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Govella NJ, Assenga A, Mlwale AT, Mirzai N, Heffernan E, Moriarty J, Wenger J, Corbel V, McBeath J, Ogoma SB, Killeen GF. Entomological assessment of hessian fabric transfluthrin vapour emanators for protecting against outdoor-biting Aedes aegypti in coastal Tanzania. PLoS One 2024; 19:e0299722. [PMID: 38809841 PMCID: PMC11135681 DOI: 10.1371/journal.pone.0299722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 02/13/2024] [Indexed: 05/31/2024] Open
Abstract
BACKGROUND A low technology emanator device for slowly releasing vapour of the volatile pyrethroid transfluthrin was recently developed in Tanzania that provides robust protection against night biting Anopheles and Culex vectors of malaria and filariasis for several months. Here these same emanator devices were assessed in Dar es Salaam city, as a means of protection against outdoor-biting Aedes (Stegomia) aegypti, the most important vector of human arboviruses worldwide, in parallel with similar studies in Haiti and Brazil. METHODS A series of entomological experiments were conducted under field and semi-field conditions, to evaluate whether transfluthrin emanators protect against wild Ae. aegypti, and also compare the transfluthrin responsiveness of Ae. aegypti originating from wild-caught eggs to established pyrethroid-susceptible Ae. aegypti and Anopheles gambiae colonies. Preliminary measurements of transfluthrin vapour concentration in air samples collected near treated emanators were conducted by gas chromatography-mass spectrometry. RESULTS Two full field experiments with four different emanator designs and three different transfluthrin formulations consistently indicated negligible reduction of human landing rates by wild Ae. aegypti. Under semi-field conditions in large cages, 50 to 60% reductions of landing rates were observed, regardless of which transfluthrin dose, capture method, emanator placement position, or source of mosquitoes (mildly pyrethroid resistant wild caught Ae. aegypti or pyrethroid-susceptible colonies of Ae. aegypti and An. gambiae) was used. Air samples collected immediately downwind from an emanator treated with the highest transfluthrin dose (15g), contained 12 to 19 μg/m3 transfluthrin vapour. CONCLUSIONS It appears unlikely that the moderate levels of pyrethroid resistance observed in wild Ae. aegypti can explain the modest-to-undetectable levels of protection exhibited. While potential inhalation exposure could be of concern for the highest (15g) dose evaluated, 3g of transfluthrin appears sufficient to achieve the modest levels of protection that were demonstrated entomologically. While the generally low levels of protection against Aedes reported here from Tanzania, and from similar entomological studies in Haiti and Brazil, are discouraging, complementary social science studies in Haiti and Brazil suggest end-users perceive valuable levels of protection against mosquitoes. It therefore remains unclear whether transfluthrin emanators have potential for protecting against Aedes vectors of important human arboviruses.
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Affiliation(s)
- Nicodem J. Govella
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Dar es Salaam, United Republic of Tanzania
- African Institution of Science and Technology, School of Life Science and Bio-Engineering, The Nelson Mandela, Tengeru, Arusha, United Republic of Tanzania
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
| | - Alphonce Assenga
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Dar es Salaam, United Republic of Tanzania
| | - Amos T. Mlwale
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Dar es Salaam, United Republic of Tanzania
| | - Nosrat Mirzai
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
| | - Eimear Heffernan
- Centre for Research into Atmospheric Chemistry, School of Chemistry, University College Cork, Cork, Republic of Ireland
- Environmental Research Institute, University College Cork, Cork, Republic of Ireland
| | - Jennie Moriarty
- Centre for Research into Atmospheric Chemistry, School of Chemistry, University College Cork, Cork, Republic of Ireland
