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Kilpatrick KW, Lee C, Hudgens MG. G-formula for observational studies under stratified interference, with application to bed net use on malaria. Stat Med 2024; 43:2853-2868. [PMID: 38726590 PMCID: PMC11187673 DOI: 10.1002/sim.10102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Revised: 04/22/2024] [Accepted: 04/24/2024] [Indexed: 05/16/2024]
Abstract
Assessing population-level effects of vaccines and other infectious disease prevention measures is important to the field of public health. In infectious disease studies, one person's treatment may affect another individual's outcome, that is, there may be interference between units. For example, the use of bed nets to prevent malaria by one individual may have an indirect effect on other individuals living in close proximity. In some settings, individuals may form groups or clusters where interference only occurs within groups, that is, there is partial interference. Inverse probability weighted estimators have previously been developed for observational studies with partial interference. Unfortunately, these estimators are not well suited for studies with large clusters. Therefore, in this paper, the parametric g-formula is extended to allow for partial interference. G-formula estimators are proposed for overall effects, effects when treated, and effects when untreated. The proposed estimators can accommodate large clusters and do not suffer from the g-null paradox that may occur in the absence of interference. The large sample properties of the proposed estimators are derived assuming no unmeasured confounders and that the partial interference takes a particular form (referred to as 'weak stratified interference'). Simulation studies are presented demonstrating the finite-sample performance of the proposed estimators. The Demographic and Health Survey from the Democratic Republic of the Congo is then analyzed using the proposed g-formula estimators to assess the effects of bed net use on malaria.
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Affiliation(s)
- Kayla W. Kilpatrick
- Department of Biostatistics and Bioinformatics, Duke University, Durham, North Carolina, U.S.A
| | - Chanhwa Lee
- Department of Biostatistics, University of North Carolina, Chapel Hill, North Carolina, U.S.A
| | - Michael G. Hudgens
- Department of Biostatistics, University of North Carolina, Chapel Hill, North Carolina, U.S.A
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2
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Ochomo E, Rund SSC, Mthawanji RS, Antonio-Nkondjio C, Machani M, Samake S, Wolie RZ, Nsango S, Lown LA, Matoke-Muhia D, Kamau L, Lukyamuzi E, Njeri J, Chabi J, Akrofi OO, Ntege C, Mero V, Mwalimu C, Kiware S, Bilgo E, Traoré MM, Afrane Y, Hakizimana E, Muleba M, Orefuwa E, Chaki P, Juma EO. Mosquito control by abatement programmes in the United States: perspectives and lessons for countries in sub-Saharan Africa. Malar J 2024; 23:8. [PMID: 38178145 PMCID: PMC10768238 DOI: 10.1186/s12936-023-04829-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Accepted: 12/21/2023] [Indexed: 01/06/2024] Open
Abstract
Africa and the United States are both large, heterogeneous geographies with a diverse range of ecologies, climates and mosquito species diversity which contribute to disease transmission and nuisance biting. In the United States, mosquito control is nationally, and regionally coordinated and in so much as the Centers for Disease Control (CDC) provides guidance, the Environmental Protection Agency (EPA) provides pesticide registration, and the states provide legal authority and oversight, the implementation is usually decentralized to the state, county, or city level. Mosquito control operations are organized, in most instances, into fully independent mosquito abatement districts, public works departments, local health departments. In some cases, municipalities engage independent private contractors to undertake mosquito control within their jurisdictions. In sub-Saharan Africa (SSA), where most vector-borne disease endemic countries lie, mosquito control is organized centrally at the national level. In this model, the disease control programmes (national malaria control programmes or national malaria elimination programmes (NMCP/NMEP)) are embedded within the central governments' ministries of health (MoHs) and drive vector control policy development and implementation. Because of the high disease burden and limited resources, the primary endpoint of mosquito control in these settings is reduction of mosquito borne diseases, primarily, malaria. In the United States, however, the endpoint is mosquito control, therefore, significant (or even greater) emphasis is laid on nuisance mosquitoes as much as disease vectors. The authors detail experiences and learnings gathered by the delegation of African vector control professionals that participated in a formal exchange programme initiated by the Pan-African Mosquito Control Association (PAMCA), the University of Notre Dame, and members of the American Mosquito Control Association (AMCA), in the United States between the year 2021 and 2022. The authors highlight the key components of mosquito control operations in the United States and compare them to mosquito control programmes in SSA countries endemic for vector-borne diseases, deriving important lessons that could be useful for vector control in SSA.
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Affiliation(s)
- Eric Ochomo
- Entomology Department, Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya.
- Vector Control Products Unit, Researchworld Limited, Kisumu, Kenya.
| | | | - Rosheen S Mthawanji
- Vector Biology Group, Malawi Liverpool Wellcome Trust Clinical Research Programme, Blantyre, Malawi
| | - Christophe Antonio-Nkondjio
- Organisation de Coordination Pour la lutte contre les Endémies en Afrique centrale (OCEAC), Yaounde, Cameroon
| | - Maxwell Machani
- Entomology Department, Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya
| | | | - Rosine Z Wolie
- Vector Control Product Evaluation Centre - Institut Pierre Richet (VCPEC-IPR), Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire
- Unité de Formation et de Recherche des Sciences de la Nature, Université Nangui Abrogoua, Abdijan, Côte d'Ivoire
| | - Sandrine Nsango
- Faculty of Medicine and Pharmaceutical Sciences, University of Douala, Douala, Cameroon
- Centre Pasteur in Cameroon, Yaounde, Cameroon
| | | | - Damaris Matoke-Muhia
- Pan-African Mosquito Control Association (PAMCA), KEMRI Headquarters, Nairobi, Kenya
- Centre for Biotechnology Research and Development, Kenya Medical Research Institute, Nairobi, Kenya
| | - Luna Kamau
- Centre for Biotechnology Research and Development, Kenya Medical Research Institute, Nairobi, Kenya
| | - Edward Lukyamuzi
- Pan-African Mosquito Control Association (PAMCA), KEMRI Headquarters, Nairobi, Kenya
| | - Jane Njeri
- Pan-African Mosquito Control Association (PAMCA), KEMRI Headquarters, Nairobi, Kenya
| | | | | | - Charles Ntege
- National Malaria Control Division Ministry of Health, Kampala, Uganda
| | - Victor Mero
- Ifakara Health Institute (IHI), Dar es Salaam, Tanzania
| | | | - Samson Kiware
- Pan-African Mosquito Control Association (PAMCA), KEMRI Headquarters, Nairobi, Kenya
- Ifakara Health Institute (IHI), Dar es Salaam, Tanzania
| | - Etienne Bilgo
- Institut de Recherche en Sciences de la Sante (IRSS) Direction regionale de l'Ouest, Bobo Dioulasso, Burkina Faso
| | - Mohamed Moumine Traoré
- Malaria Research and Training Centre, Faculty of Medicine, Pharmacy and Odonto-Stomatology, University of Sciences, Techniques and Technology of Bamako, BP 1805, Bamako, Mali
| | - Yaw Afrane
- Department of Medical Microbiology, University of Ghana Medical School, College of Health Sciences, University of Ghana, Accra, Ghana
| | - Emmanuel Hakizimana
- Malaria and Other Parasitic Diseases Division, Rwanda Biomedical Centre (RBC), Ministry of Health, Kigali, Rwanda
- Pan-African Mosquito Control Organization (PAMCO), Rwanda Chapter, Kigali, Rwanda
| | | | - Emma Orefuwa
- Pan-African Mosquito Control Association (PAMCA), KEMRI Headquarters, Nairobi, Kenya
| | - Prosper Chaki
- Pan-African Mosquito Control Association (PAMCA), KEMRI Headquarters, Nairobi, Kenya
| | - Elijah Omondi Juma
- Pan-African Mosquito Control Association (PAMCA), KEMRI Headquarters, Nairobi, Kenya
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Diop A, Ndiaye F, Sturm-Ramirez K, Konate L, Senghor M, Diouf EH, Dia AK, Diedhiou S, Samb B, Sene D, Zohdy S, Dotson E, Diouf MB, Koscelnik V, Gerberg L, Bangoura A, Faye O, Clark T, Niang EHA, Chabi J. Urban malaria vector bionomics and human sleeping behavior in three cities in Senegal. Parasit Vectors 2023; 16:331. [PMID: 37726787 PMCID: PMC10510207 DOI: 10.1186/s13071-023-05932-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2023] [Accepted: 08/15/2023] [Indexed: 09/21/2023] Open
Abstract
BACKGROUND Malaria is endemic in Senegal, with seasonal transmission, and the entire population is at risk. In recent years, high malaria incidence has been reported in urban and peri-urban areas of Senegal. An urban landscape analysis was conducted in three cities to identify the malaria transmission indicators and human behavior that may be driving the increasing malaria incidence occurring in urban environments. Specifically, mosquito vector bionomics and human sleeping behaviors including outdoor sleeping habits were assessed to guide the optimal deployment of targeted vector control interventions. METHODS Longitudinal entomological monitoring using human landing catches and pyrethrum spray catches was conducted from May to December 2019 in Diourbel, Kaolack, and Touba, the most populous cities in Senegal after the capital Dakar. Additionally, a household survey was conducted in randomly selected houses and residential Koranic schools in the same cities to assess house structures, sleeping spaces, sleeping behavior, and population knowledge about malaria and vector control measures. RESULTS Of the 8240 Anopheles mosquitoes collected from all the surveyed sites, 99.4% (8,191) were An. gambiae s.l., and predominantly An. arabiensis (99%). A higher number of An. gambiae s.l. were collected in Kaolack (77.7%, n = 6496) than in Diourbel and Touba. The overall mean human biting rate was 14.2 bites per person per night (b/p/n) and was higher outdoors (15.9 b/p/n) than indoors (12.5 b/p/n). The overall mean entomological inoculation rates ranged from 3.7 infectious bites per person per year (ib/p/y) in Diourbel to 40.2 ib/p/y in Kaolack. Low anthropophilic rates were recorded at all sites (average 35.7%). Of the 1202 households surveyed, about 24.3% of household members slept outdoors, except during the short rainy season between July and October, despite understanding how malaria is transmitted and the vector control measures used to prevent it. CONCLUSION Anopheles arabiensis was the primary malaria vector in the three surveyed cities. The species showed an outdoor biting tendency, which represents a risk for the large proportion of the population sleeping outdoors. As all current vector control measures implemented in the country target endophilic vectors, these data highlight potential gaps in population protection and call for complementary tools and approaches targeting outdoor biting malaria vectors.
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Affiliation(s)
- Abdoulaye Diop
- U.S. President's Malaria Initiative (PMI) Abt Associates/VectorLink Project, Dakar, Senegal
| | - Fatou Ndiaye
- Laboratoire d'Ecologie Vectorielle et Parasitaire, Faculté Des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal
| | - Katherine Sturm-Ramirez
- U.S. President's Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention (CDC), Atlanta, GA, USA
| | - Lassana Konate
- Laboratoire d'Ecologie Vectorielle et Parasitaire, Faculté Des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal
| | - Massila Senghor
- Laboratoire d'Ecologie Vectorielle et Parasitaire, Faculté Des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal
| | - El Hadji Diouf
- Laboratoire d'Ecologie Vectorielle et Parasitaire, Faculté Des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal
| | - Abdoulaye Kane Dia
- Laboratoire d'Ecologie Vectorielle et Parasitaire, Faculté Des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal
| | - Seynabou Diedhiou
- Laboratoire d'Ecologie Vectorielle et Parasitaire, Faculté Des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal
| | - Badara Samb
- Laboratoire d'Ecologie Vectorielle et Parasitaire, Faculté Des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal
| | - Doudou Sene
- National Malaria Control Programme, Dakar, Senegal
| | - Sarah Zohdy
- U.S. President's Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention (CDC), Atlanta, GA, USA
| | - Ellen Dotson
- U.S. President's Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention (CDC), Atlanta, GA, USA
| | - Mame Birame Diouf
- U.S. President's Malaria Initiative, United States Agency for International Development (USAID), Dakar, Senegal
| | - Valerie Koscelnik
- U.S. President's Malaria Initiative, United States Agency for International Development (USAID), Dakar, Senegal
| | - Lilia Gerberg
- U.S. President's Malaria Initiative, United States Agency for International Development (USAID), Washington, DC, USA
| | - Abdoulaye Bangoura
- U.S. President's Malaria Initiative, Abt Associates/VectorLink Project Rockville, Rockville, DC, USA
| | - Ousmane Faye
- Laboratoire d'Ecologie Vectorielle et Parasitaire, Faculté Des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal
| | - Tiffany Clark
- U.S. President's Malaria Initiative, Abt Associates/VectorLink Project Rockville, Rockville, DC, USA
| | - El Hadji Amadou Niang
- Laboratoire d'Ecologie Vectorielle et Parasitaire, Faculté Des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal
| | - Joseph Chabi
- U.S. President's Malaria Initiative, Abt Associates/VectorLink Project Rockville, Rockville, DC, USA.
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4
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Velleman Y, Blair L, Fleming F, Fenwick A. Water-, Sanitation-, and Hygiene-Related Diseases. Infect Dis (Lond) 2023. [DOI: 10.1007/978-1-0716-2463-0_547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/10/2023] Open
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5
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Ngonghala CN. Assessing the impact of insecticide-treated nets in the face of insecticide resistance on malaria control. J Theor Biol 2022; 555:111281. [PMID: 36154815 DOI: 10.1016/j.jtbi.2022.111281] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 09/01/2022] [Accepted: 09/17/2022] [Indexed: 01/14/2023]
Abstract
The mosquito-borne disease, malaria, continues to impose a devastating health and economic burden worldwide. In malaria-endemic areas, insecticide-treated nets (ITNs) have been useful in curtailing the burden of the disease. However, mosquito resistance to insecticides, decay in ITN efficacy, net attrition, etc., undermine the effectiveness of ITNs in combatting malaria. In this study, mathematical models that account for asymptomatic infectious humans (through a partially immune class or a separate asymptomatic infectious class), insecticide resistance, and decay in ITN efficacy are proposed and analyzed. Analytical and numerical results of the models when ITN efficacy is constant show that there are parameter regimes for which a backward bifurcation occurs. Local and global sensitivity analyses are performed to identify parameters (some of which are potential targets for disease control) with the most significant influence on the control reproduction (Rc) and disease prevalence. These influential parameters include the maximum biting rate of resistant mosquitoes, ITN coverage, initial ITN efficacy against sensitive mosquitoes, the probability that an infectious mosquito (human) infects a susceptible human (mosquito), and the rate at which adult mosquitoes develop (lose) resistance to insecticides. Simulations of the models show that accounting for asymptomatic infectious humans through a separate class, or not accounting for the decay in ITN efficacy leads to an underestimation of disease burden. In particular, if the initial efficacy of ITNs against sensitive and resistance mosquitoes is 96%, the minimum ITN coverage required to reduce Rc below one (and hence, contain malaria) is approximately 11% (27%) lower when ITN efficacy is averaged (constant) for a model with a separate asymptomatic class. For the model with a partially immune class and decaying ITN efficacy, reducing Rc below one is impossible even if the entire populace uses ITNs. The study shows that replacing ITNs before their prescribed lifespans, or designing ITNs with longer lifespans is important for malaria control. Furthermore, the study shows that piperonyl butoxide (PBO) ITNs (which inhibit or reverse insecticide resistance) outperform regular ITNs in malaria control. Hence, prospects for effectively controlling malaria are enhanced by widespread use of high quality ITNs (e.g. PBO ITNs), especially if the useful lifespans of the ITNs are long enough and the ITNs are replaced before the end of their useful lifespans.
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Affiliation(s)
- Calistus N Ngonghala
- Department of Mathematics, University of Florida, 1400 Stadium Rd, Gainesville, FL 32611, United States of America; Emerging Pathogens Institute, University of Florida, 2055 Mowry Rd, Gainesville, FL 32610, United States of America; Center for African Studies, University of Florida, 427 Grinter Hall 1523 Union Rd, Gainesville, FL 32611, United States of America.
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6
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Douglas NM, Burkot TR, Price RN. Malaria eradication revisited. Int J Epidemiol 2022; 51:382-392. [PMID: 34918106 DOI: 10.1093/ije/dyab259] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Accepted: 12/06/2021] [Indexed: 01/13/2023] Open
Affiliation(s)
- Nicholas M Douglas
- Department of Medicine, University of Otago, Christchurch, New Zealand.,Division of Global and Tropical Health, Menzies School of Health Research, Charles Darwin University, Darwin, Northern Territory, Australia.,Department of Infectious Diseases, Christchurch Hospital, Christchurch, New Zealand
| | - Thomas R Burkot
- Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, QLD, Australia
| | - Ric N Price
- Division of Global and Tropical Health, Menzies School of Health Research, Charles Darwin University, Darwin, Northern Territory, Australia.,Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
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7
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García GA, Atkinson B, Donfack OT, Hilton ER, Smith JM, Eyono JNM, Iyanga MM, Vaz LM, Mba Nguema Avue R, Pollock J, Ratsirarson J, Aldrich EM, Phiri WP, Smith DL, Schwabe C, Guerra CA. Real-time, spatial decision support to optimize malaria vector control: The case of indoor residual spraying on Bioko Island, Equatorial Guinea. PLOS DIGITAL HEALTH 2022; 1:e0000025. [PMID: 36812503 PMCID: PMC9931250 DOI: 10.1371/journal.pdig.0000025] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Accepted: 03/15/2022] [Indexed: 06/18/2023]
Abstract
Public health interventions require evidence-based decision-making to maximize impact. Spatial decision support systems (SDSS) are designed to collect, store, process and analyze data to generate knowledge and inform decisions. This paper discusses how the use of a SDSS, the Campaign Information Management System (CIMS), to support malaria control operations on Bioko Island has impacted key process indicators of indoor residual spraying (IRS): coverage, operational efficiency and productivity. We used data from the last five annual IRS rounds (2017 to 2021) to estimate these indicators. IRS coverage was calculated as the percentage of houses sprayed per unit area, represented by 100x100 m map-sectors. Optimal coverage was defined as between 80% and 85%, and under and overspraying as coverage below 80% and above 85%, respectively. Operational efficiency was defined as the fraction of map-sectors that achieved optimal coverage. Daily productivity was expressed as the number of houses sprayed per sprayer per day (h/s/d). These indicators were compared across the five rounds. Overall IRS coverage (i.e. percent of total houses sprayed against the overall denominator by round) was highest in 2017 (80.2%), yet this round showed the largest proportion of oversprayed map-sectors (36.0%). Conversely, despite producing a lower overall coverage (77.5%), the 2021 round showed the highest operational efficiency (37.7%) and the lowest proportion of oversprayed map-sectors (18.7%). In 2021, higher operational efficiency was also accompanied by marginally higher productivity. Productivity ranged from 3.3 h/s/d in 2020 to 3.9 h/s/d in 2021 (median 3.6 h/s/d). Our findings showed that the novel approach to data collection and processing proposed by the CIMS has significantly improved the operational efficiency of IRS on Bioko. High spatial granularity during planning and deployment together with closer follow-up of field teams using real-time data supported more homogeneous delivery of optimal coverage while sustaining high productivity.
