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Wotodjo AN, Doucoure S, Diagne N, Sarr FD, Sokhna C. Malaria epidemics associated with low net use in preadolescent and young adult population in Dielmo (Senegal), a malaria pre-elimination area. Parasit Vectors 2024; 17:74. [PMID: 38374068 PMCID: PMC10877880 DOI: 10.1186/s13071-024-06172-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Accepted: 01/30/2024] [Indexed: 02/21/2024] Open
Abstract
BACKGROUND The epidemic rebounds observed in 2010 and 2013 in Dielmo, a Senegalese village, during a decade (2008-2019) of universal coverage using a long-lasting insecticidal net (LLIN) strategy could have contributed to the resurgence of malaria. Thus, this study was undertaken to understand the implications of net ownership and use on malaria rebound events. METHODS A longitudinal study was carried out in Dielmo with 11 years of LLIN implementation from July 2008 to June 2019 with successive net renewals in 2011, 2014, 2016 and 2019. Quarterly cross-sectional surveys were performed to assess LLIN ownership and use by different age groups in the population. In addition, malaria incidence and transmission were assessed during the study period. RESULTS Ownership of LLINs decreased significantly from 88% in the 1st year of net implementation to 70% during the first malaria upsurge and 72% during the second upsurge while net use decreased significantly from 66% during the 1st year to 58% during the first malaria upsurge and 53% during the second upsurge. Among young adults aged 15-29 years, net use decreased significantly from the 2nd year (51%) of net use to reach 43% during the first malaria upsurge and only 32% use during the second malaria upsurge. During the second malaria upsurge, net use was significantly lower among older children aged 10-14 years old than during the 1st year of net use (p < 0.001). During the first and the second malaria upsurges, the malaria incidence was significantly higher among children aged 10-14 years old (0.4 attacks per person-year) and young adults aged 15-29 years old (0.3 and 0.4 attacks per person, respectively) than during that the 1st year of net implementation (only 0.02 attacks per person-year for 10-14 year olds and 0.04 for 15-29 year olds; p < 0.001). CONCLUSIONS The first malaria upsurge occurred following a progressive decrease in net use after the 2nd year of their implementation with an important increase in malaria incidence among older children while the second malaria upsurge was significantly associated with the decrease of net use among older children and young adults. The regular use of nets in all age groups prevented the occurrence of a third malaria upsurge in Dielmo.
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Affiliation(s)
- Amélé Nyedzie Wotodjo
- UMR VITROME (Vecteurs - Infections Tropicales et Méditerranéennes) Campus International IRD-UCAD, Dakar, Senegal.
| | - Souleymane Doucoure
- UMR VITROME (Vecteurs - Infections Tropicales et Méditerranéennes) Campus International IRD-UCAD, Dakar, Senegal
| | - Nafissatou Diagne
- UMR VITROME (Vecteurs - Infections Tropicales et Méditerranéennes) Campus International IRD-UCAD, Dakar, Senegal
| | | | - Cheikh Sokhna
- UMR VITROME (Vecteurs - Infections Tropicales et Méditerranéennes) Campus International IRD-UCAD, Dakar, Senegal
- Aix-Marseille Univ, IRD, AP-HM, SSA, VITROME, Marseille, France
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Kabera M, Mangala JLN, Soebiyanto R, Mukarugwiro B, Munguti K, Mbituyumuremyi A, Lucchi NW, Hakizimana E. Impact of Pyrethroid Plus Piperonyl Butoxide Synergist-Treated Nets on Malaria Incidence 24 Months after a National Distribution Campaign in Rwanda. Am J Trop Med Hyg 2023; 109:1356-1362. [PMID: 37871590 DOI: 10.4269/ajtmh.23-0317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Accepted: 07/07/2023] [Indexed: 10/25/2023] Open
Abstract
Malaria remains a public health priority in Rwanda. The use of insecticide-treated nets (ITNs) is a key malaria prevention tool. However, expanding pyrethroid resistance threatens the gains made in malaria control. In 2018, the Rwandan malaria program strategic approach included the use of newer types of ITNs such as pyrethroid plus piperonyl butoxide (PBO) synergist-treated nets to counter pyrethroid resistance. In February 2020, 5,892,280 ITNs were distributed countrywide; 1,085,517 of these were PBO nets distributed in five districts. This study was a pragmatic observational study that leveraged the 2020 net distribution and routinely collected confirmed malaria cases to determine the impact of PBO nets 1 and 2 years after ITN distribution. No differences were observed in the average net coverage between the PBO and standard net districts. A significant reduction in malaria incidence was reported in both the PBO (P = 0.019) and two control districts that received standard nets (P = 0.008) 1 year after ITN distribution. However, 2 years after, this reduction was sustained only in the PBO (P = 0.013) and not in the standard net districts (P = 0.685). One year after net distribution, all districts had a significant reduction in malaria incidence rate (incidence rate ratio < 1). In the second year, incidence in districts with PBO nets continued to decrease, whereas in districts with standard nets, incidences were similar to predistribution levels. The results indicate that PBO nets are a promising tool to combat pyrethroid resistance in Rwanda, with protective effects of up to 2 years post distribution.
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Affiliation(s)
- Michee Kabera
- Malaria and Other Parasitic Diseases Division, Rwanda Biomedical Centre, Kigali, Rwanda
| | - Jean-Louis N Mangala
- Malaria and Other Parasitic Diseases Division, Rwanda Biomedical Centre, Kigali, Rwanda
| | - Radina Soebiyanto
- U.S. President's Malaria Initiative, U.S. Agency for International Development (USAID), Washington, District of Columbia
| | | | - Kaendi Munguti
- U.S. President's Malaria Initiative, USAID, Kigali, Rwanda
| | | | - Naomi W Lucchi
- U.S. President's Malaria Initiative, U.S. Centers for Disease Control and Prevention, Kigali, Rwanda
| | - Emmanuel Hakizimana
- Malaria and Other Parasitic Diseases Division, Rwanda Biomedical Centre, Kigali, Rwanda
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Tondossama N, Virgillito C, Coulibaly ZI, Pichler V, Dia I, della Torre A, Touré AO, Adja AM, Caputo B. A High Proportion of Malaria Vector Biting and Resting Indoors despite Extensive LLIN Coverage in Côte d'Ivoire. INSECTS 2023; 14:758. [PMID: 37754726 PMCID: PMC10532360 DOI: 10.3390/insects14090758] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Revised: 08/30/2023] [Accepted: 09/05/2023] [Indexed: 09/28/2023]
Abstract
Malaria is still a leading cause mortality in Côte d'Ivoire despite extensive LLINs coverage. We present the results of an entomological survey conducted in a coastal and in an inland village with the aim to estimate Anopheles gambiae sensu lato (s.l.) female's abundance indoor/outdoor and Plasmodium falciparum infection rate and analyze the occurrence of blood-feeding in relation to LLINs use. Pyrethrum spray (PSC) and window exit traps (WT) collections were carried out to target endophagic/endophilic and endophagic/exophilic females, respectively. Data on LLINs use in sampled houses were collected. (1) high levels of malaria transmission despite LLINs coverage >70% (~1 An. gambiae s.l. predicted mean/person/night and ~5% Plasmodium falciparum infection rate); (2) 46% of females in the PSC sample were blood-fed, suggesting that they fed on an unprotected host inside the house; (3) 81% of females in WT were unfed, suggesting that they were leaving the house to find an available host. Model estimates that if everyone sleeps under LLINs the probability for a mosquito to bite decreases of 48% and 95% in the coastal and inland village, respectively. The results show a high proportion of mosquito biting and resting indoors despite extensive LLINs. The biological/epidemiological determinants of accounting for these results merit deeper investigations.
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Affiliation(s)
- Naminata Tondossama
- Entomology and Herpetology Unit, Institut Pasteur de Côte d’Ivoire, Abidjan 01 PB 490, Côte d’Ivoire; (N.T.); (Z.I.C.)
- Laboratoire de Biologie et Santé, UFR Biosciences, Université Félix Houphouët Boigny Cocody, Abidjan 01 BP V34, Côte d’Ivoire;
| | - Chiara Virgillito
- Department of Public Health and Infectious Diseases, Institute Pasteur Italia-Fondazione Cenci-Bolognetti, University of Rome ‘Sapienza’, Piazzale Aldo Moro 5, 00185 Rome, Italy; (C.V.)
| | - Zanakoungo Ibrahima Coulibaly
- Entomology and Herpetology Unit, Institut Pasteur de Côte d’Ivoire, Abidjan 01 PB 490, Côte d’Ivoire; (N.T.); (Z.I.C.)
| | - Verena Pichler
- Department of Public Health and Infectious Diseases, Institute Pasteur Italia-Fondazione Cenci-Bolognetti, University of Rome ‘Sapienza’, Piazzale Aldo Moro 5, 00185 Rome, Italy; (C.V.)
| | - Ibrahima Dia
- Pôle de Zoologie Médicale, Institut Pasteur de Dakar, 36 Avenue Pasteur, Dakar BP 220, Senegal;
| | - Alessandra della Torre
- Department of Public Health and Infectious Diseases, Institute Pasteur Italia-Fondazione Cenci-Bolognetti, University of Rome ‘Sapienza’, Piazzale Aldo Moro 5, 00185 Rome, Italy; (C.V.)
| | - Andre Offianan Touré
- Unité de Paludologie, Institut Pasteur de Côte d’Ivoire, Abidjan 01 PB 490, Côte d’Ivoire;
| | - Akré Maurice Adja
- Laboratoire de Biologie et Santé, UFR Biosciences, Université Félix Houphouët Boigny Cocody, Abidjan 01 BP V34, Côte d’Ivoire;
- Institut Pierre Richet, Institut National de Santé Publique, Bouaké 01 BP 1500, Côte d’Ivoire
| | - Beniamino Caputo
- Department of Public Health and Infectious Diseases, Institute Pasteur Italia-Fondazione Cenci-Bolognetti, University of Rome ‘Sapienza’, Piazzale Aldo Moro 5, 00185 Rome, Italy; (C.V.)
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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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Syme T, N'dombidjé B, Gbegbo M, Todjinou D, Ariori V, De Vos P, Pigeon O, Ngufor C. PermaNet Dual, a new deltamethrin-chlorfenapyr mixture net, shows improved efficacy against pyrethroid-resistant Anopheles gambiae sensu lato in southern Benin. Sci Rep 2023; 13:12232. [PMID: 37507423 PMCID: PMC10382523 DOI: 10.1038/s41598-023-39140-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 07/20/2023] [Indexed: 07/30/2023] Open
Abstract
Pyrethroid-chlorfenapyr nets have demonstrated improved entomological and epidemiological impact in trials across Africa. This is driving increased demand for this novel net class in malaria-endemic countries. PermaNet Dual is a new deltamethrin-chlorfenapyr net developed by Vestergaard Sàrl to provide more options to malaria control programmes. We performed an experimental hut trial to evaluate the efficacy of PermaNet Dual against wild, free-flying pyrethroid-resistant Anopheles gambiae sensu lato in Covè, Benin. PermaNet Dual induced superior levels of mosquito mortality compared to a pyrethroid-only net and a pyrethroid-piperonyl butoxide net both when unwashed (77% with PermaNet Dual vs. 23% with PermaNet 2.0 and 56% with PermaNet 3.0, p < 0.001) and after 20 standardised washes (75% with PermaNet Dual vs. 14% with PermaNet 2.0 and 30% with PermaNet 3.0, p < 0.001). Using a provisional non-inferiority margin defined by the World Health Organisation, PermaNet Dual was also non-inferior to a pyrethroid-chlorfenapyr net that has demonstrated improved public health value (Interceptor G2), for vector mortality (79% vs. 76%, OR = 0.878, 95% CIs 0.719-1.073) but not for blood-feeding protection (35% vs. 26%, OR = 1.424, 95% CIs 1.177-1.723). PermaNet Dual presents an additional option of this highly effective net class for improved control of malaria transmitted by pyrethroid-resistant mosquitoes.
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Affiliation(s)
- Thomas Syme
- London School of Hygiene & Tropical Medicine, London, UK.
- Centre de Recherche Entomologique de Cotonou, Cotonou, Benin.
- Pan African Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin.
| | - Boris N'dombidjé
- Centre de Recherche Entomologique de Cotonou, Cotonou, Benin
- Pan African Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
| | - Martial Gbegbo
- Centre de Recherche Entomologique de Cotonou, Cotonou, Benin
- Pan African Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
| | - Damien Todjinou
- Centre de Recherche Entomologique de Cotonou, Cotonou, Benin
- Pan African Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
| | - Victoria Ariori
- Centre de Recherche Entomologique de Cotonou, Cotonou, Benin
- Pan African Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin
| | - Patricia De Vos
- Centre Walloon de Recherches Agronomiques (CRA-W), Gembloux, Belgium
| | - Olivier Pigeon
- Centre Walloon de Recherches Agronomiques (CRA-W), Gembloux, Belgium
| | - Corine Ngufor
- London School of Hygiene & Tropical Medicine, London, UK.
- Centre de Recherche Entomologique de Cotonou, Cotonou, Benin.
- Pan African Malaria Vector Research Consortium (PAMVERC), Cotonou, Benin.
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Adoha CJ, Sovi A, Yovogan B, Akinro B, Accrombessi M, Dangbénon E, Odjo EM, Sagbohan HW, Kpanou CD, Padonou GG, Messenger LA, Agbangla C, Ngufor C, Cook J, Protopopoff N, Akogbéto MC. Efficacy of Pyrethroid-Pyriproxyfen and Pyrethroid-Chlorfenapyr Long-Lasting Insecticidal Nets (LLINs) for the Control of Non- Anopheles Mosquitoes: Secondary Analysis from a Cluster Randomised Controlled Trial (cRCT). INSECTS 2023; 14:417. [PMID: 37233045 PMCID: PMC10231081 DOI: 10.3390/insects14050417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Revised: 04/21/2023] [Accepted: 04/26/2023] [Indexed: 05/27/2023]
Abstract
The efficacy of a vector control tool in reducing mosquito biting is crucial for its acceptability. The present study compared the vector density of Culex spp. And Mansonia spp. across clusters, which received two dual-active ingredient (a.i.) long-lasting insecticidal nets (LLINs) and a standard pyrethroid-only LLIN, and assessed the seasonality of these mosquito genera. A total of 85,723 Culex spp. and 144,025 Mansonia spp. were caught over the study period. The density of Culex and Mansonia was reduced in all three arms over the study period. There was no evidence of a significant reduction in the indoor or outdoor density of Culex spp. in either dual-a.i. LLIN arm as compared to the standard pyrethroid-only net arm. A similar trend was observed with Mansonia spp. A high density of Culex spp. was found both in rainy and dry seasons, while for Mansonia spp., this was mainly observed during the rainy season. These results suggest that the novel insecticides in the dual-a.i. LLINs did not have an additional impact on these species and that pyrethroids might still be effective on them. Further work is required to determine whether these species of mosquitoes have resistance to the insecticides tested in this trial.
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Affiliation(s)
- Constantin J. Adoha
- Faculté des Sciences et Techniques, Université d’Abomey-Calavi, Abomey-Calavi 01 BP 526, Benin; (B.Y.); (E.M.O.); (H.W.S.); (G.G.P.)
- Centre de Recherche Entomologique de Cotonou, Cotonou 06 BP 2604, Benin; (B.A.); (C.D.K.); (C.N.); (M.C.A.)
| | - Arthur Sovi
- Centre de Recherche Entomologique de Cotonou, Cotonou 06 BP 2604, Benin; (B.A.); (C.D.K.); (C.N.); (M.C.A.)
- Faculty of Infectious and Tropical Diseases, Disease Control Department, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK (N.P.)
- Faculté d’Agronomie, Université de Parakou, Parakou BP 123, Benin
| | - Boulais Yovogan
- Faculté des Sciences et Techniques, Université d’Abomey-Calavi, Abomey-Calavi 01 BP 526, Benin; (B.Y.); (E.M.O.); (H.W.S.); (G.G.P.)
- Centre de Recherche Entomologique de Cotonou, Cotonou 06 BP 2604, Benin; (B.A.); (C.D.K.); (C.N.); (M.C.A.)
| | - Bruno Akinro
- Centre de Recherche Entomologique de Cotonou, Cotonou 06 BP 2604, Benin; (B.A.); (C.D.K.); (C.N.); (M.C.A.)
| | - Manfred Accrombessi
- Faculty of Infectious and Tropical Diseases, Disease Control Department, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK (N.P.)
| | - Edouard Dangbénon
- Centre de Recherche Entomologique de Cotonou, Cotonou 06 BP 2604, Benin; (B.A.); (C.D.K.); (C.N.); (M.C.A.)
| | - Esdras M. Odjo
- Faculté des Sciences et Techniques, Université d’Abomey-Calavi, Abomey-Calavi 01 BP 526, Benin; (B.Y.); (E.M.O.); (H.W.S.); (G.G.P.)
- Centre de Recherche Entomologique de Cotonou, Cotonou 06 BP 2604, Benin; (B.A.); (C.D.K.); (C.N.); (M.C.A.)
| | - Hermann Watson Sagbohan
- Faculté des Sciences et Techniques, Université d’Abomey-Calavi, Abomey-Calavi 01 BP 526, Benin; (B.Y.); (E.M.O.); (H.W.S.); (G.G.P.)
- Centre de Recherche Entomologique de Cotonou, Cotonou 06 BP 2604, Benin; (B.A.); (C.D.K.); (C.N.); (M.C.A.)
| | - Casimir Dossou Kpanou
- Centre de Recherche Entomologique de Cotonou, Cotonou 06 BP 2604, Benin; (B.A.); (C.D.K.); (C.N.); (M.C.A.)
| | - Gil G. Padonou
- Faculté des Sciences et Techniques, Université d’Abomey-Calavi, Abomey-Calavi 01 BP 526, Benin; (B.Y.); (E.M.O.); (H.W.S.); (G.G.P.)
- Centre de Recherche Entomologique de Cotonou, Cotonou 06 BP 2604, Benin; (B.A.); (C.D.K.); (C.N.); (M.C.A.)
| | - Louisa A. Messenger
- Faculty of Infectious and Tropical Diseases, Disease Control Department, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK (N.P.)
- Department of Environmental and Occupational Health, School of Public Health, University of Nevada, Las Vegas, NV 89154, USA
| | - Clément Agbangla
- Faculté des Sciences et Techniques, Université d’Abomey-Calavi, Abomey-Calavi 01 BP 526, Benin; (B.Y.); (E.M.O.); (H.W.S.); (G.G.P.)
| | - Corine Ngufor
- Centre de Recherche Entomologique de Cotonou, Cotonou 06 BP 2604, Benin; (B.A.); (C.D.K.); (C.N.); (M.C.A.)
- Faculty of Infectious and Tropical Diseases, Disease Control Department, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK (N.P.)
| | - Jackie Cook
- Medical Research Council (MRC) International Statistics and Epidemiology Group, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK
| | - Natacha Protopopoff
- Faculty of Infectious and Tropical Diseases, Disease Control Department, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK (N.P.)
| | - Martin C. Akogbéto
- Centre de Recherche Entomologique de Cotonou, Cotonou 06 BP 2604, Benin; (B.A.); (C.D.K.); (C.N.); (M.C.A.)
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Hobbs NP, Weetman D, Hastings IM. Insecticide resistance management strategies for public health control of mosquitoes exhibiting polygenic resistance: A comparison of sequences, rotations, and mixtures. Evol Appl 2023; 16:936-959. [PMID: 37124088 PMCID: PMC10130562 DOI: 10.1111/eva.13546] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 02/22/2023] [Accepted: 03/21/2023] [Indexed: 05/02/2023] Open
Abstract
Malaria control uses insecticides to kill Anopheles mosquitoes. Recent successes in malaria control are threatened by increasing levels of insecticide resistance (IR), requiring insecticide resistance management (IRM) strategies to mitigate this problem. Field trials of IRM strategies are usually prohibitively expensive with long timeframes, and mathematical modeling is often used to evaluate alternative options. Previous IRM models in the context of malaria control assumed IR to have a simple (monogenic) basis, whereas in natural populations, IR will often be a complex polygenic trait determined by multiple genetic variants. A quantitative genetics model was developed to model IR as a polygenic trait. The model allows insecticides to be deployed as sequences (continuous deployment until a defined withdrawal threshold, termed "insecticide lifespan", as indicated by resistance diagnosis in bioassays), rotations (periodic switching of insecticides), or full-dose mixtures (two insecticides in one formulation). These IRM strategies were compared based on their "strategy lifespan" (capped at 500 generations). Partial rank correlation and generalized linear modeling was used to identify and quantify parameters driving the evolution of resistance. Random forest models were used to identify parameters offering predictive value for decision-making. Deploying single insecticides as sequences or rotations usually made little overall difference to their "strategy lifespan", though rotations displayed lower mean and peak resistances. Deploying two insecticides in a full-dose mixture formulation was found to extend the "strategy lifespan" when compared to deploying each in sequence or rotation. This pattern was observed regardless of the level of cross resistance between the insecticides or the starting level of resistance. Statistical analysis highlighted the importance of insecticide coverage, cross resistance, heritability, and fitness costs for selecting an appropriate IRM strategy. Full-dose mixtures appear the most promising of the strategies evaluated, with the longest "strategy lifespans". These conclusions broadly corroborate previous results from monogenic models.
