Host-feeding preference of the mosquito, Culex quinquefasciatus, in Yucatan State, Mexico

The mosquitoes (Diptera: Culicidae) of the Mexican Yucatan Peninsula: a comprehensive review on the use of taxonomic names

The Yucatan Peninsula is a biogeographic province of the Neotropical region which is mostly encompassed by the 3 Mexican states of Campeche, Quintana Roo, and Yucatán. During the development of the International Joint Laboratory ELDORADO (Ecosystem, bioLogical Diversity, habitat mOdifications and Risk of emerging PAthogens and Diseases in MexicO), a French-Mexican collaboration between the IRD (Institut de Recherche pour le Développement) and UNAM (Universidad Nacional Autónoma de México) in Mérida, it became evident that many putative mosquito species names recorded in the Mexican Yucatan Peninsula were misidentifications/misinterpretations or from the uncritical repetition of incorrect literature records. To provide a stronger foundation for future studies, the mosquito fauna of the Mexican Yucatan Peninsula is here comprehensively reviewed using current knowledge of taxonomy, ecology, and distribution of species through extensive bibliographic research, and examination of newly collected specimens. As a result, 90 mosquito species classified among 16 genera and 24 subgenera are recognized to occur in the Mexican Yucatan Peninsula, including 1 new peninsula record and 3 new state records.

The midgut epithelium of mosquitoes adjusts cell proliferation and endoreplication to respond to physiological challenges

BACKGROUND

Hematophagous mosquitoes transmit many pathogens that cause human diseases. Pathogen acquisition and transmission occur when female mosquitoes blood feed to acquire nutrients for reproduction. The midgut epithelium of mosquitoes serves as the point of entry for transmissible viruses and parasites.

RESULTS

We studied midgut epithelial dynamics in five major mosquito vector species by quantifying PH3-positive cells (indicative of mitotic proliferation), the incorporation of nucleotide analogs (indicative of DNA synthesis accompanying proliferation and/or endoreplication), and the ploidy (by flow cytometry) of cell populations in the posterior midgut epithelium of adult females. Our results show that the epithelial dynamics of post-emergence maturation and of mature sugar-fed guts were similar in members of the Aedes, Culex, and Anopheles genera. In the first three days post-emergence, ~ 20% of cells in the posterior midgut region of interest incorporated nucleotide analogs, concurrent with both proliferative activity and a broad shift toward higher ploidy. In mature mosquitoes maintained on sugar, an average of 3.5% of cells in the posterior midgut region of interest incorporated nucleotide analogs from five to eight days post-emergence, with a consistent presence of mitotic cells indicating constant cell turnover. Oral bacterial infection triggered a sharp increase in mitosis and nucleotide analog incorporation, suggesting that the mosquito midgut undergoes accelerated cellular turnover in response to damage. Finally, blood feeding resulted in an increase in cell proliferation, but the nature and intensity of the response varied by mosquito species and by blood source (human, bovine, avian or artificial). In An. gambiae, enterocytes appeared to reenter the cell cycle to increase ploidy after consuming blood from all sources except avian.

CONCLUSIONS

We saw that epithelial proliferation, differentiation, and endoreplication reshape the blood-fed gut to increase ploidy, possibly to facilitate increased metabolic activity. Our results highlight the plasticity of the midgut epithelium in mosquitoes' physiological responses to distinct challenges.

Japanese encephalitis virus: epidemiology and risk-based surveillance approaches for New Zealand

The introduction and subsequent rapid spread of Japanese encephalitis virus genotype IV across all Australian mainland states and the Northern Territory since late 2021 has increased the risk of an incursion of this mosquito-transmitted zoonotic virus disease into New Zealand, with serious implications for both animal and human health. The potential modes of entry are through introduction of infected mosquitoes as hitchhikers on ships or aircraft, windborne transfer of mosquitoes, or arrival of infected reservoir bird species. A competent vector mosquito, Culex quinquefasciatus, is endemic in New Zealand and other mosquito species may also become involved. If infection becomes established in New Zealand, the scale of transmission may be considerably less than has occurred in Australia because climatic and epidemiological factors are not so favourable. Early evidence of an incursion could come from detection of clinical disease in horses or pigs, or from human cases. Targeted surveillance to confirm or refute indications of an incursion could be undertaken by antibody detection in a number of species. Dogs have been shown to be a particularly valuable sentinel species due to their cohabitation with people and high seroconversion rate. Other novel methods of surveillance could include reverse transcriptase PCR (RT-PCR) on oronasal secretions of pigs. Should evidence of the disease be detected, prompt action would be required to vaccinate at-risk human populations and clarify the epidemiological situation with respect to mammalian hosts and mosquito vector species, including whether a new mosquito species had arrived in the country.Abbreviations: AHL: Animal Health Laboratory; JE: Japanese encephalitis disease; JEV: Japanese encephalitis virus; RT-PCR: Reverse transcriptase PCR.

Characterization of the Blood-Feeding Patterns of Culex quinquefasciatus (Diptera: Culicidae) in San Bernardino County, California

West Nile virus (WNV) is a zoonotic disease that is endemic in North America and is known to cause a range of symptoms from mild to life threatening in humans. Culex quinquefasciatus is one of the most prominent vectors of WNV in Southern California. The goal of this study was to identify which animal species are most fed upon by these mosquitoes in various habitats in the West Valley area of San Bernardino County, California, and determine the relationship between blood-feeding patterns and WNV activity in the region. Culex quinquefasciatus specimens were collected by West Valley Mosquito and Vector Control District during 2011 from 32 different sites. The bloodmeals of 683 individuals (92.4% of those tested) were identified using the mitochondrial gene cytochrome c oxidase 1 (COI). These bloodmeals comprised 29 vertebrate species across four different habitats. Species richness (ranging from 10 to 17) was not significantly different between habitats when rarified to account for sample size. Across habitats, the highest percentage of avian bloodmeals were taken from house sparrows (18.8-39.1%) and house finches (2.6-31.5%). Bloodmeals were identified from five mammalian species, accounting for 5.1-59.2% of bloodmeals by habitat, including humans (0-4.1%). A seasonal shift towards increased mammalian bloodmeal prevalence, specifically for domestic dog and human bloodmeals, was observed in urban habitats. The WNV activity during 2011 in San Bernardino County occurred mostly in urban and suburban areas as indicated by minimum infection rate (MIR) in Culex quinquefasciatus, notable as all human bloodmeals were identified from these two habitats.

