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Gichuki PM, Kibe L, Mwatele C, Mwangangi J, Mbogo CM. Towards an integrated vector management approach for sustainable control of schistosomiasis and malaria in Mwea, Kirinyaga County, Kenya: Baseline epidemiological and vector results. Heliyon 2023; 9:e20966. [PMID: 37876477 PMCID: PMC10590948 DOI: 10.1016/j.heliyon.2023.e20966] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 10/12/2023] [Accepted: 10/12/2023] [Indexed: 10/26/2023] Open
Abstract
Background Vector control is an important approach in the control of most parasitic and vector-borne diseases including malaria, and schistosomiasis. Distribution of these two infections often overlaps and in such areas it's more economically viable to employ an integrated approach in the control of their vectors which largely shares the same breeding ecosystem. We carried out a baseline epidemiological and vector surveys for malaria and schistosomiasis in Mwea, Kirinyaga County, in preparation for the upscaling of integrated vector management (IVM) for the two diseases. Methods This was a repeated cross sectional survey, where mosquito and snails were sampled during dry and wet seasons in three different ecological zones, Kiamaciri, Thiba and Murinduko to identify possible breeding sites. Mosquito larvae were collected using standard dippers, adults using CDC miniature light traps while snail vectors were sampled using standard snail scoops in different breeding habitats. A total of 1200 pupils from 12 primary schools were tested for malaria using rapid diagnostic tests (Malaria Pf/PAN Ag combo). Stool samples were processed using the Kato Katz technique for intestinal schistosomiasis. Results The overall prevalence of intestinal schistosomiasis was 9.08 % (95 % CI: 07.00-11.00), with Kiamaciri zone recording the highest prevalence at 19 % (95%CI: 15.00-23.00) and Murinduko zone the least at 0.17 % (95%CI: 0.00-0.01). Majority of the infections were of light intensity 78.9 % (95%CI: 70.04-86.13). There was no positive malaria case detected in this study. Of the 3208 adult mosquitoes sampled during the dry season, 20.6 % (95 % CI: 19.25-22.08) were Anopheles gambiae s.l while 79.4 % (95 % CI: 77.92-80.75) were culicines. During the wet season, 3378 adult mosquitoes were collected, of which 14.7 % (95 % CI: 13.56-15.98) were Anopheles gambiae s.l and 85.3 % (95 % CI: 84.02-86.44) culicines. Overall, 4085 mosquito larvae were collected during the two seasons, of which, 57.3 % and 42.7 % were anopheles and culicine respectively. Majority of the larvae (85.1 % (95%CI: 84.01-86.10) were collected during the wet season, with only 14.9 % (95%CI: 14.10-16.00) being collected during the dry season. A total of 2292 fresh water vector snails were collected with a majority (69.6 % (95%CI: 68.00-71.10) being Biomphalaria pffeiferi responsible for transmission of intestinal schistosomiasis. Conclusion This study demonstrates that intestinal schistosomiasis is prevalent in Kiamaciri and Thiba zones, and points to the possibility of active transmission of schistosomiasis in Murinduko zone. Malaria vectors were predominantly observed in all sites despite there being no malaria positive case. Culex quinquefaciatus responsible for the spread of several arboviruses was also observed. The presence of these vectors may lead to future disease outbreaks in the area if concerted control initiatives are not undertaken. The disease vectors shared the same breeding sites and thus its economical and feasible to adopt an integrated vector management approach in control efforts for these disease in the study area.
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Affiliation(s)
- Paul M. Gichuki
- Kenya Medical Research Institute (KEMRI), Eastern & Southern Africa Centre of International Parasite Control (ESACIPAC), Nairobi, P.O BOX 54840-00200 Nairobi, Kenya
- School of Health Sciences, Meru University of Science and Technology, P.O BOX 972-60200 Meru, Kenya
| | - Lydia Kibe
- Kenya Medical Research Institute (KEMRI), Eastern & Southern Africa Centre of International Parasite Control (ESACIPAC), Nairobi, P.O BOX 54840-00200 Nairobi, Kenya
| | - Cassian Mwatele
- Kenya Medical Research Institute (KEMRI), Eastern & Southern Africa Centre of International Parasite Control (ESACIPAC), Nairobi, P.O BOX 54840-00200 Nairobi, Kenya
| | - Joseph Mwangangi
- KEMRI-Wellcome Trust Research Programme, Public Health Unit, PO Box 43640 - 00100, Nairobi, Kenya
- Kenya Medical Research Institute (KEMRI), Centre for Geographical Medicine Research-Coast (CGMR-C). P.O Box 230- 80108 Kilifi, Kenya
| | - Charles M. Mbogo
- Kenya Medical Research Institute (KEMRI), Eastern & Southern Africa Centre of International Parasite Control (ESACIPAC), Nairobi, P.O BOX 54840-00200 Nairobi, Kenya
- KEMRI-Wellcome Trust Research Programme, Public Health Unit, PO Box 43640 - 00100, Nairobi, Kenya
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Brake S, Gomez-Maldonado D, Hummel M, Zohdy S, Peresin MS. Understanding the current state-of-the-art of long-lasting insecticide nets and potential for sustainable alternatives. CURRENT RESEARCH IN PARASITOLOGY & VECTOR-BORNE DISEASES 2022; 2:100101. [PMID: 36248356 PMCID: PMC9562956 DOI: 10.1016/j.crpvbd.2022.100101] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Revised: 09/13/2022] [Accepted: 09/14/2022] [Indexed: 11/23/2022]
Abstract
Long-lasting insecticide-treated nets (LLINs) are widely distributed to communities where malaria is a major cause of mortality, especially to those under the age of 5 years-old. To protect people from this illness, LLINs provide physical and chemical barriers by containing insecticides within the matrix of the polymer fibers or on the surface. Synthetic polymers including polyethylene and polyester are common material choices for these nets, and pyrethroids, along with other additives, are the insecticides of choice for this application. Many studies have shown the effectiveness of these nets on the impact of malaria is highly significant, but there is a demand for more durable nets that last longer than only a few years as the available products are rated for 2–3 years of use. Improvements in this area would increase cost effectiveness, because better durability would reduce the frequency of manufacturing and worldwide shipping. Additionally, due to the plastic fibers, the waste can build quickly, damaging the environment. To deal with the sustainability and durability issues, biodegradable and renewable materials should be chosen as an alternative. LLINs are important for malaria control, but they require a sustainable and durable alternative to synthetic polymers. LLINs are made by extrusion of pyrethroids and synthetic polymers or by coating. The current LLINs include important active ingredients to improve insecticidal activity. Bio-based polymers have the potential to be used to develop a superior LLIN to those available currently.
