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Mmbaga AT, Lwetoijera DW. Current and future opportunities of autodissemination of pyriproxyfen approach for malaria vector control in urban and rural Africa. Wellcome Open Res 2023; 8:119. [PMID: 37440995 PMCID: PMC10333782 DOI: 10.12688/wellcomeopenres.19131.2] [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] [Accepted: 10/23/2023] [Indexed: 07/15/2023] Open
Abstract
Despite the progress made in reducing malaria burden, new ways to address the increasing challenges of insecticide resistance and the invasion and spread of exotic malaria vectors such as Anopheles stephensi in Africa are urgently needed. While African countries are adopting larviciding as a complementary intervention for malaria vector control, the autodissemination technology has the potential to overcome barriers associated with the identification and treatment of prolific habitats that impede conventional larviciding approaches in rural settings. The autodissemination technology as a "lure and release" strategy works by exploiting the resting behavior of gravid mosquitoes to transfer lethal concentration of biological or chemical insecticide such as pyriproxyfen (PPF), an insect growth regulator (IGRs) to their oviposition sites and result in adult emergence inhibition. Despite the evidence of the autodissemination approach to control other mosquito-borne diseases, there is growing and promising evidence for its use in controlling malaria vectors in Africa, which highlights the momentous research that needs to be sustained. This article reviews the evidence for efficacy of the autodissemination approach using PPF and discusses its potential as efficient and affordable complementary malaria vector control intervention in Africa. In the previous studies that were done in controlled semi-field environments, autodissemination with PPF demonstrated its potential in reducing densities of captive population of malaria vectors such as Anopheles gambiae and Anopheles arabiensis. Of importance, empirical evidence and biology-informed mathematical models to demonstrate the utility of the autodissemination approach to control wild populations of malaria vectors under field environment either alone or in combination with other tools are underway. Among others, the key determining factors for future introduction of this approach at scale is having scalable autodissemination devices, optimized PPF formulations, assess its integration/complementarity to existing conventional larviciding, and community perception and acceptance of the autodissemination approach.
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Affiliation(s)
- Augustino Thabiti Mmbaga
- Environmental Health and Ecological Science Department, Ifakara Health Institute, Ifakara, Morogoro, P.O. Box 53, Tanzania
| | - Dickson Wilson Lwetoijera
- Environmental Health and Ecological Science Department, Ifakara Health Institute, Ifakara, Morogoro, P.O. Box 53, Tanzania
- School of Life Sciences and Bio Engineering, Nelson Mandela African Institution of Science and Technology, Tengeru, Arusha, P.O. Box 447, Tanzania
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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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Mmbaga AT, Lwetoijera DW. Current and future opportunities of autodissemination of pyriproxyfen approach for malaria vector control in urban and rural Africa. Wellcome Open Res 2023. [DOI: 10.12688/wellcomeopenres.19131.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/18/2023] Open
Abstract
Despite the progress made in reducing malaria burden, new ways to address the increasing challenges of insecticide resistance and the invasion and spread of exotic malaria vectors such as Anopheles stephensi in Africa are urgently needed. While African countries are adopting larviciding as a complementary intervention for malaria vector control, the autodissemination technology has the potential to overcome barriers associated with the identification and treatment of prolific habitats that impede conventional larviciding approaches in rural settings. The autodissemination technology as a “lure and release” strategy works by exploiting the resting behavior of gravid mosquitoes to transfer lethal concentration of biological or chemical insecticide such as pyriproxyfen (PPF), an insect growth regulator (IGRs) to their oviposition sites and result in adult emergence. Despite the evidence of the autodissemination approach to control other mosquito-borne diseases, there is growing and promising evidence for its use in controlling malaria vectors in Africa, which highlights the momentous research that needs to be sustained. This article reviews the evidence for efficacy of the autodissemination approach using PPF and discusses its potential as efficient and affordable complementary malaria vector control intervention in Africa. In the previous studies that were done in controlled semi-field environments, autodissemination with PPF demonstrated its potential in reducing densities of captive population of malaria vectors such as Anopheles gambiae and Anopheles arabiensis. Of importance, empirical evidence and biology-informed mathematical models to demonstrate the utility of the autodissemination approach to control wild populations of malaria vectors under field environment either alone or in combination with other tools are underway. Among others, the key determining factors for future introduction of this approach at scale is having scalable autodissemination devices, optimized PPF formulations, assess its integration/complementarity to existing conventional larviciding, and community perception and acceptance of the autodissemination approach.
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Song J, Zheng Z, Fang H, Li T, Wu Z, Qiu M, Shen H, Mei J, Xu L. Deposition and dissipation of difenoconazole in pepper and soil and its reduced application to control pepper anthracnose. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2023; 252:114591. [PMID: 36736234 DOI: 10.1016/j.ecoenv.2023.114591] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 01/27/2023] [Accepted: 01/28/2023] [Indexed: 06/18/2023]
Abstract
The initial deposition amount, dissipation dynamics, retention rate, and field control efficacy of difenoconazole in pepper-soil system were studied with different application dosages, planting regions and patterns. The initial deposition amount of difenoconazole under the same application dosage showed the following order: fruits < cultivated soils < lower stems < upper stems < lower leaves < upper leaves, open field < greenhouse, and Changjiang < Cixi < Hefei < Langfang, respectively, which increased with increasing application dosage. The dissipation rates in leaves, stems, fruits and cultivated soils exhibited an initially fast and then slow trend, while the retention rates displayed a tendency of first increasing and then stabilizing with increasing application dosages. After 7 d of difenoconazole application, the retention rates at five concentrations were 10.3%- 39.1%, and the field efficacy mostly reached the minimum effective dose. These results suggested that difenoconazole could be reduced by 25% based on the minimum recommended dose meeting the requirements of field control efficacy for controlling pepper anthracnose.
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Affiliation(s)
- Jiajin Song
- Institute of Pesticide and Environmental Toxicology, College of Agriculture & Biotechnology, Zhejiang University, Hangzhou 310058, China
| | - Zhiruo Zheng
- Institute of Pesticide and Environmental Toxicology, College of Agriculture & Biotechnology, Zhejiang University, Hangzhou 310058, China
| | - Hua Fang
- Institute of Pesticide and Environmental Toxicology, College of Agriculture & Biotechnology, Zhejiang University, Hangzhou 310058, China; Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Ministry of Agriculture, Zhejiang University, Hangzhou 310058, China; Key Laboratory of Biology of Crop Pathogens and Insects of Zhejiang Province, Zhejiang University, Hangzhou 310058, China
| | - Tongxin Li
- Institute of Pesticide and Environmental Toxicology, College of Agriculture & Biotechnology, Zhejiang University, Hangzhou 310058, China
| | - Zishan Wu
- Institute of Pesticide and Environmental Toxicology, College of Agriculture & Biotechnology, Zhejiang University, Hangzhou 310058, China
| | - Mengting Qiu
- Institute of Pesticide and Environmental Toxicology, College of Agriculture & Biotechnology, Zhejiang University, Hangzhou 310058, China
| | - Hongjian Shen
- Institute of Pesticide and Environmental Toxicology, College of Agriculture & Biotechnology, Zhejiang University, Hangzhou 310058, China
| | - Jiajia Mei
- Institute of Pesticide and Environmental Toxicology, College of Agriculture & Biotechnology, Zhejiang University, Hangzhou 310058, China
| | - Lihui Xu
- Institute of Eco-Environmental Protection, Shanghai Academy of Agricultural Sciences, Shanghai 201403, China.
