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Praulins G, Murphy-Fegan A, Gillespie J, Mechan F, Gleave K, Lees R. Unpacking WHO and CDC Bottle Bioassay Methods: A Comprehensive Literature Review and Protocol Analysis Revealing Key Outcome Predictors. Gates Open Res 2024; 8:56. [PMID: 39170853 PMCID: PMC11335745 DOI: 10.12688/gatesopenres.15433.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/17/2024] [Indexed: 08/23/2024] Open
Abstract
Background Resistance monitoring is a key element in controlling vector-borne diseases. The World Health Organization (WHO) and Centres for Disease Control and Prevention (CDC) have each developed bottle bioassay methods for determining insecticide susceptibility in mosquito vectors which are used globally. Methods This study aimed to identify variations in bottle bioassay methodologies and assess the potential impact on the data that is generated. Our approach involved a systematic examination of existing literature and protocols from WHO and CDC, with a focus on the specifics of reported methodologies, variation between versions, and reported outcomes. Building on this, we experimentally evaluated the impact of several variables on bioassay results. Results Our literature review exposed a significant inconsistency in the how bioassay methods are reported, hindering reliable interpretation of data and the ability to compare results between studies. The experimental research provided further insight by specifically identifying two key factors that influence the outcomes of bioassays: mosquito dry weight and relative humidity (RH). This finding not only advances our comprehension of these assays but also underscores the importance of establishing precisely defined methodologies for resistance monitoring. The study also demonstrates the importance of controlling bioassay variables, noting the significant influence of wing length, as an indicator of mosquito size, on mortality rates in standardized bioassays. Conclusions Generating data with improved protocol consistency and precision will not only deepen our understanding of resistance patterns but also better inform vector control measures. We call for continued research and collaboration to refine and build consensus on bioassay techniques, to help bolster the global effort against vector-borne diseases like malaria.
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Affiliation(s)
- Giorgio Praulins
- Innovation to Impact (I2I), Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Annabel Murphy-Fegan
- Innovation to Impact (I2I), Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Jack Gillespie
- Innovation to Impact (I2I), Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Frank Mechan
- Innovation to Impact (I2I), Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Katherine Gleave
- Innovation to Impact (I2I), Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Rosemary Lees
- Innovation to Impact (I2I), Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
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Myers A, Fagbohoun J, Houetohossou G, Ndombidje B, Govoetchan R, Todjinou D, Ngufor C. Identifying suitable methods for evaluating the sterilizing effects of pyriproxyfen on adult malaria vectors: a comparison of the oviposition and ovary dissection methods. Malar J 2024; 23:164. [PMID: 38789998 PMCID: PMC11127354 DOI: 10.1186/s12936-024-04983-2] [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: 11/21/2023] [Accepted: 05/14/2024] [Indexed: 05/26/2024] Open
Abstract
BACKGROUND Nets containing pyriproxyfen, an insect growth regulator that sterilizes adult mosquitoes, have become available for malaria control. Suitable methods for investigating vector susceptibility to pyriproxyfen and evaluating its efficacy on nets need to be identified. The sterilizing effects of pyriproxyfen on adult malaria vectors can be assessed by measuring oviposition or by dissecting mosquito ovaries to determine damage by pyriproxyfen (ovary dissection). METHOD Laboratory bioassays were performed to compare the oviposition and ovary dissection methods for monitoring susceptibility to pyriproxyfen in wild malaria vectors using WHO bottle bioassays and for evaluating its efficacy on nets in cone bioassays. Blood-fed mosquitoes of susceptible and pyrethroid-resistant strains of Anopheles gambiae sensu lato were exposed to pyriproxyfen-treated bottles (100 μg and 200 μg) and to unwashed and washed pieces of a pyriproxyfen long-lasting net in cone bioassays. Survivors were assessed for the sterilizing effects of pyriproxyfen using both methods. The methods were compared in terms of their reliability, sensitivity, specificity, resources (cost and time) required and perceived difficulties by trained laboratory technicians. RESULTS The total number of An. gambiae s.l. mosquitoes assessed for the sterilizing effects of pyriproxyfen were 1745 for the oviposition method and 1698 for the ovary dissection method. Fertility rates of control unexposed mosquitoes were significantly higher with ovary dissection compared to oviposition in both bottle bioassays (99-100% vs. 34-59%, P < 0.05) and cone bioassays (99-100% vs. 18-33%, P < 0.001). Oviposition rates of control unexposed mosquitoes were lower with wild pyrethroid-resistant An. gambiae s.l. Cové, compared to the laboratory-maintained reference susceptible An gambiae sensu stricto Kisumu (18-34% vs. 58-76%, P < 0.05). Sterilization rates of the Kisumu strain in bottle bioassays with the pyriproxyfen diagnostic dose (100 μg) were suboptimal with the oviposition method (90%) but showed full susceptibility with ovary dissection (99%). Wild pyrethroid-resistant Cové mosquitoes were fully susceptible to pyriproxyfen in bottle bioassays using ovary dissection (> 99%), but not with the oviposition method (69%). Both methods showed similar levels of sensitivity (89-98% vs. 89-100%). Specificity was substantially higher with ovary dissection compared to the oviposition method in both bottle bioassays (99-100% vs. 34-48%) and cone tests (100% vs.18-76%). Ovary dissection was also more sensitive for detecting the residual activity of pyriproxyfen in a washed net compared to oviposition. The oviposition method though cheaper, was less reliable and more time-consuming. Laboratory technicians preferred ovary dissection mostly due to its reliability. CONCLUSION The ovary dissection method was more accurate, more reliable and more efficient compared to the oviposition method for evaluating the sterilizing effects of pyriproxyfen on adult malaria vectors in susceptibility bioassays and for evaluating the efficacy of pyriproxyfen-treated nets.
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Affiliation(s)
- Alesha Myers
- London School of Hygiene and Tropical Medicine (LSHTM), London, WC1E 7HT, UK
| | - Josias Fagbohoun
- Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin
- Panafrican Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
| | | | - Boris Ndombidje
- Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin
- Panafrican Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
| | - Renaud Govoetchan
- London School of Hygiene and Tropical Medicine (LSHTM), London, WC1E 7HT, UK
- Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin
- Panafrican Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
- African Institute for Research in Infectious Diseases (AIRID), Cotonou, Benin
| | - Damien Todjinou
- Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin
- Panafrican Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
| | - Corine Ngufor
- London School of Hygiene and Tropical Medicine (LSHTM), London, WC1E 7HT, UK.
- Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin.
- Panafrican Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin.
- African Institute for Research in Infectious Diseases (AIRID), Cotonou, Benin.
