House Mosquito Culex Quinquefasciatus Research Articles

Influence of resource levels, organic compounds and laboratory colonization on interspecific competition between the Asian tiger mosquito Aedes albopictus (Stegomyia albopicta) and the southern house mosquito Culex quinquefasciatus.

The mosquitoes Aedes albopictus (Stegomyia albopicta) (Skuse) and Culex quinquefasciatus (Say) (Diptera: Culicidae) are common inhabitants of tyres and other artificial containers, which constitute important peridomestic mosquito breeding habitats. We tested the hypotheses that interspecific resource competition between the larvae of these species is asymmetrical, that the concentration of chemicals associated with decomposing detritus affects the competitive outcomes of these species, and that wild and colonized strains of Cx. quinquefasciatus are affected differently by competition with Ae. albopictus. We conducted two laboratory competition experiments wherein we measured survivorship and estimated population growth (λ') in both species under multiple mixed-species densities. Under varying resource levels, competition was asymmetrical: Ae. albopictus caused competitive reductions or exclusions of Cx. quinquefasciatus under conditions of limited resources. In a second experiment, which used both wild and colonized strains of Cx. quinquefasciatus, organic chemical compounds associated with decomposing detritus did not affect the competitive outcome. The colonized strain of Cx. quinquefasciatus had greater survivorship and adult mass, and faster development times than the wild strain, but both strains were similarly affected by competition with Ae. albopictus. Competition between these species may have important consequences for vector population dynamics, especially in areas in which tyres and artificial containers constitute the majority of mosquito breeding habitats.

Silent, generic and plant kairomone sensitive odorant receptors from the Southern house mosquito

The Southern house mosquito Culex quinquefasciatus has the largest repertoire of odorant receptors (ORs) of all mosquitoes and dipteran species whose genomes have been sequenced to date. Previously, we have identified and de-orphanized two ORs expressed in female antennae, CquiOR2 and CquiOR10, which are sensitive to oviposition attractants. In view of a new nomenclature for the Culex genome (VectorBase) we renamed these ORs as CquiOR21 (formerly CquiOR10) and CquiOR121 (CquiOR2). In addition, we selected ORs from six different phylogenetic groups for deorphanization. We cloned four of them by using cDNA from female antennae as a template. Attempts to clone CquiOR87 and CquiOR110 were unsuccessful either because they are pseudogenes or are not expressed in adult female antennae, the main olfactory tissue. By contrast, CquiOR1, CquiOR44, CquiOR73, and CquiOR161 were highly expressed in female antennae. To de-orphanize these ORs, we employed the Xenopus oocyte recording system. CquiORx–CquiOrco-expressed oocytes were challenged with a panel of 90 compounds, including known oviposition attractants, human and vertebrate host odorants, plant kairomones, and naturally occurring repellents. While CquiOR161 did not respond to any test compound in two different laboratories, CquiOR1 showed the features of a generic OR, with strong responses to 1-octen-3-ol and other ligands. CquiOR44 and CquiOR73 showed preference to plant-derived terpenoids and phenolic compounds, respectively. While fenchone was the best ligand for the former, 3,5-dimethylphenol elicited the strongest responses in the latter. The newly de-orphanized ORs may be involved in reception of plant kairomones and/or natural repellents.

Global spread and genetic variants of the two CYP9M10 haplotype forms associated with insecticide resistance in Culex quinquefasciatus Say

Insecticide resistance develops as a genetic factor (allele) conferring lower susceptibility to insecticides proliferates within a target insect population under strong positive selection. Intriguingly, a resistance allele pre-existing in a population often bears a series of further adaptive allelic variants through new mutations. This phenomenon occasionally results in replacement of the predominating resistance allele by fitter new derivatives, and consequently, development of greater resistance at the population level. The overexpression of the cytochrome P450 gene CYP9M10 is associated with pyrethroid resistance in the southern house mosquito Culex quinquefasciatus. Previously, we have found two genealogically related overexpressing CYP9M10 haplotypes, which differ in gene copy number (duplicated and non-duplicated). The duplicated haplotype was derived from the non-duplicated overproducer probably recently. In the present study, we investigated allelic series of CYP9M10 involved in three C. quinquefasciatus laboratory colonies recently collected from three different localities. Duplicated and non-duplicated overproducing haplotypes coexisted in African and Asian colonies indicating a global distribution of both haplotype lineages. The duplicated haplotypes both in the Asian and African colonies were associated with higher expression levels and stronger resistance than non-duplicated overproducing haplotypes. There were slight variation in expression level among the non-duplicated overproducing haplotypes. The nucleotide sequences in coding and upstream regions among members of this group also showed a little diversity. Non-duplicated overproducing haplotypes with relatively higher expression were genealogically closer to the duplicated haplotypes than the other non-duplicated overproducing haplotypes, suggesting multiple cis-acting mutations before duplication.