- Environmental Research Institute, University College Cork, Cork, Republic of Ireland
| | - John Wenger
- Centre for Research into Atmospheric Chemistry, School of Chemistry, University College Cork, Cork, Republic of Ireland
- Environmental Research Institute, University College Cork, Cork, Republic of Ireland
| | - Vincent Corbel
- Institut de Recherche pour le Developpement, University of Montpellier, Montpellier, France
- Laboratório de Fisiologia e Controle de Artrópodes Vetores (Laficave), Instituto Oswaldo Cruz (IOC), Fundação Oswaldo Cruz (FIOCRUZ), Avenida Brasil, Rio de Janeiro-RJ, Brazil
| | - Justin McBeath
- Envu UK Ltd, Cambridge, Milton, Cambridge, United Kingdom
| | | | - Gerry F. Killeen
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Dar es Salaam, United Republic of Tanzania
- Environmental Research Institute, University College Cork, Cork, Republic of Ireland
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
- School of Biological Earth & Environmental Sciences, Environmental Research Institute, University College Cork, Cork, Republic of Ireland
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Yan C, Hii J, Ngoen-Klan R, Ahebwa A, Saeung M, Chareonviriyaphap T. The effect of transfluthrin-treated jute and cotton emanator vests on human landing and fecundity of Anopheles minimus in Thailand. Acta Trop 2023; 242:106904. [PMID: 36967063 DOI: 10.1016/j.actatropica.2023.106904] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2022] [Revised: 03/17/2023] [Accepted: 03/18/2023] [Indexed: 04/03/2023]
Abstract
Complementary approaches to tackle outdoor and early evening biting mosquitoes are urgently required. Transfluthrin (TFT) is a volatile pyrethroid capable of altering mosquito feeding behavior. This study investigated the efficacy of TFT-treated jute (TFT-J) and cotton (TFT-C) fabrics on human landing activity, feeding and fecundity of Anopheles minimus in Thailand. Jute and cotton fabrics each measuring 1024 cm2 were impregnated with 7.34 × 10-4 g/cm2 TFT (20%, w/v), and evaluated in a semi-field screen house system. Two collectors, wearing an untreated control or TFT-treated vests, conducted human-landing collections of released 100 laboratory-reared adult females of An. minimus from 18:00-00:00 h for 16 consecutive nights. Recaptured mosquitoes were given a blood meal for 30 min. with a membrane feeding system for assessment of blood feeding and fecundity. TFT-J, relative to control, significantly reduced human landings (Odds Ratio (OR) =0.27 (95% Confidence Interval (CI) [0.10-0.74], p = 0.011)), however no significant reduction was observed for TFT-C (OR=0.67 [95% CI 0.24-1.82], p = 0.43). Blood feeding was significantly lower among mosquitoes exposed to TFT-J (12.45% [95% CI, 2.04-22.85], p = 0.029) and TFT-C (13% [95% CI, 0.99-26.84], p = 0.016) relative to control. Impregnated fabrics had no effect on the mean number of egg oviposition. However, egg hatchability was reduced in TFT-J (49.5% [95% CI, 21.74-77.26], p = 0.029) and TFT-C (40.2% [95% CI, 17.21-63.19], p = 0.008) relative to control. TFT-J significantly reduced the landing, blood feeding, and fertility of An. minimus. Further studies are needed to evaluate different treatment methods on fabrics and their incorporation in integrated mosquito management.
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Affiliation(s)
- Chanly Yan
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok 10900, Thailand
| | - Jeffrey Hii
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok 10900, Thailand; College of Public Health, Medical & Veterinary Sciences, James Cook University, North Queensland, QLD 4810, Australia
| | - Ratchadawan Ngoen-Klan
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok 10900, Thailand
| | - Alex Ahebwa
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok 10900, Thailand
| | - Manop Saeung
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok 10900, Thailand
| | - Theeraphap Chareonviriyaphap
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok 10900, Thailand; Royal Society of Thailand, Thailand.