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Affiliation(s)
- Neil Philip Hobbs
- Department of Vector BiologyLiverpool School of Tropical MedicinePembroke PlaceLiverpoolL3 5QAUK
| | - David Weetman
- Department of Vector BiologyLiverpool School of Tropical MedicinePembroke PlaceLiverpoolL3 5QAUK
| | - Ian Michael Hastings
- Department of Tropical Disease BiologyLiverpool School of Tropical MedicinePembroke PlaceLiverpoolL3 5QAUK
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Efa S, Elanga-Ndille E, Poumachu Y, Tene B, Mikande JZ, Zakariaou N, Wondji CS, Ndo C. Insecticide Resistance Profile and Mechanisms in An. gambiae s.l. from Ebolowa, South Cameroon. INSECTS 2022; 13:1133. [PMID: 36555042 PMCID: PMC9785700 DOI: 10.3390/insects13121133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 11/25/2022] [Accepted: 11/30/2022] [Indexed: 06/17/2023]
Abstract
Monitoring the trend of insecticide resistance and understanding associated genetic mechanisms is important for designing efficient malaria vector control strategies. This study was conducted to provide temporal data on insecticide resistance status and mechanisms in the major malaria vector Anopheles gambiae s.l. from Ebolowa, Southern Cameroon. Methods: Larvae of An. gambiae s.l. were collected from typical breeding sites throughout the city and reared to adulthood. Emerging adults were morphologically identified and WHO tube assays were performed to determine their susceptibility to carbamate, organophosphate and pyrethroid insecticides at diagnostic doses. When resistance was observed, its intensity was determined by performing WHO tube tests using 5 and 10 times the concentration of the diagnostic dose. Metabolic resistance mechanisms were investigated using insecticide-synergist assays. Sibling species of the An. gambiae complex were identified using SINE-PCR protocol. TaqMan assay was used to genotype the L1014F and L1014S kdr mutations, and the N1575Y mutation, an amplifier of the resistance conferred by the L1014F mutation. Results: Anopheles coluzzii was by far the dominant (99%) member of the An. gambiae s.l. complex in Ebolowa. The species was fully susceptible to carbamates and organophosphates, but resistant to all pyrethroid insecticides tested. Resistance was of moderate intensity for deltamethrin (mortality: 37%, 70% and 99% for 1×, 5× and 10× insecticide concentration, respectively) but rather of high intensity for permethrin (5% for 1×; 62% for 5× and 75% for 10×) and for alphacypermethrin (4.4% for 1×; 57% for 5× and 80% for 10×). Pre-exposure to the synergist PBO resulted in a full recovery of the susceptibility to delthametrin, but this was not observed for the other two pyrethroids tested. L1014S (kdr-East) and the N1575Y mutations were absent, whereas the L1014F (kdr-West) mutation was present at a high frequency (75%), showing a significant association with resistance to permethrin (OR = 3.8; 95%; CI [1.9−7.4]; p < 0.0001) and alphacypermethrin (OR = 3; 95%; CI [1.6−5.4]; p = 0.0002). Conclusion: The increased resistance of An. gambiae s.l. to pyrethroid insecticides as observed in Ebolowa poses a threat to the efficacy of LLINs used to protect populations from the bites of Anopheles mosquitoes that transmit malaria parasites. The present study further highlights the urgent need to implement resistance management strategies in order to maintain the effectiveness of insecticide-based vector control interventions and prevent a rebound in malaria-related mortality.
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Affiliation(s)
- Salomon Efa
- Department of Medical Entomology, Centre for Research in Infectious Diseases (CRID), Yaoundé P.O. Box 13591, Cameroon
- Faculty of Sciences, University of Yaoundé I, Yaoundé P.O. Box 337, Cameroon
| | - Emmanuel Elanga-Ndille
- Department of Medical Entomology, Centre for Research in Infectious Diseases (CRID), Yaoundé P.O. Box 13591, Cameroon
- Vector Borne Parasitic and Infectious Diseases Unit of the Laboratory of Applied Biology and Ecology (VBID-LABEA), Department of Animal Biology, Faculty of Sciences, University of Dschang, Dschang P.O. Box 067, Cameroon
| | - Yacouba Poumachu
- Vector Borne Parasitic and Infectious Diseases Unit of the Laboratory of Applied Biology and Ecology (VBID-LABEA), Department of Animal Biology, Faculty of Sciences, University of Dschang, Dschang P.O. Box 067, Cameroon
| | - Billy Tene
- Department of Medical Entomology, Centre for Research in Infectious Diseases (CRID), Yaoundé P.O. Box 13591, Cameroon
| | - Jacqueline Ze Mikande
- Department of Anesthesia and Reanimation, Faculty of Medicine and Biomedical Sciences, University of Yaoundé I, Yaoundé P.O Box 1364, Cameroon
| | - Njoumémi Zakariaou
- Department of Anesthesia and Reanimation, Faculty of Medicine and Biomedical Sciences, University of Yaoundé I, Yaoundé P.O Box 1364, Cameroon
| | - Charles S. Wondji
- Department of Medical Entomology, Centre for Research in Infectious Diseases (CRID), Yaoundé P.O. Box 13591, Cameroon
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
| | - Cyrille Ndo
- Department of Medical Entomology, Centre for Research in Infectious Diseases (CRID), Yaoundé P.O. Box 13591, Cameroon
- Faculty of Medicine and Pharmaceutical Sciences, University of Douala, Douala P.O. Box 2701, Cameroon
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Govoetchan R, Fongnikin A, Syme T, Small G, Gbegbo M, Todjinou D, Rowland M, Nimmo D, Padonou GG, Ngufor C. VECTRON™ T500, a new broflanilide insecticide for indoor residual spraying, provides prolonged control of pyrethroid-resistant malaria vectors. Malar J 2022; 21:324. [DOI: 10.1186/s12936-022-04336-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Accepted: 10/26/2022] [Indexed: 11/13/2022] Open
Abstract
Abstract
Background
Broflanilide is a newly discovered insecticide with a novel mode of action targeting insect γ-aminobutyric acid receptors. The efficacy of VECTRON™ T500, a wettable powder formulation of broflanilide, was assessed for IRS against wild pyrethroid-resistant malaria vectors in experimental huts in Benin.
Methods
VECTRON™ T500 was evaluated at 100 mg/m2 in mud and cement-walled experimental huts against wild pyrethroid-resistant Anopheles gambiae sensu lato (s.l.) in Covè, southern Benin, over 18 months. A direct comparison was made with Actellic® 300CS, a WHO-recommended micro-encapsulated formulation of pirimiphos-methyl, applied at 1000 mg/m2. The vector population at Covè was investigated for susceptibility to broflanilide and other classes of insecticides used for vector control. Monthly wall cone bioassays were performed to assess the residual efficacy of VECTRON™ T500 using insecticide susceptible An. gambiae Kisumu and pyrethroid-resistant An. gambiae s.l. Covè strains. The study complied with OECD principles of good laboratory practice.
Results
The vector population at Covè was resistant to pyrethroids and organochlorines but susceptible to broflanilide and pirimiphos-methyl. A total of 23,171 free-flying wild pyrethroid-resistant female An. gambiae s.l. were collected in the experimental huts over 12 months. VECTRON™ T500 induced 56%-60% mortality in wild vector mosquitoes in both cement and mud-walled huts. Mortality with VECTRON™ T500 was 62%-73% in the first three months and remained > 50% for 9 months on both substrate-types. By comparison, mortality with Actellic® 300CS was very high in the first three months (72%-95%) but declined sharply to < 40% after 4 months. Using a non-inferiority margin defined by the World Health Organization, overall mortality achieved with VECTRON™ T500 was non-inferior to that observed in huts treated with Actellic® 300CS with both cement and mud wall substrates. Monthly in situ wall cone bioassay mortality with VECTRON™ T500 also remained over 80% for 18 months but dropped below 80% with Actellic® 300CS at 6–7 months post spraying.
Conclusion
VECTRON™ T500 shows potential to provide substantial and prolonged control of malaria transmitted by pyrethroid-resistant mosquito vectors when applied for IRS. Its addition to the current list of WHO-approved IRS insecticides will provide a suitable option to facilitate rotation of IRS products with different modes of action.
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Urio NH, Pinda PG, Ngonzi AJ, Muyaga LL, Msugupakulya BJ, Finda M, Matanila GS, Mponzi W, Ngowo HS, Kahamba NF, Nkya TE, Okumu FO. Effects of agricultural pesticides on the susceptibility and fitness of malaria vectors in rural south-eastern Tanzania. Parasit Vectors 2022; 15:213. [PMID: 35710443 PMCID: PMC9204902 DOI: 10.1186/s13071-022-05318-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2022] [Accepted: 05/03/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Agricultural pesticides may exert strong selection pressures on malaria vectors during the aquatic life stages and may contribute to resistance in adult mosquitoes. This could reduce the performance of key vector control interventions such as indoor-residual spraying and insecticide-treated nets. The aim of this study was to investigate effects of agrochemicals on susceptibility and fitness of the malaria vectors across farming areas in Tanzania. METHODS An exploratory mixed-methods study was conducted to assess pesticide use in four villages (V1-V4) in south-eastern Tanzania. Anopheles gambiae (s.l.) larvae were collected from agricultural fields in the same villages and their emergent adults examined for insecticide susceptibility, egg-laying and wing lengths (as proxy for body size). These tests were repeated using two groups of laboratory-reared An. arabiensis, one of which was pre-exposed for 48 h to sub-lethal aquatic doses of agricultural pesticides found in the villages. RESULTS Farmers lacked awareness about the linkages between the public health and agriculture sectors but were interested in being more informed. Agrochemical usage was reported as extensive in V1, V2 and V3 but minimal in V4. Similarly, mosquitoes from V1 to V3 but not V4 were resistant to pyrethroids and either pirimiphos-methyl or bendiocarb, or both. Adding the synergist piperonyl butoxide restored potency of the pyrethroids. Pre-exposure of laboratory-reared mosquitoes to pesticides during aquatic stages did not affect insecticide susceptibility in emergent adults of the same filial generation. There was also no effect on fecundity, except after pre-exposure to organophosphates, which were associated with fewer eggs and smaller mosquitoes. Wild mosquitoes were smaller than laboratory-reared ones, but fecundity was similar. CONCLUSIONS Safeguarding the potential of insecticide-based interventions requires improved understanding of how agricultural pesticides influence important life cycle processes and transmission potential of mosquito vectors. In this study, susceptibility of mosquitoes to public health insecticides was lower in villages reporting frequent use of pesticides compared to villages with little or no pesticide use. Variations in the fitness parameters, fecundity and wing length marginally reflected the differences in exposure to agrochemicals and should be investigated further. Pesticide use may exert additional life cycle constraints on mosquito vectors, but this likely occurs after multi-generational exposures.
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Affiliation(s)
- Naomi H. Urio
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
- School of Life Science and Bioengineering, The Nelson Mandela African Institute of Science and Technology, P.O. Box 447, Arusha, Tanzania
| | - Polius G. Pinda
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
- School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Amos J. Ngonzi
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
- School of Life Science and Bioengineering, The Nelson Mandela African Institute of Science and Technology, P.O. Box 447, Arusha, Tanzania
| | - Letus L. Muyaga
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Betwel J. Msugupakulya
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Marceline Finda
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
- School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Godfrey S. Matanila
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Winifrida Mponzi
- 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
- Institute of Biodiversity, Animal Health, and Comparative Medicine, University of Glasgow, G12 8QQ Glasgow, Scotland
| | - Najat F. Kahamba
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
- Institute of Biodiversity, Animal Health, and Comparative Medicine, University of Glasgow, G12 8QQ Glasgow, Scotland
| | - Theresia E. Nkya
- International Centre of Insect Physiology and Ecology, Nairobi, Kenya
- University of Dar es Salaam, Mbeya Health and Allied Sciences, Mbeya, Tanzania
| | - Fredros O. Okumu
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
- School of Life Science and Bioengineering, The Nelson Mandela African Institute of Science and Technology, P.O. Box 447, Arusha, Tanzania
- School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
- Institute of Biodiversity, Animal Health, and Comparative Medicine, University of Glasgow, G12 8QQ Glasgow, Scotland
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Martin JL, Messenger LA, Mosha FW, Lukole E, Mosha JF, Kulkarni M, Churcher TS, Sherrard-Smith E, Manjurano A, Protopopoff N, Rowland M. Durability of three types of dual active ingredient long-lasting insecticidal net compared to a pyrethroid-only LLIN in Tanzania: methodology for a prospective cohort study nested in a cluster randomized controlled trial. Malar J 2022; 21:96. [PMID: 35305667 PMCID: PMC8934498 DOI: 10.1186/s12936-022-04119-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 03/05/2022] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND Progress achieved by long-lasting insecticidal nets (LLINs) against malaria is threatened by widespread selection of pyrethroid resistance among vector populations. LLINs with non-pyrethroid insecticides are urgently needed. This study aims to assess the insecticide and textile durability of three classes of dual-active ingredient (A.I.) LLINs using techniques derived from established WHO LLIN testing methods to set new standards of evaluation. METHODS A WHO Phase 3 active ingredients and textile durability study will be carried out within a cluster randomized controlled trial in 40 clusters in Misungwi district, Tanzania. The following treatments will be evaluated: (1) Interceptor®G2 combining chlorfenapyr and the pyrethroid alpha-cypermethrin, (2) Royal Guard® treated with pyriproxyfen and alpha-cypermethrin, (3) Olyset™ Plus which incorporates a synergist piperonyl butoxide and the pyrethroid permethrin, and (4) a reference standard alpha-cypermethrin only LLIN (Interceptor®). 750 nets will be followed in 5 clusters per intervention arm at 6, 12, 24 and 36 months post distribution for survivorship and hole index assessment. A second cohort of 1950 nets per net type will be identified in 10 clusters, of which 30 LLINs will be withdrawn for bio-efficacy and chemical analysis every 6 months up to 36 months and another 30 collected for experimental hut trials every year. Bio-efficacy will be assessed using cone bioassays and tunnel tests against susceptible and resistant laboratory strains of Anopheles gambiae sensu stricto. Efficacy of field-collected nets will be compared in six experimental huts. The main outcomes will be Anopheles mortality up to 72 h post exposure, blood feeding and egg maturation using ovary dissection to assess impact on fecundity. CONCLUSIONS Study findings will help develop bio-efficacy and physical durability criteria for partner A.I., in relation to the cRCT epidemiological and entomological outcomes, and refine preferred product characteristics of each class of LLIN. If suitable, the bioassay and hut outcomes will be fitted to transmission models to estimate correlation with cRCT outcomes. TRIAL REGISTRATION NUMBER NCT03554616.
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Affiliation(s)
- Jackline L. Martin
- Kilimanjaro Christian Medical University College, Moshi, United Republic of Tanzania
- National Institute for Medical Research-Mwanza Center, Mwanza, United Republic of Tanzania
| | | | - Franklin W. Mosha
- Kilimanjaro Christian Medical University College, Moshi, United Republic of Tanzania
| | - Eliud Lukole
- National Institute for Medical Research-Mwanza Center, Mwanza, United Republic of Tanzania
| | - Jacklin F. Mosha
- National Institute for Medical Research-Mwanza Center, Mwanza, United Republic of Tanzania
| | | | | | | | - Alphaxard Manjurano
- National Institute for Medical Research-Mwanza Center, Mwanza, United Republic of Tanzania
| | | | - Mark Rowland
- London School of Hygiene and Tropical, London, UK
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Mechan F, Katureebe A, Tuhaise V, Mugote M, Oruni A, Onyige I, Bumali K, Thornton J, Maxwell K, Kyohere M, Kamya MR, Mutungi P, Kigozi SP, Yeka A, Opigo J, Maiteki-Sebuguzi C, Gonahasa S, Hemingway J, Dorsey G, Reimer LJ, Staedke SG, Donnelly MJ, Lynd A. LLIN evaluation in Uganda project (LLINEUP): The fabric integrity, chemical content and bioefficacy of long-lasting insecticidal nets treated with and without piperonyl butoxide across two years of operational use in Uganda. CURRENT RESEARCH IN PARASITOLOGY & VECTOR-BORNE DISEASES 2022; 2:100092. [PMID: 35734077 PMCID: PMC9207544 DOI: 10.1016/j.crpvbd.2022.100092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 05/06/2022] [Accepted: 05/18/2022] [Indexed: 11/28/2022]
Abstract
Long-lasting insecticidal nets (LLINs) supplemented with the synergist piperonyl butoxide have been developed in response to growing pyrethroid resistance; however, their durability in the field remains poorly described. A pragmatic cluster-randomised trial was embedded into Ugandaʼs 2017–2018 LLIN distribution to compare the durability of LLINs with and without PBO. A total of 104 clusters (health sub-districts) were included with each receiving one of four LLIN products, two with pyrethroid + PBO (Olyset Plus and PermaNet 3.0) and two pyrethroid-only (Olyset Net and PermaNet 2.0). Nets were sampled at baseline, 12 and 25 months post-distribution to assess physical condition, chemical content, and bioefficacy. Physical condition was quantified using proportionate Hole Index and chemical content measured using high-performance liquid chromatography. Bioefficacy was assessed with three-minute World Health Organisation (WHO) Cone and Wireball assays using pyrethroid-resistant Anopheles gambiae, with 1-h knockdown and 24-h mortality recorded. There was no difference in physical durability between LLIN products assessed (P = 0.644). The pyrethroid content of all products remained relatively stable across time-points but PBO content declined by 55% (P < 0.001) and 58% (P < 0.001) for Olyset Plus and PermaNet 3.0 respectively. Both PBO LLINs were highly effective against pyrethroid-resistant mosquitoes when new, knocking down all mosquitoes. However, bioefficacy declined over time with Olyset Plus knocking down 45.72% (95% CI: 22.84–68.62%, P = 0.021) and Permanent 3.0 knocking down 78.57% (95% CI: 63.57–93.58%, P < 0.001) after 25 months. Here we demonstrate that both Olyset Plus and PermaNet 3.0 are as durable as their pyrethroid-only equivalents and had superior bioefficacy against pyrethroid-resistant An. gambiae. However, the superiority of PBO-LLINs decreased with operational use, correlating with a reduction in total PBO content. This decline in bioefficacy after just two years is concerning and there is an urgent need to assess the durability of PBO LLINs in other settings. Olyset Plus and PermaNet 3.0 nets effective against pyrethroid-resistant Anopheles gambiae when new. Killing effect of both nets halved after two years. Nets in ‘traditional’ thatched-roof housing at high risk of damage.
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Affiliation(s)
- Frank Mechan
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
- Corresponding author.
| | | | | | | | - Ambrose Oruni
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
| | | | | | - Jonathan Thornton
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Kilama Maxwell
- Department of Medicine, Makerere University, Kampala, Uganda
| | - Mary Kyohere
- Department of Medicine, Makerere University, Kampala, Uganda
| | - Moses R. Kamya
- Infectious Diseases Research Collaboration, Uganda
- Makerere University - Johns Hopkins University (MUJHU) Research Collaboration, Kampala, Uganda
| | | | | | - Adoke Yeka
- Infectious Diseases Research Collaboration, Uganda
| | - Jimmy Opigo
- National Malaria Control Division, Ministry of Health, Kampala, Uganda
| | | | | | - Janet Hemingway
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Grant Dorsey
- Department of Medicine, University of California, San Francisco, USA
| | - Lisa J. Reimer
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Sarah G. Staedke
- Infectious Diseases Research Collaboration, Uganda
- Department of Clinical Research, London School of Hygiene & Tropical Medicine, London, UK
| | - Martin J. Donnelly
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Amy Lynd
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
- Corresponding author.
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Gichuki PM, Kamau L, Njagi K, Karoki S, Muigai N, Matoke-Muhia D, Bayoh N, Mathenge E, Yadav RS. Bioefficacy and durability of Olyset ® Plus, a permethrin and piperonyl butoxide-treated insecticidal net in a 3-year long trial in Kenya. Infect Dis Poverty 2021; 10:135. [PMID: 34930459 PMCID: PMC8691082 DOI: 10.1186/s40249-021-00916-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2021] [Accepted: 11/01/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Long-lasting insecticide nets (LLINs) are a core malaria intervention. LLINs should retain efficacy against mosquito vectors for a minimum of three years. Efficacy and durability of Olyset® Plus, a permethrin and piperonyl butoxide (PBO) treated LLIN, was evaluated versus permethrin treated Olyset® Net. In the absence of WHO guidelines of how to evaluate PBO nets, and considering the manufacturer's product claim, Olyset® Plus was evaluated as a pyrethroid LLIN. METHODS This was a household randomized controlled trial in a malaria endemic rice cultivation zone of Kirinyaga County, Kenya between 2014 and 2017. Cone bioassays and tunnel tests were done against Anopheles gambiae Kisumu. The chemical content, fabric integrity and LLIN survivorship were monitored. Comparisons between nets were tested for significance using the Chi-square test. Exact binomial distribution with 95% confidence intervals (95% CI) was used for percentages. The WHO efficacy criteria used were ≥ 95% knockdown and/or ≥ 80% mortality rate in cone bioassays and ≥ 80% mortality and/or ≥ 90% blood-feeding inhibition in tunnel tests. RESULTS At 36 months, Olyset® Plus lost 52% permethrin and 87% PBO content; Olyset® Net lost 24% permethrin. Over 80% of Olyset® Plus and Olyset® Net passed the WHO efficacy criteria for LLINs up to 18 and 12 months, respectively. At month 36, 91.2% Olyset® Plus and 86.4% Olyset® Net survived, while 72% and 63% developed at least one hole. The proportionate Hole Index (pHI) values representing nets in good, serviceable and torn condition were 49.6%, 27.1% and 23.2%, respectively for Olyset® Plus, and 44.9%, 32.8% and 22.2%, respectively for Olyset® Net but were not significantly different. CONCLUSIONS Olyset® Plus retained efficacy above or close to the WHO efficacy criteria for about 2 years than Olyset® Net (1-1.5 years). Both nets did not meet the 3-year WHO efficacy criteria, and showed little attrition, comparable physical durability and survivorship, with 50% of Olyset® Plus having good and serviceable condition after 3 years. Better community education on appropriate use and upkeep of LLINs is essential to ensure effectiveness of LLIN based malaria interventions.
