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Masalu JP, Finda M, Killeen GF, Ngowo HS, Pinda PG, Okumu FO. Creating mosquito-free outdoor spaces using transfluthrin-treated chairs and ribbons. Malar J 2020; 19:109. [PMID: 32156280 PMCID: PMC7063784 DOI: 10.1186/s12936-020-03180-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2019] [Accepted: 03/02/2020] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND Residents of malaria-endemic communities spend several hours outdoors performing different activities, e.g. cooking, story-telling or eating, thereby exposing themselves to potentially-infectious mosquitoes. This compromises effectiveness of indoor interventions, notably long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS). This study characterized common peri-domestic spaces in rural south-eastern Tanzania, and assessed protective efficacy against mosquitoes of hessian fabric mats and ribbons treated with the spatial repellent, transfluthrin, and fitted to chairs and outdoor kitchens, respectively. METHODS Two hundred households were surveyed, and their most-used peri-domestic spaces physically characterized. Protective efficacies of locally-made transfluthrin-emanating chairs and hessian ribbons were tested in outdoor environments of 28 households in dry and wet seasons, using volunteer-occupied exposure-free double net traps. CDC light traps were used to estimate host-seeking mosquito densities within open-structure outdoor kitchens. Field-collected Anopheles arabiensis and Anopheles funestus mosquitoes were exposed underneath the chairs to estimate 24 h-mortality. Finally, The World Health Organization insecticide susceptibility tests were conducted on wild-caught Anopheles from the villages. RESULTS Approximately half (52%) of houses had verandas. Aside from these verandas, most houses also had peri-domestic spaces where residents stayed most times (67% of houses with verandas and 94% of non-veranda houses). Two-thirds of these spaces were sited under trees, and only one third (34.4%) were built-up. The outdoor structures were usually makeshift kitchens having roofs and partial walls. Transfluthrin-treated chairs reduced outdoor-biting An. arabiensis densities by 70-85%, while transfluthrin-treated hessian ribbons fitted to the outdoor kitchens caused 77-81% reduction in the general peri-domestic area. Almost all the field-collected An. arabiensis (99.4%) and An. funestus (100%) exposed under transfluthrin-treated chairs died. The An. arabiensis were susceptible to non-pyrethroids (pirimiphos methyl and bendiocarb), but resistant to pyrethroids commonly used on LLINs (deltamethrin and permethrin). CONCLUSION Most houses had actively-used peri-domestic outdoor spaces where exposure to mosquitoes occurred. The transfluthrin-treated chairs and ribbons reduced outdoor-biting malaria vectors in these peri-domestic spaces, and also elicited significant mortality among pyrethroid-resistant field-caught malaria vectors. These two new prototype formats for transfluthrin emanators, if developed further, may constitute new options for complementing LLINs and IRS with outdoor protection against malaria and other mosquito-borne pathogens in areas where peri-domestic human activities are common.
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Affiliation(s)
- John P Masalu
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Morogoro, United Republic of Tanzania.
- School of Life Science and Biotechnology, Nelson Mandela African Institution of Science and Technology, Arusha, United Republic of Tanzania.
| | - Marceline Finda
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Morogoro, United Republic of Tanzania
- School of Public Health, University of the Witwatersrand, Parktown, Johannesburg, Republic of South Africa
| | - Gerry F Killeen
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Morogoro, United Republic of Tanzania
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Halfan S Ngowo
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Morogoro, United Republic of Tanzania
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK
| | - Polius G Pinda
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Morogoro, United Republic of Tanzania
| | - Fredros O Okumu
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Morogoro, United Republic of Tanzania
- School of Life Science and Biotechnology, Nelson Mandela African Institution of Science and Technology, Arusha, United Republic of Tanzania
- School of Public Health, University of the Witwatersrand, Parktown, Johannesburg, Republic of South Africa
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK
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Runge M, Snow RW, Molteni F, Thawer S, Mohamed A, Mandike R, Giorgi E, Macharia PM, Smith TA, Lengeler C, Pothin E. Simulating the council-specific impact of anti-malaria interventions: A tool to support malaria strategic planning in Tanzania. PLoS One 2020; 15:e0228469. [PMID: 32074112 PMCID: PMC7029840 DOI: 10.1371/journal.pone.0228469] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Accepted: 01/16/2020] [Indexed: 11/25/2022] Open
Abstract
INTRODUCTION The decision-making process for malaria control and elimination strategies has become more challenging. Interventions need to be targeted at council level to allow for changing malaria epidemiology and an increase in the number of possible interventions. Models of malaria dynamics can support this process by simulating potential impacts of multiple interventions in different settings and determining appropriate packages of interventions for meeting specific expected targets. METHODS The OpenMalaria model of malaria dynamics was calibrated for all 184 councils in mainland Tanzania using data from malaria indicator surveys, school parasitaemia surveys, entomological surveillance, and vector control deployment data. The simulations were run for different transmission intensities per region and five interventions, currently or potentially included in the National Malaria Strategic Plan, individually and in combination. The simulated prevalences were fitted to council specific prevalences derived from geostatistical models to obtain council specific predictions of the prevalence and number of cases between 2017 and 2020. The predictions were used to evaluate in silico the feasibility of the national target of reaching a prevalence of below 1% by 2020, and to suggest alternative intervention stratifications for the country. RESULTS The historical prevalence trend was fitted for each council with an agreement of 87% in 2016 (95%CI: 0.84-0.90) and an agreement of 90% for the historical trend (2003-2016) (95%CI: 0.87-0.93) The current national malaria strategy was expected to reduce the malaria prevalence between 2016 and 2020 on average by 23.8% (95% CI: 19.7%-27.9%) if current case management levels were maintained, and by 52.1% (95% CI: 48.8%-55.3%) if the case management were improved. Insecticide treated nets and case management were the most cost-effective interventions, expected to reduce the prevalence by 25.0% (95% CI: 19.7%-30.2) and to avert 37 million cases between 2017 and 2020. Mass drug administration was included in most councils in the stratification selected for meeting the national target at minimal costs, expected to reduce the prevalence by 77.5% (95%CI: 70.5%-84.5%) and to avert 102 million cases, with almost twice higher costs than those of the current national strategy. In summary, the model suggested that current interventions are not sufficient to reach the national aim of a prevalence of less than 1% by 2020 and a revised strategic plan needs to consider additional, more effective interventions, especially in high transmission areas and that the targets need to be revisited. CONCLUSION The methodology reported here is based on intensive interactions with the NMCP and provides a helpful tool for assessing the feasibility of country specific targets and for determining which intervention stratifications at sub-national level will have most impact. This country-led application could support strategic planning of malaria control in many other malaria endemic countries.
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Affiliation(s)
- Manuela Runge
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Robert W. Snow
- Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, England, United Kingodm
- Population Health Unit, Kenya Medical Research Institute-Wellcome Trust Research Programme, Nairobi, Kenya
| | - Fabrizio Molteni
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- National Malaria Control Programme (NMCP), Dar es Salaam, Tanzania
| | - Sumaiyya Thawer
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- National Malaria Control Programme (NMCP), Dar es Salaam, Tanzania
| | - Ally Mohamed
- National Malaria Control Programme (NMCP), Dar es Salaam, Tanzania
| | - Renata Mandike
- National Malaria Control Programme (NMCP), Dar es Salaam, Tanzania
| | - Emanuele Giorgi
- CHICAS, Lancaster Medical School, Lancaster University, Lancaster, England, United Kingodm
| | - Peter M. Macharia
- Population Health Unit, Kenya Medical Research Institute-Wellcome Trust Research Programme, Nairobi, Kenya
| | - Thomas A. Smith
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Christian Lengeler
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Emilie Pothin
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
- Clinton Health Access Initiative, Boston, Massachusetts, United States of America
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Msugupakulya BJ, Kaindoa EW, Ngowo HS, Kihonda JM, Kahamba NF, Msaky DS, Matoke-Muhia D, Tungu PK, Okumu FO. Preferred resting surfaces of dominant malaria vectors inside different house types in rural south-eastern Tanzania. Malar J 2020; 19:22. [PMID: 31941508 PMCID: PMC6964015 DOI: 10.1186/s12936-020-3108-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Accepted: 01/07/2020] [Indexed: 02/04/2023] Open
Abstract
Background Malaria control in Africa relies extensively on indoor residual spraying (IRS) and insecticide-treated nets (ITNs). IRS typically targets mosquitoes resting on walls, and in few cases, roofs and ceilings, using contact insecticides. Unfortunately, little attention is paid to where malaria vectors actually rest indoors, and how such knowledge could be used to improve IRS. This study investigated preferred resting surfaces of two major malaria vectors, Anopheles funestus and Anopheles arabiensis, inside four common house types in rural south-eastern Tanzania. Methods The assessment was done inside 80 houses including: 20 with thatched roofs and mud walls, 20 with thatched roofs and un-plastered brick walls, 20 with metal roofs and un-plastered brick walls, and 20 with metal roofs and plastered brick walls, across four villages. In each house, resting mosquitoes were sampled in mornings (6 a.m.–8 a.m.), evenings (6 p.m.–8 p.m.) and at night (11 p.m.–12.00 a.m.) using Prokopack aspirators from multiple surfaces (walls, undersides of roofs, floors, furniture, utensils, clothing, curtains and bed nets). Results Overall, only 26% of An. funestus and 18% of An. arabiensis were found on walls. In grass-thatched houses, 33–55% of An. funestus and 43–50% of An. arabiensis rested under roofs, while in metal-roofed houses, only 16–20% of An. funestus and 8–30% of An. arabiensis rested under roofs. Considering all data together, approximately 40% of mosquitoes rested on surfaces not typically targeted by IRS, i.e. floors, furniture, utensils, clothing and bed nets. These proportions were particularly high in metal-roofed houses (47–53% of An. funestus; 60–66% of An. arabiensis). Conclusion While IRS typically uses contact insecticides to target adult mosquitoes on walls, and occasionally roofs and ceilings, significant proportions of vectors rest on surfaces not usually sprayed. This gap exceeds one-third of malaria mosquitoes in grass-thatched houses, and can reach two-thirds in metal-roofed houses. Where field operations exclude roofs during IRS, the gaps can be much greater. In conclusion, there is need for locally-obtained data on mosquito resting behaviours and how these influence the overall impact and costs of IRS. This study also emphasizes the need for alternative approaches, e.g. house screening, which broadly tackle mosquitoes beyond areas reachable by IRS and ITNs.
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Affiliation(s)
- Betwel J Msugupakulya
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania. .,School of Life Science and Bioengineering, The Nelson Mandela African Institution of Science and Technology, P. O. Box 447, Arusha, Tanzania.
| | - Emmanuel W Kaindoa
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania.,School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Halfan S Ngowo
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania.,Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Japhet M Kihonda
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania
| | - Najat F Kahamba
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania.,School of Life Science and Bioengineering, The Nelson Mandela African Institution of Science and Technology, P. O. Box 447, Arusha, Tanzania
| | - Dickson S Msaky
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania
| | - Damaris Matoke-Muhia
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania.,Centre for Biotechnology Research and Development, Kenya Medical Research Institute, Nairobi, Kenya
| | - Patrick K Tungu
- Amani Medical Research Centre, National Institute of Medical Research, Muheza, Tanzania
| | - Fredros O Okumu
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania. .,School of Life Science and Bioengineering, The Nelson Mandela African Institution of Science and Technology, P. O. Box 447, Arusha, Tanzania. .,School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa. .,Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, G12 8QQ, UK.
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Swai JK, Mmbando AS, Ngowo HS, Odufuwa OG, Finda MF, Mponzi W, Nyoni AP, Kazimbaya D, Limwagu AJ, Njalambaha RM, Abbasi S, Moore SJ, Schellenberg J, Lorenz LM, Okumu FO. Protecting migratory farmers in rural Tanzania using eave ribbons treated with the spatial mosquito repellent, transfluthrin. Malar J 2019; 18:414. [PMID: 31823783 PMCID: PMC6905030 DOI: 10.1186/s12936-019-3048-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Accepted: 12/02/2019] [Indexed: 01/08/2023] Open
Abstract
Background Many subsistence farmers in rural southeastern Tanzania regularly relocate to distant farms in river valleys to tend to crops for several weeks or months each year. While there, they live in makeshift semi-open structures, usually far from organized health systems and where insecticide-treated nets (ITNs) do not provide adequate protection. This study evaluated the potential of a recently developed technology, eave ribbons treated with the spatial repellent transfluthrin, for protecting migratory rice farmers in rural southeastern Tanzania against indoor-biting and outdoor-biting mosquitoes. Methods In the first test, eave ribbons (0.1 m × 24 m each) treated with 1.5% transfluthrin solution were compared to untreated ribbons in 24 randomly selected huts in three migratory communities over 48 nights. Host-seeking mosquitoes indoors and outdoors were monitored nightly (18.00–07.00 h) using CDC light traps and CO2-baited BG malaria traps, respectively. The second test compared efficacies of eave ribbons treated with 1.5% or 2.5% transfluthrin in 12 huts over 21 nights. Finally, 286 farmers were interviewed to assess perceptions about eave ribbons, and their willingness to pay for them. Results In the two experiments, when treated eave ribbons were applied, the reduction in indoor densities ranged from 56 to 77% for Anopheles arabiensis, 36 to 60% for Anopheles funestus, 72 to 84% for Culex, and 80 to 98% for Mansonia compared to untreated ribbons. Reduction in outdoor densities was 38 to 77% against An. arabiensis, 36 to 64% against An. funestus, 63 to 88% against Culex, and 47 to 98% against Mansonia. There was no difference in protection between the two transfluthrin doses. In the survey, 58% of participants perceived the ribbons to be effective in reducing mosquito bites. Ninety per cent were willing to pay for the ribbons, the majority of whom were willing to pay but less than US$2.17 (5000 TZS), one-third of the current prototype cost. Conclusions Transfluthrin-treated eave ribbons can protect migratory rice farmers, living in semi-open makeshift houses in remote farms, against indoor-biting and outdoor-biting mosquitoes. The technology is acceptable to users and could potentially complement ITNs. Further studies should investigate durability and epidemiological impact of eave ribbons, and the opportunities for improving affordability to users.
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Affiliation(s)
- Johnson K Swai
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania.
| | - Arnold S Mmbando
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Halfan S Ngowo
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania.,Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Olukayode G Odufuwa
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Marceline F Finda
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania.,School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Winifrida Mponzi
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Anna P Nyoni
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Deogratius Kazimbaya
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Alex J Limwagu
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Rukiyah M Njalambaha
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Saidi Abbasi
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Sarah J Moore
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania.,Swiss Tropical and Public Health Institute, Socinstrasse. 57, 4002, Basel 4, Switzerland.,University of Basel, St. Petersplatz 1, 4002, Basel, Switzerland
| | - Joanna Schellenberg
- Department of Disease Control, Faculty of Infectious and Tropical Disease, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK
| | - Lena M Lorenz
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania.,Department of Disease Control, Faculty of Infectious and Tropical Disease, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK
| | - Fredros O Okumu
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania.,Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, G12 8QQ, UK.,School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.,School of Life Science and Bioengineering, The Nelson Mandela African, Institution of Science and Technology, P. O. Box 447, Arusha, Tanzania
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Abstract
BACKGROUND Larviciding refers to the regular application of chemical or microbial insecticides to water bodies or water containers to kill the aquatic immature forms of the mosquito (the larvae and pupae). OBJECTIVES To summarize research evidence evaluating whether larviciding with chemical or microbial insecticides prevents malaria transmission. SEARCH METHODS We searched the Cochrane Infectious Diseases Group Specialized Register; the Cochrane Central Register of Controlled Trials (CENTRAL), published in the Cochrane Library; MEDLINE; Embase; CAB Abstracts; LILACS; the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP); ClinicalTrials.gov; and the ISRCTN registry up to 6 June 2019. SELECTION CRITERIA We included cluster-randomized controlled trials (cRCTs), interrupted time series (ITS), randomized cross-over studies, non-randomized cross-over studies, and controlled before-and-after studies (CBAs) that compared larviciding with no larviciding. DATA COLLECTION AND ANALYSIS We independently assessed trials for eligibility and risk of bias, and extracted data. We assessed the certainty of evidence using the GRADE approach. MAIN RESULTS Four studies (one cRCT, two CBAs, and one non-randomized cross-over design) met the inclusion criteria. All used ground application of larvicides (people hand-delivering larvicides); one evaluated chemical and three evaluated microbial agents. Studies were carried out in The Gambia, Tanzania, Kenya, and Sri Lanka. Three studies were conducted in areas where mosquito aquatic habitats were less extensive (< 1 km²), and one where habitats were more extensive (> 1 km²; a cross-over study from The Gambia).For aquatic habitats of less than 1 km², one cRCT randomized eight villages in Sri Lanka to evaluate chemical larviciding using insect growth regulator; and two CBA studies undertaken in Kenya and Tanzania evaluated microbial larvicides. In the cRCT, larviciding across all villages was associated with lower malaria incidence (rate ratio 0.24, 4649 participants, low-certainty evidence) and parasite prevalence (risk ratio (RR) 0.26, 5897 participants, low-certainty evidence) compared to no larviciding. The two CBA studies reported lower malaria prevalence during the intervention period (parasite prevalence RR 0.79, 95% confidence interval (CI) 0.71 to 0.89; 70,902 participants; low-certainty evidence). The Kenyan study also reported a reduction in the incidence of new malaria cases (RR 0.62, 95% CI 0.38 to 1.01; 720 participants; very low-certainty evidence).For aquatic habitats of more than 1 km², the non-randomized cross-over trial using microbial larvicides did not detect an effect for malaria incidence (RR 1.58, 95% CI 0.94 to 2.65; 4226 participants), or parasite prevalence (RR 1.15, 95% CI 0.41 to 3.20; 3547 participants); both were very low-certainty evidence. The Gambia trial also reported the mean haemoglobin level, and there was no difference across the four comparisons (mean difference -0.13, 95% CI -0.40 to 0.13; 3586 participants).We were unable to summarize or pool entomological outcomes due to unreported and missing data. AUTHORS' CONCLUSIONS Most controlled studies on larviciding have been performed with microbial agents. Ground larviciding for non-extensive larval habitats may have an effect on malaria transmission, and we do not know if there is an effect in large-scale aquatic habitats. We found no studies using larviciding application techniques that could cover large aquatic habitats, such as aerial spraying using aircraft.
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Affiliation(s)
- Leslie Choi
- Liverpool School of Tropical MedicineDepartment of Clinical SciencesPembroke PlaceLiverpoolUKL3 5QA
| | | | - Anne L Wilson
- Durham UniversityDepartment of BiosciencesStockton RoadDurhamUK
- Liverpool School of Tropical MedicineDepartment of Vector BiologyLiverpoolUK
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Batista EPA, Mapua SA, Ngowo H, Matowo NS, Melo EF, Paixão KS, Eiras AE, Okumu FO. Videographic analysis of flight behaviours of host-seeking Anopheles arabiensis towards BG-Malaria trap. PLoS One 2019; 14:e0220563. [PMID: 31365584 PMCID: PMC6668822 DOI: 10.1371/journal.pone.0220563] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Accepted: 07/18/2019] [Indexed: 11/19/2022] Open
Abstract
The BG-Malaria trap (BGM) is an adaptation of the well-known BG-Sentinel trap (BGS) with greater trapping efficiencies for anopheline and culicine mosquitoes. Its continued optimization requires greater understanding of mosquito flight behaviors near it. We used three high-resolution infrared cameras (68 frames/second) to track flight behaviors of laboratory-reared Anopheles arabiensis females in vicinity of the BGM in comparison with BGS. Additional comparisons were done for BGM at 20, 40 and 80cm heights, and for BGMs baited with Ifakara blend plus CO2, CO2 alone, or no bait. More mosquitoes were observed near BGM than BGS. Both BGMs installed 20cm above the floor and baited with CO2 received more visits by host-seeking mosquitoes than the other BGMs evaluated in their respective experiments. Trap designs, height and attractants all influence mosquito activity in vicinity of the traps which can be readily visualized using infrared cameras to accelerate trap development and testing. The greater activity of host-seeking mosquitoes near BGM than BGS supports the proven superiority of BGM traps in field and semi-field settings.
