Evaluation of textile substrates for dispensing synthetic attractants for malaria mosquitoes

Background: The full-scale impact of odour-baited technology on the surveillance, sampling and control of vectors of infectious diseases is partly limited by the lack of methods for the efficient and sustainable dispensing of attractants. In this study we investigated whether locally-available and commonly used textiles are efficient substrates for the release of synthetic odorant blends attracting malaria mosquitoes. Methods: The relative efficacy of (a) polyester, (b) cotton, (c) cellulose + polyacrylate, and (d) nylon textiles as substrates for dispensing a synthetic odour blend (Ifakara blend 1(IB1)) that attracts malaria mosquitoes was evaluated in western Kenya. The study was conducted through completely randomized Latin square experimental designs under semi-field and field conditions. Results: Traps charged with IB1-impregnated polyester, cotton and cellulose + polyacrylate materials caught significantly more female Anopheles gambiae sensu stricto (semi-field conditions) and An. gambiae sensu lato (field conditions) mosquitoes than IB1-treated nylon (P = 0.001). The IB1-impregnated cellulose + polyacrylate material was the most attractive to female An. funestus mosquitoes compared to all other dispensing textile substrates (P < 0.001). The responses of female An. funestus mosquitoes to IB1-treated cotton and polyester were equal (P = 0.45). Significantly more female Culex mosquitoes were attracted to IB1-treated cotton than to the other treatments (P < 0.001). Whereas IB1-impregnated cotton and cellulose + polyacrylate material attracted equal numbers of female Mansonia mosquitoes (P = 0.44), the catches due to these two substrates were significantly higher than those associated with the other substrates (P < 0.001). Conclusion: The number and species of mosquitoes attracted to a synthetic odour blend is influenced by the type of odour-dispensing material used. Thus, surveillance and intervention programmes for malaria and other mosquito vectors using attractive odour baits should select an odour-release material that optimizes the odour blend

Development and optimization of the Suna trap as a tool for mosquito monitoring and control

Background Monitoring of malaria vector populations provides information about disease transmission risk, as well as measures of the effectiveness of vector control. The Suna trap is introduced and evaluated with regard to its potential as a new, standardized, odour-baited tool for mosquito monitoring and control. Methods Dual-choice experiments with female Anopheles gambiae sensu lato in a laboratory room and semi-field enclosure, were used to compare catch rates of odour-baited Suna traps and MM-X traps. The relative performance of the Suna trap, CDC light trap and MM-X trap as monitoring tools was assessed inside a human-occupied experimental hut in a semi-field enclosure. Use of the Suna trap as a tool to prevent mosquito house entry was also evaluated in the semi-field enclosure. The optimal hanging height of Suna traps was determined by placing traps at heights ranging from 15 to 105 cm above ground outside houses in western Kenya. Results In the laboratory the mean proportion of An. gambiae s.l. caught in the Suna trap was 3.2 times greater than the MM-X trap (P &lt;0.001), but the traps performed equally in semi-field conditions (P = 0.615). As a monitoring tool , the Suna trap outperformed an unlit CDC light trap (P &lt;0.001), but trap performance was equal when the CDC light trap was illuminated (P = 0.127). Suspending a Suna trap outside an experimental hut reduced entry rates by 32.8% (P &lt;0.001). Under field conditions, suspending the trap at 30 cm above ground resulted in the greatest catch sizes (mean 25.8 An. gambiae s.l. per trap night). Conclusions The performance of the Suna trap equals that of the CDC light trap and MM-X trap when used to sample An. gambiae inside a human-occupied house under semi-field conditions. The trap is effective in sampling mosquitoes outside houses in the field, and the use of a synthetic blend of attractants negates the requirement of a human bait. Hanging a Suna trap outside a house can reduce An. gambiae house entry and its use as a novel tool for reducing malaria transmission risk will be evaluated in peri-domestic settings in sub-Saharan Africa

Residual Plasmodium falciparum parasitemia in Kenyan children after artemisinin-combination therapy is associated with increased transmission to mosquitoes and parasite recurrence.