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Affiliation(s)
- Paul M Gichuki
- Eastern & Southern Africa Centre of International Parasite Control, Kenya Medical Research Institute, Nairobi, Kenya. .,School of Health Sciences, Meru University of Science and Technology, Meru, Kenya.
| | - Luna Kamau
- Centre for Biotechnology Research and Development, Kenya Medical Research Institute, Nairobi, Kenya
| | - Kiambo Njagi
- Division of National Malaria Programme, Ministry of Health, Nairobi, Kenya
| | - Solomon Karoki
- Division of National Malaria Programme, Ministry of Health, Nairobi, Kenya
| | - Njoroge Muigai
- Department of Health, Kirinyaga County, Kirinyaga, Kenya
| | - Damaris Matoke-Muhia
- Centre for Biotechnology Research and Development, Kenya Medical Research Institute, Nairobi, Kenya
| | - Nabie Bayoh
- Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya.,Centers for Disease Control and Prevention, Kisumu, Kenya
| | - Evan Mathenge
- Eastern & Southern Africa Centre of International Parasite Control, Kenya Medical Research Institute, Nairobi, Kenya
| | - Rajpal S Yadav
- Department of Control of Neglected Tropical Diseases, World Health Organization, Geneva, Switzerland
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Metelo-Matubi E, Zanga J, Binene G, Mvuama N, Ngamukie S, Nkey J, Schopp P, Bamba M, Irish S, Nguya-Kalemba-Maniania J, Fasine S, Nagahuedi J, Muyembe JJ, Mansiangi P. The effect of a mass distribution of insecticide-treated nets on insecticide resistance and entomological inoculation rates of Anopheles gambiae s.l. in Bandundu City, Democratic Repub`lic of Congo. Pan Afr Med J 2021; 40:118. [PMID: 34887992 PMCID: PMC8627145 DOI: 10.11604/pamj.2021.40.118.27365] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 10/10/2021] [Indexed: 11/26/2022] Open
Abstract
Introduction insecticide-treated nets (ITNs) remain the mainstay of malaria vector control in the Democratic Republic of Congo. However, insecticide resistance of malaria vectors threatens their effectiveness. Entomological inoculation rates and insecticide susceptibility in Anopheles gambiae s.l. were evaluated before and after mass distribution of ITNs in Bandundu City for possible occurrence of resistance. Methods a cross-sectional study was conducted from 15th July 2015 to 15th June 2016. Adult mosquitoes were collected using pyrethrum spray catches and human landing catches and identified to species level and tested for the presence of sporozoites. Bioassays were carried out before and after distribution of ITNs to assess the susceptibility of adult mosquitoes to insecticides. Synergist bioassays were also conducted and target site mutations assessed using Polymerase chain reaction (PCR). Results a total of 1754 female An. gambiae s.l. were collected before and after deployment of ITNs. Fewer mosquitoes were collected after the distribution of ITNs. However, there was no significant difference in sporozoite rates or the overall entomological inoculation rate before and after the distribution of ITNs. Test-mosquitoes were resistant to deltamethrin, permethrin, and Dichlorodiphenyltrichloroethane but susceptible to bendiocarb. Pre-exposure of mosquitoes to Piperonyl butoxide increased their mortality after exposure to permethrin and deltamethrin. The frequency of the Kinase insert domain receptor (kdr)-West gene increased from 92 to 99% before and after the distribution of nets, respectively. Conclusion seasonal impacts could be a limiting factor in the analysis of these data; however, the lack of decrease in transmission after the distribution of new nets could be explained by the high-level of resistance to pyrethroid.
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Affiliation(s)
- Emery Metelo-Matubi
- Faculté de Médecine, Université de Bandundu, B.P 548 Bandundu-ville, Bandundu, République Démocratique de Congo.,Institut National de Recherche Biomédicale, B.P 1197 KIN 1, Kinshasa, République Démocratique de Congo.,Faculté des Sciences, Département de Biologie, Unité de Recherche Entomologique, B.P 190 KIN XI, Université de Kinshasa, Kinshasa, République Démocratique de Congo
| | - Josué Zanga
- Faculté de Médecine, Ecole de Santé Publique, Département de Santé Environnementale, B.P 834 KIN XI, Université de Kinshasa, Kinshasa, République Démocratique de Congo
| | - Guillaume Binene
- Institut National de Recherche Biomédicale, B.P 1197 KIN 1, Kinshasa, République Démocratique de Congo
| | - Nono Mvuama
- Faculté de Médecine, Ecole de Santé Publique, Département de Santé Environnementale, B.P 834 KIN XI, Université de Kinshasa, Kinshasa, République Démocratique de Congo
| | - Solange Ngamukie
- Faculté de Médecine, Ecole de Santé Publique, Département de Santé Environnementale, B.P 834 KIN XI, Université de Kinshasa, Kinshasa, République Démocratique de Congo
| | - Jadis Nkey
- Faculté de Médecine, Université de Bandundu, B.P 548 Bandundu-ville, Bandundu, République Démocratique de Congo
| | - Pauline Schopp
- United States President´s Malaria Initiative and Entomology Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, 1600 Clifton Road NE, Atlanta, GA 30329, USA
| | - Maxwell Bamba
- Faculté de Médecine, Ecole de Santé Publique, Département de Santé Environnementale, B.P 834 KIN XI, Université de Kinshasa, Kinshasa, République Démocratique de Congo
| | - Seth Irish
- United States President´s Malaria Initiative and Entomology Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, 1600 Clifton Road NE, Atlanta, GA 30329, USA
| | | | - Sylvie Fasine
- Institut National de Recherche Biomédicale, B.P 1197 KIN 1, Kinshasa, République Démocratique de Congo
| | - Jonas Nagahuedi
- Faculté des Sciences, Département de Biologie, Unité de Recherche Entomologique, B.P 190 KIN XI, Université de Kinshasa, Kinshasa, République Démocratique de Congo
| | - Jean-Jacques Muyembe
- Institut National de Recherche Biomédicale, B.P 1197 KIN 1, Kinshasa, République Démocratique de Congo
| | - Paul Mansiangi
- Faculté de Médecine, Ecole de Santé Publique, Département de Santé Environnementale, B.P 834 KIN XI, Université de Kinshasa, Kinshasa, République Démocratique de Congo
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Richoux GM, Yang L, Norris E, Jiang S, Linthicum KJ, Bloomquist JR. Resistance-Breaking Insecticidal Activity of New Spatial Insecticides against Aedes aegypti. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2021; 69:9684-9692. [PMID: 34387470 DOI: 10.1021/acs.jafc.1c01200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The use of N-aryl amide derivatives as spatially acting insecticides remains relatively unexplored. To expand this knowledge, we synthesized eighty-nine N-aryl amide analogues and screened them for mortality against an insecticide-susceptible strain of Aedes aegypti mosquitoes, Orlando (OR), using a vapor exposure glass tube assay. Of the screened compounds, twenty-two produced >92% mortality at 24 h and warranted further investigation to determine LC50 values. Fifteen of these analogues had LC50 values within 2 orders of magnitude of transfluthrin, and of significant interest, N-(2,6-dichloro-4-(trifluoromethyl)phenyl)-2,2,3,3,3-pentafluoropropanamide (compound 70) was nearly as potent as transfluthrin and exhibited greater toxicity than metofluthrin when screened against OR A. aegypti. Compounds exhibiting potent toxicity against OR A. aegypti or whose structure-activity relationship potentially offered beneficial insights into structure optimization were screened against the insecticide-resistant, Puerto Rico (PR), strain of A. Aegypti, and it was discovered that not only did these N-arylamides typically show little resistance, some such as N-(2,6-dichloropyridin-4-yl)-2,2,3,3,4,4,4-heptafluorobutanamide (compound 36) and 2,2,3,3,4,4,4-heptafluoro-N-(3,4,5-trifluorophenyl)butanamide (compound 40) were actually more potent against the PR mosquitoes. Due to this promising insecticidal activity, five compounds were administered orally to mice to determine acute oral rodent toxicity. All five compounds were found to have mouse oral toxicity LD50 values well above the minimum safe level as set by the Innovative Vector Control Consortium (50 mg/kg). In addition to the promising biological activity documented here, we report the structure-activity relationship analysis used to guide the derivatization approach taken and to further inform future efforts in the development of N-arylamides as potential resistance-breaking, spatially acting insecticides.
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Affiliation(s)
- Gary M Richoux
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, Florida 32610, United States
| | - Liu Yang
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, Florida 32610, United States
| | - Edmund Norris
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, Florida 32610, United States
- Agricultural and Veterinary Entomology, USDA, ARS, Center for Medical, Gainesville, Florida 32608, United States
| | - Shiyao Jiang
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, Florida 32610, United States
| | - Kenneth J Linthicum
- Agricultural and Veterinary Entomology, USDA, ARS, Center for Medical, Gainesville, Florida 32608, United States
| | - Jeffrey R Bloomquist
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, Florida 32610, United States
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Clegban CMY, Camara S, Koffi AA, Ahoua Alou LP, Kabran Kouame JP, Koffi AF, Kouassi PK, Moiroux N, Pennetier C. Evaluation of Yahe ® and Panda ® 2.0 long-lasting insecticidal nets against wild pyrethroid-resistant Anopheles gambiae s.l. from Côte d'Ivoire: an experimental hut trial. Parasit Vectors 2021; 14:347. [PMID: 34210362 PMCID: PMC8247218 DOI: 10.1186/s13071-021-04843-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Accepted: 06/11/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Long-lasting insecticidal nets (LLINs) have played an important role in reducing the global malaria burden since 2000. They are a core prevention tool used widely by people at risk of malaria. The Vector Control Prequalification mechanism of the Word Health Organization (WHO-Vector Control PQ) established the testing and evaluation guidelines for LLINs before registration for public use. In the present study, two new brands of deltamethrin-impregnated nets (Yahe® LN and Panda® Net 2.0) were evaluated in an experimental hut against wild pyrethroid-resistant Anopheles gambiae s.l. in M'Bé nearby Bouaké, central Côte d'Ivoire. METHODS The performance of Yahe® LN and Panda® Net 2.0 was compared with that of PermaNet 2.0, conventionally treated nets (CTN), and untreated net to assess the blood-feeding inhibition, deterrence, induced exophily, and mortality. RESULTS Cone bioassay results showed that Panda® Net 2.0, PermaNet 2.0 and Yahe® LN (both unwashed and washed 20 times) induced > 95% knockdown or > 80% mortality of the susceptible Anopheles gambiae Kisumu strain. With the pyrethroid-resistant M'Bé strain, mortality rate for all treated nets did not exceed 70%. There was a significant reduction in entry and blood feeding (p < 0.05) and an increase in exophily and mortality rates (p < 0.05) with all treatments compared to untreated nets, except the CTNs. However, the personal protection induced by these treated nets decreased significantly after 20 washes. The performance of Panda® Net 2.0 was equal to PermaNet® 2.0 in terms of inhibiting blood feeding, but better than PermaNet® 2.0 in terms of mortality. CONCLUSION This study showed that Yahe® LN and Panda® Net 2.0 met the WHO Pesticide Evaluation Scheme (WHOPES) criteria to undergo phase III trial at the community level. Due to an increasing spread and development of pyrethroid resistance in malaria vectors, control of malaria transmission must evolve into an integrated vector management relying on a large variety of efficient control tools.
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Affiliation(s)
- Cyntia-Muriel Y Clegban
- Institut Pierre Richet/Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire. .,Université Félix Houphouët-Boigny, Abidjan, Côte d'Ivoire. .,MIVEGEC, Univ Montpellier, CNRS, IRD, Montpellier, France.
| | - Soromane Camara
- Institut Pierre Richet/Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire.,Université Félix Houphouët-Boigny, Abidjan, Côte d'Ivoire.,MIVEGEC, Univ Montpellier, CNRS, IRD, Montpellier, France
| | - A Alphonsine Koffi
- Institut Pierre Richet/Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | - Ludovic P Ahoua Alou
- Institut Pierre Richet/Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | | | - A Fernand Koffi
- Institut Pierre Richet/Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | | | | | - Cédric Pennetier
- Institut Pierre Richet/Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire.,MIVEGEC, Univ Montpellier, CNRS, IRD, Montpellier, France
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17
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Yovogan B, Sovi A, Padonou GG, Adoha CJ, Akinro B, Chitou S, Accrombessi M, Dangbénon E, Akpovi H, Messenger LA, Ossè R, Hounto AO, Cook J, Kleinschmidt I, Ngufor C, Rowland M, Protopopoff N, Akogbéto MC. Pre-intervention characteristics of the mosquito species in Benin in preparation for a randomized controlled trial assessing the efficacy of dual active-ingredient long-lasting insecticidal nets for controlling insecticide-resistant malaria vectors. PLoS One 2021; 16:e0251742. [PMID: 34014982 PMCID: PMC8136630 DOI: 10.1371/journal.pone.0251742] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Accepted: 05/01/2021] [Indexed: 11/18/2022] Open
Abstract
Background This study provides detailed characteristics of vector populations in preparation for a three-arm cluster randomized controlled trial (RCT) aiming to compare the community impact of dual active-ingredient (AI) long-lasting insecticidal nets (LLINs) that combine two novel insecticide classes–chlorfenapyr or pyriproxifen–with alpha-cypermethrin to improve the prevention of malaria transmitted by insecticide-resistant vectors compared to standard pyrethroid LLINs. Methods The study was carried out in 60 villages across Cove, Zangnanando and Ouinhi districts, southern Benin. Mosquito collections were performed using human landing catches (HLCs). After morphological identification, a sub-sample of Anopheles gambiae s.l. were dissected for parity, analyzed by PCR for species and presence of L1014F kdr mutation and by ELISA-CSP to identify Plasmodium falciparum sporozoite infection. WHO susceptibility tube tests were performed by exposing adult An. gambiae s.l., collected as larvae from each district, to 0.05% alphacypermethrin, 0.75% permethrin, 0.1% bendiocarb and 0.25% pirimiphos-methyl. Synergist assays were also conducted with exposure first to 4% PBO followed by alpha-cypermethrin. Results An. gambiae s.l. (n = 10807) was the main malaria vector complex found followed by Anopheles funestus s.l. (n = 397) and Anopheles nili (n = 82). An. gambiae s.l. was comprised of An. coluzzii (53.9%) and An. gambiae s.s. (46.1%), both displaying a frequency of the L1014F kdr mutation >80%. Although more than 80% of people slept under standard LLIN, human biting rate (HBR) in An. gambiae s.l. was higher indoors [26.5 bite/person/night (95% CI: 25.2–27.9)] than outdoors [18.5 b/p/n (95% CI: 17.4–19.6)], as were the trends for sporozoite rate (SR) [2.9% (95% CI: 1.7–4.8) vs 1.8% (95% CI: 0.6–3.8)] and entomological inoculation rate (EIR) [21.6 infected bites/person/month (95% CI: 20.4–22.8) vs 5.4 (95% CI: 4.8–6.0)]. Parous rate was 81.6% (95%CI: 75.4–88.4). An. gambiae s.l. was resistant to alpha-cypermethrin and permethrin but, fully susceptible to bendiocarb and pirimiphos-methyl. PBO pre-exposure followed by alpha-cypermethrin treatment induced a higher 24 hours mortality compared to alphacypermethrin alone but not exceeding 40%. Conclusions Despite a high usage of standard pyrethroid LLINs, the study area is characterized by intense malaria transmission. The main vectors An. coluzzii and An. gambiae s.s. were both highly resistant to pyrethroids and displayed multiple resistance mechanisms, L1014F kdr mutation and mixed function oxidases. These conditions of the study area make it an appropriate site to conduct the trial that aims to assess the effect of novel dual-AI LLINs on malaria transmitted by insecticide-resistant vectors.
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Affiliation(s)
- Boulais Yovogan
- Faculté des Sciences et Techniques de l’Université d’Abomey-Calavi, Abomey-Calavi, Benin
- Centre de Recherche Entomologique de Cotonou, Cotonou, Benin
| | - Arthur Sovi
- Centre de Recherche Entomologique de Cotonou, Cotonou, Benin
- Faculté d’Agronomie, Université de Parakou, Parakou, Benin
- Faculty of Infectious and Tropical Diseases, Disease Control Department, London School of Hygiene and Tropical Medicine, London, United Kingdom
- * E-mail:
| | - Gil G. Padonou
- Faculté des Sciences et Techniques de l’Université d’Abomey-Calavi, Abomey-Calavi, Benin
- Centre de Recherche Entomologique de Cotonou, Cotonou, Benin
| | - Constantin J. Adoha
- Faculté des Sciences et Techniques de l’Université d’Abomey-Calavi, Abomey-Calavi, Benin
- Centre de Recherche Entomologique de Cotonou, Cotonou, Benin
| | - Bruno Akinro
- Centre de Recherche Entomologique de Cotonou, Cotonou, Benin
| | - Saïd Chitou
- Centre de Recherche Entomologique de Cotonou, Cotonou, Benin
| | - Manfred Accrombessi
- Faculty of Infectious and Tropical Diseases, Disease Control Department, London School of Hygiene and Tropical Medicine, London, United Kingdom
- Institut de Recherche Clinique du Bénin, Abomey-Calavi, Benin
| | | | - Hilaire Akpovi
- Centre de Recherche Entomologique de Cotonou, Cotonou, Benin
| | - Louisa A. Messenger
- Faculty of Infectious and Tropical Diseases, Disease Control Department, London School of Hygiene and Tropical Medicine, London, United Kingdom
- American Society for Microbiology, Washington, DC, United States of America
| | - Razaki Ossè
- Centre de Recherche Entomologique de Cotonou, Cotonou, Benin
- Ecole de Gestion et d’Exploitation des Systèmes d’Elevage, Université Nationale d’Agriculture, Kétou, Benin
| | - Aurore Ogouyemi Hounto
- Programme Nationale de Lutte Contre Le Paludisme (PNLP), Cotonou, Benin
- Faculté des Sciences de la Santé, Université d’Abomey-Calavi, Cotonou, Benin
| | - Jackie Cook
- Medical Research Council (MRC) Tropical International Statistics and Epidemiology Epidemiology Group, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Immo Kleinschmidt
- Medical Research Council (MRC) Tropical International Statistics and Epidemiology Epidemiology Group, London School of Hygiene and Tropical Medicine, London, United Kingdom
- School of Pathology, Faculty of Health Sciences, University of Witwatersrand, Johannesburg, South Africa
- Southern African Development Community Malaria Elimination Eight Secretariat, Windhoek, Namibia
| | - Corine Ngufor
- Centre de Recherche Entomologique de Cotonou, Cotonou, Benin
- Faculty of Infectious and Tropical Diseases, Disease Control Department, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Mark Rowland
- Faculty of Infectious and Tropical Diseases, Disease Control Department, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Natacha Protopopoff
- Faculty of Infectious and Tropical Diseases, Disease Control Department, London School of Hygiene and Tropical Medicine, London, United Kingdom
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18
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Martin JL, Mosha FW, Lukole E, Rowland M, Todd J, Charlwood JD, Mosha JF, Protopopoff N. Personal protection with PBO-pyrethroid synergist-treated nets after 2 years of household use against pyrethroid-resistant Anopheles in Tanzania. Parasit Vectors 2021; 14:150. [PMID: 33691742 PMCID: PMC7944899 DOI: 10.1186/s13071-021-04641-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 02/16/2021] [Indexed: 11/10/2022] Open
Abstract
Background The spread of pyrethroid resistance in malaria vectors threatens the effectiveness of standard long-lasting insecticidal nets (LLIN). Synergist nets combine pyrethroid (Py) and piperonyl-butoxide (PBO) to enhance potency against resistance mediated by mono-oxygenase mechanisms. Our project assessed personal protection of the World Health Organization first-in-class PBO-Py LLIN (Olyset Plus) versus the standard LLIN (Olyset net) against pyrethroid-resistant Anopheles gambiae sensu lato (s.l.) and An. funestus in North-West Tanzania after 20 months of household use. Methods From a household survey, 39 standard Olyset net and 39 Olyset Plus houses were selected. The physical integrity and hole index (HI) of the nets were assessed, and resting mosquitoes were collected from inside nets and from room walls. The indoor abundance was estimated using CDC light traps and species identified using PCR. The bioefficacy of PBO and standard LLINs against wild Anopheles was assessed using 30-minute cylinder bioassays. Results Of 2397 Anopheles collected, 8.9% (n = 213) were resting inside standard Olyset nets, while none were found inside Olyset Plus nets (PBO-Py LLINs) of any HI category. Resting density of blood-fed mosquitoes was higher on walls of sleeping rooms with Olyset nets compared to Olyset Plus (0.62 vs 0.10, density ratio [DR]: 0.03, 95% CI 0.01–0.13, p < 0.001). Mosquitoes were found inside Olyset nets of all WHO HI categories, but more were collected inside the more damaged nets (HI ≥ 643) than in less damaged (HI 0–64) nets (DR: 6.4, 95% CI 1.1–36.0, p = 0.037). In bioassay, mortality of An. gambiae s.l. was higher with Olyset Plus than with Olyset nets for new nets (76.8% vs 27.5%) and nets used for 20 months (56.8% vs 12.8%); similar trends were observed with An. funestus. Conclusion The PBO-Py LLINs provided improved protection after 20 months of household use, as demonstrated by the higher bioassay mortality and absence of pyrethroid-resistant An. gambiae sensu stricto (s.s.) and An. funestus collected from inside Olyset Plus nets, irrespective of HI category, as compared to Olyset nets.![]()
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Affiliation(s)
- Jackline L Martin
- Kilimanjaro Christian Medical University College, Moshi, United Republic of Tanzania. .,National Institute for Medical Research-Mwanza Centre, Mwanza, United Republic of Tanzania.