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Lees RS, Armistead JS, Azizi S, Constant E, Fornadel C, Gimnig JE, Hemingway J, Impoinvil D, Irish SR, Kisinza W, Lissenden N, Mawejje HD, Messenger LA, Moore S, Ngufor C, Oxborough R, Protopopoff N, Ranson H, Small G, Wagman J, Weetman D, Zohdy S, Spiers A. Strain Characterisation for Measuring Bioefficacy of ITNs Treated with Two Active Ingredients (Dual-AI ITNs): Developing a Robust Protocol by Building Consensus. INSECTS 2022; 13:434. [PMID: 35621770 PMCID: PMC9144861 DOI: 10.3390/insects13050434] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 04/21/2022] [Accepted: 04/22/2022] [Indexed: 02/04/2023]
Abstract
Durability monitoring of insecticide-treated nets (ITNs) containing a pyrethroid in combination with a second active ingredient (AI) must be adapted so that the insecticidal bioefficacy of each AI can be monitored independently. An effective way to do this is to measure rapid knock down of a pyrethroid-susceptible strain of mosquitoes to assess the bioefficacy of the pyrethroid component and to use a pyrethroid-resistant strain to measure the bioefficacy of the second ingredient. To allow robust comparison of results across tests within and between test facilities, and over time, protocols for bioefficacy testing must include either characterisation of the resistant strain, standardisation of the mosquitoes used for bioassays, or a combination of the two. Through a series of virtual meetings, key stakeholders and practitioners explored different approaches to achieving these goals. Via an iterative process we decided on the preferred approach and produced a protocol consisting of characterising mosquitoes used for bioefficacy testing before and after a round of bioassays, for example at each time point in a durability monitoring study. We present the final protocol and justify our approach to establishing a standard methodology for durability monitoring of ITNs containing pyrethroid and a second AI.
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Affiliation(s)
- Rosemary S. Lees
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK; (J.H.); (N.L.); (H.R.); (D.W.)
- Innovation to Impact, Pembroke Place, Liverpool L3 5QA, UK;
| | - Jennifer S. Armistead
- U.S. President’s Malaria Initiative (PMI), U.S. Agency for International Development (USAID), Washington, DC 20547, USA;
| | - Salum Azizi
- KCMUCo-PAMVERC Test Facility, Department of Medical Parasitology and Entomology, Kilimanjaro Christian Medical University College, Moshi P.O. Box 2240, Tanzania;
| | - Edi Constant
- Centre Suisse de Recherches Scientifiques (CSRS), Abidjan 1303, Côte d’Ivoire;
| | - Christen Fornadel
- Innovative Vector Control Consortium (IVCC), Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK; (C.F.); (G.S.)
| | - John E. Gimnig
- Division of Parasitic Diseases and Malaria, Centers for Disease Control (CDC) and Prevention, Atlanta, GA 30329, USA; (J.E.G.); (D.I.); (S.Z.)
| | - Janet Hemingway
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK; (J.H.); (N.L.); (H.R.); (D.W.)
| | - Daniel Impoinvil
- Division of Parasitic Diseases and Malaria, Centers for Disease Control (CDC) and Prevention, Atlanta, GA 30329, USA; (J.E.G.); (D.I.); (S.Z.)
- U.S. President’s Malaria Initiative (PMI), Centers for Disease Control (CDC) and Prevention, Atlanta, GA 30329, USA;
| | - Seth R. Irish
- U.S. President’s Malaria Initiative (PMI), Centers for Disease Control (CDC) and Prevention, Atlanta, GA 30329, USA;
| | - William Kisinza
- Amani Research Centre, National Institute for Medical Research, Muheza P.O. Box 81, Tanzania;
| | - Natalie Lissenden
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK; (J.H.); (N.L.); (H.R.); (D.W.)
- Innovation to Impact, Pembroke Place, Liverpool L3 5QA, UK;
| | - Henry D. Mawejje
- Infectious Diseases Research Collaboration (IDRC), Plot 2C Nakasero Hill Road, Kampala P.O. Box 7475, Uganda;
| | - Louisa A. Messenger
- Department of Disease Control, Faculty of Infectious Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK; (L.A.M.); (C.N.); (N.P.)
| | - Sarah Moore
- Vector Control Product Testing Unit (VCPTU), Environmental Health and Ecological Science Department, Ifakara Health Institute, Bagamoyo P.O. Box 74, Tanzania;
- Vector Biology Unit, Department of Epidemiology and Public Health, Swiss Tropical & Public Health Institute, Kreuzstrasse 2, Allschwil, 4123 Basel, Switzerland
- Faculty of Science, University of Basel, Petersplatz 1, 4001 Basel, Switzerland
- Nelson Mandela African Institute of Science and Technology (NM-AIST), Tengeru P.O. Box 447, Tanzania
| | - Corine Ngufor
- Department of Disease Control, Faculty of Infectious Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK; (L.A.M.); (C.N.); (N.P.)
- Centre de Recherche Entomologique de Cotonou, Cotonou BP 2604, Benin
| | - Richard Oxborough
- PMI VectorLink Project, Abt Associates, 6130 Executive Blvd., Rockville, MD 20852, USA;
| | - Natacha Protopopoff
- Department of Disease Control, Faculty of Infectious Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK; (L.A.M.); (C.N.); (N.P.)
| | - Hilary Ranson
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK; (J.H.); (N.L.); (H.R.); (D.W.)
| | - Graham Small
- Innovative Vector Control Consortium (IVCC), Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK; (C.F.); (G.S.)
| | - Joseph Wagman
- Malaria and Neglected Tropical Diseases Program, PATH, Washington, DC 20001, USA;
| | - David Weetman
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK; (J.H.); (N.L.); (H.R.); (D.W.)
| | - Sarah Zohdy
- Division of Parasitic Diseases and Malaria, Centers for Disease Control (CDC) and Prevention, Atlanta, GA 30329, USA; (J.E.G.); (D.I.); (S.Z.)