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Affiliation(s)
- Elis P. A. Batista
- Laboratory of Innovation Technologies in Vector Control, Department of Parasitology, Biological Sciences Institute, Federal University of Minas Gerais, Belo Horizonte, Brazil
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Ifakara, Tanzania
| | - Salum A. Mapua
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Ifakara, Tanzania
- School of Life Sciences, University of Keele, Staffordshire, United Kingdom
- School of Environment and Life Sciences, University of Salford, Manchester, United Kingdom
| | - Halfan Ngowo
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Ifakara, Tanzania
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
| | - Nancy S. Matowo
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Ifakara, Tanzania
- University of Basel, Basel, Switzerland
- Swiss Tropical and Public Health Institute, Basel, Switzerland
| | - Elizangela F. Melo
- Laboratory of Innovation Technologies in Vector Control, Department of Parasitology, Biological Sciences Institute, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Kelly S. Paixão
- Laboratory of Innovation Technologies in Vector Control, Department of Parasitology, Biological Sciences Institute, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Alvaro E. Eiras
- Laboratory of Innovation Technologies in Vector Control, Department of Parasitology, Biological Sciences Institute, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Fredros O. Okumu
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Ifakara, Tanzania
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
- School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Parktown, Republic of South Africa
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Abstract
For the control and elimination of malaria, information on the local vector dynamics is essential. This information provides guidance on appropriate and timely deployment of vector control tools and their subsequent success. The data on the dynamics of local mosquito populations can be collected using many different Anopheles sampling methods. Dependent on the objectives, resources, time, and local environment, different traps and methods can be chosen. This chapter describes the sampling of adult populations, focusing on the important preparatory stages and some of the widely used sampling methods. The trapping methods discussed in this chapter are the human landing catch, human-baited net trap, animal landing catch, animal-baited net trap, CDC miniature light trap, Biogents Suna trap, peripheral net collection, pyrethrum collection, exit/entry trap, and resting shelter. For optimal deployment in the field, a step-by-step description of the sampling methods is given.
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Tchouakui M, Chiang MC, Ndo C, Kuicheu CK, Amvongo-Adjia N, Wondji MJ, Tchoupo M, Kusimo MO, Riveron JM, Wondji CS. A marker of glutathione S-transferase-mediated resistance to insecticides is associated with higher Plasmodium infection in the African malaria vector Anopheles funestus. Sci Rep 2019; 9:5772. [PMID: 30962458 PMCID: PMC6453935 DOI: 10.1038/s41598-019-42015-1] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Accepted: 03/13/2019] [Indexed: 01/02/2023] Open
Abstract
Metabolic resistance to insecticides is threatening malaria control in Africa. However, the extent to which it impacts malaria transmission remains unclear. Here, we investigated the association between a marker of glutathione S-transferase mediated metabolic resistance and Plasmodium infection in field population of Anopheles funestus s.s. in comparison to the A296S-RDL target site mutation. The 119F-GSTe2 resistant allele was present in southern (Obout) (56%) and central (Mibellon) (25%) regions of Cameroon whereas the 296S-RDL resistant allele was detected at 98.5% and 15% respectively. The whole mosquito Plasmodium and sporozoite infection rates were 57% and 14.8% respectively in Obout (n = 508) and 19.7% and 5% in Mibellon (n = 360). No association was found between L119F-GSTe2 genotypes and whole mosquito infection status. However, when analyzing oocyst and sporozoite infection rates separately, the resistant homozygote 119F/F genotype was significantly more associated with Plasmodium infection in Obout than both heterozygote (OR = 2.5; P = 0.012) and homozygote susceptible (L/L119) genotypes (OR = 2.10; P = 0.013). In contrast, homozygote RDL susceptible mosquitoes (A/A296) were associated more frequently with Plasmodium infection than other genotypes (OR = 4; P = 0.03). No additive interaction was found between L119F and A296S. Sequencing of the GSTe2 gene showed no association between the polymorphism of this gene and Plasmodium infection. Glutathione S-transferase metabolic resistance is potentially increasing the vectorial capacity of resistant An. funestus mosquitoes. This could result in a possible exacerbation of malaria transmission in areas of high GSTe2-based metabolic resistance to insecticides.
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Affiliation(s)
- Magellan Tchouakui
- Research Unit LSTM/OCEAC, P.O. BOX 288, Yaoundé, Cameroon. .,Centre for Research in Infectious Diseases (CRID), P.O. BOX 13591, Yaoundé, Cameroon. .,Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé 1, P.O. Box 812, Yaoundé, Cameroon.
| | - Mu-Chun Chiang
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, L35QA, Liverpool, UK
| | - Cyrille Ndo
- Research Unit LSTM/OCEAC, P.O. BOX 288, Yaoundé, Cameroon.,Centre for Research in Infectious Diseases (CRID), P.O. BOX 13591, Yaoundé, Cameroon.,University of Douala, P.O. Box 2701, Douala, Cameroon
| | - Carine K Kuicheu
- Research Unit LSTM/OCEAC, P.O. BOX 288, Yaoundé, Cameroon.,Centre for Research in Infectious Diseases (CRID), P.O. BOX 13591, Yaoundé, Cameroon.,Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé 1, P.O. Box 812, Yaoundé, Cameroon
| | - Nathalie Amvongo-Adjia
- Research Unit LSTM/OCEAC, P.O. BOX 288, Yaoundé, Cameroon.,Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé 1, P.O. Box 812, Yaoundé, Cameroon.,Centre for Medical Research, Institute of Medical Research and Medicinal Plants Studies (IMPM), P.O. Box 13033, Yaoundé, Cameroon
| | - Murielle J Wondji
- Research Unit LSTM/OCEAC, P.O. BOX 288, Yaoundé, Cameroon.,Centre for Research in Infectious Diseases (CRID), P.O. BOX 13591, Yaoundé, Cameroon.,Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, L35QA, Liverpool, UK
| | - Micareme Tchoupo
- Research Unit LSTM/OCEAC, P.O. BOX 288, Yaoundé, Cameroon.,Centre for Research in Infectious Diseases (CRID), P.O. BOX 13591, Yaoundé, Cameroon
| | - Michael O Kusimo
- Centre for Research in Infectious Diseases (CRID), P.O. BOX 13591, Yaoundé, Cameroon
| | - Jacob M Riveron
- Research Unit LSTM/OCEAC, P.O. BOX 288, Yaoundé, Cameroon.,Centre for Research in Infectious Diseases (CRID), P.O. BOX 13591, Yaoundé, Cameroon.,Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, L35QA, Liverpool, UK
| | - Charles S Wondji
- Research Unit LSTM/OCEAC, P.O. BOX 288, Yaoundé, Cameroon. .,Centre for Research in Infectious Diseases (CRID), P.O. BOX 13591, Yaoundé, Cameroon. .,Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, L35QA, Liverpool, UK.
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59
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Matiya DJ, Philbert AB, Kidima W, Matowo JJ. Dynamics and monitoring of insecticide resistance in malaria vectors across mainland Tanzania from 1997 to 2017: a systematic review. Malar J 2019; 18:102. [PMID: 30914051 PMCID: PMC6434877 DOI: 10.1186/s12936-019-2738-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 03/20/2019] [Indexed: 11/22/2022] Open
Abstract
Background Malaria still claims substantial lives of individuals in Tanzania. Insecticide-treated nets (ITNs) and indoor residual spray (IRS) are used as major malaria vector control tools. These tools are facing great challenges from the rapid escalating insecticide resistance in malaria vector populations. This review presents the information on the dynamics and monitoring of insecticide resistance in malaria vectors in mainland Tanzania since 1997. The information is important to policy-makers and other vector control stakeholders to reflect and formulate new resistance management plans in the country. Methods Reviewed articles on susceptibility and mechanisms of resistance in malaria vectors to insecticides across mainland Tanzania were systematically searched from the following databases: PubMed, Google scholar, HINARI and AGORA. The inclusion criteria were articles published between 2000 and 2017, reporting susceptibility of malaria vectors to insecticides, mechanisms of resistance in the mainland Tanzania, involving field collected adult mosquitoes, and mosquitoes raised from the field collected larvae. Exclusion criteria were articles reporting insecticide resistance in larval bio-assays, laboratory strains, and unpublished data. Reviewed information include year of study, malaria vectors, insecticides, and study sites. This information was entered in the excel sheet and analysed. Results A total of 30 articles met the selection criteria. The rapid increase of insecticide resistance in the malaria vectors across the country was reported since year 2006 onwards. Insecticide resistance in Anopheles gambiae sensu lato (s.l.) was detected in at least one compound in each class of all recommended insecticide classes. However, the Anopheles funestus s.l. is highly resistant to pyrethroids and DDT. Knockdown resistance (kdr) mechanism in An. gambiae s.l. is widely studied in the country. Biochemical resistance by detoxification enzymes (P450s, NSE and GSTs) in An. gambiae s.l. was also recorded. Numerous P450s genes associated with metabolic resistance were over transcribed in An. gambiae s.l. collected from agricultural areas. However, no study has reported mechanisms of insecticide resistance in the An. funestus s.l. in the country. Conclusion This review has shown the dynamics and monitoring of insecticide resistance in malaria vector populations across mainland Tanzanian. This highlights the need for devising improved control approaches of the malaria vectors in the country.
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Affiliation(s)
- Deokary Joseph Matiya
- Dar es Salaam University College of Education (DUCE), P.O. Box 2329, Dar es Salaam, Tanzania. .,University of Dar es Salaam (UDSM), P.O. Box 35064, Dar es Salaam, Tanzania.
| | - Anitha B Philbert
- University of Dar es Salaam (UDSM), P.O. Box 35064, Dar es Salaam, Tanzania
| | - Winifrida Kidima
- University of Dar es Salaam (UDSM), P.O. Box 35064, Dar es Salaam, Tanzania
| | - Johnson J Matowo
- Kilimanjaro Christian Medical University College (KCMUCo), P.O. Box 2240, Moshi, Tanzania
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60
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Meza FC, Kreppel KS, Maliti DF, Mlwale AT, Mirzai N, Killeen GF, Ferguson HM, Govella NJ. Mosquito electrocuting traps for directly measuring biting rates and host-preferences of Anopheles arabiensis and Anopheles funestus outdoors. Malar J 2019; 18:83. [PMID: 30885205 PMCID: PMC6423841 DOI: 10.1186/s12936-019-2726-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 03/13/2019] [Indexed: 11/26/2022] Open
Abstract
Background Mosquito biting rates and host preferences are crucial determinants of human exposure to vector-borne diseases and the impact of vector control measures. The human landing catch (HLC) is a gold standard method for measuring human exposure to bites, but presents risks to participants by requiring some exposure to mosquito vectors. Mosquito electrocuting traps (METs) represent an exposure-free alternative to HLCs for measuring human exposure to malaria vectors. However, original MET prototypes were too small for measuring whole-body biting rates on humans or large animals like cattle. Here a much larger MET capable of encompassing humans or cattle was designed, and its performance was evaluated relative to both the original small MET and HLC and for quantifying malaria vector host preferences. Methods Human landing catch, small human-baited METs (MET-SH), and large METs baited with either a human (MET-LH) or calves (MET-LC) were simultaneously used to capture wild malaria vectors outdoors in rural southern Tanzania. The four capture methods were compared in a Latin-square design over 20 nights. Malaria vector host preferences were estimated through comparison of the number of mosquitoes caught by large METs baited with either humans or cattle. Results The MET-LH caught more than twice as many Anopheles arabiensis than either the MET-SH or HLC. It also caught higher number of Anopheles funestus sensu lato (s.l.) compared to the MET-SH or HLC. Similar numbers of An. funestus sensu stricto (s.s.) were caught in MET-LH and MET-SH collections. Catches of An. arabiensis with human or cattle-baited large METs were similar, indicating no clear preference for either host. In contrast, An. funestus s.s. exhibited a strong, but incomplete preference for humans. Conclusions METs are a sensitive, practical tool for assessing mosquito biting rates and host preferences, and represent a safer alternative to the HLC. Additionally these findings suggest the HLC underestimate whole-body human exposure. MET collections indicated the An. funestus s.s. population in this setting had a higher than expected attack rate on cattle, potentially making eliminating of this species more difficult with human-targetted control measures. Supplementary vector control tools targetted at livestock may be required to effectively tackle this species.
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Affiliation(s)
- Felician C Meza
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Off Mlabani Passage, P.O. Box 53, Ifakara, Tanzania.
| | - Katharina S Kreppel
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Off Mlabani Passage, P.O. Box 53, Ifakara, Tanzania.,Animal Health and Comparative Medicine, Institute of Biodiversity, University of Glasgow, Graham Kerr Building, Glasgow, G12 8QQ, UK
| | - Deodatus F Maliti
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Off Mlabani Passage, P.O. Box 53, Ifakara, Tanzania.,Animal Health and Comparative Medicine, Institute of Biodiversity, University of Glasgow, Graham Kerr Building, Glasgow, G12 8QQ, UK
| | - Amos T Mlwale
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Off Mlabani Passage, P.O. Box 53, Ifakara, Tanzania
| | - Nosrat Mirzai
- Bioelectronics Unit, University of Glasgow, Graham Kerr Building, Glasgow, G12 8QQ, UK
| | - Gerry F Killeen
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Off Mlabani Passage, P.O. Box 53, Ifakara, Tanzania.,Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Heather M Ferguson
- Animal Health and Comparative Medicine, Institute of Biodiversity, University of Glasgow, Graham Kerr Building, Glasgow, G12 8QQ, UK
| | - Nicodem J Govella
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Off Mlabani Passage, P.O. Box 53, Ifakara, Tanzania.,Animal Health and Comparative Medicine, Institute of Biodiversity, University of Glasgow, Graham Kerr Building, Glasgow, G12 8QQ, UK
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61
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Kaindoa EW, Ngowo HS, Limwagu AJ, Tchouakui M, Hape E, Abbasi S, Kihonda J, Mmbando AS, Njalambaha RM, Mkandawile G, Bwanary H, Coetzee M, Okumu FO. Swarms of the malaria vector Anopheles funestus in Tanzania. Malar J 2019; 18:29. [PMID: 30696441 PMCID: PMC6350364 DOI: 10.1186/s12936-019-2660-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Accepted: 01/18/2019] [Indexed: 11/10/2022] Open
Abstract
Background Anopheles funestus mosquitoes currently contribute more than 85% of ongoing malaria transmission events in south-eastern Tanzania, even though they occur in lower densities than other vectors, such as Anopheles arabiensis. Unfortunately, the species ecology is minimally understood, partly because of difficulties in laboratory colonization. This study describes the first observations of An. funestus swarms in Tanzania, possibly heralding new opportunities for control. Method Using systematic searches by community-based volunteers and expert entomologists, An. funestus swarms were identified in two villages in Ulanga and Kilombero districts in south-eastern Tanzania, starting June 2018. Swarms were characterized by size, height, start- and end-times, presence of copulation and associated environmental features. Samples of male mosquitoes from the swarms were examined for sexual maturity by observing genitalia rotation, species identity using polymerase chain reaction and wing sizes. Results 581 An. funestus (98.1% males (n = 570) and 1.9% (n = 11) females) and 9 Anopheles gambiae sensu lato (s.l.) males were sampled using sweep nets from the 81 confirmed swarms in two villages (Ikwambi in Kilombero district and Tulizamoyo in Ulanga district). Six copulation events were observed in the swarms. Mean density (95% CL) of An. funestus caught/swarm/village/evening was 6.6 (5.9–7.2) in Tulizamoyo and 10.8 (5.8–15.8) in Ikwambi. 87.7% (n = 71) of the swarms were found in Tulizamoyo, while 12.3% (n = 10) were in Ikwambi. Mean height of swarms was 1.7 m (0.9–2.5 m), while mean duration was 12.9 (7.9–17.9) minutes. The PCR analysis confirmed that 100% of all An. funestus s.l. samples processed were An. funestus sensu stricto. Mean wing length of An. funestus males was 2.47 mm (2.0–2.8 mm), but there was no difference between swarming males and indoor-resting males. Most swarms (95.0%) occurred above bare ground, sometime on front lawns near human dwellings, and repeatedly in the same locations. Conclusion This study has demonstrated occurrence of An. funestus swarms for the first time in Tanzania. Further investigations could identify new opportunities for improved control of this dominant malaria vector, possibly by targeting the swarms.
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Affiliation(s)
- Emmanuel W Kaindoa
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania. .,School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
| | - Halfan S Ngowo
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania
| | - Alex J Limwagu
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania
| | - Magellan Tchouakui
- Centre for Research in Infectious Diseases (CRID), P.O. BOX 13591, Yaoundé, Cameroon
| | - Emmanuel Hape
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania
| | - Said Abbasi
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania
| | - Japhet Kihonda
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania
| | - Arnold S Mmbando
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania
| | - Rukiyah M Njalambaha
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania
| | - Gustav Mkandawile
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania
| | - Hamis Bwanary
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania
| | - Maureen Coetzee
- School of Pathology, Faculty of Health Sciences, Wits Research Institute for Malaria and Wits/MRC Collaborating Centre for Multidisciplinary Research on Malaria, University of the Witwatersrand, Johannesburg, South Africa.,Centre for Emerging Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg, South Africa
| | - Fredros O Okumu
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania.,School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.,Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, G12 8QQ, UK
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62
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Tchouakui M, Riveron JM, Djonabaye D, Tchapga W, Irving H, Soh Takam P, Njiokou F, Wondji CS. Fitness Costs of the Glutathione S-Transferase Epsilon 2 (L119F-GSTe2) Mediated Metabolic Resistance to Insecticides in the Major African Malaria Vector Anopheles Funestus. Genes (Basel) 2018; 9:E645. [PMID: 30572680 PMCID: PMC6316527 DOI: 10.3390/genes9120645] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 12/07/2018] [Accepted: 12/17/2018] [Indexed: 01/18/2023] Open
Abstract
Metabolic resistance to insecticides threatens malaria control. However, little is known about its fitness cost in field populations of malaria vectors, thus limiting the design of suitable resistance management strategies. Here, we assessed the association between the glutathione S-transferase GSTe2-mediated metabolic resistance and life-traits of natural populations of Anopheles funestus. A total of 1200 indoor resting blood-fed female An. funestus (F₀) were collected in Mibellon, Cameroon (2016/2017), and allowed to lay eggs individually. Genotyping of F1 mosquitoes for the L119F-GSTE2 mutation revealed that L/L119-homozygote susceptible (SS) mosquitoes significantly laid more eggs than heterozygotes L119F-RS (odds ratio (OR) = 2.06; p < 0.0001) and homozygote resistant 119F/F-RR (OR = 2.93; p < 0.0001). L/L119-SS susceptible mosquitoes also showed the higher ability for oviposition than 119F/F-RR resistant (OR = 2.68; p = 0.0002) indicating a reduced fecundity in resistant mosquitoes. Furthermore, L119F-RS larvae developed faster (nine days) than L119F-RR and L119F-SS (11 days) (X² = 11.052; degree of freedom (df) = 4; p = 0.02) suggesting a heterozygote advantage effect for larval development. Interestingly, L/L119-SS developed faster than 119F/F-RR (OR = 5.3; p < 0.0001) revealing an increased developmental time in resistant mosquitoes. However, genotyping and sequencing revealed that L119F-RR mosquitoes exhibited a higher adult longevity compared to RS (OR > 2.2; p < 0.05) and SS (OR > 2.1; p < 0.05) with an increased frequency of GSTe2-resistant haplotypes in mosquitoes of D30 after adult emergence. Additionally, comparison of the expression of GSTe2 revealed a significantly increased expression from D1-D30 after emergence of adults (Anova test (F) = 8; df= 3; p = 0.008). The negative association between GSTe2 and some life traits of An. funestus could facilitate new resistance management strategies. However, the increased longevity of GSTe2-resistant mosquitoes suggests that an increase in resistance could exacerbate malaria transmission.