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Comparative analysis of the larvicidal activity of temephos (EC50) and novaluaron (EC10) to control Anopheles stephensi in Sri Lanka. Parasitol Int 2023; 92:102686. [DOI: 10.1016/j.parint.2022.102686] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 07/06/2022] [Accepted: 09/22/2022] [Indexed: 11/22/2022]
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Njoroge MM, Fillinger U, Saddler A, Moore S, Takken W, van Loon JJA, Hiscox A. Evaluating putative repellent 'push' and attractive 'pull' components for manipulating the odour orientation of host-seeking malaria vectors in the peri-domestic space. Parasit Vectors 2021; 14:42. [PMID: 33430963 PMCID: PMC7802213 DOI: 10.1186/s13071-020-04556-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 12/16/2020] [Indexed: 12/17/2022] Open
Abstract
Background Novel malaria vector control approaches aim to combine tools for maximum protection. This study aimed to evaluate novel and re-evaluate existing putative repellent ‘push’ and attractive ‘pull’ components for manipulating the odour orientation of malaria vectors in the peri-domestic space. Methods Anopheles arabiensis outdoor human landing catches and trap comparisons were implemented in large semi-field systems to (i) test the efficacy of Citriodiol® or transfluthrin-treated fabric strips positioned in house eave gaps as push components for preventing bites; (ii) understand the efficacy of MB5-baited Suna-traps in attracting vectors in the presence of a human being; (iii) assess 2-butanone as a CO2 replacement for trapping; (iv) determine the protection provided by a full push-pull set up. The air concentrations of the chemical constituents of the push–pull set-up were quantified. Results Microencapsulated Citriodiol® eave strips did not provide outdoor protection against host-seeking An. arabiensis. Transfluthrin-treated strips reduced the odds of a mosquito landing on the human volunteer (OR 0.17; 95% CI 0.12–0.23). This impact was lower (OR 0.59; 95% CI 0.52–0.66) during the push-pull experiment, which was associated with low nighttime temperatures likely affecting the transfluthrin vaporisation. The MB5-baited Suna trap supplemented with CO2 attracted only a third of the released mosquitoes in the absence of a human being; however, with a human volunteer in the same system, the trap caught < 1% of all released mosquitoes. The volunteer consistently attracted over two-thirds of all mosquitoes released. This was the case in the absence (‘pull’ only) and in the presence of a spatial repellent (‘push-pull’), indicating that in its current configuration the tested ‘pull’ does not provide a valuable addition to a spatial repellent. The chemical 2-butanone was ineffective in replacing CO2. Transfluthrin was detectable in the air space but with a strong linear reduction in concentrations over 5 m from release. The MB5 constituent chemicals were only irregularly detected, potentially suggesting insufficient release and concentration in the air for attraction. Conclusion This step-by-step evaluation of the selected ‘push’ and ‘pull’ components led to a better understanding of their ability to affect host-seeking behaviours of the malaria vector An. arabiensis in the peri-domestic space and helps to gauge the impact such tools would have when used in the field for monitoring or control.![]()
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Affiliation(s)
- Margaret Mendi Njoroge
- International Centre of Insect Physiology and Ecology (icipe), Human Health Theme, Nairobi, 00100, Kenya.,Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands
| | - Ulrike Fillinger
- International Centre of Insect Physiology and Ecology (icipe), Human Health Theme, Nairobi, 00100, Kenya.
| | - Adam Saddler
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Socinstrasse 57, 4051 833, Basel, Switzerland.,University of Basel, Petersplatz 1, Basel, Switzerland.,Department of Environmental Health and Ecological Sciences, Ifakara Health Institute, P.O. Box 74, Bagamoyo, Tanzania
| | - Sarah Moore
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Socinstrasse 57, 4051 833, Basel, Switzerland.,University of Basel, Petersplatz 1, Basel, Switzerland.,Department of Environmental Health and Ecological Sciences, Ifakara Health Institute, P.O. Box 74, Bagamoyo, Tanzania
| | - Willem Takken
- Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands
| | - Joop J A van Loon
- Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands
| | - Alexandra Hiscox
- International Centre of Insect Physiology and Ecology (icipe), Human Health Theme, Nairobi, 00100, Kenya.,Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands.,London School of Hygiene and Tropical Medicine, ARCTEC, Keppel Street, London, WC1E 7HT, UK
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Lupenza ET, Kihonda J, Limwagu AJ, Ngowo HS, Sumaye RD, Lwetoijera DW. Using pastoralist community knowledge to locate and treat dry-season mosquito breeding habitats with pyriproxyfen to control Anopheles gambiae s.l. and Anopheles funestus s.l. in rural Tanzania. Parasitol Res 2021; 120:1193-1202. [PMID: 33409645 DOI: 10.1007/s00436-020-07040-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Accepted: 12/25/2020] [Indexed: 10/22/2022]
Abstract
Fundamentally, larviciding with pyriproxyfen (PPF) has potential to complement Long Lasting Insecticide Nets (LLINs) and indoor residual sprays (IRS) in settings where resistance to pyrethroids and residual malaria transmission exist. In this study, we evaluated the field effectiveness of larviciding using PPF to reduce dry season productivity of mosquito breeding habitats that were located by pastoralists within the study area. Using pastoralist knowledge, dry season breeding habitats in Mofu village rural Tanzania were located and monitored for larval productivity for a period of 8 months before PPF intervention. During the intervention, six out of twelve breeding habitats were treated with Sumilarv 0.5G PPF granules. The impact of deposited PPF was monitored by recording emergence inhibition of larvae collected from treated habitats compared to the appropriate control group for a period of three months and half post-intervention. During baseline, the average proportion (+SD) of adult emerged was similar between two clusters, with (0.89 + 0.22) for the control cluster and (0.93 + 0.16) for the treatment cluster of breeding habitats. Following treatment with PPF, the average proportion (+SD) of adult emerged in the treated breeding habitats was significantly low (0.096 + 0.22) compared to adults that emerged from larvae in the untreated habitats (0.99 + 0.22) (p < 0.0001). Of all emerged adults, approximately 94% were An. gambiae s.l. and the remaining 6% were An. funestus s.l. This is the first study demonstrating the usefulness of engaging pastoralist community to locate and identify hard to find mosquito breeding habitats. Reduced productivity of the targeted habitats with PPF offers prospect of implementing PPF larviciding in dry season when habitats are few and permanent to control mosquito population in rural settings.
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Affiliation(s)
- Eliza T Lupenza
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Japhet Kihonda
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Alex J Limwagu
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Halfan S Ngowo
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Robert D Sumaye
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Dickson W Lwetoijera
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania. .,School of Life Science and Bioengineering, Nelson Mandela African Institution of Science & Technology, Arusha, Tanzania.
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Su T, Mullens P, Thieme J, Melgoza A, Real R, Brown MQ. Deployment and Fact Analysis of the In2Care® Mosquito Trap, A Novel Tool for Controlling Invasive Aedes Species. JOURNAL OF THE AMERICAN MOSQUITO CONTROL ASSOCIATION 2020; 36:167-174. [PMID: 33600585 DOI: 10.2987/20-6929.1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
During April-October 2019, the West Valley Mosquito and Vector Control District (Ontario, CA) deployed large numbers of In2Care® mosquito traps in a preliminary study to evaluate the trap's potential effectiveness at controlling invasive Aedes aegypti (L.) and Ae. albopictus (Skuse) in 6 cities of San Bernardino County, CA. The trap was used to attract ovipositing females, expose them to the juvenile hormone mimic pyriproxyfen and the entomopathogenic fungus Beauveria bassiana, and autodisseminate pyriproxyfen to other water sources prior to their death from fungal infection. The trap attracted Ae. aegypti and Culex quinquefasciatus, with the latter species predominating at much higher larval densities in the trap reservoirs. Field-collected larvae and pupae from the trap reservoirs showed complete adult emergence inhibition. Furthermore, the trap reservoirs retained high levels of residual larvicidal, pupicidal, and emergence inhibition activity after they were retrieved from the field, as indicated by laboratory bioassays against laboratory colony of Cx. quinquefasciatus. Results of this study support more detailed quantitative local evaluations on trap efficacy to measure the impact of the In2Care mosquito trap on wild invasive Aedes and Culex populations in future mosquito control efforts.