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Affiliation(s)
- Guillermo A. García
- Medical Care Development International, Silver Spring, MD, United States of America
| | - Brent Atkinson
- Medical Care Development International, Silver Spring, MD, United States of America
| | | | - Emily R. Hilton
- Institute for Health Metrics and Evaluation, Univeristy of Washington, Seattle, WA, United States of America
| | - Jordan M. Smith
- Medical Care Development International, Malabo, Equatorial Guinea
| | | | | | | | | | - John Pollock
- Medical Care Development, Augusta, ME, United States of America
| | - Josea Ratsirarson
- Medical Care Development International, Silver Spring, MD, United States of America
| | | | - Wonder P. Phiri
- Medical Care Development International, Malabo, Equatorial Guinea
| | - David L. Smith
- Institute for Health Metrics and Evaluation, Univeristy of Washington, Seattle, WA, United States of America
| | | | - Carlos A. Guerra
- Medical Care Development International, Silver Spring, MD, United States of America
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Factors related to long-lasting insecticidal net (LLIN) use during travel in western Kenya: A descriptive analysis. Travel Med Infect Dis 2022; 47:102291. [DOI: 10.1016/j.tmaid.2022.102291] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Revised: 02/15/2022] [Accepted: 02/23/2022] [Indexed: 11/20/2022]
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Ngufor C, Fagbohoun J, Agbevo A, Ismail H, Challenger JD, Churcher TS, Rowland M. Comparative efficacy of two pyrethroid-piperonyl butoxide nets (Olyset Plus and PermaNet 3.0) against pyrethroid resistant malaria vectors: a non-inferiority assessment. Malar J 2022; 21:20. [PMID: 35016676 PMCID: PMC8753866 DOI: 10.1186/s12936-022-04041-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 01/03/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Pyrethroid-PBO nets were conditionally recommended for control of malaria transmitted by mosquitoes with oxidase-based pyrethroid-resistance based on epidemiological evidence of additional protective effect with Olyset Plus compared to a pyrethroid-only net (Olyset Net). Entomological studies can be used to assess the comparative performance of other brands of pyrethroid-PBO ITNs to Olyset Plus. METHODS An experimental hut trial was performed in Cové, Benin to compare PermaNet 3.0 (deltamethrin plus PBO on roof panel only) to Olyset Plus (permethrin plus PBO on all panels) against wild pyrethroid-resistant Anopheles gambiae sensu lato (s.l.) following World Health Organization (WHO) guidelines. Both nets were tested unwashed and after 20 standardized washes compared to Olyset Net. Laboratory bioassays were also performed to help explain findings in the experimental huts. RESULTS With unwashed nets, mosquito mortality was higher in huts with PermaNet 3.0 compared to Olyset Plus (41% vs. 28%, P < 0.001). After 20 washes, mortality declined significantly with PermaNet 3.0 (41% unwashed vs. 17% after washing P < 0.001), but not with Olyset Plus (28% unwashed vs. 24% after washing P = 0.433); Olyset Plus induced significantly higher mortality than PermaNet 3.0 and Olyset Net after 20 washes. PermaNet 3.0 showed a higher wash retention of PBO compared to Olyset Plus. A non-inferiority analysis performed with data from unwashed and washed nets together using a margin recommended by the WHO, showed that PermaNet 3.0 was non-inferior to Olyset Plus in terms of mosquito mortality (25% with Olyset Plus vs. 27% with PermaNet 3.0, OR = 1.528, 95%CI = 1.02-2.29) but not in reducing mosquito feeding (25% with Olyset Plus vs. 30% with PermaNet 3.0, OR = 1.192, 95%CI = 0.77-1.84). Both pyrethroid-PBO nets were superior to Olyset Net. CONCLUSION Olyset Plus outperformed PermaNet 3.0 in terms of its ability to cause greater margins of improved mosquito mortality compared to a standard pyrethroid net, after multiple standardized washes. However, using a margin of non-inferiority defined by the WHO, PermaNet 3.0 was non-inferior to Olyset Plus in inducing mosquito mortality. Considering the low levels of mortality observed and increasing pyrethroid-resistance in West Africa, it is unclear whether either of these nets would demonstrate the same epidemiological impact observed in community trials in East Africa.
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Affiliation(s)
- Corine Ngufor
- London School of Hygiene and Tropical Medicine (LSHTM), London, UK. .,Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin. .,Pan African Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin.
| | - Josias Fagbohoun
- Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin ,Pan African Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
| | - Abel Agbevo
- Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin ,Pan African Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
| | - Hanafy Ismail
- grid.48004.380000 0004 1936 9764Liverpool School of Tropical Medicine, Liverpool, L3 5QA UK
| | - Joseph D. Challenger
- grid.7445.20000 0001 2113 8111MRC Centre for Global Infectious Disease Analysis, Infectious Disease Epidemiology, Imperial College London, Norfolk Place, London, W2 1PG UK
| | - Thomas S. Churcher
- grid.7445.20000 0001 2113 8111MRC Centre for Global Infectious Disease Analysis, Infectious Disease Epidemiology, Imperial College London, Norfolk Place, London, W2 1PG UK
| | - Mark Rowland
- grid.8991.90000 0004 0425 469XLondon School of Hygiene and Tropical Medicine (LSHTM), London, UK ,Pan African Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
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10
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Threats to the effectiveness of insecticide-treated bednets for malaria control: thinking beyond insecticide resistance. LANCET GLOBAL HEALTH 2021; 9:e1325-e1331. [PMID: 34216565 DOI: 10.1016/s2214-109x(21)00216-3] [Citation(s) in RCA: 67] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 04/03/2021] [Accepted: 04/23/2021] [Indexed: 12/22/2022]
Abstract
From 2004 to 2019, insecticide-treated bednets (ITNs) have been the most effective tool for reducing malaria morbidity and mortality in sub-Saharan Africa. Recently, however, the decline in malaria cases and deaths has stalled. Some suggest that this inertia is due to increasing resistance in malaria vectors to the pyrethroid insecticides used for treating ITNs. However, there is presently little evidence to reach this conclusion and we therefore recommend that a broader perspective to evaluate ITN effectiveness in terms of access to nets, use of nets, bioefficacy, and durability should be taken. We argue that a single focus on insecticide resistance misses the bigger picture. To improve the effects of ITNs, net coverage should increase by increasing funding for programmes, adopting improved strategies for increasing ITN uptake, and enhancing the longevity of the active ingredients and the physical integrity of nets, while simultaneously accelerating the development and evaluation of novel vector control tools.
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11
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Gleave K, Lissenden N, Chaplin M, Choi L, Ranson H. Piperonyl butoxide (PBO) combined with pyrethroids in insecticide-treated nets to prevent malaria in Africa. Cochrane Database Syst Rev 2021; 5:CD012776. [PMID: 34027998 PMCID: PMC8142305 DOI: 10.1002/14651858.cd012776.pub3] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
BACKGROUND Pyrethroid long-lasting insecticidal nets (LLINs) have been important in the large reductions in malaria cases in Africa, but insecticide resistance in Anopheles mosquitoes threatens their impact. Insecticide synergists may help control insecticide-resistant populations. Piperonyl butoxide (PBO) is such a synergist; it has been incorporated into pyrethroid-LLINs to form pyrethroid-PBO nets, which are currently produced by five LLIN manufacturers and, following a recommendation from the World Health Organization (WHO) in 2017, are being included in distribution campaigns. This review examines epidemiological and entomological evidence on the addition of PBO to pyrethroid nets on their efficacy. OBJECTIVES To compare effects of pyrethroid-PBO nets currently in commercial development or on the market with effects of their non-PBO equivalent in relation to: 1. malaria parasite infection (prevalence or incidence); and 2. entomological outcomes. SEARCH METHODS We searched the Cochrane Infectious Diseases Group (CIDG) Specialized Register, CENTRAL, MEDLINE, Embase, Web of Science, CAB Abstracts, and two clinical trial registers (ClinicalTrials.gov and WHO International Clinical Trials Registry Platform) up to 25 September 2020. We contacted organizations for unpublished data. We checked the reference lists of trials identified by these methods. SELECTION CRITERIA We included experimental hut trials, village trials, and randomized controlled trials (RCTs) with mosquitoes from the Anopheles gambiae complex or the Anopheles funestus group. DATA COLLECTION AND ANALYSIS Two review authors assessed each trial for eligibility, extracted data, and determined the risk of bias for included trials. We resolved disagreements through discussion with a third review author. We analysed data using Review Manager 5 and assessed the certainty of evidence using the GRADE approach. MAIN RESULTS Sixteen trials met the inclusion criteria: 10 experimental hut trials, four village trials, and two cluster-RCTs (cRCTs). Three trials are awaiting classification, and four trials are ongoing. Two cRCTs examined the effects of pyrethroid-PBO nets on parasite prevalence in people living in areas with highly pyrethroid-resistant mosquitoes (< 30% mosquito mortality in discriminating dose assays). At 21 to 25 months post intervention, parasite prevalence was lower in the intervention arm (odds ratio (OR) 0.79, 95% confidence interval (CI) 0.67 to 0.95; 2 trials, 2 comparisons; moderate-certainty evidence). In highly pyrethroid-resistant areas, unwashed pyrethroid-PBO nets led to higher mosquito mortality compared to unwashed standard-LLINs (risk ratio (RR) 1.84, 95% CI 1.60 to 2.11; 14,620 mosquitoes, 5 trials, 9 comparisons; high-certainty evidence) and lower blood feeding success (RR 0.60, 95% CI 0.50 to 0.71; 14,000 mosquitoes, 4 trials, 8 comparisons; high-certainty evidence). However, in comparisons of washed pyrethroid-PBO nets to washed LLINs, we do not know if PBO nets had a greater effect on mosquito mortality (RR 1.20, 95% CI 0.88 to 1.63; 10,268 mosquitoes, 4 trials, 5 comparisons; very low-certainty evidence), although the washed pyrethroid-PBO nets did decrease blood-feeding success compared to standard-LLINs (RR 0.81, 95% CI 0.72 to 0.92; 9674 mosquitoes, 3 trials, 4 comparisons; high-certainty evidence). In areas where pyrethroid resistance is moderate (31% to 60% mosquito mortality), mosquito mortality was higher with unwashed pyrethroid-PBO nets compared to unwashed standard-LLINs (RR 1.68, 95% CI 1.33 to 2.11; 751 mosquitoes, 2 trials, 3 comparisons; moderate-certainty evidence), but there was little to no difference in effects on blood-feeding success (RR 0.90, 95% CI 0.72 to 1.11; 652 mosquitoes, 2 trials, 3 comparisons; moderate-certainty evidence). For washed pyrethroid-PBO nets compared to washed standard-LLINs, we found little to no evidence for higher mosquito mortality or reduced blood feeding (mortality: RR 1.07, 95% CI 0.74 to 1.54; 329 mosquitoes, 1 trial, 1 comparison, low-certainty evidence; blood feeding success: RR 0.91, 95% CI 0.74 to 1.13; 329 mosquitoes, 1 trial, 1 comparison; low-certainty evidence). In areas where pyrethroid resistance is low (61% to 90% mosquito mortality), studies reported little to no difference in the effects of unwashed pyrethroid-PBO nets compared to unwashed standard-LLINs on mosquito mortality (RR 1.25, 95% CI 0.99 to 1.57; 948 mosquitoes, 2 trials, 3 comparisons; moderate-certainty evidence), and we do not know if there was any effect on blood-feeding success (RR 0.75, 95% CI 0.27 to 2.11; 948 mosquitoes, 2 trials, 3 comparisons; very low-certainty evidence). For washed pyrethroid-PBO nets compared to washed standard-LLINs, we do not know if there was any difference in mosquito mortality (RR 1.39, 95% CI 0.95 to 2.04; 1022 mosquitoes, 2 trials, 3 comparisons; very low-certainty evidence) or on blood feeding (RR 1.07, 95% CI 0.49 to 2.33; 1022 mosquitoes, 2 trials, 3 comparisons; low-certainty evidence). In areas where mosquito populations are susceptible to insecticides (> 90% mosquito mortality), there may be little to no difference in the effects of unwashed pyrethroid-PBO nets compared to unwashed standard-LLINs on mosquito mortality (RR 1.20, 95% CI 0.64 to 2.26; 2791 mosquitoes, 2 trials, 2 comparisons; low-certainty evidence). This is similar for washed nets (RR 1.07, 95% CI 0.92 to 1.25; 2644 mosquitoes, 2 trials, 2 comparisons; low-certainty evidence). We do not know if unwashed pyrethroid-PBO nets had any effect on the blood-feeding success of susceptible mosquitoes (RR 0.52, 95% CI 0.12 to 2.22; 2791 mosquitoes, 2 trials, 2 comparisons; very low-certainty evidence). The same applies to washed nets (RR 1.25, 95% CI 0.82 to 1.91; 2644 mosquitoes, 2 trials, 2 comparisons; low-certainty evidence). In village trials comparing pyrethroid-PBO nets to LLINs, there was no difference in sporozoite rate (4 trials, 5 comparisons) nor in mosquito parity (3 trials, 4 comparisons). AUTHORS' CONCLUSIONS In areas of high insecticide resistance, pyrethroid-PBO nets have greater entomological and epidemiological efficacy compared to standard LLINs, with sustained reduction in parasite prevalence, higher mosquito mortality and reduction in mosquito blood feeding rates 21 to 25 months post intervention. Questions remain about the durability of PBO on nets, as the impact of pyrethroid-PBO nets on mosquito mortality was not sustained over 20 washes in experimental hut trials, and epidemiological data on pyrethroid-PBO nets for the full intended three-year life span of the nets is not available. Little evidence is available to support greater entomological efficacy of pyrethroid-PBO nets in areas where mosquitoes show lower levels of resistance to pyrethroids.
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Affiliation(s)
- Katherine Gleave
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Natalie Lissenden
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Marty Chaplin
- Department of Clinical Sciences, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Leslie Choi
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Hilary Ranson
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
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12
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Kilian A, Obi E, Mansiangi P, Abílio AP, Haji KA, Blaufuss S, Olapeju B, Babalola S, Koenker H. Variation of physical durability between LLIN products and net use environments: summary of findings from four African countries. Malar J 2021; 20:26. [PMID: 33413388 PMCID: PMC7791654 DOI: 10.1186/s12936-020-03549-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Accepted: 12/12/2020] [Indexed: 11/14/2022] Open
Abstract
Background Physical durability of long-lasting-insecticidal nets (LLIN) is an important aspect of the effectiveness of LLIN as a malaria prevention tool, but there is limited data on performance across locations and products. This secondary analysis of data from the VectorWorks project from 10 sites in four African countries involving six LLIN brands provides such data. Methods A total of 4672 campaign nets from 1976 households were recruited into prospective cohort studies 2–6 months after distribution through campaigns and followed for 3 years in Mozambique, Nigeria, DRC and Zanzibar, Tanzania. LLIN products included two 100 denier polyester LLIN (DawaPlus® 2.0, PermaNet® 2.0) distributed in five sites and four 150 denier polyethylene LLIN (Royal Sentry®, MAGNet®, DuraNet©, Olyset™ Net) distributed in five sites. Primary outcome was LLIN survival in serviceable condition and median survival in years. Net use environment and net care variables were collected during four household surveys. Determinants of physical durability were explored by survival analysis and Cox regression models with risk of failure starting with the first hanging of the net. Results Definite outcomes for physical durability were obtained for 75% of study nets. After 31 to 37 months survival in serviceable condition varied between sites by 63 percentage-points, from 17 to 80%. Median survival varied by 3.7 years, from 1.6 to 5.3 years. Similar magnitude of variation was seen for polyethylene and polyester LLIN and for the same brand. Cox regression showed increasing net care attitude in combination with exposure to net related messages to be the strongest explanatory variable of survival. However, differences between countries also remained significant. In contrast, no difference was seen for LLIN material types. Conclusions Variation in net use environment and net care is the main reason for differences in the physical durability of LLIN products in different locations. While some of these factors have been identified to work across countries, other factors remain poorly defined and further investigation is needed in this area. Grouping LLIN brands by similar textile characteristics, such as material or yarn strength, is insufficient to distinguish LLIN product performance suggesting a more differentiated, composite metric is needed.
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Affiliation(s)
- Albert Kilian
- PMI VectorWorks Project, Tropical Health LLP, Montagut, Spain.
| | - Emmanuel Obi
- PMI VectorWorks Project, Tropical Health LLP, Abuja, Nigeria
| | - Paul Mansiangi
- Ecole de Santé Publique, Université de Kinshasa, Kinshasa, Democratic Republic of Congo
| | | | - Khamis Ameir Haji
- Zanzibar Malaria Elimination Programme, Stone Town, Zanzibar, Tanzania
| | - Sean Blaufuss
- PMI VectorWorks Project, JHU Center for Communication Programs, Baltimore, MD, USA
| | - Bolanle Olapeju
- PMI VectorWorks Project, JHU Center for Communication Programs, Baltimore, MD, USA
| | - Stella Babalola
- PMI VectorWorks Project, JHU Center for Communication Programs, Baltimore, MD, USA
| | - Hannah Koenker
- PMI VectorWorks Project, JHU Center for Communication Programs, Baltimore, MD, USA
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13
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Traoré DF, Sagna AB, Assi SB, Tchiekoi BN, Adja AM, Dagnogo M, Koffi AA, Rogier C, Remoue F. Operational Evaluation of the Effectiveness of Long-lasting Insecticidal Nets on Human-Vector Contact in an African Urban Malaria Context. Open Forum Infect Dis 2020; 8:ofaa635. [PMID: 33553475 PMCID: PMC7850104 DOI: 10.1093/ofid/ofaa635] [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: 06/24/2020] [Accepted: 12/28/2020] [Indexed: 11/30/2022] Open
Abstract
Background Malaria is still a major public health concern in Côte d’Ivoire despite mass distribution of long-lasting insecticidal nets (LLINs) as a key preventive strategy. This study intended to evaluate the operational effectiveness of LLINs on the level of human-vector contact using 1 antibody-based biomarker of exposure to Anopheles in urban areas. Methods This cross-sectional study collected socio-demographic data and use of LLINs from 9 neighborhoods in the city of Bouaké (Côte d’Ivoire). Dry blood spots performed in children aged >6 months and adults were used to evaluate immunoglobulin G (IgG) responses to the Anopheles gSG6-P1 salivary peptide. Results IgG response levels to the salivary peptide were significantly lower in individuals who declared having “always” (n = 270) slept under an LLIN compared with those who had “often” (n = 2087) and “never” (n = 88) slept under an LLIN (P < .0001). IgG response levels to gSG6-P1 between those who declared having “always” and “not always” slept under an LLIN varied according to neighborhood, socio-professional category, and age group. Conclusions The human IgG level to this gSG6-P1 salivary peptide could be a useful tool to evaluate the actual effectiveness of LLINs and help design behavioral change interventions that are crucial for sustaining universal coverage.
