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Chen CY, Oliver SV. The effect of larval exposure to acids and detergents on the life history of the major malaria vector Anopheles arabiensis Patton (Diptera: Culicidae). PEST MANAGEMENT SCIENCE 2024; 80:4736-4745. [PMID: 38801202 DOI: 10.1002/ps.8189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 05/06/2024] [Accepted: 05/08/2024] [Indexed: 05/29/2024]
Abstract
BACKGROUND Anopheles arabiensis, a highly adaptable member of the Anopheles gambiae complex, poses a challenge for control efforts due to its outdoor biting and resting behaviour. Consequently, indoor insecticide-based control methods are ineffective against An. arabiensis. Furthermore, An. arabiensis are adapting to breeding in polluted waters, and may be contributing to residual malaria and malaria in urban areas. There have been some advances in understanding the effect of rural pollutants on Anopheles mosquitoes, but the effect of urban pollutants is poorly understood. Thus, in this study, the effect of acidic pollutants [nitric acid (HNO3) and hydrochloric acid (HCl)] and alkaline pollutants (phosphate-free and phosphate-containing detergent) on two laboratory-reared An. arabiensis strains - an insecticide susceptible strain (SENN) and an insecticide-resistant strain selected from SENN (SENN-DDT) - were determined. RESULTS The median lethal concentration (LC50) and larval exposure on larval development, adult longevity and insecticide tolerance were evaluated. Nitric acid and phosphate-containing detergent were found to be more toxic than HCl and phosphate-free detergent in terms of LC50 values. Detergent exposure (both phosphate-containing and phosphate-free) increased adult longevity of both strains. Nitric acid reduced larval development time in both SENN and SENN-DDT, whereas HCl reduced larval development time in SENN only. By contrast, both phosphate-containing and phosphate-free detergents increased larval development time of both strains. Furthermore, HNO3 and phosphate-containing detergent increased insecticide tolerance the most. CONCLUSION The two An. arabiensis strains responded to urban pollutants differently. Thus, this study provides insight into the adaptation of An. arabiensis to acidic and alkaline urban pollutants. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
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Affiliation(s)
- Chia-Yu Chen
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases a Division of the National Health Laboratory Service, Johannesburg, South Africa
- Wits Research Institute for Malaria, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Shüné V Oliver
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases a Division of the National Health Laboratory Service, Johannesburg, South Africa
- Wits Research Institute for Malaria, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
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Mapua SA, Samb B, Nambunga IH, Mkandawile G, Bwanaly H, Kaindoa EW, Odero JO, Masalu JP, Kahamba NF, Hape EE, Govella NJ, Okumu FO, Tripet F. Entomological survey of sibling species in the Anopheles funestus group in Tanzania confirms the role of Anopheles parensis as a secondary malaria vector. Parasit Vectors 2024; 17:261. [PMID: 38886827 PMCID: PMC11181546 DOI: 10.1186/s13071-024-06348-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Accepted: 06/10/2024] [Indexed: 06/20/2024] Open
Abstract
BACKGROUND Malaria transmission in Tanzania is driven by mosquitoes of the Anopheles gambiae complex and Anopheles funestus group. The latter includes An. funestus s.s., an anthropophilic vector, which is now strongly resistant to public health insecticides, and several sibling species, which remain largely understudied despite their potential as secondary vectors. This paper provides the initial results of a cross-country study of the species composition, distribution and malaria transmission potential of members of the Anopheles funestus group in Tanzania. METHODS Mosquitoes were collected inside homes in 12 regions across Tanzania between 2018 and 2022 using Centres for Disease Control and Prevention (CDC) light traps and Prokopack aspirators. Polymerase chain reaction (PCR) assays targeting the noncoding internal transcribed spacer 2 (ITS2) and 18S ribosomal DNA (18S rDNA) were used to identify sibling species in the An. funestus group and presence of Plasmodium infections, respectively. Where DNA fragments failed to amplify during PCR, we sequenced the ITS2 region to identify any polymorphisms. RESULTS The following sibling species of the An. funestus group were found across Tanzania: An. funestus s.s. (50.3%), An. parensis (11.4%), An. rivulorum (1.1%), An. leesoni (0.3%). Sequencing of the ITS2 region in the nonamplified samples showed that polymorphisms at the priming sites of standard species-specific primers obstructed PCR amplification, although the ITS2 sequences closely matched those of An. funestus s.s., barring these polymorphisms. Of the 914 samples tested for Plasmodium infections, 11 An. funestus s.s. (1.2%), and 2 An. parensis (0.2%) individuals were confirmed positive for P. falciparum. The highest malaria transmission intensities [entomological inoculation rate (EIR)] contributed by the Funestus group were in the north-western region [108.3 infectious bites/person/year (ib/p/y)] and the south-eastern region (72.2 ib/p/y). CONCLUSIONS Whereas An. funestus s.s. is the dominant malaria vector in the Funestus group in Tanzania, this survey confirms the occurrence of Plasmodium-infected An. parensis, an observation previously made in at least two other occasions in the country. The findings indicate the need to better understand the ecology and vectorial capacity of this and other secondary malaria vectors in the region to improve malaria control.
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Affiliation(s)
- Salum Abdallah Mapua
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Morogoro, Tanzania.
- Centre for Applied Entomology and Parasitology, School of Life Sciences, Keele University, Huxley Building, Keele, Staffordshire, ST5 5BG, UK.
| | - Badara Samb
- Laboratoire d'Écologie Vectorielle et Parasitaire, Département de Biologie Animale, Faculté des Sciences et Techniques, Université Cheikh Anta Diop de Dakar, 5005, Dakar-Fann, BP, Senegal
| | - Ismail Hassan Nambunga
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Morogoro, Tanzania
| | - Gustav Mkandawile
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Morogoro, Tanzania
| | - Hamis Bwanaly
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Morogoro, Tanzania
| | - Emmanuel Wilson Kaindoa
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Morogoro, Tanzania
| | - Joel Ouma Odero
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Morogoro, Tanzania
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, G61 1QH, UK
| | - John Paliga Masalu
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Morogoro, Tanzania
| | - Najat Feruz Kahamba
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Morogoro, Tanzania
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, G61 1QH, UK
| | - Emmanuel Elirehema Hape
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Morogoro, Tanzania
- School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Nicodem James Govella
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Morogoro, Tanzania
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, G61 1QH, UK
- School of Life Science and Bioengineering, The Nelson Mandela African Institution of Science and Technology, P. O. Box 447, Arusha, Tanzania
| | - Fredros Oketch Okumu
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Morogoro, Tanzania
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, G61 1QH, UK
- School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
- School of Life Science and Bioengineering, The Nelson Mandela African Institution of Science and Technology, P. O. Box 447, Arusha, Tanzania
| | - Frederic Tripet
- Swiss Tropical and Public Health Institute, Kreuzgasse 2, 4123, Allschwil, Switzerland
- University of Basel, Basel, Switzerland
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Wangrawa DW, Odero JO, Baldini F, Okumu F, Badolo A. Distribution and insecticide resistance profile of the major malaria vector Anopheles funestus group across the African continent. MEDICAL AND VETERINARY ENTOMOLOGY 2024; 38:119-137. [PMID: 38303659 DOI: 10.1111/mve.12706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Accepted: 01/10/2024] [Indexed: 02/03/2024]
Abstract
There has been significant progress in malaria control in the last 2 decades, with a decline in mortality and morbidity. However, these gains are jeopardised by insecticide resistance, which negatively impacts the core interventions, such as insecticide-treated nets (ITN) and indoor residual spraying (IRS). While most malaria control and research efforts are still focused on Anopheles gambiae complex mosquitoes, Anopheles funestus remains an important vector in many countries and, in some cases, contributes to most of the local transmission. As countries move towards malaria elimination, it is important to ensure that all dominant vector species, including An. funestus, an important vector in some countries, are targeted. The objective of this review is to compile and discuss information related to A. funestus populations' resistance to insecticides and the mechanisms involved across Africa, emphasising the sibling species and their resistance profiles in relation to malaria elimination goals. Data on insecticide resistance in An. funestus malaria vectors in Africa were extracted from published studies. Online bibliographic databases, including Google Scholar and PubMed, were used to search for relevant studies. Articles published between 2000 and May 2023 reporting resistance of An. funestus to insecticides and associated mechanisms were included. Those reporting only bionomics were excluded. Spatial variation in species distribution and resistance to insecticides was recorded from 174 articles that met the selection criteria. It was found that An. funestus was increasingly resistant to the four classes of insecticides recommended by the World Health Organisation for malaria vector control; however, this varied by country. Insecticide resistance appears to reduce the effectiveness of vector control methods, particularly IRS and ITN. Biochemical resistance due to detoxification enzymes (P450s and glutathione-S-transferases [GSTs]) in An. funestus was widely recorded. However, An. funestus in Africa remains susceptible to other insecticide classes, such as organophosphates and neonicotinoids. This review highlights the increasing insecticide resistance of An. funestus mosquitoes, which are important malaria vectors in Africa, posing a significant challenge to malaria control efforts. While An. funestus has shown resistance to the recommended insecticide classes, notably pyrethroids and, in some cases, organochlorides and carbamates, it remains susceptible to other classes of insecticides such as organophosphates and neonicotinoids, providing potential alternative options for vector control strategies. The study underscores the need for targeted interventions that consider the population structure and geographical distribution of An. funestus, including its sibling species and their insecticide resistance profiles, to effectively achieve malaria elimination goals.
