An improved odor bait for monitoring populations of Aedes aegypti-vectors of dengue and chikungunya viruses in Kenya

Aedes albopictus (Skuse) and other container-inhabiting species have become important public health concerns due to the transmission of dengue, chikungunya, and Zika viruses. Effective surveillance is dependent on the ability to collect a sufficient number of mosquitoes for population monitoring and pathogen isolation. The Biogents Sentinel (BGS) trap supplied with a proprietary human skin lure has become the standard tool for container-inhabiting Aedes species collections worldwide. Recently, R-octenol, a single isomer of the well characterized mosquito attractant octenol, was shown to greatly improve the capture rate of some Aedes species when utilized with the Center for Disease Control and Prevention (CDC) light traps and Mosquito Magnet traps. This study evaluated the effectiveness of the TrapTech lure (TT lure), containing R-octenol, alone or in combination with the human skin lure in a BGS trap to capture Ae. albopictus and other species. BGS traps with human skin lures or a combination of the two lures collected approximately twice as many Ae. albopictus females compared to those with TT lures. Unlike previous studies, baiting BGS traps with TT lures did not result in increased diversity of mosquito species, or in higher numbers of other container-inhabiting Aedes species. Although human skin lures were clearly superior to TT R-octenol lures in BGS traps, R-octenol lures are more widely available and might still be used as an alternative lure, especially when Ae. albopictus populations are high.

As Aedes aegypti continues to expand its global distribution, the diseases it vectors (dengue, Zika, chikungunya and yellow fever) are of increasing concern. Modern efforts to control this species include “rear and release” strategies where lab-reared mosquitoes are distributed throughout the landscape to replace or suppress invasive populations. These programs require intensive surveillance efforts to monitor their success, and the Biogents Sentinel (BGS) trap is one of the most effective tools for sampling adult Ae. aegypti. BGS trap catches can be highly variable throughout landscapes, so we investigated the potential impacts of environmental factors on adult Ae. aegypti capture rates during a “rear and release” program in California to better understand the relative contributions of true variability in population density across a landscape and trap context. We recorded male and female Ae. aegypti catches from BGS traps, with and without CO2, throughout control sites where no mosquitoes were released and in treatment sites where males infected with Wolbachia were released. BGS trap catches were positively influenced by higher proportions of shade or bushes in the front yard of the premises as well as the presence of potential larval habitats such as subterranean vaults. In contrast, an increase in residential habitat within a 100 m radius of trap locations negatively influenced BGS trap catches. For male Ae. aegypti, increased visual complexity of the trap location positively influenced capture rates, and the presence of yard drains negatively affected catch rates in control sites. Lastly, for BGS traps using CO2, higher catch rates were noted from traps placed greater than one meter from walls or fences for both male and female mosquitoes. These results have important implications for surveillance programs of Ae. aegypti throughout the Californian urban environment including adult monitoring during “rear and release” programs.

Two types of mosquito trap were tested near Smith Lake in Portland, Multnomah County, OR: 2 Biogents Sentinel (BGS) traps baited with carbon dioxide (CO2) and an octenol sachet or a BG Lure, and an encephalitis virus surveillance (EVS) trap with CO2 but without an odor sachet. After 6 trap-nights, the 2 BGS traps caught significantly more mosquitoes than the EVS trap. More Culex tarsalis and an overall greater number of species were caught in the BGS traps. A BGS trap and an EVS trap, both baited with CO2 alone, were compared to investigate whether the difference was due to the attractants or the difference in trap type. The BGS trap caught more mosquitoes but the difference was not significant. The BGS trap, when baited with CO2 and other lures, can be an effective mosquito sampling tool, but further research is needed to understand the importance of the attractants.

Mosquitoes are nuisance insects and they serve as vectors of many diseases. Mosquito surveillance is an important component of mosquito control programs and traps are especially useful in vector mosquito surveillance. Initially, we used a Biogents® Sentinel (BGS) trap with lure and a CDC trap with CO2 to survey adult mosquitoes in different settings like gardens, buildings, huts, and cattle farms. Across all study sites, the BGS trap with lure consistently collected higher densities of mosquitoes across all species compared to the CDC trap with CO2. Culex quinquefasciatus was the predominant species across all study sites. Subsequently, we used different combinations of lures in BGS traps and tested their efficacy in collecting adult mosquitoes in buildings and huts. Overall, the BGS traps with lure + CO2 consistently collected higher densities of mosquitoes across species. Again, Culex quinquefasciatus was the highest collected mosquito species in buildings (389.0 ± 30.80) as well as huts (388.0 ± 33.60). The traps also collected Culex gelidus, Aedes aegypti, Aedes albopictus in minor quantities in different settings.

