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A new tent trap for sampling exophagic and endophagic members of the Anopheles gambiae complex

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      Abstract

      Background

      Mosquito sampling methods are essential for monitoring and evaluating malaria vector control interventions. In urban Dar es Salaam, human landing catch (HLC) is the only method sufficiently sensitive for monitoring malaria-transmitting Anopheles. HLC is labour intensive, cumbersome, hazardous, and requires such intense supervision that is difficulty to sustain on large scales.

      Methods

      Novel tent traps were developed as alternatives to HLC. The Furvela tent, designed in Mozambique, incorporates a CDC Light trap (LT) components, while two others from Ifakara, Tanzania (designs A and B) require no electricity or moving parts. Their sensitivity for sampling malaria vectors was compared with LT and HLC over a wide range of vector abundances in rural and urban settings in Tanzania, with endophagic and exophagic populations, respectively, using randomised Latin-square and cross- over experimental designs.

      Results

      The sensitivity of LTs was greater than HLC while the opposite was true of Ifakara tent traps (crude mean catch of An. gambiae sensu lato relative to HLC = 0.28, 0.65 and 1.30 for designs A, B and LT in a rural setting and 0.32 for design B in an urban setting). However, Ifakara B catches correlated far better to HLC (r2 = 0.73, P < 0.001) than any other method tested (r2 = 0.04, P = 0.426 and r2 = 0.19, P = 0.006 for Ifakara A and LTs respectively). Only Ifakara B in a rural setting with high vector density exhibited constant sampling efficiency relative to HLC. The relative sensitivity of Ifakara B increased as vector densities decreased in the urban setting and exceeded that of HLC at the lowest densities. None of the tent traps differed from HLC in terms of the proportions of parous mosquitoes (P ≥ 0.849) or An. gambiae s.l. sibling species (P ≥ 0.280) they sampled but both Ifakara A and B designs failed to reduce the proportion of blood-fed mosquitoes caught (Odds ratio [95% Confidence Interval] = 1.6 [1.2, 2.1] and 1.0 [0.8, 1.2], P = 0.002 and 0.998, respectively), probably because of operator exposure while emptying the trap each morning.

      Conclusion

      The Ifakara B trap may have potential for monitoring and evaluating a variety of endophagic and exophagic Afrotropical malaria vectors, particularly at low but epidemiologically relevant population densities. However, operator exposure to mosquito bites remains a concern so additional modifications or protective measures will be required before this design can be considered for widespread, routine use.

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      Most cited references 55

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      Identification of single specimens of the Anopheles gambiae complex by the polymerase chain reaction.

      A ribosomal DNA-polymerase chain reaction (PCR) method has been developed for species identification of individuals of the five most widespread members of the Anopheles gambiae complex, a group of morphologically indistinguishable sibling mosquito species that includes the major vectors of malaria in Africa. The method, which is based on species-specific nucleotide sequences in the ribosomal DNA intergenic spacers, may be used to identify both species and interspecies hybrids, regardless of life stage, using either extracted DNA or fragments of a specimen. Intact portions of a mosquito as small as an egg or the segment of one leg may be placed directly into the PCR mixture for amplification and analysis. The method uses a cocktail of five 20-base oligonucleotides to identify An. gambiae, An. arabiensis, An. quadriannnulatus, and either An. melas in western Africa or An. melas in eastern and southern Africa.
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        Measurement in Medicine: The Analysis of Method Comparison Studies

         J Bland,  D Altman (1983)
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          Mosquito behavior and vector control.

          Effective indoor residual spraying against malaria vectors depends on whether mosquitoes rest indoors (i.e., endophilic behavior). This varies among species and is affected by insecticidal irritancy. Exophilic behavior has evolved in certain populations exposed to prolonged spraying programs. Optimum effectiveness of insecticide-treated nets presumably depends on vectors biting at hours when most people are in bed. Time of biting varies among different malaria vector species, but so far there is inconclusive evidence for these evolving so as to avoid bednets. Use of an untreated net diverts extra biting to someone in the same room who is without a net. Understanding choice of oviposition sites and dispersal behavior is important for the design of successful larval control programs including those using predatory mosquito larvae. Prospects for genetic control by sterile males or genes rendering mosquitoes harmless to humans will depend on competitive mating behavior. These methods are hampered by the immigration of monogamous, already-mated females.
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            Author and article information

            Affiliations
            [1]Ifakara Health Institute, Coordination Office, PO Box 78373, Kiko Avenue, Mikocheni, Dar es Salaam, United Republic of Tanzania
            [2]Dar es Salaam City Council, Ministry of Regional Administration and Local Government, United Republic of Tanzania
            [3]Durham University, School of Biological and Biomedical Sciences, South Road, Durham, DH13LE, UK
            [4]Liverpool School of Tropical Medicine, Pembroke place, Liverpool, L3QA, UK
            [5]Swiss Tropical Institute, Department of Public Health and Epidemiology, PO Box 4002, Basel, Switzerland
            [6]Danish Bilharziaisis Laboratory, 1-D Jaegersborg Allé, Charlottenlund, DK 2920, Denmark
            [7]Biology Department, University of Winnipeg, Winnipeg, Manitoba, R3B 2E9, Canada
            Contributors
            Journal
            Malar J
            Malaria Journal
            BioMed Central
            1475-2875
            2009
            14 July 2009
            : 8
            : 157
            2720981
            1475-2875-8-157
            19602253
            10.1186/1475-2875-8-157
            Copyright © 2009 Govella et al; licensee BioMed Central Ltd.

            This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

            Categories
            Methodology

            Infectious disease & Microbiology

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