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Affiliation(s)
- Dimitri W Wangrawa
- Laboratoire d'Entomologie Fondamentale et Appliquée, Université Joseph Ki-Zerbo, Ouagadougou, Burkina Faso
- Département des Sciences de la Vie et de la Terre, Université Norbert Zongo, Koudougou, Burkina Faso
| | - Joel O Odero
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Ifakara, Tanzania
- School of Biodiversity, One Health, and Veterinary Medicine, University of Glasgow, Glasgow, UK
| | - Francesco Baldini
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Ifakara, Tanzania
- School of Biodiversity, One Health, and Veterinary Medicine, University of Glasgow, Glasgow, UK
| | - Fredros Okumu
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Ifakara, Tanzania
| | - Athanase Badolo
- Laboratoire d'Entomologie Fondamentale et Appliquée, Université Joseph Ki-Zerbo, Ouagadougou, Burkina Faso
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Msugupakulya BJ, Urio NH, Jumanne M, Ngowo HS, Selvaraj P, Okumu FO, Wilson AL. Changes in contributions of different Anopheles vector species to malaria transmission in east and southern Africa from 2000 to 2022. Parasit Vectors 2023; 16:408. [PMID: 37936155 PMCID: PMC10631025 DOI: 10.1186/s13071-023-06019-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Accepted: 10/18/2023] [Indexed: 11/09/2023] Open
Abstract
BACKGROUND Malaria transmission in Africa is facilitated by multiple species of Anopheles mosquitoes. These vectors have different behaviors and vectorial capacities and are affected differently by vector control interventions, such as insecticide-treated nets and indoor residual spraying. This review aimed to assess changes in the contribution of different vector species to malaria transmission in east and southern Africa over 20 years of widespread insecticide-based vector control. METHODS We searched PubMed, Global Health, and Web of Science online databases for articles published between January 2000 and April 2023 that provided species-specific sporozoite rates for different malaria vectors in east and southern Africa. We extracted data on study characteristics, biting rates, sporozoite infection proportions, and entomological inoculation rates (EIR). Using EIR data, the proportional contribution of each species to malaria transmission was estimated. RESULTS Studies conducted between 2000 and 2010 identified the Anopheles gambiae complex as the primary malaria vector, while studies conducted from 2011 to 2021 indicated the dominance of Anopheles funestus. From 2000 to 2010, in 57% of sites, An. gambiae demonstrated higher parasite infection prevalence than other Anopheles species. Anopheles gambiae also accounted for over 50% of EIR in 76% of the study sites. Conversely, from 2011 to 2021, An. funestus dominated with higher infection rates than other Anopheles in 58% of sites and a majority EIR contribution in 63% of sites. This trend coincided with a decline in overall EIR and the proportion of sporozoite-infected An. gambiae. The main vectors in the An. gambiae complex in the region were Anopheles arabiensis and An. gambiae sensu stricto (s.s.), while the important member of the An. funestus group was An. funestus s.s. CONCLUSION The contribution of different vector species in malaria transmission has changed over the past 20 years. As the role of An. gambiae has declined, An. funestus now appears to be dominant in most settings in east and southern Africa. Other secondary vector species may play minor roles in specific localities. To improve malaria control in the region, vector control should be optimized to match these entomological trends, considering the different ecologies and behaviors of the dominant vector species.
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Affiliation(s)
- Betwel J Msugupakulya
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, PO Box 53, Ifakara, Tanzania.
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK.
| | - Naomi H Urio
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, PO Box 53, Ifakara, Tanzania
- School of Life Science and Bioengineering, The Nelson Mandela African Institution of Sciences & Technology, Arusha, Tanzania
| | - Mohammed Jumanne
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, PO Box 53, Ifakara, Tanzania
| | - Halfan S Ngowo
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, PO Box 53, Ifakara, Tanzania
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, UK
| | - Prashanth Selvaraj
- Institute for Disease Modeling, Bill and Melinda Gates Foundation, Seattle, USA
| | - Fredros O Okumu
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, PO Box 53, Ifakara, Tanzania.
- School of Life Science and Bioengineering, The Nelson Mandela African Institution of Sciences & Technology, Arusha, Tanzania.
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, UK.
- School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Park Town, Johannesburg, Republic of South Africa.
| | - Anne L Wilson
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK.
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Odero JO, Nambunga IH, Wangrawa DW, Badolo A, Weetman D, Koekemoer LL, Ferguson HM, Okumu FO, Baldini F. Advances in the genetic characterization of the malaria vector, Anopheles funestus, and implications for improved surveillance and control. Malar J 2023; 22:230. [PMID: 37553665 PMCID: PMC10410966 DOI: 10.1186/s12936-023-04662-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Accepted: 07/28/2023] [Indexed: 08/10/2023] Open
Abstract
Anopheles mosquitoes present a major public health challenge in sub-Saharan Africa; notably, as vectors of malaria that kill over half a million people annually. In parts of the east and southern Africa region, one species in the Funestus group, Anopheles funestus, has established itself as an exceptionally dominant vector in some areas, it is responsible for more than 90% of all malaria transmission events. However, compared to other malaria vectors, the species is far less studied, partly due to difficulties in laboratory colonization and the unresolved aspects of its taxonomy and systematics. Control of An. funestus is also increasingly difficult because it has developed widespread resistance to public health insecticides. Fortunately, recent advances in molecular techniques are enabling greater insights into species identity, gene flow patterns, population structure, and the spread of resistance in mosquitoes. These advances and their potential applications are reviewed with a focus on four research themes relevant to the biology and control of An. funestus in Africa, namely: (i) the taxonomic characterization of different vector species within the Funestus group and their role in malaria transmission; (ii) insecticide resistance profile; (iii) population genetic diversity and gene flow, and (iv) applications of genetic technologies for surveillance and control. The research gaps and opportunities identified in this review will provide a basis for improving the surveillance and control of An. funestus and malaria transmission in Africa.
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Affiliation(s)
- Joel O Odero
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Ifakara, Tanzania.
- School of Biodiversity, One Health, and Veterinary Medicine, University of Glasgow, Glasgow, G12 8QQ, UK.
| | - Ismail H Nambunga
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Ifakara, Tanzania
| | - Dimitri W Wangrawa
- Laboratoire d'Entomologie Fondamentale et Appliquée, Université Joseph ZEBRO, Ouagadougou, Burkina Faso
| | - Athanase Badolo
- Laboratoire d'Entomologie Fondamentale et Appliquée, Université Joseph ZEBRO, Ouagadougou, Burkina Faso
| | - David Weetman
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Lizette L Koekemoer
- Wits Research Institute for Malaria, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
- Centre for Emerging Zoonotic Parasitic Diseases, Vector Control Reference Laboratory, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa
| | - Heather M Ferguson
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Ifakara, Tanzania
- School of Biodiversity, One Health, and Veterinary Medicine, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Fredros O Okumu
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Ifakara, Tanzania
- School of Biodiversity, One Health, and Veterinary Medicine, University of Glasgow, Glasgow, G12 8QQ, UK
- School of Public Health, Faculty of Health Science, University of the Witwatersrand, Johannesburg, South Africa
- School of Life Science and Biotechnology, Nelson Mandela African Institution of Science and Technology, Arusha, Tanzania
| | - Francesco Baldini
- School of Biodiversity, One Health, and Veterinary Medicine, University of Glasgow, Glasgow, G12 8QQ, UK.