Detection and molecular characterization of Avipoxvirus in Culex spp. (Culicidae) captured in domestic areas in Rio de Janeiro, Brazil

Avian pox is a highly contagious poultry disease that causes significant economic losses. Mosquitoes belonging to the genus Culex (Diptera: Culicidae) have a fundamental role in disseminating Avipoxvirus (Poxviridae). This study proposes investigating the presence of Avipoxvirus (APV) DNA in Culex spp. from Rio de Janeiro to determine its frequency and perform a phylogenetic analysis based on the core like the 4b protein (p4b) gene. The detection of APVs was conducted individually on four hundred Culex spp. mosquitoes. A total of 12.23% (47/384) of the Culex spp. were positive in the PCR. Sequencing the p4b gene revealed that this study’s sequences displayed 98.8–99% identity with Fowlpoxvirus (FWPW) sequences available in GenBank. In the phylogenetic analysis, these APVs were clustered in the A1 subclade together with FWPW sequences from several countries. The evolutionary distance of the p4b gene was 0.61 ± 0.21% in rural areas and 0.38 ± 0.16% in peri-urban areas. The current investigation is the first study to report the detection of APVs in field-caught mosquitoes. Moreover, a high frequency of APV DNA was observed in Culex spp. captured in domestic areas, where backyard poultry is present. This data demonstrates the importance of implementing control measures for Culex spp. to mitigate the transmission of APVs in backyard poultry in Rio de Janeiro.

Species Diversity, Habitat Distribution, and Blood Meal Analysis of Haematophagous Dipterans Collected by CDC-UV Light Traps in the Dominican Republic

Haematophagous insects cause major economic losses by both direct damage and the transmission of pathogens. However, the biting Diptera species in the Caribbean region have been poorly documented. During 2021, CDC downdraft suction traps with UV light were employed to assess both the species occurrence and blood meal sources across three different habitats in the Dominican Republic. Eighteen species of mosquitoes (n = 274), six species of Culicoides (n = 803), two black fly species (n = 2), and one species of muscid fly (n = 25) were identified at species-level by morphology and/or molecular phylogenetic approaches based on the mitochondrial cytochrome c oxidase subunit 1 (COI). Engorged mosquito (n = 5) and Culicoides (n = 28) females showed host preferences derived exclusively from mammals (cows and pigs), except Culex species containing the blood of chickens. Our study provides new records of the Diptera Dominican catalogue (Culex salinarius for the Greater Antilles, Culicoides jamaicensis for Hispaniola, and Culicoides haitiensis and Culicoides borinqueni for the Dominican Republic), the first available COI DNA sequences of different Diptera in the GenBank, some pictures of diagnostic features of closely related specimens, spatial distribution across the habitats studied, and new insights on their feeding preferences in the Caribbean region.

Mosquito (Diptera: Culicidae) diversity and medical importance in Koh Kong mangrove forests, Cambodia

Background

Mangroves are an ecosystem interface between land and sea, forming distinctive shallow-water marine communities in tropical and subtropical waters. The mangrove forest surface in Cambodia is being reduced due to deforestation. Because the mangrove type of ecosystem generally hosts a great diversity of mosquitoes, the urbanization of these ecosystems will increase interactions between humans and wild mosquitoes, and might thus serve as a potential source of new infectious diseases. Understanding mosquito diversity and analyzing their virome is critical to estimate the risk of emergence or future outbreaks of mosquito-borne diseases.

Objective

To understand the mosquito diversity of mangrove forests of Koh Kong province (Cambodia).

Methods

In 2019, the mosquito fauna was sampled for 3 consecutive days using BG-Sentinel and light traps, in 3 locations in the mangrove forests of Koh Kong province (Cambodia) during both dry and rainy seasons.

Results

A total of 3107 samples were collected, belonging to 10 genera for 34 species. The Culex genus was the most diverse, accounting for 10 species. One species, Culex sitiens, represented over 60% of all collected mosquitoes. A total of 12 medically important species were recorded, 2 species, Aedes (Stegomyia) albopictus and Culex vishnui, were collected in all sites and during both the dry and rainy seasons, highlighting a potential risk of these species acting as bridge vectors.

Conclusions

If new arboviruses were to be recorded in this peculiar area, it would indicate that the mosquito species found have the potential to act as a bridge between sylvatic and anthropogenic arboviruses.

Using Data Mining and Network Analysis to Infer Arboviral Dynamics: The Case of Mosquito-Borne Flaviviruses Reported in Mexico

Given the significant impact of mosquito-borne flaviviruses (MBFVs) on both human and animal health, predicting their dynamics and understanding their transmission cycle is of the utmost importance. Usually, predictions about the distribution of priority pathogens, such as Dengue, Yellow fever, West Nile Virus and St. Louis encephalitis, relate abiotic elements to simple biotic components, such as a single causal agent. Furthermore, focusing on single pathogens neglects the possibility of interactions and the existence of common elements in the transmission cycles of multiple pathogens. A necessary, but not sufficient, condition that a mosquito be a vector of a MBFV is that it co-occurs with hosts of the pathogen. We therefore use a recently developed modeling framework, based on co-occurrence data, to infer potential biotic interactions between those mosquito and mammal species which have previously been identified as vectors or confirmed positives of at least one of the considered MBFVs. We thus create models for predicting the relative importance of mosquito species as potential vectors for each pathogen, and also for all pathogens together, using the known vectors to validate the models. We infer that various mosquito species are likely to be significant vectors, even though they have not currently been identified as such, and are likely to harbor multiple pathogens, again validating the predictions with known results. Besides the above "niche-based" viewpoint we also consider an assemblage-based analysis, wherein we use a community-identification algorithm to identify those mosquito and/or mammal species that form assemblages by dint of their significant degree of co-occurrence. The most cohesive assemblage includes important primary vectors, such as A. aegypti, A. albopictus, C. quinquefasciatus, C. pipiens and mammals with abundant populations that are well-adapted to human environments, such as the white-tailed deer (Odocoileus virginianus), peccary (Tayassu pecari), opossum (Didelphis marsupialis) and bats (Artibeus lituratus and Sturnira lilium). Our results suggest that this assemblage has an important role in the transmission dynamics of this viral group viewed as a complex multi-pathogen-vector-host system. By including biotic risk factors our approach also modifies the geographical risk profiles of the spatial distribution of MBFVs in Mexico relative to a consideration of only abiotic niche variables.

West Nile and Zika viruses in bats from a suburban area of Merida, Yucatan, Mexico

Infections with viruses of the Flavivirus genus were explored in 22 bats (Artibeus jamaicensis) from Merida, Yucatan, Mexico. The detection of the viral genus was performed by RT-PCR, and infections with dengue (DENV 1-4), West Nile (WNV) and Zika (ZIKV) viruses were subsequently explored. Sequences from positive products were analysed using the BLAST algorithm to determine identity. In 7 (31.8%) and 2 (9.1%) bats, WNV and ZIKV were identified, respectively. The bioinformatic analysis showed 98%-100% coverage and identity for both viruses. Molecular evidence of WNV and ZIKV natural infection in bats from Yucatan, Mexico, is presented.

Bloodmeal sources and feeding behavior of anopheline mosquitoes in Bure district, northwestern Ethiopia

BACKGROUND

Mosquito bloodmeal sources determine the feeding rates, adult survival, fecundity, hatching rates, and developmental times. Only the female Anopheles mosquito takes bloodmeals from humans, birds, mammals, and other vertebrates for egg development. Studies of the host preference patterns in blood-feeding anopheline mosquitoes are crucial to determine malaria vectors. However, the human blood index, foraging ratio, and host preference index of anopheline mosquitoes are not known so far in Bure district, Ethiopia.