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Affiliation(s)
- Magellan Tchouakui
- LSTM Research Unit at the Centre for Research in Infectious Diseases (CRID), P.O. Box 13591 Yaoundé, Cameroon.
- Parasitology and Ecology Laboratory, Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé 1, P.O. Box 812 Yaoundé, Cameroon.
| | - Jacob M Riveron
- LSTM Research Unit at the Centre for Research in Infectious Diseases (CRID), P.O. Box 13591 Yaoundé, Cameroon.
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L35QA, UK.
| | - Doumani Djonabaye
- LSTM Research Unit at the Centre for Research in Infectious Diseases (CRID), P.O. Box 13591 Yaoundé, Cameroon.
- Department of Biochemistry, Faculty of Science, University of Yaoundé 1, P.O. Box 812 Yaoundé, Cameroon.
| | - Williams Tchapga
- LSTM Research Unit at the Centre for Research in Infectious Diseases (CRID), P.O. Box 13591 Yaoundé, Cameroon.
| | - Helen Irving
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L35QA, UK.
| | - Patrice Soh Takam
- Department of Mathematics, Faculty of Science, University of Yaoundé 1, P.O. Box 812 Yaoundé, Cameroon.
| | - Flobert Njiokou
- LSTM Research Unit at the Centre for Research in Infectious Diseases (CRID), P.O. Box 13591 Yaoundé, Cameroon.
- Parasitology and Ecology Laboratory, Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé 1, P.O. Box 812 Yaoundé, Cameroon.
| | - Charles S Wondji
- LSTM Research Unit at the Centre for Research in Infectious Diseases (CRID), P.O. Box 13591 Yaoundé, Cameroon.
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L35QA, UK.
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Baldini F, Rougé J, Kreppel K, Mkandawile G, Mapua SA, Sikulu-Lord M, Ferguson HM, Govella N, Okumu FO. First report of natural Wolbachia infection in the malaria mosquito Anopheles arabiensis in Tanzania. Parasit Vectors 2018; 11:635. [PMID: 30545384 PMCID: PMC6293665 DOI: 10.1186/s13071-018-3249-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Accepted: 11/30/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Natural infections of the endosymbiont bacteria Wolbachia have recently been discovered in populations of the malaria mosquito Anopheles gambiae (s.l.) in Burkina Faso and Mali, West Africa. This Anopheles specific strain wAnga limits the malaria parasite Plasmodium falciparum infections in the mosquito, thus it offers novel opportunities for malaria control. RESULTS We investigated Wolbachia presence in Anopheles arabiensis and Anopheles funestus, which are the two main malaria vectors in the Kilombero Valley, a malaria endemic region in south-eastern Tanzania. We found 3.1% (n = 65) and 7.5% (n = 147) wAnga infection prevalence in An. arabiensis in mosquitoes collected in 2014 and 2016, respectively, while no infection was detected in An. funestus (n = 41). Phylogenetic analysis suggests that at least two distinct strains of wAnga were detected, both belonging to Wolbachia supergroup A and B. CONCLUSIONS To our knowledge, this is the first confirmation of natural Wolbachia in malaria vectors in Tanzania, which opens novel questions on the ecological and genetic basis of its persistence and pathogen transmission in the vector hosts. Understanding the basis of interactions between Wolbachia, Anopheles mosquitoes and malaria parasites is crucial for investigation of its potential application as a biocontrol strategy to reduce malaria transmission, and assessment of how natural wAnga infections influence pathogen transmission in different ecological settings.
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Affiliation(s)
- Francesco Baldini
- Institute of Biodiversity Animal Health and Comparative Medicine, University of Glasgow, Glasgow, G12 8QQ UK
| | - Justine Rougé
- Institute of Biodiversity Animal Health and Comparative Medicine, University of Glasgow, Glasgow, G12 8QQ UK
| | - Katharina Kreppel
- Institute of Biodiversity Animal Health and Comparative Medicine, University of Glasgow, Glasgow, G12 8QQ UK
- Environmental Health & Ecological Sciences Department, Ifakara Health Institute, Off Mlabani Passage, PO Box 53, Ifakara, Tanzania
| | - Gustave Mkandawile
- Environmental Health & Ecological Sciences Department, Ifakara Health Institute, Off Mlabani Passage, PO Box 53, Ifakara, Tanzania
| | - Salum Abdallah Mapua
- Environmental Health & Ecological Sciences Department, Ifakara Health Institute, Off Mlabani Passage, PO Box 53, Ifakara, Tanzania
| | - Maggy Sikulu-Lord
- The School of Public Health, The University of Queensland, Sydney, Queensland Australia
| | - Heather M. Ferguson
- Institute of Biodiversity Animal Health and Comparative Medicine, University of Glasgow, Glasgow, G12 8QQ UK
| | - Nicodem Govella
- Environmental Health & Ecological Sciences Department, Ifakara Health Institute, Off Mlabani Passage, PO Box 53, Ifakara, Tanzania
| | - Fredros O. Okumu
- Institute of Biodiversity Animal Health and Comparative Medicine, University of Glasgow, Glasgow, G12 8QQ UK
- Environmental Health & Ecological Sciences Department, Ifakara Health Institute, Off Mlabani Passage, PO Box 53, Ifakara, Tanzania
- School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
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64
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Moshi IR, Manderson L, Ngowo HS, Mlacha YP, Okumu FO, Mnyone LL. Outdoor malaria transmission risks and social life: a qualitative study in South-Eastern Tanzania. Malar J 2018; 17:397. [PMID: 30373574 PMCID: PMC6206631 DOI: 10.1186/s12936-018-2550-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Accepted: 10/25/2018] [Indexed: 12/03/2022] Open
Abstract
Background Behaviour changes in mosquitoes from indoor to outdoor biting result in continuing risk of malaria from outdoor activities, including routine household activities and occasional social and cultural practices and gatherings. This study aimed to identify the range of social and cultural gatherings conducted outdoors and their associated risks for mosquito bites. Methods A cross-sectional study was conducted in four villages in the Kilombero Valley from November 2015 to March 2016. Observations, focus group discussions, and key informant interviews were conducted. The recorded data were transcribed and translated from Swahili to English. Thematic content analysis was used to identify perspectives on the importance of various social and cultural gatherings that incidentally expose people to mosquito bites and malaria infection. Results Religious, cultural and social gatherings involving the wider community are conducted outdoors at night till dawn. Celebrations include life course events, religious and cultural ceremonies, such as Holy Communion, weddings, gatherings at Easter and Christmas, male circumcision, and rituals conducted to please the gods and to remember the dead. These celebrations, at which there is minimal use of interventions to prevent bites, contribute to individual satisfaction and social capital, helping to maintain a cohesive society. Bed net use while sleeping outdoors during mourning is unacceptable, and there is minimal use of other interventions, such as topical repellents. Long sleeve clothes are used for protection from mosquito bites but provide less protection. Conclusion Gatherings and celebrations expose people to mosquito bites. Approaches to prevent risks of mosquito bites and disease management need to take into account social, cultural and environmental factors. Area specific interventions may be expensive, yet may be the best approach to reduce risk of infection as endemic countries work towards elimination. Focusing on single interventions will not yield the best outcomes for malaria prevention as social contexts and vector behaviour vary.
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Affiliation(s)
- Irene R Moshi
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Kiko Avenue, Mikocheni, PO Box 78373, Dar es Salaam, United Republic of Tanzania. .,School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Parktown, Johannesburg, South Africa.
| | - Lenore Manderson
- School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Parktown, Johannesburg, South Africa
| | - Halfan S Ngowo
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Kiko Avenue, Mikocheni, PO Box 78373, Dar es Salaam, United Republic of Tanzania
| | - Yeromin P Mlacha
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Kiko Avenue, Mikocheni, PO Box 78373, Dar es Salaam, United Republic of Tanzania.,Swiss Tropical and Public Health Institute (Swiss TPH), Basel, Switzerland.,University of Basel, Basel, Switzerland.,Sokoine University of Agriculture, Pest Management Centre, P.O. Box 3110, Morogoro, Tanzania
| | - Fredros O Okumu
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Kiko Avenue, Mikocheni, PO Box 78373, Dar es Salaam, United Republic of Tanzania.,School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Parktown, Johannesburg, South Africa.,Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso.,Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Ladislaus L Mnyone
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Kiko Avenue, Mikocheni, PO Box 78373, Dar es Salaam, United Republic of Tanzania.,School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Parktown, Johannesburg, South Africa.,Sokoine University of Agriculture, Pest Management Centre, P.O. Box 3110, Morogoro, Tanzania
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Batista EPA, Ngowo H, Opiyo M, Shubis GK, Meza FC, Siria DJ, Eiras AE, Okumu FO. Field evaluation of the BG-Malaria trap for monitoring malaria vectors in rural Tanzanian villages. PLoS One 2018; 13:e0205358. [PMID: 30296287 PMCID: PMC6175526 DOI: 10.1371/journal.pone.0205358] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Accepted: 09/24/2018] [Indexed: 11/19/2022] Open
Abstract
BG-Malaria (BGM) trap is a simple adaptation of the widely-used BG-Sentinel trap (BGS). It is proven to be highly effective for trapping the Brazilian malaria vector, Anopheles darlingi, in field conditions, and the African vector, Anopheles arabiensis, under controlled semi-field environments, but has not been field-tested in Africa. Here, we validated the BGM for field sampling of malaria vectors in south-eastern Tanzania. Using a series of Latin-Square experiments conducted nightly (6pm-7am) in rural villages, we compared mosquito catches between BGM, BGS and human landing catches (HLC). We also compared BGMs baited with different attractants (Ifakara-blend, Mbita-blend, BG-Lure and CO2). Lastly, we tested BGMs baited with Ifakara-blend from three odour-dispensing methods (BG-Cartridge, BG-Sachet and Nylon strips). One-tenth of the field-collected female Anopheles gambiae s.l. and Anopheles funestus were dissected to assess parity. BGM captured more An. gambiae s.l. than BGS (p < 0.001), but HLC caught more than either trap (p < 0.001). However, BGM captured more An. funestus than HLC. Proportions of parous An. gambiae s.l. and An. funestus consistently exceeded 50%, with no significant difference between methods. While the dominant species caught by HLC was An. gambiae s.l. (56.0%), followed by Culex spp. (33.1%) and Mansonia spp. (6.0%), the BGM caught mostly Culex (81.6%), followed by An. gambiae s.l. (10.6%) and Mansonia (5.8%). The attractant-baited BGMs were all significantly superior to un-baited controls (p < 0.001), although no difference was found between the specific attractants. The BG-Sachet was the most efficient dispenser for capturing An. gambiae s.l. (14.5(2.75–42.50) mosquitoes/trap/night), followed by BG-Cartridge (7.5(1.75–26.25)). The BGM caught more mosquitoes than BGS in field-settings, but sampled similar species diversity and physiological states as BGS. The physiological states of malaria vectors caught in BGM and BGS were similar to those naturally attempting to bite humans (HLC). The BGM was most efficient when baited with Ifakara blend, dispensed from BG-Sachet. We conclude that though BGM traps have potential for field-sampling of host-seeking African malaria vectors with representative physiological states, both BGM and BGS predominantly caught more culicines than Anopheles, compared to HLC, which caught mostly An. gambiae s.l.
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Affiliation(s)
- Elis P. A. Batista
- Laboratório de Ecologia Química de Insetos Vetores, Departamento de Parasitologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Ifakara, Tanzania
- * E-mail:
| | - Halfan Ngowo
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Ifakara, Tanzania
| | - Mercy Opiyo
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Ifakara, Tanzania
| | - Gasper K. Shubis
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Ifakara, Tanzania
| | - Felician C. Meza
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Ifakara, Tanzania
| | - Doreen J. Siria
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Ifakara, Tanzania
| | - Alvaro E. Eiras
- Laboratório de Ecologia Química de Insetos Vetores, Departamento de Parasitologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Fredros O. Okumu
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Ifakara, Tanzania
- School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Parktown, Republic of South Africa
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
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Charlwood JD, Kessy E, Yohannes K, Protopopoff N, Rowland M, LeClair C. Studies on the resting behaviour and host choice of Anopheles gambiae and An. arabiensis from Muleba, Tanzania. MEDICAL AND VETERINARY ENTOMOLOGY 2018; 32:263-270. [PMID: 29479733 DOI: 10.1111/mve.12299] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Revised: 11/09/2017] [Accepted: 12/15/2017] [Indexed: 06/08/2023]
Abstract
The relative efficacy of a mechanical (Prokopack) collection method vs. manual aspiration in the collection of resting mosquitoes was evaluated in northern Tanzania before and after an intervention using indoor residual spraying and longlasting insecticide-treated nets. In smoke-free houses mosquitoes were collected from the roof and walls, but in smoky houses mosquitoes were found predominantly on the walls. Anopheles gambiae (Diptera: Culicidae) constituted 97.7% of the 312 An. gambiae complex specimens identified before but only 19.3% of the 183 identified after the intervention. A single sampling with the Prokopack collected a third of the available insects. Anopheles gambiae completed its gonotrophic development indoors, whereas Anopheles arabiensis did so outdoors. In both species gonotrophic development took 2 days. Most unfed resting An. arabiensis collected outdoors were virgins, whereas the majority of engorged insects were parous (with well-contracted sacs). Daily survival was estimated to be 80.0%. Only 9.4% of the engorged An. arabiensis collected outdoors and 47.1% of those collected indoors had fed on humans. Using the Prokopack sampler is more efficient than manual methods for the collection of resting mosquitoes. Malaria transmission may have been affected by a change in vector composition resulting from a change in feeding, rather than reduced survival. Monitoring the proportions of members of the An. gambiae complex may provide signals of an impending breakdown in control.
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Affiliation(s)
- J D Charlwood
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, U.K
| | - E Kessy
- Kilimanjaro Christian Medical University College, Moshi, Tanzania
| | - K Yohannes
- Pan African Malaria Vector Research Consortium, Muleba, Tanzania
| | - N Protopopoff
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, U.K
| | - M Rowland
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, U.K
| | - C LeClair
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, U.K
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Khatib RA, Chaki PP, Wang DQ, Mlacha YP, Mihayo MG, Gavana T, Xiao N, Zhou XN, Abdullah S. Epidemiological characterization of malaria in rural southern Tanzania following China-Tanzania pilot joint malaria control baseline survey. Malar J 2018; 17:292. [PMID: 30103755 PMCID: PMC6088395 DOI: 10.1186/s12936-018-2446-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Accepted: 08/04/2018] [Indexed: 11/23/2022] Open
Abstract
Background Malaria is an important public health problem in Tanzania. The latest national malaria data suggests rebound of the disease in the country. Anopheles arabiensis, a mosquito species renowned for its resilience against existing malaria vector control measures has now outnumbered the endophagic and anthrophilic Anopheles gambiae sensu stricto as the dominant vector. Vector control measures, prophylaxis and case management with artemisinin-based combination therapy (ACT) are the main control interventions. This paper presents and discusses the main findings from a baseline household survey that was conducted to determine malaria parasite prevalence and associated risk exposures prior to piloting the T3-initiative of World Health Organization integrated with Chinese malaria control experience aimed at additional reduction of malaria in the area. Methods The study was conducted from 4 sub-district divisions in Rufiji District, southern Tanzania: Ikwiriri, Kibiti, Bungu, and Chumbi. Malaria transmission is endemic in the area. It involved 2000 households that were randomly selected from a list of all households that had been registered from the area. Residents in sampled households were interviewed on a range of questions that included use of long-lasting insecticidal nets (LLINs) the night prior to the interview and indicators of socio-economic status. Blood drops were also collected on blood slides that were examined for malaria parasites using microscopes. Results The study observed an average malaria parasite prevalence of 13% across the selected site. Its distribution was 5.6, 12.8, 16.7, and 18% from Ikwiriri, Kibiti, Bungu, and Chumbi wards, respectively. The corresponding LLIN use discovered were 57.5% over the district. The highest usage was observed from Ikwiriri at 69.6% and the lowest from Bungu at 46.3%. A statistically significant variation in parasitaemia between socio-economic quintiles was observed from the study. Males were more parasitaemic than females (p value = 0.000). Discussion and conclusion The findings have been discussed in the light of results from Tanzania Demographic and Health Survey-Malaria Indicator Survey, 2015–2016 and other related studies, together with goals and targets set for malaria control. The paper also discusses the observed parasitaemia in relation to reported LLIN use and its distribution by some important factors as they were explored from the study. It has been concluded that malaria burden is now concentrated on the fringes of the settlements where the poorest section of the population is concentrated and LLIN usage is lower than the national average and targets set by national and global malaria control initiatives.