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Affiliation(s)
- Dipomin F Traoré
- Institut Pierre Richet (IPR), Institut National de la Santé Publique (INSP), Bouaké, Côte d'Ivoire.,MIVEGEC, University of Montpellier, IRD, CNRS, Montpellier, France.,Unité de Formation et de Recherche en Sciences de la Nature (UFR SN), Université Nangui Abrogoua, Abidjan, Côte d'Ivoire
| | - André B Sagna
- Institut Pierre Richet (IPR), Institut National de la Santé Publique (INSP), Bouaké, Côte d'Ivoire.,MIVEGEC, University of Montpellier, IRD, CNRS, Montpellier, France
| | - Serge B Assi
- Institut Pierre Richet (IPR), Institut National de la Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | - Bertin N'Cho Tchiekoi
- Institut Pierre Richet (IPR), Institut National de la Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | - Akré M Adja
- Institut Pierre Richet (IPR), Institut National de la Santé Publique (INSP), Bouaké, Côte d'Ivoire.,Unité de Formation et de Recherche en Biosciences (UFR Biosciences), Université Félix Houphouët Boigny, Abidjan, Côte d'Ivoire
| | - Mamadou Dagnogo
- Unité de Formation et de Recherche en Sciences de la Nature (UFR SN), Université Nangui Abrogoua, Abidjan, Côte d'Ivoire
| | - Alphonsine A Koffi
- Institut Pierre Richet (IPR), Institut National de la Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | | | - Franck Remoue
- Institut Pierre Richet (IPR), Institut National de la Santé Publique (INSP), Bouaké, Côte d'Ivoire.,MIVEGEC, University of Montpellier, IRD, CNRS, Montpellier, France
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14
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Lorenz LM, Bradley J, Yukich J, Massue DJ, Mageni Mboma Z, Pigeon O, Moore J, Kilian A, Lines J, Kisinza W, Overgaard HJ, Moore SJ. Comparative functional survival and equivalent annual cost of 3 long-lasting insecticidal net (LLIN) products in Tanzania: A randomised trial with 3-year follow up. PLoS Med 2020; 17:e1003248. [PMID: 32946451 PMCID: PMC7500675 DOI: 10.1371/journal.pmed.1003248] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 08/17/2020] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Two billion long-lasting insecticidal nets (LLINs) have been procured for malaria control. A functional LLIN is one that is present, is in good physical condition, and remains insecticidal, thereby providing protection against vector-borne diseases through preventing bites and killing disease vectors. The World Health Organization (WHO) prequalifies LLINs that remain adequately insecticidal 3 years after deployment. Therefore, institutional buyers often assume that prequalified LLINs are functionally identical with a 3-year lifespan. We measured the lifespans of 3 LLIN products, and calculated their cost per year of functional life, to demonstrate the economic and public health importance of procuring the most cost-effective LLIN product based on its lifespan. METHODS AND FINDINGS A randomised double-blinded trial of 3 pyrethroid LLIN products (10,571 nets in total) was conducted at 3 follow-up points: 10 months (August-October 2014), 22 months (August-October 2015), and 36 months (October-December 2016) among 3,393 households in Tanzania using WHO-recommended methods. Primary outcome was LLIN functional survival (LLIN present and in serviceable condition). Secondary outcomes were (1) bioefficacy and chemical content (residual insecticidal activity) and (2) protective efficacy for volunteers sleeping under the LLINs (bite reduction and mosquitoes killed). Median LLIN functional survival was significantly different between the 3 net products (p = 0.001): 2.0 years (95% CI 1.7-2.3) for Olyset, 2.5 years (95% CI 2.2-2.8) for PermaNet 2.0 (hazard ratio [HR] 0.73 [95% CI 0.64-0.85], p = 0.001), and 2.6 years (95% CI 2.3-2.8) for NetProtect (HR = 0.70 [95% CI 0.62-0.77], p < 0.001). Functional survival was affected by accumulation of holes, leading to users discarding nets. Protective efficacy also significantly differed between products as they aged. Equivalent annual cost varied between US$1.2 (95% CI $1.1-$1.4) and US$1.5 (95% CI $1.3-$1.7), assuming that each net was priced identically at US$3. The 2 longer-lived nets (PermaNet and NetProtect) were 20% cheaper than the shorter-lived product (Olyset). The trial was limited to only the most widely sold LLINs in Tanzania. Functional survival varies by country, so the single country setting is a limitation. CONCLUSIONS These results suggest that LLIN functional survival is less than 3 years and differs substantially between products, and these differences strongly influence LLIN value for money. LLIN tendering processes should consider local expectations of cost per year of functional life and not unit price. As new LLIN products come on the market, especially those with new insecticides, it will be imperative to monitor their comparative durability to ensure that the most cost-effective products are procured for malaria control.
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Affiliation(s)
- Lena M. Lorenz
- Department of Disease Control, Faculty of Infectious and Tropical Diseases, London School of Hygiene &Tropical Medicine, London, United Kingdom
- Queen’s Medical Research Institute, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh, United Kingdom
| | - John Bradley
- MRC Tropical Epidemiology Group, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Joshua Yukich
- Department of Tropical Medicine, Tulane University School of Public Health and Tropical Medicine, New Orleans, Louisiana, United States of America
| | - Dennis J. Massue
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
- Vector Control Product Testing Unit, Ifakara Health Institute, Bagamoyo, Tanzania
- Epidemiology and Public Health Department, Swiss Institute of Tropical and Public Health, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Zawadi Mageni Mboma
- Department of Disease Control, Faculty of Infectious and Tropical Diseases, London School of Hygiene &Tropical Medicine, London, United Kingdom
- Ifakara Health Institute, Dar es Salaam, Tanzania
| | - Olivier Pigeon
- Plant Protection Products and Biocides Physico-chemistry and Residues Unit, Agriculture and Natural Environment Department, Walloon Agricultural Research Centre, Gembloux, Belgium
| | - Jason Moore
- Vector Control Product Testing Unit, Ifakara Health Institute, Bagamoyo, Tanzania
- Epidemiology and Public Health Department, Swiss Institute of Tropical and Public Health, Basel, Switzerland
| | | | - Jo Lines
- Department of Disease Control, Faculty of Infectious and Tropical Diseases, London School of Hygiene &Tropical Medicine, London, United Kingdom
| | - William Kisinza
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Hans J. Overgaard
- Faculty of Science and Technology, Norwegian University of Life Sciences, Ås, Norway
- Department of Microbiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand
| | - Sarah J. Moore
- Vector Control Product Testing Unit, Ifakara Health Institute, Bagamoyo, Tanzania
- Epidemiology and Public Health Department, Swiss Institute of Tropical and Public Health, Basel, Switzerland
- University of Basel, Basel, Switzerland
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15
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Ngufor C, Agbevo A, Fagbohoun J, Fongnikin A, Rowland M. Efficacy of Royal Guard, a new alpha-cypermethrin and pyriproxyfen treated mosquito net, against pyrethroid-resistant malaria vectors. Sci Rep 2020; 10:12227. [PMID: 32699237 PMCID: PMC7376134 DOI: 10.1038/s41598-020-69109-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Accepted: 07/06/2020] [Indexed: 11/10/2022] Open
Abstract
Royal Guard is a new insecticide-treated bed-net incorporated with a mixture of alpha-cypermethrin and pyriproxyfen (an insect growth regulator). We assessed its efficacy and wash-resistance in laboratory and experimental hut studies following WHO guidelines. Mosquitoes that survived exposure to the net were kept in separate oviposition chambers and observed for the reproductive effects of pyriproxyfen. In laboratory assays, Royal Guard induced > 80% mortality and > 90% blood-feeding inhibition of An. gambiae sl mosquitoes before and after 20 standardised washes and sterilised blood-fed mosquitoes which remained alive after exposure to the net. In an experimental hut trial against wild free-flying pyrethroid-resistant An. gambiae sl in Cové Benin, Royal Guard through the pyrethroid component induced comparable levels of mortality and blood-feeding inhibition to a standard pyrethroid-only treated net before and after 20 washes and sterilised large proportions of surviving blood-fed female mosquitoes through the pyriproxyfen component; Royal Guard induced 83% reduction in oviposition and 95% reduction in offspring before washing and 25% reduction in oviposition and 50% reduction in offspring after 20 washes. Royal Guard has the potential to improve malaria vector control and provide better community protection against clinical malaria in pyrethroid-resistant areas compared to standard pyrethroid-only LLINs.
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Affiliation(s)
- Corine Ngufor
- London School of Hygiene and Tropical Medicine (LSHTM), London, UK. .,Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin. .,Pan African Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin.
| | - Abel Agbevo
- Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin.,Pan African Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
| | - Josias Fagbohoun
- Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin.,Pan African Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
| | - Augustin Fongnikin
- Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin.,Pan African Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
| | - Mark Rowland
- London School of Hygiene and Tropical Medicine (LSHTM), London, UK.,Pan African Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
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16
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Hughes A, Lissenden N, Viana M, Toé KH, Ranson H. Anopheles gambiae populations from Burkina Faso show minimal delayed mortality after exposure to insecticide-treated nets. Parasit Vectors 2020; 13:17. [PMID: 31924276 PMCID: PMC6954553 DOI: 10.1186/s13071-019-3872-2] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 12/29/2019] [Indexed: 01/02/2023] Open
Abstract
Background The efficacy of long-lasting insecticidal nets (LLINs) in preventing malaria in Africa is threatened by insecticide resistance. Bioassays assessing 24-hour mortality post-LLIN exposure have established that resistance to the concentration of pyrethroids used in LLINs is widespread. However, although mosquitoes may no longer be rapidly killed by LLIN exposure, a delayed mortality effect has been shown to reduce the transmission potential of mosquitoes exposed to nets. This has been postulated to partially explain the continued efficacy of LLINs against pyrethroid-resistant populations. Burkina Faso is one of a number of countries with very high malaria burdens and pyrethroid-resistant vectors, where progress in controlling this disease has stagnated. We measured the impact of LLIN exposure on mosquito longevity in an area of the country with intense pyrethroid resistance to establish whether pyrethroid exposure was still shortening mosquito lifespan in this setting. Methods We quantified the immediate and delayed mortality effects of LLIN exposure using standard laboratory WHO cone tests, tube bioassays and experimental hut trials on Anopheles gambiae populations originating from the Cascades region of Burkina Faso using survival analysis and a Bayesian state-space model. Results Following single and multiple exposures to a PermaNet 2.0 LLIN only one of the four mosquito populations tested showed evidence of delayed mortality. No delayed mortality was seen in experimental hut studies using LLINs. A delayed mortality effect was only observed in WHO tube bioassays when deltamethrin concentration was increased above the standard diagnostic dose. Conclusions As mosquito pyrethroid-resistance increases in intensity, delayed effects from LLIN exposure are substantially reduced or absent. Given the rapid increase in resistance occurring in malaria vectors across Africa it is important to determine whether the failure of LLINs to shorten mosquito lifespan is now a widespread phenomenon as this will have important implications for the future of this pivotal malaria control tool.![]()
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Affiliation(s)
- Angela Hughes
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Natalie Lissenden
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Mafalda Viana
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Kobié Hyacinthe Toé
- Centre National de Recherche et de Formation sur le Paludisme, 01 BP 2208, Ouagadougou 01, Burkina Faso
| | - Hilary Ranson
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK.
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17
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Chowdhury R, Chowdhury V, Faria S, Akter S, Dash AP, Bhattacharya SK, Maheswary NP, Bern C, Akhter S, Alvar J, Kroeger A, Boelaert M, Banu Q. Effect of insecticide-treated bed nets on visceral leishmaniasis incidence in Bangladesh. A retrospective cohort analysis. PLoS Negl Trop Dis 2019; 13:e0007724. [PMID: 31525195 PMCID: PMC6762203 DOI: 10.1371/journal.pntd.0007724] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Revised: 09/26/2019] [Accepted: 08/21/2019] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Visceral leishmaniasis (VL) is a parasitic disease, transmitted by the sand fly species Phlebotomus argentipes in the Indian sub-continent. Effective vector control is highly desirable to reduce vector density and human and vector contact in the endemic communities with the aim to curtail disease transmission. We evaluated the effect of long lasting insecticide treated bed nets (LLIN) and bed nets impregnated with slow-release insecticide tablet K-O TAB 1-2-3 (jointly insecticide-treated nets or ITN) on VL incidence in a highly endemic sub-district (upazila) in Bangladesh. METHODS Several distributions of LLIN or K-O TAB 1-2-3 for self-impregnation of bed nets at home took place in Fulbaria upazila, Mymensigh district from 2004 to 2008 under three research projects, respectively funded by CDC, Atlanta, USA (2004) and WHO-TDR, Geneva, Switzerland (2006 & 2008). We included all households (n = 8142) in the 20 villages that had benefited in the past from one of these interventions (1295 donated LLIN and 11,918 local bed nets impregnated with K-O TAB 1-2-3) in the "exposed cohort". We recruited a "non-exposed cohort" in villages with contemporaneously similar incidence rates who had not received such vector control interventions (7729 HHs from nine villages). In both cohorts, we visited all families house to house and ascertained any VL cases for the 3 year period before and after the intervention. We evaluated the incidence rate (IR) of VL in both cohorts as primary endpoint, applying the difference-in-differences method. RESULTS The study identified 1011 VL cases (IR 140.47/10,000 per year [py]) before the intervention, of which 534 and 477 cases in the intervention and control areas respectively. The IR was 144.13/10,000 py (534/37050) and 136.59/10,000 py (477/34923) in the intervention and control areas respectively, with no significant difference (p = 0.3901) before the intervention. After the intervention, a total of 555 cases (IR 77.11/10,000 py) were identified of which 178 (IR 48.04/10,000 py) in the intervention and 377 (107.95/10,000 py) in the control area. The intervention area had a significant lower IR than the control area during follow up, rate difference = -59.91, p<0.0001. The IR during follow up was significantly reduced by 96.09/10,000 py in the intervention area (p<0.0001) and 28.63/10,000 py in control area (p<0.0001) compared to baseline. There was a strong and significant overall effect of the ITN intervention, δ = -67.45, p <0.0001. Sex (OR = 1.36, p<0.0001) and age (OR = 0.99, p<0.0001) also had a significant effect on VL incidence. Male had a higher risk of VL than female and one year increase in age decreased the likelihood of VL by about 0.92%. Two third of the VL incidence occurred in the age range 2 to 30 years (median age of VL patients was 17 years). CONCLUSION VL incidence rate was significantly lower in the ITN intervention cohort compared to control in Bangladesh. Some bias due to more intense screen-and-treat activities or other interventions in the intervention area cannot be ruled out. Nonetheless, given their feasibility and sustainability, ITNs should be considered for integrated vector control during the maintenance phase of the VL elimination programme.
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Affiliation(s)
- Rajib Chowdhury
- International Center for Diarrhoea Disease Research, Bangladesh (icddr,b), Mohakhali, Bangladesh
- National Institute of Preventive and Social Medicine, Mohakhali, Bangladesh
| | | | - Shyla Faria
- Directorate General of Health Services (DGHS), Mohakhali, Bangladesh
| | - Sakila Akter
- National Institute of Preventive and Social Medicine, Mohakhali, Bangladesh
| | | | | | | | - Caryn Bern
- UCSF School of Medicine, San Francisco California, United States of America
| | - Shireen Akhter
- National Institute of Preventive and Social Medicine, Mohakhali, Bangladesh
| | - Jorge Alvar
- Drugs for Neglected Diseases initiative (DNDi), Geneva, Switzerland
| | - Axel Kroeger
- Special Programme for Research and Training in Tropical Diseases, World Health Organization, Geneva, Switzerland
- University of Freiburg, Centre for Medicine and Society/Anthropology, Freiburg, Germany
| | | | - Qamar Banu
- Asian University for Women, Chittatong, Bangladesh
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In vitro acaricidal effect of Melia azedarach and Artemisia herba- alba extracts on Hyalomma dromedarii (Acari: Ixodidae): embryonated eggs and engorged nymphs. J Parasit Dis 2019; 43:696-710. [PMID: 31749542 DOI: 10.1007/s12639-019-01149-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2019] [Accepted: 08/09/2019] [Indexed: 10/26/2022] Open
Abstract
The present study aimed to evaluate the in vitro efficacy of four medicinal plant extracts: petroleum ether and ethyl alcohol extracts of the ripen fruits of Melia azedarach and whole aerial parts of Artemisia herba-alba against the two inactive stages of the camel tick Hyalomma dromedarii, embryonated eggs and engorged nymphs in comparison to reference acaricide Butox®5.0 (Deltamethrin). Egg and nymphal immersion tests at four concentrations with three replicates were used. The deformity in larvae hatched from treated eggs and adults moulted from treated nymphs were observed and photographed by light microscope (LM) and scanning electron microscope (SEM). The results showed that M. azedarach and A. herba-alba extracts revealed higher significant toxic effects on embryonated eggs and engorged nymphs comparing with the reference acaricide (Butox®5.0) and control. In egg emmersion test, the LC50 of petroleum ether extracts of M. azedarach and A. herba-alba was 3.14 and 3.91%, respectively and LC50 of the respective ethyl alcohol extracts was 1.77 and 2.45%. In nymphal immersion test, LC50 of petroleum ether extracts of M. azedarach and A. herba-alba was 0.26 and 1%, respectively, and LC50 of the respective ethyl alcohol extracts was 4.17 and 8.7%. Abnormalities were observed by LM and SEM in the larvae hatched from the treated eggs as incomplete development of legs and mouth parts as well as shrinkage mainly in legs and mouthparts of adults emerged from treated nymphs. In conclusion, all extracts and petroleum ether extracts of the two plants have great potential to be developed as a novel acaricidal for controlling eggs and nymphs of H. dromedarii, respectively.
