The relative attractiveness of carbon dioxide and octenol in CDC- and EVS-type light traps for sampling the mosquitoes Aedes aegypti (L.), Aedes polynesiensis Marks, and Culex quinquefasciatus say in Moorea, French Polynesia.

Two dominant day-biting pests and vector species on the island of Moorea in French Polynesia are Aedes (Stegomyia) aegypti (L.) and Aedes (Stegomyia) polynesiensis Marks, major vectors of dengue viruses and Wuchereria bancrofti, respectively. Their surveillance is hindered by a relative lack of attraction to light traps, necessitating the undesirable use of human bait collections with the inherent risks of pathogen transmission. The effectiveness of CDC- and EVS-type light traps baited with olfactory attractants was evaluated for these two Aedes species and the nocturnal Culex (Culex) quinquefasciatus Say in three sites in urban and semi-rural environments on Moorea in October/November 2003. Firstly, four CDC-type traps with light only, light with octenol, light with carbon dioxide (dry ice), and light with octenol plus carbon dioxide were operated continuously over four days with daily rotation to compensate for position effects. Secondly, two CDC- and two EVS-type traps with carbon dioxide or carbon dioxide plus octenol were operated continuously over four days with similar rotation. Variation was found in the numbers of the three species collected at the different sites, reflecting the relative availability of their preferred larval habitats. With the CDC traps in the first trial, the addition of octenol to the light did not significantly increase the collection of any species, the addition of carbon dioxide did significantly increase collection of all three species, while the addition of octenol to the light plus carbon dioxide did not significantly increase the collections further. In the second trial, there was no significant difference in the mean number of Ae. aegypti or Ae. polynesiensis collected in either EVS or CDC traps when baited with carbon dioxide or with octenol added. For Cx. quinquefasciatus, the supplementation with octenol made no significant difference with EVS traps but resulted in significantly reduced collections in CDC traps. Overall, neither trap, however baited, provided large samples when compared with landing/ biting collections at human bait. Only two other species were collected, Culex (Culex) roseni Belkin and Aedes (Aedimorphus) nocturnus (Theobald), the latter being a first record for the island of Moorea and for French Polynesia.     

Daily patterns of locomotor and sugar-feeding activity of the mosquito Culex annulirostris from geographically isolated populations

Abstract.  The daily patterns of locomotor and sugar-feeding activity of virgin female Culex annulirostris from three regions in Australia and a laboratory colony are studied using video techniques in the laboratory. Although all populations display a crepuscular/nocturnal locomotor pattern, significant variation exists between populations, with the pattern of those from southern Australia differing markedly from those in central and northern Australia. It is hypothesized that adaptation of populations to local climates is responsible. Sugar-feeding (inferred from landing on a sugar source) is mostly crepuscular/nocturnal in all populations. The behavioural variation that exists within wide-ranging mosquito species is highlighted, and indicates that significant behavioural differences exist between laboratory colonies and wild-types.     

Diurnal periodicity of fight in some Delphacidae and Cicadellidae associated with rice

Abstract. 1. The diurnal periodicity of flight of delphacids and cicadellids associated with rice was assessed by suction trapping.
2. All the delphacids examined and most cicadellids showed a bimodal, crepuscular pattern of flight, the major peak occurring in the evening.
3. Some cicadellids showed a unimodal crepuscular pattern of flight activity with the peak occurring in the evening, whereas flight activity of Cofana spectra and Cunimaculata continued throughout the night.
4. Changes in the periodicity of flight activity of Nilaparvata lugens, Sogatella furcifera, Recilia dorsalis and Macrosteles striifrons were observed in relation to phases of the moon and the nature of the habitat.
5. Periodicity of take-off for N.lugens, Sfurcifera and R.dorsalis assessed by canopy net traps also showed a bimodal, crepuscular pattern with the major peak occurring in the evening.
6. The significance of diurnal periodicity is discussed in relation to the flight behaviour of the insects studied.     