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Salomé G, Riddin M, Braack L. Species Composition, Seasonal Abundance, and Biting Behavior of Malaria Vectors in Rural Conhane Village, Southern Mozambique. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2023; 20:3597. [PMID: 36834293 PMCID: PMC9966379 DOI: 10.3390/ijerph20043597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Revised: 02/08/2023] [Accepted: 02/10/2023] [Indexed: 06/18/2023]
Abstract
Malaria vector surveillance provides important data to inform the effective planning of vector control interventions at a local level. The aim of this study was to determine the species diversity and abundance, biting activity, and Plasmodium infectivity of Anopheles mosquitoes from a rural village in southern Mozambique. Human landing catches were performed monthly between December 2020 and August 2021. All collected Anopheles were identified to the species level and tested for the presence of malaria parasites. Eight Anopheles species were identified among the 1802 collected anophelines. Anopheles gambiae sensu lato (s.l.) were the most abundant (51.9%) and were represented by Anopheles quadriannulatus and Anopheles arabiensis. Anopheles funestus s.l. represented 4.5%. The biting activity of An. arabiensis was more pronounced early in the evening and outdoors, whereas that of An. funestus sensu stricto (s.s.) was more intense late in the night, with no significant differences in location. One An. funestus s.s. and one An. arabiensis, both collected outdoors, were infected with Plasmodium falciparum. The overall entomologic inoculation rate was estimated at 0.015 infective bites per person per night. The significant outdoor and early evening biting activity of An. arabiensis and An. funestus found in this village may negatively impact the effectiveness of current vector control interventions. Additional vector control tools that can target these mosquitoes are needed.
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Affiliation(s)
- Graça Salomé
- UP Institute for Sustainable Malaria Control, School of Health Systems and Public Health, Faculty of Health Sciences, University of Pretoria, Pretoria 0028, South Africa
- Department of Physiological Sciences, Faculty of Medicine, Eduardo Mondlane University, 702 Salvador Allende Ave., Maputo P.O. Box 257, Mozambique
| | - Megan Riddin
- UP Institute for Sustainable Malaria Control, School of Health Systems and Public Health, Faculty of Health Sciences, University of Pretoria, Pretoria 0028, South Africa
| | - Leo Braack
- UP Institute for Sustainable Malaria Control, School of Health Systems and Public Health, Faculty of Health Sciences, University of Pretoria, Pretoria 0028, South Africa
- Malaria Consortium, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajavithi Rd, Ratchathewi, Bangkok 10400, Thailand
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Malaria Vector Surveillance and Control in an Elimination Setting in South Africa. Trop Med Infect Dis 2022; 7:tropicalmed7110391. [DOI: 10.3390/tropicalmed7110391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 11/17/2022] [Accepted: 11/18/2022] [Indexed: 11/23/2022] Open
Abstract
South Africa’s malaria elimination plans are aligned to the World Health Organization’s aim for a malaria-free world and include specific objectives within a specified time frame. These are proving difficult to achieve owing to the sporadic nature of locally acquired malaria in some affected districts, while other districts that were endemic for the disease are either malaria-free or very close to that goal. The WHO also specifies that continued measures to prevent the re-establishment of transmission are required in areas where elimination has been achieved. These measures include routine malaria vector surveillance in endemic districts that are free of malaria to assess receptivity and risk of reintroduction, which may prove difficult to justify in the face of competing public health priorities and limited resources. These issues are discussed here within the framework of vector surveillance and control and include recommendations on how they can be addressed going forward.
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Fernández Montoya L, Máquina M, Martí-Soler H, Sherrard-Smith E, Alafo C, Opiyo M, Comiche K, Galatas B, Huijben S, Koekemoer LL, Oliver SV, Maartens F, Marrenjo D, Cuamba N, Aide P, Saúte F, Paaijmans KP. The realized efficacy of indoor residual spraying campaigns falls quickly below the recommended WHO threshold when coverage, pace of spraying and residual efficacy on different wall types are considered. PLoS One 2022; 17:e0272655. [PMID: 36190958 PMCID: PMC9529131 DOI: 10.1371/journal.pone.0272655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Accepted: 07/22/2022] [Indexed: 11/06/2022] Open
Abstract
Indoor residual spraying (IRS) has been and remains an important malaria control intervention in southern Mozambique, South Africa and Eswatini. A better understanding of the effectiveness of IRS campaigns is critical to guide future elimination efforts. We analyze the three IRS campaigns conducted during a malaria elimination demonstration project in southern Mozambique, the "Magude project", and propose a new method to calculate the efficacy of IRS campaigns adjusting for IRS coverage, pace of house spraying and IRS residual efficacy on different wall types. Anopheles funestus sensu lato (s.l.) and An. gambiae s.l. were susceptible to pirimiphos-methyl and DDT. Anopheles funestus s.l. was resistant to pyrethroids, with 24h post-exposure mortality being lower for An. funestus sensu stricto (s.s.) than for An. parensis (collected indoors). The percentage of structures sprayed was above 90% and percentage of people covered above 86% in all three IRS campaigns. The percentage of households sprayed was above 83% in 2015 and 2016, but not assessed in 2017. Mosquito mortality 24h post-exposure stayed above 80% for 196 days after the 2016 IRS campaign and 222 days after the 2017 campaign and was 1.5 months longer on mud walls than on cement walls. This was extended by up to two months when 120h post-exposure mortality was considered. The district-level realized IRS efficacy was 113 days after the 2016 campaign. While the coverage of IRS campaigns in Magude were high, IRS protection did not remain optimal for the entire high malaria transmissions season. The use of a longer-lasting IRS product could have further supported the interruption of malaria transmission in the district. To better estimate the protection afforded by IRS campaigns, National Malaria Control Programs and partners are encouraged to adjust the calculation of IRS efficacy for IRS coverage, pace of house spraying during the campaign and IRS efficacy on different wall types combined with wall type distribution in the sprayed area.