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Zoungbédji DM, Padonou GG, Sovi A, Konkon AK, Salako AS, Azondékon R, Sidick A, Ahouandjinou JM, Towakinou L, Ossè R, Aïkpon R, Affoukou C, Baba-Moussa L, Akogbéto M. Bio-efficacy of Olyset ® Plus, PermaNet ® 3.0 and Interceptor ® G2 on pyrethroid-resistant populations of Anopheles gambiae s.l. prior to the June 2023 net distribution campaign in Benin, West Africa. Trop Med Health 2024; 52:34. [PMID: 38689360 PMCID: PMC11059851 DOI: 10.1186/s41182-024-00599-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Accepted: 04/17/2024] [Indexed: 05/02/2024] Open
Abstract
BACKGROUND This study investigates the effectiveness of new-generation mosquito nets, like Olyset® Plus and PermaNet® 3.0, and dual-action nets such as Interceptor® G2, against pyrethroid-resistant Anopheles gambiae mosquitoes following the 2023 mass distribution of long-lasting insecticidal nets in Benin. METHODS We tested wild mosquito populations from six communes in Benin against various pyrethroid (permethrin 0.75%, alphacypermethrin 0.05%, and deltamethrin 0.05%) using WHO tube tests. Additionally, we exposed mosquitoes to chlorfenapyr 100 µg/ml using the CDC bottle bioassay method. A subset of mosquitoes underwent biochemical and PCR tests to check the overexpression of metabolic enzymes and the Kdr L1014F mutation. We evaluated the effectiveness of Olyset® Plus, PermaNet® 3.0, and Interceptor® G2 nets using cone and tunnel tests on both laboratory and field populations of An. gambiae. RESULTS Overall, the highest mortality rate was 60% with pyrethroid and 98 to100% with chlorfenapyr. In cone tests, all three types of nets induced mortality rates above 80% in the susceptible laboratory strain of An. gambiae. Notably, Olyset® Plus showed the highest mortality rates for pyrethroid-resistant mosquitoes in cone tests, ranging from 81.03% (95% CI: 68.59-90.13) in Djougou to 96.08% (95% CI: 86.54-99.52) in Akpro-Missérété. PermaNet® 3.0 had variable rates, from 42.5% (95% CI: 27.04-59.11) in Djougou to 58.54% (95% CI: 42.11-73.68) in Porto-Novo. However, revealed good results for Interceptor® G2, with 94% (95% CI: 87.40-97.77) mortality and 89.09% blood sampling inhibition in local populations of An. gambiae. In comparison, Interceptor® had lower rates of 17% (95% CI: 10.23-25.82) and 60%, respectively. CONCLUSION These results suggest that tunnel tests are effective for evaluating dual-active ingredient nets. Additionally, Interceptor® G2 and PBO nets like Olyset® Plus could be considered as alternatives against pyrethroid-resistant mosquitoes.
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Affiliation(s)
- David Mahouton Zoungbédji
- Centre de Recherche Entomologique de Cotonou (CREC), 06 BP 2604, Cotonou, Benin.
- Faculté des Sciences et Techniques de l'Université d'Abomey-Calavi, Abomey-Calavi, Benin.
| | - Germain Gil Padonou
- Centre de Recherche Entomologique de Cotonou (CREC), 06 BP 2604, Cotonou, Benin
- Faculté des Sciences et Techniques de l'Université d'Abomey-Calavi, Abomey-Calavi, Benin
| | - Arthur Sovi
- Centre de Recherche Entomologique de Cotonou (CREC), 06 BP 2604, Cotonou, Benin
- Faculty of Agronomy, University of Parakou, Parakou, Benin
- Faculty of Infectious and Tropical Diseases, The London School of Hygiene and Tropical Medicine, London, UK
| | - Alphonse Keller Konkon
- Centre de Recherche Entomologique de Cotonou (CREC), 06 BP 2604, Cotonou, Benin
- Faculté des Sciences et Techniques de l'Université d'Abomey-Calavi, Abomey-Calavi, Benin
| | | | - Roseric Azondékon
- Centre de Recherche Entomologique de Cotonou (CREC), 06 BP 2604, Cotonou, Benin
| | - Aboubakar Sidick
- Centre de Recherche Entomologique de Cotonou (CREC), 06 BP 2604, Cotonou, Benin
| | | | - Linda Towakinou
- Centre de Recherche Entomologique de Cotonou (CREC), 06 BP 2604, Cotonou, Benin
| | - Razaki Ossè
- Centre de Recherche Entomologique de Cotonou (CREC), 06 BP 2604, Cotonou, Benin
- École de Gestion et d'exploitation des Systèmes d'élevage, Université Nationale d'Agriculture, Kétou, Benin
| | - Rock Aïkpon
- Programme National de Lutte Contre le Paludisme, Cotonou, Benin
- Université Nationale des Sciences, Technologies, Ingénierie et Mathématiques (UNSTIM), Abomey, Benin
| | | | - Lamine Baba-Moussa
- Faculté des Sciences et Techniques de l'Université d'Abomey-Calavi, Abomey-Calavi, Benin
- Laboratoire de Biologie et de Typage Moléculaire en Microbiologie (LBTMM), département de Biochimie et de Biologie Cellulaire (BBC), Université de Abomey-Calavi (UAC), Abomey-Calavi, Benin
| | - Martin Akogbéto
- Centre de Recherche Entomologique de Cotonou (CREC), 06 BP 2604, Cotonou, Benin
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Gleave K, Lees RS. Better methods, better data: landscaping the priorities for improving methodologies in vector control. Gates Open Res 2024; 8:27. [PMID: 39035850 PMCID: PMC11259587 DOI: 10.12688/gatesopenres.15399.1] [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] [Accepted: 03/07/2024] [Indexed: 07/23/2024] Open
Abstract
This article addresses the evolving challenges in evaluating insecticide-based tools for vector control. In response to the emergence of insecticide resistance in major malaria vectors, novel chemistries and products are coming to market, and there is a need to review the available testing methodologies. Commonly used methods for evaluating insecticides, such as the World Health Organization (WHO) cone bioassay, are inadequate for the diverse range of tools now available. Innovation to Impact (I2I) has studied the variability in laboratory methods, with the aim of identifying key factors that contribute to variation and providing recommendations to tighten up protocols. The I2I Methods Landscape is a living document which presents a review of existing methods for evaluating vector control tools, with the scope currently extending to insecticide-treated nets (ITNs) and indoor residual sprays (IRS). The review reveals a lack of validation for many commonly used vector control methods, highlighting the need for improved protocols to enhance reliability and robustness of the data that is generated to make decisions in product development, evaluation, and implementation. A critical aspect highlighted by this work is the need for tailored methods to measure endpoints relevant to the diverse modes of action of novel insecticides. I2I envisage that the Methods Landscape will serve as a decision-making tool for researchers and product manufacturers in selecting appropriate methods, and a means to prioritise research and development. We call for collective efforts in the pro-active development, validation, and consistent implementation of suitable methods in vector control to produce the data needed to make robust decisions.