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Affiliation(s)
- Tianyun Su
- West Valley Mosquito and Vector Control District, 1295 E Locust Street, Ontario, CA 91761
| | - Patrick Mullens
- West Valley Mosquito and Vector Control District, 1295 E Locust Street, Ontario, CA 91761
| | - Jennifer Thieme
- West Valley Mosquito and Vector Control District, 1295 E Locust Street, Ontario, CA 91761
| | - Alfonso Melgoza
- West Valley Mosquito and Vector Control District, 1295 E Locust Street, Ontario, CA 91761
| | - Robert Real
- West Valley Mosquito and Vector Control District, 1295 E Locust Street, Ontario, CA 91761
| | - Michelle Q Brown
- West Valley Mosquito and Vector Control District, 1295 E Locust Street, Ontario, CA 91761
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Unlu I, Rochlin I, Suman DS, Wang Y, Chandel K, Gaugler R. Large-Scale Operational Pyriproxyfen Autodissemination Deployment to Suppress the Immature Asian Tiger Mosquito (Diptera: Culicidae) Populations. JOURNAL OF MEDICAL ENTOMOLOGY 2020; 57:1120-1130. [PMID: 32006427 PMCID: PMC7448106 DOI: 10.1093/jme/tjaa011] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Indexed: 05/15/2023]
Abstract
Effective suppression of container-inhabiting Asian Tiger [Aedes albopictus (Skuse)] (Diptera: Culicidae) and yellow fever [Aedes aegypti (L.)] (Diptera: Culicidae) mosquitoes presents one of the most intractable problems for modern mosquito control. Traditional tools often fail to control populations of these mosquito species, and are prohibitively expensive or have negative environmental impacts. Novel approaches and tools are urgently needed for integrated container-inhabiting mosquito management programs. One of the most promising techniques is autodissemination. We present the results of a long-term large-scale study conducted in a temperate urbanized environment representing typical Ae. albopictus habitats. Three treatment sites with autodissemination stations and three nearby reference sites were monitored for eggs, immature, and adult mosquitoes over a period of 3 yr from 2014 to 2016. Elevated larval and pupal mortality of 12-19% on average was the most notable outcome in sentinel cups of the treatment sites. The number of eggs in the treatment sites was significantly reduced in 2014, but not in 2015 or 2016. Adult populations remained similar in treatment and reference sites throughout the study. The impact of autodissemination on mosquito populations was lower than reported by previous investigations. Technical and logistical problems associated with wider coverage and working in multiple urban neighborhoods contributed to reduced efficacy. Incorporating autodissemination with routine mosquito control operations and commercializing this methodology for general public use will require further research on combining this tool with other novel or conventional technologies.
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Affiliation(s)
- Isik Unlu
- Center for Vector Biology, Rutgers University, New Brunswick, NJ
- Corresponding author, e-mail:
| | - Ilia Rochlin
- Center for Vector Biology, Rutgers University, New Brunswick, NJ
| | - Devi S Suman
- Center for Vector Biology, Rutgers University, New Brunswick, NJ
| | - Yi Wang
- Center for Vector Biology, Rutgers University, New Brunswick, NJ
| | - Kshitij Chandel
- Center for Vector Biology, Rutgers University, New Brunswick, NJ
| | - Randy Gaugler
- Center for Vector Biology, Rutgers University, New Brunswick, NJ
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Modelling the control of Aedes albopictus mosquitoes based on sterile males release techniques in a tropical environment. Ecol Modell 2020. [DOI: 10.1016/j.ecolmodel.2020.109002] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Yadav K, Dhiman S, Acharya BN, Ghorpade RR, Sukumaran D. Pyriproxyfen treated surface exposure exhibits reproductive disruption in dengue vector Aedes aegypti. PLoS Negl Trop Dis 2019; 13:e0007842. [PMID: 31738760 PMCID: PMC6886876 DOI: 10.1371/journal.pntd.0007842] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 12/02/2019] [Accepted: 10/13/2019] [Indexed: 11/21/2022] Open
Abstract
Background Reduced susceptibility of mosquito vectors to currently used insecticides hampers control interventions. Recently pyriproxyfen, an insect growth regulator has been demonstrated to effectively reduce the reproductive potential in vector mosquitoes. Methods Pyriproxyfen (PPF), in different concentrations (0.75%, 0.075%, 0.0075%, and 0.00075%) was applied on papers and Indian wild type Aedes aegypti female mosquitoes (N ≥ 20 for each treatment) were exposed onto it as per WHO guidelines, to study the reproductive disruption. PPF concentration on treated papers was quantitatively cross-determined using HPLC method. Reduction in fecundity, fertility and adult emergence in exposed female Ae. aegypti was determined. Abnormal development in ovary and eggs of exposed females was studied microscopically after different time intervals. Results Eggs laid, eggs hatched, pupae formed and adults emerged per female exposed in both before blood meal and after blood meal groups declined significantly from lowest to highest concentration of PPF (F ≥ 5.2; p < 0.02). Adult emergence inhibition in females exposed to PPF before and after blood meal groups ranged from 58.8% [OR = 0.18 (95% CI = 0.09–0.36)] to 79.2% [OR = 0.04 (95% CI = 0.02–0.10)] and 64.4% [OR = 0.12 (95% CI = 0.05–0.28)] to 77.1% [OR = 0.05 (95% CI = 0.02–0.14)] respectively in different concentrations. The probit model used suggested that FI50 (50% fertility inhibition) and EI50 (50% emergence inhibition) were 0.002% (p = 0.82) and 0.0001% (p = 0.99) for females exposed before blood meal, while 0.01% (p = 0.63) and <0.0001% (p = 0.98) for the females exposed after blood meal, respectively. The eggs laid by the females exposed to PPF-treated surface showed altered body organization, desegmentation and disoriented abdominal and cervical regions in the developing embryo. Quantification of PPF on impregnated papers showed that it was uniformly distributed throughout the matrix. Conclusions The present study has shown that tarsal contact to PPF-treated surface for a small time drastically influenced the fecundity, fertility and adult emergence in Indian wild Ae. aegypti mosquitoes. Results suggest that a certain minimum concentration of PPF through contact exposure can reduce the abundance of vector mosquitoes to a considerable level. The formulations based on combination of PPF and other compatible insecticides may be an impactful approach where susceptible mosquitoes are killed by the insecticide component while resistant mosquitoes are sterilised by PPF. Development of resistance against insecticides has challenged mosquito control programmes globally and prompted the research of alternative options that can complement insecticides. An insect growth regulator, pyriproxyfen (PPF) usage against mosquitoes can effectively reduce the vector population. PPF mainly inhibits the metamorphosis of mosquito larvae into pupae and prevent the adult emergence, therefore it is generally applied in mosquito breeding habitats. PPF has been shown to exhibit delayed residual effect that may impair the reproductive capacity by affecting the survival, fecundity and fertility of adult mosquito exposed through tarsal contact. Presently, the effectiveness of different concentrations of PPF intended to be delivered through contact have been evaluated against dengue vector Ae. aegypti. Results suggested that very low PPF concentration treated surfaces drastically reduce the fecundity, fertility and adult emergence in mosquitoes. Study suggests that control interventions based on PPF-treated surfaces could provide an additional route to target mosquito vector control by overall population density reduction.