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Affiliation(s)
- Lucia Fernández Montoya
- Centro de Investigação em Saúde de Manhiça (CISM), Manhiça, Mozambique
- ISGlobal, Barcelona, Spain
| | - Mara Máquina
- Centro de Investigação em Saúde de Manhiça (CISM), Manhiça, Mozambique
| | | | - Ellie Sherrard-Smith
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, United Kingdom
| | - Celso Alafo
- Centro de Investigação em Saúde de Manhiça (CISM), Manhiça, Mozambique
| | - Mercy Opiyo
- Centro de Investigação em Saúde de Manhiça (CISM), Manhiça, Mozambique
- ISGlobal, Barcelona, Spain
| | - Kiba Comiche
- Centro de Investigação em Saúde de Manhiça (CISM), Manhiça, Mozambique
| | - Beatriz Galatas
- Centro de Investigação em Saúde de Manhiça (CISM), Manhiça, Mozambique
- ISGlobal, Barcelona, Spain
| | - Silvie Huijben
- ISGlobal, Barcelona, Spain
- Center for Evolution and Medicine, School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America
- Simon A. Levin Mathematical, Computational and Modeling Sciences Center, Arizona State University, Tempe, Arizona, United States of America
| | - Lizette L. Koekemoer
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, Johannesburg, South Africa
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa
| | - Shüné V. Oliver
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, Johannesburg, South Africa
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa
| | | | | | - Nelson Cuamba
- National Malaria Control Programme, Ministry of Health, Maputo, Mozambique
- PMI VectorLink Project, Abt Associates Inc., Maputo, Mozambique
| | - Pedro Aide
- Centro de Investigação em Saúde de Manhiça (CISM), Manhiça, Mozambique
- National Institute of Health, Ministry of Health, Maputo, Mozambique
| | - Francisco Saúte
- Centro de Investigação em Saúde de Manhiça (CISM), Manhiça, Mozambique
| | - Krijn P. Paaijmans
- Centro de Investigação em Saúde de Manhiça (CISM), Manhiça, Mozambique
- ISGlobal, Barcelona, Spain
- Center for Evolution and Medicine, School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America
- Simon A. Levin Mathematical, Computational and Modeling Sciences Center, Arizona State University, Tempe, Arizona, United States of America
- The Biodesign Center for Immunotherapy, Vaccines and Virotherapy, Arizona State University, Tempe, AZ, United States of America
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Nkya TE, Fillinger U, Sangoro OP, Marubu R, Chanda E, Mutero CM. Six decades of malaria vector control in southern Africa: a review of the entomological evidence-base. Malar J 2022; 21:279. [PMID: 36184603 PMCID: PMC9526912 DOI: 10.1186/s12936-022-04292-6] [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: 05/27/2022] [Accepted: 09/05/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Countries in the southern Africa region have set targets for malaria elimination between 2020 and 2030. Malaria vector control is among the key strategies being implemented to achieve this goal. This paper critically reviews published entomological research over the past six decades in three frontline malaria elimination countries namely, Botswana Eswatini and Namibia, and three second-line malaria elimination countries including Mozambique, Zambia, and Zimbabwe. The objective of the review is to assess the current knowledge and highlight gaps that need further research attention to strengthen evidence-based decision-making toward malaria elimination. METHODS Publications were searched on the PubMed engine using search terms: "(malaria vector control OR vector control OR malaria vector*) AND (Botswana OR Swaziland OR Eswatini OR Zambia OR Zimbabwe OR Mozambique)". Opinions, perspectives, reports, commentaries, retrospective analysis on secondary data protocols, policy briefs, and reviews were excluded. RESULTS The search resulted in 718 publications with 145 eligible and included in this review for the six countries generated over six decades. The majority (139) were from three countries, namely Zambia (59) and Mozambique (48), and Zimbabwe (32) whilst scientific publications were relatively scanty from front-line malaria elimination countries, such as Namibia (2), Botswana (10) and Eswatini (4). Most of the research reported in the publications focused on vector bionomics generated mostly from Mozambique and Zambia, while information on insecticide resistance was mostly available from Mozambique. Extreme gaps were identified in reporting the impact of vector control interventions, both on vectors and disease outcomes. The literature is particularly scanty on important issues such as change of vector ecology over time and space, intervention costs, and uptake of control interventions as well as insecticide resistance. CONCLUSIONS The review reveals a dearth of information about malaria vectors and their control, most noticeable among the frontline elimination countries: Namibia, Eswatini and Botswana. It is of paramount importance that malaria vector research capacity and routine entomological monitoring and evaluation are strengthened to enhance decision-making, considering changing vector bionomics and insecticide resistance, among other determinants of malaria vector control.
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Affiliation(s)
- Theresia Estomih Nkya
- International Centre of Insect Physiology and Ecology, Nairobi, Kenya
- University of Dar es Salaam, Mbeya College of Health and Allied Sciences, Mbeya, Tanzania
| | - Ulrike Fillinger
- International Centre of Insect Physiology and Ecology, Nairobi, Kenya
| | | | - Rose Marubu
- International Centre of Insect Physiology and Ecology, Nairobi, Kenya
| | - Emmanuel Chanda
- World Health Organization-Regional Office for Africa, Brazzaville, Republic of Congo
| | - Clifford Maina Mutero
- International Centre of Insect Physiology and Ecology, Nairobi, Kenya
- School of Health Systems and Public Health, University of Pretoria, Pretoria, South Africa
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10
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Fernández Montoya L, Martí-Soler H, Máquina M, Comiche K, Cuamba I, Alafo C, Koekemoer LL, Sherrard-Smith E, Bassat Q, Galatas B, Aide P, Cuamba N, Jotamo D, Saúte F, Paaijmans KP. The mosquito vectors that sustained malaria transmission during the Magude project despite the combined deployment of indoor residual spraying, insecticide-treated nets and mass-drug administration. PLoS One 2022; 17:e0271427. [PMID: 36084031 PMCID: PMC9462736 DOI: 10.1371/journal.pone.0271427] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 08/23/2022] [Indexed: 11/18/2022] Open
Abstract
The "Magude project" aimed but failed to interrupt local malaria transmission in Magude district, southern Mozambique, by using a comprehensive package of interventions, including indoor residual spraying (IRS), pyrethroid-only long-lasting insecticide treated nets (LLINs) and mass-drug administration (MDA). Here we present detailed information on the vector species that sustained malaria transmission, their association with malaria incidence and behaviors, and their amenability to the implemented control interventions. Mosquitoes were collected monthly between May 2015 and October 2017 in six sentinel sites in Magude district, using CDC light traps both indoors and outdoors. Anopheles arabiensis was the main vector during the project, while An. funestus s.s., An. merus, An. parensis and An. squamosus likely played a secondary role. The latter two species have never previously been found positive for Plasmodium falciparum in southern Mozambique. The intervention package successfully reduced vector sporozoite rates in all species throughout the project. IRS was effective in controlling An. funestus s.s. and An. parensis, which virtually disappeared after its first implementation, but less effective at controlling An. arabiensis. Despite suboptimal use, LLINs likely provided significant protection against An. arabiensis and An. merus that sought their host largely indoors when people where in bed. Adding IRS on top of LLINs and MDA likely added value to the control of malaria vectors during the Magude project. Future malaria elimination attempts in the area could benefit from i) increasing the use of LLINs, ii) using longer-lasting IRS products to counteract the increase in vector densities observed towards the end of the high transmission season, and iii) a higher coverage with MDA to reduce the likelihood of human infection. However, additional interventions targeting vectors that survive IRS and LLINs by biting outdoors or indoors before people go to bed, will be likely needed to achieve local malaria elimination.
