until 2080. For this purpose, we used the potential distribution of suitable habitats for Culex pipiens calculated using an ecological niche model (ENM) and the potential number of generations of Dirofilaria spp. The ecological niche model of Cx. pipiens in Greece showed good predictive power (AUC=0.897) with the parasite at a resolution of 1 km2. The variables that contributed most to the model were mean annual temperature, rivers and human footprint. The highest risk of infection was found in coastal areas and in riverside areas of the main river basins, as well as in irrigated areas of the mainland and peninsular regions and in the whole territory of island areas, and the lowest risk was found in areas of higher altitude. A positive relationship was found between the risk of dirofilariosis and the location of infected dogs, with 86.65% located in very high and high risk areas. In 2080, the percentage of territory gained by Cx. pipiens will increase by 261.52%. This model provides a high predictive value, predicted presence, and risk of Dirofilaria spp. infection and can serve as a tool for the management and control of this disease.

RNAi-Mediated Silencing of Laccase 2 in Culex pipiens Pupae via Dehydration and Soaking Results in Multiple Defects in Cuticular Development.

Mosquitoes transmit a range of pathogens, causing devastating effects on human health. Population genetic control strategies have been developed and successfully used for several mosquito species. The most important step in identifying potential targets for mosquito control is the understanding of gene function. RNA interference (RNAi) is a powerful tool for gene silencing which has been widely used to study gene function in insects via knockdown of expression. The success of RNAi in insects depends on the efficient delivery of dsRNA into the cells, with microinjections being the most commonly used to study mosquito gene function. However, microinjections in the pupal stage lead to significant mortality in Aedes and Culex species, and few studies have performed microinjections in Culicinae pupae. Advanced techniques, such as CRISPR/Cas9 knockout, require establishing individual mosquito lines for each gene studied, and maintaining such lines may be limited by the insect-rearing capacity of a laboratory. Moreover, at times gene knockout during early development (embryo stage) has a deleterious effect on mosquito development, precluding the analysis of gene function in the pupal and adult stages and its potential for mosquito control. There is a need for a simple procedure that can be used for the fast and reliable examination of adult gene function via RNAi knockdown. Here, we focus on the aquatic stages of the mosquito life cycle and suggest a quick and easy assay for screening the functional role of genes in Culex pipiens mosquitoes without using microinjections. By dehydration of early stage pupae and subsequent rehydration in highly concentrated dsRNA, we achieved a moderate knockdown of laccase 2, a gene that turns on in the pupal stage and is responsible for melanization and sclerotization of the adult cuticle.

The L1014F Knockdown Resistance Mutation Is Not a Strong Correlate of Phenotypic Resistance to Pyrethroids in Florida Populations of Culex quinquefasciatus.

Culex quinquefasciatus is an important target for vector control because of its ability to transmit pathogens that cause disease. Most populations are resistant to pyrethroids and often to organophosphates, the two most common classes of active ingredients used by public health agencies. A knockdown resistance (kdr) mutation, resulting in an amino acid change from a leucine to phenylalanine in the voltage gated sodium channel, is one mechanism contributing to the pyrethroid resistant phenotype. Enzymatic resistance has also been shown to play a very important role. Recent studies have shown strong resistance in populations even when kdr is relatively low, which indicates that factors other than kdr may be larger contributors to resistance. In this study, we examined, on a statewide scale (over 70 populations), the strength of the correlation between resistance in the CDC bottle bioassay and the kdr genotypes and allele frequencies. Spearman correlation analysis showed only moderate (-0.51) or weak (-0.29) correlation between the kdr genotype and permethrin or deltamethrin resistance, respectively. The frequency of the kdr allele was an even weaker correlate than genotype. These results indicate that assessing kdr in populations of Culex quinquefasciatus is not a good surrogate for phenotypic resistance testing.

Exploring the range of Culex mosquitoes in Western Argentinean Patagonia, unveiling the presence of Culex pipiens bioform pipiens in South America.