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Affiliation(s)
- Rashid A Khatib
- Ifakara Health Institute, Kiko Avenue, Mikocheni, P.O. Box 78373, Dar es Salaam, United Republic of Tanzania.
| | - Prosper P Chaki
- Ifakara Health Institute, Kiko Avenue, Mikocheni, P.O. Box 78373, Dar es Salaam, United Republic of Tanzania
| | - Duo-Quan Wang
- National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, 207 Rui Jin Er Road, Shanghai, 200025, People's Republic of China
| | - Yeromin P Mlacha
- Ifakara Health Institute, Kiko Avenue, Mikocheni, P.O. Box 78373, Dar es Salaam, United Republic of Tanzania.,Swiss Tropical and Public Health Institute (Swiss TPH), Socinstrasse 57, P.O. Box, 4002, Basel, Switzerland.,University of Basel, Petersplatz 1, 4003, Basel, Switzerland
| | - Michael G Mihayo
- Ifakara Health Institute, Kiko Avenue, Mikocheni, P.O. Box 78373, Dar es Salaam, United Republic of Tanzania
| | - Tegemeo Gavana
- Ifakara Health Institute, Kiko Avenue, Mikocheni, P.O. Box 78373, Dar es Salaam, United Republic of Tanzania
| | - Ning Xiao
- National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, 207 Rui Jin Er Road, Shanghai, 200025, People's Republic of China
| | - Xiao-Nong Zhou
- National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, 207 Rui Jin Er Road, Shanghai, 200025, People's Republic of China
| | - Salim Abdullah
- Ifakara Health Institute, Kiko Avenue, Mikocheni, P.O. Box 78373, Dar es Salaam, United Republic of Tanzania
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Masalu JP, Okumu FO, Mmbando AS, Sikulu-Lord MT, Ogoma SB. Potential benefits of combining transfluthrin-treated sisal products and long-lasting insecticidal nets for controlling indoor-biting malaria vectors. Parasit Vectors 2018; 11:231. [PMID: 29631633 PMCID: PMC5891933 DOI: 10.1186/s13071-018-2811-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Accepted: 03/25/2018] [Indexed: 11/25/2022] Open
Abstract
Background Transfluthrin vapour prevents mosquito bites by disrupting their host-seeking behaviors. We measured the additional benefits of combining transfluthrin-treated sisal decorations and long-lasting insecticidal nets (LLINs) with an aim of extending protection against early evening, indoor-biting malaria vectors when LLINs are ineffective. Methods We investigated the indoor protective efficacy of locally made sisal decorative baskets (0.28 m2) treated with 2.5 ml and 5.0 ml transfluthrin, in terms of mosquito density, exposure to bites and 24 h mortality. Experiments were conducted in experimental huts, located in Lupiro village, Ulanga District, south-eastern Tanzania. Human landing catches (HLC) were used to measure exposure to bites between 19:00–23:00 h. Each morning, at 06:00 h, mosquitoes were collected inside huts and in exit traps and monitored for 24 h mortality. Results Sisal decorative baskets (0.28 m2) treated with 2.5 ml and 5.0 ml transfluthrin deterred three-quarters of Anopheles arabiensis mosquitoes from entering huts (relative rate, RR = 0.26, 95% confidence interval, CI: 0.20–0.34, P < 0.001 and RR= 0.29, 95% CI: 0.22–0.37, P < 0.001, respectively). Both treatments induced a 10-fold increase in 24 h mortality of An. arabiensis mosquitoes (odds ratio, OR = 12.26, 95% CI: 7.70–19.51, P < 0.001 and OR = 18.42, 95% CI: 11.36–29.90, P < 0.001, respectively). Conclusions Sisal decorative items treated with spatial repellents provide additional household and personal protection against indoor biting malaria and nuisance mosquitoes in the early evening, when conventional indoor vector control tools, such as LLINs, are not in use. We recommend future studies to investigate the epidemiological relevance of combining LLINs and transfluthrin decorated baskets in terms of their effect on reduction in malaria prevalence.
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Affiliation(s)
- John P Masalu
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Off Mlabani Passage, Ifakara, Morogoro, United Republic of Tanzania.
| | - Fredros O Okumu
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Off Mlabani Passage, Ifakara, Morogoro, United Republic of Tanzania.,School of Public Health, University of the Witwatersrand, Johannesburg, South Africa.,Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK
| | - Arnold S Mmbando
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Off Mlabani Passage, Ifakara, Morogoro, United Republic of Tanzania
| | - Maggy T Sikulu-Lord
- Queensland Alliance of Agriculture and Food Innovation, The University of Queensland, Brisbane, Australia
| | - Sheila B Ogoma
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Off Mlabani Passage, Ifakara, Morogoro, United Republic of Tanzania.,US National Research Council, National Academies of Sciences, Engineering, and Medicine, Washington, D.C., USA
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Hemming-Schroeder E, Strahl S, Yang E, Nguyen A, Lo E, Zhong D, Atieli H, Githeko A, Yan G. Emerging Pyrethroid Resistance among Anopheles arabiensis in Kenya. Am J Trop Med Hyg 2018; 98:704-709. [PMID: 29363447 PMCID: PMC5930888 DOI: 10.4269/ajtmh.17-0445] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Vector control programs, particularly in the form of insecticide-treated bed nets (ITNs), are essential for achieving malaria elimination goals. Recent reports of increasing knockdown resistance (kdr) mutation frequencies for Anopheles arabiensis in Western Kenya heightens the concern on the future effectiveness of ITNs in Kenya. We examined resistance in An. arabiensis populations across Kenya through kdr mutations and World Health Organization–recommended bioassays. We detected two kdr alleles, L1014F and L1014S. Kdr mutations were found in five of the 11 study sites, with mutation frequencies ranging from 3% to 63%. In two Western Kenya populations, the kdr L1014F allele frequency was as high as 10%. The L1014S frequency was highest at Chulaimbo at 55%. Notably, the kdr L1014F mutation was found to be associated with pyrethroid resistance at Port Victoria, but kdr mutations were not significantly associated with resistance at Chulaimbo, which had the highest kdr mutation frequency among all sites. This study demonstrated the emerging pyrethroid resistance in An. arabiensis and that pyrethroid resistance may be related to kdr mutations. Resistance monitoring and management are urgently needed for this species in Kenya where resistance is emerging and its abundance is becoming predominant. Kdr mutations may serve as a biomarker for pyrethroid resistance in An. arabiensis.
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Affiliation(s)
| | - Stephanie Strahl
- Program in Public Health, University of California, Irvine, California
| | - Eugene Yang
- Program in Public Health, University of California, Irvine, California
| | - Amanda Nguyen
- Program in Public Health, University of California, Irvine, California
| | - Eugenia Lo
- Program in Public Health, University of California, Irvine, California
| | - Daibin Zhong
- Program in Public Health, University of California, Irvine, California
| | - Harrysone Atieli
- Centre for Vector Biology and Control Research, Kenya Medical Research Institute, Kisumu, Kenya
| | - Andrew Githeko
- Centre for Vector Biology and Control Research, Kenya Medical Research Institute, Kisumu, Kenya
| | - Guiyun Yan
- Program in Public Health, University of California, Irvine, California
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Kiuru CW, Oyieke FA, Mukabana WR, Mwangangi J, Kamau L, Muhia-Matoke D. Status of insecticide resistance in malaria vectors in Kwale County, Coastal Kenya. Malar J 2018; 17:3. [PMID: 29304805 PMCID: PMC5755433 DOI: 10.1186/s12936-017-2156-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Accepted: 12/23/2017] [Indexed: 11/21/2022] Open
Abstract
Background The strategy for malaria vector control in the context of reducing malaria morbidity and mortality has been the scale-up of long-lasting insecticidal nets to universal coverage and indoor residual spraying. This has led to significant decline in malaria transmission. However, these vector control strategies rely on insecticides which are threatened by insecticide resistance. In this study the status of pyrethroid resistance in malaria vectors and it’s implication in malaria transmission at the Kenyan Coast was investigated. Results Using World Health Organization diagnostic bioassay, levels of phenotypic resistance to permethrin and deltamethrin was determined. Anopheles arabiensis showed high resistance to pyrethroids while Anopheles gambiae sensu stricto (s.s.) and Anopheles funestus showed low resistance and susceptibility, respectively. Anopheles gambiae sensu lato (s.l.) mosquitoes were further genotyped for L1014S and L1014F kdr mutation by real time PCR. An allele frequency of 1.33% for L1014S with no L1014F was detected. To evaluate the implication of pyrethroid resistance on malaria transmission, Plasmodium falciparum infection rates in field collected adult mosquitoes was determined using enzyme linked immunosorbent assay and further, the behaviour of the vectors was assessed by comparing indoor and outdoor proportions of mosquitoes collected. Sporozoite infection rate was observed at 4.94 and 2.60% in An. funestus s.l. and An. gambiae s.l., respectively. A higher density of malaria vectors was collected outdoor and this also corresponded with high Plasmodium infection rates outdoor. Conclusions This study showed phenotypic resistance to pyrethroids and low frequency of L1014S kdr mutation in An. gambiae s.l. The occurrence of phenotypic resistance with low levels of kdr frequencies highlights the need to investigate other mechanisms of resistance. Despite being susceptible to pyrethroids An. funestus s.l. could be driving malaria infections in the area.
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Affiliation(s)
- Caroline W Kiuru
- School of Biological Sciences, University of Nairobi, P.O. Box 30197, Nairobi, 00100, Kenya.,Department of Biological Sciences, Pwani University, Kilifi, Kenya
| | - Florence Awino Oyieke
- School of Biological Sciences, University of Nairobi, P.O. Box 30197, Nairobi, 00100, Kenya
| | - Wolfgang Richard Mukabana
- School of Biological Sciences, University of Nairobi, P.O. Box 30197, Nairobi, 00100, Kenya.,Man & Well-Being Research Office, Science for Health, P.O. Box 44970, Nairobi, 00100, Kenya
| | - Joseph Mwangangi
- Department of Biological Sciences, Pwani University, Kilifi, Kenya.,KEMRI-Centre for Geographic Medicine Research, Kilifi, Kenya
| | - Luna Kamau
- KEMRI-Centre for Biotechnology Research and Development, Nairobi, Kenya
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A diagnostic and epidemiologic investigation of acute febrile illness (AFI) in Kilombero, Tanzania. PLoS One 2017; 12:e0189712. [PMID: 29287070 PMCID: PMC5747442 DOI: 10.1371/journal.pone.0189712] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Accepted: 11/30/2017] [Indexed: 12/20/2022] Open
Abstract
Introduction In low-resource settings, empiric case management of febrile illness is routine as a result of limited access to laboratory diagnostics. The use of comprehensive fever syndromic surveillance, with enhanced clinical microbiology, advanced diagnostics and more robust epidemiologic investigation, could enable healthcare providers to offer a differential diagnosis of fever syndrome and more appropriate care and treatment. Methods We conducted a year-long exploratory study of fever syndrome among patients ≥ 1 year if age, presenting to clinical settings with an axillary temperature of ≥37.5°C and symptomatic onset of ≤5 days. Blood and naso-pharyngeal/oral-pharyngeal (NP/OP) specimens were collected and analyzed, respectively, using AFI and respiratory TaqMan Array Cards (TAC) for multi-pathogen detection of 57 potential causative agents. Furthermore, we examined numerous epidemiologic correlates of febrile illness, and conducted demographic, clinical, and behavioral domain-specific multivariate regression to statistically establish associations with agent detection. Results From 15 September 2014–13 September 2015, 1007 febrile patients were enrolled, and 997 contributed an epidemiologic survey, including: 14% (n = 139) 1<5yrs, 19% (n = 186) 5-14yrs, and 67% (n = 672) ≥15yrs. AFI TAC and respiratory TAC were performed on 842 whole blood specimens and 385 NP/OP specimens, respectively. Of the 57 agents surveyed, Plasmodium was the most common agent detected. AFI TAC detected nucleic acid for one or more of seven microbial agents in 49% of AFI blood samples, including: Plasmodium (47%), Leptospira (3%), Bartonella (1%), Salmonella enterica (1%), Coxiella burnetii (1%), Rickettsia (1%), and West Nile virus (1%). Respiratory TAC detected nucleic acid for 24 different microbial agents, including 12 viruses and 12 bacteria. The most common agents detected among our surveyed population were: Haemophilus influenzae (67%), Streptococcus pneumoniae (55%), Moraxella catarrhalis (39%), Staphylococcus aureus (37%), Pseudomonas aeruginosa (36%), Human Rhinovirus (25%), influenza A (24%), Klebsiella pneumoniae (14%), Enterovirus (15%) and group A Streptococcus (12%). Our epidemiologic investigation demonstrated both age and symptomatic presentation to be associated with a number of detected agents, including, but not limited to, influenza A and Plasmodium. Linear regression of fully-adjusted mean cycle threshold (Ct) values for Plasmodium also identified statistically significant lower mean Ct values for older children (20.8), patients presenting with severe fever (21.1) and headache (21.5), as well as patients admitted for in-patient care and treatment (22.4). Conclusions This study is the first to employ two syndromic TaqMan Array Cards for the simultaneous survey of 57 different organisms to better characterize the type and prevalence of detected agents among febrile patients. Additionally, we provide an analysis of the association between adjusted mean Ct values for Plasmodium and key clinical and demographic variables, which may further inform clinical decision-making based upon intensity of infection, as observed across endemic settings of sub-Saharan Africa.
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Why some sites are responding better to anti-malarial interventions? A case study from western Kenya. Malar J 2017; 16:498. [PMID: 29284476 PMCID: PMC5747174 DOI: 10.1186/s12936-017-2145-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Accepted: 12/18/2017] [Indexed: 01/07/2023] Open
Abstract
Background In sub-Saharan Africa, malaria interventions over the last decades have been successful in reducing both mortality and morbidity. In western Kenya however some areas experience contrasting outcomes of the ongoing interventions while the causes for this observation remains not yet clearly known. Methods The WHO insecticide (deltamethrin) susceptibility test of the common malaria vectors was studied. Multiple surveys on household use and hospital prescriptions of antimalarial drugs from 2003 to 2015 were done. Along with this, cross sectional surveys on their availability in the local drug dispensing outlets were also done in 2015. Monthly precipitations and air temperature data was collected along with systematic review on abundance and composition of common malaria vectors in the study area before and during interventions. The above factors were used to explain the possible causes of contrasting outcome of malaria interventions between the three study sites. Results Areas with malaria resurgence or sustained high transmission (Kombewa and Marani) showed higher composition of Anopheles funestus sensu lato (s.l.) than the previously abundant Anopheles gambiae sensu stricto (s.s.) and the later had higher composition to an area with a sustained infection decline (Iguhu). Anopheles gambiae s.l. from Kombewa showed highest resistance (50% mortality) upon exposure to WHO deltamethrin discriminating dosage of 0.75% while those from Marani and Iguhu had reduced resistance status (both had a mean mortality of 91%). Sampled An. funestus s.l. from Marani were also highly resistant to deltamethrin as 57% of the exposed vectors survived. An increasing of mean air temperature by 2 °C was noted for Marani and Iguhu from 2013 to 2015 and was accompanied by an increased rainfall at Marani. Community drug use and availability in selling outlets along with prescription in hospitals were not linked to the struggling control of the disease. Conclusions The malaria vector species composition shift, insecticide resistance and climatic warming were the likely cause of the contrasting outcome of malaria intervention in western Kenya. Surveillance of malaria parasite and vector dynamics along with insecticide resistance and vector biting behaviour monitoring are highly recommended in these areas.
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Hercik C, Cosmas L, Mogeni OD, Wamola N, Kohi W, Houpt E, Liu J, Ochieng C, Onyango C, Fields B, Mfinanga S, Montgomery JM. A Combined Syndromic Approach to Examine Viral, Bacterial, and Parasitic Agents among Febrile Patients: A Pilot Study in Kilombero, Tanzania. Am J Trop Med Hyg 2017; 98:625-632. [PMID: 29280432 PMCID: PMC5929188 DOI: 10.4269/ajtmh.17-0421] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The use of fever syndromic surveillance in sub-Saharan Africa is an effective approach to determine the prevalence of both malarial and nonmalarial infectious agents. We collected both blood and naso/oro-pharyngeal (NP/OP) swabs from consecutive consenting patients ≥ 1 year of age, with an axillary temperature ≥ 37.5°C, and symptom onset of ≤ 5 days. Specimens were analyzed using both acute febrile illness (AFI) and respiratory TaqMan array cards (Resp TAC) for multiagent detection of 56 different bloodstream and respiratory agents. In addition, we collected epidemiologic data to further characterize our patient population. We enrolled 205 febrile patients, including 70 children (1 < 15 years of age; 34%) and 135 adults (≥ 15 years of age; 66%). AFI TAC and Resp TAC were performed on 191 whole blood specimens and 115 NP/OP specimens, respectively. We detected nucleic acid for Plasmodium (57%), Leptospira (2%), and dengue virus (1%) among blood specimens. In addition, we detected 17 different respiratory agents, most notably, Haemophilus influenzae (64%), Streptococcus pneumonia (56%), Moraxella catarrhalis (39%), and respiratory syncytial virus (11%) among NP/OP specimens. Overall median cycle threshold was measured at 26.5. This study provides a proof-of-concept for the use of a multiagent diagnostic approach for exploratory research on febrile illness and underscores the utility of quantitative molecular diagnostics in complex epidemiologic settings of sub-Saharan Africa.
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Affiliation(s)
| | - Leonard Cosmas
- Global Disease Detection Branch, Division of Global Health Protection, Center for Global Health, US Centers for Disease Control and Prevention (CDC), Nairobi, Kenya
| | - Ondari D Mogeni
- Kenya Medical Research Institute-Centre for Global Health Research (KEMRI-CGHR), Nairobi, Kenya
| | - Newton Wamola
- Kenya Medical Research Institute-Centre for Global Health Research (KEMRI-CGHR), Nairobi, Kenya
| | - Wanze Kohi
- National Institute of Medical Research (NIMR), Muhimbili Research Centre, Salaam, Tanzania
| | - Eric Houpt
- Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, Virginia
| | - Jie Liu
- Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, Virginia
| | - Caroline Ochieng
- Kenya Medical Research Institute-Centre for Global Health Research (KEMRI-CGHR), Nairobi, Kenya
| | - Clayton Onyango
- Global Disease Detection Branch, Division of Global Health Protection, Center for Global Health, US Centers for Disease Control and Prevention (CDC), Nairobi, Kenya
| | - Barry Fields
- Global Disease Detection Branch, Division of Global Health Protection, Center for Global Health, US Centers for Disease Control and Prevention (CDC), Nairobi, Kenya
| | - Sayoki Mfinanga
- National Institute of Medical Research (NIMR), Muhimbili Research Centre, Salaam, Tanzania
| | - Joel M Montgomery
- Global Disease Detection Branch, Division of Global Health Protection, Center for Global Health, US Centers for Disease Control and Prevention (CDC), Nairobi, Kenya
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Mmbando AS, Ngowo HS, Kilalangongono M, Abbas S, Matowo NS, Moore SJ, Okumu FO. Small-scale field evaluation of push-pull system against early- and outdoor-biting malaria mosquitoes in an area of high pyrethroid resistance in Tanzania. Wellcome Open Res 2017; 2:112. [PMID: 29568808 PMCID: PMC5840620 DOI: 10.12688/wellcomeopenres.13006.1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/20/2017] [Indexed: 12/22/2022] Open
Abstract
Background: Despite high coverage of indoor interventions like insecticide-treated nets, mosquito-borne infections persist, partly because of outdoor-biting, early-biting and insecticide-resistant vectors. Push-pull systems, where mosquitoes are repelled from humans and attracted to nearby lethal targets, may constitute effective complementary interventions. Methods: A partially randomized cross-over design was used to test efficacy of push-pull in four experimental huts and four local houses, in an area with high pyrethroid resistance in Tanzania. The push-pull system consisted of 1.1% or 2.2% w/v transfluthrin repellent dispensers and an outdoor lure-and-kill device (odour-baited mosquito landing box). Matching controls were set up without push-pull. Adult male volunteers collected mosquitoes attempting to bite them outdoors, but collections were also done indoors using exit traps in experimental huts and by volunteers in the local houses. The collections were done hourly (1830hrs-0730hrs) and mosquito catches compared between push-pull and controls.
An. gambiae s.l. and
An. funestus s.l. were assessed by PCR to identify sibling species, and ELISA to detect
Plasmodium falciparum and blood meal sources. Results: Push-pull in experimental huts reduced outdoor-biting for
An. arabiensis and
Mansonia species by 30% and 41.5% respectively. However, the reductions were marginal and insignificant for
An. funestus (12.2%; p>0.05) and
Culex (5%; p>0.05). Highest protection against all species occurred before 2200hrs. There was no significant difference in number of mosquitoes inside exit traps in huts with or without push-pull. In local households, push-pull significantly reduced indoor and outdoor-biting of
An. arabiensis by 48% and 25% respectively, but had no effect on other species. Conclusion: This push-pull system offered modest protection against outdoor-biting
An. arabiensis, without increasing indoor mosquito densities. Additional experimentation is required to assess how transfluthrin-based products affect mosquito blood-feeding and mortality in push-pull contexts. This approach, if optimised, could potentially complement existing malaria interventions even in areas with high pyrethroid resistance.