| | - Franklin W Mosha
- Kilimanjaro Christian Medical University College, Moshi, United Republic of Tanzania
| | - Eliud Lukole
- Kilimanjaro Christian Medical University College, Moshi, United Republic of Tanzania
| | - Mark Rowland
- London School of Hygiene and Tropical, London, United Kingdom
| | - Jim Todd
- National Institute for Medical Research-Mwanza Centre, Mwanza, United Republic of Tanzania.,London School of Hygiene and Tropical, London, United Kingdom
| | | | - Jacklin F Mosha
- National Institute for Medical Research-Mwanza Centre, Mwanza, United Republic of Tanzania
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Mosha JF, Kulkarni MA, Messenger LA, Rowland M, Matowo N, Pitt C, Lukole E, Taljaard M, Thickstun C, Manjurano A, Mosha FW, Kleinschmidt I, Protopopoff N. Protocol for a four parallel-arm, single-blind, cluster-randomised trial to assess the effectiveness of three types of dual active ingredient treated nets compared to pyrethroid-only long-lasting insecticidal nets to prevent malaria transmitted by pyrethroid insecticide-resistant vector mosquitoes in Tanzania. BMJ Open 2021; 11:e046664. [PMID: 34006037 PMCID: PMC7942254 DOI: 10.1136/bmjopen-2020-046664] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Revised: 01/21/2021] [Accepted: 02/15/2021] [Indexed: 01/21/2023] Open
Abstract
INTRODUCTION The massive scale-up of long-lasting insecticidal nets (LLINs) has led to major reductions in malaria burden in many sub-Saharan African countries. This progress is threatened by widespread insecticide resistance among malaria vectors. This cluster-randomised controlled trial (c-RCT) compares three of the most promising dual active ingredients LLINs (dual-AI LLINs), which incorporate mixtures of insecticides or insecticide synergists to standard LLINs in an area of pyrethroid insecticide resistance. METHODS A four-arm, single-blinded, c-RCT will evaluate the effectiveness of three types of dual-AI LLINs (1) Royal Guard, combining two insecticides, pyriproxyfen and the pyrethroid alpha-cypermethrin; (2) Interceptor G2, combining chlorfenapyr and alpha-cypermethrin; (3) Olyset Plus, an LLIN combining a synergist, piperonyl butoxide and the pyrethroid permethrin, compared with; (4) Interceptor LN, a standard LLIN containing the pyrethroid alpha-cypermethrin as the sole AI. The primary outcomes are malaria infection prevalence in children aged 6 months-14 years and entomological inoculation rate (EIR), as a standard measure of malaria transmission at 24 months postintervention and cost-effectiveness. ETHICS AND DISSEMINATION Ethical approval was received from the institutional review boards of the Tanzanian National Institute for Medical Research, Kilimanjaro Christian Medical University College, London School of Hygiene and Tropical Medicine, and University of Ottawa. Study findings will be actively disseminated via reports and presentations to stakeholders, local community leaders, and relevant national and international policy makers as well as through conferences, and peer-reviewed publications. TRIAL REGISTRATION NUMBER NCT03554616.
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Affiliation(s)
- Jacklin F Mosha
- Parasitology, National Institute for Medical Research Mwanza Research Centre, Mwanza, United Republic of Tanzania
| | - Manisha A Kulkarni
- Epidemiology & Public Health, University of Ottawa Faculty of Medicine, Ottawa, Ontario, Canada
| | - Louisa A Messenger
- Disease Control, London School of Hygiene & Tropical Medicine, London, UK
| | - Mark Rowland
- Disease Control, London School of Hygiene & Tropical Medicine, London, UK
| | - Nancy Matowo
- Disease Control, London School of Hygiene & Tropical Medicine, London, UK
| | - Catherine Pitt
- Global Health and Development, London School of Hygiene & Tropical Medicine, London, UK
| | - Eliud Lukole
- Parasitology, National Institute for Medical Research Mwanza Research Centre, Mwanza, United Republic of Tanzania
- Disease Control, London School of Hygiene & Tropical Medicine, London, UK
| | - Monica Taljaard
- Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada
| | - Charles Thickstun
- Epidemiology & Public Health, University of Ottawa Faculty of Medicine, Ottawa, Ontario, Canada
| | - Alphaxard Manjurano
- Parasitology, National Institute for Medical Research Mwanza Research Centre, Mwanza, United Republic of Tanzania
| | - Franklin W Mosha
- Parasitology, Kilimanjaro Christian Medical University College, Moshi, United Republic of Tanzania
| | - Immo Kleinschmidt
- Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK
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Accrombessi M, Cook J, Ngufor C, Sovi A, Dangbenon E, Yovogan B, Akpovi H, Hounto A, Thickstun C, Padonou GG, Tokponnon F, Messenger LA, Kleinschmidt I, Rowland M, Akogbeto MC, Protopopoff N. Assessing the efficacy of two dual-active ingredients long-lasting insecticidal nets for the control of malaria transmitted by pyrethroid-resistant vectors in Benin: study protocol for a three-arm, single-blinded, parallel, cluster-randomized controlled trial. BMC Infect Dis 2021; 21:194. [PMID: 33607958 PMCID: PMC7892705 DOI: 10.1186/s12879-021-05879-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Accepted: 02/09/2021] [Indexed: 11/21/2022] Open
Abstract
BACKGROUND Long-lasting insecticidal nets (LLINs) are currently the primary method of malaria control in sub-Saharan Africa and have contributed to a significant reduction in malaria burden over the past 15 years. However, this progress is threatened by the wide-scale selection of insecticide-resistant malaria vectors. It is, therefore, important to accelerate the generation of evidence for new classes of LLINs. METHODS This protocol presents a three-arm superiority, single-blinded, cluster randomized controlled trial to evaluate the impact of 2 novel dual-active ingredient LLINs on epidemiological and entomological outcomes in Benin, a malaria-endemic area with highly pyrethroid-resistant vector populations. The study arms consist of (i) Royal Guard® LLIN, a net combining a pyrethroid (alpha-cypermethrin) plus an insect growth regulator (pyriproxyfen), which in the adult female is known to disrupt reproduction and egg fertility; (ii) Interceptor G2® LLIN, a net incorporating two adulticides (alpha-cypermethrin and chlorfenapyr) with different modes of action; and (iii) the control arm, Interceptor® LLIN, a pyrethroid (alpha-cypermethrin) only LLIN. In all arms, one net for every 2 people will be distributed to each household. Sixty clusters were identified and randomised 1:1:1 to each study arm. The primary outcome is malaria case incidence measured over 24 months through active case detection in a cohort of 25 children aged 6 months to 10 years, randomly selected from each cluster. Secondary outcomes include 1) malaria infection prevalence (all ages) and prevalence of moderate to severe anaemia in children under 5 years old, measured at 6 and 18 months post-intervention; 2) entomological indices measured every 3 months using human landing catches over 24 months. Insecticide resistance intensity will also be monitored over the study period. DISCUSSION This study is the second cluster randomised controlled trial to evaluate the efficacy of these next-generation LLINs to control malaria transmitted by insecticide-resistant mosquitoes. The results of this study will form part of the WHO evidence-based review to support potential public health recommendations of these nets and shape malaria control strategies of sub-Saharan Africa for the next decade. TRIAL REGISTRATION ClinicalTrials.gov, NCT03931473 , registered on 30 April 2019.
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Affiliation(s)
- Manfred Accrombessi
- Faculty of Infectious and Tropical Diseases, Disease Control Department, London School of Hygiene and Tropical Medicine, WC1E 7HT, London, UK.
| | - Jackie Cook
- Medical Research Council (MRC) International Statistics and Epidemiology Epidemiology Group, London School of Hygiene and Tropical Medicine, WC1E 7HT, London, UK
| | - Corine Ngufor
- Faculty of Infectious and Tropical Diseases, Disease Control Department, London School of Hygiene and Tropical Medicine, WC1E 7HT, London, UK
| | - Arthur Sovi
- Faculty of Infectious and Tropical Diseases, Disease Control Department, London School of Hygiene and Tropical Medicine, WC1E 7HT, London, UK
- Centre de Recherche Entomologique de Cotonou (CREC), Cotonou, Benin
- Faculty of Agronomy, University of Parakou, Parakou, Benin
| | | | - Boulais Yovogan
- Centre de Recherche Entomologique de Cotonou (CREC), Cotonou, Benin
| | - Hilaire Akpovi
- Centre de Recherche Entomologique de Cotonou (CREC), Cotonou, Benin
| | - Aurore Hounto
- National Malaria Control Program, Ministry of Health, Cotonou, Benin
| | - Charles Thickstun
- School of Epidemiology and Public Health, Faculty of Medicine, University of Ottawa, Ottawa, Canada
| | - Gil G Padonou
- Centre de Recherche Entomologique de Cotonou (CREC), Cotonou, Benin
| | | | - Louisa A Messenger
- Faculty of Infectious and Tropical Diseases, Disease Control Department, London School of Hygiene and Tropical Medicine, WC1E 7HT, London, UK
| | - Immo Kleinschmidt
- Medical Research Council (MRC) International Statistics and Epidemiology Epidemiology Group, London School of Hygiene and Tropical Medicine, WC1E 7HT, London, UK
- School of Pathology, Faculty of Health Sciences, University of Witwatersrand, Johannesburg, South Africa
- Southern African Development Community Malaria Elimination Eight Secretariat, Windhoek, Namibia
| | - Mark Rowland
- Faculty of Infectious and Tropical Diseases, Disease Control Department, London School of Hygiene and Tropical Medicine, WC1E 7HT, London, UK
| | | | - Natacha Protopopoff
- Faculty of Infectious and Tropical Diseases, Disease Control Department, London School of Hygiene and Tropical Medicine, WC1E 7HT, London, UK
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21
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Bamou R, Kopya E, Nkahe LD, Menze BD, Awono-Ambene P, Tchuinkam T, Njiokou F, Wondji CS, Antonio-Nkondjio C. Increased prevalence of insecticide resistance in Anopheles coluzzii populations in the city of Yaoundé, Cameroon and influence on pyrethroid-only treated bed net efficacy. ACTA ACUST UNITED AC 2021; 28:8. [PMID: 33528357 PMCID: PMC7852377 DOI: 10.1051/parasite/2021003] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 01/08/2021] [Indexed: 11/15/2022]
Abstract
In Cameroon, pyrethroid-only long-lasting insecticidal nets (LLINs) are still largely used for malaria control. The present study assessed the efficacy of such LLINs against a multiple-resistant population of the major malaria vector, Anopheles coluzzii, in the city of Yaoundé via a cone bioassay and release-recapture experimental hut trial. Susceptibility of field mosquitoes in Yaoundé to pyrethroids, DDT, carbamates and organophosphate insecticides was investigated using World Health Organization (WHO) bioassay tube tests. Mechanisms of insecticide resistance were characterised molecularly. Efficacy of unwashed PermaNet® 2.0 was evaluated against untreated control nets using a resistant colonised strain of An. coluzzii. Mortality, exophily and blood feeding inhibition were estimated. Field collected An. coluzzii displayed high resistance with mortality rates of 3.5% for propoxur (0.1%), 4.16% for DDT (4%), 26.9% for permethrin (0.75%), 50.8% for deltamethrin (0.05%), and 80% for bendiocarb (0.1%). High frequency of the 1014F west-Africa kdr allele was recorded in addition to the overexpression of several detoxification genes, such as Cyp6P3, Cyp6M2, Cyp9K1, Cyp6P4 Cyp6Z1 and GSTe2. A low mortality rate (23.2%) and high blood feeding inhibition rate (65%) were observed when resistant An. coluzzii were exposed to unwashed PermaNet® 2.0 net compared to control untreated net (p < 0.001). Furthermore, low personal protection (52.4%) was observed with the resistant strain, indicating reduction of efficacy. The study highlights the loss of efficacy of pyrethroid-only nets against mosquitoes exhibiting high insecticide resistance and suggests a switch to new generation bed nets to improve control of malaria vector populations in Yaoundé.
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Affiliation(s)
- Roland Bamou
- Vector-Borne Diseases Laboratory of the Applied Biology and Ecology Research Unit (VBID-URBEA), Department of Animal Biology, Faculty of Science of the University of Dschang, P.O. Box 067, Dschang, Cameroon - Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288 Yaoundé, Cameroon
| | - Edmond Kopya
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288 Yaoundé, Cameroon - Faculty of Sciences, University of Yaoundé I, P.O. Box 337, Yaoundé, Cameroon
| | - Leslie Diane Nkahe
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288 Yaoundé, Cameroon - Faculty of Sciences, University of Yaoundé I, P.O. Box 337, Yaoundé, Cameroon
| | - Benjamin D Menze
- Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United Kingdom - Centre for Research in Infectious Disease (CRID), P.O. Box 13591, Yaoundé, Cameroon
| | - Parfait Awono-Ambene
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288 Yaoundé, Cameroon
| | - Timoléon Tchuinkam
- Vector-Borne Diseases Laboratory of the Applied Biology and Ecology Research Unit (VBID-URBEA), Department of Animal Biology, Faculty of Science of the University of Dschang, P.O. Box 067, Dschang, Cameroon
| | - Flobert Njiokou
- Faculty of Sciences, University of Yaoundé I, P.O. Box 337, Yaoundé, Cameroon
| | - Charles S Wondji
- Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United Kingdom - Centre for Research in Infectious Disease (CRID), P.O. Box 13591, Yaoundé, Cameroon
| | - Christophe Antonio-Nkondjio
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288 Yaoundé, Cameroon - Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United Kingdom
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22
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Manjurano A, Omolo JJ, Lyimo E, Miyaye D, Kishamawe C, Matemba LE, Massaga JJ, Changalucha J, Kazyoba PE. Performance evaluation of the highly sensitive histidine-rich protein 2 rapid test for plasmodium falciparum malaria in North-West Tanzania. Malar J 2021; 20:58. [PMID: 33482835 PMCID: PMC7821515 DOI: 10.1186/s12936-020-03568-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Accepted: 12/24/2020] [Indexed: 11/18/2022] Open
Abstract
Background Precise detection of Plasmodium infections in community surveys is essential for effective malaria control. Microscopy and rapid diagnostic tests (RDTs) are the major techniques used to identify malaria infections in the field-based surveys. Although microscopy is still considered as the gold standard, RDTs are increasingly becoming versatile due to their rapid and adequate performance characteristics. Methods A malaria prevalence cross-sectional survey was carried out in north-western Tanzania in 2016, aimed at appraising the performance of high sensitivity Plasmodium falciparum (HSPf) tests compared to SD Bioline Pf and microscopy in detecting P. falciparum infections. A total of 397 individuals aged five years and above were tested for P. falciparum infections. The sensitivity, specificity, positive, and negative predictive values (PPV and NPV) of microscopy, Pf RDT and HSPf RDT was determined using PCR as the gold standard method. Results The prevalence of P. falciparum infections determined by microscopy, SD Bioline Pf, HSPf and PCR was 21.9, 27.7, 33.3 and 43.2%, respectively. The new HSPf RDT had significantly higher sensitivity (98.2%) and specificity (91.6%) compared to the routinely used SD Bioline Pf RDT(P < 0.001). The positive predictive value (PPV) was 81.8% and the negative predictive value (NPV) was 99.2% for the routinely used SD Bioline Pf RDT. Moreover, HSPf RDT had sensitivity of 69% and specificity of 76.8% compared to microscopy. The PPV was 45.5% and the NPV was 89.8% for microscopy. Furthermore, the analytical sensitivity test indicated that the newly developed HSPf RDT had lower detection limits compared to routinely used SD Bioline RDT. Conclusions HSPf RDT had better performance when compared to both microscopy and the currently used malaria RDTs. The false negativity could be associated with the low parasite density of the samples. False positivity may be related to the limitations of the expertise of microscopists or persistent antigenicity from previous infections in the case of RDTs. Nevertheless, HS PfRDT performed better compared to routinely used Pf RDT, and microscopy in detecting malaria infections. Therefore, HS Pf RDT presents the best alternative to the existing commercial/regularly available RDTs due to its sensitivity and specificity, and reliability in diagnosing malaria infections.
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Affiliation(s)
- Alphaxard Manjurano
- Mwanza Medical Research Center, National Institute for Medical Research, Mwanza, Tanzania.
| | - Justin J Omolo
- National Institute of Medical Research, Head Quarters, P.O. Box 9653, Dar es Salaam, Tanzania
| | - Eric Lyimo
- Mwanza Medical Research Center, National Institute for Medical Research, Mwanza, Tanzania
| | - Donald Miyaye
- Mwanza Medical Research Center, National Institute for Medical Research, Mwanza, Tanzania
| | - Coleman Kishamawe
- Mwanza Medical Research Center, National Institute for Medical Research, Mwanza, Tanzania
| | - Lucas E Matemba
- Dodoma Medical Research Center, National Institute for Medical Research, Dodoma, Tanzania
| | - Julius J Massaga
- National Institute of Medical Research, Head Quarters, P.O. Box 9653, Dar es Salaam, Tanzania
| | - John Changalucha
- Mwanza Medical Research Center, National Institute for Medical Research, Mwanza, Tanzania
| | - Paul E Kazyoba
- National Institute of Medical Research, Head Quarters, P.O. Box 9653, Dar es Salaam, Tanzania
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Nlinwe NO, Singong YC, Florentine TMR. Evaluation of malaria preventive measures among adult patients attending the Bamendjou and Foumbot district hospitals of the West Region of Cameroon. Malar J 2021; 20:60. [PMID: 33482826 PMCID: PMC7821540 DOI: 10.1186/s12936-021-03592-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Accepted: 01/15/2021] [Indexed: 01/25/2023] Open
Abstract
BACKGROUND Although a significant decrease in entomological and epidemiological indicators was reported in Cameroon since the introduction of insecticide-treated bed nets, malaria prevalence remains high also in some parts of the West Region of Cameroon. This study was designed to evaluate malaria preventive measures among patients attending the Bamendjou and Foumbot District hospitals of the West Region of Cameroon. METHODS This was a cross-sectional study carried out within a period of 3 months, from January to March 2020. Data was obtained using a structured questionnaire and laboratory analysis. The CareStart™ Pf Malaria HRP2 qualitative rapid diagnostic test was used for malaria diagnosis. The questionnaire was designed to collect information on respondent's socio-demographic characteristics, and the use of malaria preventive measures. Data were analysed using descriptive statistics, regression analysis, and Chi-square (and Fisher's exact) test. RESULTS A total of 170 study participants were recruited in Foumbot and 197 in Bamendjou. Malaria was significantly (P < 0.0001) more prevalent in Foumbot (47.06%) than in Bamendjou (19.8%). In Foumbot, non-use of insect repellent spray (P = 0.0214), insect repellent body cream (P = 0.0009), mosquito spray (P = 0.0001) and not draining stagnant water (P = 0.0004) predisposed to higher risk of malaria. In Bamendjou, non-use of insect repellent spray (P = 0.0012), long-lasting insecticidal bed nets (P = 0.0001), window and door nets (P = 0.0286), predisposed to a higher risk of malaria. CONCLUSIONS Malaria prevalence was high among the study participants especially in Foumbot. An adequate follow-up to ensure effective execution of the recently launched third phase of LLINs distribution campaign in Cameroon is recommended. Additionally, integrated vector management is required to ensure effective control of malaria transmission in Foumbot and Bamendjou.
