Landscape heterogeneity creates diverse habitat and resources for mosquito vectors of disease. A consequence may be varied distribution and abundance of vector species over space and time dependent on niche requirements.We tested the hypothesis that landscape heterogeneity driven by urbanization influences the distribution and relative abundance of Culex pipiens, Cx. restuans, and Cx. quinquefasciatus, three vectors of West Nile virus (WNv) in the eastern North American landscape. We collected 9,803 cryptic Culex from urban, suburban, and rural sites in metropolitan Washington, District of Columbia, during the months of June-October, 2019-2021. In 2021, we also collected mosquitoes in April and May to measure early-season abundance and distribution. Molecular techniques were used to identify a subset of collected Culex to species (n = 2,461). Ecological correlates of the spatiotemporal distribution of these cryptic Culex were examined using constrained and unconstrained ordination.Seasonality was not associated with Culex community composition in June-October over three years but introducing April and May data revealed seasonal shifts in community composition in the final year of our study. Culex pipiens were dominant across site types, while Cx. quinquefasciatus were associated with urban environments, and Cx. restuans were associated with rural and suburban sites. All three species rarely coexisted.Our work demonstrates that human-mediated land-use changes influence the distribution and relative abundance of Culex vectors of WNv, even on fine geospatial scales. Site classification, percent impervious surface, distance to city center, and longitude predicted Culex community composition. We documented active Culex months before vector surveillance typically commences in this region, with Culex restuans being most abundant during April and May. Active suppression of Cx. restuans in April and May could reduce early enzootic transmission, delay the seasonal spread of WNv, and thereby reduce overall WNv burden. By June, the highest risk of epizootic spillover of WNv to human hosts may be in suburban areas with high human population density and mixed Culex assemblages that can transmit WNv between birds and humans. Focusing management efforts there may further reduce human disease burden.

UNASSIGNED: Vector-borne diseases like West Nile virus (WNV) pose a global health challenge, with rising incidence and distribution. Culex mosquitoes are crucial WNV vectors. Avian species composition and bird community diversity, along with vector communities, influence WNV transmission patterns. However, limited knowledge exists on their impact in southwestern Spain, an area with active WNV circulation in wild birds, mosquitoes, and humans.
UNASSIGNED: To address this, we conducted a comprehensive study investigating the contributions of migratory and exotic bird species to WNV transmission and the influence of mosquito community composition.
UNASSIGNED: Analysing 1194 serum samples from 44 avian species, we detected WNV antibodies in 32 samples from 11 species, four for the first time in Europe. Migratory birds had higher WNV exposure likelihood than native and exotic species, and higher phylogenetic diversity in bird communities correlated with lower exposure rates. Moreover, in 5859 female mosquitoes belonging to 12 species, we identified WNV competent vectors like Cx. pipiens s.l. and the Univittatus subgroup. Birds with WNV antibodies were positively associated with competent vector abundance, but negatively with overall mosquito species richness.
UNASSIGNED: These findings highlight the complex interactions between bird species, their phylogenetics, and mosquito vectors in WNV transmission. Understanding these dynamics will help to implement effective disease control strategies in southwestern Spain.

BACKGROUND: Pathogens that reproduce or develop in mosquitoes can transmit several diseases, endanger human health, and overwhelm health systems. Synthetic pyrethroids are the most widely used insecticides against adult mosquitoes, but their widespread use has led to resistance. The adenosine triphosphate (ATP)-binding cassette (ABC) transporters are involved in the resistance monitoring of insects, but their role and underlying mechanisms in insecticide resistance have not been fully elucidated. In the present study, we identified ABC transporter genes in Culex pipiens and investigated their role in the development of insecticide resistance.
RESULTS: We identified 63 ABC transporter genes in Cx. pipiens and classified them as per the ABC transporter subfamilies. We also performed phylogenetic analysis. The knockdown rate of the mosquitoes orally fed with the ABC transporter inhibitor verapamil increased after deltamethrin treatment compared with that of the control group. Several genes from the ABCB, ABCC, and ABCG subfamilies were highly expressed in resistant mosquitoes. Immunofluorescence analysis revealed that ABCG6032427 was expressed in the head, chest, abdomen, wings, and legs, and the expression was the highest in the legs. Subsequently, knockdown of ABCG6032427 using RNA interference (RNAi) increased the sensitivity of the mosquitoes to deltamethrin, and scanning and transmission electron microscopy revealed that ABCG6032427 knockdown reduced cuticle thickness and the cuticle became loose and irregular.
CONCLUSIONS: ABCG6032427 may modulate cuticle thickness and structure, thus play an important role in the development of deltamethrin resistance in mosquitoes. Thus, it could be a potential target for deltamethrin resistance management in Cx. pipiens. © 2023 Society of Chemical Industry.