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Affiliation(s)
- Lucía Fernández Montoya
- ISGlobal, Barcelona, Spain
- Centro de Investigação em Saúde de Manhiça (CISM), Fundação Manhiça, Mozambique
| | | | - Mara Máquina
- Centro de Investigação em Saúde de Manhiça (CISM), Fundação Manhiça, Mozambique
| | - Kiba Comiche
- Centro de Investigação em Saúde de Manhiça (CISM), Fundação Manhiça, Mozambique
| | - Inocencia Cuamba
- Centro de Investigação em Saúde de Manhiça (CISM), Fundação Manhiça, Mozambique
| | - Celso Alafo
- Centro de Investigação em Saúde de Manhiça (CISM), Fundação Manhiça, Mozambique
| | - Lizette L. Koekemoer
- Faculty of Health Sciences, WITS Research Institute for Malaria, University of the Witswatersrand and the Natitonal Institute for Communicable Diseases, Johannesburg, South Africa
| | - Ellie Sherrard-Smith
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, United Kingdom
| | - Quique Bassat
- ISGlobal, Barcelona, Spain
- Centro de Investigação em Saúde de Manhiça (CISM), Fundação Manhiça, Mozambique
- ICREA, Barcelona, Spain
- Pediatrics Department, Hospital Sant Joan de Déu, Universitat de Barcelona, Esplugues, Barcelona, Spain
- Consorcio de Investigación Biomédica en Red de Epidemiología y Salud Pública (CIBERESP), Madrid, Spain
| | - Beatriz Galatas
- ISGlobal, Barcelona, Spain
- Centro de Investigação em Saúde de Manhiça (CISM), Fundação Manhiça, Mozambique
| | - Pedro Aide
- Centro de Investigação em Saúde de Manhiça (CISM), Fundação Manhiça, Mozambique
- Instituto Nacional da Saúde, Ministério da Saúde, Maputo, Mozambique
| | - Nelson Cuamba
- Programa Nacional de Controlo da Malária, Ministério da Saúde, Maputo, Mozambique
- PMI VectorLink Project, Abt Associates Inc., Maputo, Mozambique
| | - Dulcisaria Jotamo
- Programa Nacional de Controlo da Malária, Ministério da Saúde, Maputo, Mozambique
| | - Francisco Saúte
- Centro de Investigação em Saúde de Manhiça (CISM), Fundação Manhiça, Mozambique
| | - Krijn P. Paaijmans
- ISGlobal, Barcelona, Spain
- Centro de Investigação em Saúde de Manhiça (CISM), Fundação Manhiça, Mozambique
- Center for Evolution and Medicine, School of Life Sciences, Arizona State University, Tempe, AZ, United States of America
- The Biodesign Center for Immunotherapy, Vaccines and Virotherapy, Arizona State University, Tempe, AZ, United States of America
- Simon A. Levin Mathematical, Computational and Modeling Sciences Center, Arizona State University, Tempe, AZ, United States of America
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11
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Mapua SA, Hape EE, Kihonda J, Bwanary H, Kifungo K, Kilalangongono M, Kaindoa EW, Ngowo HS, Okumu FO. Persistently high proportions of plasmodium-infected Anopheles funestus mosquitoes in two villages in the Kilombero valley, South-Eastern Tanzania. Parasite Epidemiol Control 2022; 18:e00264. [PMID: 35959316 PMCID: PMC9357827 DOI: 10.1016/j.parepi.2022.e00264] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 06/20/2022] [Accepted: 07/29/2022] [Indexed: 11/04/2022] Open
Abstract
Background In south-eastern Tanzania where insecticide-treated nets have been widely used for >20 years, malaria transmission has greatly reduced but remains highly heterogenous over small distances. This study investigated the seasonal prevalence of Plasmodium sporozoite infections in the two main malaria vector species, Anopheles funestus and Anopheles arabiensis for 34 months, starting January 2018 to November 2020. Methods Adult mosquitoes were collected using CDC-light traps and Prokopack aspirators inside local houses in Igumbiro and Sululu villages, where earlier surveys had found very high densities of An. funestus. Collected females were sorted by taxa, and the samples examined using ELISA assays for detecting Plasmodium circumsporozoite protein in their salivary glands. Results Of 7859 An. funestus tested, 4.6% (n = 365) were positive for Pf sporozoites in the salivary glands. On the contrary, only 0.4% (n = 9) of the 2382 An. arabiensis tested were positive. The sporozoite prevalence did not vary significantly between the villages or seasons. Similarly, the proportions of parous females of either species were not significantly different between the two villages (p > 0.05) but was slightly higher in An. funestus (0.50) than in An. arabiensis (0.42). Analysis of the 2020 data determined that An. funestus contributed 97.7% of all malaria transmitted in households in these two villages. Conclusions In contexts where individual vector species mediate most of the pathogen transmission, it may be most appropriate to pursue a species-focused approach to better understand the ecology of the dominant vectors and target them with effective interventions to suppress transmission. Despite the ongoing efforts on tackling malaria in the two study villages, there is still persistently high Plasmodium infection prevalence in local populations of An. funestus, which now carry ~97% of all malaria infections and mediates intense year-round transmission. Further reduction in malaria burden in these or other similar settings requires effective targeting of An. funestus.
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12
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Gebhardt ME, Krizek RS, Coetzee M, Koekemoer LL, Dahan-Moss Y, Mbewe D, Lupiya JS, Muleba M, Stevenson JC, Moss WJ, Norris DE. Expanded geographic distribution and host preference of Anopheles gibbinsi (Anopheles species 6) in northern Zambia. Malar J 2022; 21:211. [PMID: 35780113 PMCID: PMC9250713 DOI: 10.1186/s12936-022-04231-5] [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: 03/27/2022] [Accepted: 06/15/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Nchelenge District in northern Zambia suffers from holoendemic malaria transmission despite a decade of yearly indoor residual spraying (IRS) and insecticide-treated net (ITN) distributions. One hypothesis for this lack of impact is that some vectors in the area may forage in the early evening or outdoors. Anopheles gibbinsi specimens were identified in early evening mosquito collections performed in this study area, and further insight was gleaned into this taxon, including characterizing its genetic identity, feeding preferences, and potential role as a malaria vector. METHODS Mosquitoes were collected in July and August 2019 by CDC light traps in Nchelenge District in indoor sitting rooms, outdoor gathering spaces, and animal pens from 16:00-22:00. Host detection by PCR, COI and ITS2 PCR, and circumsporozoite (CSP) ELISA were performed on all samples morphologically identified as An. gibbinsi, and a subset of specimens were selected for COI and ITS2 sequencing. To determine risk factors for increased abundance of An. gibbinsi, a negative binomial generalized linear mixed-effects model was performed with household-level variables of interest. RESULTS Comparison of COI and ITS2 An. gibbinsi reference sequences to the NCBI database revealed > 99% identity to "Anopheles sp. 6" from Kenya. More than 97% of specimens were morphologically and molecularly consistent with An. gibbinsi. Specimens were primarily collected in animal pen traps (59.2%), followed by traps outdoors near where humans gather (24.3%), and traps set indoors (16.5%). Host DNA detection revealed a high propensity for goats, but 5% of specimens with detected host DNA had fed on humans. No specimens were positive for Plasmodium falciparum sporozoites. Animal pens and inland households > 3 km from Lake Mweru were both associated with increased An. gibbinsi abundance. CONCLUSIONS This is the first report of An. gibbinsi in Nchelenge District, Zambia. This study provided a species identity for unknown "An. sp. 6" in the NCBI database, which has been implicated in malaria transmission in Kenya. Composite data suggest that this species is largely zoophilic and exophilic, but comes into contact with humans and the malaria parasites they carry. This species should continue to be monitored in Zambia and neighbouring countries as a potential malaria vector.
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Affiliation(s)
- Mary E Gebhardt
- The W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
| | - Rachel S Krizek
- The W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Maureen Coetzee
- Wits Research Institute for Malaria, Faculty of Health Sciences, University of the Witwatersrand, and the Centre for Emerging Zoonotic & Parasitic Diseases, Vector Control Reference Laboratory, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa
| | - Lizette L Koekemoer
- Wits Research Institute for Malaria, Faculty of Health Sciences, University of the Witwatersrand, and the Centre for Emerging Zoonotic & Parasitic Diseases, Vector Control Reference Laboratory, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa
| | - Yael Dahan-Moss
- Wits Research Institute for Malaria, Faculty of Health Sciences, University of the Witwatersrand, and the Centre for Emerging Zoonotic & Parasitic Diseases, Vector Control Reference Laboratory, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa
| | - David Mbewe
- Tropical Diseases Research Centre, Ndola, Zambia
| | | | | | - Jennifer C Stevenson
- The W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
- Macha Research Trust, Choma, Zambia
| | - William J Moss
- The W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Douglas E Norris
- The W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
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13
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Kumala J, Koekemoer LL, Coetzee M, Mzilahowa T. Intensity of insecticide resistance in the major malaria vector Anopheles funestus from Chikwawa, rural Southern Malawi. Parasit Vectors 2022; 15:220. [PMID: 35729623 PMCID: PMC9210055 DOI: 10.1186/s13071-022-05299-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Accepted: 04/26/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Malaria vector control using insecticide-based approaches has proven to be an effective strategy. However, widespread insecticide resistance among malaria vector populations across sub-Saharan Africa threatens to derail control efforts. This study was conducted in Chikwawa district, an area in rural southern Malawi characterised by persistent malaria transmission and reports of insecticide resistance in the local mosquito population. The aim of the was to characterise the intensity of insecticide resistance within a population of Anopheles funestus sensu lato (s.l.), a major vector of malaria in this district. METHODS Live adult females belonging to the An. funestus group were collected from households by indoor aspiration. The CDC bottle assay was used for phenotypic quantification of resistance to deltamethrin, permethrin and alpha-cypermethrin at 1×, 2.5×, 5× and 10× the recommended diagnostic dose for each of these insecticides. WHO tube assays were used to determine susceptibility to bendiocarb, dichlorodiphenyltrichloroethane (DDT) and pirimiphos-methyl insecticides at diagnostic concentrations. RESULTS Anopheles funestus s.l. exposed to 10× the recommended diagnostic dose was highly resistant to alpha-cypermethrin (mortality 95.4%); in contrast, mortality was 100% when exposed to both deltamethrin and permethrin at the same dose. Despite showing susceptibility to deltamethrin and permethrin at the 10× concentration, mortality at the 5× concentration was 96.7% and 97.1%, respectively, indicating moderate resistance to these two insecticides. WHO susceptibility assays indicated strong resistance against bendiocarb (mortality 33.8%, n = 93), whereas there was full susceptibility to DDT (mortality 98.9%, n = 103) and pirimiphos-methyl (mortality 100%, n = 103). CONCLUSIONS Strategies for managing resistance to insecticides, particularly against pyrethroids, must be urgently implemented to maintain the effectiveness of insecticide-based vector control interventions in the area. Such strategies include the wide-scale introduction of third-generation synergist insecticide-treated bed nets (ITNs) and next-generation dual active ingredient ITNs. The use of effective non-pyrethroids, such as pirimiphos-methyl, clothianidin and potentially DDT, could provide a window of opportunity for indoor residual spraying across the district. This strategy would support the current Malawi Insecticide Resistance Management Plan which aims at rotating insecticides to minimise selection pressure and slow down the evolution of resistance to approved insecticides. These actions will help to prevent malaria vector control failure and improve progress towards malaria elimination.