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Traoré DF, Sagna AB, Adja AM, Zoh DD, Adou KA, Lingué KN, Coulibaly I, Tchiekoi NB, Assi SB, Poinsignon A, Dagnogo M, Remoue F. Exploring the heterogeneity of human exposure to malaria vectors in an urban setting, Bouaké, Côte d'Ivoire, using an immuno-epidemiological biomarker. Malar J 2019; 18:68. [PMID: 30857543 PMCID: PMC6413440 DOI: 10.1186/s12936-019-2696-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Accepted: 03/01/2019] [Indexed: 11/24/2022] Open
Abstract
Background In some African cities, urban malaria is a threat to the health and welfare of city dwellers. To improve the control of the disease, it is critical to identify neighbourhoods where the risk of malaria transmission is the highest. This study aims to evaluate the heterogeneity of malaria transmission risk in one city (Bouaké) in a West African country (Côte d’Ivoire) that presents several levels of urbanization. Methods Two cross-sectional studies were conducted in three neighbourhoods (Dar-es-Salam, Kennedy and N’gattakro) in Bouaké during both the rainy and dry seasons. Data on insecticide-treated net (ITN) use and blood samples were collected from children aged between 6 months and 15 years to determine the parasite density and the prevalence of Plasmodium falciparum and the level of IgG against the Anopheles gSG6-P1 salivary peptide, used as the biomarker of Anopheles bite exposure. Results The specific IgG levels to the gSG6-P1 salivary peptide in the rainy season were significantly higher compared to the dry season in all neighbourhoods studied (all p < 0.001). Interestingly, these specific IgG levels did not differ between neighbourhoods during the rainy season, whereas significant differences in IgG level were observed in the dry season (p = 0.034). ITN use could be a major factor of variation in the specific IgG level. Nevertheless, no difference in specific IgG levels to the gSG6-P1 salivary peptide was observed between children who declared “always” versus “never” sleeping under an ITN in each neighbourhood. In addition, the prevalence of P. falciparum in the whole population and immune responders was significantly different between neighbourhoods in each season (p < 0.0001). Conclusion This study highlights the high risk of malaria exposure in African urban settings and the high heterogeneity of child exposure to the Anopheles vector between neighbourhoods in the same city. The Anopheles gSG6-P1 salivary peptide could be a suitable biomarker to accurately and quantitatively assess the risk of malaria transmission in urban areas. Electronic supplementary material The online version of this article (10.1186/s12936-019-2696-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Dipomin F Traoré
- Institut Pierre Richet (IPR), Institut National de la Santé Publique (INSP), Bouaké, Côte d'Ivoire. .,MIVEGEC, Univ. Montpellier, CNRS, IRD, Montpellier, France. .,Unité de Formation et de Recherche en Sciences de la nature (UFR SN), Université Nangui Abrogoua, Abidjan, Côte d'Ivoire.
| | - André B Sagna
- Institut Pierre Richet (IPR), Institut National de la Santé Publique (INSP), Bouaké, Côte d'Ivoire.,MIVEGEC, Univ. Montpellier, CNRS, IRD, Montpellier, France
| | - Akré M Adja
- Institut Pierre Richet (IPR), Institut National de la Santé Publique (INSP), Bouaké, Côte d'Ivoire.,Unité de Formation et de Recherche en Biosciences (UFR Biosciences), Université Félix Houphouët Boigny, Abidjan, Côte d'Ivoire
| | - Dounin D Zoh
- Institut Pierre Richet (IPR), Institut National de la Santé Publique (INSP), Bouaké, Côte d'Ivoire.,Unité de Formation et de Recherche en Biosciences (UFR Biosciences), Université Félix Houphouët Boigny, Abidjan, Côte d'Ivoire
| | - Kouassi A Adou
- Institut Pierre Richet (IPR), Institut National de la Santé Publique (INSP), Bouaké, Côte d'Ivoire.,Institut de Géographie Tropicale (IGT), Université Félix Houphouët Boigny, Abidjan, Côte d'Ivoire
| | - Kouassi N Lingué
- Institut Pierre Richet (IPR), Institut National de la Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | - Issa Coulibaly
- Institut Pierre Richet (IPR), Institut National de la Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | - N'Cho Bertin Tchiekoi
- Institut Pierre Richet (IPR), Institut National de la Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | - Serge B Assi
- Institut Pierre Richet (IPR), Institut National de la Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | - Anne Poinsignon
- Institut Pierre Richet (IPR), Institut National de la Santé Publique (INSP), Bouaké, Côte d'Ivoire.,MIVEGEC, Univ. Montpellier, CNRS, IRD, Montpellier, France
| | - Mamadou Dagnogo
- Unité de Formation et de Recherche en Sciences de la nature (UFR SN), Université Nangui Abrogoua, Abidjan, Côte d'Ivoire
| | - Franck Remoue
- Institut Pierre Richet (IPR), Institut National de la Santé Publique (INSP), Bouaké, Côte d'Ivoire.,MIVEGEC, Univ. Montpellier, CNRS, IRD, Montpellier, France
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Gleave K, Lissenden N, Richardson M, Choi L, Ranson H. Piperonyl butoxide (PBO) combined with pyrethroids in insecticide-treated nets to prevent malaria in Africa. Cochrane Database Syst Rev 2018; 11:CD012776. [PMID: 30488945 PMCID: PMC6262905 DOI: 10.1002/14651858.cd012776.pub2] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
BACKGROUND Public health strategies that target mosquito vectors, particularly pyrethroid long-lasting insecticidal nets (LLINs), have been largely responsible for the substantial reduction in the number of people in Africa developing malaria. The spread of insecticide resistance in Anopheles mosquitoes threatens these impacts. One way to control insecticide-resistant populations is by using insecticide synergists. Piperonyl butoxide (PBO) is a synergist that inhibits specific metabolic enzymes within mosquitoes and has been incorporated into pyrethroid-LLINs to form pyrethroid-PBO nets. Pyrethroid-PBO nets are currently produced by four LLIN manufacturers and, following a recommendation from the World Health Organization (WHO) in 2017, are being included in distribution campaigns in countries. This review examines epidemiological and entomological evidence on whether the addition of PBO to LLINs improves their efficacy. OBJECTIVES 1. Evaluate whether adding PBO to pyrethroid LLINs increases the epidemiological and entomological effectiveness of the nets.2. Compare the effects of pyrethroid-PBO nets currently in commercial development or on the market with their non-PBO equivalent in relation to:a. malaria infection (prevalence or incidence);b. entomological outcomes. SEARCH METHODS We searched the Cochrane Infectious Diseases Group (CIDG) Specialized Register; CENTRAL, MEDLINE, Embase, Web of Science, CAB Abstracts, and two clinical trial registers (ClinicalTrials.gov and WHO International Clinical Trials Registry Platform) up to 24 August 2018. We contacted organizations for unpublished data. We checked the reference lists of trials identified by the above methods. SELECTION CRITERIA We included laboratory trials, experimental hut trials, village trials, and randomized clinical trials with mosquitoes from the Anopheles gambiae complex or Anopheles funestus group. DATA COLLECTION AND ANALYSIS Two review authors assessed each trial for eligibility, extracted data, and determined the risk of bias for included trials. We resolved disagreements through discussion with a third review author. We analysed the data using Review Manager 5 and assessed the certainty of the evidence using the GRADE approach. MAIN RESULTS Fifteen trials met the inclusion criteria: two laboratory trials, eight experimental hut trials, and five cluster-randomized controlled village trials.One village trial examined the effect of pyrethroid-PBO nets on malaria infection prevalence in an area with highly pyrethroid-resistant mosquitoes. The latest endpoint at 21 months post-intervention showed that malaria prevalence probably decreased in the intervention arm (OR 0.40, 95% CI 0.20 to 0.80; 1 trial, 1 comparison, moderate-certainty evidence).In highly pyrethroid-resistant areas (< 30% mosquito mortality), in comparisons of unwashed pyrethroid-PBO nets to unwashed standard-LLINs, PBO nets resulted in higher mosquito mortality (risk ratio (RR) 1.84, 95% CI 1.60 to 2.11; 14,620 mosquitoes, 5 trials, 9 comparisons, high-certainty evidence) and lower blood feeding success (RR 0.60, 95% CI 0.50 to 0.71; 14,000 mosquitoes, 4 trials, 8 comparisons, high-certainty evidence). However, in comparisons of washed pyrethroid-PBO nets to washed LLINs we do not know if PBO nets have a greater effect on mosquito mortality (RR 1.20, 95% CI 0.88 to 1.63; 10,268 mosquitoes, 4 trials, 5 comparisons, very low-certainty evidence), although the washed pyrethroid-PBO nets do decrease blood feeding success compared to standard-LLINs (RR 0.81, 95% CI 0.72 to 0.92; 9674 mosquitoes, 3 trials, 4 comparisons, high-certainty evidence).In areas where pyrethroid resistance is considered moderate (31% to 60% mosquito mortality), there may be little or no difference in effects of unwashed pyrethroid-PBO nets compared to unwashed standard-LLINs on mosquito mortality (RR 1.16, 95% CI 0.88 to 1.54; 242 mosquitoes, 1 trial, 1 comparison, low-certainty evidence), and there may be little or no difference in the effects on blood feeding success (RR 0.87, 95% CI 0.67 to 1.13; 242 mosquitoes, 1 trial, 1 comparison, low-certainty evidence). The same pattern is apparent for washed pyrethroid-PBO nets compared to washed standard-LLINs (mortality: RR 1.07, 95% CI 0.74 to 1.54; 329 mosquitoes, 1 trial, 1 comparison, low-certainty evidence; blood feeding success: RR 0.91, 95% CI 0.74 to 1.13; 329 mosquitoes, 1 trial, 1 comparison, low-certainty evidence).In areas where pyrethroid resistance is low (61% to 90% mosquito mortality), there is probably little or no difference in the effect of unwashed pyrethroid-PBO nets compared to unwashed standard-LLINs on mosquito mortality (RR 1.10, 95% CI 1.05 to 1.16; 708 mosquitoes, 1 trial, 2 comparisons, moderate-certainty evidence), but there is no evidence for an effect on blood feeding success (RR 0.67, 95% CI 0.06 to 7.37; 708 mosquitoes, 1 trial, 2 comparisons, very low-certainty evidence). For washed pyrethroid-PBO nets compared to washed standard-LLINs we do not know if there is any difference in mosquito mortality (RR 1.16, 96% CI 0.83 to 1.63; 878 mosquitoes, 1 trial, 2 comparisons, very low-certainty evidence), but blood feeding may decrease (RR 1.50, 95% CI 0.89 to 2.54; 878 mosquitoes, 1 trial, 2 comparisons, low-certainty evidence).In areas were mosquito populations are susceptible to insecticides (> 90% mosquito mortality), there may be little or no difference in the effect of unwashed pyrethroid-PBO nets compared to unwashed standard-LLINs on mosquito mortality (RR 1.20, 95% CI 0.64 to 2.26; 2791 mosquitoes, 2 trials, 2 comparisons, low-certainty evidence). This is similar for washed nets (RR 1.07, 95% CI 0.92 to 1.25; 2644 mosquitoes, 2 trials, 2 comparisons, low-certainty evidence). We do not know if unwashed pyrethroid-PBO nets have any effect on blood feeding success of susceptible mosquitoes (RR 0.50, 95% CI 0.11 to 2.32; 2791 mosquitoes, 2 trials, 2 comparisons, very low-certainty evidence). The same applies to washed nets (RR 1.28, 95% CI 0.81 to 2.04; 2644 mosquitoes, 2 trials, 2 comparisons, low-certainty evidence).In village trials comparing pyrethroid-PBO nets to LLINs, there was no difference in sporozoite rate (4 trials, 5 comparison) and mosquito parity (3 trials, 4 comparisons). AUTHORS' CONCLUSIONS In areas of high insecticide resistance, pyrethroid-PBO nets reduce mosquito mortality and blood feeding rates, and results from a single clinical trial demonstrate that this leads to lower malaria prevalence. Questions remain about the durability of PBO on nets, as the impact of pyrethroid-PBO LLINs on mosquito mortality was not sustained over 20 washes in experimental hut trials. There is little evidence to support higher entomological efficacy of pyrethroid-PBO nets in areas where the mosquitoes show lower levels of resistance to pyrethroids.
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Affiliation(s)
- Katherine Gleave
- Liverpool School of Tropical MedicineDepartment of Vector BiologyPembroke PlaceLiverpoolUKL3 5QA
| | - Natalie Lissenden
- Liverpool School of Tropical MedicineDepartment of Vector BiologyPembroke PlaceLiverpoolUKL3 5QA
| | - Marty Richardson
- Liverpool School of Tropical MedicineDepartment of Clinical SciencesPembroke PlaceLiverpoolUKL3 5QA
| | - Leslie Choi
- Liverpool School of Tropical MedicineDepartment of Clinical SciencesPembroke PlaceLiverpoolUKL3 5QA
| | - Hilary Ranson
- Liverpool School of Tropical MedicineDepartment of Vector BiologyPembroke PlaceLiverpoolUKL3 5QA
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Levitz L, Janko M, Mwandagalirwa K, Thwai KL, Likwela JL, Tshefu AK, Emch M, Meshnick SR. Effect of individual and community-level bed net usage on malaria prevalence among under-fives in the Democratic Republic of Congo. Malar J 2018; 17:39. [PMID: 29347953 PMCID: PMC5774036 DOI: 10.1186/s12936-018-2183-y] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Accepted: 01/10/2018] [Indexed: 11/10/2022] Open
Abstract
Background Understanding the contribution of community-level long-lasting, insecticidal net (LLIN) coverage to malaria control is critical to planning and assessing intervention campaigns. The Democratic Republic of Congo (DRC), which has one of the highest burdens of malaria cases and deaths and has dramatically scaled up LLIN ownership in recent years thus it is an ideal setting to evaluate the effect of individual versus community-level use to prevent malaria among children under the age of 5. Results Data were derived from the 2013–2014 DRC Demographic and Health Survey. Community-level LLIN usage was significantly associated with protection against malaria, even when individual-level LLIN usage was included in the model. In stratified analysis, higher levels of community LLIN coverage enhanced the protective effect of individual LLIN usage, resulting in lower malaria prevalence among individuals who used a LLIN. A sub-analysis of individual LLIN usage by insecticide type revealed deltamethrin-treated nets were more protective than permethrin-treated nets, suggesting that mosquitoes in the DRC are more susceptible to deltamethrin. Conclusions This study examines the effects of individual and community-level LLIN usage in young children in an area of high ITN usage. Individual and community LLIN usage were significantly associated with protection against malaria in children under 5 in the DRC. Importantly, the protective effect of individual LLIN usage against malaria is enhanced when community LLIN coverage is higher, demonstrating the importance of increasing community-level LLIN usage. LLINs treated with deltamethrin were shown to be more protective against malaria than LLINs treated with permethrin. Demographic and Health Surveys are thus a novel and important means of surveillance for insecticide resistance.
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Affiliation(s)
- Lauren Levitz
- Department of Epidemiology, University of North Carolina, Gillings School of Global Public Health, 135 Dauer Drive, 3113 Michael Hooker Research Building, Chapel Hill, NC, 27599, USA
| | - Mark Janko
- Department of Geography, University of North Carolina Gillings School of Global Public Health, Chapel Hill, NC, 27599, USA
| | | | - Kyaw L Thwai
- Department of Epidemiology, University of North Carolina, Gillings School of Global Public Health, 135 Dauer Drive, 3113 Michael Hooker Research Building, Chapel Hill, NC, 27599, USA
| | - Joris L Likwela
- Programme National de la Lutte contre le Paludisme, Kinshasa, Democratic Republic of Congo
| | - Antoinette K Tshefu
- University of Kinshasa School of Public Health, Kinshasa, Democratic Republic of Congo
| | - Michael Emch
- Department of Geography, University of North Carolina Gillings School of Global Public Health, Chapel Hill, NC, 27599, USA
| | - Steven R Meshnick
- Department of Epidemiology, University of North Carolina, Gillings School of Global Public Health, 135 Dauer Drive, 3113 Michael Hooker Research Building, Chapel Hill, NC, 27599, USA.
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22
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Ssempiira J, Nambuusi B, Kissa J, Agaba B, Makumbi F, Kasasa S, Vounatsou P. The contribution of malaria control interventions on spatio-temporal changes of parasitaemia risk in Uganda during 2009-2014. Parasit Vectors 2017; 10:450. [PMID: 28964263 PMCID: PMC5622426 DOI: 10.1186/s13071-017-2393-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Accepted: 09/19/2017] [Indexed: 11/21/2022] Open
Abstract
BACKGROUND In Uganda, malaria vector control interventions and case management with Artemisinin Combination Therapies (ACTs) have been scaled up over the last few years as a result of increased funding. Data on parasitaemia prevalence among children less than 5 years old and coverage of interventions was collected during the first two Malaria Indicator Surveys (MIS) conducted in 2009 and 2014, respectively. In this study, we quantify the effects of control interventions on parasitaemia risk changes between the two MIS in a spatio-temporal analysis. METHODS Bayesian geostatistical and temporal models were fitted on the MIS data of 2009 and 2014. The models took into account geographical misalignment in the locations of the two surveys and adjusted for climatic changes and socio-economic differentials. Parasitaemia risk was predicted over a 2 × 2 km2 grid and the number of infected children less than 5 years old was estimated. Geostatistical variable selection was applied to identify the most important ITN coverage indicators. A spatially varying coefficient model was used to estimate intervention effects at sub-national level. RESULTS The coverage of Insecticide Treated Nets (ITNs) and ACTs more than doubled at country and sub-national levels during the period 2009-2014. The coverage of Indoor Residual Spraying (IRS) remained static at all levels. ITNs, IRS, and ACTs were associated with a reduction in parasitaemia odds of 19% (95% BCI: 18-29%), 78% (95% BCI: 67-84%), and 34% (95% BCI: 28-66%), respectively. Intervention effects varied with region. Higher socio-economic status and living in urban areas were associated with parasitaemia odds reduction of 46% (95% BCI: 0.51-0.57) and 57% (95% BCI: 0.40-0.53), respectively. The probability of parasitaemia risk decline in the country was 85% and varied from 70% in the North-East region to 100% in Kampala region. The estimated number of children infected with malaria declined from 2,480,373 in 2009 to 825,636 in 2014. CONCLUSIONS Interventions have had a strong effect on the decline of parasitaemia risk in Uganda during 2009-2014, albeit with varying magnitude in the regions. This success should be sustained by optimizing ITN coverage to achieve universal coverage.