Characterization of Sudan strains of Bacillus thuringiensis pathogenic to the larvae of the house mosquito Culex quinquefasciatus

Mosquitoes, as blood sucking insects and vectors for several serious human diseases, continue to be one of the major threats to public health, comfort and economic growth in the Sudan and many other countries. Dengue, yellow fever, and filariasis in addition to malaria are all transmitted by mosquitoes; this pest is controlled using chemical pesticides. The increasing concern about the environment and the hazards resulting from the sole reliance on pesticides and the acquired resistance to one or multiple insecticides forced scientist to seek for safer efficient alternatives or supplements for the chemical pesticides. Bacillus thuringiensis is considered to be one of the important microbial control agents capable of producing insecticidal proteins with specific pathogenicity. In this study, different samples were obtained from soils collected from different locations in Sudan and from stored products dust and dead insects, in addition to mosquito rearing bonds, with the objective of isolating entomopathogenic Bacillus thuringiensis strains. Thirty nine strains were isolated and identified morphologically and biochemically and their toxicity to the house mosquito Culex quinquefasciatus second and third instar larvae was evaluated. The larvae of the house mosquito were introduced to sterile distilled water treated with 500 ppm concentration from each isolate. Significant differences existed between the isolates in their toxicity 42 hours post treatment, where mortality percentages ranged from 25% to 95% compared to 12.5% in the untreated control larvae. About 69% of the 39 Bt isolates were found pathogenic (mortality ≥50%) to the house mosquito larvae. Regression analysis revealed differences in the lethal times between the different isolates. The LT50 values varied from 29.38 hours for isolate Om-5 to 131.9956 hours for isolate GF-18. The practical significance of these findings for management of mosquitoes is discussed. It is therefore concluded that Sudan environment is rich in Bacillus thuringiensis pathogenic to the house mosquito and 5 isolates resulted in cumulative mortality percentages above 80%.

Anthropogenic habitat disturbance and ecological divergence between incipient species of the malaria mosquito Anopheles gambiae.

BackgroundAnthropogenic habitat disturbance is a prime cause in the current trend of the Earth’s reduction in biodiversity. Here we show that the human footprint on the Central African rainforest, which is resulting in deforestation and growth of densely populated urban agglomerates, is associated to ecological divergence and cryptic speciation leading to adaptive radiation within the major malaria mosquito Anopheles gambiae.Methodology/Principal FindingsIn southern Cameroon, the frequency of two molecular forms–M and S–among which reproductive isolation is strong but still incomplete, was correlated to an index of urbanisation extracted from remotely sensed data, expressed as the proportion of built-up surface in each sampling unit. The two forms markedly segregated along an urbanisation gradient forming a bimodal cline of ∼6-km width: the S form was exclusive to the rural habitat, whereas only the M form was present in the core of densely urbanised settings, co-occurring at times in the same polluted larval habitats of the southern house mosquito Culex quinquefasciatus–a species association that was not historically recorded before.Conclusions/SignificanceOur results indicate that when humans create novel habitats and ecological heterogeneities, they can provide evolutionary opportunities for rapid adaptive niche shifts associated with lineage divergence, whose consequences upon malaria transmission might be significant.

Southern House Mosquito Culex quinquefasciatus Say

EENY457, a 6-page illustrated fact sheet by Stephanie Larrick and Roxanne Connelly, is part of the Featured Creatures collection. It describes this medium-sized brown mosquito that exists throughout the tropics and the lower latitudes of temperate regions and is a vector of many pathogens, several of which affect humans — synonymy, distribution, description, life cycle, medical importance, and management. Includes references. Published by the UF Department of Entomology and Nematology, November 2009. EENY457/IN837: Southern House Mosquito Culex quinquefasciatus Say (ufl.edu)

Lethal and sublethal responses of an aquatic insect Culex quinquefasciatus (Diptera: Culicidae) challenged with individual and joint exposure to dissolved sodium selenate and methylmercury chloride