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Affiliation(s)
- Kavita Yadav
- Vector Management Division, Defence Research and Development Establishment, Gwalior, Madhya Pradesh, India
- * E-mail:
| | - Sunil Dhiman
- Vector Management Division, Defence Research and Development Establishment, Gwalior, Madhya Pradesh, India
| | - BN Acharya
- Synthetic Chemistry Division, Defence Research and Development Establishment, Gwalior, Madhya Pradesh, India
| | - Rama Rao Ghorpade
- Synthetic Chemistry Division, Defence Research and Development Establishment, Gwalior, Madhya Pradesh, India
| | - Devanathan Sukumaran
- Vector Management Division, Defence Research and Development Establishment, Gwalior, Madhya Pradesh, India
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12
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Junges MT, Harburguer L, Lorenzo MC, Eisenberg P, Masuh H, Carbajo AE. Soil presence reduces the control effectiveness of a slow-release formulation of pyriproxyfen on Aedes aegypti (Diptera: Culicidae) larvae. Trop Med Int Health 2019; 25:216-221. [PMID: 31691403 DOI: 10.1111/tmi.13333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE To assess the influence of soil on the effectiveness of two new slow-release formulations (floating and non-floating) of pyriproxyfen coextruded with low-density polyethylene. METHODS Two slow-release devices were developed using low-density polyethylene, pyriproxyfen as larvicide and calcium carbonate as filler. A factorial design was used to evaluate the effect of soil presence on the performance of each device. Weekly bioassays were performed. RESULTS Soil presence affected treatment effectiveness, but this effect was associated with device type. The tablets were effective for nearly 3 months. CONCLUSION Treatment effectiveness could be reduced because of the loss of pyriproxyfen by several physico-chemical processes such as adsorption into the soil.
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Affiliation(s)
- Melania Teresita Junges
- Laboratorio de Ecología de Enfermedades Transmitidas por Vectores, Universidad Nacional de San Martín, San Martín, Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas, CABA, Argentina
| | - Laura Harburguer
- Consejo Nacional de Investigaciones Científicas y Técnicas, CABA, Argentina.,Centro de Investigaciones de Plagas e Insecticidas, Unidad de Investigación y Desarrollo Estratégico para la Defensa, Villa Martelli, Buenos Aires, Argentina
| | - Maria Cecilia Lorenzo
- Dirección de Materiales Avanzados, INTI-Áreas del Conocimiento, San Martín, , Buenos Aires, Argentina.,Instituto de Investigación e Ingeniería Ambiental, Universidad Nacional de San Martín, San Martín, Buenos Aires, Argentina
| | - Patricia Eisenberg
- Dirección de Materiales Avanzados, INTI-Áreas del Conocimiento, San Martín, , Buenos Aires, Argentina.,Instituto de Investigación e Ingeniería Ambiental, Universidad Nacional de San Martín, San Martín, Buenos Aires, Argentina
| | - Héctor Masuh
- Consejo Nacional de Investigaciones Científicas y Técnicas, CABA, Argentina.,Centro de Investigaciones de Plagas e Insecticidas, Unidad de Investigación y Desarrollo Estratégico para la Defensa, Villa Martelli, Buenos Aires, Argentina
| | - Aníbal Eduardo Carbajo
- Laboratorio de Ecología de Enfermedades Transmitidas por Vectores, Universidad Nacional de San Martín, San Martín, Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas, CABA, Argentina
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Djamouko-Djonkam L, Mounchili-Ndam S, Kala-Chouakeu N, Nana-Ndjangwo SM, Kopya E, Sonhafouo-Chiana N, Talipouo A, Ngadjeu CS, Doumbe-Belisse P, Bamou R, Toto JC, Tchuinkam T, Wondji CS, Antonio-Nkondjio C. Spatial distribution of Anopheles gambiae sensu lato larvae in the urban environment of Yaoundé, Cameroon. Infect Dis Poverty 2019; 8:84. [PMID: 31594541 PMCID: PMC6784347 DOI: 10.1186/s40249-019-0597-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Accepted: 09/10/2019] [Indexed: 11/23/2022] Open
Abstract
Background The rapid and unplanned urbanization of African cities is considered to increase the risk of urban malaria transmission. The present study objective was to assess factors influencing the spatio-temporal distribution of Anopheles gambiae s.l. larvae in the city of Yaoundé, Cameroon. Methods All water bodies were checked once every 2 months for the presence of mosquito larvae from March 2017 to May 2018 in 32 districts of Yaoundé. Physico-chemical characteristics including the size, depth, turbidity, pH, temperature, conductivity, sulfates, organophosphates, hydrogen peroxide (H2O2), conductivity, iron and calcium were recorded and analyzed according to anopheline larvae presence or absence. High resolution satellite images from landsat sentinel Enhanced Thematic Mapper were used for spatial mapping of both field and environmental variables. Bivariate and multivariate logistic regression models were used to identify variables closely associated with anopheline larvae distribution. Results A total of 18 696 aquatic habitats were checked and only 2942 sites (15.7%) contained anopheline larvae. A high number of sites with anopheline larvae (≥ 69%) presented late instar larvae (L3, L4 and pupae). Anopheline mosquito larvae were sampled from a variety of breeding sites including puddles (51.6%), tire prints (12.9%), wells (11.7%) and drains (11.3%). Bivariate logistic regression analyses associated anopheline larvae presence with the absence of predators, absence of algae, absence of vegetation and depth of less than 1 m. Conductivity, turbidity, organophosphates, H2O2 and temperature were significantly high in breeding sites with anopheline larvae than in breeding sites without these larvae (P < 0.1). Anopheline species collected included An. coluzzii (91.1%) and An. gambiae s.s. (8.9%). GIS mapping indicated a heterogeneous distribution of anopheline breeding habitats in the city of Yaoundé. Land cover analysis indicated high variability of the city of Yaoundé’s landscape. Conclusions The data confirms adaptation of An. gambiae s.l. to the urban domain in the city of Yaoundé and calls for urgent actions to improve malaria vector control.