Transmission efficiency of Culex quinquefasciatus and Aedes aegypti to Wuchereria bancrofti infection: an experimental study

Present study was undertaken to evaluate the suitability of natural (Culex quinquefasciatus) and experimental (Aedes aegypti) vectors for supporting the development of W. bancrofti larvae for onward transmission. Both the species permitted development of W. bancrofti mf to infective larvae (L3) within 11 to 13 days. The mf intake by both the species of mosquitoes was directly related to mf density in donor's blood. Culex exhibited higher L3 recovery than Aedes. In Aedes maximum percent L3 development occurred after ingesting 4 mf whereas Culex exhibited best establishment at an average mf intake of 11.5. Nevertheless wide variation in mf density in donor's blood did not significantly affect the larval establishment in Aedes mosquito while in Culex very high (> 400 mf/40 microliters) or low (< 50 mf/40 microliters) mf counts in donor's blood adversely affected the L3 recovery. The results reveals that A. aegypti has an edge over the natural vector, Culex in being a voracious feeder, their easy laboratory maintenance and better transmission potential.     

Biological control of container-breeding mosquitoes, Aedes albopictus and Culex quinquefasciatus, in a Japanese island by release of Toxorhynchites splendens adults

To control container-breeding mosquitoes in the small island of Minnajima (0.56 km2), northern Okinawa, Japan, laboratory-reared adults (aged 7-10 days) of Toxorhynchites splendens (Palawan strain), a mosquito with predatory larvae, were released repeatedly during 1984, 1986 and 1987. Thirteen species of mosquitoes (Diptera: Culicidae) occurred in artificial containers, ground pools or crab-holes on the island, the predominant species being Aedes (Stegomyia) albopictus and Culex (Culex) quinquefasciatus. Predatory mosquito larvae of Culex (Lutzia) fuscanus and Cx (Lt.) halifaxii were found commonly in wet containers. In the first year of study, during a period of 54 days from 13 May to 5 July 1984, totals of 879 female and 806 male adults of Tx.splendens were released on six occasions. Similarly, between 29 April and 30 August 1986, totals of 2920 female and 2878 male adult Tx.splendens were released. In the third study year, totals of 2041 female and 1783 male Tx.splendens were released on eight occasions during 199 days from 23 April to 7 November 1987. After adult releases at two sites, the immature stages of Tx.splendens were found in 164 out of 502 traps in 1984, 421 out of 933 traps in 1986, and 151 out of 502 traps in 1987. The number of immatures of Tx.splendens present in each trap varied from 1 to 40 in 1984, 1 to 29 in 1986 and 1 to 9 in 1987. Numbers of immatures of the target species found in the traps during August-September averaged 71.9/trap/month in 1984, 114.7/trap/month in 1986 and 36.0/trap/month in 1987, significantly less in the traps with Tx.splendens than in those without them. The present field studies indicated that, in this small island, approximately 250 adult female and 200 male Tx.splendens per month should be released from April to November, and the releases should be carried out every year, in order to control effectively the target mosquitoes Ae.albopictus and Cx quinquefasciatus breeding in artificial containers in Minnajima.     

Alternative splicing generates multiple transcripts of the inhibitor of apoptosis protein 1 in Aedes and Culex spp. mosquitoes

We determined the sequences of cDNA encoding Inhibitor of Apoptosis Protein 1 (IAP1) homologues from Aedes triseriatus, Aedes albopictus, Aedes aegypti, Culex pipiens and Culex tarsalis. The cDNAs encode translation products that share > or = 84% sequence similarity. The IAP1 mRNA of each mosquito species exists as 3-5 distinct variants due to the presence of heterogeneous sequences at the distal end of their 5'UTRs. Partial genomic sequencing upstream of the 5' end of the Ae. triseriatus IAP1 gene, and analysis of the Ae. aegypti genomic sequence, suggest that these mRNA variants are generated by alternative splicing. Each IAP1 mRNA variant from Ae. triseriatus and Cx. pipiens was detected by RT-PCR in all mosquito life-stages and adult tissues examined, and the relative concentration of each Ae. triseriatus IAP mRNA variant in various tissues was determined.     