METHODS

The origins of bloodmeals from all freshly fed and a few half-gravid exophagic and endophagic females collected using Centers for Disease Control and Prevention light traps were identified as human and bovine using enzyme-linked immunosorbent assay. The human blood index, forage ratio, and host feeding index were calculated.

RESULTS

A total of 617 specimens belonging to An. arabiensis (n = 209), An. funestus (n = 217), An. coustani (n = 123), An. squamosus (n = 54), and An. cinereus (n = 14) were only analyzed using blood ELISA. Five hundred seventy-five of the specimens were positive for blood antigens of the host bloods. All anopheline mosquitoes assayed for a bloodmeal source had mixed- rather than single-source bloodmeals. The FR for humans was slightly > 1.0 compared to bovines for all Anopheles species. HFI for each pair of vertebrate hosts revealed that humans were the slightly preferred bloodmeal source compared to bovines for all species (except An. squamosus), but there was no marked host selection.

CONCLUSIONS

All anopheline mosquitoes assayed for bloodmeal ELISA had mixed feeds, which tends to diminish the density of gametocytes in the mosquito stomach, thereby reducing the chance of fertilization of the female gamete and reducing the chances of a malaria vector becoming infected. Moreover, An. coustani was the only species that had only human bloodmeals, meaning that this species has the potential to transmit the disease. Therefore, combination zooprophylaxis should be reinforced as a means of vector control because the study sites are mixed dwellings.

An Integrated Molecular Approach to Untangling Host-Vector-Pathogen Interactions in Mosquitoes (Diptera: Culicidae) From Sylvan Communities in Mexico

There are ~240 species of Culicidae in Mexico, of which some are vectors of arthropod-borne viruses such as Zika virus, dengue virus, chikungunya virus, and West Nile virus. Thus, the identification of mosquito feeding preferences is paramount to understanding of vector–host–pathogen interactions that, in turn, can aid the control of disease outbreaks. Typically, DNA and RNA are extracted separately for animal (insects and blood meal hosts) and viral identification, but this study demonstrates that multiple organisms can be analyzed from a single RNA extract. For the first time, residual DNA present in standard RNA extracts was analyzed by DNA barcoding in concert with Sanger and next-generation sequencing (NGS) to identify both the mosquito species and the source of their meals in blood-fed females caught in seven sylvan communities in Chiapas State, Mexico. While mosquito molecular identification involved standard barcoding methods, the sensitivity of blood meal identification was maximized by employing short primers with NGS. In total, we collected 1,634 specimens belonging to 14 genera, 25 subgenera, and 61 morphospecies of mosquitoes. Of these, four species were new records for Mexico (Aedes guatemala, Ae. insolitus, Limatus asulleptus, Trichoprosopon pallidiventer), and nine were new records for Chiapas State. DNA barcode sequences for >300 bp of the COI gene were obtained from 291 specimens, whereas 130 bp sequences were recovered from another 179 specimens. High intraspecific divergence values (>2%) suggesting cryptic species complexes were observed in nine taxa: Anopheles eiseni (5.39%), An. pseudopunctipennis (2.79%), Ae. podographicus (4.05%), Culex eastor (4.88%), Cx. erraticus (2.28%), Toxorhynchites haemorrhoidalis (4.30%), Tr. pallidiventer (4.95%), Wyeomyia adelpha/Wy. guatemala (7.30%), and Wy. pseudopecten (4.04%). The study increased the number of mosquito species known from 128 species to 138 species for Chiapas State, and 239 for Mexico as a whole. Blood meal analysis showed that Aedes angustivittatus fed on ducks and chicken, whereas Psorophora albipes fed on humans. Culex quinquefasciatus fed on diverse hosts including chicken, human, turkey, and Mexican grackle. No arbovirus RNA was detected by reverse transcriptase–polymerase chain reaction in the surveyed specimens. This study demonstrated, for the first time, that residual DNA present in RNA blood meal extracts can be used to identify host vectors, highlighting the important role of molecular approaches in both vector identification and revealing host–vector–pathogen interactions.

Whole blood and blood components from vertebrates differentially affect egg formation in three species of anautogenous mosquitoes

Background

Most female mosquitoes are anautogenous and must blood feed on a vertebrate host to produce eggs. Prior studies show that the number of eggs females lay per clutch correlates with the volume of blood ingested and that protein is the most important macronutrient for egg formation. In contrast, how whole blood, blood fractions and specific blood proteins from different vertebrates affect egg formation is less clear. Since egg formation is best understood in Aedes aegypti, we examined how blood and blood components from different vertebrates affect this species and two others: the malaria vector Anopheles gambiae and arbovirus vector Culex quinquefasciatus.

Methods

Adult female mosquitoes were fed blood, blood fractions and purified major blood proteins from different vertebrate hosts. Markers of reproductive response including ovary ecdysteroidogenesis, yolk deposition into oocytes and number of mature eggs produced were measured.

Results

Ae. aegypti, An. gambiae and C. quinquefasciatus responded differently to meals of whole blood, plasma or blood cells from human, rat, chicken and turkey hosts. We observed more similarities between the anthropophiles Ae. aegypti and An. gambiae than the ornithophile C. quinquefasciatus. Focusing on Ae. aegypti, the major plasma-derived proteins (serum albumin, fibrinogen and globulins) differentially stimulated egg formation as a function of vertebrate host source. The major blood cell protein, hemoglobin, stimulated yolk deposition when from pigs but not humans, cows or sheep. Serum albumins from different vertebrates also variably affected egg formation. Bovine serum albumin (BSA) stimulated ovary ecdysteroidogenesis, but more weakly induced digestive enzyme activities than whole blood. In contrast, BSA-derived peptides and free amino acids had no stimulatory effects on ecdysteroidogenesis or yolk deposition into oocytes.

Conclusions

Whole blood, blood fractions and specific blood proteins supported egg formation in three species of anautogenous mosquitoes but specific responses varied with the vertebrate source of the blood components tested.