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Affiliation(s)
- Landre Djamouko-Djonkam
- Malaria Research Laboratory, Organization for the fight against Endemic diseases in Central Africa (OCEAC), P.O. Box 288, Yaoundé, Cameroon.,Vector Borne Infectious Disease Unit of the Laboratory of Applied Biology and Ecology (VBID-LABEA), Department of Animal Biology, Faculty of Science, University of Dschang, P.O. Box 067, Dschang, Cameroon
| | - Souleman Mounchili-Ndam
- Malaria Research Laboratory, Organization for the fight against Endemic diseases in Central Africa (OCEAC), P.O. Box 288, Yaoundé, Cameroon.,Faculty of Science, University of Yaounde I, P.O. Box 337, Yaounde, Cameroon
| | - Nelly Kala-Chouakeu
- Malaria Research Laboratory, Organization for the fight against Endemic diseases in Central Africa (OCEAC), P.O. Box 288, Yaoundé, Cameroon.,Vector Borne Infectious Disease Unit of the Laboratory of Applied Biology and Ecology (VBID-LABEA), Department of Animal Biology, Faculty of Science, University of Dschang, P.O. Box 067, Dschang, Cameroon
| | - Stella Mariette Nana-Ndjangwo
- Malaria Research Laboratory, Organization for the fight against Endemic diseases in Central Africa (OCEAC), P.O. Box 288, Yaoundé, Cameroon.,Faculty of Science, University of Yaounde I, P.O. Box 337, Yaounde, Cameroon
| | - Edmond Kopya
- Malaria Research Laboratory, Organization for the fight against Endemic diseases in Central Africa (OCEAC), P.O. Box 288, Yaoundé, Cameroon.,Faculty of Science, University of Yaounde I, P.O. Box 337, Yaounde, Cameroon
| | - Nadége Sonhafouo-Chiana
- Malaria Research Laboratory, Organization for the fight against Endemic diseases in Central Africa (OCEAC), P.O. Box 288, Yaoundé, Cameroon.,Faculty of Health Sciences University of Buea, P.O. Box 63, Buea, Cameroon
| | - Abdou Talipouo
- Malaria Research Laboratory, Organization for the fight against Endemic diseases in Central Africa (OCEAC), P.O. Box 288, Yaoundé, Cameroon.,Faculty of Science, University of Yaounde I, P.O. Box 337, Yaounde, Cameroon
| | - Carmene Sandra Ngadjeu
- Malaria Research Laboratory, Organization for the fight against Endemic diseases in Central Africa (OCEAC), P.O. Box 288, Yaoundé, Cameroon.,Faculty of Science, University of Yaounde I, P.O. Box 337, Yaounde, Cameroon
| | - Patricia Doumbe-Belisse
- Malaria Research Laboratory, Organization for the fight against Endemic diseases in Central Africa (OCEAC), P.O. Box 288, Yaoundé, Cameroon.,Faculty of Science, University of Yaounde I, P.O. Box 337, Yaounde, Cameroon
| | - Roland Bamou
- Malaria Research Laboratory, Organization for the fight against Endemic diseases in Central Africa (OCEAC), P.O. Box 288, Yaoundé, Cameroon.,Vector Borne Infectious Disease Unit of the Laboratory of Applied Biology and Ecology (VBID-LABEA), Department of Animal Biology, Faculty of Science, University of Dschang, P.O. Box 067, Dschang, Cameroon
| | - Jean Claude Toto
- Malaria Research Laboratory, Organization for the fight against Endemic diseases in Central Africa (OCEAC), P.O. Box 288, Yaoundé, Cameroon
| | - Timoléon Tchuinkam
- Vector Borne Infectious Disease Unit of the Laboratory of Applied Biology and Ecology (VBID-LABEA), Department of Animal Biology, Faculty of Science, University of Dschang, P.O. Box 067, Dschang, Cameroon
| | | | - Christophe Antonio-Nkondjio
- Malaria Research Laboratory, Organization for the fight against Endemic diseases in Central Africa (OCEAC), P.O. Box 288, Yaoundé, Cameroon. .,Vector Biology Liverpool School of Tropical medicine Pembroke Place, Liverpool, L3 5QA, UK.
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Mbare O, Lindsay SW, Fillinger U. Testing a pyriproxyfen auto-dissemination station attractive to gravid Anopheles gambiae sensu stricto for the development of a novel attract-release -and-kill strategy for malaria vector control. BMC Infect Dis 2019; 19:800. [PMID: 31510931 PMCID: PMC6740013 DOI: 10.1186/s12879-019-4438-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2019] [Accepted: 09/04/2019] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND Larviciding is an effective supplementary tool for malaria vector control, but the identification and accessibility of aquatic habitats impedes application. Dissemination of the insect growth regulator, pyriproxyfen (PPF), by gravid Anopheles might constitute a novel application strategy. This study aimed to explore the feasibility of using an attractive bait-station to contaminate gravid Anopheles gambiae sensu stricto with PPF and subsequently transfer PPF to larval habitats. METHODS A bait-station was developed comprising of an artificial pond containing water treated with 20 ppm cedrol, an oviposition attractant, and a netting-cover treated with PPF. Three identical semi-field cages were used to assess the potential of gravid Anopheles to transfer PPF from the bait-station to ponds. Gravid females were released in two semi-field cages, one with PPF on its bait-station (test) and one without PPF (control). No mosquitoes were released in the third cage with a PPF-treated station (control). Transfer of PPF to open ponds was assessed by monitoring emergence of late instar insectary-reared larvae introduced into the ponds. The amount of PPF carried by a mosquito and transferred to water was quantified using liquid chromatography-mass spectrometry. RESULTS In the controls, 86% (95% CI 81-89%) of larvae introduced into open ponds developed into adults, indicating that wind did not distribute PPF in absence of mosquitoes. Emergence inhibition was observed in the test cage but was dependent on the distance between pond and bait-station. Only 25% (95% CI 22-29%) of larvae emerged as adults from ponds 4 m from the bait-station, but 92% (95% CI 89-94%) emerged from ponds 10 m away. Each mosquito was contaminated on average with 112 μg (95% CI 93-123 μg) PPF resulting in the transfer of 230 ng/L (95% CI 180-290 ng/L) PPF to 100 ml volumes of water. CONCLUSIONS The bait-stations successfully attracted gravid females which were subsequently dusted with effective levels of PPF. However, in this study design, attraction and dissemination was limited to short distances. To make this approach feasible for malaria vector control, stronger attractants that lure gravid females from longer distances, in landscapes with many water bodies, and better PPF delivery systems are needed.
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Affiliation(s)
- Oscar Mbare
- International Centre of Insect Physiology and Ecology, Human Health Theme, Nairobi, Kenya
- London School of Hygiene and Tropical Medicine, London, UK
| | | | - Ulrike Fillinger
- International Centre of Insect Physiology and Ecology, Human Health Theme, Nairobi, Kenya
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15
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Khemrattrakool P, Yanola J, Lumjuan N, Somboon P. Pyriproxyfen-Treated Polypropylene Sheets and Resting Boxes for Controlling Mosquitoes in Livestock Operations. INSECTS 2019; 10:E55. [PMID: 30781681 PMCID: PMC6410238 DOI: 10.3390/insects10020055] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 02/13/2019] [Accepted: 02/14/2019] [Indexed: 01/21/2023]
Abstract
Many insect vector species of medical and veterinary importance are found abundantly in areas where animals are held. In these areas, they often rest for a period of time on objects around the animals both before and after blood feeding. However, the use of neurotoxic insecticides for vector control is not advised for use in such shelters as these chemicals can pose hazards to animals. The present study evaluated the efficacy of pyriproxyfen (PPF), an insect growth regulator, applied to polypropylene sheets and resting boxes on the reproductivity of mosquitoes found in animal shelters in Chiang Mai, Thailand. The sheets sprayed with 666 mg PPF/m² were set on the inner wall of a cowshed and kept in place for 3 h (6.00 to 9.00 pm). During this time, fully blood-fed female mosquitoes that landed and remained continuously on the sheets for 5, 10, and 20 min were collected. The results, involving Anopheles subpictus, An. vagus, Culex gelidus, Cx. tritaeniorhynchus, and Cx. vishnui, revealed significant reductions in oviposition rates, egg hatchability, pupation, and adult emergence in the PPF-treated groups compared to the control groups. Adult emergence rates were reduced to 85.6⁻94.9% and 95.5⁻100% in those exposed for 10 and 20 min, respectively. The sheets retained their effectiveness for three months. The PPF-treated (666 mg/m²) resting boxes (35 × 35 × 55 cm) were placed overnight at a chicken farm where Cx. quinquefasciatus predominated. Blood-fed mosquitoes were collected in the morning and reared in the laboratory. Oviposition rates were reduced by 71.7% and adult emergence was reduced by 97.8% compared to the controls. PPF residual spray on surface materials in animal sheds is a potential method for controlling mosquitoes. Further studies are needed to evaluate the impact of PPF-treated materials on wild populations.
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Affiliation(s)
- Pattarapon Khemrattrakool
- Center of Insect Vector Study, Department of Parasitology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand.
- Graduate PhD's Degree Program in Parasitology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand.
| | - Jintana Yanola
- Department of Medical Technology, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai 50200, Thailand.
| | - Nongkran Lumjuan
- Research Institute for Health Sciences, Chiang Mai University, Chiang Mai 50200, Thailand.
| | - Pradya Somboon
- Center of Insect Vector Study, Department of Parasitology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand.