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Affiliation(s)
- Katherine Gleave
- Innovation to Impact (I2I), Liverpool School of Tropical Medicine, Liverpool, Merseyside, L17 9QQ, UK
| | - Rosemary Susan Lees
- Innovation to Impact (I2I), Liverpool School of Tropical Medicine, Liverpool, Merseyside, L17 9QQ, UK
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Agbevo A, Ahogni I, Menze B, Tungu P, Kemibala EE, Govoetchan R, Wondji C, Padonou GG, Ngufor C. Community evaluation of the physical and insecticidal durability of DuraNet® Plus, an alpha-cypermethrin and piperonyl butoxide incorporated mosquito net: protocol for a multi-country study in West, Central and East Africa. Arch Public Health 2023; 81:202. [PMID: 37986195 PMCID: PMC10662531 DOI: 10.1186/s13690-023-01217-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Accepted: 11/09/2023] [Indexed: 11/22/2023] Open
Abstract
BACKGROUND Pyrethroid-PBO nets have demonstrated improved impact against clinical malaria transmitted by pyrethroid resistant mosquito vectors and are being scaled up across Africa. However very little is known about their physical and insecticidal durability under operational conditions. This study will investigate the attrition, fabric integrity, insecticide content and bioefficacy of DuraNet® Plus, a new WHO prequalified alphacypermethrin and PBO incorporated net developed by Shobikaa Impex Private Limited over 3 years of field use in communities in Benin, Cameroon and Tanzania. METHODS The study will be conducted in parallel in selected villages in Zakpota District in Benin, Mbalmayo, District in Cameroon and Muheza District in Tanzania. In each country, ~ 1800 households will be recruited and randomised to receive DuraNet® Plus or DuraNet® (a WHO prequalified alphacypermethrin-only ITN). Follow up surveys will be performed at 1 month post distribution to investigate adverse events and subsequently every 6-12 months to assess ITN attrition and fabric integrity following standard WHO procedures. A second cohort of nets will be withdrawn every 6-12 months and assessed for alpha-cypermethrin and PBO content and for entomological activity in laboratory bioassays (cone bioassays and tunnel tests). Alpha-cypermethrin bioefficacy will be monitored using the susceptible Anopheles gambiae Kisumu strain in cone bioassays while PBO bioefficacy will be monitored using pyrethroid resistant strains with overexpressed P450 enzymes in tunnel tests to determine the proportion of efficacious nets (≥ 95% knockdown, ≥ 80% mortality or ≥ 90% blood feeding inhibition in tunnels) at each time point. Nets withdrawn at 12, 24 and 36 months from each country will also be tested in experimental hut trials against wild free-flying pyrethroid resistant Anopheles gambiae sl in Côvè Benin to investigate the superiority of DuraNet® Plus over DuraNet® at each time point under semi field conditions. CONCLUSION This large-scale multi country trial will provide useful information on the durability of a pyrethroid-PBO net (DuraNet® Plus) in 3 different regions in sub-Saharan Africa. The methods proposed for bioefficacy testing could also contribute towards the development of new standardised guidelines for monitoring the insecticidal efficacy of pyrethroid-PBO nets under operational conditions.
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Affiliation(s)
- Abel Agbevo
- Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin
- Panafrican Malaria Vector Research Consortium (PAMVERC-BENIN), Cotonou, Benin
- London School of Hygiene and Tropical Medicine (LSHTM), London, UK
| | - Idelphonse Ahogni
- Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin
- Panafrican Malaria Vector Research Consortium (PAMVERC-BENIN), Cotonou, Benin
| | - Benjamin Menze
- Centre for Research in Infectious Diseases (CRID) ), Yaoundé, Cameroon
| | - Patrick Tungu
- Vector Control Training Centre (VCTC), Muheza, Tanzania
- National Institute for Medical Research (NIMR), Amani Research Centre, Tanga, Tanzania
| | | | - Renaud Govoetchan
- Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin
- Panafrican Malaria Vector Research Consortium (PAMVERC-BENIN), Cotonou, Benin
- London School of Hygiene and Tropical Medicine (LSHTM), London, UK
| | - Charles Wondji
- Centre for Research in Infectious Diseases (CRID) ), Yaoundé, Cameroon
- Liverpool School of Tropical Medicine, Liverpool, UK
| | | | - Corine Ngufor
- Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin.
- Panafrican Malaria Vector Research Consortium (PAMVERC-BENIN), Cotonou, Benin.
- London School of Hygiene and Tropical Medicine (LSHTM), London, UK.
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Matope A, Lees RS, Spiers A, Foster GM. A bioassay method validation framework for laboratory and semi-field tests used to evaluate vector control tools. Malar J 2023; 22:289. [PMID: 37770855 PMCID: PMC10540336 DOI: 10.1186/s12936-023-04717-w] [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: 03/18/2023] [Accepted: 09/13/2023] [Indexed: 09/30/2023] Open
Abstract
Vector control interventions play a fundamental role in the control and elimination of vector-borne diseases. The evaluation of vector control products relies on bioassays, laboratory and semi-field tests using live insects to assess the product's effectiveness. Bioassay method development requires a rigorous validation process to ensure that relevant methods are used to capture appropriate entomological endpoints which accurately and precisely describe likely efficacy against disease vectors as well as product characteristics within the manufacturing tolerance ranges for insecticide content specified by the World Health Organization. Currently, there are no standardized guidelines for bioassay method validation in vector control. This report presents a framework for bioassay validation that draws on accepted validation processes from the chemical and healthcare fields and which can be applied for evaluating bioassays and semi-field tests in vector control. The validation process has been categorized into four stages: preliminary development; feasibility experiments; internal validation, and external validation. A properly validated method combined with an appropriate experimental design and data analyses that account for both the variability of the method and the product is needed to generate reliable estimates of product efficacy to ensure that at-risk communities have timely access to safe and reliable vector control products.
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Affiliation(s)
- Agnes Matope
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Rosemary S Lees
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
- Innovation to Impact (I2I), Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Angus Spiers
- Innovation to Impact (I2I), Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Geraldine M Foster
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.