- U.S. President’s Malaria Initiative (PMI), Centers for Disease Control (CDC) and Prevention, Atlanta, GA 30329, USA;
| | - Angus Spiers
- Innovation to Impact, Pembroke Place, Liverpool L3 5QA, UK;
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Multerer L, Vanobberghen F, Glass TR, Hiscox A, Lindsay SW, Takken W, Tiono A, Smith T. Estimating intervention effectiveness in trials of malaria interventions with contamination. Malar J 2021; 20:413. [PMID: 34670558 PMCID: PMC8527711 DOI: 10.1186/s12936-021-03924-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Accepted: 09/21/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In cluster randomized trials (CRTs) or stepped wedge cluster randomized trials (SWCRTs) of malaria interventions, mosquito movement leads to contamination between trial arms unless buffer zones separate the clusters. Contamination can be accounted for in the analysis, yielding an estimate of the contamination range, the distance over which contamination measurably biases the effectiveness. METHODS A previously described analysis for CRTs is extended to SWCRTs and estimates of effectiveness are provided as a function of intervention coverage. The methods are applied to two SWCRTs of malaria interventions, the SolarMal trial on the impact of mass trapping of mosquitoes with odor-baited traps and the AvecNet trial on the effect of adding pyriproxyfen to long-lasting insecticidal nets. RESULTS For the SolarMal trial, the contamination range was estimated to be 146 m ([Formula: see text] credible interval [Formula: see text] km), together with a [Formula: see text] ([Formula: see text] credible interval [Formula: see text]) reduction of Plasmodium infection, compared to the [Formula: see text] reduction estimated without accounting for contamination. The estimated effectiveness had an approximately linear relationship with coverage. For the AvecNet trial, estimated contamination effects were minimal, with insufficient data from the cluster boundary regions to estimate the effectiveness as a function of coverage. CONCLUSIONS The contamination range in these trials of malaria interventions is much less than the distances Anopheles mosquitoes can fly. An appropriate analysis makes buffer zones unnecessary, enabling the design of more cost-efficient trials. Estimation of the contamination range requires information from the cluster boundary regions and trials should be designed to collect this.
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Affiliation(s)
- Lea Multerer
- Swiss Tropical and Public Health Institute, Basel, Switzerland. .,University of Basel, Basel, Switzerland.
| | - Fiona Vanobberghen
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Tracy R Glass
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Alexandra Hiscox
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands.,ARCTEC, London School of Hygiene and Tropical Medicine, London, UK
| | | | - Willem Takken
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Alfred Tiono
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Thomas Smith
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
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Grisales N, Lees RS, Maas J, Morgan JC, Wangrawa DW, Guelbeogo WM, N'Fale S, Lindsay SW, McCall PJ, Ranson H. Pyriproxyfen-treated bed nets reduce reproductive fitness and longevity of pyrethroid-resistant Anopheles gambiae under laboratory and field conditions. Malar J 2021; 20:273. [PMID: 34158066 PMCID: PMC8218427 DOI: 10.1186/s12936-021-03794-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 05/30/2021] [Indexed: 11/21/2022] Open
Abstract
Background The efficacy of insecticide-treated nets (ITNs) containing the insect growth regulator pyriproxyfen (PPF) and pyrethroid insecticides (PPF-ITNs) is being assessed in clinical trials to determine whether they provide greater protection from malaria than standard pyrethroid-treated ITNs in areas where mosquitoes are resistant to pyrethroids. Understanding the entomological mode of action of this new ITN class will aide interpretation of the results from these trials. Methods Anopheles gambiae sensu lato (s.l.) mosquitoes from a susceptible laboratory strain were exposed to PPF-treated netting 24 h, 6 h, and immediately prior to, or 24 h post blood feeding, and the impact on fecundity, fertility and longevity recorded. Pyrethroid-resistant populations were exposed to nets containing permethrin and PPF (PPF-ITNs) in cone bioassays and daily mortality recorded. Mosquitoes were also collected from inside houses pre- and post-distribution of PPF-ITNs in a clinical trial conduced in Burkina Faso; female An. gambiae s.l. were then assessed for fecundity and fertility. Results PPF exposure reduced the median adult lifespan of insecticide-susceptible mosquitoes by 4 to 5 days in all exposure times (p < 0.05) other than 6 h pre-blood meal and resulted in almost complete lifelong sterilization. The longevity of pyrethroid-resistant mosquitoes was also reduced by at least 5 days after exposure to PPF-ITNs compared to untreated nets, but was unaffected by exposure to standard pyrethroid only ITNs. A total of 386 blood-fed or gravid An. gambiae s.l. females were collected from five villages between 1 and 12 months before distribution of PPF-ITNs. Of these mosquitoes, 75% laid eggs and the remaining 25% appeared to have normal ovaries upon dissection. In contrast, only 8.6% of the 631 blood-fed or gravid An. gambiae s.l. collected post PPF-ITN distribution successfully oviposited; 276 (43.7%) did not oviposit but had apparently normal ovaries upon dissection, and 301 (47.7%) did not oviposit and had abnormal eggs upon dissection. Egg numbers were also significantly lower (average of 138/female prior distribution vs 85 post distribution, p < 0.05). Conclusion Exposure to a mixture of PPF and pyrethroids on netting shortens the lifespan of mosquitoes and reduces reproductive output. Sterilization of vectors lasted at least one year under operational conditions. These findings suggest a longer effective lifespan of PPF-pyrethroid nets than reported previously. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-021-03794-z.
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Affiliation(s)
- Nelson Grisales
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK.,World Mosquito Programme, Action On Poverty, Level 4, President Place, No. 93 Nguyen Du Street, District 1, Ho Chi Minh City, Vietnam
| | - Rosemary S Lees
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - James Maas
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - John C Morgan
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Dimitri W Wangrawa
- Centre National de Recherche Et de Formation Sur Le Paludisme (CNRFP), Rue 1847 Avenue Kunda Yonré, 01 BP 2208, Ouagadougou, Burkina Faso
| | - Wamdaogo M Guelbeogo
- Centre National de Recherche Et de Formation Sur Le Paludisme (CNRFP), Rue 1847 Avenue Kunda Yonré, 01 BP 2208, Ouagadougou, Burkina Faso
| | - Sagnon N'Fale
- Centre National de Recherche Et de Formation Sur Le Paludisme (CNRFP), Rue 1847 Avenue Kunda Yonré, 01 BP 2208, Ouagadougou, Burkina Faso
| | - Steven W Lindsay
- Department of Biosciences, Durham University, Durham, DH1 3LE, UK
| | - Philip J McCall
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Hilary Ranson
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK.
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Parthasarathy R, Palli SR. Stage-specific action of juvenile hormone analogs. JOURNAL OF PESTICIDE SCIENCE 2021; 46:16-22. [PMID: 33746542 PMCID: PMC7953018 DOI: 10.1584/jpestics.d20-084] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 01/08/2021] [Indexed: 06/12/2023]
Abstract
The discovery of juvenile hormones (JH) and their synthetic analogs (JHA) generated excitement and hope that these compounds will replace first- and second-generation insecticides that have not so desirable environmental and human safety profiles. However, JHAs used commercially during the past four decades did not meet these expectations. The recent availability of advanced molecular and histological methods and the discovery of key players involved in JH action provided some insights into the functioning of JHA in a stage and species-specific manner. In this review, we will summarize recent findings and stage-specific action of JHA, focusing on three commercially used JHA, methoprene, hydroprene and pyriproxyfen and economically important pests, the red flour beetle, Tribolium castaneum, and the tobacco budworm, Heliothis virescens, and disease vector, the yellow fever mosquito, Aedes aegypti.
