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Koffi AA, Ahoua Alou LP, Djenontin A, Kabran JPK, Dosso Y, Kone A, Moiroux N, Pennetier C. Efficacy of Olyset® Duo, a permethrin and pyriproxyfen mixture net against wild pyrethroid-resistant Anopheles gambiae s.s. from Côte d'Ivoire: an experimental hut trial. ACTA ACUST UNITED AC 2015; 22:28. [PMID: 26489480 PMCID: PMC4613874 DOI: 10.1051/parasite/2015028] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 09/25/2015] [Indexed: 11/24/2022]
Abstract
Pyrethroid resistance in malaria vectors has spread across sub-Saharan Africa. Alternative tools and molecules are urgently needed for effective vector control. One of the most promising strategies to prevent or delay the development of resistance is to use at least two molecules having unrelated modes of action in combination in the same bed net. We evaluated in experimental huts in Côte d’Ivoire, a new polyethylene long-lasting insecticidal net (LN) product, Olyset® Duo, incorporating permethrin (PER) and pyriproxyfen (PPF), an insect growth regulator (IGR). PPF alone or in combination with permethrin had a significant impact on fertility (7–12% reduction relative to control) and no effect on fecundity of wild multi-resistant An. gambiae s.s. These results triggered crucial research questions on the behaviour of targeted mosquitoes around the LN. To maximize the sterilizing effect of PPF in the combination, there would be a need for a trade-off between the necessary contact time of the insect with PPF and the surface content of the pyrethroid insecticide that is bioavailable and induces excito-repellency.
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Affiliation(s)
- Alphonsine A Koffi
- Institut Pierre Richet (IPR), Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | - Ludovic P Ahoua Alou
- Institut Pierre Richet (IPR), Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | - Armel Djenontin
- Institut de Recherche pour le Développement (IRD), Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), UM-CNRS 5290 IRD 224, Cotonou, Benin - Faculté des Sciences et Techniques-Université d'Abomey-Calavi, Cotonou, Benin - Centre de Recherche Entomologique de Cotonou (CREC), Cotonou, Benin
| | - Jean-Paul K Kabran
- Institut Pierre Richet (IPR), Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | - Youssouf Dosso
- Institut Pierre Richet (IPR), Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | - Aboubacar Kone
- Institut Pierre Richet (IPR), Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | | | - Cedric Pennetier
- Institut de Recherche pour le Développement (IRD), Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), UM-CNRS 5290 IRD 224, Cotonou, Benin - Centre de Recherche Entomologique de Cotonou (CREC), Cotonou, Benin
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Kudom AA, Mensah BA, Froeschl G, Rinder H, Boakye D. DDT and pyrethroid resistance status and laboratory evaluation of bio-efficacy of long lasting insecticide treated nets against Culex quinquefasciatus and Culex decens in Ghana. Acta Trop 2015. [PMID: 26215129 DOI: 10.1016/j.actatropica.2015.07.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Nuisance from Culex mosquitoes in Ghana has a serious negative impact on the standard of living in many urban communities. In addition, a perceived lack of efficacy of long lasting insecticide treated nets (LLINs) against nuisance mosquitoes contributes to their discontinued use. This again compromises malaria control, even if Anopheles species themselves would still be susceptible to the insecticides used. Control strategies involve pyrethroid insecticides but information on Culex mosquito susceptibility to these insecticides is limited. A nationwide survey was conducted to address this problem. In adults, susceptibility to permethrin, deltamethrin and DDT as well as enzyme activity and kdr mutation were determined. Cone and tunnel bioassay were also carried out to determine the efficacy of LLINs against the mosquitoes. Culex quinquefasciatus and Culex decens were identified in the study area. Higher deltamethrin and DDT resistance and relatively low permethrin resistance were observed in both species. High enzyme activities and kdr mutations were observed in C. quinquefasciatus but not in C. decens. However, reduced efficacy of LLINs was observed in both mosquito species. This adds up to the evidence of the spread of pyrethroid resistance in mosquitoes and its negative impact on control strategies.