BACKGROUND: Parasite clearance time after artemisinin-based combination therapy (ACT) may be increasing in Asian and African settings. The association between parasite clearance following ACT and transmissibility is currently unknown. METHODS: We determined parasite clearance dynamics by duplex quantitative polymerase chain reaction (qPCR) in samples collected in the first 3 days after treatment of uncomplicated malaria with ACT. Gametocyte carriage was determined by Pfs25 quantitative nucleic acid sequence-based amplification assays; infectiousness to mosquitoes by membrane-feeding assays on day 7 after treatment. RESULTS: Residual parasitemia was detected by qPCR in 31.8% (95% confidence interval [CI], 24.6-39.8) of the children on day 3 after initiation of treatment. Residual parasitemia was associated with a 2-fold longer duration of gametocyte carriage (P = .0007), a higher likelihood of infecting mosquitoes (relative risk, 1.95; 95% CI, 1.17-3.24; P = .015), and a higher parasite burden in mosquitoes (incidence rate ratio, 2.92; 95% CI, 1.61-5.31; P < .001). Children with residual parasitemia were also significantly more likely to experience microscopically detectable parasitemia during follow-up (relative risk, 11.25; 95% CI, 4.08-31.01; P < .001). CONCLUSIONS: Residual submicroscopic parasitemia is common after ACT and is associated with a higher transmission potential. Residual parasitemia may also have consequences for individual patients because of its higher risk of recurrent parasitemia

Extended Malaria Parasite Clearance Time in African Children Following Artemisinincombination Therapy Enhances Transmission\ud to Anopheles Mosquitoes

Artemisinin resistance was recently shown to have spread or emerged on the Thailand/Myanmar border. Evidence is accumulating that the parasite clearance time after artemisinin-based combination therapy (ACT) is increasing in settings in Asia and Africa. It is currently unknown if an extended parasite clearance time after ACTs has consequences for the individual patient or confers a higher malaria transmission potential. 298 children in Mbita, Western Kenya, with uncomplicated falciparum malaria were randomized to artemether-lumefantrine (AL, n = 153) ordihydroartemisinin-piperaquine (DP, n = 145). Parasite carriage post-treatment was determined by microscopy and qPCR, gametocyte carriage by quantitative nucleic acid sequence based amplication. Infectiousness to mosquitoes was determined by mosquito membrane feeding assays. Both drugs were efficacious as judged by standard trial outcomes. Sub-patent residual parasitaemia on day 3 was detected by qPCR in 36.11% (95% CI 25.11 - 48.29) of children treated with AL, and in 30.16% (95% CI 19.23 - 43.02) of children treated with DP. After adjustment for age, treatment arm and enrolment parasite density, children with an extended parasite clearance time were significantly more likely to have microscopically detected recurrent parasitaemia during follow-up (Odds Ratio: 19.51, 95% CI 5.24 - 72.71, p < 0.001). Children with an extended parasite clearance time were also more likely to be infectious to mosquitoes (Odds Ratio 2.76; 95% CI 1.14 - 6.67, p = 0.02) and gave rise to a higher oocyst load in mosquitoes (Incidence Rate Ratio 2.80, 95% CI 1.49 - 5.24, p = 0.001). Our findings indicate that an extended parasite clearance time after ACTs has consequences for the individual patient and for the population at large due to higher transmission potential. The high prevalence of residual subpatent parasitaemia after treatment may be due to novel parasite genotypes with reduced drug sensitivity, inadequate population-level immunity, or the higher sensitivity of qPCR for detection of persisting parasites.\u

A Novel Synthetic Odorant Blend for Trapping of Malaria and Other African Mosquito Species