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Affiliation(s)
- Ramaseshadri Parthasarathy
- Department of Entomology, University of Kentucky, College of Agriculture, Food and Environment, Lexington, KY, USA
| | - Subba Reddy Palli
- Department of Entomology, University of Kentucky, College of Agriculture, Food and Environment, Lexington, KY, USA
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Yunta C, Hemmings K, Stevenson B, Koekemoer LL, Matambo T, Pignatelli P, Voice M, Nász S, Paine MJI. Cross-resistance profiles of malaria mosquito P450s associated with pyrethroid resistance against WHO insecticides. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2019; 161:61-67. [PMID: 31685198 DOI: 10.1016/j.pestbp.2019.06.007] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 05/20/2019] [Accepted: 06/11/2019] [Indexed: 06/10/2023]
Abstract
Extensive use of pyrethroids for malaria control in Africa has led to widespread pyrethroid resistance in the two major African vectors of malaria An. gambiae and An. funestus. This is often associated with constitutively elevated levels of cytochrome P450s involved with pyrethroid metabolism and detoxification. P450s have the capacity to metabolise diverse substrates, which raises concerns about their potential to cause cross-resistance. A bank of seven recombinant P450s from An. gambiae (CYPs 6M2, 6P2, 6P3, 6P4, 6P5, 9J5) and An. funestus (CYP6P9a) commonly associated with pyrethroid resistance were screened against twelve insecticides representing the five major classes of insecticides recommended by WHO for malaria control; permethrin, etofenprox and bifenthrin (type I pyrethroids), deltamethrin, lambda cyhalothrin and cypermethrin (type II pyrethroids), DDT (organochlorine), bendiocarb (carbamate), malathion, pirimiphos methyl and fenitrothion (organophosphates) and pyriproxyfen (juvenile hormone analogue). DDT was not metabolised by the P450 panel, while bendiocarb was only metabolised by CYP6P3. Pyrethroids and pyriproxyfen were largely susceptible to metabolism by the P450 panel, as were organophosphates, which are activated by P450s. Primiphos-methyl is increasingly used for malaria control. Examination of the pirimiphos-methyl metabolites generated by CYP6P3 revealed both the active pirimiphos-methyl-oxon form and the inactive oxidative cleavage product 2-diethylamino-6-hydroxy-4-methylpyrimidine. The inhibition profile of CYPs 6M2, 6P2, 6P3, 6P9a and 9J5 was also examined using diethoxyfluorescein (DEF) as the probe substrate. Bendiocarb was the weakest inhibitor with IC50 > 100 μM across the P450 panel, while CYP6M2 showed strongest inhibition by malathion (IC50 0.7 μM). The results suggest that P450s present at elevated levels in two major Anopheline vectors of malaria in Africa have the capacity to metabolise a diverse range of pyrethroid and organophosphate insecticides as well as pyriproxyfen that could impact vector control.
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Affiliation(s)
- Cristina Yunta
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
| | - Kay Hemmings
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
| | - Bradley Stevenson
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
| | - Lizette L Koekemoer
- Wits Research Institute for Malaria, MRC Collaborating Centre for Multidisciplinary Research on Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand and the Centre for Emerging, Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg, South Africa
| | - Tonderi Matambo
- Wits Research Institute for Malaria, MRC Collaborating Centre for Multidisciplinary Research on Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand and the Centre for Emerging, Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg, South Africa
| | | | | | - Szilárd Nász
- Syngenta, Product Metabolism and Analytical Sciences, Jealott's Hill International Research Centre, Bracknell RG42 6EY, UK
| | - Mark J I Paine
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK.
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Khemrattrakool P, Yanola J, Lumjuan N, Somboon P. Pyriproxyfen-Treated Polypropylene Sheets and Resting Boxes for Controlling Mosquitoes in Livestock Operations. INSECTS 2019; 10:E55. [PMID: 30781681 PMCID: PMC6410238 DOI: 10.3390/insects10020055] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 02/13/2019] [Accepted: 02/14/2019] [Indexed: 01/21/2023]
Abstract
Many insect vector species of medical and veterinary importance are found abundantly in areas where animals are held. In these areas, they often rest for a period of time on objects around the animals both before and after blood feeding. However, the use of neurotoxic insecticides for vector control is not advised for use in such shelters as these chemicals can pose hazards to animals. The present study evaluated the efficacy of pyriproxyfen (PPF), an insect growth regulator, applied to polypropylene sheets and resting boxes on the reproductivity of mosquitoes found in animal shelters in Chiang Mai, Thailand. The sheets sprayed with 666 mg PPF/m² were set on the inner wall of a cowshed and kept in place for 3 h (6.00 to 9.00 pm). During this time, fully blood-fed female mosquitoes that landed and remained continuously on the sheets for 5, 10, and 20 min were collected. The results, involving Anopheles subpictus, An. vagus, Culex gelidus, Cx. tritaeniorhynchus, and Cx. vishnui, revealed significant reductions in oviposition rates, egg hatchability, pupation, and adult emergence in the PPF-treated groups compared to the control groups. Adult emergence rates were reduced to 85.6⁻94.9% and 95.5⁻100% in those exposed for 10 and 20 min, respectively. The sheets retained their effectiveness for three months. The PPF-treated (666 mg/m²) resting boxes (35 × 35 × 55 cm) were placed overnight at a chicken farm where Cx. quinquefasciatus predominated. Blood-fed mosquitoes were collected in the morning and reared in the laboratory. Oviposition rates were reduced by 71.7% and adult emergence was reduced by 97.8% compared to the controls. PPF residual spray on surface materials in animal sheds is a potential method for controlling mosquitoes. Further studies are needed to evaluate the impact of PPF-treated materials on wild populations.
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Affiliation(s)
- Pattarapon Khemrattrakool
- Center of Insect Vector Study, Department of Parasitology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand.
- Graduate PhD's Degree Program in Parasitology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand.
| | - Jintana Yanola
- Department of Medical Technology, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand.
| | - Nongkran Lumjuan
- Research Institute for Health Sciences, Chiang Mai University, Chiang Mai 50200, Thailand.
| | - Pradya Somboon
- Center of Insect Vector Study, Department of Parasitology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand.