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Affiliation(s)
- Andreas A Kudom
- Center for International Health, Department of Infectious Diseases and Tropical Medicine, Ludwig-Maximilians-Universität Munich, Germany; Department of Entomology and Wildlife, School of Biological Sciences, University of Cape Coast, Ghana.
| | - Ben A Mensah
- Department of Entomology and Wildlife, School of Biological Sciences, University of Cape Coast, Ghana
| | - Guenter Froeschl
- Center for International Health, Department of Infectious Diseases and Tropical Medicine, Ludwig-Maximilians-Universität Munich, Germany
| | - Heinz Rinder
- Center for International Health, Department of Infectious Diseases and Tropical Medicine, Ludwig-Maximilians-Universität Munich, Germany; Bavarian Health and Food Safety Authority (LGL), Oberschleissheim, Germany
| | - Daniel Boakye
- Noguchi Memorial Institute for Medical Research, University of Ghana, Ghana
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Jaffer A, Protopopoff N, Mosha FW, Malone D, Rowland MW, Oxborough RM. Evaluating the sterilizing effect of pyriproxyfen treated mosquito nets against Anopheles gambiae at different blood-feeding intervals. Acta Trop 2015. [PMID: 26200789 DOI: 10.1016/j.actatropica.2015.07.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Pyrethroid resistant malaria vectors are widespread throughout sub-Saharan Africa and new insecticides with different modes of action are urgently needed. Pyriproxyfen is a juvenile hormone mimic that reduces fecundity and fertility of adult Anopheles mosquitoes when used as a contact insecticide. A long-lasting insecticidal net incorporating pyriproxyfen is under development. As wild, host-seeking females may succeed in blood-feeding at different intervals after initial contact with mosquito nets the aim of this study was to determine the effect that age and gonotrophic status (nulliparous or parous) and the interval between initial pyriproxyfen exposure and blood-feeding has in terms of subsequent reduced fecundity and fertility. Anopheles gambiae s.s. were exposed to pyriproxyfen LLIN for three minutes in WHO cone bioassays. Four regimens were tested with different blood-feeding intervals A-1 hour (nulliparous), B-1 hour (parous), C-24h (nulliparous), or D-120h (nulliparous) after pyriproxyfen exposure. Mosquito oviposition rate, fecundity and fertility of eggs were recorded for several days. All four treatment regimens produced levels of mortality similar to unexposed females. The overall reduction in reproductive rate of 99.9% for regimen A relative to the untreated net was primarily due to oviposition inhibition in exposed females (97%). Pyriproxyfen was equally effective against older parous mosquitoes and when blood-feeding was 24h after exposure. Regimen D produced a reduction in reproductive rate of 60.1% but this was of lesser magnitude than other regimens and was the only regimen that failed to reduce fertility of laid eggs, indicating the effects of pyriproxyfen exposure on reproduction are to some extent reversible as mosquitoes age. In an area of moderate to high mosquito net coverage a host-seeking mosquito is likely to contact a treated mosquito net before: (a) penetrating a holed net and blood-feeding shortly after exposure or, (b) be frustrated by intact nets before succeeding in blood-feeding on an unprotected individual the following night. Mosquito nets are an appropriate delivery system for pyriproxyfen, based on the large reductions in reproductive rate when blood-feeding between 1h and 24h after exposure. Combining with a pyrethroid should be an effective approach if susceptible mosquitoes are killed and resistant mosquitoes sterilized.
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Affiliation(s)
- Aneesa Jaffer
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK.
| | - Natacha Protopopoff
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK; Department of Entomology and Parasitology, Kilimanjaro Christian Medical University College, Moshi, Kilimanjaro, Tanzania; Pan-African Malaria Vector Research Consortium, (PAMVERC), Moshi, Tanzania.
| | - Franklin W Mosha
- Department of Entomology and Parasitology, Kilimanjaro Christian Medical University College, Moshi, Kilimanjaro, Tanzania; Pan-African Malaria Vector Research Consortium, (PAMVERC), Moshi, Tanzania.
| | - David Malone
- Innovative Vector Control Consortium (IVCC), Liverpool School of Tropical Medicine, Liverpool, UK.
| | - Mark W Rowland
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK; Pan-African Malaria Vector Research Consortium, (PAMVERC), Moshi, Tanzania.
| | - Richard M Oxborough
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK; Department of Entomology and Parasitology, Kilimanjaro Christian Medical University College, Moshi, Kilimanjaro, Tanzania; Pan-African Malaria Vector Research Consortium, (PAMVERC), Moshi, Tanzania.