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Spielmeyer A, Schetelig MF, Etang J. High-throughput analysis of insecticides on malaria vectors using liquid chromatography tandem mass spectrometry. PLoS One 2019; 14:e0211064. [PMID: 30730918 PMCID: PMC6366735 DOI: 10.1371/journal.pone.0211064] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Accepted: 12/21/2018] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Different setups and protocols have been developed for investigating insecticide effects on Anopheles (An.) mosquitoes, vectors of malaria. However, chemical uptake resulting from their tarsal contact with insecticide-treated material has seldom been investigated. To address the challenges encountered in the interpretation of bioassay data, a high throughput method for chemical analysis on malaria vectors was developed and validated for five selected insecticides including alpha-cypermethrin (aCYP), deltamethrin (DM), etofenprox (EPX), permethrin (PM), pirimiphos-methyl (PPM). METHODS The method includes a single chemical extraction step via an ultrasound probe on mosquito samples and analysis via liquid chromatography coupled to high-resolution tandem mass spectrometry (UHPLC-MS/MS). The protocol was established for two malaria vector species, Anopheles gambiae senso stricto (s.s.) and An. stephensi, both males and females. Recovery rates ranged from 70 to 100% without any influence of sex or species. The method was efficiently applied to female An. gambiae s.s. of the KISUMU1 reference strain, after susceptibility tests using the World Health Organization's standard protocol. RESULTS Susceptibility tests revealed 13.4-18.4 minutes knockdown times for 50% mosquitoes during exposure to EPX and pyrethroids. The mortality rates 24 hours post-exposure to insecticides were mostly 99-100%, except in two PM and three PPM assays suggesting possible or confirmed resistance to these insecticides. The mean insecticide uptake in dead mosquitoes ranged from 23 pg (aCYP) to 1812 pg (EPX) per specimen. However, the mean uptake in survivors to PM and PPM was reduced by at least 25%, suggesting that acute doses were not achieved in these specimens during bioassays. CONCLUSIONS The developed and validated UHPLC-MS/MS method could be used to address some limitations of bioassays or to assess the penetration of insecticides in mosquito matrix with reference to cuticle thickness and other insecticide resistance mechanisms.
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Affiliation(s)
- Astrid Spielmeyer
- Justus Liebig University Giessen, Institute for Food Chemistry and Food Biotechnology, Giessen, Germany
| | - Marc F. Schetelig
- Justus Liebig University Giessen, Institute for Insect Biotechnology, Giessen, Germany
| | - Josiane Etang
- Justus Liebig University Giessen, Institute for Insect Biotechnology, Giessen, Germany
- Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), Institut de Recherche de Yaoundé (IRY), Yaoundé, Cameroun
- University of Douala, Faculty of Medicine and Pharmaceutical Sciences, Douala, Cameroon
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17
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Weetman D, Kamgang B, Badolo A, Moyes CL, Shearer FM, Coulibaly M, Pinto J, Lambrechts L, McCall PJ. Aedes Mosquitoes and Aedes-Borne Arboviruses in Africa: Current and Future Threats. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2018; 15:ijerph15020220. [PMID: 29382107 PMCID: PMC5858289 DOI: 10.3390/ijerph15020220] [Citation(s) in RCA: 130] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 01/23/2018] [Accepted: 01/24/2018] [Indexed: 12/21/2022]
Abstract
The Zika crisis drew attention to the long-overlooked problem of arboviruses transmitted by Aedes mosquitoes in Africa. Yellow fever, dengue, chikungunya and Zika are poorly controlled in Africa and often go unrecognized. However, to combat these diseases, both in Africa and worldwide, it is crucial that this situation changes. Here, we review available data on the distribution of each disease in Africa, their Aedes vectors, transmission potential, and challenges and opportunities for Aedes control. Data on disease and vector ranges are sparse, and consequently maps of risk are uncertain. Issues such as genetic and ecological diversity, and opportunities for integration with malaria control, are primarily African; others such as ever-increasing urbanization, insecticide resistance and lack of evidence for most control-interventions reflect problems throughout the tropics. We identify key knowledge gaps and future research areas, and in particular, highlight the need to improve knowledge of the distributions of disease and major vectors, insecticide resistance, and to develop specific plans and capacity for arboviral disease surveillance, prevention and outbreak responses.
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Affiliation(s)
- David Weetman
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK.
| | - Basile Kamgang
- Centre for Research in Infectious Diseases, Yaoundé PO Box 13501, Cameroon.
| | - Athanase Badolo
- Laboratoire d'Entomologie Fondamentale et Appliquée (LEFA), Université Ouaga 1 Pr Joseph Ki-Zerbo, Ouagadougou 03 BP 7021, Burkina Faso.
| | - Catherine L Moyes
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford OX3 7LF, UK.
| | - Freya M Shearer
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford OX3 7LF, UK.
| | - Mamadou Coulibaly
- University of Sciences, Techniques and Technologies of Bamako, Bamako BP 1805, Mali.
| | - João Pinto
- Global Health and Tropical Medicine (GHTM), Instituto de Higiene e Medicina Tropical (IHMT), Universidade Nova de Lisboa (UNL), Rua da Junqueira 100, 1349-008 Lisbon, Portugal.
| | - Louis Lambrechts
- Insect-Virus Interactions, Department of Genomes and Genetics, Institut Pasteur, 75015 Paris, France.
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 2000, 75015 Paris, France.
| | - Philip J McCall
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK.
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Exploring the potential of using cattle for malaria vector surveillance and control: a pilot study in western Kenya. Parasit Vectors 2017; 10:18. [PMID: 28069065 PMCID: PMC5223359 DOI: 10.1186/s13071-016-1957-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Accepted: 12/23/2016] [Indexed: 12/02/2022] Open
Abstract
Background Malaria vector mosquitoes with exophilic and zoophilic tendencies, or with a high acceptance of alternative blood meal sources when preferred human blood-hosts are unavailable, may help maintain low but constant malaria transmission in areas where indoor vector control has been scaled up. This residual transmission might be addressed by targeting vectors outside the house. Here we investigated the potential of insecticide-treated cattle, as routinely used for control of tsetse and ticks in East Africa, for mosquito control. Methods The malaria vector population in the study area was investigated weekly for 8 months using two different trapping tools: light traps indoors and cattle-baited traps (CBTs) outdoors. The effect of the application of the insecticide deltamethrin and the acaricide amitraz on cattle on host-seeking Anopheles arabiensis was tested experimentally in field-cages and the impact of deltamethrin-treated cattle explored under field conditions on mosquito densities on household level. Results CBTs collected on average 2.8 (95% CI: 1.8–4.2) primary [Anopheles gambiae (s.s.), An. arabiensis and An. funestus (s.s.)] and 6.3 (95% CI: 3.6–11.3) secondary malaria vectors [An. ivulorum and An. coustani (s.l.)] per trap night and revealed a distinct, complementary seasonality. At the same time on average only 1.4 (95% CI: 0.8–2.3) primary and 1.1 (95% CI: 0.6–2.0) secondary malaria vectors were collected per trap night with light traps indoors. Amitraz had no effect on survival of host-seeking An. arabiensis under experimental conditions but deltamethrin increased mosquito mortality (OR 19, 95% CI: 7–50), but only for 1 week. In the field, vector mortality in association with deltamethrin treatment was detected only with CBTs and only immediately after the treatment (OR 0.25, 95% CI: 0.13–0.52). Conclusions Entomological sampling with CBTs highlights that targeting cattle for mosquito control has potential since it would not only target naturally zoophilic malaria vectors but also opportunistic feeders that lack access to human hosts as is expected in residual malaria transmission settings. However, the deltamethrin formulation tested here although used widely to treat cattle for tsetse and tick control, is not suitable for the control of malaria vectors since it causes only moderate initial mortality and has little residual activity.