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Affiliation(s)
- Arnold S Mmbando
- Environmental Health and Ecological Sciences, Ifakara Health Institute, Ifakara, Tanzania.,Swiss Tropical and Public Health Institute, Basel, Switzerland.,Univeristy of Basel, Basel, Switzerland
| | - Halfan S Ngowo
- Environmental Health and Ecological Sciences, Ifakara Health Institute, Ifakara, Tanzania
| | - Masoud Kilalangongono
- Environmental Health and Ecological Sciences, Ifakara Health Institute, Ifakara, Tanzania
| | - Said Abbas
- Environmental Health and Ecological Sciences, Ifakara Health Institute, Ifakara, Tanzania
| | - Nancy S Matowo
- Environmental Health and Ecological Sciences, Ifakara Health Institute, Ifakara, Tanzania.,Swiss Tropical and Public Health Institute, Basel, Switzerland
| | - Sarah J Moore
- Environmental Health and Ecological Sciences, Ifakara Health Institute, Ifakara, Tanzania.,Swiss Tropical and Public Health Institute, Basel, Switzerland.,Univeristy of Basel, Basel, Switzerland
| | - Fredros O Okumu
- Environmental Health and Ecological Sciences, Ifakara Health Institute, Ifakara, Tanzania.,School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.,Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK
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75
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Choi L, Wilson A. Larviciding to control malaria. THE COCHRANE DATABASE OF SYSTEMATIC REVIEWS 2017. [DOI: 10.1002/14651858.cd012736] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Leslie Choi
- Liverpool School of Tropical Medicine; Department of Clinical Sciences; Pembroke Place Liverpool UK L3 5QA
| | - Anne Wilson
- Durham University; Department of Biosciences; Stockton Road Durham UK
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76
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Sperling S, Cordel M, Gordon S, Knols BG, Rose A. Eave tubes for malaria control in Africa: Videographic observations of mosquito behaviour in Tanzania with a simple and rugged video surveillance system. MALARIAWORLD JOURNAL 2017; 8:9. [PMID: 34532232 PMCID: PMC8415065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Eave tubes are novel mosquito control devices that help to protect households against malaria vectors and other mosquitoes. They are installed in the upper walls of human habitations after the eaves have been closed. Mosquitoes trying to enter through these tubes are intercepted by electrostatic netting that can be treated with a variety of insecticides. Using video, mosquito behaviour and duration of contact with netting in eave tubes was recorded and analysed to assess contamination with insecticides under semi-field and field conditions. MATERIALS AND METHODS Off-the-shelf action cameras were used to observe behaviour of mosquitoes in eave tubes near Ifakara, Tanzania. In an experimental hut in a screen house, we observed Anopheles arabiensis females on electrostatic eave tube netting treated with bendiocarb powder or with Beauveria bassiana spores, both in comparison to untreated netting. In village houses that had been equipped with eave tubes we observed the behaviour of wild mosquitoes towards electrostatic netting treated with bendiocarb. Results were evaluated using a short-contact assay (5 second exposure). RESULTS In the semi-field setup, the median contact time of An. arabiensis on bendiocarb-powdered eave tube nets was 276.4 sec (n=56), compared to 26.3 sec on the control (n=59). Of all the mosquitoes observed on the treated net, 94.6% had contact times of more than 5 seconds on the bendiocarb-powdered netting. The median time on nets powdered with B. bassiana spores was 34.4 sec (n=26), compared 37.1 sec in the untreated control (n=22). 88.5% of the mosquitoes spent more than 5 seconds on the treated nets. In the field we recorded 106 individual mosquitoes of unknown species inside tubes. They spent a median time of 70.9 sec on the bendiocarb-treated netting, with 90.6% remaining there for more than 5 seconds. CONCLUSIONS We have found no indication that the behaviour of mosquitoes on electrostatic eave tube netting, treated either with bendiocarb powder or with B. bassiana spores, interferes with successful transfer of lethal doses of these insecticidal actives. The videographic set-up used in this study is simple, sturdy and reliable enough to observe and analyse mosquito behaviour under field conditions.
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Affiliation(s)
| | - Michael Cordel
- Biogents AG, Weißenburgstraße 22, 93055 Regensburg, Germany
| | - Scott Gordon
- Biogents AG, Weißenburgstraße 22, 93055 Regensburg, Germany
| | - Bart G.J. Knols
- Radboud University Nijmegen, Department of Environmental Science, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands
| | - Andreas Rose
- Biogents AG, Weißenburgstraße 22, 93055 Regensburg, Germany,* corresponding author:
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77
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Emidi B, Kisinza WN, Mmbando BP, Malima R, Mosha FW. Effect of physicochemical parameters on Anopheles and Culex mosquito larvae abundance in different breeding sites in a rural setting of Muheza, Tanzania. Parasit Vectors 2017. [PMID: 28645303 PMCID: PMC5482952 DOI: 10.1186/s13071-017-2238-x] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Affiliation(s)
- Basiliana Emidi
- Kilimanjaro Christian Medical University College, P.O. Box 2240, Moshi, Tanzania. .,National Institute for Medical Research, Headquarters, P.O. Box 9653, Dar es Salaam, Tanzania.
| | - William N Kisinza
- National Institute for Medical Research, Amani Centre, P.O. Box 81, Muheza, Tanzania
| | - Bruno P Mmbando
- National Institute for Medical Research, Tanga Centre, P.O. Box 5004, Tanga, Tanzania
| | - Robert Malima
- National Institute for Medical Research, Amani Centre, P.O. Box 81, Muheza, Tanzania
| | - Franklin W Mosha
- Kilimanjaro Christian Medical University College, P.O. Box 2240, Moshi, Tanzania
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78
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Killeen GF, Masalu JP, Chinula D, Fotakis EA, Kavishe DR, Malone D, Okumu F. Control of Malaria Vector Mosquitoes by Insecticide-Treated Combinations of Window Screens and Eave Baffles. Emerg Infect Dis 2017; 23:782-789. [PMID: 28418299 PMCID: PMC5403053 DOI: 10.3201/eid2305.160662] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
We assessed window screens and eave baffles (WSEBs), which enable mosquitoes to enter but not exit houses, as an alternative to indoor residual spraying (IRS) for malaria vector control. WSEBs treated with water, the pyrethroid lambda-cyhalothrin, or the organophosphate pirimiphos-methyl, with and without a binding agent for increasing insecticide persistence on netting, were compared with IRS in experimental huts. Compared with IRS containing the same insecticide, WSEBs killed similar proportions of Anopheles funestus mosquitoes that were resistant to pyrethroids, carbamates and organochlorines and greater proportions of pyrethroid-resistant, early exiting An. arabiensis mosquitoes. WSEBs with pirimiphos-methyl killed greater proportions of both vectors than lambda-cyhalothrin or lambda-cyhalothrin plus pirimiphos-methyl and were equally efficacious when combined with binding agent. WSEBs required far less insecticide than IRS, and binding agents might enhance durability. WSEBs might enable affordable deployment of insecticide combinations to mitigate against physiologic insecticide resistance and improve control of behaviorally resistant, early exiting vectors.
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79
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Genome-Wide Transcription and Functional Analyses Reveal Heterogeneous Molecular Mechanisms Driving Pyrethroids Resistance in the Major Malaria Vector Anopheles funestus Across Africa. G3-GENES GENOMES GENETICS 2017; 7:1819-1832. [PMID: 28428243 PMCID: PMC5473761 DOI: 10.1534/g3.117.040147] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Pyrethroid resistance in malaria vector, An. funestus is increasingly reported across Africa, threatening the sustainability of pyrethroid-based control interventions, including long lasting insecticidal nets (LLINs). Managing this problem requires understanding of the molecular basis of the resistance from different regions of the continent, to establish whether it is being driven by a single or independent selective events. Here, using a genome-wide transcription profiling of pyrethroid resistant populations from southern (Malawi), East (Uganda), and West Africa (Benin), we investigated the molecular basis of resistance, revealing strong differences between the different African regions. The duplicated cytochrome P450 genes (CYP6P9a and CYP6P9b) which were highly overexpressed in southern Africa are not the most upregulated in other regions, where other genes are more overexpressed, including GSTe2 in West (Benin) and CYP9K1 in East (Uganda). The lack of directional selection on both CYP6P9a and CYP6P9b in Uganda in contrast to southern Africa further supports the limited role of these genes outside southern Africa. However, other genes such as the P450 CYP9J11 are commonly overexpressed in all countries across Africa. Here, CYP9J11 is functionally characterized and shown to confer resistance to pyrethroids and moderate cross-resistance to carbamates (bendiocarb). The consistent overexpression of GSTe2 in Benin is coupled with a role of allelic variation at this gene as GAL4-UAS transgenic expression in Drosophila flies showed that the resistant 119F allele is highly efficient in conferring both DDT and permethrin resistance than the L119. The heterogeneity in the molecular basis of resistance and cross-resistance to insecticides in An. funestus populations throughout sub-Saharan African should be taken into account in designing resistance management strategies.
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80
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Kaindoa EW, Matowo NS, Ngowo HS, Mkandawile G, Mmbando A, Finda M, Okumu FO. Interventions that effectively target Anopheles funestus mosquitoes could significantly improve control of persistent malaria transmission in south-eastern Tanzania. PLoS One 2017; 12:e0177807. [PMID: 28542335 PMCID: PMC5436825 DOI: 10.1371/journal.pone.0177807] [Citation(s) in RCA: 106] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Accepted: 05/03/2017] [Indexed: 11/26/2022] Open
Abstract
Malaria is transmitted by many Anopheles species whose proportionate contributions vary across settings. We re-assessed the roles of Anopheles arabiensis and Anopheles funestus, and examined potential benefits of species-specific interventions in an area in south-eastern Tanzania, where malaria transmission persists, four years after mass distribution of long-lasting insecticide-treated nets (LLINs). Monthly mosquito sampling was done in randomly selected households in three villages using CDC light traps and back-pack aspirators, between January-2015 and January-2016, four years after the last mass distribution of LLINs in 2011. Multiplex polymerase chain reaction (PCR) was used to identify members of An. funestus and Anopheles gambiae complexes. Enzyme-linked immunosorbent assay (ELISA) was used to detect Plasmodium sporozoites in mosquito salivary glands, and to identify sources of mosquito blood meals. WHO susceptibility assays were done on wild caught female An. funestus s.l, and physiological ages approximated by examining mosquito ovaries for parity. A total of 20,135 An. arabiensis and 4,759 An. funestus were collected. The An. funestus group consisted of 76.6% An. funestus s.s, 2.9% An. rivulorum, 7.1% An. leesoni, and 13.4% unamplified samples. Of all mosquitoes positive for Plasmodium, 82.6% were An. funestus s.s, 14.0% were An. arabiensis and 3.4% were An. rivulorum. An. funestus and An. arabiensis contributed 86.21% and 13.79% respectively, of annual entomological inoculation rate (EIR). An. arabiensis fed on humans (73.4%), cattle (22.0%), dogs (3.1%) and chicken (1.5%), but An. funestus fed exclusively on humans. The An. funestus populations were 100% susceptible to organophosphates, pirimiphos methyl and malathion, but resistant to permethrin (10.5% mortality), deltamethrin (18.7%), lambda-cyhalothrin (18.7%) and DDT (26.2%), and had reduced susceptibility to bendiocarb (95%) and propoxur (90.1%). Parity rate was higher in An. funestus (65.8%) than An. arabiensis (44.1%). Though An. arabiensis is still the most abundant vector species here, the remaining malaria transmission is predominantly mediated by An. funestus, possibly due to high insecticide resistance and high survival probabilities. Interventions that effectively target An. funestus mosquitoes could therefore significantly improve control of persistent malaria transmission in south–eastern Tanzania.
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Affiliation(s)
- Emmanuel W. Kaindoa
- Ifakara Health Institute, Environmental Health and Ecological Sciences Thematic Group, Morogoro, Tanzania
- University of the Witwatersrand, School of Public Health, Faculty of Health Science, Johannesburg, South Africa
- * E-mail:
| | - Nancy S. Matowo
- Ifakara Health Institute, Environmental Health and Ecological Sciences Thematic Group, Morogoro, Tanzania
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Halfan S. Ngowo
- Ifakara Health Institute, Environmental Health and Ecological Sciences Thematic Group, Morogoro, Tanzania
- Institute of Biodiversity, Animal Health and Comparative Medicine, G12 8QQ, University of Glasgow, Glasgow, United Kingdom
| | - Gustav Mkandawile
- Ifakara Health Institute, Environmental Health and Ecological Sciences Thematic Group, Morogoro, Tanzania
| | - Arnold Mmbando
- Ifakara Health Institute, Environmental Health and Ecological Sciences Thematic Group, Morogoro, Tanzania
- Swiss Tropical and Public Health Institute, University of Basel, Basel, Switzerland
| | - Marcelina Finda
- Ifakara Health Institute, Environmental Health and Ecological Sciences Thematic Group, Morogoro, Tanzania
| | - Fredros O. Okumu
- Ifakara Health Institute, Environmental Health and Ecological Sciences Thematic Group, Morogoro, Tanzania
- University of the Witwatersrand, School of Public Health, Faculty of Health Science, Johannesburg, South Africa
- Institute of Biodiversity, Animal Health and Comparative Medicine, G12 8QQ, University of Glasgow, Glasgow, United Kingdom
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81
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Masalu JP, Finda M, Okumu FO, Minja EG, Mmbando AS, Sikulu-Lord MT, Ogoma SB. Efficacy and user acceptability of transfluthrin-treated sisal and hessian decorations for protecting against mosquito bites in outdoor bars. Parasit Vectors 2017; 10:197. [PMID: 28427437 PMCID: PMC5397833 DOI: 10.1186/s13071-017-2132-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Accepted: 04/05/2017] [Indexed: 11/16/2022] Open
Abstract
Background A number of mosquito vectors bite and rest outdoors, which contributes to sustained residual malaria transmission in endemic areas. Spatial repellents are thought to create a protective “bubble” within which mosquito bites are reduced and may be ideal for outdoor use. This study builds on previous studies that proved efficacy of transfluthrin-treated hessian strips against outdoor biting mosquitoes. The goal of this study was to modify strips into practical, attractive and acceptable transfluthrin treated sisal and hessian emanators that confer protection against potential infectious bites before people use bed nets especially in the early evening and outdoors. This study was conducted in Kilombero Valley, Ulanga District, south-eastern Tanzania. Results The protective efficacy of hand-crafted transfluthrin-treated sisal decorative baskets and hessian wall decorations against early evening outdoor biting malaria vectors was measured by human landing catches (HLC) in outdoor bars during peak outdoor mosquito biting activity (19:00 to 23:00 h). Treated baskets and wall decorations reduced bites of Anopheles arabiensis mosquitoes by 89% (Relative Rate, RR = 0.11, 95% confidence interval, CI: 0.09–0.15, P < 0.001) and 86% (RR = 0.14, 95% CI: 0.11–0.18, P < 0.001), respectively. In addition, they significantly reduced exposure to outdoor bites of Culex spp. by 66% (RR = 0.34, 95% CI: 0.22–0.52, P < 0.001) and 56% (RR = 0.44, 95% CI: 0.29–0.66, P < 0.001), respectively. Conclusion Locally hand-crafted transfluthrin-treated sisal decorative baskets and hessian wall decorations are readily acceptable and confer protection against outdoor biting malaria vectors in the early evening and outdoors: when people are resting on the verandas, porches or in outdoor social places such as bars and restaurants. Additional research can help support the use of such items as complementary interventions to expand protection to communities currently experiencing outdoor transmission of mosquito-borne pathogens.
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Affiliation(s)
- John P Masalu
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Off Mlabani Passage, Ifakara, P.O Box 53, Morogoro, United Republic of Tanzania.
| | - Marceline Finda
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Off Mlabani Passage, Ifakara, P.O Box 53, Morogoro, United Republic of Tanzania
| | - Fredros O Okumu
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Off Mlabani Passage, Ifakara, P.O Box 53, Morogoro, United Republic of Tanzania.,School of Public Health, University of the Witwatersrand, Johannesburg, South Africa.,Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK
| | - Elihaika G Minja
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Off Mlabani Passage, Ifakara, P.O Box 53, Morogoro, United Republic of Tanzania
| | - Arnold S Mmbando
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Off Mlabani Passage, Ifakara, P.O Box 53, Morogoro, United Republic of Tanzania
| | | | - Sheila B Ogoma
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Off Mlabani Passage, Ifakara, P.O Box 53, Morogoro, United Republic of Tanzania.,US National Research Council, National Academies of Sciences, Engineering and Medicine, Washington, DC, USA
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82
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A low technology emanator treated with the volatile pyrethroid transfluthrin confers long term protection against outdoor biting vectors of lymphatic filariasis, arboviruses and malaria. PLoS Negl Trop Dis 2017; 11:e0005455. [PMID: 28388682 PMCID: PMC5384659 DOI: 10.1371/journal.pntd.0005455] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Accepted: 03/03/2017] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The vapor phase of the volatile pyrethroid transfluthrin incapacitates mosquitoes and prevents them from feeding. Although existing emanator products for delivering volatile pyrethroids protect against outdoor mosquito bites, they are too short-lived to be practical or affordable for routine use in low-income settings. New transfluthrin emanators, comprised simply of treated hessian fabric strips, have recently proven highly protective against outdoor-biting vectors of lymphatic filariasis, arboviruses and malaria, but their full protective lifespan, minimum dose requirements, and range of protection have not previously been assessed. METHODOLOGY The effects of transfluthrin-treated hessian strips upon mosquito biting exposure of users and nearby non-users, as well as dependence of protection upon treatment dose, were measured outdoors in rural Tanzania using human landing catches (HLC). PRINCIPAL FINDINGS Strips treated with 10ml of transfluthrin prevented at least three quarters (p < 0.001) of outdoor bites by Anopheles arabiensis, Culex spp. and Mansonia spp. mosquitoes, and >90% protection against bites on warmer nights with higher evaporation rates, for at least one year. Strips treated with this high dose also reduced biting exposure of non-users at a distance of up to 5m from the strips for An. arabiensis (p < 0.001) and up to 2m for Mansonia spp. (p = 0.008), but provided no protection to non-users against Culex spp. No evidence of increased risk for non-users, caused by diversion of mosquitoes to unprotected individuals, was found at any distance within an 80m radius. A dose of only 1ml provided equivalent protection to the 10ml dose against An. arabiensis, Culex spp. and Mansonia spp. mosquitoes over 6 months (p < 0.001). CONCLUSIONS/SIGNIFICANCE Transfluthrin-treated hessian emanators provide safe, affordable, long-term protection against several different pathogen-transmitting mosquito taxa that attack humans outdoors, where they are usually active and cannot be protected by bed nets or residual sprays with conventional, solid-phase insecticides.