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Affiliation(s)
- Nfor Omarine Nlinwe
- Department of Medical Laboratory Science, The University of Bamenda, Faculty of Health Sciences, Bambili, P.O Box 39, Bamenda, North West Region, Cameroon.
| | - Yengong Clinton Singong
- Department of Medical Laboratory Science, The University of Bamenda, Faculty of Health Sciences, Bambili, P.O Box 39, Bamenda, North West Region, Cameroon
| | - Tenkam Makamdoum Ruth Florentine
- Department of Medical Laboratory Science, The University of Bamenda, Faculty of Health Sciences, Bambili, P.O Box 39, Bamenda, North West Region, Cameroon
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Tungu PK, Waweru J, Karthi S, Wangai J, Kweka EJ. Field evaluation of Veeralin, an alpha-cypermethrin + PBO long-lasting insecticidal net, against natural populations of Anopheles funestus in experimental huts in Muheza, Tanzania. CURRENT RESEARCH IN PARASITOLOGY & VECTOR-BORNE DISEASES 2021; 1:100030. [PMID: 35284898 PMCID: PMC8906063 DOI: 10.1016/j.crpvbd.2021.100030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Revised: 05/12/2021] [Accepted: 05/18/2021] [Indexed: 11/12/2022]
Abstract
The success of long-lasting insecticidal nets (LLIN) as the primary method for preventing malaria is threatened by pyrethroid resistance in Anopheles vectors. New generation long-lasting nets incorporating PBO synergist (piperonyl butoxide) with pyrethroid are designed to control insecticide-resistant mosquitoes. The efficacy of Veeralin® PBO LLINs was evaluated in experimental huts against wild free-flying pyrethroid-resistant Anopheles funestus (s.l.). Mosquito mortality, blood-feeding inhibition and personal protection were compared between untreated nets, standard LLINs and PBO/pyrethroid combination nets. Blood-feeding rates recorded with 20-times washed Veeralin were not significantly different from those with 20-times washed PermaNet 3.0 LLIN, a WHO Pre-Qualification Team (PQT) approved PBO/pyrethroid LLIN. This provides evidence that Veeralin LLIN provides similar blood-feeding inhibition to the standard approved LLIN and thus meets WHO PQT criteria for blood-feeding. Results show significantly higher mortality for Veeralin PBO LLINs against pyrethroid-resistant Anopheles funestus (s.l.) compared to DuraNet, a WHO PQT approved standard pyrethroid-only LLIN, both when unwashed and washed 20 times. The improved efficacy over a standard pyrethroid-only LLIN can be attributed to the effect of PBO in the Veeralin LLIN, hence meeting the Vector Control Advisory Group (VCAG) criteria for a resistance breaking LLIN. Long-lasting insecticidal nets with PBO play a key role in blood-feeding and mortality of mosquitoes. Incorporating PBO in LLIN enhanced the efficacy of LLINs against wild populations of Anopheles mosquitoes. Understanding the impact of LLINs + PBO on mortality, repellency, knockdown could be an asset in vector control toolbox.
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Mosha JF, Lukole E, Charlwood JD, Wright A, Rowland M, Bullock O, Manjurano A, Kisinza W, Mosha FW, Kleinschmidt I, Protopopoff N. Risk factors for malaria infection prevalence and household vector density between mass distribution campaigns of long-lasting insecticidal nets in North-western Tanzania. Malar J 2020; 19:297. [PMID: 32819368 PMCID: PMC7441624 DOI: 10.1186/s12936-020-03369-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Accepted: 08/10/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Long-lasting insecticidal nets (LLINs) are the most widely deployed vector control intervention in sub-Saharan Africa to prevent malaria. Recent reports indicate selection of pyrethroid insecticide resistance is widespread in mosquito vectors. This paper explores risk factors associated with malaria infection prevalence and vector density between mass distribution campaigns, changes in net coverage, and loss of protection in an area of high pyrethroid resistance in Northwest Tanzania. METHODS A cross sectional malaria survey of 3456 children was undertaken in 2014 in Muleba district, Kagera region west of Lake Victoria. Vector density was assessed using indoor light traps and outdoor tent traps. Anophelines were identified to species using PCR and tested for Plasmodium falciparum circumsporozoite protein. Logistic regression was used to identify household and environmental factors associated with malaria infection and regression binomial negative for vector density. RESULTS LLIN use was 27.7%. Only 16.9% of households had sufficient nets to cover all sleeping places. Malaria infection was independently associated with access to LLINs (OR: 0.57; 95% CI 0.34-0.98). LLINs less than 2 years old were slightly more protective than older LLINs (53 vs 65% prevalence of infection); however, there was no evidence that LLINs in good condition (hole index < 65) were more protective than LLINs, which were more holed. Other risk factors for malaria infection were age, group, altitude and house construction quality. Independent risk factors for vector density were consistent with malaria outcomes and included altitude, wind, livestock, house quality, open eaves and LLIN usage. Indoor collections comprised 4.6% Anopheles funestus and 95.4% Anopheles gambiae of which 4.5% were Anopheles arabiensis and 93.5% were Anopheles gambiae sensu stricto. CONCLUSION Three years after the mass distribution campaign and despite top-ups, LLIN usage had declined considerably. While children living in households with access to LLINs were at lower risk of malaria, infection prevalence remained high even among users of LLINs in good condition. While effort should be made to maintain high coverage between campaigns, distribution of standard pyrethroid-only LLINs appears insufficient to prevent malaria transmission in this area of intense pyrethroid resistance.
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Affiliation(s)
- Jacklin F Mosha
- National Institute for Medical Research, Mwanza Medical Research Centre, Mwanza, Tanzania.
| | - Eliud Lukole
- National Institute for Medical Research, Mwanza Medical Research Centre, Mwanza, Tanzania
| | - J Derek Charlwood
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK
| | - Alexandra Wright
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK
| | - Mark Rowland
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK
| | - Olivia Bullock
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK
| | - Alphaxard Manjurano
- National Institute for Medical Research, Mwanza Medical Research Centre, Mwanza, Tanzania
| | - William Kisinza
- Amani Medical Research Centre, National Institute for Medical Research, Muheza, Tanzania
| | - Franklin W Mosha
- Kilimanjaro Christian Medical University College, Moshi, Tanzania
| | - Immo Kleinschmidt
- MRC Tropical Epidemiology Group, Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, UK
| | - Natacha Protopopoff
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK
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Okumu F. The fabric of life: what if mosquito nets were durable and widely available but insecticide-free? Malar J 2020; 19:260. [PMID: 32690016 PMCID: PMC7370456 DOI: 10.1186/s12936-020-03321-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Accepted: 07/04/2020] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND Bed nets are the commonest malaria prevention tool and arguably the most cost-effective. Their efficacy is because they prevent mosquito bites (a function of physical durability and integrity), and kill mosquitoes (a function of chemical content and mosquito susceptibility). This essay follows the story of bed nets, insecticides and malaria control, and asks whether the nets must always have insecticides. METHODS Key attributes of untreated or pyrethroid-treated nets are examined alongside observations of their entomological and epidemiological impacts. Arguments for and against adding insecticides to nets are analysed in contexts of pyrethroid resistance, personal-versus-communal protection, outdoor-biting, need for local production and global health policies. FINDINGS Widespread resistance in African malaria vectors has greatly weakened the historical mass mosquitocidal effects of insecticide-treated nets (ITNs), which previously contributed communal benefits to users and non-users. Yet ITNs still achieve substantial epidemiological impact, suggesting that physical integrity, consistent use and population-level coverage are increasingly more important than mosquitocidal properties. Pyrethroid-treatment remains desirable where vectors are sufficiently susceptible, but is no longer universally necessary and should be re-examined alongside other attributes, e.g. durability, coverage, acceptability and access. New ITNs with multiple actives or synergists could provide temporary relief in some settings, but their performance, higher costs, and drawn-out innovation timelines do not justify singular emphasis on insecticides. Similarly, sub-lethal insecticides may remain marginally-impactful by reducing survival of older mosquitoes and disrupting parasite development inside the mosquitoes, but such effects vanish under strong resistance. CONCLUSIONS The public health value of nets is increasingly driven by bite prevention, and decreasingly by lethality to mosquitoes. For context-appropriate solutions, it is necessary to acknowledge and evaluate the potential and cost-effectiveness of durable untreated nets across different settings. Though ~ 90% of malaria burden occurs in Africa, most World Health Organization-prequalified nets are manufactured outside Africa, since many local manufacturers lack capacity to produce the recommended insecticidal nets at competitive scale and pricing. By relaxing conditions for insecticides on nets, it is conceivable that non-insecticidal but durable, and possibly bio-degradable nets, could be readily manufactured locally. This essay aims not to discredit ITNs, but to illustrate how singular focus on insecticides can hinder innovation and sustainability.
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Affiliation(s)
- Fredros Okumu
- Environmental Health & Ecological Sciences, Ifakara Health Institute, Ifakara, Tanzania.
- School of Public Health, University of the Witwatersrand, Johannesburg, Republic of South Africa.
- Institute of Biodiversity, Animal Health & Comparative Medicine, University of Glasgow, Glasgow, UK.
- School of Life Science and Bioengineering, Nelson Mandela African Institution of Science & Technology, Arusha, Tanzania.
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Sovi A, Keita C, Sinaba Y, Dicko A, Traore I, Cisse MBM, Koita O, Dengela D, Flatley C, Bankineza E, Mihigo J, Belemvire A, Carlson J, Fornadel C, Oxborough RM. Anopheles gambiae (s.l.) exhibit high intensity pyrethroid resistance throughout Southern and Central Mali (2016-2018): PBO or next generation LLINs may provide greater control. Parasit Vectors 2020; 13:239. [PMID: 32384907 PMCID: PMC7206711 DOI: 10.1186/s13071-020-04100-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Accepted: 04/25/2020] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND Millions of pyrethroid LLINs have been distributed in Mali during the past 20 years which, along with agricultural use, has increased the selection pressure on malaria vector populations. This study investigated pyrethroid resistance intensity and susceptible status of malaria vectors to alternative insecticides to guide choice of insecticides for LLINs and IRS for effective control of malaria vectors. METHODS For 3 years between 2016 and 2018, susceptibility testing was conducted annually in 14-16 sites covering southern and central Mali. Anopheles gambiae (s.l.) were collected from larval sites and adult mosquitoes exposed in WHO tube tests to diagnostic doses of bendiocarb (0.1%) and pirimiphos-methyl (0.25%). Resistance intensity tests were conducted using CDC bottle bioassays (2016-2017) and WHO tube tests (2018) at 1×, 2×, 5×, and 10× the diagnostic concentration of permethrin, deltamethrin and alpha-cypermethrin. WHO tube tests were conducted with pre-exposure to the synergist PBO followed by permethrin or deltamethrin. Chlorfenapyr was tested in CDC bottle bioassays at 100 µg active ingredient per bottle and clothianidin at 2% in WHO tube tests. PCR was performed to identify species within the An. gambiae complex. RESULTS In all sites An. gambiae (s.l.) showed high intensity resistance to permethrin and deltamethrin in CDC bottle bioassay tests in 2016 and 2017. In 2018, the WHO intensity tests resulted in survivors at all sites for permethrin, deltamethrin and alpha-cypermethrin when tested at 10× the diagnostic dose. Across all sites mean mortality was 33.7% with permethrin (0.75%) compared with 71.8% when pre-exposed to PBO (4%), representing a 2.13-fold increase in mortality. A similar trend was recorded for deltamethrin. There was susceptibility to pirimiphos-methyl, chlorfenapyr and clothianidin in all surveyed sites, including current IRS sites in Mopti Region. An. coluzzii was the primary species in 4 of 6 regions. CONCLUSIONS Widespread high intensity pyrethroid resistance was recorded during 2016-2018 and is likely to compromise the effectiveness of pyrethroid LLINs in Mali. PBO or chlorfenapyr LLINs should provide improved control of An. gambiae (s.l.). Clothianidin and pirimiphos-methyl insecticides are currently being used for IRS as part of a rotation strategy based on susceptibility being confirmed in this study.
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Affiliation(s)
- Arthur Sovi
- Faculty of Agronomy, University of Parakou, BP123 Parakou, Benin
- Centre de Recherche Entomologique de Cotonou, 06BP2604 Cotonou, Benin
- Disease Control Department, Faculty of Infectious & Tropical Diseases, The London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT UK
- PMI VectorLink Project, Abt Associates, Cite du Niger 1, Rue 30, Porte 612, Bamako, Mali
| | - Chitan Keita
- PMI VectorLink Project, Abt Associates, Cite du Niger 1, Rue 30, Porte 612, Bamako, Mali
| | - Youssouf Sinaba
- PMI VectorLink Project, Abt Associates, Cite du Niger 1, Rue 30, Porte 612, Bamako, Mali
| | - Abdourhamane Dicko
- Programme National de Lutte contre le Paludisme (PNLP), Ministère de la Santé, Bamako, Mali
| | - Ibrahim Traore
- Université des Sciences, des Techniques, et des Technologies de Bamako (USTTB), Bamako, Mali
| | - Moussa B. M. Cisse
- Université des Sciences, des Techniques, et des Technologies de Bamako (USTTB), Bamako, Mali
| | - Ousmane Koita
- Université des Sciences, des Techniques, et des Technologies de Bamako (USTTB), Bamako, Mali
| | - Dereje Dengela
- PMI VectorLink Project, Abt Associates, 6130 Executive Blvd, Rockville, MD 20852 USA
| | - Cecilia Flatley
- PMI VectorLink Project, Abt Associates, 6130 Executive Blvd, Rockville, MD 20852 USA
| | - Elie Bankineza
- PMI VectorLink Project, Abt Associates, Cite du Niger 1, Rue 30, Porte 612, Bamako, Mali
| | - Jules Mihigo
- U.S. President’s Malaria Initiative, U.S. Agency for International Development, Bamako, Mali
| | - Allison Belemvire
- U.S. President’s Malaria Initiative, U.S. Agency for International Development, Washington, DC USA
| | - Jenny Carlson
- U.S. President’s Malaria Initiative, U.S. Agency for International Development, Washington, DC USA
| | - Christen Fornadel
- U.S. President’s Malaria Initiative, U.S. Agency for International Development, Washington, DC USA
- Innovative Vector Control Consortium (IVCC), Washington, D.C USA
| | - Richard M. Oxborough
- PMI VectorLink Project, Abt Associates, 6130 Executive Blvd, Rockville, MD 20852 USA
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Nignan C, Niang A, Maïga H, Sawadogo SP, Poda BS, Gnankine O, Dabiré KR, Tripet F, Diabaté A. Comparison of swarming, mating performance and longevity of males Anopheles coluzzii between individuals fed with different natural fruit juices in laboratory and semi-field conditions. Malar J 2020; 19:173. [PMID: 32375825 PMCID: PMC7201624 DOI: 10.1186/s12936-020-03248-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 04/26/2020] [Indexed: 12/02/2022] Open
Abstract
Background It is assumed that malaria vectors feed on locally available nectar sources to obtain energy. Sugar feeding is energetically critical for the Anopheles male swarming and mating activities. However, little is known about the impact of local nectar feeding on male physiological development and its consequences on male mosquito life traits in the malaria control context. This study aimed to evaluate the influence of local fruit juices on the life traits of males Anopheles coluzzii. Methods Swarming characteristics (number of males in swarm, number of mating pairs, and swarm duration) in semi-field conditions; mating rate and longevity in a laboratory setting were compared between males An. coluzzii fed exclusively with mango, papaya or banana juices. The trophic preference was investigated in semi-field conditions. Results The results of this study showed that in the laboratory, mosquitoes fed with papaya juices lived on average longer (10 days) than those fed with banana or mango juices (5 days) and had higher a mating rate (53%) than those fed with banana juice (40%). In the semi-field, the swarm size of mosquitoes fed with banana juice (85 males) was larger than that of mosquitoes fed with mango juice (60 males). The number of mating pairs formed from banana-fed male swarms (17 mating pairs) was higher than that formed from mango-fed male swarm (8 mating pairs). There was no difference in swarming duration between male treatments. Male mosquitoes had a preference for papaya and banana juices. Conclusions The results indicate that the origin of plant-derived feeding is an important factor in the survival and reproduction of mosquitoes. This calls for further investigations of chemical contents of nectars and their impact on the physiological development of mosquitoes.
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Affiliation(s)
- Charles Nignan
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso. .,Laboratoire d'Entomologie Fondamentale et Appliqué/UFR‑SVT/Université Joseph KI - ZERBO, Ouagadougou, Burkina Faso.
| | - Abdoulaye Niang
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso.,Centre for Applied Entomology and Parasitology, School of Life Sciences, Keele University, Keele, UK
| | - Hamidou Maïga
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso
| | | | - Bèwadéyir Serge Poda
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso.,Laboratoire d'Entomologie Fondamentale et Appliqué/UFR‑SVT/Université Joseph KI - ZERBO, Ouagadougou, Burkina Faso
| | - Olivier Gnankine
- Laboratoire d'Entomologie Fondamentale et Appliqué/UFR‑SVT/Université Joseph KI - ZERBO, Ouagadougou, Burkina Faso
| | | | - Frédéric Tripet
- Centre for Applied Entomology and Parasitology, School of Life Sciences, Keele University, Keele, UK
| | - Abdoulaye Diabaté
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso.
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Kemibala EE, Mafra-Neto A, Dekker T, Saroli J, Silva R, Philbert A, Nghabi K, Mboera LEG. A zooprophylaxis strategy using L-lactic acid (Abate) to divert host-seeking malaria vectors from human host to treated non-host animals. Malar J 2020; 19:52. [PMID: 32000782 PMCID: PMC6993509 DOI: 10.1186/s12936-020-3136-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Accepted: 01/22/2020] [Indexed: 11/10/2022] Open
Abstract
Background Zooprophylaxis is a technique in which blood-seeking vectors are diverted to non-host animals in order to lower blood-feeding rates on human hosts. The success of this technique depends on the host preference of the vector being targeted. The objective of this study was to evaluate the effect of l-lactic acid (Abate) to divert malaria mosquito, Anopheles gambiae from feeding on human host. Methods A 14-month-old female goat was treated with Abate, a formulation incorporating l-lactic acid into a slow-release matrix. This formulation was applied on the fur of the goat’s back and neck. The treated animal was then presented to Anopheles gambiae sensu stricto (s.s.) as a prospective host in a semi-field environment (‘mosquito sphere’) together with either an untreated animal or a human. The number of mosquitoes caught to each host choice offered were compared. Results Goat treated with the l-lactic acid formulation successfully attracted An. gambiae at higher rates (70.2%) than the untreated ones (29.8%). Furthermore, An. gambiae s.s. were attracted to a treated goat at an equivalent degree (47.3%) as to their preferred human host (52.7%), even when the preferred host was present in the same environment. Conclusions The findings indicate that human host-seeking mosquitoes can be diverted into feeding on non-preferred hosts despite the close proximity of their favoured host, hence reducing chances for the transmission of blood-borne parasites.
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Affiliation(s)
- Elison E Kemibala
- Ministry of Health, Community Development, Gender, Elderly and Children, Vector Control Training Centre, Muheza, Tanzania. .,University of Dar es Salaam, Dar es Salaam, Tanzania.
| | | | - Teun Dekker
- Swedish University of Agricultural Sciences, Alnarp, Sweden
| | | | | | | | - Kija Nghabi
- University of Dar es Salaam, Dar es Salaam, Tanzania
| | - Leonard E G Mboera
- SACIDS Foundation for One Health, Sokoine University of Agriculture, Morogoro, Tanzania
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30
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Oumbouke WA, Rowland M, Koffi AA, Alou LPA, Camara S, N'Guessan R. Evaluation of an alpha-cypermethrin + PBO mixture long-lasting insecticidal net VEERALIN® LN against pyrethroid resistant Anopheles gambiae s.s.: an experimental hut trial in M'bé, central Côte d'Ivoire. Parasit Vectors 2019; 12:544. [PMID: 31730481 PMCID: PMC6858630 DOI: 10.1186/s13071-019-3796-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 11/07/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Long-lasting insecticidal nets (LLINs) are the primary method of malaria prevention. However, the widespread resistance to pyrethroids among major malaria vector species represents a significant threat to the continued efficacy of pyrethroid LLIN. Piperonyl butoxide (PBO) is a synergist that inhibits the activity of metabolic enzymes of the cytochrome P450 family known to detoxify insecticides including pyrethroids. Synergist LLIN incorporating PBO and a pyrethroid may provide improved control compared to pyrethroid-only LLIN. METHODS The efficacy of VEERALIN® LN (VKA polymers Pvt Ltd, India), an alpha-cypermethrin PBO synergist net was evaluated in experimental huts in M'bé, central Côte d'Ivoire against wild pyrethroid resistant Anopheles gambiae s.s. Comparison was made with a standard alpha-cypermethrin-treated net (MAGNet® LN, VKA polymers Pvt Ltd, India). Nets were tested unwashed and after 20 standardized washes. RESULTS VEERALIN® LN demonstrated improved efficacy compared to MAGNet® LN against wild free-flying pyrethroid-resistant An. gambiae s.s. Before washing, VEERALIN® LN produced mortality of An. gambiae s.s. (51%) significantly higher than the standard pyrethroid-only net (29%) (P < 0.0001). Although there was a significant reduction in mortality with both LLINs after 20 washes, VEERALIN® LN remained superior in efficacy to MAGNet® LN (38 vs 17%) (P < 0.0001). Blood-feeding was significantly inhibited with both types of insecticide-treated nets relative to the untreated control net (P < 0.0001). Unwashed VEERALIN® LN induced significantly higher blood-feeding inhibition of An. gambiae s.s. (62.6%) compared to MAGNet® LN (35.4%) (P < 0.001). The difference persisted after washing, as there was no indication that either LLIN lost protection against biting or blood-feeding. The level of personal protection derived from the use of VEERALIN® LN was high (87%) compared to MAGNet® LN (66-69%) whether unwashed or washed. The AI content of VEERALIN® LN after 20 washes decreased from 6.75 to 6.03 g/kg for alpha-cypermethrin and from 2.95 to 2.64 g/kg for PBO, corresponding to an overall retention of 89% for each compound. CONCLUSIONS The addition of the synergist PBO to pyrethroid net greatly improved protection and control of pyrethroid-resistant An. gambiae s.s. The pyrethroid-PBO VEERALIN® LN has the potential to reduce transmission in areas compromised by pyrethroid resistance.