The Biogents® Sentinel (BGS) trap is the standard tool to monitor adult Aedes (Stegomyia) albopictus (Skuse) (Diptera: Culicidae), the Asian tiger mosquito. BGS traps are commonly placed in residential properties during surveillance operations, but locations within properties may have significant differences in ambient light, temperature, and humidity (e.g. between a sunlit lawn and shady underbrush). We examined the effect of BGS trap placement on Ae. albopictus capture rates in three residential properties in Monmouth County, New Jersey, USA. In each property we visually selected locations as shade, partial shade, and sun. Traps in “partial shade” locations were under vegetation and were exposed to filtered sunlight during some parts of the day while “shaded” locations were never exposed to direct sunlight. Locations defined as “sun” were exposed to direct sunlight for large parts of the day. We placed a BGS trap in each of the three location types and used small data loggers to measure temperature, relative humidity, and light exposure at each trap during a 24-hour deployment. To address temporal variability, we made seven separate measurements from 31 August to 22 September 2010. We found that “partial shade” and “full shade” locations did not differ but that “full sun” locations had significantly higher light exposure, higher temperature, and lower humidity. Importantly, Ae. albopictus catches (males, females, or both) were consistently and significantly over 3 times higher in traps located in shaded locations. To further investigate the effects of local temperature and humidity on surveillance we examined Ae. albopictus collections from 37 BGS traps fitted with data loggers and deployed weekly from August through mid October, during the 2009 season, in three urban sites in Mercer County, NJ. We confirmed that local climate influences capture rates and that Ae. albopictus surveillance projects need to monitor trap placement carefully for maximum efficiency.

As the incidence of arboviral diseases such as dengue, Zika, chikungunya, and yellow fever increases globally, controlling their primary vector, Aedes aegypti (L.) (Diptera: Culicidae), is of greater importance than ever before. Mosquito control programs rely heavily on effective adult surveillance to ensure methodological efficacy. The Biogents Sentinel (BGS) trap is the gold standard for surveilling adult Aedes mosquitoes and is commonly deployed worldwide, including during modern 'rear and release' programs. Despite its extensive use, few studies have directly assessed environmental characteristics that affect BGS trap catches, let alone how these influences change during 'rear and release' programs. We assessed male and female Ae. aegypti spatial stability, as well as premises condition and trap location influences on BGS trap catches, as part of Debug Innisfail 'rear and release' program in northern Australia. We found similar trends in spatial stability of male and female mosquitoes at both weekly and monthly resolutions. From surveillance in locations where no males were released, reduced catches were found at premises that contained somewhat damaged houses and unscreened properties. In addition, when traps were located in areas that were unsheltered, more than 10 m from commonly used sitting areas or more visually complex catches were also negatively affected. In locations where males were released, we found that traps in treatment sites, relative to control sites, displayed increased catches in heavily shaded premises and were inconsistently influenced by differences in house sets and building materials. Such findings have valuable implications for a range of Ae. aegypti surveillance programs.

Aedes koreicus (Edwards) is an invasive mosquito species, like Aedes albopictus (Skuse) and Aedes japonicus japonicus (Theobald), that has already colonized a large part of northeastern Italy and other European countries. Despite its rapid expansion, information about adult distribution and trapping is lacking. Here, we conducted a 2-yr longitudinal survey using adult traps to investigate the spatiotemporal distribution of Ae. koreicus and evaluated the effectiveness of three trapping devices in Latin square experiments conducted in an urban site and a forested site. The following three different traps were compared: a CO2-baited Biogents (BG) Sentinel trap, a CO2-baited Centers for Disease Control and Prevention light trap (CDC trap), and a grass infusion-baited gravid trap.In northern Italy, Ae. koreicus was collected from late April to early November, with peak of abundance observed in August. Aedes koreicus was more abundant in 2015 than in 2014 because of higher temperatures during summer. Unlike Ae. albopictus, the abundance of Ae. koreicus was not related to the altitude of the sampling locations in the range 241-660 m above sea level. The BG Sentinel and gravid traps collected significantly more Ae. koreicus than the CDC trap in the urban site, whereas there was no significant difference between the three traps in the forested site. In the urban site, the BG Sentinel trap and the gravid trap were the most effective for collecting Ae. albopictus and Culex pipiens L., respectively. In the forested site, Cx. pipiens was primarily collected by the CDC trap.