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83
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Milali MP, Sikulu-Lord MT, Govella NJ. Bites before and after bedtime can carry a high risk of human malaria infection. Malar J 2017; 16:91. [PMID: 28241888 PMCID: PMC5329919 DOI: 10.1186/s12936-017-1740-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Accepted: 02/20/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Understanding biting distribution of potentially infectious (parous) mosquitoes at various hours of the night would be useful in establishing the likely impact of bed nets on malaria transmission. Bed nets are highly effective at preventing biting by older malaria vectors, which occurs when most people are in bed. However, this behaviour is likely to vary across ecological settings and among mosquito populations. METHODS Field experiments were conducted in Minepa village within Kilombero Valley. Two outdoor catching stations located approximately 50 m from each other were established for mosquito collection. On each experimental night, mosquitoes were collected using human landing catch (HLC) by a single adult male at each station from 18:00 to 07:00 h. To compare the distribution of mosquito biting and the composition of their age structure, mosquitoes were sorted and recorded according to the hour they were collected. A sub-sample of Anopheles arabiensis was dissected to determine their parity status. Insectary-reared An. arabiensis within the semi-field system (SFS) with known age were also released in the SFS (10 m × 20 m) and recaptured hourly using HLC to determine the effect of parity on biting distribution. RESULTS Overall, there was no statistical association between the parity status and the biting time of An. arabiensis either in the field or in the SFS (P ≥ 0.05). The wild and insectary-reared An. arabiensis were observed to exhibit different hourly biting patterns. CONCLUSION The study has shown that mosquito biting time phenotype is not influenced by their parity status. These findings imply that the risk of human exposure to potentially infectious bites is equally distributed throughout the night, thus supplementary measures to protect people against bites in evening and morning are desirable.
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Affiliation(s)
- Masabho P Milali
- Ifakara Health Institute, Environmental Health and Ecological Sciences Thematic Group, Coordination Office, PO Box 78373, Kiko Avenue, Mikocheni, Dar es Salaam, United Republic of Tanzania.,Marquette University, Department of Mathematics, Statistics and Computer Sciences, Milwaukee, WI, USA
| | - Maggy T Sikulu-Lord
- Ifakara Health Institute, Environmental Health and Ecological Sciences Thematic Group, Coordination Office, PO Box 78373, Kiko Avenue, Mikocheni, Dar es Salaam, United Republic of Tanzania.,QIMR Berghofer Medical Research Institute, Herston, QLD, 4006, Australia
| | - Nicodem J Govella
- Ifakara Health Institute, Environmental Health and Ecological Sciences Thematic Group, Coordination Office, PO Box 78373, Kiko Avenue, Mikocheni, Dar es Salaam, United Republic of Tanzania.
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84
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Hardy A, Makame M, Cross D, Majambere S, Msellem M. Using low-cost drones to map malaria vector habitats. Parasit Vectors 2017; 10:29. [PMID: 28088225 PMCID: PMC5237572 DOI: 10.1186/s13071-017-1973-3] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 01/05/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND There is a growing awareness that if we are to achieve the ambitious goal of malaria elimination, we must compliment indoor-based vector control interventions (such as bednets and indoor spraying) with outdoor-based interventions such as larval source management (LSM). The effectiveness of LSM is limited by our capacity to identify and map mosquito aquatic habitats. This study provides a proof of concept for the use of a low-cost (< $1000) drone (DJI Phantom) for mapping water bodies in seven sites across Zanzibar including natural water bodies, irrigated and non-irrigated rice paddies, peri-urban and urban locations. RESULTS With flying times of less than 30 min for each site, high-resolution (7 cm) georeferenced images were successfully generated for each of the seven sites, covering areas up to 30 ha. Water bodies were readily identifiable in the imagery, as well as ancillary information for planning LSM activities (access routes to water bodies by road and foot) and public health management (e.g. identification of drinking water sources, mapping individual households and the nature of their construction). CONCLUSION The drone-based surveys carried out in this study provide a low-cost and flexible solution to mapping water bodies for operational dissemination of LSM initiatives in mosquito vector-borne disease elimination campaigns. Generated orthomosaics can also be used to provide vital information for other public health planning activities.
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Affiliation(s)
- Andy Hardy
- Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, UK.
| | - Makame Makame
- Zanzibar Malaria Elimination Programme, Zanzibar Ministry of Health, Stone Town, Zanzibar, United Republic of Tanzania
| | - Dónall Cross
- Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Aberystwyth, UK
| | - Silas Majambere
- Innovative Vector Control Consortium, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Mwinyi Msellem
- Zanzibar Malaria Elimination Programme, Zanzibar Ministry of Health, Stone Town, Zanzibar, United Republic of Tanzania
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Stevenson JC, Pinchoff J, Muleba M, Lupiya J, Chilusu H, Mwelwa I, Mbewe D, Simubali L, Jones CM, Chaponda M, Coetzee M, Mulenga M, Pringle JC, Shields T, Curriero FC, Norris DE. Spatio-temporal heterogeneity of malaria vectors in northern Zambia: implications for vector control. Parasit Vectors 2016; 9:510. [PMID: 27655231 PMCID: PMC5031275 DOI: 10.1186/s13071-016-1786-9] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Accepted: 09/01/2016] [Indexed: 11/16/2022] Open
Abstract
Background Despite large reductions in malaria burden across Zambia, some regions continue to experience extremely high malaria transmission. In Nchelenge District, Luapula Province, northern Zambia, almost half the human population carries parasites. Intervention coverage has increased substantially over the past decade, but comprehensive district-wide entomological studies to guide delivery of vector control measures are lacking. This study describes the bionomics and spatio-temporal patterns of malaria vectors in Nchelenge over a two and a half year period, investigates what household factors are associated with high vector densities and determines why vector control may not have been effective in the past to better guide future control efforts. Methods Between April 2012 and September 2014, twenty-seven households from across Nchelenge District were randomly selected for monthly light trap collections of mosquitoes. Anopheline mosquitoes were identified morphologically and molecularly to species. Foraging rates were estimated and sporozoite rates were determined by circumsporozoite ELISAs to calculate annual entomological inoculation rates. Blood feeding rates and host preference were determined by PCR. Zero-inflated negative binomial models measured environmental and household factors associated with mosquito abundance at study households such as season, proximity to the lake, and use of vector control measures. Results The dominant species in Nchelenge was An. funestus (s.s.) with An. gambiae (s.s.) as a secondary vector. Both vectors were found together in large numbers across the district and the combined EIRs of the two vectors exceeded 80 infectious bites per person per annum. An. funestus household densities increased in the dry season whilst An. gambiae surged during the rains. Presence of insecticide treated nets (ITNs) and closed eaves in the houses were found to be associated with fewer numbers of An. gambiae but not An. funestus. There was no association with indoor residual spraying (IRS). Conclusion In Nchelenge, the co-existence of two highly anthropophagic vectors, present throughout the year, is likely to be driving the high malaria transmission evident in the district. The vectors here have been shown to be highly resistant to pyrethroids used for IRS during the study. Vector control interventions in this area would have to be multifaceted and district-wide for effective control of malaria. Electronic supplementary material The online version of this article (doi:10.1186/s13071-016-1786-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jennifer C Stevenson
- The W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, MD, 21205, USA. .,Macha Research Trust, P.O. Box 630166, Choma, Zambia.
| | - Jessie Pinchoff
- The W. Harry Feinstone Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, MD, 21205, USA
| | - Mbanga Muleba
- Tropical Diseases Research Centre Room 727, Ndola Central Hospital, P.O. Box 71769, Ndola, Zambia
| | - James Lupiya
- Tropical Diseases Research Centre Room 727, Ndola Central Hospital, P.O. Box 71769, Ndola, Zambia
| | - Hunter Chilusu
- Tropical Diseases Research Centre Room 727, Ndola Central Hospital, P.O. Box 71769, Ndola, Zambia
| | - Ian Mwelwa
- Tropical Diseases Research Centre Room 727, Ndola Central Hospital, P.O. Box 71769, Ndola, Zambia
| | - David Mbewe
- Tropical Diseases Research Centre Room 727, Ndola Central Hospital, P.O. Box 71769, Ndola, Zambia
| | | | - Christine M Jones
- The W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, MD, 21205, USA
| | - Mike Chaponda
- Tropical Diseases Research Centre Room 727, Ndola Central Hospital, P.O. Box 71769, Ndola, Zambia
| | - Maureen Coetzee
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Modest Mulenga
- Tropical Diseases Research Centre Room 727, Ndola Central Hospital, P.O. Box 71769, Ndola, Zambia
| | - Julia C Pringle
- The W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, MD, 21205, USA
| | - Tim Shields
- The W. Harry Feinstone Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, MD, 21205, USA
| | - Frank C Curriero
- The W. Harry Feinstone Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, MD, 21205, USA
| | - Douglas E Norris
- The W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, MD, 21205, USA
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Riveron JM, Osae M, Egyir-Yawson A, Irving H, Ibrahim SS, Wondji CS. Multiple insecticide resistance in the major malaria vector Anopheles funestus in southern Ghana: implications for malaria control. Parasit Vectors 2016; 9:504. [PMID: 27628765 PMCID: PMC5024453 DOI: 10.1186/s13071-016-1787-8] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Accepted: 09/01/2016] [Indexed: 12/04/2022] Open
Abstract
BACKGROUND Understanding the dynamics of insecticide resistance in African malaria vectors is crucial for successful implementation of resistance management strategies in the continent. This study reports a high and multiple insecticide resistance in Anopheles funestus from southern Ghana which could compromise the Malaria Operational Plan in this country, if not tackled. Adult Anopheles mosquitoes were collected in Obuasi and Adawukwa, in southern Ghana. Plasmodium infection rates, susceptibility to the main insecticides used in public health and the molecular basis of insecticide resistance were established. RESULTS An. funestus (sensu stricto) (s.s.) was the predominant mosquito species found resting inside the houses in Obuasi, while at Adawukwa it was found together with An. coluzzii. Parasite rates were high in An. funestus (s.s.) populations from both localities, with Plasmodium infection rates greater than 12.5 %. Both, An. funestus (s.s.) and An. coluzzii, from the two sites exhibited high resistance to the insecticide from various classes including the pyrethroids, carbamates and DDT, but remained fully susceptible to the organophosphates. A preliminary characterization of the underlying molecular mechanisms of resistance in An. funestus (s.s.) populations from both sites revealed that CYP6P9a, CYP6P9b, CYP6M7 and GSTe2 genes are upregulated, markedly higher in Obuasi (between 3.35 and 1.83 times) than in Adawukwa population. The frequency of L119F-GSTe2 and A296S-RDL resistance markers were also higher in Obuasi (42.5 and 68.95 % higher), compared with An. funestus (s.s.) populations from Adawukwa. These findings suggest that the similar resistance pattern observed in both An. funestus (s.s.) populations are driven by different mechanisms. CONCLUSIONS Resistance to multiple insecticides in public health use is present in malaria vectors from Ghana with major resistance genes already operating in the field. This should be taken into consideration in the design of resistance management strategies to avoid operational failure.
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Affiliation(s)
- Jacob M. Riveron
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, UK
- Research Unit Liverpool School of Tropical Medicine, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale, P.O Box 288, Yaoundé, Cameroon
| | | | | | - Helen Irving
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, UK
| | - Sulaiman S. Ibrahim
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, UK
- Department of Biochemistry, Bayero University, PMB 3011 Kano, Nigeria
| | - Charles S. Wondji
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, UK
- Research Unit Liverpool School of Tropical Medicine, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale, P.O Box 288, Yaoundé, Cameroon
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87
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Main BJ, Lee Y, Ferguson HM, Kreppel KS, Kihonda A, Govella NJ, Collier TC, Cornel AJ, Eskin E, Kang EY, Nieman CC, Weakley AM, Lanzaro GC. The Genetic Basis of Host Preference and Resting Behavior in the Major African Malaria Vector, Anopheles arabiensis. PLoS Genet 2016; 12:e1006303. [PMID: 27631375 PMCID: PMC5025075 DOI: 10.1371/journal.pgen.1006303] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2016] [Accepted: 08/16/2016] [Indexed: 11/19/2022] Open
Abstract
Malaria transmission is dependent on the propensity of Anopheles mosquitoes to bite humans (anthropophily) instead of other dead end hosts. Recent increases in the usage of Long Lasting Insecticide Treated Nets (LLINs) in Africa have been associated with reductions in highly anthropophilic and endophilic vectors such as Anopheles gambiae s.s., leaving species with a broader host range, such as Anopheles arabiensis, as the most prominent remaining source of transmission in many settings. An. arabiensis appears to be more of a generalist in terms of its host choice and resting behavior, which may be due to phenotypic plasticity and/or segregating allelic variation. To investigate the genetic basis of host choice and resting behavior in An. arabiensis we sequenced the genomes of 23 human-fed and 25 cattle-fed mosquitoes collected both in-doors and out-doors in the Kilombero Valley, Tanzania. We identified a total of 4,820,851 SNPs, which were used to conduct the first genome-wide estimates of "SNP heritability" for host choice and resting behavior in this species. A genetic component was detected for host choice (human vs cow fed; permuted P = 0.002), but there was no evidence of a genetic component for resting behavior (indoors versus outside; permuted P = 0.465). A principal component analysis (PCA) segregated individuals based on genomic variation into three groups which were characterized by differences at the 2Rb and/or 3Ra paracentromeric chromosome inversions. There was a non-random distribution of cattle-fed mosquitoes between the PCA clusters, suggesting that alleles linked to the 2Rb and/or 3Ra inversions may influence host choice. Using a novel inversion genotyping assay, we detected a significant enrichment of the standard arrangement (non-inverted) of 3Ra among cattle-fed mosquitoes (N = 129) versus all non-cattle-fed individuals (N = 234; χ2, p = 0.007). Thus, tracking the frequency of the 3Ra in An. arabiensis populations may be of use to infer selection on host choice behavior within these vector populations; possibly in response to vector control. Controlled host-choice assays are needed to discern whether the observed genetic component has a direct relationship with innate host preference. A better understanding of the genetic basis for host feeding behavior in An. arabiensis may also open avenues for novel vector control strategies based on driving genes for zoophily into wild mosquito populations.
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Affiliation(s)
- Bradley J Main
- Vector Genetics Laboratory, Department of Pathology, Microbiology and Immunology/University of California, Davis, Davis, California, United States of America
- * E-mail:
| | - Yoosook Lee
- Vector Genetics Laboratory, Department of Pathology, Microbiology and Immunology/University of California, Davis, Davis, California, United States of America
| | - Heather M. Ferguson
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
| | - Katharina S. Kreppel
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
- Environmental Health and Ecological Sciences Group, Ifakara Health Institute, Ifakara, United Republic of Tanzania
| | - Anicet Kihonda
- Environmental Health and Ecological Sciences Group, Ifakara Health Institute, Ifakara, United Republic of Tanzania
| | - Nicodem J. Govella
- Environmental Health and Ecological Sciences Group, Ifakara Health Institute, Ifakara, United Republic of Tanzania
| | - Travis C. Collier
- Vector Genetics Laboratory, Department of Pathology, Microbiology and Immunology/University of California, Davis, Davis, California, United States of America
| | - Anthony J. Cornel
- Department of Entomology and Nematology, University of California, Davis, Davis, California, United States of America
| | - Eleazar Eskin
- Department of Computer Science, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Eun Yong Kang
- Department of Computer Science, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Catelyn C. Nieman
- Vector Genetics Laboratory, Department of Pathology, Microbiology and Immunology/University of California, Davis, Davis, California, United States of America
| | - Allison M. Weakley
- Vector Genetics Laboratory, Department of Pathology, Microbiology and Immunology/University of California, Davis, Davis, California, United States of America
| | - Gregory C. Lanzaro
- Vector Genetics Laboratory, Department of Pathology, Microbiology and Immunology/University of California, Davis, Davis, California, United States of America
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Maia MF, Kreppel K, Mbeyela E, Roman D, Mayagaya V, Lobo NF, Ross A, Moore SJ. A crossover study to evaluate the diversion of malaria vectors in a community with incomplete coverage of spatial repellents in the Kilombero Valley, Tanzania. Parasit Vectors 2016; 9:451. [PMID: 27527601 PMCID: PMC4986272 DOI: 10.1186/s13071-016-1738-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Accepted: 08/03/2016] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND Malaria elimination is unlikely to occur if vector control efforts focus entirely on transmission occurring indoors without addressing vectors that bite outdoors and outside sleeping hours. Additional control tools such as spatial repellents may provide the personal protection required to fill this gap. However, since repellents do not kill mosquitoes it is unclear if vectors will be diverted from households that use spatial repellents to those that do not. METHODS A crossover study was performed over 24 weeks in Kilombero, Tanzania. The density of resting and blood-engorged mosquitoes and human blood index (HBI) of malaria vector species per household was measured among 90 households using or not using 0.03 % transfluthrin coils burned outdoors under three coverage scenarios: (i) no coverage (blank coils); (ii) complete coverage of repellent coils; and (iii) incomplete coverage of repellent and blank coils. Mosquitoes were collected three days a week for 24 weeks from the inside and outside of all participating households using mosquito aspirators. Paired indoor and outdoor human landing collections were performed in three random households for six consecutive nights to confirm repellent efficacy of the coils and local vector biting times. RESULTS The main vectors were Anopheles arabiensis and Anopheles funestus (sensu stricto), which fed outdoors, outside sleeping hours, on humans as well as animals. Anopheles arabiensis landings were reduced by 80 % by the spatial repellent although household densities were not reduced. The HBI for An. arabiensis was significantly higher among households without repellents in the incomplete coverage scenario compared to houses in the no coverage scenario (Odds ratio 1.71; 95 % CI: 1.04-2.83; P = 0.03). This indicated that An. arabiensis mosquitoes seeking a human blood meal were diverted from repellent users to non-users. The repellent coils did not affect An. funestus densities or HBI. CONCLUSIONS Substantial malaria vector activity is occurring outside sleeping hours in the Kilombero valley. Repellent coils provided some protection against local An. arabiensis but did not protect against local (and potentially pyrethroid-resistant) An. funestus. Pyrethroid-based spatial repellents may offer a degree of personal protection, however the overall public health benefit is doubtful and potentially iniquitous as their use may divert malaria vectors to those who do not use them.