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Affiliation(s)
- Justin Kumala
- Malaria Alert Centre-Communicable Diseases Action Centre (MAC-CDAC), Kamuzu University of Health Sciences, Blantyre, Malawi.,Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.,Centre for Emerging Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg, South Africa
| | - Lizette L Koekemoer
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.,Centre for Emerging Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg, South Africa
| | - Maureen Coetzee
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.,Centre for Emerging Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg, South Africa
| | - Themba Mzilahowa
- Malaria Alert Centre-Communicable Diseases Action Centre (MAC-CDAC), Kamuzu University of Health Sciences, Blantyre, Malawi.
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14
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Kahamba NF, Finda M, Ngowo HS, Msugupakulya BJ, Baldini F, Koekemoer LL, Ferguson HM, Okumu FO. Using ecological observations to improve malaria control in areas where Anopheles funestus is the dominant vector. Malar J 2022; 21:158. [PMID: 35655190 PMCID: PMC9161514 DOI: 10.1186/s12936-022-04198-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Accepted: 05/19/2022] [Indexed: 11/10/2022] Open
Abstract
The most important malaria vectors in sub-Saharan Africa are Anopheles gambiae, Anopheles arabiensis, Anopheles funestus, and Anopheles coluzzii. Of these, An. funestus presently dominates in many settings in east and southern Africa. While research on this vector species has been impeded by difficulties in creating laboratory colonies, available evidence suggests it has certain ecological vulnerabilities that could be strategically exploited to greatly reduce malaria transmission in areas where it dominates. This paper examines the major life-history traits of An. funestus, its aquatic and adult ecologies, and its responsiveness to key interventions. It then outlines a plausible strategy for reducing malaria transmission by the vector and sustaining the gains over the medium to long term. To illustrate the propositions, the article uses data from south-eastern Tanzania where An. funestus mediates over 85% of malaria transmission events and is highly resistant to key public health insecticides, notably pyrethroids. Both male and female An. funestus rest indoors and the females frequently feed on humans indoors, although moderate to high degrees of zoophagy can occur in areas with large livestock populations. There are also a few reports of outdoor-biting by the species, highlighting a broader range of behavioural phenotypes that can be considered when designing new interventions to improve vector control. In comparison to other African malaria vectors, An. funestus distinctively prefers permanent and semi-permanent aquatic habitats, including river streams, ponds, swamps, and spring-fed pools. The species is therefore well-adapted to sustain its populations even during dry months and can support year-round malaria transmission. These ecological features suggest that highly effective control of An. funestus could be achieved primarily through strategic combinations of species-targeted larval source management and high quality insecticide-based methods targeting adult mosquitoes in shelters. If done consistently, such an integrated strategy has the potential to drastically reduce local populations of An. funestus and significantly reduce malaria transmission in areas where this vector species dominates. To sustain the gains, the programmes should be complemented with gradual environmental improvements such as house modification to maintain biting exposure at a bare minimum, as well as continuous engagements of the resident communities and other stakeholders.
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Affiliation(s)
- Najat F Kahamba
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania.
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, G128QQ, Glasgow, UK.
| | - Marceline Finda
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania
- School of Public Health, Faculty of Health Science, University of the Witwatersrand, Johannesburg, South Africa
| | - Halfan S Ngowo
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, G128QQ, Glasgow, UK
| | - Betwel J Msugupakulya
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Francesco Baldini
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, G128QQ, Glasgow, UK
| | - Lizette L Koekemoer
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Heather M Ferguson
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, G128QQ, Glasgow, UK
| | - Fredros O Okumu
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania.
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, G128QQ, Glasgow, UK.
- School of Public Health, Faculty of Health Science, University of the Witwatersrand, Johannesburg, South Africa.
- School of Life Science and Biotechnology, Nelson Mandela African Institution of Science and Technology, P. O. Box 447, Arusha, Tanzania.
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15
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Munhenga G, Oliver SV, Lobb LN, Mazarire TT, Sekgele W, Mashatola T, Mabaso N, Dlamini DM, Zulu M, Moletsane F, Letinić BD, Zawada J, Burke A, Matamba A, Brooke BD. Malaria risk and receptivity: Continuing development of insecticide resistance in the major malaria vector Anopheles arabiensis in northern KwaZulu-Natal, South Africa. S AFR J SCI 2022. [DOI: 10.17159/sajs.2022/11755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
Malaria incidence in South Africa is highest in the three endemic provinces: KwaZulu-Natal, Mpumalanga and Limpopo. The contribution to malaria transmission by several mosquito species, variation in their resting behaviours and low levels of insecticide resistance makes it necessary to periodically monitor Anopheles species assemblages and resistance phenotypes in vector populations. The aim of this study was therefore to assess Anopheles species assemblage in northern KwaZulu-Natal and to collect insecticide susceptibility data for An. arabiensis, the primary vector of malaria in that province. Anopheles specimens were collected from Mamfene, Jozini, northern KwaZulu-Natal from November 2019 to April 2021. Progeny of wild-collected An. arabiensis females were used for standard insecticide susceptibility tests and synergist bioassays. Anopheles arabiensis contributed 85.6% (n=11 062) of the total catches. Samples for subsequent insecticide susceptibility bioassays were selected from 212 An. arabiensis families. These showed low-level resistance to DDT, permethrin, deltamethrin, and bendiocarb, as well as full susceptibility to pirimiphos-methyl. Synergist bioassays using piperonyl butoxide and triphenyl phosphate suggest oxygenase-based pyrethroid and esterase-mediated sequestration of bendiocarb. These low levels of resistance are unlikely to be operationally significant at present. It is concluded that northern KwaZulu-Natal Province remains receptive to malaria transmission despite ongoing control and elimination interventions. This is due to the perennial presence of the major vector An. arabiensis and other secondary vector species. The continued detection of low-frequency insecticide resistance phenotypes in An. arabiensis is cause for concern and requires periodic monitoring for changes in resistance frequency and intensity.