BackgroundElimination of lymphatic filariasis (LF) in Samoa continues to be challenging despite multiple annual mass drug campaigns aimed at stopping transmission by reducing the prevalence and density of microfilaraemia. The persistence of transmission may be partly related to the highly efficient Aedes vectors. The assessment of pathogen transmission by mosquito vectors and of vector control relies on the ability to capture mosquitoes efficiently. The aims of this study are to compare trapping methods to capture LF-infected mosquitoes and determine the role in transmission of the species of Aedes mosquitoes in the area.MethodsFasitoo-Tai village was the chosen site because of persistent transmission despite annual mass drug administration. Sampling methods included BioGents Sentinel (BGS) trap, human-baited collections (HBC) and the Centers for Disease Control (CDC) trap. BGS and CDC traps were baited with BG-lure, CO2, and/or octenol. Individual trap locations were geo-located and efficiency of sampling methods was evaluated using a randomized Latin-square design in two locations. Number of mosquitoes collected (male and female), as well as species for each trapping method were determined. Additionally, Ae. polynesiensis and Ae. (Finlaya) spp. females were pooled by trap method and analysed for filarial DNA. Infection prevalence was estimated using the PoolScreen software.ResultsThe BGS trap with any type of bait collected more mosquitoes compared to both the CDC trap and the HBC. The BGS trap baited with BG-lure collected more mosquitoes than with CO2 and octenol. There were no significant differences between trapping methods in terms of proportions of infected females collected. The prevalence of filarial infection in Ae. polynesiensis and Ae. (Finlaya) spp. was estimated at 4.7 % and 0.67 % respectively.ConclusionsThis study supports the use of the BGS trap for research on and surveillance of the mosquito vectors of LF in Samoa. The BGS trap is a suitable and safer alternative to HBC for sampling Ae. polynesiensis and Ae. (Finlaya) spp., which continue to be the predominant vectors of LF. Of concern was the high prevalence of LF in mosquitoes despite a recent mass drug administration programme. This highlights the urgency for updated policies concerning filariasis elimination in Samoa.

Native to Southeast Asia, the spotted wing drosophila, Drosophila suzukii Matsumura (Diptera: Drosophilidae), has become a serious pest of soft-skinned fruit crops since its introduction into North America and Europe in 2008. Current monitoring strategies use baits based on fermentation products; however, to date, no fruit-based volatile blends attractive to this fly have been identified. This is particularly important because females are able to cut into the epicarp of ripening fruit for oviposition. Thus, we conducted studies to: 1) investigate the behavioral responses of adult D. suzukii to volatiles from blueberry, cherry, raspberry, and strawberry fruit extracts; 2) identify the antennally active compounds from the most attractive among the tested extracts (raspberry) using gas chromatography (GC)-mass spectrometry and coupled gas chromatography -electroantennographic detection (GC-EAD); and 3) test a synthetic blend containing the EAD-active compounds identified from raspberry extract on adult attraction. In olfactometer studies, both female and male D. suzukii were attracted to all four fruit extracts. The attractiveness of the fruit extracts ranks as: raspberry ≥ strawberry > blueberry ≥ cherry. GC analyses showed that the fruit extracts emit distinct volatile compounds. In GC-EAD experiments, 11 raspberry extract volatiles consistently elicited antennal responses in D. suzukii. In choice test bioassays, a synthetic EAD-active blend attracted more D. suzukii than a blank control, but was not as attractive as the raspberry extract. To our knowledge, this is the first report of a behaviorally and antennally active blend of host fruit volatiles attractive to D. suzukii, offering promising opportunities for the development of improved monitoring and behaviourally based management tools.

Biogents Sentinel (BGS) traps have rapidly become a standard for adult Aedes aegypti surveillance. Several investigators have found that trap collections can be damaged easily by heavy dew or rain entering the trap intake port. In addition, water entering the trap may temporarily stop the fan, thus reducing the collection potential of the trap. We evaluated the effectiveness of a rain cover designed to minimize damage to mosquito trap collections from BGS 2.0 traps in a residential backyard in Jacksonville, FL. Rain covers consisted of white fiberglass 51-cm2 sheets positioned 19, 29, and 39 cm above the air intake of the traps. One BGS trap did not have a rain cover and was used as a control standard for comparison. All traps were baited with the BG-Lure. Generally, traps with rain covers resulted in higher mosquito counts when compared with collections from uncovered traps. Overall mosquito abundance was greater from traps with the rain cover positioned at 29 cm, but this difference was not significantly different when compared with the other cover heights. Covers spaced 29 or 39 cm collected significantly more Culex quinquefasciatus compared with traps at 19 cm and no cover. Species diversity was greatest for BGS traps with the rain cover positioned at 29 cm followed by 39 cm, 19 cm, and no cover; however, differences in diversity among the traps, with or without covers, were not significant.