Usutu virus (USUV) is an arthropod-borne virus (arbovirus) of the flaviviridae family (genus Flavivirus) which belong to the Japanese encephalitis virus complex. Culex mosquitoes have been implicated in the transmission of this pathogen. The major susceptible hosts of USUV are migratory birds, thereby potentiating its ability to spread from one region to another globally. Nigeria has the largest economy in Africa with a significant percentage of the gross domestic product relying on the agricultural and animal production industry. This review explores the zoonotic potentials of the virus in Africa, especially Nigeria, with special focus on the devastating sequelae this might lead to in the future if necessary precautionary policies are not enacted and adopted to bolster the surveillance system for mosquito-borne viruses.

Since its introduction to North America in 1999, the West Nile virus (WNV) has resulted in over 50,000 human cases and 2400 deaths. WNV transmission is maintained via mosquito vectors and avian reservoir hosts, yet mosquito and avian infections are not uniform across ecological landscapes. As a result, it remains unclear whether the ecological communities of the vectors or reservoir hosts are more predictive of zoonotic risk at the microhabitat level. We examined this question in central Iowa, representative of the midwestern United States, across a land use gradient consisting of suburban interfaces with natural and agricultural habitats. At eight sites, we captured mosquito abundance data using New Jersey light traps and monitored bird communities using visual and auditory point count surveys. We found that the mosquito minimum infection rate (MIR) was better predicted by metrics of the mosquito community than metrics of the bird community, where sites with higher proportions of Culex pipiens group mosquitoes during late summer (after late July) showed higher MIRs. Bird community metrics did not significantly influence mosquito MIRs across sites. Together, these data suggest that the microhabitat suitability of Culex vector species is of greater importance than avian community composition in driving WNV infection dynamics at the urban and agricultural interface.

An outbreak of Japanese encephalitis (JE) was reported in Solan district of Himachal Pradesh, India in May 2018 wherein a total of eight JE cases were reported by the state health department, of which seven cases were confirmed by ELISA. An entomological survey was carried out to investigate the presence of vector mosquitoes in the affected area. Field visits were undertaken in eight villages of two blocks in Solan district. Larval collections were made from the major aquatic sites and emerging mosquito species were identified. Seepage water ditches were the main source of JE vector mosquitoes Culex tritaeniorhynchus and Cx. bitaeniorhynchus. During hand catch collections of adult mosquitoes, three vector species of JE,Culex tritaeniorhynchus (Man Hour Density 1-14), Cx. vishnui (MHD 2) and Cx. bitaeniorhynchus (MHD 1-2) were collected. A few specimens of Cx. tritaeniorhynchus (6 no.) were also collected in light trap collections. Since this was the first reported outbreak of JE from Himachal Pradesh, India, studies on sero-surveillance in addition to bionomics of JE vectors are required for better understanding of epidemiology of JE in Himachal Pradesh. Moreover, there is a need to study the role of climate change especially rising temperature in the context of JE in Himachal Pradesh.

OBJECTIVE: To investigate the distribution and density of Culex mosquito populations and the resistance of Culex pipiens pallens to insecticides in Jiangsu Province in 2018 and 2019.
METHODS: During the period from June to October in 2018 and 2019, six counties (districts, cities) were sampled in southern, northern and central Jiangsu Province as surveillance sites. The density of Culex mosquitoes was measured overnight using the light trapping technique. In addition, Culex pipiens pallens mosquitoes were collected from Hai\'an of Nantong City and Yandu District of Yancheng City, central Jiangsu Province, and the sensitivity of female first filial generations to dichlorodiphenyltrichloroethane (DDT), malation, proposur, beta cypermethrin and deltamethrin was tested using the standard WHO insecticide susceptibility test assay.
RESULTS: A total of 104 423 Culex mosquitoes were captured in six surveillance sites of Jiangsu Province in 2018 and 2019, and Culex quinquefasciatus (49.11%), Culex pipiens pallens (28.38%), and Culex tritaeniorhynchus (21.04%) were predominant species. The density of Culex mosquitoes started to increase since early June, peaked in July and tended to be low in late October. Culex pipiens pallens mosquitoes captured from Hai\'an was susceptible to malation, while those from Yandu District were moderately resistant to malation. Culex pipiens pallens mosquitoes from both Yandu and Hai\'an were moderately resistant to proposur, and were resistant to DDT, beta cypermethrin and deltamethrin.
CONCLUSIONS: Culex quinquefasciatus, Culex pipiens pallens and Culex tritaeniorhynchus are predominant Culex species in Jiangsu Province. Culex pipiens pallens is resistant to DT, beta cypermethrin and deltamethrin in central Jiangsu Province.
［摘要］ 目的 了解2018—2019年江苏省库蚊种群分布、密度变化及淡色库蚊对杀虫剂的抗性水平。方法 2018—2019年6—10月, 选择江苏省苏南、苏北和苏中6个县 (市、区) 作为监测点, 采用全通宵诱蚊灯法调查库蚊种群密度。采集苏中地区南通市海安市和盐城市盐都区淡色库蚊, 采用WHO推荐的接触筒强迫接触法测定子1代雌性淡色库蚊对二氯二苯三氯乙烷 (dichlorodiphenyltrichloroethane, DDT)、马拉硫磷、残杀威、高效氯氰菊酯和溴氰菊酯5种杀虫剂的敏感性。结果 2018—2019年在江苏省6个监测点累计库蚊104 423只, 蚊种以致倦库蚊、淡色库蚊和三带喙库蚊为主, 分别占49.11%、28.38%和21.04%; 库蚊种群密度从6月初开始升高, 7月左右达到峰值, 10月下旬趋近于低值。海安市淡色库蚊对马拉硫磷抗性级别为敏感, 盐都区淡色库蚊对马拉硫磷抗性级别为初步抗性; 盐都区、海安市淡色库蚊对残杀威抗性级别均为初步抗性; 盐都区、海安市淡色库蚊对DDT、高效氯氰菊酯、溴氰菊酯抗性级别均为抗性。结论 江苏省库蚊种群以致倦库蚊、淡色库蚊、三带喙库蚊为主; 苏中地区淡色库蚊已对DDT、高效氯氰菊酯和溴氰菊酯产生抗性。.