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Ngufor C, Fongnikin A, Fagbohoun J, Agbevo A, Syme T, Ahoga J, Accrombessi M, Protopopoff N, Cook J, Churcher TS, Padonou GG, Govoetchan R, Akogbeto M. Evaluating the attrition, fabric integrity and insecticidal durability of two dual active ingredient nets (Interceptor ® G2 and Royal ® Guard): methodology for a prospective study embedded in a cluster randomized controlled trial in Benin. Malar J 2023; 22:276. [PMID: 37716970 PMCID: PMC10504698 DOI: 10.1186/s12936-023-04708-x] [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: 04/28/2023] [Accepted: 09/07/2023] [Indexed: 09/18/2023] Open
Abstract
BACKGROUND Following the World Health Organization (WHO) endorsement of dual active ingredient (AI) nets, an increased uptake of pyrethroid-chlorfenapyr and pyrethroid-pyriproxyfen nets is expected. Studies evaluating their physical and insecticidal durability are essential for making programmatic and procurement decisions. This paper describes the methodology for a prospective study to evaluate the attrition, fabric integrity, insecticidal durability of Interceptor® G2 (alpha-cypermethrin-chlorfenapyr) and Royal Guard® (alpha-cypermethrin-pyriproxyfen), compared to Interceptor® (alpha-cypermethrin), embedded in a 3-arm cluster randomized controlled trial (cRCT) in the Zou Department of Benin. METHODS Ten clusters randomly selected from each arm of the cRCT will be used for the study. A total of 750 ITNs per type will be followed in 5 study clusters per arm to assess ITN attrition and fabric integrity at 6-, 12-, 24- and 36-months post distribution, using standard WHO procedures. A second cohort of 1800 nets per type will be withdrawn every 6 months from all 10 clusters per arm and assessed for chemical content and biological activity in laboratory bioassays at each time point. Alpha-cypermethrin bioefficacy in Interceptor® and Royal Guard® will be monitored in WHO cone bioassays and tunnel tests using the susceptible Anopheles gambiae Kisumu strain. The bioefficacy of the non-pyrethroid insecticides (chlorfenapyr in Interceptor® G2 and pyriproxyfen in Royal Guard®) will be monitored using the pyrethroid-resistant Anopheles coluzzii Akron strain. Chlorfenapyr activity will be assessed in tunnel tests while pyriproxyfen activity will be assessed in cone bioassays in terms of the reduction in fertility of blood-fed survivors observed by dissecting mosquito ovaries. Nets withdrawn at 12, 24 and 36 months will be tested in experimental hut trials within the cRCT study area against wild free-flying pyrethroid resistant An. gambiae sensu lato to investigate their superiority to Interceptor® and to compare them to ITNs washed 20 times for experimental hut evaluation studies. Mechanistic models will also be used to investigate whether entomological outcomes with each dual ITN type in experimental hut trials can predict their epidemiological performance in the cRCT. CONCLUSION This study will provide information on the durability of two dual AI nets (Interceptor® G2 and Royal Guard®) in Benin and will help identify suitable methods for monitoring the durability of their insecticidal activity under operational conditions. The modelling component will determine the capacity of experimental hut trials to predict the epidemiological performance of dual AI nets across their lifespan.
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Affiliation(s)
- Corine Ngufor
- London School of Hygiene and Tropical Medicine (LSHTM), London, WC1E 7HT, UK.
- Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin.
- Panafrican Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin.
| | - Augustin Fongnikin
- Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin
- Panafrican Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
| | - Josias Fagbohoun
- Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin
- Panafrican Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
| | - Abel Agbevo
- London School of Hygiene and Tropical Medicine (LSHTM), London, WC1E 7HT, UK
- Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin
- Panafrican Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
| | - Thomas Syme
- London School of Hygiene and Tropical Medicine (LSHTM), London, WC1E 7HT, UK
- Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin
- Panafrican Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
| | - Juniace Ahoga
- Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin
- Panafrican Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
| | - Manfred Accrombessi
- London School of Hygiene and Tropical Medicine (LSHTM), London, WC1E 7HT, UK
- Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin
| | - Natacha Protopopoff
- London School of Hygiene and Tropical Medicine (LSHTM), London, WC1E 7HT, UK
| | - Jackie Cook
- London School of Hygiene and Tropical Medicine (LSHTM), London, WC1E 7HT, UK
| | - Thomas S Churcher
- MRC Centre for Global Infectious Disease Analysis, Infectious Disease Epidemiology, Imperial College London, Norfolk Place, London, W2 1PG, UK
| | | | - Renaud Govoetchan
- London School of Hygiene and Tropical Medicine (LSHTM), London, WC1E 7HT, UK
- Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin
- Panafrican Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
| | - Martin Akogbeto
- Centre de Recherches Entomologiques de Cotonou (CREC), Cotonou, Benin
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Zoungbédji DM, Padonou GG, Konkon AK, Hougbe S, Sagbohan H, Kpanou C, Salako AS, Ossè R, Aïkpon R, Afoukou C, Sidick A, Akinro B, Chitou S, Gnanguénon V, Condo P, Hassani AS, Impoinvil D, Akogbéto M. Assessing the susceptibility and efficacy of traditional neurotoxic (pyrethroid) and new-generation insecticides (chlorfenapyr, clothianidin, and pyriproxyfen), on wild pyrethroid-resistant populations of Anopheles gambiae from southern Benin. Malar J 2023; 22:245. [PMID: 37626366 PMCID: PMC10463682 DOI: 10.1186/s12936-023-04664-6] [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: 04/01/2023] [Accepted: 08/07/2023] [Indexed: 08/27/2023] Open
Abstract
BACKGROUND The objective of this study was to determine the susceptibility of wild Anopheles gambiae sensu lato (s.l.) from southern Benin to the new insecticides (chlorfenapyr (CFP), pyriproxyfen (PPF), and clothianidin (CTD)) and assess the efficacy of insecticide-treated bed nets (ITNs) that contain these new products. METHODS Wild An. gambiae from the Benin communes of Allada, Ifangni, Akpro-Missérété, and Porto-Novo were tested for their susceptibility to CFP and PPF using the WHO bottle tests, and pyrethroids (alpha-cypermethrin, deltamethrin, and permethrin) and CTD using WHO tube tests. WHO cone tests were used to evaluate the efficacy of Interceptor® (which contains alpha-cypermethrin (ACM) only), Interceptor® G2, (CFP + ACM), and Royal Guard® nets (PPF + ACM). The ovaries of blood-fed An. gambiae from Ifangni exposed to a new PPF net were dissected, and egg development status was examined using Christopher's stages to determine the fertility status of the mosquitoes. Using a standardized protocol, the oviposition rate and oviposition inhibition rate were calculated from live blood-fed An. gambiae placed in oviposition chambers after exposure to PPF. RESULTS In all four mosquito populations, pyrethroid mortality ranged from 5 to 80%, while chlorfenapyr and clothianidin mortality ranged from 98 to 100%. At Ifangni, all mosquitoes exposed to Royal Guard® nets were infertile (100%) while the majority (74.9%) of mosquitoes exposed to Interceptor® nets had fully developed their eggs to Christopher's stage V. The oviposition inhibition rate after exposure of the mosquitoes to the PPF was 99% for the wild population of An. gambiae s.l. and the susceptible laboratory strain, An. gambiae sensu stricto (Kisumu). CONCLUSIONS The results of this study suggest that pyrethroid-resistant An. gambiae from the selected communes in southern Benin are susceptible to chlorfenapyr, clothianidin, and pyriproxyfen. In addition, based on bioassay results, new and unused Interceptor® G2 and Royal Guard® nets were effective on Ifangni's mosquito populations. Despite the availability of new effective insecticides, continued vigilance is needed in Benin. Therefore, monitoring of resistance to these insecticides will continue to periodically update the Benin national insecticide resistance database and management plan.
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Affiliation(s)
- David Mahouton Zoungbédji
- Centre de Recherche Entomologique de Cotonou (CREC), 06 BP 2604, Cotonou, Benin.