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Affiliation(s)
- Welbeck A Oumbouke
- London School of Hygiene and Tropical Medicine, Keppel Street, London, UK. .,Vector Control Product Evaluation Centre (VCPEC)/Institut Pierre Richet, 01 BP 1500, Bouaké, Côte d'Ivoire.
| | - Mark Rowland
- London School of Hygiene and Tropical Medicine, Keppel Street, London, UK
| | - Alphonsine A Koffi
- Vector Control Product Evaluation Centre (VCPEC)/Institut Pierre Richet, 01 BP 1500, Bouaké, Côte d'Ivoire
| | - Ludovic P A Alou
- Vector Control Product Evaluation Centre (VCPEC)/Institut Pierre Richet, 01 BP 1500, Bouaké, Côte d'Ivoire
| | - Soromane Camara
- Vector Control Product Evaluation Centre (VCPEC)/Institut Pierre Richet, 01 BP 1500, Bouaké, Côte d'Ivoire
| | - Raphael N'Guessan
- London School of Hygiene and Tropical Medicine, Keppel Street, London, UK.,Vector Control Product Evaluation Centre (VCPEC)/Institut Pierre Richet, 01 BP 1500, Bouaké, Côte d'Ivoire
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31
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Collins E, Vaselli NM, Sylla M, Beavogui AH, Orsborne J, Lawrence G, Wiegand RE, Irish SR, Walker T, Messenger LA. The relationship between insecticide resistance, mosquito age and malaria prevalence in Anopheles gambiae s.l. from Guinea. Sci Rep 2019; 9:8846. [PMID: 31222175 PMCID: PMC6586859 DOI: 10.1038/s41598-019-45261-5] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 05/30/2019] [Indexed: 11/15/2022] Open
Abstract
Insecticide resistance across sub-Saharan Africa may impact the continued effectiveness of malaria vector control. We investigated the association between carbamate and pyrethroid resistance with Anopheles gambiae s.l. parity, Plasmodium falciparum infection, and molecular insecticide resistance mechanisms in Guinea. Pyrethroid resistance was intense, with field populations surviving ten times the insecticidal concentration required to kill susceptible individuals. The L1014F kdr-N1575Y haplotype and I1527T mutation were significantly associated with mosquito survival following permethrin exposure (Prevalence Ratio; PR = 1.92, CI = 1.09–3.37 and PR = 2.80, CI = 1.03–7.64, respectively). Partial restoration of pyrethroid susceptibility following synergist pre-exposure suggests a role for mixed-function oxidases. Carbamate resistance was lower and significantly associated with the G119S Ace-1 mutation. Oocyst rates were 6.8% and 4.2% among resistant and susceptible mosquitoes, respectively; survivors of bendiocarb exposure were significantly more likely to be infected. Pyrethroid resistant mosquitoes had significantly lower parity rates than their susceptible counterparts (PR = 1.15, CI = 1.10–1.21). Our findings emphasize the need for additional studies directly assessing the influence of insecticide resistance on mosquito fitness.
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Affiliation(s)
- Emma Collins
- Department of Disease Control, Faculty of Infectious Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Natasha M Vaselli
- Department of Disease Control, Faculty of Infectious Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Moussa Sylla
- Centre National de Formation et de Recherche en Santé Rurale de Maferinyah, Maferinyah, Guinea
| | - Abdoul H Beavogui
- Centre National de Formation et de Recherche en Santé Rurale de Maferinyah, Maferinyah, Guinea
| | - James Orsborne
- Department of Disease Control, Faculty of Infectious Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Gena Lawrence
- Entomology Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, United States of America
| | - Ryan E Wiegand
- Entomology Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, United States of America
| | - Seth R Irish
- Entomology Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, United States of America.,President's Malaria Initiative, Bureau for Global Health, Office of Infectious Disease, United States Agency for International Development, Washington DC, United States of America
| | - Thomas Walker
- Department of Disease Control, Faculty of Infectious Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Louisa A Messenger
- Entomology Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA, United States of America. .,American Society for Microbiology, 1752 N Street, NW, Washington DC, 20036, United States of America.
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Abstract
Over the past two decades, malaria-related deaths have reduced substantially, especially in African children. However, the global malaria burden still remains high. The recent emergence of resistance to artemisinin, the backbone of malaria management, could threaten malaria control. Importantly, over the past five years, there has been an upsurge in research in the development of novel antimalarial drugs (and combinations), malaria vaccine and new vector-control strategies that can boost the malaria control programme.
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Affiliation(s)
- Ashok K Pannu
- Assistant Professor, Department of Internal Medicine, Post Graduate Institute of Medical Education and Research, Chandigarh, India
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Oumbouke WA, Koffi AA, Alou LPA, Rowland M, N’Guessan R. Evaluation of standard pyrethroid based LNs (MiraNet and MagNet) in experimental huts against pyrethroid resistant Anopheles gambiae s.l. M'bé, Côte d'Ivoire: Potential for impact on vectorial capacity. PLoS One 2019; 14:e0215074. [PMID: 30973948 PMCID: PMC6459542 DOI: 10.1371/journal.pone.0215074] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 03/26/2019] [Indexed: 11/19/2022] Open
Abstract
Background There is evidence from experimental hut and household studies that the entomological efficacy of long lasting pyrethroid treated nets (LLINs) is compromised in areas of pyrethroid resistance. The rapid increase in resistance intensity in African malaria vectors could further undermine the performance of these nets. The pyrethroid resistance intensity in Anopheles gambiae s.l. M’bé from central Côte d’Ivoire is reported to be high (> 1700 fold). Whether this translates into an increase in entomological indicators of malaria transmission needs investigation. Method The efficacy of two long lasting insecticidal nets (LN) MiraNet and MagNet, both alpha-cypermethrin based was evaluated in experimental huts against pyrethroid resistant Anopheles gambiae in M’bé, central Côte d’Ivoire. All nets were deliberately holed to simulate wear-and-tear and were tested unwashed and after 20 standardized washes. Results The entry rates of An. gambiae s.l. into huts with insecticide treated nets were 62–84% lower than entry into huts with untreated nets (p < 0.001). Exit rates of An. gambiae s.l. with unwashed MiraNet and MagNet LNs were significantly greater than with untreated nets (50–60% vs 26%) and this effect after washing 20 times nets did not decrease. Blood-feeding with both nets was significantly inhibited relative to the untreated reference net (31–55%) (p < 0.001). Washing MiraNet LN 20 times had no significant impact on protection against An. gambiae s.l. bites but it did cause a significant fall by 40% in protection with MagNet LN (p < 0.001). All insecticide treated nets induced higher mortality of An. gambiae s.l. than the untreated net (p < 0.05). The impact though significant was limited (14–30%). The personal protection against An. gambiae s.l. bites derived from all treatments was high (75–90%). The overall insecticidal effect was compromised by pyrethroid resistance and was not detectable in some treatments. Conclusion In this area of high pyrethroid resistance intensity (over 1700 fold), both MiraNet and MagNet LNs still conferred appreciable personal protection against mosquito bites despite inducing only slightly greater mortality of pyrethroid resistant Anopheles mosquitoes than untreated nets. The impact is comparable to moderately intense Benin resistance area (207 fold) and Burkina Faso (over 1000 fold). This preserved level of protection plus the small but sensitive killing of mosquitoes may continue to impact vectorial capacity despite high intensity of resistance. Nevertheless, there is an obvious need for strategies and nets with novel mode of action to enhance vector control.
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Affiliation(s)
- Welbeck A. Oumbouke
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, United Kingdom
- Institut Pierre Richet (IPR) / Institut National de Santé Publique (INSP), Bouaké, Côte d’Ivoire
- * E-mail:
| | - Alphonsine A. Koffi
- Institut Pierre Richet (IPR) / Institut National de Santé Publique (INSP), Bouaké, Côte d’Ivoire
| | - Ludovic P. Ahoua Alou
- Institut Pierre Richet (IPR) / Institut National de Santé Publique (INSP), Bouaké, Côte d’Ivoire
| | - Mark Rowland
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Raphael N’Guessan
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, United Kingdom
- Institut Pierre Richet (IPR) / Institut National de Santé Publique (INSP), Bouaké, Côte d’Ivoire
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34
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Strengthening long-lasting insecticidal nets effectiveness monitoring using retrospective analysis of cross-sectional, population-based surveys across sub-Saharan Africa. Sci Rep 2018; 8:17110. [PMID: 30459359 PMCID: PMC6244007 DOI: 10.1038/s41598-018-35353-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 10/25/2018] [Indexed: 02/01/2023] Open
Abstract
Bed nets averted 68% of malaria cases in Africa between 2000 and 2015. However, concerns over insecticide resistance, bed net durability and the effectiveness of long-lasting insecticidal nets (LLIN) are growing. To assess the effectiveness of LLINs of different ages and insecticides against malaria, we conducted a population-based, cross-sectional study using data from 162,963 children younger than 5 years of age participating in 33 Demographic and Health and Malaria Indicator Surveys conducted in 21 countries between 2009 and 2016. We used Bayesian logistic regression to estimate associations between LLIN age, insecticide type, and malaria. Children sleeping under LLINs the previous night experienced 21% lower odds of malaria infection than children who did not (odds ratio [OR] 0.79; 95% Uncertainty Interval [UI] 0.76-0.82). Nets less than one year of age exhibited the strongest protective effect (OR 0.75; 95% UI 0.72-0.79), and protection weakened as net age increased. LLINs containing different insecticides exhibited similar protection (ORdeltamethrin 0.78 [0.75-0.82]; ORpermethrin 0.79 [0.75-0.83]; ORalphacypermethrin 0.85 [0.76-0.94]). Freely-available, population-based surveys can enhance and guide current entomological monitoring amid concerns of insecticide resistance and bed net durability, and be used with locally-collected data to support decisions on LLIN redistribution campaign timing which insecticide to use.
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Camara S, Ahoua Alou LP, Koffi AA, Clegban YCM, Kabran JP, Koffi FM, Koffi K, Pennetier C. Efficacy of Interceptor ® G2, a new long-lasting insecticidal net against wild pyrethroid-resistant Anopheles gambiae s.s. from Côte d'Ivoire: a semi-field trial. ACTA ACUST UNITED AC 2018; 25:42. [PMID: 30088473 PMCID: PMC6082037 DOI: 10.1051/parasite/2018042] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Accepted: 07/19/2018] [Indexed: 11/17/2022]
Abstract
Background: The widespread insecticide resistance in malaria vector populations is a serious threat to the efficacy of vector control tools. As a result, the World Health Organization (WHO) supports the development of alternative tools that combine several insecticides with the aim of improving vector control and the management of insecticide resistance. In the present study, a long-lasting insecticidal net treated with a mixture of chlorfenapyr and alphacypermethrin was evaluated against wild pyrethroid-resistant Anopheles gambiae s.s in M’bé, Côte d’Ivoire. Centers for Disease Control and Prevention (CDC) bottle tests were carried out with resistant An. gambiae s.s. of M’bé and the susceptible strain, to assess the resistance level to chlorfenapyr and alphacypermethrin. Results: CDC bottle bioassays revealed a high level of resistance of An. gambiae s.s. population from M’bé to alphacypermethrin, whereas they revealed low resistance to chlorfenapyr. In experimental huts, Interceptor® G2 that was unwashed or washed 20 times killed 87% and 82% of An. gambiae s.s., respectively, whereas Interceptor® LN that was either unwashed or washed 20 times killed only about 10% of the mosquitoes. The blood-feeding inhibition induced by Interceptor® was not significantly different compared to untreated nets, whereas Interceptor® G2 that was unwashed or washed 20 times induced 42% and 34% inhibition of blood-feeding, respectively. Conclusion: Interceptor® G2 met the WHOPES criteria to undergo a phase III study. Investigation of its efficacy at a community level and the conduct of randomized controlled trials dealing with epidemiological outputs are warranted in order to study the potential of Interceptor® G2 to better protect communities.
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Affiliation(s)
- Soromane Camara
- Institut Pierre Richet/Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire - Université Félix Houphouët-Boigny, Abidjan, Côte d'Ivoire - Institut de Recherche pour le Développement (IRD), Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), UMR 224, Bouaké, Côte d'Ivoire
| | | | | | - Yao Cyntia Muriel Clegban
- Institut Pierre Richet/Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire - Université Félix Houphouët-Boigny, Abidjan, Côte d'Ivoire
| | - Jean-Paul Kabran
- Institut Pierre Richet/Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | - Fernand Mathieu Koffi
- Institut Pierre Richet/Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire
| | - Kouakou Koffi
- Université Félix Houphouët-Boigny, Abidjan, Côte d'Ivoire
| | - Cédric Pennetier
- Institut Pierre Richet/Institut National de Santé Publique (INSP), Bouaké, Côte d'Ivoire - Institut de Recherche pour le Développement (IRD), Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), UMR 224, Bouaké, Côte d'Ivoire
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Akoton R, Tchigossou GM, Djègbè I, Yessoufou A, Atoyebi MS, Tossou E, Zeukeng F, Boko P, Irving H, Adéoti R, Riveron J, Wondji CS, Moutairou K, Djouaka R. Experimental huts trial of the efficacy of pyrethroids/piperonyl butoxide (PBO) net treatments for controlling multi-resistant populations of Anopheles funestus s.s. in Kpomè, Southern Benin. Wellcome Open Res 2018; 3:71. [PMID: 30175242 PMCID: PMC6113884 DOI: 10.12688/wellcomeopenres.14589.1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/06/2018] [Indexed: 01/23/2023] Open
Abstract
Background: Insecticides resistance in
Anopheles mosquitoes limits Long-Lasting Insecticidal Nets (LLIN) used for malaria control in Africa, especially Benin. This study aimed to evaluate the bio-efficacy of current LLINs in an area where
An. funestus s.l. and
An. gambiae have developed multi-resistance to insecticides, and to assess in experimental huts the performance of a mixed combination of pyrethroids and piperonyl butoxide (PBO) treated nets on these resistant mosquitoes. Methods: The study was conducted at Kpomè, Southern Benin. The bio-efficacy of LLINs against
An. funestus and An. gambiae was assessed using the World Health Organization (WHO) cone and tunnel tests. A released/recapture experiment following WHO procedures was conducted to compare the efficacy of conventional LLINs treated with pyrethroids only and LLINs with combinations of pyrethroids and PBO. Prior to huts trials, we confirmed the level of insecticide and PBO residues in tested nets using high performance liquid chromatography (HPLC). Results: Conventional LLINs (Type 2 and Type 4) have the lowest effect against local multi-resistant
An. funestus s.s. and An. coluzzii populations from Kpomè. Conversely, when LLINs containing mixtures of pyrethroids and PBO (Type 1 and Type 3) were introduced in trial huts, we recorded a greater effect against the two mosquito populations (P < 0.0001). Tunnel test with
An. funestus s.s. revealed mortalities of over 80% with this new generation of LLINs (Type 1 and Type 3),while conventional LLINs produced 65.53 ± 8.33% mortalities for Type 2 and 71.25 ±7.92% mortalities for Type 4. Similarly, mortalities ranging from 77 to 87% were recorded with the local populations of
An. coluzzii. Conclusion: This study suggests the reduced efficacy of conventional LLINs (Pyrethroids alone) currently distributed in Benin communities where
Anopheles populations have developed multi-insecticide resistance. The new generation nets (pyrethroids+PBO) proved to be more effective on multi-resistant populations of mosquitoes.
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Affiliation(s)
- Romaric Akoton
- University of Abomey, Calavi, Abomey-Calavi, 526, Benin.,AgroEcoHealth Platform, International Institute of Tropical Agriculture, Cotonou, 0932, Benin
| | - Genevieve M Tchigossou
- University of Abomey, Calavi, Abomey-Calavi, 526, Benin.,AgroEcoHealth Platform, International Institute of Tropical Agriculture, Cotonou, 0932, Benin
| | - Innocent Djègbè
- AgroEcoHealth Platform, International Institute of Tropical Agriculture, Cotonou, 0932, Benin.,National University of Sciences, Technologies, Engineering and Mathematics of Abomey, Abomey, 123, Benin
| | | | - Michael Seun Atoyebi
- AgroEcoHealth Platform, International Institute of Tropical Agriculture, Cotonou, 0932, Benin.,Cell Biology and Genetics Unit, Department of Zoology, University of Ibadan, Ibadan, Nigeria
| | - Eric Tossou
- University of Abomey, Calavi, Abomey-Calavi, 526, Benin.,AgroEcoHealth Platform, International Institute of Tropical Agriculture, Cotonou, 0932, Benin
| | - Francis Zeukeng
- Faculty of Sciences, Department of Biochemistry, University of Yaounde I, Yaounde, 812, Cameroon
| | - Pelagie Boko
- National malaria and Neglected diseases control program, Ministry of Health, Cotonou, Benin
| | - Helen Irving
- Liverpool School of Tropical Medicine, Liverpool, L3 5QA , UK
| | - Razack Adéoti
- AgroEcoHealth Platform, International Institute of Tropical Agriculture, Cotonou, 0932, Benin
| | - Jacob Riveron
- Liverpool School of Tropical Medicine, Liverpool, L3 5QA , UK
| | | | | | - Rousseau Djouaka
- AgroEcoHealth Platform, International Institute of Tropical Agriculture, Cotonou, 0932, Benin
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Protopopoff N, Mosha JF, Lukole E, Charlwood JD, Wright A, Mwalimu CD, Manjurano A, Mosha FW, Kisinza W, Kleinschmidt I, Rowland M. Effectiveness of a long-lasting piperonyl butoxide-treated insecticidal net and indoor residual spray interventions, separately and together, against malaria transmitted by pyrethroid-resistant mosquitoes: a cluster, randomised controlled, two-by-two factorial design trial. Lancet 2018; 391:1577-1588. [PMID: 29655496 PMCID: PMC5910376 DOI: 10.1016/s0140-6736(18)30427-6] [Citation(s) in RCA: 232] [Impact Index Per Article: 38.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/24/2017] [Revised: 02/13/2018] [Accepted: 02/13/2018] [Indexed: 11/29/2022]
Abstract
BACKGROUND Progress in malaria control is under threat by wide-scale insecticide resistance in malaria vectors. Two recent vector control products have been developed: a long-lasting insecticidal net that incorporates a synergist piperonyl butoxide (PBO) and a long-lasting indoor residual spraying formulation of the insecticide pirimiphos-methyl. We evaluated the effectiveness of PBO long-lasting insecticidal nets versus standard long-lasting insecticidal nets as single interventions and in combination with the indoor residual spraying of pirimiphos-methyl. METHODS We did a four-group cluster randomised controlled trial using a two-by-two factorial design of 48 clusters derived from 40 villages in Muleba (Kagera, Tanzania). We randomly assigned these clusters using restricted randomisation to four groups: standard long-lasting insecticidal nets, PBO long-lasting insecticidal nets, standard long-lasting insecticidal nets plus indoor residual spraying, or PBO long-lasting insecticidal nets plus indoor residual spraying. Both standard and PBO nets were distributed in 2015. Indoor residual spraying was applied only once in 2015. We masked the inhabitants of each cluster to the type of nets received, as well as field staff who took blood samples. Neither the investigators nor the participants were masked to indoor residual spraying. The primary outcome was the prevalence of malaria infection in children aged 6 months to 14 years assessed by cross-sectional surveys at 4, 9, 16, and 21 months after intervention. The endpoint for assessment of indoor residual spraying was 9 months and PBO long-lasting insecticidal nets was 21 months. This trial is registered with ClinicalTrials.gov, number NCT02288637. FINDINGS 7184 (68·0%) of 10 560 households were selected for post-intervention survey, and 15 469 (89·0%) of 17 377 eligible children from the four surveys were included in the intention-to-treat analysis. Of the 878 households visited in the two indoor residual spraying groups, 827 (94%) had been sprayed. Reported use of long-lasting insecticidal nets, across all groups, was 15 341 (77·3%) of 19 852 residents after 1 year, decreasing to 12 503 (59·2%) of 21 105 in the second year. Malaria infection prevalence after 9 months was lower in the two groups that received PBO long-lasting insecticidal nets than in the two groups that received standard long-lasting insecticidal nets (531 [29%] of 1852 children vs 767 [42%] of 1809; odds ratio [OR] 0·37, 95% CI 0·21-0·65; p=0·0011). At the same timepoint, malaria prevalence in the two groups that received indoor residual spraying was lower than in groups that did not receive indoor residual spraying (508 [28%] of 1846 children vs 790 [44%] of 1815; OR 0·33, 95% CI 0·19-0·55; p<0·0001) and there was evidence of an interaction between PBO long-lasting insecticidal nets and indoor residual spraying (OR 2·43, 95% CI 1·19-4·97; p=0·0158), indicating redundancy when combined. The PBO long-lasting insecticidal net effect was sustained after 21 months with a lower malaria prevalence than the standard long-lasting insecticidal net (865 [45%] of 1930 children vs 1255 [62%] of 2034; OR 0·40, 0·20-0·81; p=0·0122). INTERPRETATION The PBO long-lasting insecticidal net and non-pyrethroid indoor residual spraying interventions showed improved control of malaria transmission compared with standard long-lasting insecticidal nets where pyrethroid resistance is prevalent and either intervention could be deployed to good effect. As a result, WHO has since recommended to increase coverage of PBO long-lasting insecticidal nets. Combining indoor residual spraying with pirimiphos-methyl and PBO long-lasting insecticidal nets provided no additional benefit compared with PBO long-lasting insecticidal nets alone or standard long-lasting insecticidal nets plus indoor residual spraying. FUNDING UK Department for International Development, Medical Research Council, and Wellcome Trust.