Distribution and diversity of mosquitoes and Oropouche-like virus infection rates in an Amazonian rural settlement

Mosquito diversity and disease transmission are influenced by landscape modifications, i.e., vectors and pathogens previously found only in forests are now found close to human environments due to anthropic changes. This study determined the diversity and distribution of mosquitoes in forest environments in order to analyze the potential vectors of Amazonian forest arboviruses. Mosquitoes were collected by 1) vertical stratification from forest canopy and ground areas using Hooper Pugedo (HP) light traps and human attraction and 2) horizontal stratification using HP light traps in peridomicile, forest edge, and forest environments near the Rio Pardo rural settlement, Amazonas, Brazil. A total of 3,750 mosquitoes were collected, representing 46 species. 3,139 individuals representing 46 species were sampled by vertical stratification. Both the Shannon-Weaver diversity index (H’) and equitability (J’) were higher in the canopy than on the ground. 611 individuals representing 13 species were sampled by horizontal stratification. H’ decreased in the following order: forest edge > forest > peridomicile, and J’ was greater at the forest edge and smaller in the peridomicile environment. Moreover, H’ was higher for the human attraction collection method than the HP traps. A total of 671 pools were analyzed by RT-qPCR; three species were positive for Oropouche-like viruses (Ochlerotatus serratus, Psorophora cingulata, and Haemagogus tropicalis) and the minimum infection rate was 0.8%. The composition of mosquito species did not differ significantly between anthropic and forest environments in Rio Pardo. Some mosquito species, due to their abundance, dispersion in the three environments, and record of natural infection, were hypothesized to participate in the arbovirus transmission cycle in this Amazonian rural settlement.

Beat the heat: Culex quinquefasciatus regulates its body temperature during blood feeding

Mosquitoes are regarded as one of the most dangerous animals on earth. Because they are responsible for the spread of a wide range of both human and animal pathogens, research of the underlying mechanisms of their feeding behavior and physiology is critical. Among disease vector mosquitoes, Culex quinquefasciatus, a known carrier of West Nile virus and Western Equine Encephalitis, remains relatively understudied. As blood-sucking insects, adaptations (either at the molecular or physiological level) while feeding on warm blood are crucial to their survival, as overheating can result in death due to heat stress. Our research aims to determine how Cx. quinquefasciatus copes with the heat associated with warm blood meal ingestion and possibly uncover the adaptations this species uses to avoid thermal stress. Through the use of thermographic imaging, we analyzed the body temperature of Cx. quinquefasciatus while blood feeding. Infrared thermography has allowed us to identify a cooling strategy, evaporative cooling via the production of fluid droplets, and an overall low body temperature in comparison to the blood temperature during feeding. Understanding Cx. quinquefasciatus' adaptations and the strategies they employ to reduce their body temperature while blood feeding constitutes the first step towards discovering potential targets that could be used for their control.

Vertebrate-Aedes aegypti and Culex quinquefasciatus (Diptera)-arbovirus transmission networks: Non-human feeding revealed by meta-barcoding and next-generation sequencing

Background

Aedes aegypti mosquito-borne viruses including Zika (ZIKV), dengue (DENV), yellow fever (YFV), and chikungunya (CHIKV) have emerged and re-emerged globally, resulting in an elevated burden of human disease. Aedes aegypti is found worldwide in tropical, sub-tropical, and temperate areas. The characterization of mosquito blood meals is essential to understand the transmission dynamics of mosquito-vectored pathogens.

Methodology/principal findings

Here, we report Ae. aegypti and Culex quinquefasciatus host feeding patterns and arbovirus transmission in Northern Mexico using a metabarcoding-like approach with next-generation deep sequencing technology. A total of 145 Ae. aegypti yielded a blood meal analysis result with 107 (73.8%) for a single vertebrate species and 38 (26.2%) for two or more. Among the single host blood meals for Ae. aegypti, 28.0% were from humans, 54.2% from dogs, 16.8% from cats, and 1.0% from tortoises. Among those with more than one species present, 65.9% were from humans and dogs. For Cx. quinquefasciatus, 388 individuals yielded information with 326 (84%) being from a single host and 63 (16.2%) being from two or more hosts. Of the single species blood meals, 77.9% were from dogs, 6.1% from chickens, 3.1% from house sparrows, 2.4% from humans, while the remaining 10.5% derived from other 12 host species. Among those which had fed on more than one species, 11% were from dogs and humans, and 89% of other host species combinations. Forage ratio analysis revealed dog as the most over-utilized host by Ae. aegypti (= 4.3) and Cx. quinquefasciatus (= 5.6) and the human blood index at 39% and 4%, respectively. A total of 2,941 host-seeking female Ae. aegypti and 3,536 Cx. quinquefasciatus mosquitoes were collected in the surveyed area. Of these, 118 Ae. aegypti pools and 37 Cx. quinquefasciatus pools were screened for seven arboviruses (ZIKV, DENV 1–4, CHIKV, and West Nile virus (WNV)) using qRT-PCR and none were positive (point prevalence = 0%). The 95%-exact upper limit confidence interval was 0.07% and 0.17% for Ae. aegypti and Cx. quinquefasciatus, respectively

Conclusions/significance

The low human blood feeding rate in Ae. aegypti, high rate of feeding on mammals by Cx. quinquefasciatus, and the potential risk to transmission dynamics of arboviruses in highly urbanized areas of Northern Mexico is discussed.

Elucidating arbovirus-vector-host contact networks is critical to understand and control mosquito-borne virus transmission, including pathogens such as ZIKV, DENV 1–4, CHIKV, and WNV. Here, we report the results of metabarcoding of blood meals of two primary pathogen mosquito vectors, Aedes aegypti and Culex quinquefasciatus. We found limited human blood feeding by Ae. aegypti and high preference for feeding on mammals by Cx. quinquefasciatus. Interestingly, blood meal analysis revealed dogs as the most utilized host for both vector species suggesting the potential for zooprophylaxis for human-amplified urban arboviruses. Pools of these vector species were tested for seven arboviruses and all were negative. We calculated vectorial capacity to discuss the potential risk and transmission dynamics of pathogens transmitted by these two important vectors in an urban location in Northern Mexico.

Surveillance of Culicine Mosquitoes in Six Villages of Taita-Taveta County, Kenya, With Host Determinations From Blood-Fed Females

Culicine mosquitoes are vectors of human disease-causing pathogens like filarial worms and several arthropod-borne viruses (arboviruses). Currently, there has been an increase in emerging and re-emerging vector-borne diseases along coastal Kenya, which has been of major concern in public health. This study aimed at determining culicine mosquito species abundance, diversity and their host feeding preferences in Taita-Taveta County, Coastal Kenya. Entomological sampling was done during the long-wet season (March and May) and long dry season (June to October) 2016-2018. Mosquito sampling was done using CDC light traps and Backpack aspiration for indoor and outdoor environments. All culicine mosquitoes collected were identified morphologically and categorized according to their physiological status. Blood fed culicine mosquitoes were tested for bloodmeal sources using ELISA. In total, 3,278 culicine mosquitoes were collected, of which 738 (22.5 %) were found indoors and 2,540, (77.5 %) outdoors. The mosquitoes consisted of 18 species belonging to four genera: Aedes (7), Culex (8), Mansonia (2), and Coquillettidia (1). Overall, there was high mosquito species diversity (H) in outdoors (H = 2.4339) than in indoors (H = 2.2523), whereas even distribution (EH) was higher in indoors (EH = 0.9064) than outdoors (EH = 0.8266). Majorly the bloodmeals identified were from multiple host sources with (51.6%), single hosts (41.3%), and unidentified (7.2%). This study has demonstrated a high diversity of culicine mosquitoes with relaxed feeding tendencies. These mosquitoes are contributing to mosquito biting nuisance and the likelihood of exposure of populations to diseases of public health.