The effect of predatory fish exudates on the ovipostional behaviour of three mosquito species: Culex quinquefasciatus, Aedes aegypti and Culex tarsalis

Abstract.  Three mosquito species, Culex tarsalis Coquillett, Culex quinquefasciatus Say and Aedes aegypti L. (Diptera: Culicidae), were examined in laboratory binary choice experiments to investigate whether fish exudates from the mosquitofish, Gambusia affinis (Baird & Girard) (Cyprinodontiformes: Poecilliidae), deter oviposition and whether the responses of these mosquito species to fish exudates in oviposition sites are consistent with the risk of predation from fish experienced by each species in their respective natural breeding habitats. Culex tarsalis was deterred significantly from egg laying by the presence of fish exudates in oviposition cups, consistent with high levels of predation by fish in natural breeding sites. Egg laying by Cx quinquefasciatus was slightly reduced in water with fish exudates, but was not consistently deterred by water conditioned by mosquitofish, consistent with the species' relatively low risk of fish predation in natural habitats. Oviposition by container-breeding Ae. aegypti was not deterred by the presence of fish exudates in oviposition cups, consistent with a low risk of predation by fish in natural habitats.     

Repellent efficacy and safety evaluation of IR3535 derivative against Aedes albopictus,Culex pipiens pallens and Aedes togoi

The IR3535 derivative (LJH158), in which the ethyl ester of IR3535 was converted to methyl ester, was synthesized and studied as a new mosquito repellent. The repellent efficacy of LJH158 was compared with that of DEET against Aedes albopictus, Culex pipiens pallens and Aedes togoi. Also, the aromatic repellent tests were conducted with mixtures of repellents and the essential oils of cinnamon, which were obtained by supercritical fluid extraction. In addition, the safety issues of LJH158 were monitored using single oral dose safety methods and eye irritation, and skin irritation tests. The results of repellent efficacy in both biting and aromatic tests and safety tests demonstrate that LJH158 has high potential to be used as a new repellent or in combination with other repellents.     

Enantiomeric selectivity in behavioural and electrophysiological responses of Aedes aegypti and Culex quinquefasciatus mosquitoes

1-Octen-3-ol is a kairomone for many haematophagous insects including mosquitoes. Numerous studies have examined the effects of racemic 1-octen-3-ol; however, few studies have investigated the role of individual enantiomers in relation to mosquito attraction. In the present study, we investigated the behavioural and electrophysiological responses of two mosquito species, Aedes aegypti and Culex quinquefasciatus, to individual enantiomers and mixtures of 1-octen-3-ol, employing a laboratory Y-tube olfactometer and single sensillum recordings. The olfactory receptor neurons of both Ae. aegypti and Cx. quinquefasciatus had a significantly higher response to the (R)-1-octen-3-ol enantiomer compared to the (S)-1-octen-3-ol enantiomer at 10-9 g μl-1 to 10-6 g μl-1. Behaviourally, Ae. aegypti was more responsive to the (R)-1-octen-3-ol enantiomer, showing an increase in flight activity and relative attraction compared to Cx. quinquefasciatus. The (R)-1-octen-3-ol enantiomer caused an increase in activation for Cx. quinquefasciatus. However, the most notable effect was from an (R:S)-1-octen-3-ol mixture (84:16) that caused significantly more mosquitoes to sustain their flight and reach the capture chambers (demonstrated by a reduced non-sustained flight activity), suggesting that it may have a behaviourally excitatory effect. For Cx. quinquefasciatus, a reduced relative attraction response was also observed for all treatments containing the (R)-1-octen-3-ol enantiomer, either on its own or as part of a mixture, but not with the (S)-1-octen-3-ol enantiomer. This is the first time enantiomeric selectivity has been shown for Ae. aegypti using electrophysiology in vivo. The implications of these results for exploitation in mosquito traps are discussed.     

Insecticidal, repellent and oviposition-deterrent activity of selected essential oils against Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus

Essential oils extracted from 10 medicinal plants were evaluated for larvicidal, adulticidal, ovicidal, oviposition-deterrent and repellent activities towards three mosquito species; Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus. The essential oils of Juniperus macropoda and Pimpinella anisum were highly effective as both larvicidal and ovicidal. The essential oil of P. anisum showed toxicity against 4th instar larvae of A. stephensi and A. aegypti with equivalent LD95 values of 115.7 microg/ml, whereas it was 149.7 microg/ml against C. quinquefasciatus larvae. Essential oils of Zingiber officinale and Rosmarinus officinalis were found to be ovicidal and repellent, respectively towards the three mosquito species. The essential oil of Cinnamomum zeylanicum resulted into highest repellent (RD95) values of 49.6, 53.9 and 44.2 mg/mat against A. stephensi, A. aegypti and C. quinquefasciatus, respectively apart from oviposition-deterrent potential.     