- Faculté des Sciences et Techniques, Université d'Abomey-Calavi, Godomey, Benin.
| | - Germain Gil Padonou
- Centre de Recherche Entomologique de Cotonou (CREC), 06 BP 2604, Cotonou, Benin
- Faculté des Sciences et Techniques, Université d'Abomey-Calavi, Godomey, Benin
| | - Alphonse Keller Konkon
- Centre de Recherche Entomologique de Cotonou (CREC), 06 BP 2604, Cotonou, Benin
- Faculté des Sciences et Techniques, Université d'Abomey-Calavi, Godomey, Benin
| | - Steve Hougbe
- Centre de Recherche Entomologique de Cotonou (CREC), 06 BP 2604, Cotonou, Benin
| | - Hermann Sagbohan
- Centre de Recherche Entomologique de Cotonou (CREC), 06 BP 2604, Cotonou, Benin
- Faculté des Sciences et Techniques, Université d'Abomey-Calavi, Godomey, Benin
| | - Casimir Kpanou
- Centre de Recherche Entomologique de Cotonou (CREC), 06 BP 2604, Cotonou, Benin
| | | | - Razaki Ossè
- Centre de Recherche Entomologique de Cotonou (CREC), 06 BP 2604, Cotonou, Benin
| | - Rock Aïkpon
- Programme National de Lutte Contre Le Paludisme, Cotonou, Benin
| | | | - Aboubakar Sidick
- Centre de Recherche Entomologique de Cotonou (CREC), 06 BP 2604, Cotonou, Benin
| | - Bruno Akinro
- Centre de Recherche Entomologique de Cotonou (CREC), 06 BP 2604, Cotonou, Benin
| | - Saïd Chitou
- Centre de Recherche Entomologique de Cotonou (CREC), 06 BP 2604, Cotonou, Benin
| | - Virgile Gnanguénon
- US President's Malaria Initiative, US Agency for International Development, Cotonou, Benin
| | - Patrick Condo
- US President's Malaria Initiative, US Agency for International Development, Cotonou, Benin
| | - Ahmed Saadani Hassani
- US President's Malaria Initiative, US Centers for Disease Control and Prevention, Cotonou, Benin
| | - Daniel Impoinvil
- US President's Malaria Initiative, US Centers for Disease Control and Prevention, Atlanta, USA
| | - Martin Akogbéto
- Centre de Recherche Entomologique de Cotonou (CREC), 06 BP 2604, Cotonou, Benin
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Mbuba E, Odufuwa OG, Moore J, Mmbaga S, Tchicaya E, Edi C, Chalageri V, Uragayala S, Sharma A, Rahi M, Raghavendra K, Eapen A, Koenker H, Ross A, Moore SJ. Multi-country evaluation of the durability of pyrethroid plus piperonyl-butoxide insecticide-treated nets: study protocol. Malar J 2023; 22:30. [PMID: 36707886 PMCID: PMC9881340 DOI: 10.1186/s12936-023-04465-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Accepted: 01/20/2023] [Indexed: 01/29/2023] Open
Abstract
BACKGROUND Mass distributions of long-lasting insecticidal nets (LLINs) have contributed to large reductions in the malaria burden. However, this success is in jeopardy due in part to the increasing pyrethroid-resistant mosquito population as well as low LLINs coverage in various areas because the lifespan of LLINs is often shorter than the interval between replenishment campaigns. New insecticide-treated nets (ITNs) containing pyrethroid and piperonyl-butoxide (PBO) have shown a greater reduction in the incidence of malaria than pyrethroid LLINs in areas with pyrethroid-resistant mosquitoes. However, the durability (attrition, bio-efficacy, physical integrity and chemical retainment) of pyrethroid-PBO ITNs under operational settings has not been fully characterized. This study will measure the durability of pyrethroid-PBO ITNs to assess whether they meet the World Health Organization (WHO) three years of operational performance criteria required to be categorized as "long-lasting". METHODS A prospective household randomized controlled trial will be conducted simultaneously in Tanzania, India and Côte d'Ivoire to estimate the field durability of three pyrethroid-PBO ITNs (Veeralin®, Tsara® Boost, and Olyset® Plus) compared to a pyrethroid LLIN: MAGNet®. Durability monitoring will be conducted up to 36 months post-distribution and median survival in months will be calculated. The proportion of ITNs: (1) lost (attrition), (2) physical integrity, (3) resistance to damage score, (4) meeting WHO bio-efficacy (≥ 95% knockdown after 1 h or ≥ 80% mortality after 24 h for WHO cone bioassay, or ≥ 90% blood-feeding inhibition or ≥ 80% mortality after 24 h for WHO Tunnel tests) criteria against laboratory-reared resistant and susceptible mosquitoes, and insecticidal persistence over time will be estimated. The non-inferiority of Veeralin® and Tsara® Boost to the first-in-class, Olyset® Plus will additionally be assessed for mortality, and the equivalence of 20 times washed ITNs compared to field aged ITNs will be assessed for mortality and blood-feeding inhibition endpoints in the Ifakara Ambient Chamber Test, Tanzania. CONCLUSION This will be the first large-scale prospective household randomized controlled trial of pyrethroid-PBO ITNs in three different countries in East Africa, West Africa and South Asia, simultaneously. The study will generate information on the replenishment intervals for PBO nets.