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Parker JEA, Angarita-Jaimes N, Abe M, Towers CE, Towers D, McCall PJ. Infrared video tracking of Anopheles gambiae at insecticide-treated bed nets reveals rapid decisive impact after brief localised net contact. Sci Rep 2015; 5:13392. [PMID: 26323965 PMCID: PMC4642575 DOI: 10.1038/srep13392] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 07/24/2015] [Indexed: 11/11/2022] Open
Abstract
Long-lasting insecticidal bed nets (LLINs) protect humans from malaria transmission and are fundamental to malaria control worldwide, but little is known of how mosquitoes interact with nets. Elucidating LLIN mode of action is essential to maintain or improve efficacy, an urgent need as emerging insecticide resistance threatens their future. Tracking multiple free-flying Anopheles gambiae responding to human-occupied bed nets in a novel large-scale system, we characterised key behaviours and events. Four behavioural modes with different levels of net contact were defined: swooping, visiting, bouncing and resting. Approximately 75% of all activity occurred at the bed net roof where multiple brief contacts were focussed above the occupant’s torso. Total flight and net contact times were lower at LLINs than untreated nets but the essential character of the response was unaltered. LLINs did not repel mosquitoes but impacted rapidly: LLIN contact of less than 1 minute per mosquito during the first ten minutes reduced subsequent activity; after thirty minutes, activity at LLINs was negligible. Velocity measurements showed that mosquitoes detected nets, including unbaited untreated nets, prior to contact. This is the most complete characterisation of mosquito-LLIN interactions to date, and reveals many aspects of LLIN mode of action, important for developing the next generation of LLINs.
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Affiliation(s)
- Josephine E A Parker
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
| | - Natalia Angarita-Jaimes
- Optical Engineering Group, School of Engineering, University of Warwick, Coventry, CV4 7AL, UK
| | - Mayumi Abe
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
| | - Catherine E Towers
- Optical Engineering Group, School of Engineering, University of Warwick, Coventry, CV4 7AL, UK
| | - David Towers
- Optical Engineering Group, School of Engineering, University of Warwick, Coventry, CV4 7AL, UK
| | - Philip J McCall
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
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Tiono AB, Pinder M, N'Fale S, Faragher B, Smith T, Silkey M, Ranson H, Lindsay SW. The AvecNet Trial to assess whether addition of pyriproxyfen, an insect juvenile hormone mimic, to long-lasting insecticidal mosquito nets provides additional protection against clinical malaria over current best practice in an area with pyrethroid-resistant vectors in rural Burkina Faso: study protocol for a randomised controlled trial. Trials 2015; 16:113. [PMID: 25873089 PMCID: PMC4377002 DOI: 10.1186/s13063-015-0606-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Accepted: 02/12/2015] [Indexed: 11/17/2022] Open
Abstract
Background Recent reductions in malaria in sub-Saharan Africa have been associated with increased coverage with long-lasting insecticidal nets (LLINs). Pyrethroids are currently the only insecticide class used for treating nets, and the rapid increase in resistance to pyrethroids in vector mosquitoes may jeopardise future vector control. Nets containing a novel combination of permethrin, a pyrethroid, and pyriproxyfen, an insect juvenile hormone mimic, (PPF-LLIN) may enhance malaria control, as well as reducing the spread of pyrethroid-resistant mosquitoes. This trial will determine whether PPF-LLINs provide incremental protection against malaria over current best practice of LLINs and prompt treatment in an area with pyrethroid-resistant vectors. Methods A 2 armed cluster-randomised controlled trial will be conducted in Burkina Faso to assess whether PPF-LLIN (containing 2% permethrin and 1% pyriproxyfen w/w) provide better protection against clinical malaria in children than 2% permethrin-treated LLINs. Study subjects will be recruited and provided with LLINs at the start of the study. The LLINs will be exchanged for PPF-LLIN by cluster in a step-wedge fashion so 3 months before the end of the 2 year trial all participants will have a PPF-LLIN. The primary endpoint will be clinical malaria incidence measured by passive case detection in a cohort of children, aged 6 months to 5 years. Anaemia and parasite prevalence will also be measured in children during cross-sectional surveys. Exposure to malaria parasites will be assessed using light traps followed by identification of common vector species and their sporozoite infection rates. Safety evaluation will include recording of adverse events and pregnancy outcomes. The main endpoint analysis will include adjusting for distance between village clusters with different types of nets, as the impact of PPF-LLIN is likely to increase as larger areas are dominated by PPF-LLIN, reducing the spill over of mosquitoes from villages with LLINs. Discussion The step-wedge design is to measure the impact of an incrementally delivered environmental intervention where we expect the degree of control to be improved as more people use PPF-LLIN over a larger area. Trial findings will help inform policy makers on the effectiveness of PPF-LLIN nets for malaria control in areas of pyrethroid resistance. Trial registration ISRCTN21853394 – AvecNet, registered on 3 April 2013. Electronic supplementary material The online version of this article (doi:10.1186/s13063-015-0606-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Alfred B Tiono
- Centre National de Recherche et de Formation sur le Paludisme (CNRFP), Ouagadougou, Burkina Faso.
| | - Margaret Pinder
- School of Biological Sciences and Biomedicine, Durham University, Durham, UK. .,Medical Research Council Unit The Gambia, P.O. Box 273, Banjul, The Gambia.
| | - Sagnon N'Fale
- Centre National de Recherche et de Formation sur le Paludisme (CNRFP), Ouagadougou, Burkina Faso.
| | | | - Tom Smith
- Swiss Tropical and Public Health Institute, Basle, Switzerland.
| | | | - Hilary Ranson
- Liverpool School of Tropical Medicine, Liverpool, UK.
| | - Steve W Lindsay
- School of Biological Sciences and Biomedicine, Durham University, Durham, UK.