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Affiliation(s)
- Marta Ferreira Maia
- Swiss Tropical and Public Health Institute, Socinstr. 57, Basel, CH-4002 Switzerland
- University of Basel, St. Petersplatz 1, CH-4002 Basel, Switzerland
- Ifakara Health Institute, P.O. Box 74, Bagamoyo, Pwani United Republic of Tanzania
| | - Katharina Kreppel
- Ifakara Health Institute, P.O. Box 74, Bagamoyo, Pwani United Republic of Tanzania
- University of Glasgow, Institute of Biodiversity Animal Health and Comparative Medicine, Glasgow, G12 8QQ UK
| | - Edgar Mbeyela
- Ifakara Health Institute, P.O. Box 74, Bagamoyo, Pwani United Republic of Tanzania
| | - Deogratius Roman
- Ifakara Health Institute, P.O. Box 74, Bagamoyo, Pwani United Republic of Tanzania
| | - Valeriana Mayagaya
- Ifakara Health Institute, P.O. Box 74, Bagamoyo, Pwani United Republic of Tanzania
| | - Neil F. Lobo
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN 46556 USA
| | - Amanda Ross
- Swiss Tropical and Public Health Institute, Socinstr. 57, Basel, CH-4002 Switzerland
- University of Basel, St. Petersplatz 1, CH-4002 Basel, Switzerland
| | - Sarah Jane Moore
- Swiss Tropical and Public Health Institute, Socinstr. 57, Basel, CH-4002 Switzerland
- University of Basel, St. Petersplatz 1, CH-4002 Basel, Switzerland
- Ifakara Health Institute, P.O. Box 74, Bagamoyo, Pwani United Republic of Tanzania
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89
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Jaleta KT, Hill SR, Birgersson G, Tekie H, Ignell R. Chicken volatiles repel host-seeking malaria mosquitoes. Malar J 2016; 15:354. [PMID: 27439360 PMCID: PMC4955153 DOI: 10.1186/s12936-016-1386-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 06/14/2016] [Indexed: 12/03/2022] Open
Abstract
Background Anopheles arabiensis is a dominant vector of malaria in sub-Saharan Africa, which feeds indoors and outdoors on human and other vertebrate hosts, making it a difficult species to control with existing control methods. Novel methods that reduce human-vector interactions are, therefore, required to improve the impact of vector control programmes. Investigating the mechanisms underlying the host discrimination process in An. arabiensis could provide valuable knowledge leading to the development of novel control technologies. In this study, a host census and blood meal analysis were conducted to determine the host selection behaviour of An. arabiensis. Since mosquitoes select and discriminate among hosts primarily using olfaction, the volatile headspace of the preferred non-human host and non-host species, were collected. Using combined gas chromatography and electroantennographic detection analysis followed by combined gas chromatography and mass spectrometry, the bioactive compounds in the headspace collections were identified. The efficiency of the identified non-host compounds to repel host-seeking malaria mosquitoes was tested under field conditions. Results The host census and blood meal analyses demonstrated that An. arabiensis strongly prefers human blood when host seeking indoors, while it randomly feeds on cattle, goats and sheep when found outdoors. However, An. arabiensis avoids chickens despite their relatively high abundance, indicating that chickens are a non-host species for this vector. Eleven bioactive compounds were found in the headspace of the non-host species. Six of these were species-specific, out of which four were identified using combined gas chromatography and mass spectrometry. When tested in the field, the chicken-specific compounds, isobutyl butyrate, naphthalene, hexadecane and trans-limonene oxide, and the generic host compounds, limonene, cis-limonene oxide and β-myrcene, significantly reduced trap catches within the house compared to a negative control. A significant reduction in trap catch was also observed when suspending a caged chicken next to the trap. Conclusions Non-host volatiles repel host-seeking An. arabiensis and thus play a significant role in host discrimination. As such, this study demonstrates that non-host volatiles can provide protection to humans at risk of mosquito-vectored diseases in combination with established control programmes. Electronic supplementary material The online version of this article (doi:10.1186/s12936-016-1386-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Kassahun T Jaleta
- Unit of Chemical Ecology, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, P. O. Box 102, 23053, Alnarp, Sweden.,Department of Zoological Sciences, College of Natural Science, Addis Ababa University, P. O. Box 1176, Addis Ababa, Ethiopia
| | - Sharon Rose Hill
- Unit of Chemical Ecology, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, P. O. Box 102, 23053, Alnarp, Sweden
| | - Göran Birgersson
- Unit of Chemical Ecology, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, P. O. Box 102, 23053, Alnarp, Sweden
| | - Habte Tekie
- Department of Zoological Sciences, College of Natural Science, Addis Ababa University, P. O. Box 1176, Addis Ababa, Ethiopia
| | - Rickard Ignell
- Unit of Chemical Ecology, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, P. O. Box 102, 23053, Alnarp, Sweden.
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90
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Ndo C, Kopya E, Menze-Djantio B, Toto JC, Awono-Ambene P, Lycett G, Wondji CS. High susceptibility of wild Anopheles funestus to infection with natural Plasmodium falciparum gametocytes using membrane feeding assays. Parasit Vectors 2016; 9:341. [PMID: 27301693 PMCID: PMC4908716 DOI: 10.1186/s13071-016-1626-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Accepted: 06/07/2016] [Indexed: 01/15/2023] Open
Abstract
Background Anopheles funestus is a major vector of malaria in sub-Saharan Africa. However, because it is difficult to colonize, research on this mosquito species has lagged behind other vectors, particularly the understanding of its susceptibility and interactions with the Plasmodium parasite. The present study reports one of the first experimental infections of progeny from wild-caught An. funestus with the P. falciparum parasite providing a realistic avenue for the characterisation of immune responses associated with this infection. Methods Wild-fed resting An. funestus females were collected using electric aspirators and kept in cages for four days until they were fully gravid and ready to oviposit. The resulting eggs were reared to adults F1 mosquitoes under insectary conditions. Three to five day-old An. funestus F1 females were fed with infected blood taken from gametocyte carriers using an artificial glass-parafilm feeding system. Feeding rate was recorded and fed mosquitoes were dissected at day 7 to count oocysts in midguts. Parallel experiments were performed with the known Plasmodium-susceptible An. coluzzii Ngousso laboratory strain, to monitor our blood handling procedures and infectivity of gametocytes. Results The results revealed that An. funestus displays high and similar level of susceptibility to Plasmodium infection compared to An. coluzzii, and suggest that our methodology produces robust feeding and infection rates in wild An. funestus progeny. The prevalence of infection in An. funestus mosquitoes was 38.52 % (range 6.25–100 %) and the median oocyst number was 12.5 (range 1–139). In parallel, the prevalence in An. coluzzii was 39.92 % (range 6.85–97.5 %), while the median oocyst number was 32.1 (range 1–351). Conclusions Overall, our observations are in line with the fact that both species are readily infected with P. falciparum, the most common and dangerous malaria parasite in sub-Saharan Africa, and since An. funestus is widespread throughout Africa, malaria vector control research and implementation needs to seriously address this vector species too. Additionally, the present work indicates that it is feasible to generate large number of wild F1 infected An. funestus mosquitoes using membrane feeding assays, which can be used for comprehensive study of interactions with the Plasmodium parasite. Electronic supplementary material The online version of this article (doi:10.1186/s13071-016-1626-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Cyrille Ndo
- Malaria Research Laboratory, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon. .,Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK. .,Faculty of Medicine and Pharmaceutical Sciences, University of Douala, P.O. Box 2701, Douala, Cameroon.
| | - Edmond Kopya
- Malaria Research Laboratory, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon.,Faculty of Sciences, University of Yaoundé I, P.O. Box 337, Yaoundé, Cameroon
| | - Benjamin Menze-Djantio
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.,Research Unit Liverpool School of Tropical Medicine, OCEAC, P.O. Box 288, Yaoundé, Cameroon
| | - Jean Claude Toto
- Malaria Research Laboratory, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon
| | - Parfait Awono-Ambene
- Malaria Research Laboratory, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon
| | - Gareth Lycett
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Charles S Wondji
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.,Research Unit Liverpool School of Tropical Medicine, OCEAC, P.O. Box 288, Yaoundé, Cameroon
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91
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Kaindoa EW, Mkandawile G, Ligamba G, Kelly-Hope LA, Okumu FO. Correlations between household occupancy and malaria vector biting risk in rural Tanzanian villages: implications for high-resolution spatial targeting of control interventions. Malar J 2016; 15:199. [PMID: 27067147 PMCID: PMC4828883 DOI: 10.1186/s12936-016-1268-8] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Accepted: 04/01/2016] [Indexed: 11/14/2022] Open
Abstract
Background Fine-scale targeting of interventions is increasingly important where epidemiological disease profiles depict high geographical stratifications. This study verified correlations between household biomass and mosquito house-entry using experimental hut studies, and then demonstrated how geographical foci of mosquito biting risk can be readily identified based on spatial distributions of household occupancies in villages. Methods A controlled 4 × 4 Latin square experiment was conducted in rural Tanzania, in which no, one, three or six adult male volunteers slept under intact bed nets, in experimental huts. Mosquitoes entering the huts were caught using exit interception traps on eaves and windows. Separately, monthly mosquito collections were conducted in 96 randomly selected households in three villages using CDC light traps between March-2012 and November-2013. The number of people sleeping in the houses and other household and environmental characteristics were recorded. ArcGIS 10 (ESRI-USA) spatial analyst tool, Gi* Ord Statistic was used to analyse clustering of vector densities and household occupancy. Results The densities of all mosquito genera increased in huts with one, three or six volunteers, relative to huts with no volunteers, and direct linear correlations within tested ranges (P < 0.001). Significant geographical clustering of indoor densities of malaria vectors, Anopheles arabiensis and Anopheles funestus, but not Culex or Mansonia species occurred in locations where households with highest occupancy were also most clustered (Gi* P ≤ 0.05, and Gi* Z-score ≥1.96). Conclusions This study demonstrates strong correlations between household occupancy and malaria vector densities in households, but also spatial correlations of these variables within and between villages in rural southeastern Tanzania. Fine-scale clustering of indoor densities of vectors within and between villages occurs in locations where houses with highest occupancy are also clustered. The study indicates potential for using household census data to preliminarily identify households with greatest Anopheles mosquito biting risk.
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Affiliation(s)
- Emmanuel W Kaindoa
- Environmental Health and Ecological Sciences Thematic Group, Ifakara Health Institute, Morogoro, Tanzania. .,Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, UK. .,School of Public Health, University of the Witwatersrand, Johannesburg, South Africa.
| | - Gustav Mkandawile
- Environmental Health and Ecological Sciences Thematic Group, Ifakara Health Institute, Morogoro, Tanzania
| | - Godfrey Ligamba
- Environmental Health and Ecological Sciences Thematic Group, Ifakara Health Institute, Morogoro, Tanzania
| | | | - Fredros O Okumu
- Environmental Health and Ecological Sciences Thematic Group, Ifakara Health Institute, Morogoro, Tanzania.,School of Public Health, University of the Witwatersrand, Johannesburg, South Africa
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Das S, Muleba M, Stevenson JC, Norris DE. Habitat Partitioning of Malaria Vectors in Nchelenge District, Zambia. Am J Trop Med Hyg 2016; 94:1234-44. [PMID: 27001755 DOI: 10.4269/ajtmh.15-0735] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Accepted: 02/07/2016] [Indexed: 11/07/2022] Open
Abstract
Nchelenge District in Luapula Province, northern Zambia, experiences holoendemic malaria despite implementation of vector control programs. The major Anopheles vectors that contribute to Plasmodium falciparum transmission in this area had not previously been well defined. Three collections performed during the 2012 wet and dry seasons and the 2013 wet season revealed Anopheles funestus sensu stricto and Anopheles gambiae sensu stricto as the main vectors, where 80-85% of each collection was composed of An. funestus Both vectors were found to be highly anthropophilic, and An. funestus has higher sporozoite infection rates (SIRs) and entomological inoculation rates (EIRs) year-round compared with An. gambiae: SIRs of 1.8-3.0% and 0-2.5%, respectively, and EIRs of 3.7-41.5 infectious bites per 6-month period (ib/p/6mo) and 0-5.9 ib/p/6mo, respectively. Spatial and temporal changes in each vector's dynamics and bionomics were also observed. Anopheles funestus was the predominant vector in the villages near Kenani Stream in both wet and dry seasons, whereas An. gambiae was found to be the main vector in areas near Lake Mweru during the wet season. The vector data illustrate the need for broader temporal and spatial sampling in Nchelenge and present unique opportunities to further our understanding of malarial transmission and implications for malarial control in high-risk areas.
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Affiliation(s)
- Smita Das
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland; Tropical Disease Research Centre, Ndola Central Hospital, Ndola, Zambia; Macha Research Trust, Choma, Zambia
| | - Mbanga Muleba
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland; Tropical Disease Research Centre, Ndola Central Hospital, Ndola, Zambia; Macha Research Trust, Choma, Zambia
| | - Jennifer C Stevenson
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland; Tropical Disease Research Centre, Ndola Central Hospital, Ndola, Zambia; Macha Research Trust, Choma, Zambia
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Matowo NS, Koekemoer LL, Moore SJ, Mmbando AS, Mapua SA, Coetzee M, Okumu FO. Combining Synthetic Human Odours and Low-Cost Electrocuting Grids to Attract and Kill Outdoor-Biting Mosquitoes: Field and Semi-Field Evaluation of an Improved Mosquito Landing Box. PLoS One 2016; 11:e0145653. [PMID: 26789733 PMCID: PMC4720432 DOI: 10.1371/journal.pone.0145653] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Accepted: 12/07/2015] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND On-going malaria transmission is increasingly mediated by outdoor-biting vectors, especially where indoor insecticidal interventions such as long-lasting insecticide treated nets (LLINs) are widespread. Often, the vectors are also physiologically resistant to insecticides, presenting major obstacles for elimination. We tested a combination of electrocuting grids with synthetic odours as an alternative killing mechanism against outdoor-biting mosquitoes. METHODS An odour-baited device, the Mosquito Landing Box (MLB), was improved by fitting it with low-cost electrocuting grids to instantly kill mosquitoes attracted to the odour lure, and automated photo switch to activate attractant-dispensing and mosquito-killing systems between dusk and dawn. MLBs fitted with one, two or three electrocuting grids were compared outdoors in a malaria endemic village in Tanzania, where vectors had lost susceptibility to pyrethroids. MLBs with three grids were also tested in a large semi-field cage (9.6 × 9.6 × 4.5m), to assess effects on biting-densities of laboratory-reared Anopheles arabiensis on volunteers sitting near MLBs. RESULTS Significantly more mosquitoes were killed when MLBs had two or three grids, than one grid in wet and dry seasons (P<0.05). The MLBs were highly efficient against Mansonia species and malaria vector, An. arabiensis. Of all mosquitoes, 99% were non-blood fed, suggesting host-seeking status. In the semi-field, the MLBs reduced mean number of malaria mosquitoes attempting to bite humans fourfold. CONCLUSION The improved odour-baited MLBs effectively kill outdoor-biting malaria vector mosquitoes that are behaviourally and physiologically resistant to insecticidal interventions e.g. LLINs. The MLBs reduce human-biting vector densities even when used close to humans, and are insecticide-free, hence potentially antiresistance. The devices could either be used as surveillance tools or complementary mosquito control interventions to accelerate malaria elimination where outdoor transmission is significant.
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Affiliation(s)
- Nancy S. Matowo
- Environmental and Ecological Sciences Thematic Group, Ifakara Health Institute, Dar es Salaam, Tanzania
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Lizette L. Koekemoer
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
- Centre for Opportunistic, Tropical and Hospital Infections, National Institute for Communicable Diseases, Johannesburg, South Africa
| | - Sarah J. Moore
- Environmental and Ecological Sciences Thematic Group, Ifakara Health Institute, Dar es Salaam, Tanzania
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Arnold S. Mmbando
- Environmental and Ecological Sciences Thematic Group, Ifakara Health Institute, Dar es Salaam, Tanzania
| | - Salum A. Mapua
- Environmental and Ecological Sciences Thematic Group, Ifakara Health Institute, Dar es Salaam, Tanzania
| | - Maureen Coetzee
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
- Centre for Opportunistic, Tropical and Hospital Infections, National Institute for Communicable Diseases, Johannesburg, South Africa
| | - Fredros O. Okumu
- Environmental and Ecological Sciences Thematic Group, Ifakara Health Institute, Dar es Salaam, Tanzania
- School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
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St Laurent B, Cooke M, Krishnankutty SM, Asih P, Mueller JD, Kahindi S, Ayoma E, Oriango RM, Thumloup J, Drakeley C, Cox J, Collins FH, Lobo NF, Stevenson JC. Molecular Characterization Reveals Diverse and Unknown Malaria Vectors in the Western Kenyan Highlands. Am J Trop Med Hyg 2016; 94:327-35. [PMID: 26787150 DOI: 10.4269/ajtmh.15-0562] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Accepted: 11/03/2015] [Indexed: 12/21/2022] Open
Abstract
The success of mosquito-based malaria control is dependent upon susceptible bionomic traits in local malaria vectors. It is crucial to have accurate and reliable methods to determine mosquito species composition in areas subject to malaria. An unexpectedly diverse set of Anopheles species was collected in the western Kenyan highlands, including unidentified and potentially new species carrying the malaria parasite Plasmodium falciparum. This study identified 2,340 anopheline specimens using both ribosomal DNA internal transcribed spacer region 2 and mitochondrial DNA cytochrome oxidase subunit 1 loci. Seventeen distinct sequence groups were identified. Of these, only eight could be molecularly identified through comparison to published and voucher sequences. Of the unidentified species, four were found to carry P. falciparum by circumsporozoite enzyme-linked immunosorbent assay and polymerase chain reaction, the most abundant of which had infection rates comparable to a primary vector in the area, Anopheles funestus. High-quality adult specimens of these unidentified species could not be matched to museum voucher specimens or conclusively identified using multiple keys, suggesting that they may have not been previously described. These unidentified vectors were captured outdoors. Diverse and unknown species have been incriminated in malaria transmission in the western Kenya highlands using molecular identification of unusual morphological variants of field specimens. This study demonstrates the value of using molecular methods to compliment vector identifications and highlights the need for accurate characterization of mosquito species and their associated behaviors for effective malaria control.
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Affiliation(s)
- Brandyce St Laurent
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana; Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom; Centre for Global Health Research, Kenya Medical Research Institute/Centers for Disease Control and Prevention, Kisumu, Kenya; Western Triangle Research Center, Montana State University, Conrad, Montana; Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | - Mary Cooke
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana; Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom; Centre for Global Health Research, Kenya Medical Research Institute/Centers for Disease Control and Prevention, Kisumu, Kenya; Western Triangle Research Center, Montana State University, Conrad, Montana; Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | - Sindhu M Krishnankutty
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana; Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom; Centre for Global Health Research, Kenya Medical Research Institute/Centers for Disease Control and Prevention, Kisumu, Kenya; Western Triangle Research Center, Montana State University, Conrad, Montana; Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | - Puji Asih
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana; Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom; Centre for Global Health Research, Kenya Medical Research Institute/Centers for Disease Control and Prevention, Kisumu, Kenya; Western Triangle Research Center, Montana State University, Conrad, Montana; Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | - John D Mueller
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana; Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom; Centre for Global Health Research, Kenya Medical Research Institute/Centers for Disease Control and Prevention, Kisumu, Kenya; Western Triangle Research Center, Montana State University, Conrad, Montana; Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | - Samuel Kahindi
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana; Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom; Centre for Global Health Research, Kenya Medical Research Institute/Centers for Disease Control and Prevention, Kisumu, Kenya; Western Triangle Research Center, Montana State University, Conrad, Montana; Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | - Elizabeth Ayoma
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana; Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom; Centre for Global Health Research, Kenya Medical Research Institute/Centers for Disease Control and Prevention, Kisumu, Kenya; Western Triangle Research Center, Montana State University, Conrad, Montana; Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | - Robin M Oriango
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana; Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom; Centre for Global Health Research, Kenya Medical Research Institute/Centers for Disease Control and Prevention, Kisumu, Kenya; Western Triangle Research Center, Montana State University, Conrad, Montana; Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | - Julie Thumloup
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana; Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom; Centre for Global Health Research, Kenya Medical Research Institute/Centers for Disease Control and Prevention, Kisumu, Kenya; Western Triangle Research Center, Montana State University, Conrad, Montana; Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | - Chris Drakeley
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana; Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom; Centre for Global Health Research, Kenya Medical Research Institute/Centers for Disease Control and Prevention, Kisumu, Kenya; Western Triangle Research Center, Montana State University, Conrad, Montana; Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | - Jonathan Cox
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana; Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom; Centre for Global Health Research, Kenya Medical Research Institute/Centers for Disease Control and Prevention, Kisumu, Kenya; Western Triangle Research Center, Montana State University, Conrad, Montana; Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | - Frank H Collins
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana; Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom; Centre for Global Health Research, Kenya Medical Research Institute/Centers for Disease Control and Prevention, Kisumu, Kenya; Western Triangle Research Center, Montana State University, Conrad, Montana; Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | - Neil F Lobo
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana; Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom; Centre for Global Health Research, Kenya Medical Research Institute/Centers for Disease Control and Prevention, Kisumu, Kenya; Western Triangle Research Center, Montana State University, Conrad, Montana; Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | - Jennifer C Stevenson
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana; Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom; Centre for Global Health Research, Kenya Medical Research Institute/Centers for Disease Control and Prevention, Kisumu, Kenya; Western Triangle Research Center, Montana State University, Conrad, Montana; Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
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95
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Maliti DV, Govella NJ, Killeen GF, Mirzai N, Johnson PCD, Kreppel K, Ferguson HM. Development and evaluation of mosquito-electrocuting traps as alternatives to the human landing catch technique for sampling host-seeking malaria vectors. Malar J 2015; 14:502. [PMID: 26670881 PMCID: PMC4681165 DOI: 10.1186/s12936-015-1025-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Accepted: 12/02/2015] [Indexed: 11/10/2022] Open
Abstract
Background The human landing catch (HLC) is the gold standard method for sampling host-seeking malaria vectors. However, the HLC is ethically questionable because it requires exposure of humans to potentially infectious mosquito bites. Methods Two exposure-free methods for sampling host-seeking mosquitoes were evaluated using electrocuting surfaces as potential replacements for HLC: (1) a previously evaluated, commercially available electrocuting grid (CA-EG) designed for killing flies, and (2) a custom-made mosquito electrocuting trap (MET) designed to kill African malaria vectors.