Discoveries of Exoribonuclease-Resistant Structures of Insect-Specific Flaviviruses Isolated in Zambia

To monitor the arthropod-borne virus transmission in mosquitoes, we have attempted both to detect and isolate viruses from 3304 wild-caught female mosquitoes in the Livingstone (Southern Province) and Mongu (Western Province) regions in Zambia in 2017. A pan-flavivirus RT-PCR assay was performed to identify flavivirus genomes in total RNA extracted from mosquito lysates, followed by virus isolation and full genome sequence analysis using next-generation sequencing and rapid amplification of cDNA ends. We isolated a newly identified Barkedji virus (BJV Zambia) (10,899 nt) and a novel flavivirus, tentatively termed Barkedji-like virus (BJLV) (10,885 nt) from Culex spp. mosquitoes which shared 96% and 75% nucleotide identity with BJV which has been isolated in Israel, respectively. These viruses could replicate in C6/36 cells but not in mammalian and avian cell lines. In parallel, a comparative genomics screening was conducted to study evolutionary traits of the 5'- and 3'-untranslated regions (UTRs) of isolated viruses. Bioinformatic analyses of the secondary structures in the UTRs of both viruses revealed that the 5'-UTRs exhibit canonical stem-loop structures, while the 3'-UTRs contain structural homologs to exoribonuclease-resistant RNAs (xrRNAs), SL-III, dumbbell, and terminal stem-loop (3'SL) structures. The function of predicted xrRNA structures to stop RNA degradation by Xrn1 exoribonuclease was further proved by the in vitro Xrn1 resistance assay.

Behavioural response of the house mosquitoes Culex quinquefasciatus and Culex pipiens molestus to avian odours and its reliance on carbon dioxide

How Culex (Diptera: Culicidae) mosquitoes select and discriminate between potential avian hosts is critical for understanding the epidemiology of West Nile virus. Therefore, the present authors studied the behavioural responses of Culex quinquefasciatus (Say) and Culex pipiens molestus (Forsskål) to headspace volatiles of three avian species [chicken and pigeon (sexes analysed separately), and magpie], presented either alone or in combination with 600 p.p.m. carbon dioxide (CO₂ ). The attraction of Cx. quinquefasciatus to the headspace volatiles of both sexes of chicken, and of female pigeon, in combination with CO₂ was significantly higher than that achieved by the CO₂ and solvent control. Although Cx. p. molestus was attracted to headspace volatiles of chickens and magpies, it was repelled by those of female pigeons when combined with CO₂ . An increased effect between the avian volatiles and CO₂ was observed for Cx. quinquefasciatus, whereas the addition of CO₂ had no effect on the attraction of Cx. p. molestus females. The results of this study demonstrate that Cx. quinquefasciatus and Cx. p. molestus are attracted to the odour of potential avian hosts. Future studies aimed at identifying the bioactive volatile compounds in the headspace of chickens may contribute to the potential development of effective surveillance and control tools against Culex species.

High Rate of Non-Human Feeding by Aedes aegypti Reduces Zika Virus Transmission in South Texas

Mosquito-borne viruses are emerging or re-emerging globally, afflicting millions of people around the world. Aedes aegypti, the yellow fever mosquito, is the principal vector of dengue, Zika, and chikungunya viruses, and has well-established populations across tropical and subtropical urban areas of the Americas, including the southern United States. While intense arboviral epidemics have occurred in Mexico and further south in the Americas, local transmission in the United States has been minimal. Here, we study Ae. aegypti and Culex quinquefasciatus host feeding patterns and vertebrate host communities in residential environments of South Texas to identify host-utilization relative to availability. Only 31% of Ae. aegypti blood meals were derived from humans, while 50% were from dogs and 19% from other wild and domestic animals. In Cx. quinquefasciatus, 67% of blood meals were derived from chicken, 22% came from dogs, 9% from various wild avian species, and 2% from other mammals including one human, one cat, and one pig. We developed a model for the reproductive number, R0, for Zika virus (ZIKV) in South Texas relative to northern Mexico using human disease data from Tamaulipas, Mexico. We show that ZIKV R0 in South Texas communities could be greater than one if the risk of human exposure to Ae. aegypti bites in these communities is at least 60% that of Northern Mexico communities. The high utilization of non-human vertebrates and low risk of human exposure in South Texas diminishes the outbreak potential for human-amplified urban arboviruses transmitted by Ae. aegypti.

PCR-Based Bloodmeal Analysis of Aedes aegypti and Culex quinquefasciatus (Diptera: Culicidae) in St. George Parish, Grenada

Blood-feeding patterns of mosquitoes affect the transmission and maintenance of arboviral diseases. In the Caribbean, Aedes aegypti (L.) and Culex quinquefasciatus Say mosquitoes are the dominant mosquito species in developed areas. However, no information is available on the bloodmeal hosts of these invasive vectors in Grenada, where arboviral pathogens such as dengue, chikungunya, and Zika viruses cause significant human suffering. To this end, Ae. aegypti and Cx. quinquefasciatus mosquitoes were investigated from five semirural locations near houses in St. George's Parish, from 2017 to 2018. Polymerase chain reaction was conducted on DNA extracted from individual blood-fed mosquitoes using vertebrate-specific cytochrome b primers. The 32 Ae. aegypti bloodmeals included humans (70%), mongooses (18%), domestic dogs (6%), a domestic cat (3%), and an unidentified bird (3%). Thirty-seven Cx. quinquefasciatus mosquitoes took bloodmeals from seven species of birds (51%), humans (27%), domestic cats (8%), iguanas (5%), a domestic dog (3%), a rat (3%), and a common opossum (3%). The high percentage of human bloodmeal hosts in our study, especially by the normally anthropophilic Ae. aegypti, is expected. The bloodmeal sources and the percentage of nonhuman bloodmeals (30%) taken by Ae. aegypti are comparable to other studies. The large range of hosts may be explained in part by the semirural nature of most local housing. Accordingly, this may contribute to an exchange of pathogens between domestic, peridomestic, and sylvatic transmission cycles.

Vector-borne transmission and evolution of Zika virus

Zika virus (ZIKV), discovered in the Zika Forest of Uganda in 1947, is a mosquito-borne flavivirus related to yellow fever, dengue and West Nile viruses. From its discovery until 2007, only sporadic ZIKV cases were reported, with mild clinical manifestations in patients. Therefore, little attention was given to this virus before epidemics in the South Pacific and the Americas that began in 2013. Despite a growing number of ZIKV studies in the past three years, many aspects of the virus remain poorly characterized, particularly the spectrum of species involved in its transmission cycles. Here, we review the mosquito and vertebrate host species potentially involved in ZIKV vector-borne transmission worldwide. We also provide an evidence-supported analysis regarding the possibility of ZIKV spillback from an urban cycle to a zoonotic cycle outside Africa, and we review hypotheses regarding recent emergence and evolution of ZIKV. Finally, we identify critical remaining gaps in the current knowledge of ZIKV vector-borne transmission.