Pollutants rarely occur alone in the natural environment, and few studies have focused on the potential interactions between metals or metalloids. In this study an aquatic insect, the southern house mosquito (Culex quinquefasciatus: Diptera), was used to test the individual and joint effects of dissolved sodium selenate (Se) and methyl mercury chloride (MeHg). We conducted ovipositional preference tests and 14-day chronic toxicity studies to determine lethal and sublethal responses of C. quinquefasciatus to a range of Se and MeHg concentrations and mixtures. No evidence was found for female ovipositional preference in field trials using artificial ponds. Larvae were more sensitive to MeHg than Se, with LC(50) values of 30 microg/L (CI = 28-31 microg/L) and 11 mg/L (CI = 10-12 mg/L) respectively. In addition, larval survival was significantly reduced at concentrations as low as 25 microg/L of MeHg and 8 mg/L of Se. A synergistic interaction was observed in the toxicity of the Se-MeHg mixtures to C. quinquefasciatus larvae. Larval mosquito survival was significantly reduced at 7.5 microg/L MeHg + 2.75 mg/L Se and an LC(50) value of 9 microg/L MeHg + 3.4 mg/L Se was determined for a fixed ratio mixture. The rate of growth of the larvae was analyzed using a Growth Index that provided a sensitive measure of the developmental effects of toxicant exposure. Sodium selenate at concentrations as low as 2 mg/L caused a significant decrease in growth between larvae in treatment versus control solutions after only 4 days. Similarly, MeHg at concentrations as low as 25 microg/L and a Se-MeHg mixture of 3 microg/L MeHg plus 1.1 mg/L Se caused significant growth reductions after only 2 and 3 days, respectively. These are the first reported survival and developmental data for an aquatic insect exposed to MeHg and Se-MeHg mixtures.

PATHWAYS OF EXPANSION AND MULTIPLE INTRODUCTIONS ILLUSTRATED BY LARGE GENETIC DIFFERENTIATION AMONG WORLDWIDE POPULATIONS OF THE SOUTHERN HOUSE MOSQUITO

The southern house mosquito Culex quinquefasciatus is a principal vector of human lymphatic filariasis, several encephalitides (including West Nile virus), avian malaria, and poxvirus, but its importance as a vector varies considerably among regions. This species has spread with humans and is ubiquitous in tropical urban and suburban environments. This was the first mosquito to reach Hawaii and we performed a worldwide genetic survey using micro-satellite loci to identify its source. Our analyses showed divergent Old World and New World genetic signatures in Cx. quinquefasciatus with further distinctions between east and west African, Asian, and Pacific populations that correlate with the epidemiology of human filariasis. We found that in Hawaii south Pacific mosquitoes have largely replaced the original New World introduction of Cx. quinquefasciatus, consistent with their reported expansion to higher elevations. We hypothesize worldwide pathways of expansion of this disease vector.

Molecular characterization of the amplified aldehyde oxidase from insecticide resistant Culex quinquefasciatus.

Primary structural information including the complete nucleotide sequence of the first insect aldehyde oxidase (AO) was obtained from the common house mosquito Culex quinquefasciatus (Say) through cloning and sequencing of both genomic DNA and cDNA. The deduced amino-acid sequence encodes a 150-kDa protein of 1266 amino-acid residues, which is consistent with the expected monomeric subunit size of AO. The Culex AO sequence contains a molybdopterin cofactor binding domain and two iron-sulfur centres. A comparison of the partial sequences of AO from insecticide resistant and susceptible strains of C. quinquefasciatus shows two distinct alleles of this enzyme, one of which is amplified in the insecticide resistant strain on a 30-kb DNA amplicon alongside two resistance-associated esterases. The amplified AO gene results in elevated AO activity in all life stages, but activity is highest in 3rd instar larvae. The elevated enzyme can be seen as a separate band on polyacrylamide gel electrophoresis. The role of AO in xenobiotic oxidation in mammals and the partial inhibition of elevated AO activity by a range of insecticides in Culex, suggest that this AO may play a role in insecticide resistance.

Amplification of a xanthine dehydrogenase gene is associated with insecticide resistance in the common house mosquito Culex quinquefasciatus.

Conference Article| August 01 1997 Amplification of a xanthine dehydrogenase gene is associated with insecticide resistance in the common house mosquito Culex quinquefasciatus MICHAEL COLEMAN; MICHAEL COLEMAN 1School of Pure and Applied Biology, University of Wales Cardiff, PO Box 915, Cardiff CF1 3TL, United Kingdom Search for other works by this author on: This Site PubMed Google Scholar JANET HEMINGWAY JANET HEMINGWAY 1School of Pure and Applied Biology, University of Wales Cardiff, PO Box 915, Cardiff CF1 3TL, United Kingdom Search for other works by this author on: This Site PubMed Google Scholar Biochem Soc Trans (1997) 25 (3): 526S. https://doi.org/10.1042/bst025526s Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter LinkedIn Cite Icon Cite Get Permissions Citation MICHAEL COLEMAN, JANET HEMINGWAY; Amplification of a xanthine dehydrogenase gene is associated with insecticide resistance in the common house mosquito Culex quinquefasciatus. Biochem Soc Trans 1 August 1997; 25 (3): 526S. doi: https://doi.org/10.1042/bst025526s Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsBiochemical Society Transactions Search Advanced Search This content is only available as a PDF. © 1997 Biochemical Society1997 Article PDF first page preview Close Modal You do not currently have access to this content.