Since the reemergence of St. Louis Encephalitis (SLE) Virus (SLEV) in the Southwest United States, identified during the 2015 outbreak in Arizona, SLEV has been seasonally detected within Culex spp. populations throughout the Southwest United States. Previous work revealed the 2015 outbreak was caused by an importation of SLEV genotype III, which had only been detected previously in Argentina. However, little is known about when the importation occurred or the transmission and genetic dynamics since its arrival into the Southwest. In this study, we sought to determine whether the annual detection of SLEV in the Southwest is due to enzootic cycling or new importations. To address this question, we analyzed 174 SLEV genomes (142 sequenced as part of this study) using Bayesian phylogenetic analyses to estimate the date of arrival into the American Southwest and characterize the underlying population structure of SLEV. Phylogenetic clustering showed that SLEV variants circulating in Maricopa and Riverside counties form two distinct populations with little evidence of inter-county transmission since the onset of the outbreak. Alternatively, it appears that in 2019, Yuma and Clark counties experienced annual importations of SLEV that originated in Riverside and Maricopa counties. Finally, the earliest representatives of SLEV genotype III in the Southwest form a polytomy that includes both California and Arizona samples. We propose that the initial outbreak most likely resulted from the importation of a population of SLEV genotype III variants, perhaps in multiple birds, possibly multiple species, migrating north in 2013, rather than a single variant introduced by one bird.

Mosquitoes harbor an extensive diversity of \'insect-specific\' RNA viruses in addition to those important to human and animal health. However, because most studies of the mosquito virome have been conducted at lower latitudes, little is known about the diversity and evolutionary history of RNA viruses sampled from mosquitoes in northerly regions. Here, we compared the RNA virome of two common northern mosquito species, Culex pipiens and Culex torrentium, collected in south-central Sweden. Following bulk RNA-sequencing (meta-transcriptomics) of 12 libraries, comprising 120 specimens of Cx. pipiens and 150 specimens of Cx. torrentium, we identified 40 viruses (representing 14 virus families) of which 28 were novel based on phylogenetic analysis of the RNA-dependent RNA polymerase (RdRp) protein. Hence, we documented similar levels of virome diversity as in mosquitoes sampled from the more biodiverse lower latitudes. Many viruses were also related to those sampled on other continents, indicative of a widespread global movement and/or long host-virus co-evolution. Although the two mosquito species investigated have overlapping geographical distributions and share many viruses, several viruses were only found at a specific location at this scale of sampling, such that local habitat and geography may play an important role in shaping viral diversity in Culex mosquitoes.

Of the 3,500 species of mosquitoes worldwide, only a small portion carry and transmit the mosquito-borne diseases (MBDs) that cause approximately half a million deaths annually worldwide. The most common exotic MBDs, such as malaria and dengue, are not currently established in Canada, in part because of our relatively harsh climate; however, this situation could evolve with climate change. Mosquitoes native to Canada may become infected with new pathogens and move into new regions within Canada. In addition, new mosquito species may move into Canada from other countries, and these exotic species may bring exotic MBDs as well. With high levels of international travel, including to locations with exotic MBDs, there will be more travel-acquired cases of MBDs. With climate change, there is the potential for exotic mosquito populations to become established in Canada. There is already a small area of Canada where exotic Aedes mosquitoes have become established although, to date, there is no evidence that these carry any exotic (or already endemic) MBDs. The increased risks of spreading MBDs, or introducing exotic MBDs, will need a careful clinical and public health response. Clinicians will need to maintain a high level of awareness of current trends, to promote mosquito bite prevention strategies, and to know the laboratory tests needed for early detection and when to report laboratory results to public health. Public health efforts will need to focus on ongoing active surveillance, public and professional awareness and mosquito control. Canadians need to be aware of the risks of acquiring exotic MBDs while travelling abroad as well as the risk that they could serve as a potential route of introduction for exotic MBDs into Canada when they return home.