Experiments demonstrating the feasibility of genetically modifying mosquito vectors to impair their ability to transmit the malaria parasite have been known for well over a decade. However, means to ...spread resistance or population control genes into wild mosquito populations remains an unsolved challenge. Two recent reports give hope that CRISPR technology may allow such challenge to be overcome.
Background Long-lasting insecticidal nets (LLINs) are ineffective malaria transmission prevention tools if they are unused. Discomfort due to heat is the most commonly reported reason for not using ...nets, but this problem is largely unaddressed. With increasing rural electrification and the dropping price of solar power, fans could improve comfort inside nets and be affordable to populations in malaria endemic areas. Here, results are presented from a pilot randomized controlled cross-over study testing the effect of fans on LLIN use. Methods Eighty-three households from two rural communities in Greater Accra, Ghana, randomized into three groups, participated in a 10-month cross-over trial. After a screening survey to identify eligible households, all households received new LLINs. Breversed sigmakreversed sigmareversed sigma net fan systems (one fan per member) were given to households in Group 1 and water filters were given to households in Group 2. At mid-point, Group 1 and 2 crossed over interventions. Households in Group 1 and 2 participated in fortnightly surveys on households' practices related to nets, fans and water filters, while households in Group 3 were surveyed only at screening, mid-point and study end. Entomological and weather data were collected throughout the study. Analysis took both 'per protocol' (PP) and 'intention to treat' (ITT) approaches. The mid- and end-point survey data from Group 1 and 2 were analysed using Firth logistic regressions. Fortnightly survey data from all groups were analysed using logistic regressions with random effects. Results Provision of fans to households appeared to increase net use in this study. Although the increase in net use explained by fans was not significant in the primary analyses (ITT odds ratio 3.24, p > 0.01; PP odds ratio = 1.17, p > 0.01), it was significant in secondary PP analysis (odds ratio = 1.95, p < 0.01). Net use was high at screening and even higher after provision of new LLINs and with follow up. Fan use was 90-100% depending on the fortnightly visit. Conclusions This pilot study could not provide definitive evidence that fans increase net use. A larger study with additional statistical power is needed to assess this association across communities with diverse environmental and socio-demographic characteristics.
A variety of traps are used for sampling, surveillance, and monitoring of mosquito vector species associated with parasite and pathogen transmission. Here, we assessed the performance of the Mosquito ...Magnet Independence trap with Lurex3 (MMI), by comparing its effectiveness with those of a Centers for Disease Control and Prevention light trap (CDC-LT) and CDC with CO2 and Lurex3 (CDC-A) in a dense tropical rainforest. Multivariate generalized linear models revealed significant differences among the traps regarding mosquito composition and abundance (deviance = 768; P = 0.016). Variance analyses indicated that the MMI captured significantly more mosquitoes compared with CDC-LT (P < 0.01) and CDC-A (P < 0.03). The abundance values did not significantly differ between the CDC-LT and CDC-A traps (P = 0.7). Mosquito species richness was higher from the MMI than from the CDC-LT and CDC-A traps. Furthermore, medically important mosquito species captured by the three traps showed high association with MMI. These results suggest the potential to use the MMI in studies aiming to obtain entomological surveillance information about medically important mosquitoes that occur in tropical rainforest areas. The MMI could also be used in faunal studies focusing on increasing knowledge about mosquito diversity. Considering the present positive results, the effectiveness of the MMI should additionally be evaluated in other Brazilian natural ecosystems. Further studies are also needed to address demographic data from the mosquito population sampled by the MMI.
Sometimes history gives us a second chance by repeating itself. The timely and lucid modeling analysis presented by Phillip Eckhoff in this issue super(1) reminds us all that the challenges and ...opportunities faced by the malaria control community today remain remarkably similar to those of our predecessors who undertook the Global Malaria Eradication Campaign (GMEP). The anti-malarial drugs we use in 2013 are relatively new to the front lines but they are still overwhelmingly used in the same way for reactive clinical management of symptomatic cases. super(2) Long-lasting insecticidal nets (LLINs) now offer a proven alternative to indoor residual spraying (IRS) as the front-line vector control tool of the GMEP era but both approaches target mosquitoes within the same indoor environment and evidence that combining the two yields incremental benefits remains mixed. super(3-7) Although efficacious vaccines against malaria now exist and their expected impacts are simulated here, super(1) the protection they confer is partial and may wane super(8) as naturally acquired immunity fades super(9) and/or naturally acquired skin stage infections induce immunotolerance of pre-erythrocytic stages.