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Affiliation(s)
- Julius Ssempiira
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
- Makerere University School of Public Health, Kampala, Uganda
| | - Betty Nambuusi
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
- Makerere University School of Public Health, Kampala, Uganda
| | | | | | | | - Simon Kasasa
- Makerere University School of Public Health, Kampala, Uganda
| | - Penelope Vounatsou
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
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23
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Hershey CL, Florey LS, Ali D, Bennett A, Luhanga M, Mathanga DP, Salgado SR, Nielsen CF, Troell P, Jenda G, Yé Y, Bhattarai A. Malaria Control Interventions Contributed to Declines in Malaria Parasitemia, Severe Anemia, and All-Cause Mortality in Children Less Than 5 Years of Age in Malawi, 2000-2010. Am J Trop Med Hyg 2017; 97:76-88. [PMID: 28990920 PMCID: PMC5619935 DOI: 10.4269/ajtmh.17-0203] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Accepted: 05/30/2017] [Indexed: 12/01/2022] Open
Abstract
Malaria control intervention coverage increased nationwide in Malawi during 2000-2010. Trends in intervention coverage were assessed against trends in malaria parasite prevalence, severe anemia (hemoglobin < 8 g/dL), and all-cause mortality in children under 5 years of age (ACCM) using nationally representative household surveys. Associations between insecticide-treated net (ITN) ownership, malaria morbidity, and ACCM were also assessed. Household ITN ownership increased from 27.4% (95% confidence interval [CI] = 25.9-29.0) in 2004 to 56.8% (95% CI = 55.6-58.1) in 2010. Similarly intermittent preventive treatment during pregnancy coverage increased from 28.2% (95% CI = 26.7-29.8) in 2000 to 55.0% (95% CI = 53.4-56.6) in 2010. Malaria parasite prevalence decreased significantly from 60.5% (95% CI = 53.0-68.0) in 2001 to 20.4% (95% CI = 15.7-25.1) in 2009 in children aged 6-35 months. Severe anemia prevalence decreased from 20.4% (95% CI: 17.3-24.0) in 2004 to 13.1% (95% CI = 11.0-15.4) in 2010 in children aged 6-23 months. ACCM decreased 41%, from 188.6 deaths per 1,000 live births (95% CI = 179.1-198.0) during 1996-2000, to 112.1 deaths per 1,000 live births (95% CI = 105.8-118.5) during 2006-2010. When controlling for other covariates in random effects logistic regression models, household ITN ownership was protective against malaria parasitemia in children (odds ratio [OR] = 0.81, 95% CI = 0.72-0.92) and severe anemia (OR = 0.82, 95% CI = 0.72-0.94). After considering the magnitude of changes in malaria intervention coverage and nonmalaria factors, and given the contribution of malaria to all-cause mortality in malaria-endemic countries, the substantial increase in malaria control interventions likely improved child survival in Malawi during 2000-2010.
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Affiliation(s)
- Christine L. Hershey
- President’s Malaria Initiative, Agency for International Development, Washington, District of Columbia
| | - Lia S. Florey
- The DHS Program, ICF International, Rockville, Maryland
| | - Doreen Ali
- National Malaria Control Program, Lilongwe, Malawi
| | - Adam Bennett
- Global Health Group, University of California San Francisco School of Medicine, San Francisco, California
| | | | | | - S. René Salgado
- President’s Malaria Initiative, Agency for International Development, Washington, District of Columbia
| | - Carrie F. Nielsen
- President’s Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia
| | - Peter Troell
- President’s Malaria Initiative, Centers for Disease Control and Prevention, Lilongwe, Malawi
| | - Gomezgani Jenda
- President’s Malaria Initiative, Agency for International Development, Lilongwe, Malawi
| | - Yazoume Yé
- MEASURE Evaluation, ICF International, Rockville, Maryland
| | - Achuyt Bhattarai
- President’s Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia
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Escamilla V, Alker A, Dandalo L, Juliano JJ, Miller WC, Kamthuza P, Tembo T, Tegha G, Martinson F, Emch M, Hoffman IF. Effects of community-level bed net coverage on malaria morbidity in Lilongwe, Malawi. Malar J 2017; 16:142. [PMID: 28388914 PMCID: PMC5383956 DOI: 10.1186/s12936-017-1767-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Accepted: 03/08/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The protective effect of insecticide-treated bed nets against individual-level malaria transmission is well known, however community-level effects are less understood. Protective effects from community-level bed net use against malaria transmission have been observed in clinical trials, however, the relationship is less clear outside of a controlled research setting. The objective of this research was to investigate the effect of community-level bed net use against malaria transmission outside of a bed net clinical trial setting in Lilongwe, Malawi following national efforts to scale-up ownership of long-lasting, insecticide-treated bed nets. METHODS An annual, cross-sectional, household-randomized, malaria transmission intensity survey was conducted in Lilongwe, Malawi (2011-2013). Health, demographic, and geographic-location data were collected. Participant blood samples were tested for Plasmodium falciparum presence. The percentage of people sleeping under a bed net within 400-m and 1-km radii of all participants was measured. Mixed effects logistic regression models were used to measure the relationship between malaria prevalence and surrounding bed net coverage. Each year, 800 people were enrolled (400 <5 years; 200 5-19 years; 200 ≥20 years; total n = 2400). RESULTS From 2011 to 2013, malaria prevalence declined from 12.9 to 5.6%, while bed net use increased from 53.8 to 78.6%. For every 1% increase in community bed net coverage, malaria prevalence decreased among children under 5 years old [adjusted odds ratio: 0.98 (0.96, 1.00)]. Similar effects were observed in participants 5-19 years [unadjusted odds ratio: 0.98 (0.97, 1.00)]; the effect was attenuated after adjusting for individual-level bed net use. Community coverage was not associated with malaria prevalence among adults ≥20 years. Supplemental analyses identified more pronounced indirect protective effects from community-level bed net use against malaria transmission among children under 5 years who were sleeping under a bed net [adjusted odds ratio: 0.97 (0.94, 0.99)], compared to children who were not sleeping under a bed net [adjusted odds ratio: 0.99 (0.97, 1.01)]. CONCLUSIONS Malawi's efforts to scale up ownership of long-lasting, insecticide-treated bed nets are effective in increasing reported use. Increased community-level bed net coverage appears to provide additional protection against malaria transmission beyond individual use in a real-world context.
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Affiliation(s)
- Veronica Escamilla
- Carolina Population Center, University of North Carolina, 308 W Rosemary, CB 8120, Chapel Hill, NC, 27599, USA.
| | - Alisa Alker
- Division of Infectious Diseases, University of North Carolina, Chapel Hill, NC, 27599, USA
| | | | - Jonathan J Juliano
- Division of Infectious Diseases, University of North Carolina, Chapel Hill, NC, 27599, USA.,Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC, 27599, USA.,Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - William C Miller
- Division of Infectious Diseases, University of North Carolina, Chapel Hill, NC, 27599, USA.,Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC, 27599, USA
| | | | | | | | | | - Michael Emch
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC, 27599, USA.,Department of Geography, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Irving F Hoffman
- Division of Infectious Diseases, University of North Carolina, Chapel Hill, NC, 27599, USA.,UNC Project-Malawi, Lilongwe, Malawi
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Noukpo MH, Damien GB, Elanga-N'Dille E, Sagna AB, Drame PM, Chaffa E, Boussari O, Corbel V, Akogbéto M, Remoue F. Operational Assessment of Long-Lasting Insecticidal Nets by Using an Anopheles Salivary Biomarker of Human-Vector Contact. Am J Trop Med Hyg 2016; 95:1376-1382. [PMID: 27928087 DOI: 10.4269/ajtmh.15-0541] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 08/19/2016] [Indexed: 01/10/2023] Open
Abstract
The widespread implementation of long-lasting insecticidal nets (LLINs) is a major intervention method for malaria control. Although the LLINs coverage increases, information available on the physical integrity (PI) of implemented LLINs is incomplete. This study aimed to validate human IgG antibody (Ab) response to Anopheles gSG6-P1 salivary peptide antigen, previously demonstrated as a pertinent biomarker of human exposure to Anopheles bites, for evaluating the PI of LLINs in field conditions. We analyzed data from 262 randomly selected children (< 5 years of age) in health districts of Benin. Anti-gSG6-P1 IgG responses were assessed and compared with the PI of LLINs that these same children slept under, and evaluated by the hole index (HI). Specific IgG levels were positively correlated to LLINs HI (r = 0.342; P < 0.0001). According to antipeptide IgG level (i.e., intensity of vector exposure), two categories of LLINs PI were defined: 1) group "HI: [0, 100]" corresponding to LLINs with "good" PI and 2) "HI > 100" corresponding to LLINs with "bad" PI. These results suggest that human Ab response to salivary peptide could be a complementary tool to help defining a standardized threshold of efficacy for LLINs under field use.
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Affiliation(s)
- Mahoutin H Noukpo
- Centre de Recherche Entomologique de Cotonou (CREC), Cotonou, Bénin.,UMR IRD 224-CNRS 5290-Universités Montpellier Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), Cotonou, Bénin
| | - Georgia B Damien
- Centre de Recherche Entomologique de Cotonou (CREC), Cotonou, Bénin.,UMR IRD 224-CNRS 5290-Universités Montpellier Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), Cotonou, Bénin
| | - Emmanuel Elanga-N'Dille
- UMR IRD 224-CNRS 5290-Universités Montpellier Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), Cotonou, Bénin
| | - André B Sagna
- Institut Pierre Richet (IPR), Institut Nationale de la Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | - Papa M Drame
- UMR IRD 224-CNRS 5290-Universités Montpellier Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), Cotonou, Bénin
| | - Evelyne Chaffa
- Programme National de Lutte Contre le Paludisme (PNLP), Ministère de la Santé, Cotonou, Bénin
| | - Olayidé Boussari
- Centre de Recherche Entomologique de Cotonou (CREC), Cotonou, Bénin.,UMR IRD 224-CNRS 5290-Universités Montpellier Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), Cotonou, Bénin
| | - Vincent Corbel
- UMR IRD 224-CNRS 5290-Universités Montpellier Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), Cotonou, Bénin.,Department of Entomology, Faculty of Agriculture at Kamphaeng Saen, Kasetsart University, Nakhon Pathom, Thailand
| | - Martin Akogbéto
- Centre de Recherche Entomologique de Cotonou (CREC), Cotonou, Bénin.,Faculté des Sciences et Techniques (FAST), Université d'Abomey Calavi (UAC), Abomey, Bénin
| | - Franck Remoue
- Centre de Recherche Entomologique de Cotonou (CREC), Cotonou, Bénin. .,UMR IRD 224-CNRS 5290-Universités Montpellier Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), Cotonou, Bénin.,Institut Pierre Richet (IPR), Institut Nationale de la Santé Publique (INSP), Bouaké, Côte d'Ivoire
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26
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Mugwagwa N, Mberikunashe J, Gombe NT, Tshimanga M, Bangure D, Mungati M. Factors associated with malaria infection in Honde valley, Mutasa district, Zimbabwe, 2014: a case control study. BMC Res Notes 2015; 8:829. [PMID: 26715520 PMCID: PMC4693426 DOI: 10.1186/s13104-015-1831-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Accepted: 12/21/2015] [Indexed: 11/25/2022] Open
Abstract
Background In January of 2014, an outbreak of malaria was declared in the Honde Valley region of Mutasa District in Zimbabwe. The area has a hot, temperate climate and high rainfall pattern ideal for vector breeding and malaria transmission. Gravity fed irrigation channels span the valley creating a number of breeding sites for malaria vectors, mosquitoes. Malaria outbreaks have been a common occurrence in the district over the past few years despite the district meeting set targets for prevention interventions like indoor residual spraying (IRS) with pyrethroids and long lasting insecticidal nets distribution. The objectives of this study were to describe the outbreak by person, place and time, to assess the community’s knowledge on malaria transmission, signs and symptoms and treatment and to tease out factors associated with malaria infection in the district. Methods An unmatched case–control study was carried out. Interviewer guided questionnaires were administered to residents of the valley who met the inclusion criteria in order to tease out possible factors associated with malaria infection. A case was defined as a resident of Honde Valley with a history of malaria symptoms and a confirmed diagnosis from 13 January 2014 to 26 January 2014. A control was a resident of Mutasa District who was present in the district during the time of the outbreak but did not develop symptoms of malaria. A total of 87 cases and 87 controls were enrolled. Results Cases and controls were comparable in terms of socio-demographic characteristics and knowledge on malaria transmission, treatment and prevention. Risk factors associated with contracting malaria during the outbreak were being under the age of 5 years (OR = 9.92, CI 1, 2–80, 1), not using mosquito repellents (OR = 8, 25 CI 3, 78–18, 0), having outdoor activities before dawn and after dusk (OR = 2, 81 CI 1,04–7, 6). Having received indoor residual spraying in ones house was a risk factor for contracting malaria (OR = 1, 68 CI 0, 74–3, 83). This finding was not statistically significant. Sleeping under an insecticidal net and wearing protective clothing when outdoors after dusk were protective factors against contracting malaria (OR = 0, 27 CI 0, 12–0, 59 and OR = 0, 12 CI 0, 06–0, 25 respectively). All cases were treated according to the national malaria case management guidelines. Conclusions Risk factors for contracting malaria were being under the age of 5 years, outdoor activities at night and not using mosquito repellents. Net use was a protective factor from contracting malaria in Mutasa District. Indoor residual spraying with pyrethroids in Honde Valley was not a protective factor against contracting malaria.
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Affiliation(s)
- Norma Mugwagwa
- Department of Community Medicine, University of Zimbabwe, Office 3-66 Kaguvi Building, Corner 4th/Central Avenue, Harare, Zimbabwe
| | | | - Notion Tafara Gombe
- Department of Community Medicine, University of Zimbabwe, Office 3-66 Kaguvi Building, Corner 4th/Central Avenue, Harare, Zimbabwe
| | - Mufuta Tshimanga
- Department of Community Medicine, University of Zimbabwe, Office 3-66 Kaguvi Building, Corner 4th/Central Avenue, Harare, Zimbabwe
| | - Donewell Bangure
- Department of Community Medicine, University of Zimbabwe, Office 3-66 Kaguvi Building, Corner 4th/Central Avenue, Harare, Zimbabwe.
| | - More Mungati
- Department of Community Medicine, University of Zimbabwe, Office 3-66 Kaguvi Building, Corner 4th/Central Avenue, Harare, Zimbabwe
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Ranasinghe S, Ansumana R, Bockarie AS, Bangura U, Jimmy DH, Stenger DA, Jacobsen KH. Child bed net use before, during, and after a bed net distribution campaign in Bo, Sierra Leone. Malar J 2015; 14:462. [PMID: 26581840 PMCID: PMC4652461 DOI: 10.1186/s12936-015-0990-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Accepted: 11/05/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND This analysis examined how the proportion of children less than 5-years-old who slept under a bed net the previous night changed during and after a national long-lasting insecticidal net (LLIN) distribution campaign in Sierra Leone in November-December 2010. METHODS A citywide cross-sectional study in 2010-2011 interviewed the caregivers of more than 3000 under-five children from across urban Bo, Sierra Leone. Chi squared tests were used to assess change in use rates over time, and multivariate regression models were used to examine the factors associated with bed net use. RESULTS Reported rates of last-night bed net use changed from 38.7 % (504/1304) in the months before the LLIN campaign to 21.8 % (78/357) during the week of the campaign to 75.3 % (1045/1387) in the months after the national campaign. The bed net use rate significantly increased (p < 0.01) from before the campaign to after the universal LLIN distribution campaign in all demographic, socioeconomic, and health behaviour groups, even though reported use during the campaign dropped significantly. CONCLUSION Future malaria prevention efforts will need to promote consistent use of LLINs and address any remaining disparities in insecticide-treated bed net (ITN) use.
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Affiliation(s)
- Shamika Ranasinghe
- Department of Global and Community Health, George Mason University, 4400 University Drive 5B7, Fairfax, VA, 22030, USA.
| | - Rashid Ansumana
- Mercy Hospital Research Laboratory, Bo, Sierra Leone.
- Njala University, Bo, Sierra Leone.
| | | | - Umaru Bangura
- Mercy Hospital Research Laboratory, Bo, Sierra Leone.
| | | | | | - Kathryn H Jacobsen
- Department of Global and Community Health, George Mason University, 4400 University Drive 5B7, Fairfax, VA, 22030, USA.
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Wamae P, Githeko A, Otieno G, Kabiru E, Duombia S. Early biting of the Anopheles gambiae s.s. and its challenges to vector control using insecticide treated nets in western Kenya highlands. Acta Trop 2015. [PMID: 26209103 DOI: 10.1016/j.actatropica.2015.07.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Long term use of insecticides in malaria vector control has been shown to alter the behavior of vectors. Such behavioral shifts have the potential of undermining the effectiveness of insecticide-based control interventions. The effects of insecticide treated nets (ITNs) use on the composition, biting/feeding and sporozoite rates of Anopheles gambiae s.l. mosquitoes in Musilongo village, Vihiga County of western Kenya highlands were investigated. Adult mosquitoes were collected in selected sleeping spaces inside six randomly selected houses using miniature Centre for Disease Control and Prevention (CDC) light traps. Mosquito sampling in each house was conducted twice every week for 16 consecutive months (May 2010-August 2012). At each sampling a single trap was set in the selected space inside each house such that it collected mosquitoes alternatively from 18:00 to 21:00h and 21:00 to 06:00h every week. All collected mosquitoes were morphologically identified. Female Anopheles mosquitoes were classified according to their physiological status as unfed, fed, partially gravid and gravid, sorted and counted. Members of the A. gambiae complex were identified using a Polymerase chain reaction (PCR) method. Enzyme-linked-immunosorbent assay (ELISA) was used to determine blood meal sources and Plasmodium infection rates in A. gambiae s.l. mosquitoes. Blood meal tests were conducted on DNA extracted from gut contents of blood fed A. gambiae s.l. The head and thorax section of dried samples of A. gambiae s.l. were used in testing for the presence of Plasmodium falciparum (Pf) sporozoites. Overall, 735 adult female Anopheles comprising 708 [96.3%] A. gambiae s.l. and 27 [3.7%] Anopheles funestus mosquitoes were collected. A. gambiae s.l. population collected comprised, 615 [86.9%] unfed and 38 [5.4%] fed adult mosquitoes. The rest were either partially or fully gravid. The proportion of A. gambiae s.l. biting indoors within 18:00-21:00h was 15.8% (103/653) at a rate of 3.2bites per person per hour compared to 84.2% biting from 21:00-06:00h at a rate of 3.8 bites/per/h. An estimated 97.7% A. gambiae ss and 2.3% A. arabiensis constituted the indoor biting A. gambiae s.l. The population of An. gambiae s.l. biting from 18:00 to 21:00h had a Plasmodium faciparum (pf) sporozoite rate of 3.8% compared to 3.5% observed in populations biting within 21:00-06:00h. Human blood constituted 89% of An. gambiae s.l. blood meal sources. The risk of malaria transmission from 21:00 to 06:00h was approximately 5 fold the risk within 18:00-21:00h. Majority of the infective female A. gambiae s.l. adults were biting deep into the night than in the early hours of the night. Humans remain the preferred source of blood meal for A. gambiae s.s. the dominant malaria vector in the highlands. ITNs remain a fundamental control intervention against malaria transmission since female blood seekers were more during bed time than pre-bed time. Advocacy on enhanced net availability, integrity and usage in Kenyan highlands can reduce Pf transmission. Additional complementary interventions are required to control the biting and parasite transmission encountered before bed-time.