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Affiliation(s)
- Emmanuel Mbuba
- grid.414543.30000 0000 9144 642XVector Control Product Testing Unit, Environmental Health and Ecological Science, Ifakara Health Institute, P.O. Box 74, Bagamoyo, Tanzania ,grid.416786.a0000 0004 0587 0574Swiss Tropical and Public Health Institute, Kreuzstrasse 2, 4123 Allschwil, Switzerland ,grid.6612.30000 0004 1937 0642University of Basel, St. Petersplatz 1, 4002 Basel, Switzerland
| | - Olukayode G. Odufuwa
- grid.414543.30000 0000 9144 642XVector Control Product Testing Unit, Environmental Health and Ecological Science, Ifakara Health Institute, P.O. Box 74, Bagamoyo, Tanzania ,grid.416786.a0000 0004 0587 0574Swiss Tropical and Public Health Institute, Kreuzstrasse 2, 4123 Allschwil, Switzerland ,grid.6612.30000 0004 1937 0642University of Basel, St. Petersplatz 1, 4002 Basel, Switzerland ,grid.8991.90000 0004 0425 469XEpidemiology and Population Health Department, London School of Hygiene & Tropical Medicine, Keppel Street, London, WC1E 7HT UK
| | - Jason Moore
- grid.414543.30000 0000 9144 642XVector Control Product Testing Unit, Environmental Health and Ecological Science, Ifakara Health Institute, P.O. Box 74, Bagamoyo, Tanzania ,grid.416786.a0000 0004 0587 0574Swiss Tropical and Public Health Institute, Kreuzstrasse 2, 4123 Allschwil, Switzerland
| | - Selemani Mmbaga
- grid.414543.30000 0000 9144 642XVector Control Product Testing Unit, Environmental Health and Ecological Science, Ifakara Health Institute, P.O. Box 74, Bagamoyo, Tanzania
| | - Emile Tchicaya
- grid.462846.a0000 0001 0697 1172Swiss Centre for Scientific Research in Côte d’Ivoire, 1303 Abidjan, Côte d’Ivoire ,Vegro Aps, Copenhagen, Denmark Refshalevej 213A,
| | - Constant Edi
- grid.462846.a0000 0001 0697 1172Swiss Centre for Scientific Research in Côte d’Ivoire, 1303 Abidjan, Côte d’Ivoire
| | - Vani Chalageri
- grid.419641.f0000 0000 9285 6594Field Unit, ICMR-National Institute of Malaria Research, Bangalore, Karnataka India
| | - Sreehari Uragayala
- grid.419641.f0000 0000 9285 6594Field Unit, ICMR-National Institute of Malaria Research, Bangalore, Karnataka India
| | - Amit Sharma
- grid.419641.f0000 0000 9285 6594ICMR-National Institute of Malaria Research, Sector-8, Dwarka, New Delhi, 110077 India
| | - Manju Rahi
- grid.19096.370000 0004 1767 225XICMR-Indian Council of Medical Research, Ansari Nagar, New Delhi, India
| | - Kamaraju Raghavendra
- grid.419641.f0000 0000 9285 6594ICMR-National Institute of Malaria Research, Sector-8, Dwarka, New Delhi, 110077 India
| | - Alex Eapen
- grid.19096.370000 0004 1767 225XField Unit, ICMR-Indian Council of Medical Research, Chennai, India
| | | | - Amanda Ross
- grid.416786.a0000 0004 0587 0574Swiss Tropical and Public Health Institute, Kreuzstrasse 2, 4123 Allschwil, Switzerland ,grid.6612.30000 0004 1937 0642University of Basel, St. Petersplatz 1, 4002 Basel, Switzerland
| | - Sarah J. Moore
- grid.414543.30000 0000 9144 642XVector Control Product Testing Unit, Environmental Health and Ecological Science, Ifakara Health Institute, P.O. Box 74, Bagamoyo, Tanzania ,grid.416786.a0000 0004 0587 0574Swiss Tropical and Public Health Institute, Kreuzstrasse 2, 4123 Allschwil, Switzerland ,grid.6612.30000 0004 1937 0642University of Basel, St. Petersplatz 1, 4002 Basel, Switzerland
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Lees RS, Fornadel C, Snetselaar J, Wagman J, Spiers A. Insecticides for Mosquito Control: Improving and Validating Methods to Strengthen the Evidence Base. INSECTS 2023; 14:116. [PMID: 36835685 PMCID: PMC9961412 DOI: 10.3390/insects14020116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Accepted: 01/10/2023] [Indexed: 06/18/2023]
Abstract
Efforts to eliminate vector-borne diseases, for example malaria which caused an estimated 619,000 deaths in 2021 [...].
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Affiliation(s)
- Rosemary Susan Lees
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
- Innovation to Impact, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
| | - Christen Fornadel
- Innovative Vector Control Consortium (IVCC), Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK
| | - Janneke Snetselaar
- Innovative Vector Control Consortium (IVCC), Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK
| | - Joe Wagman
- PATH, 455 Massachusetts Ave NW, Washington, DC 20001, USA
| | - Angus Spiers
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
- Innovation to Impact, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
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11
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Mugenzi LMJ, Akosah-Brempong G, Tchouakui M, Menze BD, Tekoh TA, Tchoupo M, Nkemngo FN, Wondji MJ, Nwaefuna EK, Osae M, Wondji CS. Escalating pyrethroid resistance in two major malaria vectors Anopheles funestus and Anopheles gambiae (s.l.) in Atatam, Southern Ghana. BMC Infect Dis 2022; 22:799. [PMID: 36284278 PMCID: PMC9597992 DOI: 10.1186/s12879-022-07795-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 09/15/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Aggravation of insecticide resistance in malaria vectors is threatening the efforts to control malaria by reducing the efficacy of insecticide-based interventions hence needs to be closely monitored. This study investigated the intensity of insecticide resistance of two major malaria vectors An. funestus sensu stricto (s.s.) and An. gambiae sensu lato (s.l.) collected in southern Ghana and assessed the bio-efficacy of several long-lasting insecticidal nets (LLINs) against these mosquito populations. METHODS The insecticide susceptibility profiles of Anopheles funestus s.s. and Anopheles gambiae s.l. populations from Obuasi region (Atatam), southern Ghana were characterized and the bio-efficacy of some LLINs was assessed to determine the impact of insecticide resistance on the effectiveness of these tools. Furthermore, molecular markers associated with insecticide resistance in both species were characterized in the F0 and F1 populations using PCR and qPCR methods. RESULTS Anopheles funestus s.s. was the predominant species and was resistant to pyrethroids, organochlorine and carbamate insecticides, but fully susceptible to organophosphates. An. gambiae s.l. was resistant to all four insecticide classes. High intensity of resistance to 5 × and 10 × the discriminating concentration (DC) of pyrethroids was observed in both species inducing a considerable loss of efficacy of long-lasting insecticidal nets (LLINs). Temporal expression analysis revealed a massive 12-fold increase in expression of the CYP6P4a cytochrome P450 gene in An. funestus s.s., initially from a fold change of 41 (2014) to 500 (2021). For both species, the expression of candidate genes did not vary according to discriminating doses. An. gambiae s.l. exhibited high frequencies of target-site resistance including Vgsc-1014F (90%) and Ace-1 (50%) while these mutations were absent in An. funestus s.s. CONCLUSIONS The multiple and high intensity of resistance observed in both malaria vectors highlights the need to implement resistance management strategies and the introduction of new insecticide chemistries.
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Affiliation(s)
- Leon M J Mugenzi
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon.
| | - Gabriel Akosah-Brempong
- African Regional Postgraduate Program in Insect Science, University of Ghana, Legon, Accra, Ghana
- Biotechnology and Nuclear Agriculture Research Institute, Ghana Atomic Energy Commission, Accra, Ghana
| | - Magellan Tchouakui
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon
| | - Benjamin D Menze
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon
| | - Theofelix A Tekoh
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon
| | - Micareme Tchoupo
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon
| | - Francis N Nkemngo
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon
| | - Murielle J Wondji
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Ekene K Nwaefuna
- Biotechnology and Nuclear Agriculture Research Institute, Ghana Atomic Energy Commission, Accra, Ghana
| | - Michael Osae
- Biotechnology and Nuclear Agriculture Research Institute, Ghana Atomic Energy Commission, Accra, Ghana
| | - Charles S Wondji
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon.
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.