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Affiliation(s)
- Givemore Munhenga
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa
- Wits Research Institute for Malaria, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa
| | - Shüné V. Oliver
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa
- Wits Research Institute for Malaria, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa
| | - Leanne N. Lobb
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa
- Wits Research Institute for Malaria, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa
| | - Theresa T. Mazarire
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa
- Wits Research Institute for Malaria, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa
| | - Windy Sekgele
- Wits Research Institute for Malaria, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa
| | - Thabo Mashatola
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa
- Wits Research Institute for Malaria, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa
| | - Nondumiso Mabaso
- Wits Research Institute for Malaria, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa
| | - Dumsani M. Dlamini
- Wits Research Institute for Malaria, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa
| | - Malibongwe Zulu
- Wits Research Institute for Malaria, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa
| | - Fortunate Moletsane
- Wits Research Institute for Malaria, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa
| | - Blaženka D. Letinić
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa
- Wits Research Institute for Malaria, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa
| | - Jacek Zawada
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa
- Wits Research Institute for Malaria, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa
| | - Ashley Burke
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa
- Wits Research Institute for Malaria, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa
| | - Avhatakali Matamba
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa
| | - Basil D. Brooke
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg, South Africa
- Wits Research Institute for Malaria, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa
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Gebhardt ME, Searle KM, Kobayashi T, Shields TM, Hamapumbu H, Simubali L, Mudenda T, Thuma PE, Stevenson JC, Moss WJ, Norris DE. Understudied Anophelines Contribute to Malaria Transmission in a Low-Transmission Setting in the Choma District, Southern Province, Zambia. Am J Trop Med Hyg 2022; 106:tpmd210989. [PMID: 35344932 PMCID: PMC9128685 DOI: 10.4269/ajtmh.21-0989] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Accepted: 10/29/2021] [Indexed: 11/11/2022] Open
Abstract
Malaria transmission has declined substantially in Southern Province, Zambia, which is considered a low-transmission setting. The Zambian government introduced a reactive test-and-treat strategy to identify active zones of transmission and treat parasitemic residents. This study was conducted in the Choma District, Southern Province, Zambia, concurrently with an evaluation of this strategy to identify vectors responsible for sustaining transmission, and to identify entomological, spatial, and ecological risk factors associated with increased densities of mosquitoes. Anophelines were collected with CDC light traps indoors and near animal pens in index cases and neighboring households. Outdoor collections captured significantly more anophelines than indoor traps, and 10 different anopheline species were identified. Four species (Anopheles arabiensis, An. rufipes, An. squamosus, and An. coustani) were positive for Plasmodium falciparum circumsporozoite protein by ELISA, and 61% of these 26 anophelines were captured outdoors. Bloodmeal assays confirm plasticity in An. arabiensis foraging, feeding both on humans and animals, whereas An. rufipes, An. squamosus, and An. coustani were largely zoophilic and exophilic. Linear regression of count data for indoor traps revealed that households with at least one parasitemic resident by polymerase chain reaction testing was associated with higher female anopheline counts. This suggests that targeting households with parasitemic individuals for vector interventions may reduce indoor anopheline populations. However, many vectors species responsible for transmission may not be affected by indoor interventions because they are primarily exophilic and forage opportunistically. These data underscore the necessity for further evaluation of vector surveillance and control tools that are effective outdoors, in conjunction with current indoor-based interventions.
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Affiliation(s)
- Mary E. Gebhardt
- Johns Hopkins Malaria Research Institute, The W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | - Kelly M. Searle
- Division of Epidemiology and Community Health, University of Minnesota, Minneapolis, Minnesota
| | - Tamaki Kobayashi
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | - Timothy M. Shields
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | | | | | | | | | - Jennifer C. Stevenson
- Johns Hopkins Malaria Research Institute, The W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
- Macha Research Trust, Choma, Zambia
| | - William J. Moss
- Johns Hopkins Malaria Research Institute, The W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
| | - Douglas E. Norris
- Johns Hopkins Malaria Research Institute, The W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
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17
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Mavridis K, Michaelidou K, Vontas J. Highly sensitive droplet digital PCR-based diagnostics for the surveillance of malaria vector populations in low transmission and incipient resistance settings. Expert Rev Mol Diagn 2021; 21:1105-1114. [PMID: 34328051 DOI: 10.1080/14737159.2021.1963234] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
BACKGROUND Sensitive monitoring of Plasmodium infective mosquitoes in low malaria transmission settings is of high priority for disease control. Early detection of insecticide resistance at low frequencies is also key for vector monitoring nowadays, when new insecticides are launched to control vector populations. RESEARCH DESIGN AND METHODS An. gambiae mosquitoes with predetermined infection and resistance status were used to produce populations with various malaria infection rates and mutant allelic frequencies (MAFs) of target site insecticide resistance traits. Total RNA and gDNA were isolated and used in droplet Digital PCR (ddPCR) and Reverse Transcription (RT) ddPCR performed in the QX200 ddPCR System. RESULTS We developed a novel ddPCR for detecting P. falciparum DNA in pooled mosquito head-thoraces with infective rate as low as 1.0%. A dissection-free RT-ddPCR assay for specific infective-stage detection was additionally developed and validated (accuracy = 100%) in mosquito pools with infective rates down to 1.0%. A novel ddPCR assay for insecticide resistant alleles, which was able to reliably quantify MAFs as low as 0.050% in pooled mosquito specimens, is also reported. CONCLUSIONS We developed highly sensitive and efficient (RT-) ddPCR assays for contemporary operational needs that require monitoring of low malaria transmission and emerging insecticide resistance.
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Affiliation(s)
- Konstantinos Mavridis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece
| | - Kleita Michaelidou
- Laboratory of Translational Oncology, School of Medicine, University of Crete, Heraklion, Greece
| | - John Vontas
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion, Greece.,Pesticide Science Laboratory, Department of Crop Science, Agricultural University of Athens, Athens, Greece
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18
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Wragge SE, Venter N, Touré D, Hunt RH, Coetzee M. New distribution record of Anopheles rivulorum-like from Sadiola, Mali, with notes on malaria vector insecticide resistance. Trans R Soc Trop Med Hyg 2021; 115:495-499. [PMID: 33096555 DOI: 10.1093/trstmh/traa113] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 09/06/2020] [Accepted: 10/06/2020] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND The SEMOS gold mine in Sadiola, southwestern Mali, has been implementing a malaria vector control programme for 15 y using indoor residual house spraying and sporadic larval control. Periodic screening of the vector populations have been carried out over the years to provide information to the control programme, mainly on vector species present and their insecticide resistance status. The data from five entomological surveys, carried out in 2006, 2011, 2014, 2016 and 2018, are presented. METHODS Adult mosquitoes were collected resting on walls inside houses and on verandas. Insecticide susceptibility assays were carried out and mosquitoes subsequently identified by species using molecular assays. RESULTS The major malaria vector mosquitoes, Anopheles gambiae and Anopheles arabiensis were abundant at each sampling period with Anopheles coluzzii and Anopheles funestus being rare or absent. Anopheles rivulorum was identified in 2006 and Anopheles leesoni in 2016. The presence of Anopheles rivulorum-like, identified for the first time in 2018, was not screened for in previous surveys. Insecticide susceptibility bioassays showed resistance in both A. gambiae and A. arabiensis to pyrethroids, carbamates and dichlorodiphenyltrichloroethane over the 12 y. CONCLUSIONS This is the first record of A. rivulorum-like west of Côte d'Ivoire. Resistance levels to the three classes of insecticides were variable but appeared to decrease after pyrethroids were discontinued for house spraying.
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Affiliation(s)
- Sue-Ellen Wragge
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.,SEMOS Gold Mine, Sadiola, Kayes District, Mali
| | - Nelius Venter
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.,Centre for Emerging Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg, South Africa
| | | | - Richard H Hunt
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.,Centre for Emerging Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg, South Africa
| | - Maureen Coetzee
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.,Centre for Emerging Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg, South Africa
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19
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Abstract
Residual malaria transmission is the actual maintained inoculation of Plasmodium, in spite of a well-designed and implemented vector control programs, and is of great concern for malaria elimination. Residual malaria transmission occurs under several possible circumstances, among which the presence of exophilic vector species, such as Anopheles dirus, or indoor- and outdoor-biting vectors, such as Anopheles nili, or specific behavior, such as feeding on humans indoors, then resting or leaving the house the same night (such as Anopheles moucheti) or also changes in behavior induced by insecticides applied inside houses, such as the well-known deterrent effect of permethrin-treated nets or the irritant effect of DDT. The use of insecticides may change the composition of local Anopheles populations, such as A. arabiensis taking up the place of A. gambiae in Senegal, A. aquasalis replacing A. darlingi in Guyana, or A. harrisoni superseding A. minimus in Vietnam. The change in behavior, such as biting activity earlier than usually reported—for example, Anopheles funestus after a large-scale distribution of long-lasting insecticidal nets—or insecticide resistance, in particular the current spread of pyrethroid resistance, could hamper the efficacy of classic pyrethroid-treated long-lasting insecticidal nets and maintained transmission. These issues must be well documented in every situation to elaborate, implement, monitor, and evaluate tailored vector control programs, keeping in mind that they must be conceived as integrated programs with several well and appropriately coordinated approaches, combining entomological but also parasitological, clinical, and social methods and analyses. A successful integrated vector control program must then be designed to reduce transmission and incidence rates of malaria morbidity and overall mortality.