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Yunta C, Grisales N, Nász S, Hemmings K, Pignatelli P, Voice M, Ranson H, Paine MJI. Pyriproxyfen is metabolized by P450s associated with pyrethroid resistance in An. gambiae. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2016; 78:50-57. [PMID: 27613592 PMCID: PMC6399515 DOI: 10.1016/j.ibmb.2016.09.001] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Revised: 08/31/2016] [Accepted: 09/02/2016] [Indexed: 05/25/2023]
Abstract
Pyrethroid resistance is widespread in the malaria vector Anopheles gambiae leading to concerns about the future efficacy of bednets with pyrethroids as the sole active ingredient. The incorporation of pyriproxyfen (PPF), a juvenile hormone analogue, into pyrethroid treated bednets is being trialed in Africa. Pyrethroid resistance is commonly associated with elevated levels of P450 expression including CYPs 6M2, 6P2, 6P3, 6P4, 6P5, 6Z2 and 9J5. Having expressed these P450s in E. coli we find all are capable of metabolizing PPF. Inhibition of these P450s by permethrin, deltamethrin and PPF was also examined. Deltamethrin and permethrin were moderate inhibitors (IC50 1-10 μM) of diethoxyfluorescein (DEF) activity for all P450s apart from CYP6Z2 (IC50 > 10 μM), while PPF displayed weaker inhibition of all P450s (IC50 > 10 μM) except CYP's 6Z2 and 6P2 (IC50 1-10 μM). We found evidence of low levels of cross resistance between PPF and other insecticide classes by comparing the efficacy of PPF in inhibiting metamorphosis and inducing female sterility in an insecticide susceptible strain of An. gambiae and a multiple resistant strain from Cote d'Ivoire.
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Affiliation(s)
- Cristina Yunta
- Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Nelson Grisales
- Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Szilárd Nász
- Syngenta, Product Metabolism and Analytical Sciences, Jealott's Hill International Research Centre, Bracknell, RG42 6EY, UK
| | - Kay Hemmings
- Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | | | | | - Hilary Ranson
- Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Mark J I Paine
- Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK.
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Zhou G, Wiseman V, Atieli HE, Lee MC, Githeko AK, Yan G. The impact of long-lasting microbial larvicides in reducing malaria transmission and clinical malaria incidence: study protocol for a cluster randomized controlled trial. Trials 2016; 17:423. [PMID: 27558161 PMCID: PMC4997667 DOI: 10.1186/s13063-016-1545-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 08/06/2016] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND The massive scale-up of insecticide-treated nets (ITNs) and indoor residual spraying (IRS) has led to a substantial increase in malaria vector insecticide resistance as well as in increased outdoor transmission, both of which hamper the effectiveness and efficiency of ITN and IRS. Long-lasting microbial larvicide can be a cost-effective new supplemental intervention tool for malaria control. METHODS/DESIGN We will implement the long-lasting microbial larvicide intervention in 28 clusters in two counties in western Kenya. We will test FourStar controlled release larvicide (6 % by weight Bacillus thuringiensis israelensis and 1 % Bacillus sphaerius) by applying FourStar controlled release granule formulation, 90-day briquettes, and 180-day briquettes in different habitat types. The primary endpoint is clinical malaria incidence rate and the secondary endpoint is malaria vector abundance and transmission intensity. The intervention will be conducted as a two-step approach. First, we will conduct a four-cluster trial (two clusters per county, with one of the two clusters randomly assigned to the intervention arm) to optimize the larvicide application scheme. Second, we will conduct an open-label, cluster-randomized trial to evaluate the effectiveness and cost-effectiveness of the larvicide. Fourteen clusters in each county will be assigned to intervention (treatment) or no intervention (control) by a block randomization on the basis of clinical malaria incidence, vector density, and human population size per site. We will treat each treatment cluster with larvicide for three rounds at 4-month intervals, followed by no treatment for the following 8 months. Next, we will switch the control and treatment sites. The former control sites will receive three rounds of larvicide treatment at appropriate time intervals, and former treatment sites will receive no larvicide. We will monitor indoor and outdoor vector abundance using CO2-baited CDC light traps equipped with collection bottle rotators. Clinical malaria data will be aggregated from government-run malaria treatment centers. DISCUSSION Since current first-line vector intervention methods do not target outdoor transmission and will select for higher insecticide resistance, new methods beyond bed nets and IRS should be considered. Long-lasting microbial larviciding represents a promising new tool that can target both indoor and outdoor transmission and alleviate the problem of pyrethroid resistance. It also has the potential to diminish costs by reducing larvicide reapplications. If successful, it could revolutionize malaria vector control in Africa, just as long-lasting bed nets have done. TRIAL REGISTRATION U.S. National Institute of Health, study ID NCT02392832 . Registered on 3 February 2015.
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Affiliation(s)
- Guofa Zhou
- Program in Public Health, University of California, Irvine, USA
| | - Virginia Wiseman
- School of Public Health & Community Medicine, University of New South Wales, Sydney, Australia
- Department of Global Health and Development, London School of Hygiene & Tropical Medicine, London, UK
| | - Harrysone E. Atieli
- Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya
- Maseno University, Kisumu, Kenya
| | - Ming-Chieh Lee
- Program in Public Health, University of California, Irvine, USA
| | - Andrew K. Githeko
- Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya
| | - Guiyun Yan
- Program in Public Health, University of California, Irvine, USA
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Kiware SS, Corliss G, Merrill S, Lwetoijera DW, Devine G, Majambere S, Killeen GF. Predicting Scenarios for Successful Autodissemination of Pyriproxyfen by Malaria Vectors from Their Resting Sites to Aquatic Habitats; Description and Simulation Analysis of a Field-Parameterizable Model. PLoS One 2015; 10:e0131835. [PMID: 26186730 PMCID: PMC4505906 DOI: 10.1371/journal.pone.0131835] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Accepted: 06/07/2015] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND Large-cage experiments indicate pyriproxifen (PPF) can be transferred from resting sites to aquatic habitats by Anopheles arabiensis--malaria vector mosquitoes to inhibit emergence of their own offspring. PPF coverage is amplified twice: (1) partial coverage of resting sites with PPF contamination results in far higher contamination coverage of adult mosquitoes because they are mobile and use numerous resting sites per gonotrophic cycle, and (2) even greater contamination coverage of aquatic habitats results from accumulation of PPF from multiple oviposition events. METHODS AND FINDINGS Deterministic mathematical models are described that use only field-measurable input parameters and capture the biological processes that mediate PPF autodissemination. Recent successes in large cages can be rationalized, and the plausibility of success under full field conditions can be evaluated a priori. The model also defines measurable properties of PPF delivery prototypes that may be optimized under controlled experimental conditions to maximize chances of success in full field trials. The most obvious flaw in this model is the endogenous relationship that inevitably occurs between the larval habitat coverage and the measured rate of oviposition into those habitats if the target mosquito species is used to mediate PPF transfer. However, this inconsistency also illustrates the potential advantages of using a different, non-target mosquito species for contamination at selected resting sites that shares the same aquatic habitats as the primary target. For autodissemination interventions to eliminate malaria transmission or vector populations during the dry season window of opportunity will require comprehensive contamination of the most challenging subset of aquatic habitats [Formula: see text] that persist or retain PPF activity (Ux) for only one week [Formula: see text], where Ux = 7 days). To achieve >99% contamination coverage of these habitats will necessitate values for the product of the proportional coverage of the ovipositing mosquito population with PPF contamination (CM) by the ovitrap-detectable rates of oviposition by wild mosquitoes into this subset of habitats [Formula: see text], divided by the titre of contaminated mosquitoes required to render them unproductive [Formula: see text], that approximately approach unity [Formula: see text]. CONCLUSIONS The simple multiplicative relationship between CM and [Formula: see text], and the simple exponential decay effect they have upon uncontaminated aquatic habitats, allows application of this model by theoreticians and field biologists alike.