Molecular identification of blood meals in mosquitoes (Diptera, Culicidae) in urban and forested habitats in southern Brazil

The study of host associations of mosquitoes (Diptera, Culicidae) provides valuable information to assist in our understanding of a variety of related issues, from their life-history to the entomological surveillance of pathogens. In this study, we identified and characterized mosquito blood meals from both urban and forested areas in the city of Paranaguá, state of Paraná, Brazil, by analyzing the amplification of host DNA ingested by mosquitoes under different storage conditions and digestion levels. Host DNA preservation was evaluated in fresh blood meals according to storage duration (30 to 180 days) and temperature (-20°C / -80°C) and, in digested blood, according the degree of digestion classified on the Sella scale. Molecular analysis of blood meals was based on DNA extraction and amplification of a fragment of the mitochondrial COI gene. We determined that, up to180 days of storage, the evaluated temperatures did not influence the preservation of fresh blood meals DNA, whereas the amplification success was increasingly reduced over the course of the digestion process. The species Anopheles cruzii, Aedes fluviatilis, Aedes scapularis, Psorophora ferox, Culex quinquefasciatus, Culex mollis, and Culex intrincatus, together with specimens representing four subgenera and one genus of Culicidae [Ae. (Ochlerotatus), Cx. (Culex), Cx. (Melanoconion), Cx. (Microculex), and Limatus, respectively] had their blood meals identified. Their diverse host use was evidenced by the identification of 19 species of vertebrate host, namely two amphibians, three mammals and 14 birds. Birds were the most commonly identified host in blood meals. These results not only show the diversity of mosquito hosts, but also underscore the challenges involved in monitoring arboviruses of public health importance, given potential combinations of host use for each mosquito species.

Prediction and prevention of urban arbovirus epidemics: A challenge for the global virology community

The recent emergence and rapid spread of Zika virus in tropical regions of the Western Hemisphere took arbovirologists and public health officials by surprise, and the earlier transfers of West Nile and chikungunya viruses from the Old to the New World were also unexpected. These pandemics underscore the increasing threat of zoonotic arboviruses, especially those that are capable of entering into human-amplified, urban transmission cycles transmitted by Aedes (Stegomyia) aegypti and sometimes other Aedes (Stegomyia) spp. mosquitoes. This review serves as an introduction to a World Health Organization-sponsored conference to be held on June 18-19, 2018 in Geneva, titled "From obscurity to urban epidemics: what are the next urban arboviruses?" It is intended to set the stage and fuel discussions of future urban arbovirus threats, how we can predict these risks from known and unknown viruses, and what factors may change these risks over time.

Diversity, distribution, abundance, and feeding pattern of tropical ornithophilic mosquitoes

Bird-biting mosquitoes act as bridge vectors of diverse pathogens of emerging infectious diseases. In this study, we report for the first time the abundance, diversity, distribution, and feeding pattern of bird-biting mosquitoes on an island where avifaunal diversity is rich. Monthly mosquito collections were done at six different habitats in three different climatic zones using bird-baited traps over a year. Collected mosquitoes were identified using morphological and molecular tools. A total of 2,655 bird-biting mosquitoes of eight genera and 25 species were identified. Of these, 52% were Culex species, which represents 35% of the Culex species in the country. The most abundant species were Culex sitiens, Cx. pseudovishnui, Cx. nigropunctatus and Cx. quinquefasciatus, whereas the latter two were common to all habitats. The highest abundance was reported in lowland forests (49.6%), while it was lowest in highland forests (22.3%). Highest species similarity was reported from highland forests. Seasonal variations of the most abundant species were significantly different in selected habitats (p< 0.05). Two distinct biting peaks were identified, from 06:00 to 21:00 and 22:00 to 02:00. The biting nature of identified ornithophilic mosquitoes suggests the potential vector status of these mosquitoes.

Transmission Incompetence of Culex quinquefasciatus and Culex pipiens pipiens from North America for Zika Virus

AbstractIn late 2014, Zika virus (ZIKV; Flaviviridae, Flavivirus) emerged as a significant arboviral disease threat in the Western hemisphere. Aedes aegypti and Aedes albopictus have been considered the principal vectors of ZIKV in the New World due to viral isolation frequency and vector competence assessments. Limited reports of Culex transmission potential have highlighted the need for additional vector competence assessments of North American Culex species. Accordingly, North American Culex pipiens and Culex quinquefasciatus were orally exposed and intrathoracically inoculated with the African prototype ZIKV strain and currently circulating Asian lineage ZIKV strains to assess infection, dissemination, and transmission potential. Results indicated that these two North American Culex mosquito species were highly refractory to oral infection with no dissemination or transmission observed with any ZIKV strains assessed. Furthermore, both Culex mosquito species intrathoracically inoculated with either Asian or African lineage ZIKVs failed to expectorate virus in saliva. These in vivo results were further supported by the observation that multiple mosquito cell lines of Culex species origin demonstrated significant growth restriction of ZIKV strains compared with Aedes-derived cell lines. In summation, no evidence for the potential of Cx. pipiens or Cx. quinquefasciatus to serve as a competent vector for ZIKV transmission in North America was observed.

Detection of West Nile virus in six mosquito species in synchrony with seroconversion among sentinel chickens in India

Background

West Nile virus (WNV) is a zoonotic flavivirus maintained in mosquito-bird transmission cycle. Although humans are accidental hosts, fatal outcomes following WNV infection have been reported from India. Studies have identified WNV as an important etiological agent causing acute encephalitis syndrome in Assam, Northeast India. While circulation of WNV is evident, the role of vectors and avian hosts involved in the transmission remains unclear. In this study we identified local mosquito species for evidence of WNV infection along with seroconversion among sentinel chickens.

Methods

Mosquitoes were collected and pooled species wise from June 2014 through December 2015. Virus was screened using reverse transcriptase PCR followed by sequencing and phylogenetic analysis. Sentinel chicken blood was screened for WNV antibody to assess their role in WNV transmission.

Results

A total of 52,882 mosquitoes belonging to 16 species were collected. WNV was detected in 18 pools of Culex vishnui, Culex tritaeniorhynchus, Culex quinquefasciatus, Culex whitmorei, Culex pseudovishnui and Mansonia uniformis. Phylogenetic analysis revealed that all mosquito derived sequences belonged to Lineage 5 and were 99–100% similar to the Assam strain of WNV isolated from human CSF sample in 2007. All sentinel chickens had seroconverted by the month of July that happens to be the peak WNV transmission month among humans as well.

Conclusion

To the best of our knowledge, this is the first report of WNV identification from field-collected Cx. pseudovishnui and Mansonia uniformis in India. Our study demonstrates potential vectors which may play a crucial role in WNV transmission and should be considered in the vector control strategies. Additionally, our study highlights the role of sentinel chickens for WNV surveillance.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1948-9) contains supplementary material, which is available to authorized users.