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29
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Randriamaherijaona S, Briët OJT, Boyer S, Bouraima A, N'Guessan R, Rogier C, Corbel V. Do holes in long-lasting insecticidal nets compromise their efficacy against pyrethroid resistant Anopheles gambiae and Culex quinquefasciatus? Results from a release-recapture study in experimental huts. Malar J 2015; 14:332. [PMID: 26310788 PMCID: PMC4551388 DOI: 10.1186/s12936-015-0836-7] [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: 06/09/2015] [Accepted: 08/04/2015] [Indexed: 11/16/2022] Open
Abstract
Background Resistance of malaria vectors to pyrethroids threatens the effectiveness of long-lasting insecticidal nets (LLINs) as a tool for malaria control. Recent experimental hut and observational studies in Benin show that pyrethroid resistance reduces the insecticidal effect and personal protection of LLINs especially when they become torn. The World Health Organization has proposed a threshold for when nets are “too torn” at 1,000 cm2 for rectangular holes and 790 cm2 for round holes. This study examines whether there is a threshold above which LLINs no longer reduce malaria transmission. Methods Intact and artificially-holed LLINs under three months old and untreated nets were tested by releasing mosquitoes from a susceptible Anopheles gambiae colony, a pyrethroid-resistant An. gambiae population and a resistant Culex quinquefasciatus population in closed experimental huts in Southern Benin, West Africa. The efficacy of LLINs and untreated nets was evaluated in terms of protection against blood feeding, insecticidal effect and potential effect on malaria transmission. Results Personal protection by both LLINs and untreated nets decreased exponentially with increasing holed surface area, without evidence for a specific threshold beyond which LLINs could be considered as ineffective. The insecticidal effect of LLINs was lower in resistant mosquitoes than in susceptible mosquitoes, but holed surface area had little or no impact on the insecticidal effect of LLINs. LLINs with 22,500 cm2 holed surface area and target insecticide content provided a personal protection of 0.60 (95 % CI 0.44–0.73) and a low insecticidal effect of 0.20 (95 % CI 0.12–0.30) against resistant An. gambiae. Nevertheless, mathematical models suggested that if 80 % of the population uses such nets, they could still prevent 94 % (95 % CI 89–97 %) of transmission by pyrethroid-resistant An. gambiae. Conclusions Even though personal protection by LLINs against feeding mosquitoes is strongly reduced by holes, the insecticidal effect of LLINs is independent of the holed surface area, but strongly dependent on insecticide resistance. Badly torn nets that still contain insecticide have potential to reduce malaria transmission. The relationship between LLIN integrity and efficacy needs to be understood in order to guide LLIN distribution policy. Electronic supplementary material The online version of this article (doi:10.1186/s12936-015-0836-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | - Olivier J T Briët
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland. .,University of Basel, Basel, Switzerland.
| | | | - Aziz Bouraima
- Centre de Recherches Entomologiques de Cotonou (CREC), 06 BP 2604, Cotonou, Republic of Benin.
| | - Raphael N'Guessan
- Centre de Recherches Entomologiques de Cotonou (CREC), 06 BP 2604, Cotonou, Republic of Benin. raphael.n'.,Department of Disease Control, London School of Hygiene and Tropical Medicine, Keppel street, London, WC1E 7HT, UK. raphael.n'
| | - Christophe Rogier
- Institut Pasteur de Madagascar, Antananarivo, Madagascar. .,Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes, UM 63, CNRS 7278, IRD 198, INSERM 1095, Aix Marseille Université, Marseille, France. .,Institut de Recherche Biomédicale des Armées, Brétigny sur Orge, France.
| | - Vincent Corbel
- Institut de Recherche pour le Développement, Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle (IRD 224-CNRS 5290 UM1-UM2), Montpellier, France. .,Department of Entomology, Faculty of Agriculture at Kamphaeng Saen, Kamphaeng Saen Campus, Kasetsart University, Nakhon Pathom, 73140, Thailand.
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Vanden Eng JL, Chan A, Abílio AP, Wolkon A, Ponce de Leon G, Gimnig J, Morgan J. Bed Net Durability Assessments: Exploring a Composite Measure of Net Damage. PLoS One 2015; 10:e0128499. [PMID: 26047494 PMCID: PMC4457879 DOI: 10.1371/journal.pone.0128499] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Accepted: 04/27/2015] [Indexed: 11/18/2022] Open
Abstract
Background The durability of Long Lasting Insecticidal Nets (LLINs) in field conditions is of great importance for malaria prevention and control efforts; however, the physical integrity of the net fabric is not well understood making it challenging to determine overall effectiveness of nets as they age. The 2011 World Health Organization Pesticide Evaluation Scheme (WHOPES) guidelines provide a simple, standardized method using a proportional hole index (PHI) for assessing net damage with the intent to provide national malaria control programs with guidelines to assess the useful life of LLINS and estimate the rate of replacement. Methods We evaluated the utility of the PHI measure using 409 LLINs collected over three years in Nampula Province, Mozambique following a mass distribution campaign in 2008. For each LLIN the diameter and distance from the bottom of the net were recorded for every hole. Holes were classified into four size categories and a PHI was calculated following WHOPES guidelines. We investigate how the size, shape, and location of holes influence the PHI. The areas of the WHOPES defined categories were compared to circular and elliptical areas based on approximate shape and actual measured axes of each hole and the PHI was compared to cumulative damaged surface area of the LLIN. Results The damaged area of small, medium, large, and extra-large holes was overestimated using the WHOPES categories compared to elliptical areas using the actual measured axes. Similar results were found when comparing to circular areas except for extra-large holes which were underestimated. (Wilcoxon signed rank test of differences p< 0.0001 for all sizes). Approximating holes as circular overestimated hole surface area by 1.5 to 2 times or more. There was a significant difference in the mean number of holes < 0.5 cm by brand and there were more holes of all sizes on the bottom of nets than the top. For a range of hypothetical PHI thresholds used to designate a “failed LLIN”, roughly 75 to 80% of failed LLINs were detected by considering large and extra-large holes alone, but sensitivity varied by brand. Conclusions Future studies may refine the PHI to better approximate overall damaged surface area. Furthermore, research is needed to identify whether or not appropriate PHI thresholds can be used to deem a net no longer protective. Once a cutoff is selected, simpler methods of determining the effective lifespan of LLINs can help guide replacement strategies for malaria control programs.
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Affiliation(s)
- Jodi L. Vanden Eng
- Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, GA, United States of America
- * E-mail:
| | - Adeline Chan
- Entomology Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, GA, United States of America
| | - Ana Paula Abílio
- Instituto Nacional da Saúde, Ministério da Saúde, Maputo, Mozambique
| | - Adam Wolkon
- Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, GA, United States of America
| | - Gabriel Ponce de Leon
- Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, GA, United States of America
- United States President’s Malaria Initiative, Centers for Disease Control and Prevention, Atlanta, GA, United States of America
| | - John Gimnig
- Entomology Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, GA, United States of America
| | - Juliette Morgan
- Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, GA, United States of America
- United States President’s Malaria Initiative, Centers for Disease Control and Prevention, Atlanta, GA, United States of America
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Kayedi MH, Khamisabadi K, Dehghani N, Haghdoost AA. Entomological evaluation of PermaNet 2.0® and K-O Tab 1-2-3® treated nets in comparison to nets conventionally treated with deltamethrin, after repeated washing. Pathog Glob Health 2015; 109:196-201. [PMID: 25978624 DOI: 10.1179/2047773215y.0000000010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
The residual insecticidal power of two types of ITNs (PermaNet 2.0® (PN2) and K-O Tab 1-2-3® (KO 123)), compared to K-O Tab® (KO) treated nets, was assessed. The nets were tested unwashed, and after being washed, by hand 5, 15 and 21 times, respectively. After each wash, the nets were dried vertically on a line, in the shade. Two types of bioassays (mean median knock down times (MMKDT) and mortality 24 hours after a 3-minute exposure (%mortality)) were used, along with reared female Anopheles stephensi. The number of washes had a great impact on MMKDT and %mortality of all types of nets. This impact was greater for conventionally treated nets, indicating that PN2 and KO 123 nets are significantly more wash resistant than KO nets after 21 washes. There was no significant difference between PN2 and KO 123 with respect to %mortality 24 hours after a 3-minute exposure at 0, 15 and 21 washes. Similarly, the same results were obtained for MMKDT, and the differences between PN2 and KO 123 were not statistically significant. This study demonstrates that the efficacy of KO 123 nets is as beneficial as the efficacy of PN2 nets up to 21 washes.
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Morgan J, Abílio AP, do Rosario Pondja M, Marrenjo D, Luciano J, Fernandes G, Sabindy S, Wolkon A, Ponce de Leon G, Chan A, Vanden Eng J. Physical durability of two types of long-lasting insecticidal nets (LLINs) three years after a mass LLIN distribution campaign in Mozambique, 2008-2011. Am J Trop Med Hyg 2015; 92:286-93. [PMID: 25404079 PMCID: PMC4347331 DOI: 10.4269/ajtmh.14-0023] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Accepted: 09/12/2014] [Indexed: 11/07/2022] Open
Abstract
We conducted a prospective evaluation to measure the physical durability of two brands of long-lasting insecticidal nets (LLINs) distributed during a campaign in 2008 in Nampula Province, Mozambique. Households with LLINs tagged during the campaign (6,000) were geo-located (34%) and a random sample was selected for each of 3 years of follow-up. The LLINs were evaluated in the field and a laboratory for presence of holes and a proportional hole index (pHI) was calculated following the World Health Organization guidelines. We performed 567 interviews (79.0%) and found 75.3% (72.1-78.4%) of households retained at least one LLIN after 3 years; the most common cause of attrition was damage beyond repair (51.0%). Hole damage was evident after 1 year, and increased by year. Olyset had a significantly greater mean number of holes and pHI compared with PermaNet 2.0 brand (all P values ≤ 0.001). Additional information about LLIN durability is recommended to improve malaria control efforts.
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Affiliation(s)
- Juliette Morgan
- President's Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia; Instituto Nacional da Saúde, Ministério da Saúde, Maputo, Mozambique; Programa Nacional de Controlo da Malária, Ministério da Saúde, Maputo, Mozambique; President's Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia; President's Malaria Initiative, Entomology Branch, Centers for Disease Control and Prevention, Atlanta, Georgia
| | - Ana Paula Abílio
- President's Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia; Instituto Nacional da Saúde, Ministério da Saúde, Maputo, Mozambique; Programa Nacional de Controlo da Malária, Ministério da Saúde, Maputo, Mozambique; President's Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia; President's Malaria Initiative, Entomology Branch, Centers for Disease Control and Prevention, Atlanta, Georgia
| | - Maria do Rosario Pondja
- President's Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia; Instituto Nacional da Saúde, Ministério da Saúde, Maputo, Mozambique; Programa Nacional de Controlo da Malária, Ministério da Saúde, Maputo, Mozambique; President's Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia; President's Malaria Initiative, Entomology Branch, Centers for Disease Control and Prevention, Atlanta, Georgia
| | - Dulcisária Marrenjo
- President's Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia; Instituto Nacional da Saúde, Ministério da Saúde, Maputo, Mozambique; Programa Nacional de Controlo da Malária, Ministério da Saúde, Maputo, Mozambique; President's Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia; President's Malaria Initiative, Entomology Branch, Centers for Disease Control and Prevention, Atlanta, Georgia
| | - Jacinta Luciano
- President's Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia; Instituto Nacional da Saúde, Ministério da Saúde, Maputo, Mozambique; Programa Nacional de Controlo da Malária, Ministério da Saúde, Maputo, Mozambique; President's Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia; President's Malaria Initiative, Entomology Branch, Centers for Disease Control and Prevention, Atlanta, Georgia
| | - Guilhermina Fernandes
- President's Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia; Instituto Nacional da Saúde, Ministério da Saúde, Maputo, Mozambique; Programa Nacional de Controlo da Malária, Ministério da Saúde, Maputo, Mozambique; President's Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia; President's Malaria Initiative, Entomology Branch, Centers for Disease Control and Prevention, Atlanta, Georgia
| | - Samira Sabindy
- President's Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia; Instituto Nacional da Saúde, Ministério da Saúde, Maputo, Mozambique; Programa Nacional de Controlo da Malária, Ministério da Saúde, Maputo, Mozambique; President's Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia; President's Malaria Initiative, Entomology Branch, Centers for Disease Control and Prevention, Atlanta, Georgia
| | - Adam Wolkon
- President's Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia; Instituto Nacional da Saúde, Ministério da Saúde, Maputo, Mozambique; Programa Nacional de Controlo da Malária, Ministério da Saúde, Maputo, Mozambique; President's Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia; President's Malaria Initiative, Entomology Branch, Centers for Disease Control and Prevention, Atlanta, Georgia
| | - Gabriel Ponce de Leon
- President's Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia; Instituto Nacional da Saúde, Ministério da Saúde, Maputo, Mozambique; Programa Nacional de Controlo da Malária, Ministério da Saúde, Maputo, Mozambique; President's Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia; President's Malaria Initiative, Entomology Branch, Centers for Disease Control and Prevention, Atlanta, Georgia
| | - Adeline Chan
- President's Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia; Instituto Nacional da Saúde, Ministério da Saúde, Maputo, Mozambique; Programa Nacional de Controlo da Malária, Ministério da Saúde, Maputo, Mozambique; President's Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia; President's Malaria Initiative, Entomology Branch, Centers for Disease Control and Prevention, Atlanta, Georgia
| | - Jodi Vanden Eng
- President's Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia; Instituto Nacional da Saúde, Ministério da Saúde, Maputo, Mozambique; Programa Nacional de Controlo da Malária, Ministério da Saúde, Maputo, Mozambique; President's Malaria Initiative, Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia; President's Malaria Initiative, Entomology Branch, Centers for Disease Control and Prevention, Atlanta, Georgia
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Irish SR. The behaviour of mosquitoes in relation to humans under holed bednets: the evidence from experimental huts. Mem Inst Oswaldo Cruz 2014; 109:905-11. [PMID: 25410994 PMCID: PMC4296495 DOI: 10.1590/0074-0276140159] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Accepted: 08/15/2014] [Indexed: 11/22/2022] Open
Abstract
The physical integrity of bednets is a concern of national malaria control programs,
as it is a key factor in determining the rate of replacement of bednets. It is
largely assumed that increased numbers of holes will result in a loss of protection
of sleepers from potentially infective bites. Experimental hut studies are valuable
in understanding mosquito behaviour indoors, particularly as it relates to blood
feeding and mortality. This review summarises findings from experimental hut studies,
focusing on two issues: (i) the effect of different numbers or sizes of holes in
bednets and (ii) feeding behaviour and mortality with holed nets as compared with
unholed nets. As might be expected, increasing numbers and area of holes resulted in
increased blood feeding by mosquitoes on sleepers. However, the presence of holes did
not generally have a large effect on the mortality of mosquitoes. Successfully
entering a holed mosquito net does not necessarily mean that mosquitoes spend less
time in contact with the net, which could explain the lack in differences in
mortality. Further behavioural studies are necessary to understand mosquito behaviour
around nets and the importance of holed nets on malaria transmission.
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Affiliation(s)
- Seth R Irish
- Entomology Branch, Department of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Center for Global Health, Atlanta, GA, USA
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Kabula B, Tungu P, Malima R, Rowland M, Minja J, Wililo R, Ramsan M, McElroy PD, Kafuko J, Kulkarni M, Protopopoff N, Magesa S, Mosha F, Kisinza W. Distribution and spread of pyrethroid and DDT resistance among the Anopheles gambiae complex in Tanzania. MEDICAL AND VETERINARY ENTOMOLOGY 2014; 28:244-52. [PMID: 24192019 PMCID: PMC10884793 DOI: 10.1111/mve.12036] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 09/10/2013] [Accepted: 09/19/2013] [Indexed: 06/02/2023]
Abstract
The development of insecticide resistance is a threat to the control of malaria in Africa. We report the findings of a national survey carried out in Tanzania in 2011 to monitor the susceptibility of malaria vectors to pyrethroid, organophosphate, carbamate and DDT insecticides, and compare these findings with those identified in 2004 and 2010. Standard World Health Organization (WHO) methods were used to detect knock-down and mortality rates in wild female Anopheles gambiae s.l. (Diptera: Culicidae) collected from 14 sentinel districts. Diagnostic doses of the pyrethroids deltamethrin, lambdacyhalothrin and permethrin, the carbamate propoxur, the organophosphate fenitrothion and the organochlorine DDT were used. Anopheles gambiae s.l. was resistant to permethrin in Muleba, where a mortality rate of 11% [95% confidence interval (CI) 6-19%] was recorded, Muheza (mortality rate of 75%, 95% CI 66-83%), Moshi and Arumeru (mortality rates of 74% in both). Similarly, resistance was reported to lambdacyhalothrin in Muleba, Muheza, Moshi and Arumeru (mortality rates of 31-82%), and to deltamethrin in Muleba, Moshi and Muheza (mortality rates of 28-75%). Resistance to DDT was reported in Muleba. No resistance to the carbamate propoxur or the organophosphate fenitrothion was observed. Anopheles gambiae s.l. is becoming resistant to pyrethoids and DDT in several parts of Tanzania. This has coincided with the scaling up of vector control measures. Resistance may impair the effectiveness of these interventions and therefore demands close monitoring and the adoption of a resistance management strategy.