Blood-feeding in mosquitoes: probing time and salivary gland anti-haemostatic activities in representatives of three genera (Aedes, Anopheles, Culex)

Mosquitoes (Diptera: Culicidae) face their hosts' haemostatic mechanisms when attempting to feed on blood. Accordingly, they antagonize haemostasis by salivary agents that include anti-clotting, anti-platelet and vasodilatory compounds. Because haemostasis is a complex and redundant physiological response that varies between vertebrates, it is to be expected that haematophagous animals have a salivary armoury that most efficiently counteracts their preferred hosts. The mosquito Culex quinquefasciatus Say, which has a strong tendency to ornithophagy, appears to have only recently adapted to mammals and may not have evolved efficient mechanisms to counteract mammalian platelet responses, while birds only have relatively inefficient thrombocytes. Accordingly, we compared the probing behaviour of Cx. quinquefasciatus with two other mosquito species from different backgrounds: Aedes aegypti (L.) and Anopheles albimanus Weidemann, that have apparently had a longer evolutionary association with mammals. Culex takes much more time to find blood on a mammalian host (human or mouse) when compared to the two other mosquito species, but does not differ in probing behaviour when feeding on a chicken. Salivary anti-haemostatic components were also measured in those three species of mosquito and results are discussed in context with the probing behaviour.     

Behavioral responses of Aedes aegypti,Aedes albopictus,Culex quinquefasciatus,and Anopheles minimus against various synthetic and natural repellent compounds

The behavioral responses of colony populations of Aedes aegypti, Aedes albopictus, Culex quinquefasciatus, and Anopheles minimus to four essential oils (citronella, hairy basil, catnip, and vetiver), two standard repellents (DEET and picaridin), and two synthetic pyrethroids (deltamethrin and permethrin) were conducted in the laboratory using an excito‐repellency test system. Results revealed that Cx. quinquefasciatus and An. minimus exhibited much stronger behavioral responses to all test compounds (65–98% escape for contact, 21.4–94.4% escape for non‐contact) compared to Ae. aegypti (3.7–72.2% escape (contact), 0–31.7% (non‐contact)) and Ae. albopictus (3.5–94.4% escape (contact), 11.2–63.7% (non‐contact)). In brief, essential oil from vetiver elicited the greatest irritant responses in Cx. quinquefasciatus (96.6%) and An. minimus (96.5%) compared to the other compounds tested. The synthetic pyrethroids caused a stronger contact irritant response (65–97.8% escape) than non‐contact repellents (0–50.8% escape for non‐contact) across all four mosquito species. Picaridin had the least effect on all mosquito species. Findings from the current study continue to support the screening of essential oils from various plant sources for protective properties against field mosquitoes.     

Repellent efficacy of wood vinegar against Culex pipiens pallens and Aedes togoi (Diptera: Culicidae) under laboratory and semi-field conditions

The repellent efficacy of wood vinegar was assessed against mosquitoes under laboratory conditions at 1, 5, 10, 20, 40, 60 and 80% concentrations. The study evaluated whether wood vinegar is able to repel Culex pipiens pallens Coquillet and Aedes togoi (Theobald) from the human body and if so at what concentrations. The tests were conducted using the arm-in-cage method in 80 × 40 × 40 cm screened mosquito cages. The data were analyzed and compared with those of N,N-Diethyl-3-methylbenzamide (deet) at 10.3% concentration. The results showed that wood vinegar provided mosquito repellence of varying degree depending on the concentration used. The observed repellence averaged from as low as 39.6% at 5.0% concentration to as high as 100% at 80% concentration against Ae. togoi. Repellence against Cx. pipiens pallens was high being 90.3% at 20% concentration, 92.2% at 40% concentration, 93.9% at 60% concentration and 100% at 80% concentration. The duration of protection time tests showed that the 40% and 60% concentrations of the wood vinegar give protection from landing of Ae. togoi for a period of up to 7 h, though the lower concentration gave lower protection after the first five hours. The results indicated that wood vinegar has mosquito repellent characteristics that tend to vary with the concentration used and the species of mosquitoes. Wood vinegar in this case was very effective in repelling Cx. pipiens pallens, even at lower concentrations while higher concentrations were required to repel Ae. togoi.     