Zika Virus on a Spreading Spree: what we now know that was unknown in the 1950's

Zika virus (ZIKV) is a mosquito-borne flavivirus that is transmitted through the bite of Aedes spp mosquitoes and less predominantly, through sexual intercourse. Prior to 2007, ZIKV was associated with only sporadic human infections with minimal or no clinical manifestations. Recently the virus has caused disease outbreaks from the Pacific Islands, the Americas, and off the coast of West Africa with approximately 1.62 million people suspected to be infected in more than 60 countries around the globe. The recent ZIKV outbreaks have been associated with guillain-barré syndrome, congenital syndrome (microcephaly, congenital central nervous system anomalies), miscarriages, and even death. This review summarizes the path of ZIKV outbreak within the last decade, highlights three novel modes of ZIKV transmission associated with recent outbreaks, and points to the hallmarks of congenital syndrome. The review concludes with a summary of challenges facing ZIKV research especially the control of ZIKV infection in the wake of most recent data showing that anti-dengue virus antibodies enhance ZIKV infection.

Mammalophilic feeding behaviour of Culex quinquefasciatus mosquitoes collected in the cities of Chetumal and Cancun, Yucatán Peninsula, Mexico

OBJECTIVE

The studie describes the blood-feeding behaviour of mosquitoes in Mexico, to understand host-vector relationships and dynamics of disease transmission.

METHODS

From September 2012 to November 2012 and in November 2013, 911 blood-fed Cx. quinquefasciatus mosquitoes were collected with aspirators inside houses in Chetumal and Cancun. Blood meals were analysed by PCR and subsequent Sanger sequencing of the cytochrome b gene.

RESULTS

93.3% of mosquitoes fed on mammals, 6.5% on birds and 0.2% on reptiles. The most frequent vertebrate hosts were humans (65.4%), dogs (23.2%), chicken (5.4%), cattle (2.2%) and cats (1.8%).

CONCLUSIONS

Cx. quinquefasciatus most frequently fed on humans and dogs in both studied cities, which is in contrast to a previous study that demonstrated lower prevalence of mammalian blood in engorged Cx. quinquefasciatus.

Unraveling Host-Vector-Arbovirus Interactions by Two-Gene High Resolution Melting Mosquito Bloodmeal Analysis in a Kenyan Wildlife-Livestock Interface

The blood-feeding patterns of mosquitoes are directly linked to the spread of pathogens that they transmit. Efficient identification of arthropod vector bloodmeal hosts can identify the diversity of vertebrate species potentially involved in disease transmission cycles. While molecular bloodmeal analyses rely on sequencing of cytochrome b (cyt b) or cytochrome oxidase 1 gene PCR products, recently developed bloodmeal host identification based on high resolution melting (HRM) analyses of cyt b PCR products is more cost-effective. To resolve the diverse vertebrate hosts that mosquitoes may potentially feed on in sub-Saharan Africa, we utilized HRM profiles of both cyt b and 16S ribosomal RNA genes. Among 445 blood-fed Aedeomyia, Aedes, Anopheles, Culex, Mansonia, and Mimomyia mosquitoes from Kenya’s Lake Victoria and Lake Baringo regions where many mosquito-transmitted pathogens are endemic, we identified 33 bloodmeal hosts including humans, eight domestic animal species, six peridomestic animal species and 18 wildlife species. This resolution of vertebrate host species was only possible by comparing profiles of both cyt b and 16S markers, as melting profiles of some pairs of species were similar for either marker but not both. We identified mixed bloodmeals in a Culex pipiens from Mbita that had fed on a goat and a human and in two Mansonia africana mosquitoes from Baringo that each had fed on a rodent (Arvicanthis niloticus) in addition to a human or baboon. We further detected Sindbis and Bunyamwera viruses in blood-fed mosquito homogenates by Vero cell culture and RT-PCR in Culex, Aedeomyia, Anopheles and Mansonia mosquitoes from Baringo that had fed on humans and livestock. The observed mosquito feeding on both arbovirus amplifying hosts (including sheep and goats) and possible arbovirus reservoirs (birds, porcupine, baboons, rodents) informs arbovirus disease epidemiology and vector control strategies.

Stormwater drains and catch basins as sources for production of Aedes aegypti and Culex quinquefasciatus

We present data showing that structures serving as drains and catch basins for stormwater are important sources for production of the mosquito arbovirus vectors Aedes aegypti and Culex quinquefasciatus in Mérida City, México. We examined 1761 stormwater drains - located in 45 different neighborhoods spread across the city - over dry and wet seasons from March 2012 to March 2013. Of the examined stormwater drains, 262 (14.9%) held water at the time they were examined and 123 yielded mosquito immatures. In total, we collected 64,560 immatures representing nine species. The most commonly encountered species were Cx. quinquefasciatus (n=39,269) and Ae. aegypti (n=23,313). Ae. aegypti and Cx. quinquefasciatus were collected during all 11 months when we found water-filled stormwater drains, and both were found in stormwater drains located throughout Mérida City. We also present data for associations between structural characteristics of stormwater drains or water-related characteristics and the abundance of mosquito immatures. In conclusion, stormwater drains produce massive numbers of Ae. aegypti and Cx. quinquefasciatus across Mérida City, both in the wet and dry seasons, and represent non-residential development sites that should be strongly considered for inclusion in the local mosquito surveillance and control program.

Evaluation of seasonal feeding patterns of West Nile virus vectors in Bernalillo county, New Mexico, United States: implications for disease transmission

Many mosquito species take bloodmeals predominantly from either birds or mammals. Other mosquito species are less host-specific and feed readily on both. Furthermore, some species tend to alter their feeding patterns over the course of the year; early in the mosquito season such species may feed primarily on a particular host type, and subsequently take an increasingly larger proportion of their bloodmeals from an alternative host type as the season progresses. We have examined the feeding patterns of the three mosquito species found in Bernalillo County, NM: Culex quinquefasciatus (Say), Culex tarsalis (Coquillett), and Aedes vexans (Meigen). Specifically, we seek to determine if any of these species displays a seasonal shift in terms of its host utilization pattern. Our analysis focuses on these three species because they are all considered to be competent vectors for the West Nile virus (WNV). Our current data for Cx. quinquefasciatus suggest that unlike elsewhere in its range, this species increases its proportion of avian bloodmeals as the season progresses. Alternatively, Ae. vexans feeds primarily on mammals, whereas Cx. tarsalis appears to feed on both mammals and birds throughout the mosquito season. A more complete understanding of the feeding habits of these three mosquito species may help to clarify the transmission dynamics of WNV in Bernalillo County.