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9
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Shaw WR, Catteruccia F. Vector biology meets disease control: using basic research to fight vector-borne diseases. Nat Microbiol 2018; 4:20-34. [PMID: 30150735 DOI: 10.1038/s41564-018-0214-7] [Citation(s) in RCA: 144] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 06/29/2018] [Indexed: 12/11/2022]
Abstract
Human pathogens that are transmitted by insects are a global problem, particularly those vectored by mosquitoes; for example, malaria parasites transmitted by Anopheles species, and viruses such as dengue, Zika and chikungunya that are carried by Aedes mosquitoes. Over the past 15 years, the prevalence of malaria has been substantially reduced and virus outbreaks have been contained by controlling mosquito vectors using insecticide-based approaches. However, disease control is now threatened by alarming rates of insecticide resistance in insect populations, prompting the need to develop a new generation of specific strategies that can reduce vector-mediated transmission. Here, we review how increased knowledge in insect biology and insect-pathogen interactions is stimulating new concepts and tools for vector control. We focus on strategies that either interfere with the development of pathogens within their vectors or directly impact insect survival, including enhancement of vector-mediated immune control, manipulation of the insect microbiome, or use of powerful new genetic tools such as CRISPR-Cas systems to edit vector genomes. Finally, we offer a perspective on the implementation hurdles as well as the knowledge gaps that must be filled in the coming years to safely realize the potential of these novel strategies to eliminate the scourge of vector-borne disease.
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Affiliation(s)
- W Robert Shaw
- Harvard T. H. Chan School of Public Health, Department of Immunology and Infectious Diseases, Boston, MA, USA.
| | - Flaminia Catteruccia
- Harvard T. H. Chan School of Public Health, Department of Immunology and Infectious Diseases, Boston, MA, USA.
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10
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Tiono AB, Ouédraogo A, Ouattara D, Bougouma EC, Coulibaly S, Diarra A, Faragher B, Guelbeogo MW, Grisales N, Ouédraogo IN, Ouédraogo ZA, Pinder M, Sanon S, Smith T, Vanobberghen F, Sagnon N, Ranson H, Lindsay SW. Efficacy of Olyset Duo, a bednet containing pyriproxyfen and permethrin, versus a permethrin-only net against clinical malaria in an area with highly pyrethroid-resistant vectors in rural Burkina Faso: a cluster-randomised controlled trial. Lancet 2018; 392:569-580. [PMID: 30104047 DOI: 10.1016/s0140-6736(18)31711-2] [Citation(s) in RCA: 77] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 07/16/2018] [Accepted: 07/19/2018] [Indexed: 11/17/2022]
Abstract
BACKGROUND Substantial reductions in malaria incidence in sub-Saharan Africa have been achieved with massive deployment of long-lasting insecticidal nets (LLINs), but pyrethroid resistance threatens control. Burkina Faso is an area with intense malaria transmission and highly pyrethroid-resistant vectors. We assessed the effectiveness of bednets containing permethrin, a pyrethroid, and pyriproxyfen, an insect growth regulator, versus permethrin-only (standard) LLINs against clinical malaria in children younger than 5 years in Banfora, Burkina Faso. METHODS In this two-group, step-wedge, cluster-randomised, controlled, superiority trial, standard LLINs were incrementally replaced with LLINs treated with permethrin plus pyriproxyfen (PPF) in 40 rural clusters in Burkina Faso. In each cluster, 50 children (aged 6 months to 5 years) were followed up by passive case detection for clinical malaria. Cross-sectional surveys were done at the start and the end of the transmission seasons in 2014 and 2015. We did monthly collections from indoor light traps to estimate vector densities. Primary endpoints were the incidence of clinical malaria, measured by passive case detection, and the entomological inoculation rate. Analyses were adjusted for clustering and for month and health centre. This trial is registered as ISRCTN21853394. FINDINGS 1980 children were enrolled in the cohort in 2014 and 2157 in 2015. At the end of the study, more than 99% of children slept under a bednet. The incidence of clinical malaria was 2·0 episodes per child-year in the standard LLIN group and 1·5 episodes per child-year in the PPF-treated LLIN group (incidence rate ratio 0·88 [95% CI 0·77-0·99; p=0·04]). The entomological inoculation rate was 85 (95% CI 63-108) infective bites per transmission season in the standard LLIN group versus 42 (32-52) infective bites per transmission season in the PPF-treated LLIN group (rate ratio 0·49, 95% CI 0·32-0·66; p<0·0001). INTERPRETATION PPF-treated LLINs provide greater protection against clinical malaria than do standard LLINs and could be used as an alternative to standard LLINs in areas with intense transmission of Plasmodium falciparum malaria and highly pyrethroid-resistant vectors. FUNDING EU Seventh Framework Programme.
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Affiliation(s)
- Alfred B Tiono
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Alphonse Ouédraogo
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Daouda Ouattara
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Edith C Bougouma
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Sam Coulibaly
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Amidou Diarra
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | | | - Moussa W Guelbeogo
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | | | - Issa N Ouédraogo
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | | | | | - Souleymane Sanon
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Tom Smith
- Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland
| | - Fiona Vanobberghen
- Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland
| | - N'Fale Sagnon
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Hilary Ranson
- Liverpool School of Tropical Medicine, Liverpool, UK
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11
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Benelli G. Managing mosquitoes and ticks in a rapidly changing world - Facts and trends. Saudi J Biol Sci 2018; 26:921-929. [PMID: 31303820 PMCID: PMC6600734 DOI: 10.1016/j.sjbs.2018.06.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Revised: 06/06/2018] [Accepted: 06/26/2018] [Indexed: 02/08/2023] Open
Abstract
Vector-borne diseases transmitted by mosquitoes and ticks are on the rise. The effective and sustainable control of these arthropod vectors is a puzzling challenge for public health worldwide. In the present review, I attempted to provide a concise and updated overview of the current mosquito and tick research scenario. The wide array of control tools recently developed has been considered, with special reference to those approved by the World Health Organization Vector Control Advisory Group (WHO VCAG), as well as novel ones with an extremely promising potential to be exploited in vector control programs. Concerning mosquitoes, a major focus has been given on genetically modified vectors, eave tubes, attractive toxic sugar baits (ATSB) and biocontrol agents. Regarding ticks, the recent development of highly effective repellents and acaricides (including nanoformulated ones) as well as behavior-based control tools, has been highlighted. In the second part of the review, key research questions about biology and control of mosquitoes and ticks have been critically formulated. A timely research agenda outlining hot issues to be addressed in mosquito and tick research is provided. Overall, it is expected that the present review will contribute to boost research and applications on successful mosquito and tick control strategies, along with an improved knowledge of their biology and ecology.