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12
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Modified World Health Organization (WHO) Tunnel Test for Higher Throughput Evaluation of Insecticide-Treated Nets (ITNs) Considering the Effect of Alternative Hosts, Exposure Time, and Mosquito Density. INSECTS 2022; 13:insects13070562. [PMID: 35886738 PMCID: PMC9323354 DOI: 10.3390/insects13070562] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/24/2022] [Revised: 06/08/2022] [Accepted: 06/14/2022] [Indexed: 01/27/2023]
Abstract
The standard World Health Organization (WHO) tunnel test is a reliable laboratory bioassay used for “free-flying” testing of insecticide-treated nets (ITNs) bio-efficacy where mosquitoes pass through a ITN sample to reach a live animal bait. Multiple parameters (i.e., bait, exposure time, and mosquito density) may affect the outcomes measured in tunnel tests. Therefore, a comparison was conducted of alternative hosts, exposure time, and lower mosquito density against the current gold standard test (100 mosquitoes, animal bait, and 12-h exposure) as outlined in the WHO ITN evaluation guideline. This was done with the aim to make the tunnel test cheaper and with higher throughput to meet the large sample sizes needed for bio-efficacy durability monitoring of chlorfenapyr ITNs that must be evaluated in “free-flying” bioassays. Methods: A series of experiments were conducted in the WHO tunnel test to evaluate the impact of the following factors on bio-efficacy endpoints of mosquito mortality at 24-h (M24) and 72-h (M72) and blood-feeding success (BFS): (1) baits (rabbit, membrane, human arm); (2) exposure time in the tunnel (1 h vs. 12 h); and (3) mosquito density (50 vs. 100). Finally, an alternative bioassay using a membrane with 50 mosquitoes (membrane-50) was compared to the gold standard bioassay (rabbit with 100 mosquitoes, rabbit-100). Pyrethroid-resistant Anopheles arabiensis and pyrethroid susceptible Anopheles gambiae were used to evaluate Interceptor® and Interceptor® G2 ITNs. Results: Using a human arm as bait gave a very different BFS, which impacted measurements of M24 and M72. The same trends in M24, M72 and BFS were observed for both Interceptor® ITN and Interceptor® G2 unwashed and washed 20 times measured using the gold standard WHO tunnel test (rabbit-100) or rabbit with 50 mosquitoes (rabbit-50). M24, M72 and BFS were not statistically different when either 50 or 100 mosquitoes were used with rabbit bait in the tunnel bioassay for either the susceptible or resistant strains. No systematic difference was observed between rabbit-50 and rabbit-100 in the agreement by the Bland and Altman method (B&A). The mean difference was 4.54% (−22.54–31.62) in BFS and 1.71% (−28.71–32.12) in M72 for rabbit-50 versus rabbit-100. Similar M24, M72 and lower BFS was measured by membrane-50 compared to rabbit-100. No systematic difference was observed in the agreement between membrane-50 and rabbit-100, by B&A. The mean difference was 9.06% (−11.42–29.64) for BSF and −5.44% (−50.3–39.45) for M72. Both membrane-50, rabbit-50 and rabbit-100 predicted the superiority of Interceptor® G2 over Interceptor® ITN for the resistant strain on M72. Conclusion: These results demonstrate that WHO tunnel tests using rabbit bait may be run with 50 mosquitoes to increase sample sizes needed for bio-efficacy durability monitoring of ITNs in “free-flying” bioassays. Using a membrane feeder with 50 mosquitoes is a potential replacement for the WHO tunnel bioassay with animal bait if control blood feeding rates can be improved to 50% because blood feeding impacts mosquito survival after exposure to insecticides.
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Lees RS, Armistead JS, Azizi S, Constant E, Fornadel C, Gimnig JE, Hemingway J, Impoinvil D, Irish SR, Kisinza W, Lissenden N, Mawejje HD, Messenger LA, Moore S, Ngufor C, Oxborough R, Protopopoff N, Ranson H, Small G, Wagman J, Weetman D, Zohdy S, Spiers A. Strain Characterisation for Measuring Bioefficacy of ITNs Treated with Two Active Ingredients (Dual-AI ITNs): Developing a Robust Protocol by Building Consensus. INSECTS 2022; 13:434. [PMID: 35621770 PMCID: PMC9144861 DOI: 10.3390/insects13050434] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 04/21/2022] [Accepted: 04/22/2022] [Indexed: 02/04/2023]
Abstract
Durability monitoring of insecticide-treated nets (ITNs) containing a pyrethroid in combination with a second active ingredient (AI) must be adapted so that the insecticidal bioefficacy of each AI can be monitored independently. An effective way to do this is to measure rapid knock down of a pyrethroid-susceptible strain of mosquitoes to assess the bioefficacy of the pyrethroid component and to use a pyrethroid-resistant strain to measure the bioefficacy of the second ingredient. To allow robust comparison of results across tests within and between test facilities, and over time, protocols for bioefficacy testing must include either characterisation of the resistant strain, standardisation of the mosquitoes used for bioassays, or a combination of the two. Through a series of virtual meetings, key stakeholders and practitioners explored different approaches to achieving these goals. Via an iterative process we decided on the preferred approach and produced a protocol consisting of characterising mosquitoes used for bioefficacy testing before and after a round of bioassays, for example at each time point in a durability monitoring study. We present the final protocol and justify our approach to establishing a standard methodology for durability monitoring of ITNs containing pyrethroid and a second AI.
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Affiliation(s)
- Rosemary S. Lees
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK; (J.H.); (N.L.); (H.R.); (D.W.)
- Innovation to Impact, Pembroke Place, Liverpool L3 5QA, UK;
| | - Jennifer S. Armistead
- U.S. President’s Malaria Initiative (PMI), U.S. Agency for International Development (USAID), Washington, DC 20547, USA;
| | - Salum Azizi
- KCMUCo-PAMVERC Test Facility, Department of Medical Parasitology and Entomology, Kilimanjaro Christian Medical University College, Moshi P.O. Box 2240, Tanzania;
| | - Edi Constant
- Centre Suisse de Recherches Scientifiques (CSRS), Abidjan 1303, Côte d’Ivoire;
| | - Christen Fornadel
- Innovative Vector Control Consortium (IVCC), Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK; (C.F.); (G.S.)
| | - John E. Gimnig
- Division of Parasitic Diseases and Malaria, Centers for Disease Control (CDC) and Prevention, Atlanta, GA 30329, USA; (J.E.G.); (D.I.); (S.Z.)
| | - Janet Hemingway
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK; (J.H.); (N.L.); (H.R.); (D.W.)
| | - Daniel Impoinvil
- Division of Parasitic Diseases and Malaria, Centers for Disease Control (CDC) and Prevention, Atlanta, GA 30329, USA; (J.E.G.); (D.I.); (S.Z.)
- U.S. President’s Malaria Initiative (PMI), Centers for Disease Control (CDC) and Prevention, Atlanta, GA 30329, USA;
| | - Seth R. Irish
- U.S. President’s Malaria Initiative (PMI), Centers for Disease Control (CDC) and Prevention, Atlanta, GA 30329, USA;
| | - William Kisinza
- Amani Research Centre, National Institute for Medical Research, Muheza P.O. Box 81, Tanzania;
| | - Natalie Lissenden
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK; (J.H.); (N.L.); (H.R.); (D.W.)