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Affiliation(s)
- Natacha Protopopoff
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London, UK.
| | - Jacklin F Mosha
- National Institute for Medical Research, Mwanza Medical Research Centre, Mwanza, Tanzania
| | - Eliud Lukole
- Pan-African Malaria Vector Research Consortium, Kilimanjaro Christian Medical University College, Moshi, Tanzania
| | - Jacques D Charlwood
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London, UK
| | - Alexandra Wright
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London, UK
| | - Charles D Mwalimu
- Ministry of Health Community Development Gender Elderly and Children, National Malaria Control Program, Dar es Salaam, Tanzania
| | - Alphaxard Manjurano
- National Institute for Medical Research, Mwanza Medical Research Centre, Mwanza, Tanzania
| | - Franklin W Mosha
- Pan-African Malaria Vector Research Consortium, Kilimanjaro Christian Medical University College, Moshi, Tanzania
| | - William Kisinza
- National Institute for Medical Research, Amani Medical Research Centre, Muheza, Tanzania
| | - Immo Kleinschmidt
- MRC Tropical Epidemiology Group, London School of Hygiene & Tropical Medicine, London, UK; School of Pathology, Faculty of Health Sciences, University of Witwatersrand, Johannesburg, South Africa
| | - Mark Rowland
- Department of Disease Control, London School of Hygiene & Tropical Medicine, London, UK
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Thiaw O, Doucouré S, Sougoufara S, Bouganali C, Konaté L, Diagne N, Faye O, Sokhna C. Investigating insecticide resistance and knock-down resistance (kdr) mutation in Dielmo, Senegal, an area under long lasting insecticidal-treated nets universal coverage for 10 years. Malar J 2018; 17:123. [PMID: 29566682 PMCID: PMC5863856 DOI: 10.1186/s12936-018-2276-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2017] [Accepted: 03/15/2018] [Indexed: 11/10/2022] Open
Abstract
Background The use of insecticides, through indoor residual spraying and long-lasting insecticide-treated nets (LLINs), is essential to control malaria vectors. However, the sustainability of these tools is challenged by the spread of insecticide resistance in Anopheles mosquitoes. This study was conducted to assess the susceptibility to insecticides and to determine the resistance mechanisms in malaria vectors in Dielmo, a rural area of western Senegal where LLINs were introduced a decade ago. Methods CDC bottle bioassays were used to determine the susceptibility of 2–5 day-old unfed Anopheles gambiae s.l. females to alphacypermethrin (12.5 µg/bottle), deltamethrin (12.5 µg/bottle), etofenprox (12.5 µg/bottle), lambdacyhalothrin (12.5 µg/bottle), permethrin (21.5 µg/bottle), DDT (100 µg/bottle), bendiocarb (12.5 µg/bottle), pirimiphos-methyl (20 µg/bottle) and fenitrothion (50 µg/bottle). The involvement of glutathione-S-transferases (GSTs) in insecticide resistance was assessed using a synergist, etacrynic acid (EA, 80 µg/bottle). Polymerase chain reaction (PCR) was used to investigate the presence of ‘knock-down resistance (kdr)’ mutation and to identify sibling species within the An. gambiae complex. Results CDC bottle bioassays showed that mosquitoes were fully susceptible to lambdacyhalothrin, bendiocarb and fenitrothion. Overall, mortality rates of 97, 94.6, 93.5, 92.1, and 90.1% were, respectively, observed for permethrin, deltamethrin, pirimiphos-methyl, etofenprox and alphacypermethrin. Resistance to DDT was observed, with a mortality rate of 62%. The use of EA significantly improved the susceptibility of An. gambiae s.l. to DDT by inhibiting GSTs (p = 0.03). PCR revealed that Anopheles arabiensis was the predominant species (91.3%; IC 95 86.6–94%) within An. gambiae complex from Dielmo, followed by Anopheles coluzzii (5.4%; IC 95 2.7–8.1%) and Anopheles gambiae s.s. (3.3%; IC 95 0.6–5.9%). Both 1014F and 1014S alleles were found in An. arabiensis population with frequencies of 0.08 and 0.361, respectively, and 0.233 and 0.133, respectively in An. coluzzii. In An. gambiae s.s. population, only kdr L1014F mutation was detected, with a frequency of 0.167. It was observed that some individual mosquitoes carried both alleles, with 19 specimens recorded for An. arabiensis and 2 for An. coluzzii. The presence of L1014F and L1014S alleles were not associated with resistance to pyrethroids and DDT in An. arabiensis. Conclusions The co-occurrence of 1014F and 1014S alleles and the probable involvement of GSTs enzymes in insecticide resistance in An. gambiae s.l. should prompt the local vector programme to implement non-pyrethroid/DDT insecticides alternatives.
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Affiliation(s)
- Omar Thiaw
- UMR Vecteurs-Infections Tropicales et Méditerranéennes (VITROME), Campus International UCAD-IRD Hann Maristes, Dakar, Senegal.,Laboratoire d'Ecologie Vectorielle et Parasitaire (LEVP), Faculté des Sciences et Techniques (FST), Université Cheikh Anta Diop (UCAD), Dakar, Senegal
| | - Souleymane Doucouré
- UMR Vecteurs-Infections Tropicales et Méditerranéennes (VITROME), Campus International UCAD-IRD Hann Maristes, Dakar, Senegal
| | - Seynabou Sougoufara
- UMR Vecteurs-Infections Tropicales et Méditerranéennes (VITROME), Campus International UCAD-IRD Hann Maristes, Dakar, Senegal
| | - Charles Bouganali
- UMR Vecteurs-Infections Tropicales et Méditerranéennes (VITROME), Campus International UCAD-IRD Hann Maristes, Dakar, Senegal
| | - Lassana Konaté
- Laboratoire d'Ecologie Vectorielle et Parasitaire (LEVP), Faculté des Sciences et Techniques (FST), Université Cheikh Anta Diop (UCAD), Dakar, Senegal
| | - Nafissatou Diagne
- UMR Vecteurs-Infections Tropicales et Méditerranéennes (VITROME), Campus International UCAD-IRD Hann Maristes, Dakar, Senegal
| | - Ousmane Faye
- Laboratoire d'Ecologie Vectorielle et Parasitaire (LEVP), Faculté des Sciences et Techniques (FST), Université Cheikh Anta Diop (UCAD), Dakar, Senegal
| | - Cheikh Sokhna
- UMR Vecteurs-Infections Tropicales et Méditerranéennes (VITROME), Campus International UCAD-IRD Hann Maristes, Dakar, Senegal.
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Use of Insecticide-Treated Mosquito Net among Pregnant Women and Guardians of Children under Five in the Democratic Republic of the Congo. Malar Res Treat 2017; 2017:5923696. [PMID: 29234551 PMCID: PMC5694996 DOI: 10.1155/2017/5923696] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2017] [Revised: 08/26/2017] [Accepted: 09/05/2017] [Indexed: 11/17/2022] Open
Abstract
Background Insecticide-treated mosquito nets (ITNs) are one of the most effective tools for preventing malaria in sub-Saharan Africa. Objective This study examined knowledge, attitude, and practice on the use of ITNs in the prevention of malaria among pregnant women and guardians of children under five in the Democratic Republic of the Congo. Methods A total of 5,138 pregnant women and guardians of children under five were interviewed. Results The majority of participants (>80%) knew the signs and symptoms of malaria; 81.6% reported having an ITN in the household, but 78.4% reported using it the night before the interview. Only 71.4% of pregnant women used ITN the night compared to 68.2% of children under five. In the Logistic Regression model, women who believed that it is normal to use ITNs were 1.9 times more likely to use it than those who did not (OR: 1.930); women who were confident in their abilities to use ITNs were 1.9 times more likely than those who were not confident (OR: 1.915); and women who had a good attitude towards ITNs were also more likely to use ITNs compared to those who did not (OR: 1.529). Conclusion New and innovative evidence-based behavior change interventions are needed to increase the utilization of ITNs among vulnerable groups.
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40
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Ranson H. Current and Future Prospects for Preventing Malaria Transmission via the Use of Insecticides. Cold Spring Harb Perspect Med 2017; 7:a026823. [PMID: 28507193 PMCID: PMC5666625 DOI: 10.1101/cshperspect.a026823] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Malaria vectors have developed resistance to all classes of insecticides that are used to target the adult mosquito to prevent parasite transmission. The number of resistant mosquito populations has increased dramatically in recent years, most likely as a result of the scale-up of vector control activities, and the intensity of this resistance is increasing rapidly and compromising the performance of vector control tools. Bednets and indoor residual spray formulations containing alternative active ingredients have shown promise in field trials but are still several years away from implementation. As existing insecticides become less effective at killing mosquitoes in the countries with the highest burden of malaria, there is growing concern that the advances made in reducing malaria transmission will be eroded by insecticide resistance. The likelihood of this scenario, and strategies that may help mitigate against this, are reviewed below.
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Affiliation(s)
- Hilary Ranson
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool L3 5QA, United Kingdom
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Chaumeau V, Cerqueira D, Zadrozny J, Kittiphanakun P, Andolina C, Chareonviriyaphap T, Nosten F, Corbel V. Insecticide resistance in malaria vectors along the Thailand-Myanmar border. Parasit Vectors 2017; 10:165. [PMID: 28359289 PMCID: PMC5374572 DOI: 10.1186/s13071-017-2102-z] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Accepted: 03/23/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND There is a paucity of data about the susceptibility status of malaria vectors to Public Health insecticides along the Thailand-Myanmar border. This lack of data is a limitation to guide malaria vector-control in this region. The aim of this study was to assess the susceptibility status of malaria vectors to deltamethrin, permethrin and DDT and to validate a simple molecular assay for the detection of knock-down resistance (kdr) mutations in the study area. METHODS Anopheles mosquitoes were collected in four sentinel villages during August and November 2014 and July 2015 using human landing catch and cow bait collection methods. WHO susceptibility tests were carried out to measure the mortality and knock-down rates of female mosquitoes to deltamethrin (0.05%), permethrin (0.75%) and DDT (4%). DNA sequencing of a fragment of the voltage-gated sodium channel gene was carried out to identify knock-down resistance (kdr) mutations at position 1014 in mosquitoes surviving exposure to insecticides. RESULTS A total of 6295 Anopheles belonging to ten different species were bioassayed. Resistance or suspected resistance to pyrethroids was detected in An. barbirostris (s.l.) (72 and 84% mortality to deltamethrin (n = 504) and permethrin (n = 493) respectively), An. hyrcanus (s.l.) (33 and 48% mortality to deltamethrin (n = 172) and permethrin (n = 154), respectively), An. jamesii (87% mortality to deltamethrin, n = 111), An. maculatus (s.l.) (85 and 97% mortality to deltamethrin (n = 280) and permethrin (n = 264), respectively), An. minimus (s.l.) (92% mortality, n = 370) and An. vagus (75 and 95% mortality to deltamethrin (n =148) and permethrin (n = 178), respectively). Resistance or suspected resistance to DDT was detected in An. barbirostris (s.l.) (74% mortality, n = 435), An. hyrcanus (s.l.) (57% mortality, n = 91) and An. vagus (97% mortality, n = 133). The L1014S kdr mutation at both heterozygous and homozygous state was detected only in An. peditaeniatus (Hyrcanus Group). CONCLUSION Resistance to pyrethroids is present along the Thailand-Myanmar border, and it represents a threat for malaria vector control. Further investigations are needed to better understand the molecular basis of insecticide resistance in malaria vectors in this area.
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Affiliation(s)
- Victor Chaumeau
- Centre hospitalier universitaire de Montpellier, Montpellier, France. .,Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle, Institut de Recherche pour le Développement, Montpellier, France. .,Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand. .,Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand.
| | - Dominique Cerqueira
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand
| | - John Zadrozny
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand
| | - Praphan Kittiphanakun
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - Chiara Andolina
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | | | - François Nosten
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Vincent Corbel
- Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle, Institut de Recherche pour le Développement, Montpellier, France. .,Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand.
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WHO cone bio-assays of classical and new-generation long-lasting insecticidal nets call for innovative insecticides targeting the knock-down resistance mechanism in Benin. Malar J 2017; 16:77. [PMID: 28202024 PMCID: PMC5312429 DOI: 10.1186/s12936-017-1727-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Accepted: 02/07/2017] [Indexed: 11/10/2022] Open
Abstract
Background To increase the effectiveness of insecticide-treated nets (ITN) in areas of high resistance, new long-lasting insecticidal nets (LLINs) called new-generation nets have been developed. These nets are treated with the piperonyl butoxide (PBO) synergist which inhibit the action of detoxification enzymes. The effectiveness of the new-generation nets has been proven in some studies, but their specific effect on mosquitoes carrying detoxification enzymes and those carrying both detoxification enzymes and the knock-down resistance gene in Benin is not well known. Thus, the objective of this study is to evaluate the efficacy of LLINs treated with PBO on multi-resistant Anopheles gambiae s.l. Methods The study occurred in seven cities in Benin, Abomey, Cotonou, Porto-Novo, Zangnanado, Parakou, Malanville and Tanguiéta, and included ten locations selected on a north–south transect. Mosquito larvae were collected from these sites, and adult females from these larvae were exposed to single-pyrethroid-treated nets (LifeNet, PermaNet 2.0, Olyset Net) and bi-treated nets (PermaNet 3.0 and Olyset Plus) based on their level of resistance and using WHO cone tests following WHO guidelines. Results The different LLINs showed 100% mortality of the susceptible laboratory strain Kisumu and the resistant strain Ace-1R Kisumu. However, with the resistant laboratory strain kdr-Kisumu, mortality was low (16–32%) for all LLINs except PermaNet 3.0 (82.9%). The mortality of local strains carrying only the kdr mechanism varied from 0 to 47% for the single-pyrethroid-treated LLINs and 9 to 86% for bi-treated LLINs. With local strains carrying several mechanisms of resistance (kdr + detoxification enzymes), the observed mortality with different LLINs was also low except for PermaNet 3.0, which induced significantly higher mortality, usually greater than 75% (p < 0.001), with multi-resistant strains. The inhibition of the mortalities induced by the LLINs (11–96%) on multi-resistant field populations was similar to the inhibition observed with the laboratory strain carrying only the knock-down resistance mechanism (kdr-Kisumu) (p > 0.05). Conclusion This study showed that the new-generation LLINs treated with pyrethroids and PBO showed better efficacy compared to conventional LLINs. Although the addition of PBO significantly increased the mortality of mosquitoes, the significant role of the kdr resistance gene in the low efficacy of LLINs calls for LLIN technology innovation that specifically targets this mechanism.
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N’Guessan R, Odjo A, Ngufor C, Malone D, Rowland M. A Chlorfenapyr Mixture Net Interceptor® G2 Shows High Efficacy and Wash Durability against Resistant Mosquitoes in West Africa. PLoS One 2016; 11:e0165925. [PMID: 27851828 PMCID: PMC5112870 DOI: 10.1371/journal.pone.0165925] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 09/22/2016] [Indexed: 11/18/2022] Open
Abstract
Background Malaria control through use of long-lasting insecticidal nets (LN) is threatened by the selection of anopheline mosquitoes strongly resistant to pyrethroid insecticides. To sustain future effectiveness it is essential to identify and evaluate novel insecticides suitable for nets. Mixtures of two insecticides with contrasting mode of action have the potential to kill resistant vectors and restore transmission control provided the formulation can withstand regular washing over the net’s life span. Method The efficacy of a novel mixture LN, Interceptor® G2, that combines the pyrrole chlorfenapyr and pyrethroid alpha-cypermethrin was evaluated under controlled household conditions (experimental hut trial) and by laboratory bioassay against pyrethroid resistant An. gambiae in Benin before and after standardized washing. Comparison arms included standard alpha-cypermethrin LN, nets hand-treated with chlorfenapyr-only and untreated nets. Results The chlorfenapyr-alphacypermethrin LN demonstrated improved efficacy and wash resistance compared to a standard alpha-cypermethrin LN against pyrethroid resistant mosquitoes (resistance ratio 207). In experimental hut trial alpha-cypermethrin LN killed only 20% (95% CI 15–26%) of host-seeking An. gambiae whilst mixture LN killed 71% (95% CI 65–77%). Mixture LN washed 20 times killed 65% (95% CI 58–71%), and thus intensive washing reduced efficacy by only 6% (95% CI 1.3–11%). The chlorfenapyr net killed 76% (95% CI 70–81%). Personal protection and blood feeding inhibition did not differ between mixture and pyrethroid LN; however, the mixture LN was 2.5 (95% CI: 2.1–3.1) times more protective than untreated nets. Standard WHO cone bioassays conducted during day time hours failed to anticipate field efficacy but overnight tunnel tests successfully predicted mixture LN and chlorfenapyr net efficacy in field trials. Conclusion Interceptor® G2 LN demonstrates the potential to control transmission and provide community protection over the normal lifespan of long lasting nets where standard pyrethroid LN show signs of failing due to resistance.
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Affiliation(s)
- Raphael N’Guessan
- London School of Hygiene and Tropical Medicine, London, United Kingdom
- Centre de Recherche Entomologique de Cotonou, Ministry of Health, Cotonou, Benin
- Pan-African Malaria Vector Research Consortium (PAMVERC), London, United Kingdom
| | - Abibatou Odjo
- Centre de Recherche Entomologique de Cotonou, Ministry of Health, Cotonou, Benin
| | - Corine Ngufor
- London School of Hygiene and Tropical Medicine, London, United Kingdom
- Centre de Recherche Entomologique de Cotonou, Ministry of Health, Cotonou, Benin
- Pan-African Malaria Vector Research Consortium (PAMVERC), London, United Kingdom
| | - David Malone
- Innovative Vector Control Consortium, Liverpool, United Kingdom
| | - Mark Rowland
- London School of Hygiene and Tropical Medicine, London, United Kingdom
- Pan-African Malaria Vector Research Consortium (PAMVERC), London, United Kingdom
- * E-mail:
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Lynch PA, Boots M. Using evolution to generate sustainable malaria control with spatial repellents. eLife 2016; 5. [PMID: 27776220 PMCID: PMC5089865 DOI: 10.7554/elife.15416] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2016] [Accepted: 09/13/2016] [Indexed: 11/24/2022] Open
Abstract
Evolution persistently undermines vector control programs through insecticide resistance. Here we propose a novel strategy which instead exploits evolution to generate and sustain new control tools. Effective spatial repellents are needed to keep vectors out of houses. Our approach generates such new repellents by combining a high-toxicity insecticide with a candidate repellent initially effective against only part of the vector population. By killing mosquitoes that enter treated properties the insecticide selects for vector phenotypes deflected by the repellent, increasing efficacy of the repellent against the target vector population and in turn protecting the insecticide against the spread of insecticide resistance. Using such evolved spatial repellents offers an evolutionarily sustainable, ‘double-dip’ system of disease control combining mortality and repellence. We formalize this idea using models which explore vector population genetics and disease transmission probabilities and show that using evolved spatial repellents is theoretically achievable, effective and sustainable. DOI:http://dx.doi.org/10.7554/eLife.15416.001 Many of the mosquito species that transmit malaria have evolved to bite humans indoors at night, and therefore health programs target them using insecticides sprayed on surfaces inside people’s homes. This strategy, however, stops working when mosquito populations evolve to resist the insecticide used, either because they are immune to its poisonous effects or because they change their behaviour to avoid it. Consequently, there is now a need to develop alternative strategies to control mosquitoes that are more sustainable in the face of evolution. One possibility is repellents that keep mosquitoes out of homes. Lynch and Boots have now asked whether evolution could be used to create effective repellents from substances that initially repel only part of the mosquito population by pairing them with lethal insecticides sprayed inside people’s homes. Mathematical models showed that, before insecticide resistance becomes widespread, this “evolved repellence” approach could reduce the spread of malaria by a similar amount to using insecticides alone. This was particularly true if the models considered that, as well as surviving to give fewer infectious bites, repelled infectious mosquitoes may be less likely to transmit malaria with each feed, for example if they feed more on livestock rather than humans. The models of Lynch and Boots also show that that the success of the evolved repellence concept in a given location depends on a number of factors. The proportion of the starting mosquito population that is repelled or resistant can have a large effect. Similarly, success will also depend on how likely normal, repelled and insecticide-resistant mosquitoes are to reproduce successfully. These values can be influenced by the choice of insecticide and repellent and how the chemicals are applied. Lynch and Boots show that swapping insecticides can allow an evolved repellent to be established where it would otherwise not succeed. Also, the spread of resistance to the paired insecticide is slowed or prevented when the mosquito population evolves to be repelled. Practical laboratory and field- work is now needed to build on this theoretical groundwork and to determine suitable locations and application strategies to exploit this concept as a way to sustainably reduce the spread of malaria in the future. DOI:http://dx.doi.org/10.7554/eLife.15416.002
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Affiliation(s)
- Penelope Anne Lynch
- Department of Biosciences, University of Exeter, Cornwall Campus, Penryn, United Kingdom
| | - Mike Boots
- Department of Biosciences, University of Exeter, Cornwall Campus, Penryn, United Kingdom.,Department of Integrative Biology, University of California, Berkeley, United States
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Krezanoski PJ. Delivering insecticide-treated nets for malaria prevention: innovative strategies. Res Rep Trop Med 2016; 7:39-47. [PMID: 30050338 PMCID: PMC6028060 DOI: 10.2147/rrtm.s83173] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The wide-scale adoption of insecticide-treated nets (ITNs) has led to significant reductions in malaria morbidity and mortality worldwide. Delivery of ITNs to the 3.2 billion people at risk of malaria requires multiple steps in diverse settings. The effectiveness of the delivery of ITNs in order to prevent malaria relies on activities that include ITN manufacturing and design, integration into national and international malaria prevention policies, supplying and distributing ITNs to households and individuals, and, finally, programs focused on spurring demand for and use of ITNs by individuals at risk. This paper reviews some recent innovative strategies for ITN delivery across these four domains, places these innovations within the context of the history of ITN deployment, and identifies opportunities to further improve the effectiveness of this ubiquitous public health tool.