Acylated 1,3-Aminopropanols as Repellents against Bloodsucking Arthropods

Starting from a set of known repellent compounds, a general structural framework with high probability for repellent activity was developed by molecular modelling techniques. Synthesis, structure–biological activity relationships of acylated 1,3-aminopropanols on the yellow fever mosquito Aedes aegypti and the properties and activity of the new development candidate compound KBR 3023 on Ae. aegypti, the malaria mosquito Anopheles stephensi, the common house mosquito Culex quinquefasciatus and the stable fly Stomoxys calcitrans are described. The sensory effect of KBR 3023 and deet has been studied in behavioural and neurophysiological investigations on Ae. aegypti and the American cockroach Periplaneta americana. The compounds clearly reduce or even eliminate the approach behaviour towards attractants like host odours or sexual pheromones. Electrophysiological studies on the insects' olfactory receptor organs reveal that certain cell types, which are not involved in perception of the attractive odorants, respond to deet and/or KBR 3023. As soon as one of the compounds is presented together with an attractant, a new input is active in the brain, which adds to the input from other receptors activated by the attractant. This new overall pattern clearly differs from that elicited by the attractant, so that the insect is no longer able to detect the latter. The specificity and mode of action of KBR 3023 was investigated by experiments exploring second-messenger responses elicited in antennal preparations of male P. americana. KBR 3023 induced a rapid increase in the concentration of inositol triphosphate in a dose-dependent and tissue-specific manner; other second-messenger systems were not affected. These observations suggest that KBR 3023 may act via subsets of G-protein-coupled receptors in sensory neurones.

Culturing Culex quinquefasciatus mosquitoes with a blood substitute diet for the females.

The tropical house mosquito Culex quinquefasciatus was cultured by feeding the females on an artificial diet, not on live animals or whole blood. This anautogenous strain has been maintained for more than fifty generations. The blood replacement diet for female mosquitoes, designed to simulate the tonicity and density of host blood, was based on ovalbumin, soya infant formula, globulins and adenosine triphosphate. Female adults of Cx quinquefasciatus were fed the artificial blood formula from "Parafilm' wax membrane-covered beakers. The diet was heated by radiant heat from a chamber containing an exothermic chemical reaction. This maintained the diet at a temperature of 33-37 degrees C for a period of up to 6 h, sufficient time to enable all the female mosquitoes to imbibe to satiation. After six generations on the artificial diet, female fecundity stabilized to a satisfactory level: the number of eggs per gonotrophic cycle averaged c. 85% of the "control' strain fed on whole blood from live anaesthetized guineapigs, i.e. 156 eggs per female from nine feeds on the artificial diet compared with 183 from six feeds of whole blood. Adult weight of Cx quinquefasciatus females was not significantly different, from generation 6 onwards, for strains fed on artificial diet or whole blood. Sex ratio and the rate of egg viability were also equivalent for the two strains.

Purification and characterization of carboxylesterases of a rice brown planthopper, Nilaparvata lugens Stål

More than 10 molecular forms of carboxylesterases were observed with α-naphthyl acetate as substrate in a rice brown planthopper (BPH), Nilaparvata lugens Stål, using isoelectric focusing. The three most active ones, E 1, E 2 and E 3, purified with gel permeation/chromatofocusing chromatography were characterized. Their subunit molecular mass varied between 62 and 64 kDa and the pI ranged from c.4.7 to 4.9. They were immunologically related and showed no difference in sensitivity toward the inhibition of paraoxon, methyl paraoxon, and malaoxon. E 1 consistently exhibited much higher activity than the other two isozymes toward some model substrates, i.e. α-naphthyl acetate and butyrate, β-naphthyl acetate, and 4-nitrophenyl acetate as well as some insecticides. While malathion and trans-permethrin were readily hydrolyzed by these isozymes, very limited or no degradation of cypermethrin and cis-permethrin was detected. The carboxylesterases of BPH, being unable to hydrolyze parathion, could bind strongly the potent anticholinesterase paraoxon and oxons of several organophosphorus insecticides, rendering them nontoxic. Resistant BPH had higher activity and quantity of carboxylesterases (notably E 1) than susceptible BPH. Protein subunits immunologically related to E 1 of BPH were detected in two other rice planthoppers ( Laodelphax striatellus and Sogatella furcifera) and two aphids ( Myzus persicae and Aphis gossypii), but not in the green rice leafhopper ( Nephotettix cincticeps) and southern house mosquito ( Culex quinquefasciatus).