Evaluation of collection methods for Culex quinquefasciatus,Aedes aegypti,and Aedes simpsoni in northeastern Tanzania

In East Africa, significant morbidity and mortality are caused by infections spread by Culex quinquefasciatus and Aedes aegypti. Sticky traps have been shown to be effective tools for sampling populations of Aedes mosquitoes and have been found to catch Cx. quinquefasciatus. Thus, they could potentially be used to sample populations of this species. This study compared Sticky ovitraps (SO) and MosquiTraps (MQT) with the CDC Gravid trap (CDC‐GT) for collection of Culex and Aedes mosquito populations in Tanzania. A follow‐up experiment was carried out using traps set for a 24‐h period to accommodate the oviposition habits of Aedes aegypti and Ae. simpsoni s.l. mosquitoes. The results showed that the CDC‐GT caught significantly more Cx. quinquefasciatus and Ae. aegypti than the SO or MQT, but there was no significant difference in the number of mosquitoes caught between the two sticky traps or of Ae. simpsoni s.l. caught among the three trap types. The results suggest that CDC‐GTs are the most appropriate in sampling of Cx. quinquefasciatus. Although CDC‐GTs collected more Ae. aegypti than the sticky traps, the simplicity and cost benefit of sticky traps facilitates large scale studies. All three trap types should be considered for monitoring Aedes mosquitoes.     

First report of the oriental mosquito Aedes albopictus on the West African island of Bioko,Equatorial Guinea

The invasive oriental mosquito Aedes (Stegomyia) albopictus (Skuse) (Diptera: Culicidae) was detected on Bioko Island for the first time in November 2001. It was found to be well established breeding in artificial containers at Planta, near Malabo, the capital of Equatorial Guinea. Associated species of mosquito larvae were Aedes aegypti (L.), Ae. africanus (Theobald), Culex near decens Theobald, Cx. duttoni Theobald, Cx. quinquefasciatus Say, Cx. tigripes De Grandpré & De Charmoy, Eretmapodites quinquevittatus Theobald and Mansonia africana (Theobald). This is the third tropical African country to be invaded by Ae. albopictus, which has recently spread to many parts of the Americas and Europe--with vector competence for dengue, yellow fever and other arboviruses. In the Afrotropical environment, it will be interesting to monitor the ecological balance and/or displacement between introduced Ae. albopictus and indigenous Ae. aegpyti (domestic, peri-domestic and sylvatic populations).     

Aquatain AMF efficacy on juvenile mosquito stages in control of Culex pipiens complex and Aedes albopictus

Aquatain^® mosquito formulation (AMF) is a silicone-based monomolecular film, which has recently been approved for use in the European Union. The physical mode of action based on lowering water surface tension prevents mosquito larvae/pupae respiration. Additionally, AMF disables gravid females from landing on the water surface and obstructs the natural oviposition process. Due to multistage effects on mosquitoes, AMF could be a product of choice for defined water body and container breeders such as Culex pipiens L. complex, principal vector of West Nile virus in Europe, and the invasive Aedes albopictus (Skuse) (both Diptera: Culicidae), vector of dengue and chikungunya viruses. The primary objectives of this study were to evaluate the efficacy of AMF, to determine the susceptibility of the immature forms of C. pipiens and A. albopictus, and the persistence/longevity of the product to suppress the eclosion of adults. AMF achieved high mortality rates of juvenile A. albopictus and C. pipiens under laboratory conditions. However, in the field C. pipiens larvae showed higher susceptibility to AMF than A. albopictus. Pupae of the two mosquito species were highly susceptible to the presence of AMF. When C. pipiens juveniles were exposed to AMF in the wild, effects lasted for 21 days in densely covered water bodies and 56 days in water recipients with less vegetation. In both breeding sites, natural habitat and artificial water recipient, the two mosquito species with high impact on public health in Europe could successfully be suppressed by application of AMF (1 ml m⁻²).     