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Affiliation(s)
- Giovanni Benelli
- Department of Agriculture, Food and Environment, University of Pisa, via del Borghetto 80, 56124 Pisa, Italy.,The BioRobotics Institute, Sant'Anna School of Advanced Studies, viale Rinaldo Piaggio 34, 56025, Pontedera, Pisa, Italy
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12
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Sherrard-Smith E, Sala KA, Betancourt M, Upton LM, Angrisano F, Morin MJ, Ghani AC, Churcher TS, Blagborough AM. Synergy in anti-malarial pre-erythrocytic and transmission-blocking antibodies is achieved by reducing parasite density. eLife 2018; 7:35213. [PMID: 29914622 PMCID: PMC6008048 DOI: 10.7554/elife.35213] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Accepted: 05/18/2018] [Indexed: 01/05/2023] Open
Abstract
Anti-malarial pre-erythrocytic vaccines (PEV) target transmission by inhibiting human infection but are currently partially protective. It has been posited, but never demonstrated, that co-administering transmission-blocking vaccines (TBV) would enhance malaria control. We hypothesized a mechanism that TBV could reduce parasite density in the mosquito salivary glands, thereby enhancing PEV efficacy. This was tested using a multigenerational population assay, passaging Plasmodium berghei to Anopheles stephensi mosquitoes. A combined efficacy of 90.8% (86.7-94.2%) was observed in the PEV +TBV antibody group, higher than the estimated efficacy of 83.3% (95% CrI 79.1-87.0%) if the two antibodies acted independently. Higher PEV efficacy at lower mosquito parasite loads was observed, comprising the first direct evidence that co-administering anti-sporozoite and anti-transmission interventions act synergistically, enhancing PEV efficacy across a range of TBV doses and transmission intensities. Combining partially effective vaccines of differing anti-parasitic classes is a pragmatic, powerful way to accelerate malaria elimination efforts.
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Affiliation(s)
- Ellie Sherrard-Smith
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
| | - Katarzyna A Sala
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | | | - Leanna M Upton
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Fiona Angrisano
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | | | - Azra C Ghani
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
| | - Thomas S Churcher
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
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13
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Amadi JA, Olago DO, Ong'amo GO, Oriaso SO, Nyamongo IK, Estambale BBA. "We don't want our clothes to smell smoke": changing malaria control practices and opportunities for integrated community-based management in Baringo, Kenya. BMC Public Health 2018; 18:609. [PMID: 29743062 PMCID: PMC5944038 DOI: 10.1186/s12889-018-5513-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 04/26/2018] [Indexed: 11/30/2022] Open
Abstract
Background The decline in global malaria cases is attributed to intensified utilization of primary vector control interventions and artemisinin-based combination therapies (ACTs). These strategies are inadequate in many rural areas, thus adopting locally appropriate integrated malaria control strategies is imperative in these heterogeneous settings. This study aimed at investigating trends and local knowledge on malaria and to develop a framework for malaria control for communities in Baringo, Kenya. Methods Clinical malaria cases obtained from four health facilities in the riverine and lowland zones were used to analyse malaria trends for the 2005–2014 period. A mixed method approach integrating eight focus group discussions, 12 key informant interviews, 300 survey questionnaires and two stakeholders’ consultative forums were used to assess local knowledge on malaria risk and develop a framework for malaria reduction. Results Malaria cases increased significantly during the 2005–2014 period (tau = 0.352; p < 0.001) in the riverine zone. March, April, May, June and October showed significant increases compared to other months. Misconceptions about the cause and mode of malaria transmission existed. Gender-segregated outdoor occupation such as social drinking, farm activities, herding, and circumcision events increased the risk of mosquito bites. A positive relationship occurred between education level and opinion on exposure to malaria risk after dusk (χ2 = 2.70, p < 0.05). There was over-reliance on bed nets, yet only 68% (204/300) of respondents owned at least one net. Complementary malaria control measures were under-utilized, with 90% of respondents denying having used either sprays, repellents or burnt cow dung or plant leaves over the last one year before the study was conducted. Baraza, radios, and mobile phone messages were identified as effective media for malaria information exchange. Supplementary strategies identified included unblocking canals, clearing Prosopis bushes, and use of community volunteers and school clubs to promote social behaviour change. Conclusions The knowledge gap on malaria transmission should be addressed to minimize the impacts and enhance uptake of appropriate malaria management mechanisms. Implementing community-based framework can support significant reductions in malaria prevalence by minimizing both indoor and outdoor malaria transmissions.
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Affiliation(s)
- Jacinter A Amadi
- Institute for Climate Change and Adaptation, University of Nairobi, Nairobi, Kenya. .,Department of Plant Sciences, Kenyatta University, Nairobi, Kenya.
| | - Daniel O Olago
- Institute for Climate Change and Adaptation, University of Nairobi, Nairobi, Kenya
| | - George O Ong'amo
- School of Biological Sciences, University of Nairobi, Nairobi, Kenya
| | - Silas O Oriaso
- Institute for Climate Change and Adaptation, University of Nairobi, Nairobi, Kenya
| | - Isaac K Nyamongo
- Cooperative Development, Research and Innovation, The Cooperative University of Kenya, Nairobi, Kenya
| | - Benson B A Estambale
- Division of Research Innovation and Outreach, Jaramogi Oginga Odinga University of Science and Technology, Bondo, Kenya
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14
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Ngufor C, N'Guessan R, Fagbohoun J, Todjinou D, Odjo A, Malone D, Ismail H, Akogbeto M, Rowland M. Efficacy of the Olyset Duo net against insecticide-resistant mosquito vectors of malaria. Sci Transl Med 2017; 8:356ra121. [PMID: 27629488 DOI: 10.1126/scitranslmed.aad3270] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 08/26/2016] [Indexed: 11/02/2022]
Abstract
Olyset Duo is a new long-lasting insecticidal net treated with permethrin (a pyrethroid) and pyriproxyfen, an insect growth regulator that disrupts the maturation of oocytes in mosquitoes exposed to the net. We tested the Olyset Duo net against pyrethroid-resistant Anopheles gambiae mosquitoes, which transmit malaria parasites, in laboratory bioassays and in a trial in Benin using experimental huts that closely resemble local habitations. Host-seeking mosquitoes that entered to feed were free to contact the occupied nets and were collected the next morning from exit traps. Surviving blood-fed mosquitoes were observed for effects on reproduction. Control nets were treated with pyrethroid only or pyriproxyfen only, and nets were tested unwashed and after 20 standardized washes. The Olyset Duo net showed improved efficacy and wash resistance relative to the pyrethroid-treated net in terms of mosquito mortality and prevention of blood feeding. The production of offspring among surviving blood-fed A. gambiae in the hut trial was reduced by the pyriproxyfen-treated net and the Olyset Duo net both before washing (90 and 71% reduction, respectively) and after washing (38 and 43% reduction, respectively). The degree of reproductive suppression in the hut trial was predicted by laboratory tunnel tests but not by cone bioassays. The overall reduction in reproductive rate of A. gambiae with the Olyset Duo net in the trial was 94% with no washing and 78% after 20 washes. The Olyset Duo net has the potential to provide community control of mosquito populations and reduce malaria transmission in areas of high insecticide resistance.