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Affiliation(s)
- B Kabula
- Amani Research Centre, National Institute for Medical Research, Ubwari, Muheza, Tanzania; Department of Parasitology and Entomology, Kilimanjaro Christian Medical University College, Tumaini University, Moshi, Tanzania
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Quantifying the impact of decay in bed-net efficacy on malaria transmission. J Theor Biol 2014; 363:247-61. [PMID: 25158163 PMCID: PMC4374367 DOI: 10.1016/j.jtbi.2014.08.018] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Revised: 07/30/2014] [Accepted: 08/11/2014] [Indexed: 11/22/2022]
Abstract
Insecticide-treated nets (ITNs) are at the forefront of malaria control programs and even though the percentage of households in sub-Saharan Africa that owned nets increased from 3% in 2000 to 53% in 2012, many children continue to die from malaria. The potential impact of ITNs on reducing malaria transmission is limited due to inconsistent or improper use, as well as physical decay in effectiveness. Most mathematical models for malaria transmission have assumed a fixed effectiveness rate for bed-nets, which can overestimate the impact of nets on malaria control. We develop a model for malaria spread that captures the decrease in ITN effectiveness due to physical and chemical decay, as well as human behavior as a function of time. We perform uncertainty and sensitivity analyses to identify and rank parameters that play a critical role in malaria transmission. These analyses show that the basic reproduction number R0, and the infectious human population are most sensitive to bed-net coverage and the biting rate of mosquitoes. Our results show the existence of a backward bifurcation for the case in which ITN efficacy is constant over time, which occurs for some range of parameters and is characterized by high malaria mortality in humans. This result implies that bringing R0 to less than one is not enough for malaria elimination but rather additional efforts will be necessary to control the disease. For the case in which ITN efficacy decays over time, we determine coverage levels required to control malaria for different ITN efficacies and demonstrate that ITNs with longer useful lifespans perform better in malaria control. We conclude that malaria control programs should focus on increasing bed-net coverage, which can be achieved by enhancing malaria education and increasing bed-net distribution in malaria endemic regions.
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Culminating anti-malaria efforts at long lasting insecticidal net? J Infect Public Health 2014; 7:457-64. [PMID: 25092624 DOI: 10.1016/j.jiph.2014.06.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Revised: 05/08/2014] [Accepted: 06/13/2014] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND Long-lasting insecticidal nets (LLINs) are a primary method in malaria control efforts. However, a decline in the biological efficacy and physical integrity over a period of comparatively lesser time than claimed, waning of naturally acquired immunity among regular users and misuse of LLINs are serious concerns. SEARCH AND SELECTION OF LITERATURE The literature for the current review was searched in PubMed, SCOPUS Database and Google using combined search strings of related key-words. Literature with sufficient data and information on the current subject was selected to reach a valid conclusion. FINDINGS The World Health Organization (WHO) has emphasized that LLINs should be considered a public good for people inhabiting malaria endemic settings. LLINs exhibited a cumulative effect on the vector density and may force anthropophilic mosquito vectors to find alternative animal hosts for blood meal. However, the physical integrity and biological activity of LLINs declines faster than the anticipated time due to different operational conditions and the spread of insecticide resistance. LLINs have been successful in reducing malaria incidences by either reducing or not allowing human exposure to the vector mosquitoes, but at the same time, LLINs debilitate the natural protective immunity against malaria parasite. Misuse of LLINs for deviant purposes is common and is a serious environmental concern, as people believe that traditional methods of prevention against malaria that have enabled them to survive through a long time are effective and sufficient. Moreover, people are often ill-informed regarding the toxic effects of LLINs. CONCLUSIONS Specific criteria for determining the serviceable life and guidelines on the safe washing and disposal of LLINs need to be developed, kept well-informed and closely monitored. Malaria case management, environment management and community awareness to reduce the misuse of LLINs are crucial. Focused research on developing effective anti-malarial drugs, vaccines and new insecticides to reduce resistance is imperative to tackle malaria in the future.
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Tabue RN, Nem T, Atangana J, Bigoga JD, Patchoke S, Tchouine F, Fodjo BY, Leke RGF, Fondjo E. Anopheles ziemanni a locally important malaria vector in Ndop health district, north west region of Cameroon. Parasit Vectors 2014; 7:262. [PMID: 24903710 PMCID: PMC4055171 DOI: 10.1186/1756-3305-7-262] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2014] [Accepted: 05/24/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Malaria transmission in Cameroon is mediated by a plethora of vectors that are heterogeneously distributed across the country depending on the biotope. To effectively guide malaria control operations, regular update on the role of local Anopheles species is essential. Therefore, an entomological survey was conducted between August 2010 and May 2011 to evaluate the role of the local anopheline population in malaria transmission in three villages of the Ndop health district in the northwest region of Cameroon where malaria is holoendemic, as a means to acquiring evidence based data for improved vector intervention. METHODS Mosquitoes were sampled both indoor and outdoor for four consecutive nights in each locality during each month of survey. Sampling was done by the human landing catch method on volunteers. Anopheles species were identified morphologically and their ovaries randomly dissected for parity determination. Infection with Plasmodium falciparum was detected by Circumsporozoite protein ELISA. Members of An. gambiae complex were further identified to molecular level by PCR and RFLP PCR. RESULTS An. ziemanni was the main malaria vector and whether outdoor or indoor. The man biting rate for the vectors ranged from 6.75 to 8.29 bites per person per night (b/p/n). The entomological inoculation rate for this vector species was 0.0278 infectious bites per person per night (ib/p/n) in Mbapishi, 0.034 ib/p/n in Mbafuh, and 0.063 ib/p/n in Backyit. These were by far greater than that for An. gambiae. No difference was observed in the parity rate of these two vectors. PCR analysis revealed the presence of only An. colluzzi (M- form). CONCLUSIONS An. ziemanni is an important local malaria vector in Ndop health district. The findings provide useful baseline information on the anopheles species composition, their distribution and role in malaria transmission that would guide the implementation of integrated vector management strategies in the locality.
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Affiliation(s)
- Raymond N Tabue
- National Reference Unit for Vector Control, The Biotechnology Center, University of Yaoundé I, P,O, Box 3851-Messa, Yaoundé, Cameroon.
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Manyanga VP, Minzi O, Ngasala B. Prevalence of malaria and anaemia among HIV infected pregnant women receiving co-trimoxazole prophylaxis in Tanzania: a cross sectional study in Kinondoni Municipality. BMC Pharmacol Toxicol 2014; 15:24. [PMID: 24761799 PMCID: PMC4014408 DOI: 10.1186/2050-6511-15-24] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2013] [Accepted: 04/03/2014] [Indexed: 12/15/2022] Open
Abstract
Background HIV-infected pregnant women are particularly more susceptible to the deleterious effects of malaria infection particularly anaemia. In order to prevent opportunistic infections and malaria, a policy of daily co-trimoxazole prophylaxis without the standard Suphadoxine-Pyrimethamine intermittent preventive treatment (SP-IPT) was introduced to all HIV infected pregnant women in the year 2011. However, there is limited information about the effectiveness of this policy. Methods This was a cross sectional study conducted among HIV-infected pregnant women receiving co-trimoxazole prophylaxis in eight public health facilities in Kinondoni Municipality from February to April 2013. Blood was tested for malaria infection and anaemia (haemoglobin <11 g/dl). Data were collected on the adherence to co-trimoxazole prophylaxis and other risk factors for malaria infection and anaemia. Pearson chi-square test, Fischer’s exact test and multivariate logistic regression were used in the statistical analysis. Results This study enrolled 420 HIV infected pregnant women. The prevalence of malaria infection was 4.5%, while that of anaemia was 54%. The proportion of subjects with poor adherence to co-trimoxazole was 50.5%. As compared to HIV infected pregnant women with good adherence to co-trimoxazole prophylaxis, the poor adherents were more likely to have a malaria infection (Adjusted Odds Ratio, AOR = 6.81, 95% CI = 1.35-34.43, P = 0.02) or anaemia (AOR = 1.75, 95% CI = 1.03-2.98, P = 0.039). Other risk factors associated with anaemia were advanced WHO clinical stages, current malaria infection and history of episodes of malaria illness during the index pregnancy. Conclusion The prevalence of malaria was low; however, a significant proportion of subjects had anaemia. Good adherence to co-trimoxazole prophylaxis was associated with reduction of both malaria infection and anaemia among HIV infected pregnant women.
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Affiliation(s)
| | - Omary Minzi
- Unit of Pharmacology and Therapeutics, Muhimbili University of Health and Allied Sciences, Dar Es Salaam, Tanzania.
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Anshebo GY, Graves PM, Smith SC, Wills AB, Damte M, Endeshaw T, Shargie EB, Gebre T, Mosher AW, Patterson AE, Emerson PM. Estimation of insecticide persistence, biological activity and mosquito resistance to PermaNet® 2 long-lasting insecticidal nets over three to 32 months of use in Ethiopia. Malar J 2014; 13:80. [PMID: 24602340 PMCID: PMC3995957 DOI: 10.1186/1475-2875-13-80] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Accepted: 02/15/2014] [Indexed: 11/17/2022] Open
Abstract
Background Information is needed on the expected durability of insecticidal nets under operational conditions. The persistence of insecticidal efficacy is important to estimate the median serviceable life of nets under field conditions and to plan for net replacement. Methods Deltamethrin residue levels were evaluated by the proxy method of X-ray fluorescence spectrometry on 189 nets used for three to six months from nine sites, 220 nets used for 14-20 months from 11 sites, and 200 nets used for 26-32 months from ten sites in Ethiopia. A random sample of 16.5-20% of nets from each time period (total 112 of 609 nets) were tested by bioassay with susceptible mosquitoes, and nets used for 14-20 months and 26-32 months were also tested with wild caught mosquitoes. Results Mean insecticide levels estimated by X-ray fluorescence declined by 25.9% from baseline of 66.2 (SD 14.6) mg/m2 at three to six months to 44.1 (SD 21.2) mg/m2 at 14-20 months and by 30.8% to 41.1 (SD 18.9) mg/m2 at 26-32 months. More than 95% of nets retained greater than 10 mg/m2 of deltamethrin and over 79% had at least 25 mg/m2 at all time periods. By bioassay with susceptible Anopheles, mortality averaged 89.0% on 28 nets tested at three to six months, 93.3% on 44 nets at 14-20 months and 94.1% on 40 nets at 26-32 months. With wild caught mosquitoes, mortality averaged 85.4% (range 79.1 to 91.7%) at 14-20 months but had dropped significantly to 47.2% (39.8 to 54.7%) at 26-32 months. Conclusions Insecticide residue level, as estimated by X-ray fluorescence, declined by about one third between three and six months and 14-20 months, but remained relatively stable and above minimum requirements thereafter up to 26-32 months. The insecticidal activity of PermaNet® 2.0 long-lasting insecticidal nets in the specified study area may be considered effective to susceptible mosquitoes at least for the duration indicated in this study (32 months). However, results indicated that resistance in the wild population is already rendering nets with optimum insecticide concentrations less effective in practice.
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Affiliation(s)
| | - Patricia M Graves
- Present address: School of Public Health, Tropical Medicine and Rehabilitation Sciences, James Cook University, PO Box 6811, Cairns, Qld, Australia.
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Sovi A, Azondékon R, Aïkpon RY, Govoétchan R, Tokponnon F, Agossa F, Salako AS, Oké-Agbo F, Aholoukpè B, Okè M, Gbénou D, Massougbodji A, Akogbéto M. Impact of operational effectiveness of long-lasting insecticidal nets (LLINs) on malaria transmission in pyrethroid-resistant areas. Parasit Vectors 2013; 6:319. [PMID: 24499508 PMCID: PMC4029312 DOI: 10.1186/1756-3305-6-319] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Accepted: 10/31/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND A dynamic study on the transmission of malaria was conducted in two areas (R⁺ area: Low resistance area; R⁺⁺⁺ area: High resistance area) in the department of Plateau in South Eastern Benin, where the population is protected by Long Lasting Insecticidal Nets (LLINs). The aim of this study was to determine if the resistance of malaria vectors to insecticides has an impact on their behavior and on the effectiveness of LLINs in the reduction of malaria transmission. METHODS Populations of Anopheles gambiae s.l. were sampled monthly by human landing catch in the two areas to evaluate human biting rates (HBR). Collected mosquitoes were identified morphologically and female Anopheles mosquitoes were tested for the presence of Plasmodium falciparum antigen as assessed using ELISA. The entomological inoculation rate (EIR) was also calculated (EIR = HBR x sporozoitic index [S]). We estimated the parity rate by dissecting the females of An. gambiae. Finally, window catch and spray catch were conducted in order to assess the blood feeding rate and the exophily rate of vectors. RESULTS After 6 months of tracking the mosquito's behavior in contact with the LLINs (Olyset) in R⁺⁺⁺ and R⁺ areas, the entomological indicators of the transmission of malaria (parity rate and sporozoitic index) were similar in the two areas. Also, An. gambiae populations showed the same susceptibility to P. falciparum in both R⁺ and R⁺⁺⁺ areas. The EIR and the exophily rate are higher in R⁺ area than in R⁺⁺⁺ area. But the blood-feeding rate is lower in R⁺ area comparing to R⁺⁺⁺. CONCLUSION The highest entomological inoculation rate observed in R⁺ area is mostly due to the strong aggressive density of An. gambiae recorded in one of the study localities. On the other hand, the highest exophily rate and the low blood-feeding rate recorded in R⁺ area compared to R⁺⁺⁺ area are not due to the resistance status of An. gambiae, but due to the differences in distribution and availability of breeding sites for Anopheles mosquitoes between areas. However, this phenomenon is not related to the resistance status, but is related to the environment instead.
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Affiliation(s)
- Arthur Sovi
- Centre de Recherche Entomologique de Cotonou, Cotonou 06 BP 2604, Benin
- Faculté des Sciences et Techniques, Université d’Abomey Calavi, Calavi, Bénin
| | | | - Rock Y Aïkpon
- Centre de Recherche Entomologique de Cotonou, Cotonou 06 BP 2604, Benin
- Faculté des Sciences et Techniques, Université d’Abomey Calavi, Calavi, Bénin
| | - Renaud Govoétchan
- Centre de Recherche Entomologique de Cotonou, Cotonou 06 BP 2604, Benin
- Faculté des Sciences et Techniques, Université d’Abomey Calavi, Calavi, Bénin
| | - Filémon Tokponnon
- Faculté des Sciences et Techniques, Université d’Abomey Calavi, Calavi, Bénin
- Programme Nationale de Lutte contre le Paludisme, Cotonou, Benin
| | - Fiacre Agossa
- Centre de Recherche Entomologique de Cotonou, Cotonou 06 BP 2604, Benin
| | - Albert S Salako
- Centre de Recherche Entomologique de Cotonou, Cotonou 06 BP 2604, Benin
| | - Frédéric Oké-Agbo
- Centre de Recherche Entomologique de Cotonou, Cotonou 06 BP 2604, Benin
| | - Bruno Aholoukpè
- Programme Nationale de Lutte contre le Paludisme, Cotonou, Benin
| | - Mariam Okè
- Programme Nationale de Lutte contre le Paludisme, Cotonou, Benin
| | - Dina Gbénou
- Faculté des Sciences de la Santé de l’Université d’Abomey- Calavi, Cotonou, Benin
| | - Achille Massougbodji
- Faculté des Sciences de la Santé de l’Université d’Abomey- Calavi, Cotonou, Benin
| | - Martin Akogbéto
- Centre de Recherche Entomologique de Cotonou, Cotonou 06 BP 2604, Benin
- Faculté des Sciences et Techniques, Université d’Abomey Calavi, Calavi, Bénin
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Mosqueira B, Chabi J, Chandre F, Akogbeto M, Hougard JM, Carnevale P, Mas-Coma S. Proposed use of spatial mortality assessments as part of the pesticide evaluation scheme for vector control. Malar J 2013; 12:366. [PMID: 24139513 PMCID: PMC3852965 DOI: 10.1186/1475-2875-12-366] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Accepted: 09/22/2013] [Indexed: 11/10/2022] Open
Abstract
Background The WHO Pesticide Evaluation Scheme to evaluate the efficacy of insecticides does not include the testing of a lethal effect at a distance. A tool was developed to evaluate the spatial mortality of an insecticide product against adult mosquitoes at a distance under laboratory and field conditions. Operational implications are discussed. Methods Insecticide paint, Inesfly 5A IGR™, containing two organophosphates (OPs): chlorpyrifos and diazinon, and one insect growth regulator (IGR): pyriproxyfen, was the product tested. Laboratory tests were performed using “distance boxes” with surfaces treated with one layer of control or insecticide paint at a dose of 1 kg/6 sq m. Field tests were conducted up to 12 months in six experimental huts randomly allocated to control or one or two layers of insecticide paint at 1 kg/6 sq m. All distance tests were performed using reference-susceptible strains of Anopheles gambiae and Culex quinquefasciatus left overnight at a distance of 1 m from control or treated surfaces. Results After an overnight exposition at distances of 1 m, field and laboratory evaluations at 0 months after treatment (T0) yielded 100% mortality rates on surfaces treated with one layer at 1 kg/6 sq m against susceptible strains of An. gambiae and Cx. quinquefasciatus. Testing for long-term efficacy in the field gave mortality rates of 96-100% after an overnight exposition at a distance of 1 m for up to 12 months in huts where a larger volume was treated (walls and ceilings) with one or two layers of insecticide paint. Conclusion A comprehensive evaluation of the full profile of insecticide products, both upon contact and spatially, may help rationalize vector control efforts more efficiently. Treating a large enough volume may extend a product’s mortality efficacy in the long-term, which contact tests would fail to assess. It is hereby proposed to explore the development of cost effective methods to assess spatial mortality and to include them as one additional measurement of insecticide efficacy against mosquitoes and other arthropod vectors in WHOPES Phase I and Phase II studies.
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Affiliation(s)
- Beatriz Mosqueira
- Departamento de Parasitologia, Facultad de Farmacia, Universidad de Valencia, Av Vicent Andrés Estellés s/n, Burjassot 46100, Valencia, Spain.