The residual efficacy of lambda -cyhalothrin sprayed on foliage was evaluated against various mosquito species in sections of forest in Cairns, Queensland, Australia. Weekly sweep-net collections in ...treated and untreated areas before and after spraying showed 87-100% reductions in mosquito numbers for the first 9 wk postspray. After that period, reductions fluctuated but remained >71% up to 14 wk posttreatment. Mosquito mortality ranged from 96 to 100% in contact bioassays of treated leaves during the 14 wk study. Our results demonstrate that spraying harborage vegetation with lambda -cyhalothrin is an extremely effective strategy for the control of sylvan and peridomestic mosquito species in tropical north Queensland.
Mosquito collections were conducted in Zika Forest near Entebbe, Uganda, from July 2009 through June 2010 using CO2-baited light traps, ovitraps, and human-baited catches. In total, 163,790 adult ...mosquitoes belonging to 12 genera and 58 species were captured. Of these, 22 species (38%) were captured in Zika Forest for the first time. All the new records found in the forest in this study had previously been captured in other regions of Uganda, implying that they are native to the country and do not represent new introductions. More than 20 species previously collected in Zika Forest were not detected in our collections, and thismaysuggest a change in the mosquito fauna during the past 40 yr or variation in species composition from year to year. Arboviruses of public health importance have previously been isolated from >50% of the 58 mosquito species captured in Zika Forest, which suggests a high potential for transmission and maintenance of a wide range of arboviruses in Zika Forest.
By transmitting major human diseases such as malaria, dengue fever and filariasis, mosquito species represent a serious threat worldwide in terms of public health, and pose a significant economic ...burden for the African continent and developing tropical regions. Most vector control programmes aiming at controlling life-threatening mosquitoes rely on the use of chemical insecticides, mainly belonging to the pyrethroid class. However, resistance of mosquito populations to pyrethroids is increasing at a dramatic rate, threatening the efficacy of control programmes throughout insecticide-treated areas, where mosquito-borne diseases are still prevalent. In the absence of new insecticides and efficient alternative vector control methods, resistance management strategies are therefore critical, but these require a deep understanding of adaptive mechanisms underlying resistance. Although insecticide resistance mechanisms are intensively studied in mosquitoes, such adaptation is often considered as the unique result of the selection pressure caused by insecticides used for vector control. Indeed, additional environmental parameters, such as insecticides/pesticides usage in agriculture, the presence of anthropogenic or natural xenobiotics, and biotic interactions between vectors and other organisms, may affect both the overall mosquito responses to pyrethroids and the selection of resistance mechanisms. In this context, the present work aims at updating current knowledge on pyrethroid resistance mechanisms in mosquitoes and compiling available data, often from different research fields, on the impact of the environment on mosquito response to pyrethroids. Key environmental factors, such as the presence of urban or agricultural pollutants and biotic interactions between mosquitoes and their microbiome are discussed, and research perspectives to fill in knowledge gaps are suggested.
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► Impact of environment on mosquito response to pyrethroids is reviewed. ► Main known pyrethroid resistance mechanisms are described. ► Environmental factors potentially affecting these mechanisms are identified. ► Research perspectives are proposed.
Response—New Mosquito Subgroup Breeds Questions Riehle, Michelle M.; Guelbeogo, Wamdaogo M.; Eiglmeier, Karin ...
Science (American Association for the Advancement of Science),
04/2011, Volume:
332, Issue:
6028
Journal Article
Chemical recognition plays an important role for the survival and reproduction of many insect species. Odorant binding proteins (OBPs) are the primary components of the insect olfactory mechanism and ...have been documented to play an important role in the host-seeking mechanism of mosquitoes. They are "transport proteins" believed to transport odorant molecules from the external environment to their respective membrane targets, the olfactory receptors. The mechanism by which this transport occurs in mosquitoes remains a conundrum in this field. Nevertheless, OBPs have proved to be amenable to conformational changes mediated by a pH change in other insect species. In this paper, the effect of pH on the conformational flexibility of mosquito OBPs is assessed computationally using molecular dynamics simulations of a mosquito OBP "CquiOBP1" bound to its pheromone 30G (PDB ID: 30GN). Conformational twist of a loop, driven by a set of well-characterized changes in intramolecular interactions of the loop, is demonstrated. The concomitant (i) closure of what is believed to be the entrance of the binding pocket, (ii) expansion of what could be an exit site, and (iii) migration of the ligand towards this putative exit site provide preliminary insights into the mechanism of ligand binding and release of these proteins in mosquitoes. The correlation of our results with previous experimental observations based on NMR studies help us provide a cardinal illustration on one of the probable dynamics and mechanism by which certain mosquito OBPs could deliver their ligand to their membrane-bound receptors at specific pH conditions.
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