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Achee NL, Perkins TA, Moore SM, Liu F, Sagara I, Van Hulle S, Ochomo EO, Gimnig JE, Tissera HA, Harvey SA, Monroe A, Morrison AC, Scott TW, Reiner RC, Grieco JP. Spatial repellents: The current roadmap to global recommendation of spatial repellents for public health use. CURRENT RESEARCH IN PARASITOLOGY & VECTOR-BORNE DISEASES 2022; 3:100107. [PMID: 36590345 PMCID: PMC9801085 DOI: 10.1016/j.crpvbd.2022.100107] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Revised: 11/18/2022] [Accepted: 12/04/2022] [Indexed: 12/13/2022]
Abstract
Spatial repellent (SR) products are envisioned to complement existing vector control methods through the continual release of volatile active ingredients (AI) providing: (i) protection against day-time and early-evening biting; (ii) protection in enclosed/semi-enclosed and peri-domestic spaces; (iii) various formulations to fit context-specific applications; and (iv) increased coverage over traditional control methods. SR product AIs also have demonstrated effect against insecticide-resistant vectors linked to malaria and Aedes-borne virus (ABV) transmission. Over the past two decades, key stakeholders, including World Health Organization (WHO) representatives, have met to discuss the role of SRs in reducing arthropod-borne diseases based on existing evidence. A key focus has been to establish a critical development path for SRs, including scientific, regulatory and social parameters that would constitute an outline for a SR target product profile, i.e. optimum product characteristics. The principal gap is the lack of epidemiological data demonstrating SR public health impact across a range of different ecological and epidemiological settings, to inform a WHO policy recommendation. Here we describe in brief trials that are designed to fulfill evidence needs for WHO assessment and initial projections of SR cost-effectiveness against malaria and dengue.
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Affiliation(s)
- Nicole L. Achee
- Department of Biological Sciences, Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, USA,Corresponding author. Department of Biological Sciences, Eck Institute for Global Health, 239 Galvin Life Science Center, Notre Dame, IN, 46556, USA.
| | - T. Alex Perkins
- Department of Biological Sciences, Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, USA
| | - Sean M. Moore
- Department of Biological Sciences, Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, USA
| | - Fang Liu
- Department of Applied and Computational Mathematics and Statistics, University of Notre Dame, Notre Dame, IN, USA
| | - Issaka Sagara
- Malaria Research and Training Center (MRTC), Faculty of Medicine, Dentistry and Pharmacy at the University of Sciences, Techniques and Technologies of Bamako (USTTB), Bamako, Mali
| | | | - Eric O. Ochomo
- Kenya Medical Research Institute, Centre for Global Health Research, Kisumu, Kenya
| | - John E. Gimnig
- Centers for Disease Control and Prevention, Division of Parasitic Diseases and Malaria, Atlanta, GA, USA
| | | | - Steven A. Harvey
- Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - April Monroe
- Johns Hopkins Center for Communication Programs, Baltimore, MD, USA
| | - Amy C. Morrison
- Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California, Davis, CA, USA
| | - Thomas W. Scott
- Department of Entomology and Nematology, University of California, Davis, CA, USA
| | - Robert C. Reiner
- Department of Health Metrics Sciences, University of Washington, Seattle, WA, USA
| | - John P. Grieco
- Department of Biological Sciences, Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, USA
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Transfluthrin eave-positioned targeted insecticide (EPTI) reduces human landing rate (HLR) of pyrethroid resistant and susceptible malaria vectors in a semi-field simulated peridomestic space. Malar J 2021; 20:357. [PMID: 34461911 PMCID: PMC8404287 DOI: 10.1186/s12936-021-03880-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 08/15/2021] [Indexed: 02/07/2023] Open
Abstract
Background Volatile pyrethroids (VPs) are proven to reduce human–vector contact for mosquito vectors. With increasing resistance to pyrethroids in mosquitoes, the efficacy of VPs, such as transfluthrin, may be compromised. Therefore, experiments were conducted to determine if the efficacy of transfluthrin eave-positioned targeted insecticide (EPTI) depends on the resistance status of malaria vectors. Methods Ribbons treated with 5.25 g transfluthrin or untreated controls were used around the eaves of an experimental hut as EPTI inside a semi-field system. Mosquito strains with different levels of pyrethroid resistance were released simultaneously, recaptured by means of human landing catches (HLCs) and monitored for 24-h mortality. Technical-grade (TG) transfluthrin was used, followed by emulsifiable concentrate (EC) transfluthrin and additional mosquito strains. Generalized linear mixed models with binomial distribution were used to determine the impact of transfluthrin and mosquito strain on mosquito landing rates and 24-h mortality. Results EPTI treated with 5.25 g of either TG or EC transfluthrin significantly reduced HLR of all susceptible and resistant Anopheles mosquitoes (Odds Ratio (OR) ranging from 0.14 (95% Confidence Interval (CI) [0.11–0.17], P < 0.001) to 0.57, (CI [0.42–0.78] P < 0.001). Both TG and EC EPTI had less impact on landing for the resistant Anopheles arabiensis (Mbita strain) compared to the susceptible Anopheles gambiae (Ifakara strain) (OR 1.50 [95% CI 1.18–1.91] P < 0.001) and (OR 1.67 [95% CI 1.29–2.17] P < 0.001), respectively. The EC EPTI also had less impact on the resistant An. arabiensis (Kingani strain) (OR 2.29 [95% CI 1.78–2.94] P < 0.001) compared to the control however the TG EPTI was equally effective against the resistant Kingani strain and susceptible Ifakara strain (OR 1.03 [95% CI 0.82–1.32] P = 0.75). Finally the EC EPTI was equally effective against the susceptible An. gambiae (Kisumu strain) and the resistant An. gambiae (Kisumu-kdr strain) (OR 0.98 [95% CI 0.74–1.30] P = 0.90). Conclusions Transfluthrin-treated EPTI could be useful in areas with pyrethroid-resistant mosquitoes, but it remains unclear whether stronger resistance to pyrethroids will undermine the efficacy of transfluthrin. At this dosage, transfluthrin EPTI cannot be used to kill exposed mosquitoes. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-021-03880-2.
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Devine GJ, Vazquez-Prokopec GM, Bibiano-Marín W, Pavia-Ruz N, Che-Mendoza A, Medina-Barreiro A, Villegas J, Gonzalez-Olvera G, Dunbar MW, Ong O, Ritchie SA, Churcher TS, Kirstein OD, Manrique-Saide P. The entomological impact of passive metofluthrin emanators against indoor Aedes aegypti: A randomized field trial. PLoS Negl Trop Dis 2021; 15:e0009036. [PMID: 33497375 PMCID: PMC7864418 DOI: 10.1371/journal.pntd.0009036] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 02/05/2021] [Accepted: 12/07/2020] [Indexed: 11/18/2022] Open
Abstract
Background In the absence of vaccines or drugs, insecticides are the mainstay of Aedes-borne disease control. Their utility is challenged by the slow deployment of resources, poor community compliance and inadequate household coverage. Novel application methods are required. Methodology and principal findings A 10% w/w metofluthrin “emanator” that passively disseminates insecticide from an impregnated net was evaluated in a randomized trial of 200 houses in Mexico. The devices were introduced at a rate of 1 per room and replaced at 3-week intervals. During each of 7 consecutive deployment cycles, indoor resting mosquitoes were sampled using aspirator collections. Assessments of mosquito landing behaviours were made in a subset of houses. Pre-treatment, there were no differences in Aedes aegypti indices between houses recruited to the control and treatment arms. Immediately after metofluthrin deployment, the entomological indices between the trial arms diverged. Averaged across the trial, there were significant reductions in Abundance Rate Ratios for total Ae. aegypti, female abundance and females that contained blood meals (2.5, 2.4 and 2.3-times fewer mosquitoes respectively; P<0.001). Average efficacy was 60.2% for total adults, 58.3% for females, and 57.2% for blood-fed females. The emanators also reduced mosquito landings by 90% from 12.5 to 1.2 per 10-minute sampling period (P<0.05). Homozygous forms of the pyrethroid resistant kdr alleles V410L, V1016L and F1534C were common in the target mosquito population; found in 39%, 24% and 95% of mosquitoes collected during the trial. Conclusions/Significance This is the first randomized control trial to evaluate the entomological impact of any volatile pyrethroid on urban Ae. aegypti. It demonstrates that volatile pyrethroids can have a sustained impact on Ae. aegypti population densities and human-vector contact indoors. These effects occur despite the presence of pyrethroid-resistant alleles in the target population. Formulations like these may have considerable utility for public health vector control responses. Insecticidal control tools are heavily relied on for the control of mosquito-borne viruses such as dengue, chikungunya and Zika, but the logistics associated with conventional insecticide use (e.g. space sprays and residual formulations) are challenging. Considerable time and resources are required to treat household interiors; an impediment exacerbated by the difficulty in gaining entrance to households, and sometimes by limited compliance in the community. Another constraint to effective insecticide use is that many mosquito populations are resistant to the chemicals used. Volatile pyrethroids, exhibiting both lethal and behavioural effects on mosquitoes are available in formulations that release insecticides passively to the air, at room temperature. These may be suitable for deployment in houses with the aim of creating “bite-free” spaces. By removing the need for conventional application methods, these devices might be rapidly deployed with minimum disruption to households. This is the first large-scale, randomized control trial to evaluate the entomological impacts of volatile pyrethroids in an urban environment. Using metofluthrin as an example, we confirm that some formulations have a significant impact on Aedes aegypti densities and landing behaviour indoors. These effects occur despite the presence of pyrethroid-resistance alleles associated with conventional insecticide resistance.