Mini-mark-release-recapture experiments were conducted in suburban Cairns, Australia to establish the sampling rate of the Biogents-Sentinel (BGS) trap for adult Aedes aegypti (L.). Small cohorts of marked mosquitoes (30 females and 15 males) were released at typical Cairns residences, and the number of marked mosquitoes recaptured in the BGS trap after 24 h was recorded. The sampling rate was compared between two seasons and two common housing styles (high-set 'Queenslander-style' timber and low-set brick houses), between old gravid and young nulliparous females, and between mosquitoes released in different areas of a house. Overall, the BGS traps recaptured a mean (+/- SEM) of 24.6% (+/- 1.9) of the released marked female mosquitoes in 24 h. The mean recapture rate for females was significantly higher in the dry season (30.4% +/- 2.8) compared with the wet (18.8% +/- 2.2). The overall recapture rates did not differ significantly between the two house types, but variability between the individual premises was high. An overall mean of 18.2% (+/- 1.7) of males was collected. Recapture rates of young nullipars and older gravid females were similar. These recapture rates can be used to estimate the population density of Ae. aegypti females in north Queensland, although it will provide an underestimate as trap sample was largely representative of mosquitoes present in the same area as the trap, and not from other areas of the house.

Three candidate sex pheromone components, (Z)6,(Z)9-, (Z)6,(E)8-, and (Z)6,(E)9-heneicosadien-11-one (Z6Z9, Z6E8, and Z6E9) were identified in pheromone gland extracts of female Douglas-fir tussock moths (DFTM), Orgyia pseudotsugata (McDunnough). Their occurrence in subnanogram quantities in extracts and structural conversion during analytical procedures and bioassays complicated chemical identifications. Complete identification required comparative analyses of stereoselectively synthesized and female-produced dienones by coupled gas chromatographic–electroantennographic detection (GC-EAD), high-performance liquid chromatography (HPLC) and coupled GC–mass spectrometry (MS). Determination of the pheromone component was contingent upon an experimental design that minimized structural rearrangement of dienones before and during the field test. In a 40-min field experiment, acetonitrile solutions of each of the above dienones were carried on Dry Ice to traps and were syringed onto cotton release devices below trap lids. In combination with the previously known sex pheromone component of DFTM, (Z)6-heneicosen-11-one (Z6), Z6E8 was the only synergistic dienone and the mixture was highly attractive. Because Z6 by itself attracts seven species of tussock moths (two sympatric with DFTM), a blend of Z6 and Z6E8 may impart specificity to DFTM pheromone communication. In commercial lures, this binary blend may facilitate species-specific, sensitive monitoring and efficacious control by mating disruption of this important forest defoliator.

Two methylated hydrocarbons, 7-methylheptadecane (7) and 7,11-dimethylheptadecane (7,11), are sex pheromone components of female pitch pine looper (PPL), Lambdina pellucidaria. Compounds extracted from the pheromone glands of female moths were identified by coupled gas chromatographic–electroantennographic detection (GC-EAD) and coupled GC–mass spectrometry (GC-MS) in selected ion monitoring mode. In field-trapping experiments, 7 and 7,11 in combination, but not singly, attracted numerous male moths. 5,11-Dimethylheptadecane (5,11) was detected by GC-EAD in female PPL pheromone gland extract, but did not significantly increase attraction of PPL males to 7 plus 7,11. Although 7 was > 10 times more abundant than 7,11 in pheromone gland extracts, traps baited with synthetic 7 plus 7,11 at a blend ratio of 1:1, rather than 1:0.1 or 1:0.01, captured the most PPL males. The chemical communication of PPL and spring hemlock looper (SHL), Lambdina athasaria, is strikingly similar. Both species employ 7 plus 7,11 as sex pheromone. Restriction of SHL to forests with eastern hemlock or balsam fir and PPL to forests with pitch or other hard pines contributes to their reproductive isolation. PPL and SHL may also use different optical isomers of enantiomeric 7 and stereoisomeric 7,11 to maintain specificity of their chemical communication.

Aedes aegypti (L.) (Diptera: Culicidae) is a vector of viruses causing dengue, Zika, chikungunya, and yellow fever and subsequently pose a significant global threat to public health. While sampling live mosquitoes is useful for surveillance purposes, most traps targeting Aedes kill captured mosquitoes. The Biogents Sentinel (BGS) trap, the gold standard for capturing Ae. aegypti, is one such trap. In our study, we modified the BGS trap to increase the survival of captured Ae. aegypti by replacing the trap's catch bag with a catch pot that protects mosquitoes from desiccation by airflow. A sucrose-soaked sponge or nucleic acid preservative card can also be placed inside the pot to enhance mosquito survival and augment arbovirus detection. These modifications to the BGS significantly increased the longevity of mosquitoes captured with weekly survivals of 93% in a semifield structure and 86% in the field. These high survival rates resulted in 3.5 times more alive Ae. aegypti captured weekly in the modified BGS compared to the original BGS, despite 40% lower overall catch rates. These cheap and simple trap modifications facilitate easier specimen identification as well as experiments requiring live field-collected samples such as virus detection from mosquito saliva and excreta.

A Deceptive Pollination System Targeting Drosophilids through Olfactory Mimicry of Yeast