Estimating the biting fraction of mosquitoes is of critical importance for risk assessment of malaria transmission. Here, we present a novel odor-based tool that has been rigorously assessed in semi-field assays and traditional African villages for estimating the number of mosquitoes that enter houses in search of a blood meal. A standard synthetic blend (SB) consisting of ammonia, (S)-lactic acid, tetradecanoic acid, and carbon dioxide was complemented with isovaleric acid, 4,5 dimethylthiazole, 2-methyl-1-butanol, and 3-methyl-1-butanol in various combinations and concentrations, and tested for attractiveness to the malaria mosquito Anopheles gambiae. Compounds were released through low density polyethylene (LDPE) material or from nylon strips (nylon). Studies were done in a semi-field facility and two traditional villages in western Kenya. The alcohol 3-methyl-1-butanol significantly increased the attraction of SB. The other compounds proved less effective or inhibitory. Tested in a village, 3-methyl-1-butanol, released from LDPE, increased the attraction of SB. Further studies showed a significantly enhanced attraction of adding 3-methyl-1-butanol to SB compared to previously-published attractive blends both under semi-field and village conditions. Other mosquito species with relevance for public health were collected with this blend in significantly higher numbers as well. These results demonstrate the advent of a novel, reliable odor-based sampling tool for the collection of malaria and other mosquitoes. The advantage of this odor-based tool over existing mosquito sampling tools is its reproducibility, objectiveness, and relatively low cost compared to current standards of CDC light traps or the human landing catch

Development of environmental tools for anopheline larval control

<p>Abstract</p> <p>Background</p> <p>Malaria mosquitoes spend a considerable part of their life in the aquatic stage, rendering them vulnerable to interventions directed to aquatic habitats. Recent successes of mosquito larval control have been reported using environmental and biological tools. Here, we report the effects of shading by plants and biological control agents on the development and survival of anopheline and culicine mosquito larvae in man-made natural habitats in western Kenya. Trials consisted of environmental manipulation using locally available plants, the introduction of predatory fish and/or the use of <it>Bacillus thuringiensis </it>var. <it>israelensis </it>(<it>Bti</it>) in various combinations.</p> <p>Results</p> <p>Man-made habitats provided with shade from different crop species produced significantly fewer larvae than those without shade especially for the malaria vector <it>Anopheles gambiae</it>. Larval control of the African malaria mosquito <it>An. gambiae </it>and other mosquito species was effective in habitats where both predatory fish and <it>Bti </it>were applied, than where the two biological control agents were administered independently.</p> <p>Conclusion</p> <p>We conclude that integration of environmental management techniques using shade-providing plants and predatory fish and/or <it>Bti </it>are effective and sustainable tools for the control of malaria and other mosquito-borne disease vectors.</p

Variability in nutrient composition of the edible long‐horned grasshopper (Ruspolia differens) in Uganda and its potential in alleviating food insecurity

Abstract Ruspolia differens Serville (Orthoptera: Tettigonidae) is a highly nutritious and luxurious insect delicacy that is consumed as a food source in many African countries. However, the nutrient profile of R. differens in different geographical regions have received limited research interest. Here, we provide comprehensive evidence of geographical impact on the nutrient profile of R. differens and its potential to meet the recommended dietary intake of the population. Our results demonstrated that proximate composition, fatty acids, amino acids, minerals, vitamins, and flavonoid contents of R. differens collected from five districts in Uganda varied considerably. The crude protein (28–45%), crude fat (41–54%), and energy (582–644 Kj/100 g) contents of R. differens exceed that reported from animal origins. The highest crude protein, crude fat, and carbohydrate contents of R. differens were recorded in Kabale, Masaka, and Kampala, respectively. A total of 37 fatty acids were identified with linoleic acid (omega‐6 fatty acid) being the most abundant polyunsaturated fatty acid in R. differens from Kabale, Masaka, and Mbarara. All essential amino acids were recorded in R. differens, particularly histidine with values exceeding the daily requirement for adults. Mineral and vitamin content differed significantly across the five districts. The highest quantity of flavonoids was recorded in R. differens from Hoima (484 mg/100 g). Our findings revealed that R. differens could be considered as functional food ingredients capable of supplying essential macro‐ and micronutrients that are critical in curbing the rising food insecurity and malnutrition in the regions