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Kayedi MH, Lines JD, Haghdoost AA, Najafi S. A randomized and controlled comparison of the wash-resistances and insecticidal efficacies of four types of deltamethrin-treated nets, over a 6-month period of domestic use with washing every 2 weeks, in a rural area of Iran. ANNALS OF TROPICAL MEDICINE AND PARASITOLOGY 2013; 101:519-28. [PMID: 17716435 DOI: 10.1179/136485907x193815] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In a randomized, prospective, 6-month-long field study in a rural area of Iran, the wash resistances of 200 nets (40 PermaNet, 40 Yorkool and 40 A-Z nets), that their manufacturers claimed be long-lasting insecticidal nets (LLIN), were compared with those of 40 nets conventionally treated with deltamethrin (using K-O Tab tablets). All the nets were kept in routine domestic use and subjected to standardized hand-washing at 2-week intervals. Wild-caught or laboratory-reared Anopheles stephensi were used for the bio-assays of insecticidal activity. The regular washing and domestic use led to reductions in the insecticidal activities of all the treated nets after 6 months. Although the PermaNet nets showed the smallest reduction, they were not significantly better than the conventionally treated nets, which still showed acceptable insecticidal activity after 6 months. The PermaNet and A-Z nets both performed significantly better than the Yorkool nets, which were slightly but not significantly worse than the conventionally treated nets. In questionnaire-based interviews, the local householders were found to wash their own (non-study) nets at median and mean frequencies of every 2 and 2.1 weeks, respectively. In conclusion, the PermaNet nets showed better wash resistance than any of the other commercial nets, and were the only commercial nets tested that truly appeared to be LLIN. There still appears to be scope, however, for the impregnation, and thus the wash-resistance, of even the PermaNet nets to be improved.
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Affiliation(s)
- M H Kayedi
- Disease Control and Vector Biology Unit, Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK.
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Wills AB, Smith SC, Anshebo GY, Graves PM, Endeshaw T, Shargie EB, Damte M, Gebre T, Mosher AW, Patterson AE, Tesema YB, Richards FO, Emerson PM. Physical durability of PermaNet 2.0 long-lasting insecticidal nets over three to 32 months of use in Ethiopia. Malar J 2013; 12:242. [PMID: 23855778 PMCID: PMC3733833 DOI: 10.1186/1475-2875-12-242] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Accepted: 06/23/2013] [Indexed: 11/10/2022] Open
Abstract
Background Ethiopia scaled up net distribution markedly starting in 2006. Information on expected net life under field conditions (physical durability and persistence of insecticidal activity) is needed to improve planning for net replacement. Standardization of physical durability assessment methods is lacking. Methods Permanet®2.0 long-lasting insecticidal bed nets (LLINs), available for distribution in early 2007, were collected from households at three time intervals. The number, size and location of holes were recorded for 189 nets used for three to six months from nine sites (2007) and 220 nets used for 14 to 20 months from 11 sites (2008). In 2009, a “finger/fist” sizing method classified holes in 200 nets used for 26 to 32 months from ten sites into small (<2 cm), medium (> = 2 to < =10 cm) and large (>10 cm) sizes. A proportionate hole index based on both hole number and area was derived from these size classifications. Results After three to six months, 54.5% (95% CI 47.1-61.7%) of 189 LLINs had at least one hole 0.5 cm (in the longest axis) or larger; mean holes per net was 4.4 (SD 8.4), median was 1.0 (Inter Quartile Range [IQR] 0–5) and median size was 1 cm (IQR 1–2). At 14 to 20 months, 85.5% (95% CI 80.1-89.8%) of 220 nets had at least one hole with mean 29.1 (SD 50.1) and median 12 (IQR 3–36.5) holes per net, and median size of 1 cm (IQR 1–2). At 26 to 32 months, 92.5% of 200 nets had at least one hole with a mean of 62.2 (SD 205.4) and median of 23 (IQR 6–55.5) holes per net. The mean hole index was 24.3, 169.1 and 352.8 at the three time periods respectively. Repairs were rarely observed. The majority of holes were in the lower half of the net walls. The proportion of nets in ‘poor’ condition (hole index >300) increased from 0% at three to six months to 30% at 26 to 32 months. Conclusions Net damage began quickly: more than half the nets had holes by three to six months of use, with 40% of holes being larger than 2 cm. Holes continued to accumulate until 92.5% of nets had holes by 26 to 32 months of use. An almost complete lack of repairs shows the need for promoting proper use of nets and repairs, to increase LLIN longevity. Using the hole index, almost one third of the nets were classed as unusable and ineffective after two and a half years of potential use.
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Drame PM, Diallo A, Poinsignon A, Boussari O, Dos Santos S, Machault V, Lalou R, Cornelie S, LeHesran JY, Remoue F. Evaluation of the effectiveness of malaria vector control measures in urban settings of Dakar by a specific anopheles salivary biomarker. PLoS One 2013; 8:e66354. [PMID: 23840448 PMCID: PMC3688790 DOI: 10.1371/journal.pone.0066354] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Accepted: 05/09/2013] [Indexed: 11/24/2022] Open
Abstract
Standard entomological methods for evaluating the impact of vector control lack sensitivity in low-malaria-risk areas. The detection of human IgG specific to Anopheles gSG6-P1 salivary antigen reflects a direct measure of human–vector contact. This study aimed to assess the effectiveness of a range of vector control measures (VCMs) in urban settings by using this biomarker approach. The study was conducted from October to December 2008 on 2,774 residents of 45 districts of urban Dakar. IgG responses to gSG6-P1 and the use of malaria VCMs highly varied between districts. At the district level, specific IgG levels significantly increased with age and decreased with season and with VCM use. The use of insecticide-treated nets, by drastically reducing specific IgG levels, was by far the most efficient VCM regardless of age, season or exposure level to mosquito bites. The use of spray bombs was also associated with a significant reduction of specific IgG levels, whereas the use of mosquito coils or electric fans/air conditioning did not show a significant effect. Human IgG response to gSG6-P1 as biomarker of vector exposure represents a reliable alternative for accurately assessing the effectiveness of malaria VCM in low-malaria-risk areas. This biomarker tool could be especially relevant for malaria control monitoring and surveillance programmes in low-exposure/low-transmission settings.
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Affiliation(s)
- Papa Makhtar Drame
- Institut de Recherche pour le Développement (IRD), UMR-MIVEGEC (IRD224-CNRS5290- Universites Montpellier 1 et 2), Montpellier, France.
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Physical condition of Olyset® nets after five years of utilization in rural western Kenya. Malar J 2013; 12:158. [PMID: 23663421 PMCID: PMC3734157 DOI: 10.1186/1475-2875-12-158] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Accepted: 04/26/2013] [Indexed: 11/21/2022] Open
Abstract
Background Long-lasting insecticidal nets (LLINs) are a cornerstone of malaria control at present, and millions are used each day across the globe. However, there is limited information about the durability of LLINs under different conditions of utilization and there is no consensus about when a LLIN ceases to be protective due to physical deterioration. This knowledge is important for malaria control programmes to plan for procurement and replacement. Methods A cross-sectional survey of 208 households where Olyset® nets distributed five years ago were still present was conducted in the village of Sauri, western Kenya, in the context of the Millennium Villages Project. Information on bed net utilization and maintenance was collected in each household through a structured questionnaire, and one five-year-old Olyset® net from each sampled household was randomly selected and collected for physical examination. All holes larger than 0.5 cm were measured in each net, registering their position, and a hole index was calculated following WHO guidelines. Nets were classified as in good condition, moderately damaged or badly torn based on the hole index. The analysis explored the associations between demographic and socioeconomic characteristics of households, patterns of bed net utilization and maintenance and physical condition of the nets. Additional analysis was conducted using malaria prevalence data collected in a separate survey to explore if there was any association between the condition of the net collected in a household and the presence of malaria parasites in members of that household. Results 81.4% of Olyset® nets distributed five years ago were still present in the surveyed households, and 98.97% of the nets were reportedly used the previous night. Nets had an average of 34.2 holes (95% CI 30.12-38.22), and the mean hole index was 849 (95% CI 711–986), IQR 174–1,135. 15.2% of nets were still in good condition, 46.1% were moderately damaged and 38.7% were badly torn after five years of utilization. There was no association between household characteristics or patterns of bed net utilization or maintenance and physical condition of the nets. The only predictor of the physical condition of the net was the cleanliness at the time of examination. There was a difference of 17.6 percentage points in the proportion of households with at least one blood smear positive for Plasmodium falciparum between households with a net in good condition (5.3%) and those with a moderately damaged or badly torn net (22.9%), 95% CI (0.04-0.305), t=2.77 with unequal variance, p=0.009. Conclusions Olyset® nets were used extensively in Sauri, western Kenya after five years of distribution, regardless of their physical condition. However, only 15% were found in good condition. Nets in good condition seem to be still protective after five years of utilization, while nets with more than 100 cm2 of holed surface may be associated with higher malaria parasitaemia at household level. Continued replacement of damaged nets and promotion of net maintenance and repair may be necessary to maintain the protective effectiveness of LLINs.
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Huho B, Briët O, Seyoum A, Sikaala C, Bayoh N, Gimnig J, Okumu F, Diallo D, Abdulla S, Smith T, Killeen G. Consistently high estimates for the proportion of human exposure to malaria vector populations occurring indoors in rural Africa. Int J Epidemiol 2013; 42:235-47. [PMID: 23396849 PMCID: PMC3600624 DOI: 10.1093/ije/dys214] [Citation(s) in RCA: 122] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Background Insecticide-treated nets (ITNs) and indoor residual spraying (IRS) are highly effective tools for controlling malaria transmission in Africa because the most important vectors, from the Anopheles gambiae complex and the A. funestus group, usually prefer biting humans indoors at night. Methods Matched surveys of mosquito and human behaviour from six rural sites in Burkina Faso, Tanzania, Zambia, and Kenya, with ITN use ranging from 0.2% to 82.5%, were used to calculate the proportion of human exposure to An. gambiae sensu lato and An. funestus s.l. that occurs indoors (πi), as an indicator of the upper limit of personal protection that indoor vector control measures can provide. This quantity was also estimated through use of a simplified binary analysis (πiB) so that the proportions of mosquitoes caught indoors (Pi), and between the first and last hours at which most people are indoors (Pfl) could also be calculated as underlying indicators of feeding by mosquitoes indoors or at night, respectively. Results The vast majority of human exposure to Anopheles bites occurred indoors (πiB = 0.79–1.00). Neither An. gambiae s.l. nor An. funestus s.l. strongly preferred feeding indoors (Pi = 0.40–0.63 and 0.22–0.69, respectively), but they overwhelmingly preferred feeding at times when most humans were indoors (Pfl = 0.78–1.00 and 0.86–1.00, respectively). Conclusions These quantitative summaries of behavioural interactions between humans and mosquitoes constitute a remarkably consistent benchmark with which future observations of vector behaviour can be compared. Longitudinal monitoring of these quantities is vital to evaluate the effectiveness of ITNs and IRS and the need for complementary measures that target vectors outdoors.
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Affiliation(s)
- Bernadette Huho
- Environmental Sciences Thematic Group, Ifakara Health Institute, Dar es Salaam, United Republic of Tanzania
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Mutuku FM, Khambira M, Bisanzio D, Mungai P, Mwanzo I, Muchiri EM, King CH, Kitron U. Physical condition and maintenance of mosquito bed nets in Kwale County, coastal Kenya. Malar J 2013; 12:46. [PMID: 23374429 PMCID: PMC3572415 DOI: 10.1186/1475-2875-12-46] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Accepted: 01/29/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Despite the extensive ownership and use of insecticide-treated nets (ITNs) over the last decade, the effective lifespan of these nets, especially their physical integrity, under true operational conditions is not well-understood. Usefulness of nets declines primarily due to physical damage or loss of insecticidal activity. METHODS A community based cross-sectional survey was used to determine the physical condition and to identify predictors of poor physical condition for bed nets owned by individuals from communities in Kwale County, coastal Kenya. A proportionate hole index (pHI) was used as a standard measure, and the cut-offs for an 'effective net' (offer substantial protection against mosquito bites) and 'ineffective nets' (offer little or no protection against mosquito bites) were determined (pHI ≤88 (about ≤500 cm2 of holes surface area) and pHI of >88 (≥500 cm2 of holes surface area), respectively). RESULTS The vast majority (78%) of the surveyed nets had some holes. The median pHI was 92 (range: 1-2,980). Overall, half of the nets were categorized as 'effective nets' or 'serviceable nets'. Physical deterioration of nets was associated with higher use and washing frequency. Young children and older children were found to use ineffective bed nets significantly more often than infants, while the physical integrity of nets owned by pregnant women was similar to those owned by infants. Estuarine environment inhabitants owned nets with the worst physical condition, while nets owned by the coastal slope inhabitants were in fairly good physical condition. The results suggest that bed nets are optimally utilized when they are new and physically intact. Thereafter, bed net utilization decreases gradually with increasing physical deterioration, with most net owners withdrawing physically damaged nets from routine use.This withdrawal commonly happens following 1.5 years of use, making bed net use the most important predictor of physical integrity. On average, the nets were washed twice within six months prior to the survey. Washing frequency was significantly influenced by the bed net colour and bed net age. Lack of knowledge on reasons for net retreatment and the retreatment procedure was evident, while net repair was minimal and did not seem to improve the physical condition of the nets. The "catch-up" bed net distribution strategies are sufficient for ensuring adequate ownership and utilization of 'effective nets' in the targeted groups, but bi-annual mass distribution is necessary to provide similar ownership and utilization for the other groups not targeted by "catch-up" strategies. CONCLUSIONS Monitoring and maintenance strategies that will deliver locally appropriate education messages on net washing and repair will enhance the effectiveness of malaria control programmes, and further research to assess ineffective nets need is needed.
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Affiliation(s)
- Francis M Mutuku
- Department of Environmental Studies, Emory University, Atlanta, Georgia, USA.
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Waterborne Infectious Diseases, Approaches to Control. Infect Dis (Lond) 2013. [DOI: 10.1007/978-1-4614-5719-0_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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Messenger LA, Matias A, Manana AN, Stiles-Ocran JB, Knowles S, Boakye DA, Coulibaly MB, Larsen ML, Traoré AS, Diallo B, Konaté M, Guindo A, Traoré SF, Mulder CE, Le H, Kleinschmidt I, Rowland M. Multicentre studies of insecticide-treated durable wall lining in Africa and South-East Asia: entomological efficacy and household acceptability during one year of field use. Malar J 2012; 11:358. [PMID: 23107112 PMCID: PMC3547731 DOI: 10.1186/1475-2875-11-358] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Accepted: 10/19/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Indoor residual spraying (IRS) is a primary method of malaria vector control, but its potential impact is constrained by several inherent limitations: spraying must be repeated when insecticide residues decay, householders can tire of the annual imposition and campaign costs are recurrent. Durable lining (DL) can be considered an advanced form of long-lasting IRS where insecticide is gradually released from an aesthetically attractive wall lining material to provide vector control for several years. A multicentre trial was carried out in Equatorial Guinea, Ghana, Mali, South Africa and Vietnam to assess the feasibility, durability, bioefficacy and household acceptability of DL, compared to conventional IRS or insecticide-treated curtains (LLITCs), in a variety of operational settings. METHODS This study was conducted in 220 households in traditional rural villages over 12-15 months. In all sites, rolls of DL were cut to fit house dimensions and fixed to interior wall surfaces (usually with nails and caps) by trained teams. Acceptability was assessed using a standardized questionnaire covering such topics as installation, exposure reactions, entomology, indoor environment, aesthetics and durability. Bioefficacy of interventions was evaluated using WHO cone bioassay tests at regular intervals throughout the year. RESULTS The deltamethrin DL demonstrated little to no decline in bioefficacy over 12-15 months, supported by minimal loss of insecticide content. By contrast, IRS displayed a significant decrease in bioactivity by 6 months and full loss after 12 months. The majority of participants in DL households perceived reductions in mosquito density (93%) and biting (82%), but no changes in indoor temperature (83%). Among those households that wanted to retain the DL, 73% cited protective reasons, 20% expressed a desire to keep theirs for decoration and 7% valued both qualities equally. In Equatorial Guinea, when offered a choice of vector control product at the end of the trial (DL, IRS or LLITCs), DL consistently emerged as the most popular intervention regardless of the earlier household allocation. CONCLUSIONS Just as long-lasting insecticidal nets overcame several of the technical and logistical constraints associated with conventionally treated nets and then went to scale, this study demonstrates the potential of DL to sustain user compliance and overcome the operational challenges associated with IRS.
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Affiliation(s)
- Louisa A Messenger
- Faculty of Infectious Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK.
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Kweka EJ, Munga S, Mahande AM, Msangi S, Mazigo HD, Adrias AQ, Matias JR. Protective efficacy of menthol propylene glycol carbonate compared to N, N-diethyl-methylbenzamide against mosquito bites in Northern Tanzania. Parasit Vectors 2012; 5:189. [PMID: 22950604 PMCID: PMC3444865 DOI: 10.1186/1756-3305-5-189] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Accepted: 08/23/2012] [Indexed: 01/07/2023] Open
Abstract
Background The reduction of malaria parasite transmission by preventing human-vector contact is critical in lowering disease transmission and its outcomes. This underscores the need for effective and long lasting arthropod/insect repellents. Despite the reduction in malaria transmission and outcomes in Tanzania, personal protection against mosquito bites is still not well investigated. This study sought to determine the efficacy of menthol propylene glycol carbonate (MR08), Ocimum suave as compared to the gold standard repellent N, N-diethyl-methylbenzamide (DEET), either as a single dose or in combination (blend), both in the laboratory and in the field against Anopheles gambiae s.l and Culex quinquefasciatus. Methods In the laboratory evaluations, repellents were applied on one arm while the other arm of the same individual was treated with a base cream. Each arm was separately exposed in cages with unfed female mosquitoes. Repellents were evaluated either as a single dose or as a blend. Efficacy of each repellent was determined by the number of mosquitoes that landed and fed on treated arms as compared to the control or among them. In the field, evaluations were performed by human landing catches at hourly intervals from 18:00 hr to 01:00 hr. Results A total of 2,442 mosquitoes were collected during field evaluations, of which 2,376 (97.30%) were An. gambiae s.l while 66 (2.70%) were Cx. quinquefaciatus. MR08 and DEET had comparatively similar protective efficacy ranging from 92% to 100 for both single compound and blends. These findings indicate that MR08 has a similar protective efficacy as DEET for personal protection outside bed nets when used singly and in blends. Because of the personal protection provided by MR08, DEET and blends as topical applicants in laboratory and field situations, these findings suggest that, these repellents could be used efficiently in the community to complement existing tools. Overall, Cx. quinquefasciatus were significantly prevented from blood feeding compared to An. gambiae s.l. Conclusion The incorporation of these topical repellents for protection against insect bites can be of additional value in the absence or presence of IRS and ITNs coverage. However, a combination of both the physical (bed nets) and the repellent should be used in an integrated manner for maximum protection, especially before going to bed. Additional research is needed to develop repellents with longer duration of protection.
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Affiliation(s)
- Eliningaya J Kweka
- Division of Livestock and Human Diseases Vector Control, Mosquito section, Tropical Pesticides Research Institute, P.O.BOX 3024, Arusha, Tanzania.
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