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Affiliation(s)
- Corine Ngufor
- London School of Hygiene and Tropical Medicine, London WC1E 7HT, U.K. Centre de Recherches Entomologiques de Cotonou, Ministry of Health, Cotonou 06 BP 2604, Benin. Pan African Malaria Vector Research Consortium, London WC1E 7HT, U.K.
| | - Raphael N'Guessan
- London School of Hygiene and Tropical Medicine, London WC1E 7HT, U.K. Centre de Recherches Entomologiques de Cotonou, Ministry of Health, Cotonou 06 BP 2604, Benin. Pan African Malaria Vector Research Consortium, London WC1E 7HT, U.K
| | - Josias Fagbohoun
- Centre de Recherches Entomologiques de Cotonou, Ministry of Health, Cotonou 06 BP 2604, Benin
| | - Damien Todjinou
- Centre de Recherches Entomologiques de Cotonou, Ministry of Health, Cotonou 06 BP 2604, Benin
| | - Abibath Odjo
- Centre de Recherches Entomologiques de Cotonou, Ministry of Health, Cotonou 06 BP 2604, Benin
| | - David Malone
- Innovative Vector Control Consortium, Liverpool L3 5QA, U.K
| | - Hanafy Ismail
- Liverpool School of Tropical Medicine, Liverpool L3 5QA, U.K
| | - Martin Akogbeto
- Centre de Recherches Entomologiques de Cotonou, Ministry of Health, Cotonou 06 BP 2604, Benin
| | - Mark Rowland
- London School of Hygiene and Tropical Medicine, London WC1E 7HT, U.K. Pan African Malaria Vector Research Consortium, London WC1E 7HT, U.K
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15
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Ranson H. Current and Future Prospects for Preventing Malaria Transmission via the Use of Insecticides. Cold Spring Harb Perspect Med 2017; 7:a026823. [PMID: 28507193 PMCID: PMC5666625 DOI: 10.1101/cshperspect.a026823] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Malaria vectors have developed resistance to all classes of insecticides that are used to target the adult mosquito to prevent parasite transmission. The number of resistant mosquito populations has increased dramatically in recent years, most likely as a result of the scale-up of vector control activities, and the intensity of this resistance is increasing rapidly and compromising the performance of vector control tools. Bednets and indoor residual spray formulations containing alternative active ingredients have shown promise in field trials but are still several years away from implementation. As existing insecticides become less effective at killing mosquitoes in the countries with the highest burden of malaria, there is growing concern that the advances made in reducing malaria transmission will be eroded by insecticide resistance. The likelihood of this scenario, and strategies that may help mitigate against this, are reviewed below.
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Affiliation(s)
- Hilary Ranson
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool L3 5QA, United Kingdom
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16
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Alout H, Labbé P, Chandre F, Cohuet A. Malaria Vector Control Still Matters despite Insecticide Resistance. Trends Parasitol 2017; 33:610-618. [PMID: 28499699 DOI: 10.1016/j.pt.2017.04.006] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 04/14/2017] [Accepted: 04/18/2017] [Indexed: 11/26/2022]
Abstract
Mosquito vectors' resistance to insecticides is usually considered a major threat to the recent progresses in malaria control. However, studies measuring the impact of interventions and insecticide resistance reveal inconsistencies when using entomological versus epidemiological indices. First, evaluation tests that do not reflect the susceptibility of mosquitoes when they are infectious may underestimate insecticide efficacy. Moreover, interactions between insecticide resistance and vectorial capacity reveal nonintuitive outcomes of interventions. Therefore, considering ecological interactions between vector, parasite, and environment highlights that the impact of insecticide resistance on the malaria burden is not straightforward and we suggest that vector control still matters despite insecticide resistance.
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Affiliation(s)
- Haoues Alout
- Institut des Sciences de l'Evolution de Montpellier, CNRS, IRD, University of Montpellier, ISEM - UMR 5554, Montpellier, France.
| | - Pierrick Labbé
- Institut des Sciences de l'Evolution de Montpellier, CNRS, IRD, University of Montpellier, ISEM - UMR 5554, Montpellier, France
| | - Fabrice Chandre
- Institut de recherche pour le développement (IRD), Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), UM-CNRS 5290 IRD 224, Montpellier, France
| | - Anna Cohuet
- Institut de recherche pour le développement (IRD), Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), UM-CNRS 5290 IRD 224, Montpellier, France.
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17
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Yunta C, Grisales N, Nász S, Hemmings K, Pignatelli P, Voice M, Ranson H, Paine MJI. Pyriproxyfen is metabolized by P450s associated with pyrethroid resistance in An. gambiae. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2016; 78:50-57. [PMID: 27613592 PMCID: PMC6399515 DOI: 10.1016/j.ibmb.2016.09.001] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Revised: 08/31/2016] [Accepted: 09/02/2016] [Indexed: 05/25/2023]
Abstract
Pyrethroid resistance is widespread in the malaria vector Anopheles gambiae leading to concerns about the future efficacy of bednets with pyrethroids as the sole active ingredient. The incorporation of pyriproxyfen (PPF), a juvenile hormone analogue, into pyrethroid treated bednets is being trialed in Africa. Pyrethroid resistance is commonly associated with elevated levels of P450 expression including CYPs 6M2, 6P2, 6P3, 6P4, 6P5, 6Z2 and 9J5. Having expressed these P450s in E. coli we find all are capable of metabolizing PPF. Inhibition of these P450s by permethrin, deltamethrin and PPF was also examined. Deltamethrin and permethrin were moderate inhibitors (IC50 1-10 μM) of diethoxyfluorescein (DEF) activity for all P450s apart from CYP6Z2 (IC50 > 10 μM), while PPF displayed weaker inhibition of all P450s (IC50 > 10 μM) except CYP's 6Z2 and 6P2 (IC50 1-10 μM). We found evidence of low levels of cross resistance between PPF and other insecticide classes by comparing the efficacy of PPF in inhibiting metamorphosis and inducing female sterility in an insecticide susceptible strain of An. gambiae and a multiple resistant strain from Cote d'Ivoire.
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Affiliation(s)
- Cristina Yunta
- Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Nelson Grisales
- Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Szilárd Nász
- Syngenta, Product Metabolism and Analytical Sciences, Jealott's Hill International Research Centre, Bracknell, RG42 6EY, UK
| | - Kay Hemmings
- Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | | | | | - Hilary Ranson
- Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Mark J I Paine
- Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK.