Culicidae (Diptera) selection of humans, chickens and rabbits in three different environments in the province of Chaco, Argentina

Studies were conducted to determine the selection of humans, chickens and rabbits by Culicidae in three different environments in the province of Chaco, Argentina. Mosquitoes were collected fortnightly using cylindrical metal traps containing animal bait (chickens and rabbits). The mosquitoes were collected between June 2001-May 2002. During the same period and with the same frequency, mosquitoes biting the human operators of the traps were collected during the first 15 min of exposure within different time intervals: from 09:00 am-11:00 am, 01:00 pm-03:00 pm, 05:00 pm-07:00 pm and 09:00 pm-10:00 pm. A total of 19,430 mosquitoes of 49 species belonging to 10 genera were collected. Culex species mainly selected chicken bait and Wyeomyia species selected rabbit bait. Ochlerotatus and Psorophora species were more abundant in rabbit-baited traps. Anopheles triannulatus, Coquillettidia nigricans, Ochlerotatus scapularis, Mansonia titillans and Psorophora albigenu showed a strong attraction for human bait. The Anopheles, Coquillettidia, Culex and Mansonia species were more active between 05:00 pm-09:00 pm, while Ochlerotatus, Psorophora, Haemagogus and Wyeomyia were most active from 09:00 am-07:00 pm. This study provides additional information about the biology and ecology of arbovirus vectors in Chaco.

Polymerase chain reaction detection of human host preference and Plasmodium parasite infections in field collected potential malaria vectors

This study was carried out to determine the human host preference and presence of Plasmodium parasite in field collected Anopheles mosquitoes among four villages around a military cantonment located in malaria endemic Sonitpur district of Assam, India. Encountered malaria vector mosquitoes were identified and tested for host preference and Plasmodium presence using PCR method. Human host preference was detected using simple PCR, whereas vectorial status for Plasmodium parasite was confirmed using first round PCR with genus specific primers and thereafter nested PCR with three Plasmodium species specific primers. Out of 1874 blood fed vector mosquitoes collected, 187 (10%) were processed for PCR, which revealed that 40·6% had fed on human blood; 9·2% of human blood fed mosquito were harbouring Plasmodium parasites, 71·4% of which were confirmed to Plasmodium falciparum. In addition to An. minimus, An. annularis and An. culicifacies were also found positive for malaria parasites. The present study exhibits the human feeding tendency of Anopheles vectors highlighting their malaria parasite transmission potential. The present study may serve as a model for understanding the human host preference of malaria vectors and detection of malaria parasite inside the anopheline vector mosquitoes in order to update their vectorial status for estimating the possible role of these mosquitoes in malaria transmission. The study has used PCR method and suggests that PCR-based method should be used in this entire malarious region to correctly report the vectorial position of different malaria vectors.

Identification of blood meal sources in Aedes vexans and Culex quinquefasciatus in Bernalillo County, New Mexico

Culex quinquefasciatus Say (Diptera: Culicidae) and Aedes vexans Meigen are two of the most abundant mosquitoes in Bernalillo County, New Mexico, USA. In this study, a polymerase chain reaction based methodology was used to identify the sources of blood meals taken by these two species. Ae. vexans was found to take a large proportion of its meals from mammals. Although less specific in terms of its blood meal preferences, Cx. quinquefasciatus was found to feed more commonly on birds. The results for Ae. vexans are similar to those reported for this species in other parts of their geographic range. Cx. quinquefasciatus appears to be more variable in terms of its host feeding under different environmental or seasonal circumstances. The implications of these results for arbovirus transmission are discussed.

"Bird biting" mosquitoes and human disease: a review of the role of Culex pipiens complex mosquitoes in epidemiology

The transmission of vector-borne pathogens is greatly influenced by the ecology of their vector, which is in turn shaped by genetic ancestry, the environment, and the hosts that are fed on. One group of vectors, the mosquitoes in the Culex pipiens complex, play key roles in the transmission of a range of pathogens including several viruses such as West Nile and St. Louis encephalitis viruses, avian malaria (Plasmodium spp.), and filarial worms. The Cx. pipiens complex includes Culex pipiens pipiens with two forms, pipiens and molestus, Culex pipiens pallens, Culex quinquefasciatus, Culex australicus, and Culex globocoxitus. While several members of the complex have limited geographic distributions, Cx. pipienspipiens and Cx. quinquefasciatus are found in all known urban and sub-urban temperate and tropical regions, respectively, across the world, where they are often principal disease vectors. In addition, hybrids are common in areas of overlap. Although gaps in our knowledge still remain, the advent of genetic tools has greatly enhanced our understanding of the history of speciation, domestication, dispersal, and hybridization. We review the taxonomy, genetics, evolution, behavior, and ecology of members of the Cx. pipiens complex and their role in the transmission of medically important pathogens. The adaptation of Cx. pipiens complex mosquitoes to human-altered environments led to their global distribution through dispersal via humans and, combined with their mixed feeding patterns on birds and mammals (including humans), increased the transmission of several avian pathogens to humans. We highlight several unanswered questions that will increase our ability to control diseases transmitted by these mosquitoes.

West Nile virus vector competency of Culex quinquefasciatus mosquitoes in the Galapagos Islands

The mosquito-transmitted pathogen West Nile virus (WNV) is not yet present in the Galápagos Archipelago of Ecuador. However, concern exists for fragile endemic island fauna after population decreases in several North American bird species and pathology in certain reptiles. We examined WNV vector competency of a Galápagos strain of mosquito (Culex quinquefasciatus Say). Field specimens were tested for their capacity to transmit the WN02-1956 strain of WNV after incubation at 27°C or 30°C. Rates of infection, dissemination, and transmission all increased with days post-exposure to WNV, and the highest rates were observed at 28 days. Infection rates peaked at 59% and transmission rates peaked at 44% (of mosquitoes tested). Vector efficiency increased after day 14. Rates of infection but not of transmission were significantly influence by temperature. No vertical transmission was detectable. We demonstrate that Galápagos Cx. quinquefasciatus are competent WNV vectors, and therefore should be considered an animal and public health risk for the islands and controlled wherever possible.

Mosquito infestation and dengue virus infection in Aedes aegypti females in schools in Merida, Mexico

We determined abundance of Aedes aegypti mosquitoes and presence of dengue virus (DENV) in females collected from schools in Mérida, México, during 2008 and 2009. Backpack aspiration from 24 schools produced 468 females of Ae. aegypti and 1,676 females of another human biter, Culex quinquefasciatus. Ae. aegypti females were collected most commonly from classrooms followed by offices and bathrooms. Of these females, 24.7% were freshly fed. Examination of 118 pools of Ae. aegypti females (total of 415 females) for presence of DENV RNA produced 19 positive pools (16.1%). DENV-infected pools were detected from 11 (45.8%) of 24 schools and came from different room types, including classrooms, offices, and bathrooms. The overall rate of DENV infection per 100 Ae. aegypti females was 4.8. We conclude that schools in Mérida present a risk environment for students, teachers, and other personnel to be exposed to mosquitoes and bites of DENV-infected Ae. aegypti females.