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Koama B, Namountougou M, Sanou R, Ndo S, Ouattara A, Dabiré RK, Malone D, Diabaté A. The sterilizing effect of pyriproxyfen on the malaria vector Anopheles gambiae: physiological impact on ovaries development. Malar J 2015; 14:101. [PMID: 25880844 PMCID: PMC4355148 DOI: 10.1186/s12936-015-0609-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Accepted: 02/09/2015] [Indexed: 12/05/2022] Open
Abstract
Adult females An. gambiae were exposed in 3 min cone test to treated nets with PPF before or after they were blood fed. The effects of PPF on ovaries development, females oviposition and eggs hatching were assessed. Both unfed and fed mosquitoes exposed to PPF exhibited nearly complete inhibition of fecundity (70-100%) and fertility (90-100%). After females have been exposed once to PPF, the sterilizing effect on their fecundity was observed over 3 consecutive blood meals suggesting that PPF might have an irreversible sterilizing effect. Observation of the ovaries of exposed females to PPF under microscope revealed that the ovaries failed to develop even after several blood meals. The combination of PPF to pyrethroids on bednets could provide better malaria control tool and prevent the further development and spread of pyrethroid resistance in malaria vectors.
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Affiliation(s)
- Bayili Koama
- Institut de Recherche en Sciences de la Santé/Centre Muraz, Bobo-Dioulasso, Ouagadougou, Burkina Faso.
| | - Moussa Namountougou
- Institut de Recherche en Sciences de la Santé/Centre Muraz, Bobo-Dioulasso, Ouagadougou, Burkina Faso. .,Universite Polytechnique de Bobo, Bobo-Dioulasso, Ouagadougou, Burkina Faso.
| | - Roger Sanou
- Institut de Recherche en Sciences de la Santé/Centre Muraz, Bobo-Dioulasso, Ouagadougou, Burkina Faso.
| | - Sévérin Ndo
- Institut de Recherche en Sciences de la Santé/Centre Muraz, Bobo-Dioulasso, Ouagadougou, Burkina Faso.
| | - Abdoulaye Ouattara
- Institut de Recherche en Sciences de la Santé/Centre Muraz, Bobo-Dioulasso, Ouagadougou, Burkina Faso.
| | - Roch K Dabiré
- Institut de Recherche en Sciences de la Santé/Centre Muraz, Bobo-Dioulasso, Ouagadougou, Burkina Faso.
| | - David Malone
- Innovative Vector Control Consortium, Liverpool, UK.
| | - Abdoulaye Diabaté
- Institut de Recherche en Sciences de la Santé/Centre Muraz, Bobo-Dioulasso, Ouagadougou, Burkina Faso.