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18
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Barker D, McElduff P, D'Este C, Campbell MJ. Stepped wedge cluster randomised trials: a review of the statistical methodology used and available. BMC Med Res Methodol 2016; 16:69. [PMID: 27267471 PMCID: PMC4895892 DOI: 10.1186/s12874-016-0176-5] [Citation(s) in RCA: 100] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Accepted: 05/28/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Previous reviews have focussed on the rationale for employing the stepped wedge design (SWD), the areas of research to which the design has been applied and the general characteristics of the design. However these did not focus on the statistical methods nor addressed the appropriateness of sample size methods used.This was a review of the literature of the statistical methodology used in stepped wedge cluster randomised trials. METHODS Literature Review. The Medline, Embase, PsycINFO, CINAHL and Cochrane databases were searched for methodological guides and RCTs which employed the stepped wedge design. RESULTS This review identified 102 trials which employed the stepped wedge design compared to 37 from the most recent review by Beard et al. 2015. Forty six trials were cohort designs and 45 % (n = 46) had fewer than 10 clusters. Of the 42 articles discussing the design methodology 10 covered analysis and seven covered sample size. For cohort stepped wedge designs there was only one paper considering analysis and one considering sample size methods. Most trials employed either a GEE or mixed model approach to analysis (n = 77) but only 22 trials (22 %) estimated sample size in a way which accounted for the stepped wedge design that was subsequently used. CONCLUSIONS Many studies which employ the stepped wedge design have few clusters but use methods of analysis which may require more clusters for unbiased and efficient intervention effect estimates. There is the need for research on the minimum number of clusters required for both types of stepped wedge design. Researchers should distinguish in the sample size calculation between cohort and cross sectional stepped wedge designs. Further research is needed on the effect of adjusting for the potential confounding of time on the study power.
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Affiliation(s)
- D Barker
- School of Medicine and Public Health, Faculty of Health, CCEB, HMRI Building, Level 4 West, University of Newcastle, University Drive, Callaghan, NSW, 2308, Australia.
| | - P McElduff
- School of Medicine and Public Health, Faculty of Health, CCEB, HMRI Building, Level 4 West, University of Newcastle, University Drive, Callaghan, NSW, 2308, Australia
| | - C D'Este
- School of Medicine and Public Health, Faculty of Health, CCEB, HMRI Building, Level 4 West, University of Newcastle, University Drive, Callaghan, NSW, 2308, Australia.,National Centre for Epidemiology and Population Health, Research School of Population Health, Australian National University, Canberra, ACT, 0200, Australia
| | - M J Campbell
- Medical Statistics Group, ScHARR, University of Sheffield, Sheffield, UK
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19
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Ranson H, Lissenden N. Insecticide Resistance in African Anopheles Mosquitoes: A Worsening Situation that Needs Urgent Action to Maintain Malaria Control. Trends Parasitol 2016; 32:187-196. [PMID: 26826784 DOI: 10.1016/j.pt.2015.11.010] [Citation(s) in RCA: 531] [Impact Index Per Article: 66.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Revised: 11/13/2015] [Accepted: 11/17/2015] [Indexed: 11/16/2022]
Abstract
Malaria control is reliant on insecticides to control the mosquito vector. As efforts to control the disease have intensified, so has the selection pressure on mosquitoes to develop resistance to these insecticides. The distribution and strength of this resistance has increased dramatically in recent years and now threatens the success of control programs. This review provides an update on the current status of resistance to the major insecticide classes in African malaria vectors, considers the evidence that this resistance is already compromising malaria control efforts, and looks to the future to highlight some of the new insecticide-based tools under development and the challenges in ensuring they are most effectively deployed to manage resistance.
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Affiliation(s)
- Hilary Ranson
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK.
| | - Natalie Lissenden
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
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20
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Sagnon N, Pinder M, Tchicaya EF, Tiono AB, Faragher B, Ranson H, Lindsay SW. To assess whether addition of pyriproxyfen to long-lasting insecticidal mosquito nets increases their durability compared to standard long-lasting insecticidal mosquito nets: study protocol for a randomised controlled trial. Trials 2015; 16:195. [PMID: 25927378 PMCID: PMC4423132 DOI: 10.1186/s13063-015-0700-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Accepted: 04/01/2015] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND The effectiveness of pyrethroid-treated bednets for malaria control in sub-Saharan Africa is under threat because of high levels of resistance to pyrethroid insecticides in the vectors. Here we assess the durability of polyethylene nets with a novel combination of permethrin, a pyrethroid, with pyriproxyfen, an insect juvenile mimic (PPF-LLIN), in comparison with a typical permethrin-treated long-lasting insecticidal net (LLIN). METHODS This is a cluster randomised controlled trial of net durability in Burkina Faso, with clustering at the level of the compound and includes entomological outcome measurements. Half the compounds in each village will be randomly allocated PPF-LLIN and half the LLIN. All sleeping places in a compound will be provided with one type of net. We will distribute the nets at the start of the first transmission season and follow net use at the start and end of each transmission season for 3 years. In one village, bio-efficacy and chemical content will be recorded immediately after net distribution and then at 6, 12, 18, 24, 30 and 36 months. In the other village net survivorship and fabric integrity will be recorded immediately after distribution, and then at 6, 12, 18, 24, 30 and 36 months. Routine measurements of indoor temperature and relative humidity will be made in both villages during the study. Residents will be followed for possible side effects of the PPF-LLIN by surveillance of known asthmatic subjects during the first month post-distribution and pregnancy outcomes will be monitored from antenatal clinic records. DISCUSSION The protocol is novel on two accounts. Firstly, it is the first to describe the procedure for measuring net durability following recent World Health Organisation (WHO) guidelines. Meeting the minimum requirements set in the guidelines is essential before a new type of net can be recommended by WHO's Pesticide Evaluation Scheme (WHOPES). Secondly, it describes methods to monitor the persistence of an active ingredient that reduces vector fertility and fecundity. If the PPF-LLIN is both effective and persistent it will provide an alternative vector control strategy where pyrethroid-resistant vectors are present. TRIAL REGISTRATION ISRCTN30634670 assigned 13 August 2014.
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Affiliation(s)
- N'Fale Sagnon
- 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, PO Box 273, Banjul, The Gambia.
| | - Emile Fs Tchicaya
- Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, Abidjan, Côte d'Ivoire.
| | - Alfred B Tiono
- Centre National de Recherche et de Formation sur le Paludisme (CNRFP), Ouagadougou, Burkina Faso.
| | | | - 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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