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Affiliation(s)
- Paul J Krezanoski
- Department of Medicine.,Department of Pediatrics, Massachusetts General Hospital.,Medicine and Pedatrics, Harvard Medical School, Boston, MA, USA
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Mtove G, Mugasa JP, Messenger LA, Malima RC, Mangesho P, Magogo F, Plucinski M, Hashimu R, Matowo J, Shepard D, Batengana B, Cook J, Emidi B, Halasa Y, Kaaya R, Kihombo A, Lindblade KA, Makenga G, Mpangala R, Mwambuli A, Mzava R, Mziray A, Olang G, Oxborough RM, Seif M, Sambu E, Samuels A, Sudi W, Thomas J, Weston S, Alilio M, Binkin N, Gimnig J, Kleinschmidt I, McElroy P, Moulton LH, Norris L, Ruebush T, Venkatesan M, Rowland M, Mosha FW, Kisinza WN. The effectiveness of non-pyrethroid insecticide-treated durable wall lining to control malaria in rural Tanzania: study protocol for a two-armed cluster randomized trial. BMC Public Health 2016; 16:633. [PMID: 27456339 PMCID: PMC4960851 DOI: 10.1186/s12889-016-3287-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2016] [Accepted: 07/09/2016] [Indexed: 11/16/2022] Open
Abstract
Background Despite considerable reductions in malaria achieved by scaling-up long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS), maintaining sustained community protection remains operationally challenging. Increasing insecticide resistance also threatens to jeopardize the future of both strategies. Non-pyrethroid insecticidetreated wall lining (ITWL) may represent an alternate or complementary control method and a potential tool to manage insecticide resistance. To date no study has demonstrated whether ITWL can reduce malaria transmission nor provide additional protection beyond the current best practice of universal coverage (UC) of LLINs and prompt case management. Methods/design A two-arm cluster randomized controlled trial will be conducted in rural Tanzania to assess whether non-pyrethroid ITWL and UC of LLINs provide added protection against malaria infection in children, compared to UC of LLINs alone. Stratified randomization based on malaria prevalence will be used to select 22 village clusters per arm. All 44 clusters will receive LLINs and half will also have ITWL installed on interior house walls. Study children, aged 6 months to 11 years old, will be enrolled from each cluster and followed monthly to estimate cumulative incidence of malaria parasitaemia (primary endpoint), time to first malaria episode and prevalence of anaemia before and after intervention. Entomological inoculation rate will be estimated using indoor CDC light traps and outdoor tent traps followed by detection of Anopheles gambiae species, sporozoite infection, insecticide resistance and blood meal source. ITWL bioefficacy and durability will be monitored using WHO cone bioassays and household surveys, respectively. Social and cultural factors influencing community and household ITWL acceptability will be explored through focus-group discussions and in-depth interviews. Cost-effectiveness, compared between study arms, will be estimated per malaria case averted. Discussion This protocol describes the large-scale evaluation of a novel vector control product, designed to overcome some of the known limitations of existing methods. If ITWL is proven to be effective and durable under field conditions, it may warrant consideration for programmatic implementation, particularly in areas with long transmission seasons and where pyrethroid-resistant vectors predominate. Trial findings will provide crucial information for policy makers in Tanzania and other malaria-endemic countries to guide resource allocations for future control efforts. Trial registration NCT02533336 registered on 13 July 2014.
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Affiliation(s)
- George Mtove
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania.
| | - Joseph P Mugasa
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Louisa A Messenger
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK
| | - Robert C Malima
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Peter Mangesho
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Franklin Magogo
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Mateusz Plucinski
- US President's Malaria Initiative, Atlanta, GA, USA.,Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Ramadhan Hashimu
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | | | - Donald Shepard
- National Institute for Medical Research, Headquarters, Dar es Salaam, Tanzania
| | - Bernard Batengana
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Jackie Cook
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK
| | - Basiliana Emidi
- Kilimanjaro Christian Medical College, Moshi, Tanzania.,National Institute for Medical Research, Headquarters, Dar es Salaam, Tanzania
| | - Yara Halasa
- Brandeis University, Heller School, Waltham, Massachusetts, USA
| | - Robert Kaaya
- Kilimanjaro Christian Medical College, Moshi, Tanzania
| | - Aggrey Kihombo
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Kimberly A Lindblade
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Geofrey Makenga
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Robert Mpangala
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Abraham Mwambuli
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Ruth Mzava
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Abubakary Mziray
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - George Olang
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | | | - Mohammed Seif
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Edward Sambu
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Aaron Samuels
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Wema Sudi
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - John Thomas
- Phoenix Ordinary LLC, Bridgewater, New Jersey, USA
| | - Sophie Weston
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK
| | - Martin Alilio
- President's Malaria Initiative, United States Agency for International Development, Washington DC, USA
| | - Nancy Binkin
- Translating Research into Action Project (TRAction) University Research Co., LLC, Bethesda, Maryland, USA
| | - John Gimnig
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Immo Kleinschmidt
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK
| | - Peter McElroy
- US President's Malaria Initiative, Atlanta, GA, USA.,Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Lawrence H Moulton
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Laura Norris
- President's Malaria Initiative, United States Agency for International Development, Washington DC, USA
| | - Trenton Ruebush
- Translating Research into Action Project (TRAction) University Research Co., LLC, Bethesda, Maryland, USA
| | - Meera Venkatesan
- President's Malaria Initiative, United States Agency for International Development, Washington DC, USA
| | - Mark Rowland
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK
| | | | - William N Kisinza
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
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47
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Gunasekaran K, Sahu SS, Vijayakumar T, Subramanian S, Yadav RS, Pigeon O, Jambulingam P. An experimental hut evaluation of Olyset Plus, a long-lasting insecticidal net treated with a mixture of permethrin and piperonyl butoxide, against Anopheles fluviatilis in Odisha State, India. Malar J 2016; 15:375. [PMID: 27439398 PMCID: PMC4955161 DOI: 10.1186/s12936-016-1424-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2016] [Accepted: 07/04/2016] [Indexed: 11/12/2022] Open
Abstract
Background Fast development of pyrethroid resistance in malaria vectors prompted the development of new vector control tools including combination of insecticides with different modes of action as part of resistance management strategies. Olyset Plus® is a new long-lasting insecticidal net, in which, permethrin and a synergist, piperonyl butoxide (PBO), are incorporated into filaments. Mixture nets such as this may have application against resistant mosquitoes, particularly those whose resistance is based on oxidative metabolism. There may also be enhanced activity against susceptible mosquitoes since mixed function oxidases are involved in a many metabolic activities including activation to form bioactive compounds. Methods Bio-efficacy of Olyset Plus was evaluated against susceptible malaria vector, Anopheles fluviatilis in experimental huts. Deterrence, blood feeding inhibition, induced exophily and killing effect were measured to assess the bio-efficacy. The results were compared with Olyset Net®, a polyethylene permethrin-incorporated LLIN and a conventionally treated polyester net (with permethrin) washed to just before exhaustion. Results Results showed significant reduction in entry (treatment: 0.4–0.8; control: 4.2 per trap-night) and increase in exit (56.3–82.9 % and 44.2 %) rates of Anopheles fluviatilis in the treatment arms compared to control (P < 0.05). While blood feeding rates declined in treatment arms (18.8–30.6 %), it increased in control (77.6 %) (P < 0.05). This was further evident from the blood-feeding inhibition rates in treatment arms (60.6–90.6 %). Total mortality was significantly higher in all treatment arms (96.3–100 %) compared to control arm (2 %) (P < 0.05). Chemical analysis for active ingredient (AI) showed retention of 75 and 88 % in Olyset plus and Olyset net respectively after 20 washes. Performance of Olyset Plus washed 20 times was equal to the CTN and Olyset Net against the susceptible malaria vector An. fluviatilis, fulfilling the WHO efficacy criteria of Phase II evaluation for LLIN. However, the benefit of incorporating PBO and permethrin together in a long-lasting treatment could not be demonstrated in the current study as the target vector species was fully susceptible to pyrethroids. Conclusion Olyset Plus, with its intrinsic bio-efficacy could be an effective vector control tool to prevent transmission of malaria by susceptible vectors like An. fluviatilis. However, the results of the current study need to be further supported by testing the net at village level (Phase III) for community acceptability. Before taking the net to village level, it needs to be verified whether the net is better than pyrethroid nets in terms of bio-efficacy against resistant An. culicifacies, another malaria vector that has developed resistance to synthetic pyrethroids in India.
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Affiliation(s)
- Kasinathan Gunasekaran
- Vector Control Research Centre (ICMR), Medical Complex, Indira Nagar, Puducherry, 605 006, India.
| | - Sudhansu Sekhar Sahu
- Vector Control Research Centre (ICMR), Medical Complex, Indira Nagar, Puducherry, 605 006, India.
| | - Tharmalingam Vijayakumar
- Vector Control Research Centre (ICMR), Medical Complex, Indira Nagar, Puducherry, 605 006, India
| | - Swaminathan Subramanian
- Vector Control Research Centre (ICMR), Medical Complex, Indira Nagar, Puducherry, 605 006, India
| | - Rajpal Singh Yadav
- World Health Organization Pesticide Evaluation Scheme, Department of Control of Neglected Tropical Diseases, WHO, Geneva, Switzerland
| | - Olivier Pigeon
- Agriculture and Natural Environment Department (D3), Walloon Agricultural Research Centre (CRA-W), Gembloux, Belgium
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48
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Yahouédo GA, Cornelie S, Djègbè I, Ahlonsou J, Aboubakar S, Soares C, Akogbéto M, Corbel V. Dynamics of pyrethroid resistance in malaria vectors in southern Benin following a large scale implementation of vector control interventions. Parasit Vectors 2016; 9:385. [PMID: 27378358 PMCID: PMC4932690 DOI: 10.1186/s13071-016-1661-8] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2016] [Accepted: 06/22/2016] [Indexed: 01/13/2023] Open
Abstract
Background Large-scale implementation of Indoor Residual Spraying and Insecticide Treated Nets has been implemented in Plateau Department, Benin between 2011 and 2014. The purpose of this study was to monitor the frequency and mechanisms of pyrethroid resistance in malaria vectors following the implementation of vector control tools for malaria prevention. Methods Anopheles larvae were collected in 13 villages twice a year from 2012 to 2014. WHO tube tests were used to assess the phenotypic resistance of each population to 0.05 % deltamethrin. Sibling species within Anopheles gambiae complex were identified by PCR techniques. Taqman and biochemical assays were performed to identify the presence of kdr mutations in individual mosquitoes and to detect any increase in the activity of enzymes putatively involved in insecticide metabolism (oxidases, esterase and glutathione-S-transferases). Quantitative real time PCR was used to measure the expression of three metabolic genes involved in pyrethroid resistance (CYP6P3, CYP6M2 and GSTD3). Results Anopheles populations showed < 90 % mortality to deltamethrin in all villages and at all time points. The 1014 F kdr allele frequency was close to fixation (> 0.9) over the sampling periods in both An. gambiae and An. coluzzii. Biochemical assays showed higher activities of alpha esterase and GST in field malaria vector populations compared to susceptible mosquitoes. qPCR assays showed a significant increase of CYP6P3, CYP6M2 GSTD3 expression in An. gambiae after a three-year implementation of LLINs. Conclusion The study confirmed that deltamethrin resistance is widespread in malaria vectors in Southern Benin. We suspect that the increase in deltamethrin resistance between 2012 and 2014 resulted from an increased expression of metabolic detoxification genes (CYP6M2 and CYP6P3) rather than from kdr mutations. It is urgent to evaluate further the impact of metabolic resistance on the efficacy of vector control interventions using pyrethroid insecticides.
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Affiliation(s)
- Gildas A Yahouédo
- Institut de Recherche pour le Développement (IRD), Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), UMR UM1-UM2 - CNRS 5290 - IRD 224, Montpellier, France. .,Centre de Recherche Entomologique de Cotonou (CREC), Cotonou, Bénin.
| | - Sylvie Cornelie
- Institut de Recherche pour le Développement (IRD), Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), UMR UM1-UM2 - CNRS 5290 - IRD 224, Montpellier, France.,Centre de Recherche Entomologique de Cotonou (CREC), Cotonou, Bénin
| | - Innocent Djègbè
- Institut de Recherche pour le Développement (IRD), Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), UMR UM1-UM2 - CNRS 5290 - IRD 224, Montpellier, France.,Centre de Recherche Entomologique de Cotonou (CREC), Cotonou, Bénin
| | - Justine Ahlonsou
- Centre de Recherche Entomologique de Cotonou (CREC), Cotonou, Bénin
| | - Sidick Aboubakar
- Centre de Recherche Entomologique de Cotonou (CREC), Cotonou, Bénin
| | | | - Martin Akogbéto
- Centre de Recherche Entomologique de Cotonou (CREC), Cotonou, Bénin
| | - Vincent Corbel
- Institut de Recherche pour le Développement (IRD), Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), UMR UM1-UM2 - CNRS 5290 - IRD 224, Montpellier, France.,Department of Entomology, Faculty of Agriculture, Kasetsart University, 50 Ngam Wong Wan Rd, Lat Yao Chatuchak, Bangkok, 10900, Thailand
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49
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Vantaux A, Ouattarra I, Lefèvre T, Dabiré KR. Effects of larvicidal and larval nutritional stresses on Anopheles gambiae development, survival and competence for Plasmodium falciparum. Parasit Vectors 2016; 9:226. [PMID: 27107591 PMCID: PMC4842262 DOI: 10.1186/s13071-016-1514-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 04/15/2016] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Many studies have shown that the environment in which larvae develop can influence adult characteristics with consequences for the transmission of pathogens. We investigated how two environmental stresses (larviciding and nutritional stress) interact to affect Anopheles gambiae (previously An. gambiae S molecular form) life history traits and its susceptibility for field isolates of its natural malaria agent Plasmodium falciparum. METHODS Larvae were reared in the presence or not of a sub-lethal concentration of larvicide and under a high and low food regimen. Development time, individual size, adult survival and competence for P. falciparum were assessed. RESULTS Individuals under low food regimen took more time to develop, had a lower development success and were smaller while there was no main effect of larvicide exposure on these traits. However, larvicide exposure impacted individual size in interaction with nutritional stress. Female survival was affected by the interaction between gametocytemia, parasite exposure and larval diet, as well as the interaction between gametocytemia, parasite exposure and larvicidal stress, and the interaction between gametocytemia, larvicidal exposure and larval diet. Among the 951 females dissected 7 days post-infection, 559 (58.78%) harboured parasites. Parasite prevalence was significantly affected by the interaction between larvicidal stress and larval diet. Indeed, females under low food regimen had a higher prevalence than females under high food regimen and this difference was greater under larvicidal stress. The two stresses did not impact parasite intensity. CONCLUSIONS We found that larval nutritional and larvicidal stresses affect mosquito life history traits in complex ways, which could greatly affect P. falciparum transmission. Further studies combining field-based trials on larvicide use and mosquito experimental infections would give a more accurate understanding of the effects of this vector control tool on malaria transmission.
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Affiliation(s)
- Amélie Vantaux
- MIVEGEC (Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle), UMR IRD 224-CNRS 5290-Université de Montpellier, Montpellier, France. .,Institut de Recherche en Sciences de la Santé (IRSS), Bobo Dioulasso, Burkina Faso.
| | - Issiaka Ouattarra
- Institut de Recherche en Sciences de la Santé (IRSS), Bobo Dioulasso, Burkina Faso
| | - Thierry Lefèvre
- MIVEGEC (Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle), UMR IRD 224-CNRS 5290-Université de Montpellier, Montpellier, France.,Institut de Recherche en Sciences de la Santé (IRSS), Bobo Dioulasso, Burkina Faso
| | - Kounbobr Roch Dabiré
- Institut de Recherche en Sciences de la Santé (IRSS), Bobo Dioulasso, Burkina Faso.,Centre Muraz, Bobo Dioulasso, Burkina Faso
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50
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Etang J, Pennetier C, Piameu M, Bouraima A, Chandre F, Awono-Ambene P, Marc C, Corbel V. When intensity of deltamethrin resistance in Anopheles gambiae s.l. leads to loss of Long Lasting Insecticidal Nets bio-efficacy: a case study in north Cameroon. Parasit Vectors 2016; 9:132. [PMID: 26951758 PMCID: PMC4782322 DOI: 10.1186/s13071-016-1420-x] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Accepted: 03/02/2016] [Indexed: 12/04/2022] Open
Abstract
BACKGROUND In Cameroon, insecticide resistance in Anopheles (An.) gambiae s.l. has been reported in several foci, prompting further investigations on associated patterns of Long-Lasting Insecticidal Nets (LLINs) bio-efficacy. The current study, conducted from June to August 2011, explored the intensity of deltamethrin resistance in An. gambiae s.l. from Pitoa and its impact on the residual bio-efficacy of LifeNet, a LLIN with deltamethrin incorporated into polypropylene nets (PND). METHODS Two-four days old females An. gambiae s.l. reared from larval collections in Pitoa were tested for susceptibility to DDT, permethrin and deltamethrin, using standard World Health Organization (WHO) tube assays. Intensity of deltamethrin resistance was explored using WHO tube assays, but across six working concentrations from 0.001 % to 0.5 %. Bio-efficacy of unwashed and washed PND was assessed using WHO cone test. Species identification and kdr 1014 genotyping were performed on mosquito samples that were not exposed to insecticides, using PCR-RFLP and HOLA methods respectively. The Kisumu reference susceptible strain of An. gambiae s.s. was used for comparisons. RESULTS A total of 1895 An. gambiae s.l. specimens from Pitoa were used for resistance and PND bio-efficacy testing. This mosquito population was resistant to DDT, permethrin and deltamethrin, with 18-40 min knockdown times for 50 % of tested mosquitoes and 59-77 % mortality. Deltamethrin Resistance Ratio compared with the Kisumu strain was estimated at ≥500 fold. LifeNets were effective against the susceptible Kisumu (100 % knockdown (KD60min) and mortality) and the resistant Pitoa samples (95 % KD60min, 83-95 % mortality). However, the bio-efficacy gradually dropped against the Pitoa samples when nets were washed (X (2) = 35.887, df = 8, p < 0.001), and fell under the WHO efficacy threshold (80 % mortality and/or 95 % KD60min) between 10 and 15 washes. The Pitoa samples were composed of three sibling species: An. arabiensis (132/154, 86 %), An. coluzzii (19/154, 12 %) and An. gambiae s.s. (3/154, 2 %). The kdr L1014F allele was found only in An. coluzzii (Npositive = 13/19), at 34 % frequency and heterozygote stage. No specimen carried the kdr L1014S allele. CONCLUSIONS The current study showed that LifeNet might still offer some protection against the resistant An. gambiae s.l. population from Pitoa, provided appropriate dose of insecticide is available on the nets.
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Affiliation(s)
- Josiane Etang
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288, Yaoundé, Cameroun.
- Faculty of Medicine and Pharmaceutical Sciences, University of Douala, P.O. Box 2701, Douala, Cameroon.
| | - Cédric Pennetier
- Institut de Recherche pour le Développement (IRD) UMR224 MIVEGEC, 34394, Montpellier, France.
- Institut Pierre Richet (IPR), BP1500, Bouaké, Côte d'Ivoire.
| | - Michael Piameu
- Ecole des Sciences de la Santé, Université Catholique d'Afrique Centrale, B.P. 1110, Yaoundé, Cameroun.
| | - Aziz Bouraima
- Centre de Recherche Entomologique de Cotonou (CREC), 01 B.P. 4414, Cotonou, Bénin.
| | - Fabrice Chandre
- Institut de Recherche pour le Développement (IRD) UMR224 MIVEGEC, 34394, Montpellier, France.
| | - Parfait Awono-Ambene
- Institut de Recherche de Yaoundé (IRY), Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288, Yaoundé, Cameroun.
| | - Coosemans Marc
- Institute of Tropical Medicine, Department Parasitology - Entomology, Nationalestraat 155, B-2000, Antwerpen, Belgium.
- University of Antwerp, Antwerp, Belgium.
| | - Vincent Corbel
- Institut de Recherche pour le Développement (IRD) UMR224 MIVEGEC, 34394, Montpellier, France.
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, 10900, Thailand.
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