The MET and the CA-EG were evaluated relative to the HLC in a Latin Square experiment conducted in the Kilombero Valley, Tanzania. The sampling consistency of the traps across the night and at varying mosquito densities was investigated. Estimates of the proportion of mosquitoes caught indoors (Pi), proportion of human exposure occurring indoors (πi), and proportion of mosquitoes caught when most people are likely to be indoors (Pfl) were compared for all traps. Results Whereas the CA-EG performed poorly (<10 % of catch of HLC), sampling efficiency of the MET for sampling Anopheles funestuss.l. was indistinguishable from HLC indoors and outdoors. For Anopheles gambiae s.l., sampling sensitivity of MET was 20.9 % (95 % CI 10.3–42.2) indoors and 58.5 % (95 % CI 32.2–106.2) outdoors relative to HLC. There was no evidence of density-dependent sampling by the MET or CA-EG. Similar estimates of Pi were obtained for An. gambiaes.l. and An. funestus s.l. from all trapping methods. The proportion of mosquitoes caught when people are usually indoors (Pfl) was underestimated by the CA-EG and MET for An. gambiae s.l., but similar to the HLC for An. funestus. Estimates of the proportion of human exposure occurring indoors (πi) obtained from the CA-EG and MET were similar to the HLC for An. gambiae s.l., but overestimated for An. funestus. Conclusions The MET showed promise as an outdoor sampling tool for malaria vectors where it achieved >50 % sampling sensitivity relative to the HLC. The CA-EG had poor sampling sensitivity outdoors and inside. With further modification, the MET could provide an efficient and safer alternative to the HLC for the surveillance of mosquito vectors outdoors. Electronic supplementary material The online version of this article (doi:10.1186/s12936-015-1025-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Deodatus V Maliti
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Graham Kerr Building, Glasgow, G12 8QQ, UK. .,Environmental Health and Ecological Sciences, Ifakara Health Institute, PO Box 78373, Kiko Avenue, Mikocheni B, Dar es Salaam, Tanzania. .,School of Life Sciences, Nelson Mandela African Institute of Science and Technology Tanzania, PO Box 447, Arusha, Tanzania.
| | - Nicodem J Govella
- Environmental Health and Ecological Sciences, Ifakara Health Institute, PO Box 78373, Kiko Avenue, Mikocheni B, Dar es Salaam, Tanzania.
| | - Gerry F Killeen
- Environmental Health and Ecological Sciences, Ifakara Health Institute, PO Box 78373, Kiko Avenue, Mikocheni B, Dar es Salaam, Tanzania. .,Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.
| | - Nosrat Mirzai
- Bioelectronics Unit, University of Glasgow, Graham Kerr Building, Glasgow, G12 8QQ, UK.
| | - Paul C D Johnson
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Graham Kerr Building, Glasgow, G12 8QQ, UK.
| | - Katharina Kreppel
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Graham Kerr Building, Glasgow, G12 8QQ, UK. .,Environmental Health and Ecological Sciences, Ifakara Health Institute, PO Box 78373, Kiko Avenue, Mikocheni B, Dar es Salaam, Tanzania.
| | - Heather M Ferguson
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Graham Kerr Building, Glasgow, G12 8QQ, UK.
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Riveron JM, Chiumia M, Menze BD, Barnes KG, Irving H, Ibrahim SS, Weedall GD, Mzilahowa T, Wondji CS. Rise of multiple insecticide resistance in Anopheles funestus in Malawi: a major concern for malaria vector control. Malar J 2015; 14:344. [PMID: 26370361 PMCID: PMC4570681 DOI: 10.1186/s12936-015-0877-y] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Accepted: 08/28/2015] [Indexed: 11/25/2022] Open
Abstract
Background Deciphering the dynamics and evolution of insecticide resistance in malaria vectors is crucial for successful vector control. This study reports an increase of resistance
intensity and a rise of multiple insecticide resistance in Anopheles funestus in Malawi leading to reduced bed net efficacy. Methods Anopheles funestus group mosquitoes were collected in southern Malawi and the species composition, Plasmodium infection rate, susceptibility to insecticides and molecular bases of the resistance were analysed. Results Mosquito collection revealed a predominance of An. funestus group mosquitoes with a high hybrid rate (12.2 %) suggesting extensive species hybridization. An. funestus sensu stricto was the main Plasmodium vector (4.8 % infection). Consistently high levels of resistance to pyrethroid and carbamate insecticides were recorded and had increased between 2009 and 2014. Furthermore, the 2014 collection exhibited multiple insecticide resistance, notably to DDT, contrary to 2009. Increased pyrethroid resistance correlates with reduced efficacy of bed nets (<5 % mortality by Olyset® net), which can compromise control efforts. This change in resistance dynamics is mirrored by prevalent resistance mechanisms, firstly with increased over-expression of key pyrethroid resistance genes (CYP6Pa/b and CYP6M7) in 2014 and secondly, detection of the A296S-RDL dieldrin resistance mutation for the first time. However, the L119F-GSTe2 and kdr mutations were absent. Conclusions Such increased resistance levels and rise of multiple resistance highlight the need to rapidly implement resistance management strategies to preserve the effectiveness of existing insecticide-based control interventions. Electronic supplementary material The online version of this article (doi:10.1186/s12936-015-0877-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jacob M Riveron
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, UK.
| | - Martin Chiumia
- Malaria Alert Centre, College of Medicine, University of Malawi, Blantyre, Malawi.
| | - Benjamin D Menze
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, UK. .,Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale, PO Box 288, Yaoundé, Cameroon.
| | - Kayla G Barnes
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, UK.
| | - Helen Irving
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, UK.
| | - Sulaiman S Ibrahim
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, UK.
| | - Gareth D Weedall
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, UK.
| | - Themba Mzilahowa
- Malaria Alert Centre, College of Medicine, University of Malawi, Blantyre, Malawi.
| | - Charles S Wondji
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, UK.
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Menger DJ, Omusula P, Holdinga M, Homan T, Carreira AS, Vandendaele P, Derycke JL, Mweresa CK, Mukabana WR, van Loon JJA, Takken W. Field evaluation of a push-pull system to reduce malaria transmission. PLoS One 2015; 10:e0123415. [PMID: 25923114 PMCID: PMC4414508 DOI: 10.1371/journal.pone.0123415] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Accepted: 02/18/2015] [Indexed: 11/24/2022] Open
Abstract
Malaria continues to place a disease burden on millions of people throughout the tropics, especially in sub-Saharan Africa. Although efforts to control mosquito populations and reduce human-vector contact, such as long-lasting insecticidal nets and indoor residual spraying, have led to significant decreases in malaria incidence, further progress is now threatened by the widespread development of physiological and behavioural insecticide-resistance as well as changes in the composition of vector populations. A mosquito-directed push-pull system based on the simultaneous use of attractive and repellent volatiles offers a complementary tool to existing vector-control methods. In this study, the combination of a trap baited with a five-compound attractant and a strip of net-fabric impregnated with micro-encapsulated repellent and placed in the eaves of houses, was tested in a malaria-endemic village in western Kenya. Using the repellent delta-undecalactone, mosquito house entry was reduced by more than 50%, while the traps caught high numbers of outdoor flying mosquitoes. Model simulations predict that, assuming area-wide coverage, the addition of such a push-pull system to existing prevention efforts will result in up to 20-fold reductions in the entomological inoculation rate. Reductions of such magnitude are also predicted when mosquitoes exhibit a high resistance against insecticides. We conclude that a push-pull system based on non-toxic volatiles provides an important addition to existing strategies for malaria prevention.
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Affiliation(s)
- David J. Menger
- Laboratory of Entomology, Wageningen University, P.O. Box 8031, 6700 EH, Wageningen, The Netherlands
- * E-mail:
| | - Philemon Omusula
- International Centre of Insect Physiology and Ecology, P.O. Box 30772, GPO Nairobi, Kenya
| | - Maarten Holdinga
- Laboratory of Entomology, Wageningen University, P.O. Box 8031, 6700 EH, Wageningen, The Netherlands
| | - Tobias Homan
- Laboratory of Entomology, Wageningen University, P.O. Box 8031, 6700 EH, Wageningen, The Netherlands
| | - Ana S. Carreira
- CIEPQPF, Department of Chemical Engineering, University of Coimbra, Rua Sílvio Lima, 3030–790, Coimbra, Portugal
- Devan—Micropolis, Tecmaia-Parque da Ciência e Tecnologia da Maia, Rua Eng. Frederico Ulrich, 2650, 4470–605, Maia, Portugal
| | | | | | - Collins K. Mweresa
- Laboratory of Entomology, Wageningen University, P.O. Box 8031, 6700 EH, Wageningen, The Netherlands
- International Centre of Insect Physiology and Ecology, P.O. Box 30772, GPO Nairobi, Kenya
| | - Wolfgang Richard Mukabana
- International Centre of Insect Physiology and Ecology, P.O. Box 30772, GPO Nairobi, Kenya
- School of Biological Sciences, University of Nairobi, P.O. Box 30197–00100, GPO Nairobi, Kenya
| | - Joop J. A. van Loon
- Laboratory of Entomology, Wageningen University, P.O. Box 8031, 6700 EH, Wageningen, The Netherlands
| | - Willem Takken
- Laboratory of Entomology, Wageningen University, P.O. Box 8031, 6700 EH, Wageningen, The Netherlands
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98
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Sibling species of the Anopheles funestus group, and their infection with malaria and lymphatic filarial parasites, in archived and newly collected specimens from northeastern Tanzania. Malar J 2015; 14:104. [PMID: 25885457 PMCID: PMC4352238 DOI: 10.1186/s12936-015-0616-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2014] [Accepted: 02/20/2015] [Indexed: 11/13/2022] Open
Abstract
Background Studies on the East African coast have shown a recent dramatic decline in malaria vector density and change in composition of sibling species of the Anopheles gambiae complex, paralleled by a major decline in malaria incidence. In order to better understand the ongoing changes in vector-parasite dynamics in the area, and to allow for appropriate adjustment of control activities, the present study examined the composition, and malaria and lymphatic filarial infection, of sibling species of the Anopheles funestus group. Similar to the An. gambiae complex, the An. funestus group contains important vectors of both malaria and lymphatic filariasis. Methods Archived (from 2005–2012) and newly collected (from 2014) specimens of the An. funestus group collected indoors using CDC light traps in villages in northeastern Tanzania were analysed. They were identified to sibling species by PCR based on amplification of species-specific nucleotide sequence in the ITS2 region on rDNA genes. The specimens were furthermore examined for infection with Plasmodium falciparum and Wuchereria bancrofti by PCR. Results The identified sibling species were An. funestus s.s., Anopheles parensis, Anopheles rivulorum, and Anopheles leesoni, with the first being by far the most common (overall 94.4%). When comparing archived specimens from 2005–2007 to those from 2008–2012, a small but statistically significant decrease in proportion of An. funestus s.s. was noted, but otherwise observed temporal changes in sibling species composition were minor. No P. falciparum was detected in archived specimens, while 8.3% of the newly collected An. funestus s.s. were positive for this parasite. The overall W. bancrofti infection rate decreased from 14.8% in the 2005–2007 archived specimens to only 0.5% in the newly collected specimens, and with overall 93.3% of infections being in An. funestus s.s. Conclusion The study indicated that the composition of the An. funestus group had remained rather stable during the study period, with An. funestus s.s. being the most predominant. The study also showed increasing P. falciparum infection and decreasing W. bancrofti infection in An. funestus s.s. in the study period, most likely reflecting infection levels with these parasites in the human population in the area.
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99
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Mayagaya VS, Nkwengulila G, Lyimo IN, Kihonda J, Mtambala H, Ngonyani H, Russell TL, Ferguson HM. The impact of livestock on the abundance, resting behaviour and sporozoite rate of malaria vectors in southern Tanzania. Malar J 2015; 14:17. [PMID: 25604150 PMCID: PMC4311485 DOI: 10.1186/s12936-014-0536-8] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Accepted: 12/27/2014] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Increases in the coverage of long-lasting insecticidal nets (LLINs) have significantly reduced the abundance of Anopheles gambiae sensu stricto in several African settings, leaving its more zoophagic sibling species Anopheles arabiensis as the primary vector. This study investigated the impact of livestock ownership at the household level on the ecology and malaria infection rate of vectors in an area of Tanzania where An. arabiensis accounts for most malaria transmission. METHODS Mosquito vectors were collected resting inside houses, animal sheds and in outdoor resting boxes at households with and without livestock over three years in ten villages of the Kilombero Valley, Tanzania. Additionally, the abundance and sporozoite rate of vectors attempting to bite indoors at these households was assessed as an index of malaria exposure. RESULTS The mean abundance of An. gambiae s.l. biting indoors was similar at houses with and without livestock. In all years but one, the relative proportion of An. arabiensis within the An. gambiae s.l. species complex was higher at households with livestock. Livestock presence had a significant impact on malaria vector feeding and resting behaviour. Anopheles arabiensis were generally found resting in cattle sheds where livestock were present, and inside houses when absent. Correspondingly, the human blood index of An. arabiensis and An. funestus s.l. was significant reduced at households with livestock, whereas that of An. gambiae s.s. was unaffected. Whilst there was some evidence that sporozoite rates within the indoor-biting An. gambiae s.l population was significantly reduced at households with livestock, the significance of this effect varied depending on how background spatial variation was accounted for. CONCLUSIONS These results confirm that the presence of cattle at the household level can significantly alter the local species composition, feeding and resting behaviour of malaria vectors. However, the net impact of this livestock-associated variation in mosquito ecology on malaria exposure risk was unclear. Further investigation is required to distinguish whether the apparently lower sporozoite rates observed in An. gambiae s.l. at households with livestock is really a direct effect of cattle presence, or an indirect consequence of reduced risk within areas where livestock keepers choose to live.
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Affiliation(s)
- Valeriana S Mayagaya
- Environmental Health and Ecological Sciences, Ifakara Health Institute, PO Box 53, Ifakara, Tanzania.
| | - Gamba Nkwengulila
- Department of Zoology and Wildlife Conservation, University of Dar es Salaam, PO Box 35065, Dar es Salaam, Tanzania.
| | - Issa N Lyimo
- Environmental Health and Ecological Sciences, Ifakara Health Institute, PO Box 53, Ifakara, Tanzania.
| | - Japheti Kihonda
- Environmental Health and Ecological Sciences, Ifakara Health Institute, PO Box 53, Ifakara, Tanzania.
| | - Hassan Mtambala
- Environmental Health and Ecological Sciences, Ifakara Health Institute, PO Box 53, Ifakara, Tanzania.
| | - Hassan Ngonyani
- Environmental Health and Ecological Sciences, Ifakara Health Institute, PO Box 53, Ifakara, Tanzania.
| | - Tanya L Russell
- Faculty of Medicine, Health and Molecular Sciences, James Cook University, PO Box 6811, Cairns, Queensland, 4870, Australia.
| | - Heather M Ferguson
- Boyd Orr Centre for Population and Ecosystem Health, Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, G12 8QQ, Glasgow, UK.
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Kawada H, Dida GO, Ohashi K, Kawashima E, Sonye G, Njenga SM, Mwandawiro C, Minakawa N. A small-scale field trial of pyriproxyfen-impregnated bed nets against pyrethroid-resistant Anopheles gambiae s.s. in western Kenya. PLoS One 2014; 9:e111195. [PMID: 25333785 PMCID: PMC4205095 DOI: 10.1371/journal.pone.0111195] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2014] [Accepted: 09/29/2014] [Indexed: 11/19/2022] Open
Abstract
Pyrethroid resistance is becoming a major problem for vector control programs, because at present, there are few suitable chemical substitutes for pyrethroids, as when used on bed nets the insecticide must have low mammalian toxicity as well as high activity to mosquitoes. Pyriproxyfen (PPF) is one of the most active chemicals among the juvenile hormone mimic (JHM) group. Sterilizing mosquitoes by using PPF could be a potential control measure for pyrethroid-resistant malaria vectors. We investigated the sterilizing effects of two types of PPF-impregnated bed nets – a 1% PPF-impregnated net and a 1% PPF +2% permethrin-impregnated net (Olyset Duo) – to pyrethroid-resistant wild population of Anopheles gambiae s.s. in western Kenya. High mortality of blood-fed mosquitos was observed 3 days post-collection, in the houses where PPF-impregnated nets were used, indicating the effect of PPF on the longevity of mosquitos that came in contact with the net. Reduction in the number of ovipositing females, number of eggs, and number of progeny per female were also observed in the houses in which both Olyset Duo and PPF-impregnated nets were used. This is the first field study showing the high sterilizing efficacy of PPF against wild pyrethroid-resistant An. gambiae s.s. population. In addition, we recognized the necessity of combined use of permethrin with PPF, in order to reduce the risk of mosquito bites and provide a level of personal protection. Further studies on wild pyrethroid-resistant mosquito populations such as An. arabiensis and An. funestus s.s. would provide more information on the practical use of the PPF-impregnated bed nets.
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Affiliation(s)
- Hitoshi Kawada
- Department of Vector Ecology and Environment, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
- * E-mail:
| | - Gabriel O. Dida
- Department of Vector Ecology and Environment, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
- School of Public Health, Maseno University, Kisumu, Kenya
| | - Kazunori Ohashi
- Health and Crop Sciences Research Laboratory, Sumitomo Chemical Co. Ltd., Hyogo, Japan
| | - Emiko Kawashima
- Department of Vector Ecology and Environment, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
| | | | - Sammy M. Njenga
- Eastern and Southern Africa Centre of International Parasite Control, Nairobi, Kenya
| | | | - Noboru Minakawa
- Department of Vector Ecology and Environment, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
- The Global Center of Excellence Program, Nagasaki University, Nagasaki, Japan
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