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Affiliation(s)
- Samson S. Kiware
- Environmental Health and Ecological Sciences Thematic Group, Ifakara |Health Institute, P.O. Box 53, Ifakara, Tanzania
- Department of Mathematics, Statistics and Computer Science, Marquette University, Milwaukee, WI, 53201–1881, United States of America
| | - George Corliss
- Department of Mathematics, Statistics and Computer Science, Marquette University, Milwaukee, WI, 53201–1881, United States of America
| | - Stephen Merrill
- Department of Mathematics, Statistics and Computer Science, Marquette University, Milwaukee, WI, 53201–1881, United States of America
| | - Dickson W. Lwetoijera
- Environmental Health and Ecological Sciences Thematic Group, Ifakara |Health Institute, P.O. Box 53, Ifakara, Tanzania
- Liverpool School of Tropical Medicine, Vector Biology Department, Pembroke Place, Liverpool, L3 5QA, United Kingdom
| | - Gregor Devine
- QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | - Silas Majambere
- Environmental Health and Ecological Sciences Thematic Group, Ifakara |Health Institute, P.O. Box 53, Ifakara, Tanzania
- Liverpool School of Tropical Medicine, Vector Biology Department, Pembroke Place, Liverpool, L3 5QA, United Kingdom
| | - Gerry F. Killeen
- Environmental Health and Ecological Sciences Thematic Group, Ifakara |Health Institute, P.O. Box 53, Ifakara, Tanzania
- Liverpool School of Tropical Medicine, Vector Biology Department, Pembroke Place, Liverpool, L3 5QA, United Kingdom
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Sagnon N, Pinder M, Tchicaya EF, Tiono AB, Faragher B, Ranson H, Lindsay SW. To assess whether addition of pyriproxyfen to long-lasting insecticidal mosquito nets increases their durability compared to standard long-lasting insecticidal mosquito nets: study protocol for a randomised controlled trial. Trials 2015; 16:195. [PMID: 25927378 PMCID: PMC4423132 DOI: 10.1186/s13063-015-0700-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Accepted: 04/01/2015] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND The effectiveness of pyrethroid-treated bednets for malaria control in sub-Saharan Africa is under threat because of high levels of resistance to pyrethroid insecticides in the vectors. Here we assess the durability of polyethylene nets with a novel combination of permethrin, a pyrethroid, with pyriproxyfen, an insect juvenile mimic (PPF-LLIN), in comparison with a typical permethrin-treated long-lasting insecticidal net (LLIN). METHODS This is a cluster randomised controlled trial of net durability in Burkina Faso, with clustering at the level of the compound and includes entomological outcome measurements. Half the compounds in each village will be randomly allocated PPF-LLIN and half the LLIN. All sleeping places in a compound will be provided with one type of net. We will distribute the nets at the start of the first transmission season and follow net use at the start and end of each transmission season for 3 years. In one village, bio-efficacy and chemical content will be recorded immediately after net distribution and then at 6, 12, 18, 24, 30 and 36 months. In the other village net survivorship and fabric integrity will be recorded immediately after distribution, and then at 6, 12, 18, 24, 30 and 36 months. Routine measurements of indoor temperature and relative humidity will be made in both villages during the study. Residents will be followed for possible side effects of the PPF-LLIN by surveillance of known asthmatic subjects during the first month post-distribution and pregnancy outcomes will be monitored from antenatal clinic records. DISCUSSION The protocol is novel on two accounts. Firstly, it is the first to describe the procedure for measuring net durability following recent World Health Organisation (WHO) guidelines. Meeting the minimum requirements set in the guidelines is essential before a new type of net can be recommended by WHO's Pesticide Evaluation Scheme (WHOPES). Secondly, it describes methods to monitor the persistence of an active ingredient that reduces vector fertility and fecundity. If the PPF-LLIN is both effective and persistent it will provide an alternative vector control strategy where pyrethroid-resistant vectors are present. TRIAL REGISTRATION ISRCTN30634670 assigned 13 August 2014.
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Affiliation(s)
- N'Fale Sagnon
- Centre National de Recherche et de Formation sur le Paludisme (CNRFP), Ouagadougou, Burkina Faso.
| | - Margaret Pinder
- School of Biological Sciences and Biomedicine, Durham University, Durham, UK.
- Medical Research Council Unit The Gambia, PO Box 273, Banjul, The Gambia.
| | - Emile Fs Tchicaya
- Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, Abidjan, Côte d'Ivoire.
| | - Alfred B Tiono
- Centre National de Recherche et de Formation sur le Paludisme (CNRFP), Ouagadougou, Burkina Faso.
| | | | - Hilary Ranson
- Liverpool School of Tropical Medicine, Liverpool, UK.
| | - Steve W Lindsay
- School of Biological Sciences and Biomedicine, Durham University, Durham, UK.
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Mbare O, Lindsay SW, Fillinger U. Pyriproxyfen for mosquito control: female sterilization or horizontal transfer to oviposition substrates by Anopheles gambiae sensu stricto and Culex quinquefasciatus. Parasit Vectors 2014; 7:280. [PMID: 24954695 PMCID: PMC4082483 DOI: 10.1186/1756-3305-7-280] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 06/16/2014] [Indexed: 11/10/2022] Open
Abstract
Background The use of gravid mosquitoes as vehicles to auto-disseminate larvicides was recently demonstrated for the transfer of pyriproxyfen (PPF) by container-breeding Aedes mosquitoes and presents an appealing idea to explore for other disease vectors. The success of this approach depends on the female’s behaviour, the time of exposure and the amount of PPF that can be carried by an individual. We explore the effect of PPF exposure at seven time points around blood feeding on individual Anopheles gambiae sensu stricto and Culex quinquefasciatus fecundity and ability to transfer in laboratory assays. Method Mosquitoes were exposed to 2.6 mg PPF per m2 at 48, 24 and 0.5 hours before and after a blood meal and on the day of egg-laying. The proportion of exposed females (N = 80-100) laying eggs, the number of eggs laid and hatched was studied. Transfer of PPF to oviposition cups was assessed by introducing 10 late instar insectary-reared An. gambiae s.s. larvae into all the cups and monitored for adult emergence inhibition. Results Exposure to PPF between 24 hours before and after a blood meal had significant sterilizing effects: females of both species were 6 times less likely (Odds ratio (OR) 0.16, 95% confidence interval (CI) 0.10-0.26) to lay eggs than unexposed females. Of the few eggs laid, the odds of an egg hatching was reduced 17 times (OR 0.06, 95% CI 0.04-0.08) in Anopheles but only 1.2 times (OR 0.82, 95% CI 0.73-0.93) in Culex. Adult emergence inhibition from larvae introduced in the oviposition cups was observed only from cups in which eggs were laid. When females were exposed to PPF close to egg laying they transferred enough PPF to reduce emergence by 65-71% (95% CI 62-74%). Conclusion PPF exposure within a day before and after blood feeding affects egg-development in An. gambiae s.s. and Cx. quinquefasciatus and presents a promising opportunity for integrated control of vectors and nuisance mosquitoes. However, sterilized females are unlikely to visit an oviposition site and therefore do not transfer lethal concentrations of PPF to aquatic habitats. This suggests that for successful auto-dissemination the optimum contamination time is close to oviposition.
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Affiliation(s)
| | | | - Ulrike Fillinger
- International Centre of Insect Physiology and Ecology (icipe), Thomas Odhiambo Campus, 40305 Mbita, Kenya.
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