Circulating Precipitating Antibodies in the Rabbit from Mite Infection as Shown by Agar-Gel Tests

In agar-gel tests, extracts of Psoroptes cuniculi (Delafond), against the sera of rabbits with ear canker, a disease caused by this mite, resulted in precipitation bands indicating at least two antigenantibody systems. Agar-gel double diffusion techniques can be used to show antigen-antibody systems resulting from natural infection of man and animals with helminth parasites (Kagan and Norman, 1963). But antibodies naturally produced against different species of arthropods when they invade the tissues, suck blood, inject venom, or act as allergens have not heretofore been demonstrated by such methods (Langlois et al., 1963). Blacklock et al. (1930) first demonstrated precipitins in guinea pigs to insect parasites. Little progress seems to have been made since that time. This paper reports results with agar-gel tests which confirm those of Culbertson (1935) obtained by the ring test. MATERIALS AND METHODS The serum samples came from rabbits involved in an outbreak of ear canker, scab, or psoroptic mange in the animal houses of two separate institutions. It was acquired and spread naturally, without deliberate human intervention. In all, sera from 25 rabbits exposed to the epidemic, including clean rabbits as well as scabby ones were studied. Of these, two rabbits were severely affected as follows. The first case, G-7, was a small extremely thin animal weighing 3 to 4 lb. Thick, dry grayishbrown crusts completely filled both ear canals and extended over both surfaces of the ears without interruption (Fig. 1). The remainder of the body was covered with the same type of exudate. The thickness of the crust varied from approximately 0.75 to 1.0 cm over the head, back, and feet to about 2 mm over the abdomen. Many mites were seen on the bare surface of the skin after removal of the scabs and hair. The other severe case, rabbit No. 4 had extensive crusts in both ears with large quantities of grayish yellowish odorous pus. Received for publication 8 August 1966. * This investigation was supported in part by Research Grant AI-03821 and Graduate Research Training Grant 5-T1 AI 15 from the NIAID, U. S. Public Health Service. Two large abscesses below the right ear were opened and drained. Swabs were made and scabs collected for bacterial and fungal cultures. Mites were recovered from the scabs and identified. Scabs from rabbit G-7 were put in 250-ml beakers each containing about 100 ml of merthiolated physiological saline. Three such beakers were filled and stored in the freezer. Later pieces of the material were thawed and searched for mites using a stereoscopic microscope. Literally thousands of specimens of the scab mite Psoroptes cuniculi (Delafond) were found. There were also some specimens of Notoedres cati (Hering) (-Sarcoptes cuniculi Gerlach, according to Lavoipierre, 1964) and Listrophorus gibbus Pagenstecher, but they were not sufficiently abundant to be used in this study. Extracts of Psoroptes cuniculi were prepared directly without lyophilization. Large mature specimens were removed with forceps, weighed, and homogenized in saline solution with merthiolate at 1:5,000 in a tissue grinder to give dilutions at 1:5 and 1:10. About 1,200 specimens weighed 30 mg which when diluted in 0.3 ml (300 , liters) of saline provided sufficient extract at 1:10 to make six agar-gel slides. More than 40,000 specimens were obtained from rabbit G-7, enough material to provide extracts for most of the tests. The bacteria Pseudomonas aeruginosa, Proteus species, Diphtheroid species, and Staphylococcus aureus were cultured on blood agar, and Aspergillus species was cultured on Sabouraud dextrose agar from the material obtained from rabbit No. 4. Extracts were made of each of these by scraping the agar, weighing, homogenizing in a hand tissue grinder, and diluting 1:10 in merthiolate saline without the intention of disrupting or disintegrating the bacteria and mold. Extracts of adult females of the yellow fever mosquito, Aedes aegypti and the southern house mosquito Culex quinquefasciatus were made from material obtained from laboratory colonies (Fox et al., 1963). A laboratory colony also provided the material for extracts of the domestic rat mite, Laelaps nuttalli Hirst. For agar-gel tests, the microslide technique of Yakulis and Heller (1959) was used with SeaKem( Agarose.