Culicids in Argentinean Patagonia are characterized by low species diversity and adaptation to extreme environmental conditions, yet few studies have been conducted in the region. To further assess the occurrence of Culicidae in Western Patagonia, and in particular the presence of Culex pipiens bioforms at the southernmost extent of their distribution, immature and adult specimens were collected aboveground across various land uses located in shrubland, steppe, and deciduous forest between 38.96 and 46.55°S. Mosquitoes were reported at 35 of the 105 inspected sites. Five species from the genus Culex were identified, all of which were present in the steppe and the forest, while only Cx. apicinus and members of the Cx. pipiens complex were collected in the shrubland. Within the latter, a total of 150 specimens were molecularly identified by PCR amplification of Ace-2 and CQ11 loci. The first-to-date occurrence of bioform pipiens in South America is reported, along with the first records of Cx. quinquefasciatus signatures in Patagonia. In addition, the distribution of Cx. acharistus and Cx. dolosus as south as Santa Cruz province is expanded, and the first record of Cx. eduardoi in Río Negro province is provided. Immature specimens of Cx. pipiens were conspicuous in human-made aquatic habitats (both containers and in the ground), while Cx. acharistus was more prominent in artificial containers and Cx. eduardoi was mainly in ground habitats, either natural or human-made. These findings provide valuable insights into the distribution and ecological roles of these mosquito species in a region of extreme environmental conditions.

Blinded by the light: does heat or light enhance wild mosquito (Diptera: Culicidae) attraction to CO2-baited traps in the Great Salt Lake area?

The New Jersey Light Trap has been among the earliest trap models used for mosquito surveillance in the United States. This trap was modernized in the 1950s to the miniature CDC light trap, with the addition of CO2 following soon after. The incandescent light has the tendency to attract nontarget insects, as well as losing a substantial portion of their energy as heat. Few studies have delineated whether heat or light in isolation make a difference in field collections using the former traps within the United States. Our study focused on isolating heat and light variables by using incandescent bulbs, light emitting diode (LED) bulbs, and electric heating patches affixed to a base model CO2 trap as designed at the Salt Lake City Mosquito Abatement District. Sites were selected in the urban and suburban foothills and canyons of the Wasatch Mountain front, industrial areas near the Salt Lake City International Airport, and rural wetlands in the marshes outlying the Great Salt Lake. Five traps were replicated within each sector during the summer and fall summer seasons. Collections were composed of Aedes dorsalis (Meigen), Culex pipiens L., Culex tarsalis Coquillett, and Culiseta inornata (Williston). Composition changes were a result of seasonal, rather than spatial, shifts. The results showed that LED light traps depressed collections of key species. Otherwise, there were negligible differences in collections among incandescent, heat film, and base model traps. In the Intermountain West, the miniature CDC trap is reliable enough to make programmatic decisions even if light usage varies by district.

New artificial hematophagy system with attractive polymeric biofilm for maintenance of Culex quinquefasciatus (Diptera: Culicidae) in the laboratory.

BACKGROUND: Maintaining mosquito colonies in the laboratory requires a blood supply so that females' oocytes can mature and oviposition can take place. In this study, a new artificial hematophagy system for colonization and maintenance of Culex quinquefasciatus in the laboratory was developed and tested. METHODS: We developed an attractive polymeric biofilm including 25% L-lactic acid for use as a membrane in an artificial hematophagy system and compared the feeding rate of females with Parafilm-M®. We also evaluated the oviposition rate, larval survival and adult emergence of females fed through the attractive biofilm. RESULTS: The average percentage of female Cx. quinquefasciatus fed through the attractive biofilm was 87%, while only 20% became engorged with Parafilm-M® (p < 0.0001). Feeding through the attractive biofilm developed in this study produced high levels of evaluated biological parameters; the percentage of egg laying by females that underwent artificial hematophagy through the biofilm was 90%, with an average of 158 eggs per raft. From these eggs, 97% of the larvae hatched, of which 95% reached the pupal stage. The adult emergence rate corresponded to 93% of pupae. CONCLUSIONS: Insects fed with attractant through the biofilm system had a higher engorgement rate compared to those fed through Parafilm-M®. Our study is preliminary and suggests that polymeric biofilm has great potential for artificially feeding mosquitoes in the laboratory. Based on this research, new studies will be carried out with biofilm and different systems.