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Affiliation(s)
- Gregor J Devine
- Mosquito Control Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | | | - Wilbert Bibiano-Marín
- Unidad Colaborativa de Bioensayos Entomológicos, Campus de Ciencias. Biológicas y Agropecuarias, Universidad Autónoma de Yucatán, Mérida, Yucatán, México
| | - Norma Pavia-Ruz
- Centro de Investigaciones Regionales Hideyo Noguchi, Universidad Autónoma de Yucatán, Mérida, México
| | - Azael Che-Mendoza
- Unidad Colaborativa de Bioensayos Entomológicos, Campus de Ciencias. Biológicas y Agropecuarias, Universidad Autónoma de Yucatán, Mérida, Yucatán, México
| | - Anuar Medina-Barreiro
- Unidad Colaborativa de Bioensayos Entomológicos, Campus de Ciencias. Biológicas y Agropecuarias, Universidad Autónoma de Yucatán, Mérida, Yucatán, México
| | - Josue Villegas
- Unidad Colaborativa de Bioensayos Entomológicos, Campus de Ciencias. Biológicas y Agropecuarias, Universidad Autónoma de Yucatán, Mérida, Yucatán, México
| | - Gabriela Gonzalez-Olvera
- Unidad Colaborativa de Bioensayos Entomológicos, Campus de Ciencias. Biológicas y Agropecuarias, Universidad Autónoma de Yucatán, Mérida, Yucatán, México
| | - Mike W Dunbar
- Department of Environmental Sciences, Emory University, Atlanta, Georgia, United States of America
| | - Oselyne Ong
- Mosquito Control Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | - Scott A Ritchie
- College of Public Health, Medical and Veterinary Sciences, James Cook University, Queensland, Cairns, Australia
| | - Thomas S Churcher
- Department of Infectious Disease Epidemiology, MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, United Kingdom
| | - Oscar D Kirstein
- Department of Environmental Sciences, Emory University, Atlanta, Georgia, United States of America
| | - Pablo Manrique-Saide
- Unidad Colaborativa de Bioensayos Entomológicos, Campus de Ciencias. Biológicas y Agropecuarias, Universidad Autónoma de Yucatán, Mérida, Yucatán, México
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Denz A, Njoroge MM, Tambwe MM, Champagne C, Okumu F, van Loon JJA, Hiscox A, Saddler A, Fillinger U, Moore SJ, Chitnis N. Predicting the impact of outdoor vector control interventions on malaria transmission intensity from semi-field studies. Parasit Vectors 2021; 14:64. [PMID: 33472661 PMCID: PMC7819244 DOI: 10.1186/s13071-020-04560-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Accepted: 12/21/2020] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Semi-field experiments with human landing catch (HLC) measure as the outcome are an important step in the development of novel vector control interventions against outdoor transmission of malaria since they provide good estimates of personal protection. However, it is often infeasible to determine whether the reduction in HLC counts is due to mosquito mortality or repellency, especially considering that spatial repellents based on volatile pyrethroids might induce both. Due to the vastly different impact of repellency and mortality on transmission, the community-level impact of spatial repellents can not be estimated from such semi-field experiments. METHODS We present a new stochastic model that is able to estimate for any product inhibiting outdoor biting, its repelling effect versus its killing and disarming (preventing host-seeking until the next night) effects, based only on time-stratified HLC data from controlled semi-field experiments. For parameter inference, a Bayesian hierarchical model is used to account for nightly variation of semi-field experimental conditions. We estimate the impact of the products on the vectorial capacity of the given Anopheles species using an existing mathematical model. With this methodology, we analysed data from recent semi-field studies in Kenya and Tanzania on the impact of transfluthrin-treated eave ribbons, the odour-baited Suna trap and their combination (push-pull system) on HLC of Anopheles arabiensis in the peridomestic area. RESULTS Complementing previous analyses of personal protection, we found that the transfluthrin-treated eave ribbons act mainly by killing or disarming mosquitoes. Depending on the actual ratio of disarming versus killing, the vectorial capacity of An. arabiensis is reduced by 41 to 96% at 70% coverage with the transfluthrin-treated eave ribbons and by 38 to 82% at the same coverage with the push-pull system, under the assumption of a similar impact on biting indoors compared to outdoors. CONCLUSIONS The results of this analysis of semi-field data suggest that transfluthrin-treated eave ribbons are a promising tool against malaria transmission by An. arabiensis in the peridomestic area, since they provide both personal and community protection. Our modelling framework can estimate the community-level impact of any tool intervening during the mosquito host-seeking state using data from only semi-field experiments with time-stratified HLC.