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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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Benefit of insecticide-treated nets, curtains and screening on vector borne diseases, excluding malaria: a systematic review and meta-analysis. PLoS Negl Trop Dis 2014; 8:e3228. [PMID: 25299481 PMCID: PMC4191944 DOI: 10.1371/journal.pntd.0003228] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 08/28/2014] [Indexed: 11/19/2022] Open
Abstract
Introduction Insecticide-treated nets (ITNs) are one of the main interventions used for malaria control. However, these nets may also be effective against other vector borne diseases (VBDs). We conducted a systematic review and meta-analysis to estimate the efficacy of ITNs, insecticide-treated curtains (ITCs) and insecticide-treated house screening (ITS) against Chagas disease, cutaneous and visceral leishmaniasis, dengue, human African trypanosomiasis, Japanese encephalitis, lymphatic filariasis and onchocerciasis. Methods MEDLINE, EMBASE, LILACS and Tropical Disease Bulletin databases were searched using intervention, vector- and disease-specific search terms. Cluster or individually randomised controlled trials, non-randomised trials with pre- and post-intervention data and rotational design studies were included. Analysis assessed the efficacy of ITNs, ITCs or ITS versus no intervention. Meta-analysis of clinical data was performed and percentage reduction in vector density calculated. Results Twenty-one studies were identified which met the inclusion criteria. Meta-analysis of clinical data could only be performed for four cutaneous leishmaniasis studies which together showed a protective efficacy of ITNs of 77% (95%CI: 39%–91%). Studies of ITC and ITS against cutaneous leishmaniasis also reported significant reductions in disease incidence. Single studies reported a high protective efficacy of ITS against dengue and ITNs against Japanese encephalitis. No studies of Chagas disease, human African trypanosomiasis or onchocerciasis were identified. Conclusion There are likely to be considerable collateral benefits of ITN roll out on cutaneous leishmaniasis where this disease is co-endemic with malaria. Due to the low number of studies identified, issues with reporting of entomological outcomes, and few studies reporting clinical outcomes, it is difficult to make strong conclusions on the effect of ITNs, ITCs or ITS on other VBDs and therefore further studies be conducted. Nonetheless, it is clear that insecticide-treated materials such as ITNs have the potential to reduce pathogen transmission and morbidity from VBDs where vectors enter houses. Malaria is a deadly disease caused by a parasite which is transmitted by anopheline mosquitoes. Bednets treated with insecticide are one of the key tools used to prevent malaria and they have been distributed on a large scale in many countries, particularly in Africa. It may be possible to control other diseases transmitted by insects using insecticide-treated bednets because many of these insects also enter houses. We did a review of studies looking at the effectiveness of insecticide-treated bednets, curtains and house screening against nine major diseases transmitted by insects. We assessed the effect these tools had on reducing numbers of the insects and disease in humans. Insecticide-treated bednets were found to be effective in preventing cutaneous leishmaniasis—a disease transmitted by sandflies—and insecticide-treated curtains and screening showed potential in preventing other insect borne diseases. Although further studies are required, it is clear that insecticide-treated bednets, curtains and screening have the potential to prevent transmission of insect-transmitted diseases.
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Mbare O, Lindsay SW, Fillinger U. Pyriproxyfen for mosquito control: female sterilization or horizontal transfer to oviposition substrates by Anopheles gambiae sensu stricto and Culex quinquefasciatus. Parasit Vectors 2014; 7:280. [PMID: 24954695 PMCID: PMC4082483 DOI: 10.1186/1756-3305-7-280] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 06/16/2014] [Indexed: 11/10/2022] Open
Abstract
Background The use of gravid mosquitoes as vehicles to auto-disseminate larvicides was recently demonstrated for the transfer of pyriproxyfen (PPF) by container-breeding Aedes mosquitoes and presents an appealing idea to explore for other disease vectors. The success of this approach depends on the female’s behaviour, the time of exposure and the amount of PPF that can be carried by an individual. We explore the effect of PPF exposure at seven time points around blood feeding on individual Anopheles gambiae sensu stricto and Culex quinquefasciatus fecundity and ability to transfer in laboratory assays. Method Mosquitoes were exposed to 2.6 mg PPF per m2 at 48, 24 and 0.5 hours before and after a blood meal and on the day of egg-laying. The proportion of exposed females (N = 80-100) laying eggs, the number of eggs laid and hatched was studied. Transfer of PPF to oviposition cups was assessed by introducing 10 late instar insectary-reared An. gambiae s.s. larvae into all the cups and monitored for adult emergence inhibition. Results Exposure to PPF between 24 hours before and after a blood meal had significant sterilizing effects: females of both species were 6 times less likely (Odds ratio (OR) 0.16, 95% confidence interval (CI) 0.10-0.26) to lay eggs than unexposed females. Of the few eggs laid, the odds of an egg hatching was reduced 17 times (OR 0.06, 95% CI 0.04-0.08) in Anopheles but only 1.2 times (OR 0.82, 95% CI 0.73-0.93) in Culex. Adult emergence inhibition from larvae introduced in the oviposition cups was observed only from cups in which eggs were laid. When females were exposed to PPF close to egg laying they transferred enough PPF to reduce emergence by 65-71% (95% CI 62-74%). Conclusion PPF exposure within a day before and after blood feeding affects egg-development in An. gambiae s.s. and Cx. quinquefasciatus and presents a promising opportunity for integrated control of vectors and nuisance mosquitoes. However, sterilized females are unlikely to visit an oviposition site and therefore do not transfer lethal concentrations of PPF to aquatic habitats. This suggests that for successful auto-dissemination the optimum contamination time is close to oviposition.
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Affiliation(s)
| | | | - Ulrike Fillinger
- International Centre of Insect Physiology and Ecology (icipe), Thomas Odhiambo Campus, 40305 Mbita, Kenya.
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