Incrimination of the mosquito,Aedes taeniorhynchus,as the primary vector of heartworm,Dirofilaria immitis,in coastal Yucatan,Mexico

Mosquito collections were carried out on microfilaraemic dogs, positive for Dirofilaria sp., for 18 consecutive nights in the coastal town of Celestún, Yucatan, southeast Mexico, during the rainy season (August) of 2007. A total of 292 female mosquitoes representing 12 species of dipteran Culicidae were collected: Anopheles albimanus (Wiedemann); Anopheles crucians (Wiedemann); Anopheles pseudopunctipennis (Theobald); Culex coronator (Dyar & Knab); Culex interrogator (Dyar & Knab); Culex nigripalpus (Theobald); Culex quinquefasciatus (Say); Culex salinarius (Coquillett); Aedes aegypti (Linnaeus); Aedes scapularis (Rondani); Aedes sollicitans (Walker), and Aedes taeniorhynchus (Wiedemann). Aedes taeniorhynchus and Cx. quinquefasciatus were the species found most commonly feeding on the dogs. Filarial nematodes were observed by microscopy in nine of the mosquito species collected; however, third‐instar larvae were only observed in Ae. taeniorhynchus and An. crucians. Of 76 Ae. taeniorhynchus specimens found positive for Dirofilaria sp. by dissection, 14 were confirmed to be positive for Dirofilaria immitis (Leidy) by polymerase chain reaction (PCR). The resulting infection rate for D. immitis confirmed by PCR (6.2%) is higher than any infection rate for Ae. taeniorhynchus previously reported from the Americas.     

Differential modulation of murine host immune response by salivary gland extracts from the mosquitoes Aedes aegypti and Culex quinquefasciatus

Mosquitoes (Diptera: Culicidae) are major vectors of numerous infectious agents. Compounds in mosquito saliva not only facilitate blood-feeding, but may also have an impact upon the immune system of vertebrate hosts. Consequently, the exposure to mosquito saliva may influence pathogen transmission, establishment and disease development. Using two medically important vector mosquitoes, Aedes aegypti (L.) and Culex quinquefasciatus Say, we examined the effects of mosquito saliva on immune cells of host mice. After antigen-specific or non-specific stimulation, murine splenocyte proliferation and production of both Th1 and Th2 cytokines were significantly reduced in the presence of salivary gland extract (SGE) from Ae. aegypti, but not SGE from Cx. quinquefasciatus. T cell populations were highly susceptible to this suppression, showing increased mortality and reduced division rates - judged by flow cytometric analyses. Evidently these two culicine mosquitoes differ in their host immunomodulatory activities.     

Larval mortality of Culex tarsalis and Aedes aegypti when reared with different concentrations of Tetrahymena pyriformis

The paucity of information on infection and pathogenicity of mosquito larvae by ciliates under experimental conditions prompted the evaluation of the relationship between a clone of Tetrahymena pyriformis and two species of mosquitoes, Aedes aegypti and Culex tarsalis. A significant difference in mortality was observed between the two mosquito species when they were exposed to identical concentrations of ciliates. In rearing trays containing high concentrations of T. pyriformis, 76.3% of the C. tarsalis larvae died. Under similar conditions, death occurred in less than 3.0% of the A. aegypti larvae. Three figures illustrate daily results of these studies. Three criteria for facultative parasites are listed, and one, route of entry into the host, is discussed in detail.     

Synergistic efficacy of botanical blends with and without synthetic insecticides against Aedes aegypti and Culex annulirostris mosquitoes.

Increasing insecticide resistance requires strategies to prolong the use of highly effective vector control compounds. The use of combinations of insecticides with other insecticides and phytochemicals is one such strategy that is suitable for mosquito control. In bioassays with Aedes aegypti and Culex annulirostris mosquitoes, binary mixtures of phytochemicals with or without synthetic insecticides produced promising results when each was applied at a LC25 dose. All mixtures resulted in 100% mortality against Cx. annulirostris larvae within 24 h rather than the expected mortality of 50%. All mixtures acted synergistically against Ae. aegypti larvae within the first 24 h except for one mixture that showed an additive effect. We conclude that mixtures are more effective than insecticides or phytochemicals alone and that they enable a reduced dose to be applied for vector control potentially leading to improved resistance management and reduced costs.