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Affiliation(s)
- Adrian Denz
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland.
- University of Basel, Petersplatz 1, Basel, Switzerland.
| | - Margaret M Njoroge
- Human Health Theme, International Centre of Insect Physiology and Ecology (icipe), 00100, Nairobi, Kenya
- Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands
| | - Mgeni M Tambwe
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Clara Champagne
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland
- University of Basel, Petersplatz 1, Basel, Switzerland
| | - Fredros Okumu
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
- School of Public Health, Faculty of Health Science, University of the Witwatersrand, Johannesburg, South Africa
- School of Life Science and Biotechnology, Nelson Mandela African Institution of Science and Technology, P.O. Box 447, Arusha, Tanzania
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK
| | - Joop J A van Loon
- Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands
| | - Alexandra Hiscox
- Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands
- ARCTEC, London School of Hygiene and Tropical Medicine, Keppel Street, WC1E 7HT, London, UK
| | - Adam Saddler
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland
- University of Basel, Petersplatz 1, Basel, Switzerland
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Ulrike Fillinger
- Human Health Theme, International Centre of Insect Physiology and Ecology (icipe), 00100, Nairobi, Kenya
| | - Sarah J Moore
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland
- University of Basel, Petersplatz 1, Basel, Switzerland
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Nakul Chitnis
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland
- University of Basel, Petersplatz 1, Basel, Switzerland
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7
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ten Bosch QA, Wagman JM, Castro-Llanos F, Achee NL, Grieco JP, Perkins TA. Community-level impacts of spatial repellents for control of diseases vectored by Aedes aegypti mosquitoes. PLoS Comput Biol 2020; 16:e1008190. [PMID: 32976489 PMCID: PMC7541056 DOI: 10.1371/journal.pcbi.1008190] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2019] [Revised: 10/07/2020] [Accepted: 07/24/2020] [Indexed: 11/22/2022] Open
Abstract
Spatial repellents (SRs) reduce human-mosquito contact by preventing mosquito entrance into human-occupied spaces and interfering with host-seeking and blood-feeding. A new model to synthesize experimental data on the effects of transfluthrin on Aedes aegypti explores how SR effects interact to impact the epidemiology of diseases vectored by these mosquitoes. Our results indicate that the greatest impact on force of infection is expected to derive from the chemical’s lethal effect but delayed biting and the negative effect this may have on the mosquito population could elicit substantial impact in the absence of lethality. The relative contributions of these effects depend on coverage, chemical dose, and housing density. We also demonstrate that, through an increase in the number of potentially infectious mosquito bites, increased partial blood-feeding and reduced exiting may elicit adverse impacts, which could offset gains achieved by other effects. Our analysis demonstrates how small-scale experimental data can be leveraged to derive expectations of epidemiological impact of SRs deployed at larger scales. Mosquito control strategies that reduce bites to humans through multiple, non-lethal modes of action may be important in controlling mosquito-borne diseases where insecticidal strategies are ineffective. Assessing how effective such tools are in reducing infections is not clear-cut due to the multiple ways these products affect mosquitoes’ behavior and life cycle. We introduce a paired experimental and mathematical framework to analyze and combine data from experiments on the several effects of a transfluthrin formulation and assess its public health impact. We show that, while product-induced lethality accounts for the majority of the product’s impact, delayed blood feeding can, through its negative impact on mosquito population sizes, elicit its own substantial impact. Adverse effects of increased partial blood-feeding and reduced exiting could offset gains achieved by other effects such delayed blood feeding and lethality. Our model offers a way of synthesizing the results of feasible experiments at small scales to assess public health impact at large scales.