- Innovation to Impact, Pembroke Place, Liverpool L3 5QA, UK;
| | - Henry D. Mawejje
- Infectious Diseases Research Collaboration (IDRC), Plot 2C Nakasero Hill Road, Kampala P.O. Box 7475, Uganda;
| | - Louisa A. Messenger
- Department of Disease Control, Faculty of Infectious Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK; (L.A.M.); (C.N.); (N.P.)
| | - Sarah Moore
- Vector Control Product Testing Unit (VCPTU), Environmental Health and Ecological Science Department, Ifakara Health Institute, Bagamoyo P.O. Box 74, Tanzania;
- Vector Biology Unit, Department of Epidemiology and Public Health, Swiss Tropical & Public Health Institute, Kreuzstrasse 2, Allschwil, 4123 Basel, Switzerland
- Faculty of Science, University of Basel, Petersplatz 1, 4001 Basel, Switzerland
- Nelson Mandela African Institute of Science and Technology (NM-AIST), Tengeru P.O. Box 447, Tanzania
| | - Corine Ngufor
- Department of Disease Control, Faculty of Infectious Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK; (L.A.M.); (C.N.); (N.P.)
- Centre de Recherche Entomologique de Cotonou, Cotonou BP 2604, Benin
| | - Richard Oxborough
- PMI VectorLink Project, Abt Associates, 6130 Executive Blvd., Rockville, MD 20852, USA;
| | - Natacha Protopopoff
- Department of Disease Control, Faculty of Infectious Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK; (L.A.M.); (C.N.); (N.P.)
| | - Hilary Ranson
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK; (J.H.); (N.L.); (H.R.); (D.W.)
| | - Graham Small
- Innovative Vector Control Consortium (IVCC), Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK; (C.F.); (G.S.)
| | - Joseph Wagman
- Malaria and Neglected Tropical Diseases Program, PATH, Washington, DC 20001, USA;
| | - David Weetman
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK; (J.H.); (N.L.); (H.R.); (D.W.)
| | - Sarah Zohdy
- Division of Parasitic Diseases and Malaria, Centers for Disease Control (CDC) and Prevention, Atlanta, GA 30329, USA; (J.E.G.); (D.I.); (S.Z.)
- U.S. President’s Malaria Initiative (PMI), Centers for Disease Control (CDC) and Prevention, Atlanta, GA 30329, USA;
| | - Angus Spiers
- Innovation to Impact, Pembroke Place, Liverpool L3 5QA, UK;
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Kibondo UA, Odufuwa OG, Ngonyani SH, Mpelepele AB, Matanilla I, Ngonyani H, Makungwa NO, Mseka AP, Swai K, Ntabaliba W, Stutz S, Austin JW, Moore SJ. Influence of testing modality on bioefficacy for the evaluation of Interceptor ® G2 mosquito nets to combat malaria mosquitoes in Tanzania. Parasit Vectors 2022; 15:124. [PMID: 35410250 PMCID: PMC8996609 DOI: 10.1186/s13071-022-05207-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Accepted: 02/15/2022] [Indexed: 12/02/2022] Open
Abstract
Background Insecticide-treated net (ITN) durability is evaluated using longitudinal bioefficacy and fabric integrity sampling post-distribution. Interceptor® G2 was developed for resistance management and contains two adulticides: alpha-cypermethrin and chlorfenapyr; it is a pro-insecticide that is metabolized into its active form by mosquito-detoxifying enzymes and may be enhanced when the mosquito is physiologically active. To elucidate the impact of bioassay modality, mosquito exposures of the alphacypermethrin ITN Interceptor® and dual adulticide Interceptor® G2 were investigated. Methods This study evaluated the performance of Interceptor® G2 compared to Interceptor® against local strains of mosquitoes in Tanzania. Unwashed and 20× times washed nets were tested. Efficacy of ITNs was measured by four bioassay types: (1) World Health Organisation (WHO) cone test (cone), (2) WHO tunnel test (tunnel), (3) Ifakara ambient chamber test (I-ACT) and (4) the WHO gold standard experimental hut test (hut). Hut tests were conducted against free-flying wild pyrethroid metabolically resistant Anopheles arabiensis and Culex quinquefasciatus. Cone, tunnel and I-ACT bioassays used laboratory-reared metabolically resistant An. arabiensis and Cx. quinquefasciatus and pyrethroid susceptible Anopheles gambiae sensu stricto and Aedes aegypti. Results Against resistant strains, superiority of Interceptor® G2 over Interceptor® was observed in all “free-flying bioassays”. In cone tests (which restrict mosquito flight), superiority of Interceptor® over Interceptor® G2 was recorded. Mortality of unwashed Interceptor® G2 among An. arabiensis was lowest in hut tests at 42.9% (95% CI: 37.3–48.5), although this increased to 66.7% (95% CI: 47.1–86.3) by blocking hut exit traps so mosquitoes presumably increased frequencies of contact with ITNs. Higher odds of mortality were consistently observed in Interceptor® G2 compared to Interceptor® in “free-flying” bioassays using An. arabiensis: tunnel (OR = 1.42 [95% CI:1.19–1.70], p < 0.001), I-ACT (OR = 1.61 [95% CI: 1.05–2.49], p = 0.031) and hut (OR = 2.53 [95% CI: 1.96–3.26], p < 0.001). Interceptor® and Interceptor® G2 showed high blood-feeding inhibition against all strains. Conclusion Both free-flying laboratory bioassays (WHO Tunnel and I-ACT) consistently measured similarly, and both predicted the results of the experimental hut test. For bioefficacy monitoring and upstream product evaluation of ITNs in situ, the I-ACT may provide an alternative bioassay modality with improved statistical power. Interceptor G2® outperformed Interceptor ® against pyrethroid-resistant strains, demonstrating the usefulness of chlorfenapyr in mitigation of malaria. Graphical Abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1186/s13071-022-05207-9.
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Affiliation(s)
- Ummi Abdul Kibondo
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania.
| | - Olukayode G Odufuwa
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania.,Vector Biology Unit, Department of Epidemiology and Public Health, Swiss Tropical & Public Health Institute, Kreuzstrasse 2, 4123, Allschwil, Switzerland.,MRC International Statistics and Epidemiology Group, London School of Hygiene and Tropical Medicine, London, England
| | - Saphina H Ngonyani
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Ahmadi B Mpelepele
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Issaya Matanilla
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Hassan Ngonyani
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Noel O Makungwa
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Antony P Mseka
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Kyeba Swai
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania.,Vector Biology Unit, Department of Epidemiology and Public Health, Swiss Tropical & Public Health Institute, Kreuzstrasse 2, 4123, Allschwil, Switzerland
| | - Watson Ntabaliba
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
| | - Susanne Stutz
- Professional & Specialty Solutions, BASF SE, Public Health, 67117, Limburgerhof, Germany
| | - James W Austin
- Professional & Specialty Solutions, BASF Corporation, Public Health Global Development, Research Triangle Park, NC, 27709, USA
| | - Sarah Jane Moore
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania.,Vector Biology Unit, Department of Epidemiology and Public Health, Swiss Tropical & Public Health Institute, Kreuzstrasse 2, 4123, Allschwil, Switzerland.,University of Basel, Petersplatz 1, 4001, Basel, Switzerland.,Nelson Mandela African Institute of Science and Technology (NM-AIST), P.O. Box 447, Tengeru, Tanzania
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