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Affiliation(s)
- Quirine A. ten Bosch
- Department of Biological Sciences and Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana, United States of America
- * E-mail: (QAtB); (TAP)
| | - Joseph M. Wagman
- Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America
| | | | - Nicole L. Achee
- Department of Biological Sciences and Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - John P. Grieco
- Department of Biological Sciences and Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - T. Alex Perkins
- Department of Biological Sciences and Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana, United States of America
- * E-mail: (QAtB); (TAP)
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Martin NJ, Nam VS, Lover AA, Phong TV, Tu TC, Mendenhall IH. The impact of transfluthrin on the spatial repellency of the primary malaria mosquito vectors in Vietnam: Anopheles dirus and Anopheles minimus. Malar J 2020; 19:9. [PMID: 31906969 PMCID: PMC6945573 DOI: 10.1186/s12936-019-3092-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Accepted: 12/25/2019] [Indexed: 11/28/2022] Open
Abstract
Background The complexity of mosquito-borne diseases poses a major challenge to global health efforts to mitigate their impact on people residing in sub-tropical and tropical regions, to travellers and deployed military personnel. To supplement drug- and vaccine-based disease control programmes, other strategies are urgently needed, including the direct control of disease vectors. Modern vector control research generally focuses on identifying novel active ingredients and/or innovative methods to reduce human-mosquito interactions. These efforts include the evaluation of spatial repellents, which are compounds capable of altering mosquito feeding behaviour without direct contact with the chemical source. Methods This project examined the impact of airborne transfluthrin from impregnated textile materials on two important malaria vectors, Anopheles dirus and Anopheles minimus. Repellency was measured by movement within taxis cages within a semi-field environment at the National Institute of Hygiene and Epidemiology in Hanoi, Vietnam. Knockdown and mortality were measured in adult mosquito bioassay cages. Metered-volume air samples were collected at a sub-set of points in the mosquito exposure trial. Results Significant differences in knockdown/mortality were observed along a gradient from the exposure source with higher rates of knockdown/mortality at 2 m and 4 m when compared with the furthest distance (16 m). Knockdown/mortality was also greater at floor level and 1.5 m when compared to 3 m above the floor. Repellency was not significantly different except when comparing 2 m and 16 m taxis cages. Importantly, the two species reacted differently to transfluthrin, with An. minimus being more susceptible to knockdown and mortality. The measured concentrations of airborne transfluthrin ranged from below the limit of detection to 1.32 ng/L, however there were a limited number of evaluable samples complicating interpretation of these results. Conclusions This study, measuring repellency, knockdown and mortality in two malaria vectors in Vietnam demonstrates that both species are sensitive to airborne transfluthrin. The differences in magnitude of response between the two species requires further study before use in large-scale vector control programmes to delineate how spatial repellency would impact the development of insecticide resistance and the disruption of biting behaviour.
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Affiliation(s)
| | - Vu S Nam
- National Institute of Hygiene and Entomology, Ministry of Health, Hanoi, Vietnam
| | - Andrew A Lover
- Department of Biostatistics and Epidemiology, School of Public Health and Health Sciences, University of Massachusetts, Amherst, MA, USA
| | - Tran V Phong
- National Institute of Hygiene and Entomology, Ministry of Health, Hanoi, Vietnam
| | - Tran C Tu
- National Institute of Hygiene and Entomology, Ministry of Health, Hanoi, Vietnam
| | - Ian H Mendenhall
- Duke-NUS Medical School, Programme in Emerging Infectious Diseases, 8 College Road, Singapore, 169857, Singapore.
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