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Affiliation(s)
- Pierre Carnevale
- Institut de Recherche pour le Développement, Portiragnes, France
| | - Sylvie Manguin
- HydroSciences Montpellier, Institut de Recherche pour le Développement (IRD), CNRS , Université Montpellier, Montpellier, France
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20
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Kaiser ML, Wood OR, Damiens D, Brooke BD, Koekemoer LL, Munhenga G. Estimates of the population size and dispersal range of Anopheles arabiensis in Northern KwaZulu-Natal, South Africa: implications for a planned pilot programme to release sterile male mosquitoes. Parasit Vectors 2021; 14:205. [PMID: 33874984 PMCID: PMC8056555 DOI: 10.1186/s13071-021-04674-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Accepted: 03/07/2021] [Indexed: 11/20/2022] Open
Abstract
Background Anopheles arabiensis is a major malaria vector, recently implicated as contributing to ongoing residual malaria transmission in South Africa, which feeds and rests both indoors and outdoors. This species is, therefore, not effectively targeted using core malaria vector control interventions alone. Additionally, increasing resistance to available insecticides necessitates investigations into complementary non-insecticide-based vector control methods for outdoor-resting mosquitoes. The feasibility of the sterile insect technique (SIT) as a complementary vector control intervention is being investigated in South Africa. Successful implementation of an SIT programme largely depends on inundating a target insect population with sterilized laboratory-bred males. Therefore, knowledge of the native population size and dispersal ability of released sterile laboratory-reared males is critical. In this study, we estimated the male An. arabiensis population size and the dispersal of released males in an area targeted for a pilot sterile male release programme. Methods Three separate releases were performed within a 2-year period. Approximately 5000–15,000 laboratory-reared male An. arabiensis (KWAG) were produced and marked for mark–release–recapture experiments. To recapture released mosquitoes, cloth tubes were deployed in widening concentric circles. The average dispersal distance of released males was calculated and the wild male An. arabiensis population size was estimated using two Lincoln index formulae. The natural population was sampled concurrently and Anopheles species diversity examined. Results The Anopheles gambiae complex and An. funestus group species made up the majority of wild collections along with other anophelines. The An. arabiensis population size was estimated to be between 550 and 9500 males per hectare depending on time of year, weather conditions and method used. Average dispersal distance of marked males ranged from 58 to 86 m. Marked males were found in swarms with wild males, indicating that laboratory-reared males are able to locate and participate in mating swarms. Conclusions It was logistically feasible to conduct mark–release–recapture studies at the current scale. The population size estimates obtained may provide a guideline for the initial number of males to use for a pending SIT pilot trial. It is promising for future SIT trials that laboratory-reared marked males participated in natural swarms, appearing at the right place at the right time. ![]()
Supplementary Information The online version contains supplementary material available at 10.1186/s13071-021-04674-w.
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Affiliation(s)
- Maria L Kaiser
- Centre for Emerging Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa. .,Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
| | - Oliver R Wood
- Centre for Emerging Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa.,Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - David Damiens
- UMR IRD 224, Maladies Infectieuses et Vecteurs-Ecologie-Génétique, Evolution et Contrôle (MIVEGEC), Institut de Recherche Pour Le Développement (IRD) CNRS 5290-Université de Montpellier, Montpellier, France.,IRD Réunion/GIP CYROI (Recherche Santé Bio-innovation), Sainte Clotilde, Reunion Island, France
| | - Basil D Brooke
- Centre for Emerging Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa.,Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Lizette L Koekemoer
- Centre for Emerging Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa.,Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Givemore Munhenga
- Centre for Emerging Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa.,Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
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21
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Abstract
Advances in genomics have led to an appreciation that introgression is common, but its evolutionary consequences are poorly understood. In recent species radiations the sharing of genetic variation across porous species boundaries can facilitate adaptation to new environments and generate novel phenotypes, which may contribute to further diversification. Most Anopheles mosquito species that are of major importance as human malaria vectors have evolved within recent and rapid radiations of largely nonvector species. Here, we focus on one of the most medically important yet understudied anopheline radiations, the Afrotropical Anopheles funestus complex (AFC), to investigate the role of introgression in its diversification and the possible link between introgression and vector potential. The AFC comprises at least seven morphologically similar species, yet only An. funestus sensu stricto is a highly efficient malaria vector with a pan-African distribution. Based on de novo genome assemblies and additional whole-genome resequencing, we use phylogenomic and population genomic analyses to establish species relationships. We show that extensive interspecific gene flow involving multiple species pairs has shaped the evolutionary history of the AFC since its diversification. The most recent introgression event involved a massive and asymmetrical movement of genes from a distantly related AFC lineage into An. funestus, an event that predated and plausibly facilitated its subsequent dramatic geographic range expansion across most of tropical Africa. We propose that introgression may be a common mechanism facilitating adaptation to new environments and enhancing vectorial capacity in Anopheles mosquitoes.
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22
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Bango ZA, Tawe L, Muthoga CW, Paganotti GM. Past and current biological factors affecting malaria in the low transmission setting of Botswana: A review. INFECTION, GENETICS AND EVOLUTION : JOURNAL OF MOLECULAR EPIDEMIOLOGY AND EVOLUTIONARY GENETICS IN INFECTIOUS DISEASES 2020; 85:104458. [PMID: 32668367 PMCID: PMC7354381 DOI: 10.1016/j.meegid.2020.104458] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 07/06/2020] [Accepted: 07/08/2020] [Indexed: 11/29/2022]
Abstract
Malaria continues to be one of the top infectious agents contributing to morbidity and mortality in sub-Saharan Africa. Annually, Botswana accounts only for a small proportion of cases (<<1%). Despite significantly reduced incidence rate, the country still experiences sporadic outbreaks that hamper the goal of malaria elimination. This review evaluated previous and current biological factors that impact malaria in Botswana, specifically focussing on the vectors, the parasite and the host. This was accomplished via a literature review evaluating these variables in Botswana. Current literature suggests that Anopheles arabiensis is the main malaria vector in the country. Several other potential vectors have been found widely distributed throughout Botswana in high numbers, yet remain largely unstudied with regards to their contribution to the country's malaria burden. We also report the most up to date list of all Anopheles species that have been found in Botswana. Plasmodium falciparum is responsible for the vast majority of symptomatic malaria in the country and some drug resistance markers have been documented for this species. Plasmodium vivax has been reported in asymptomatic subjects, even though a large proportion of the Botswana population appears to be Duffy antigen negative. Very little is known about the true distribution of P. vivax and no point of care testing infrastructure for this species exists in Botswana, making it difficult to tailor treatment to address possible recrudescence or relapse. Due to a genetically diverse population with a substantial Khoisan contribution into the Bantu genetic background, several phenotypes that potentially impact prevalence and severity of malaria exist within the country. These include sickle cell trait, Glucose-6-Phosphate Dehydrogenase deficiency, and Duffy negativity. This review highlights the information that currently exists on malaria in Botswana. It also postulates that a comprehensive understanding of these aforementioned biological factors may help to explain malaria persistence in Botswana.
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Affiliation(s)
| | - Leabaneng Tawe
- Botswana-University of Pennsylvania Partnership, Gaborone, Botswana; Department of Medical Laboratory Sciences, Faculty of Health Sciences, University of Botswana, Gaborone, Botswana
| | | | - Giacomo Maria Paganotti
- Botswana-University of Pennsylvania Partnership, Gaborone, Botswana; Division of Infectious Diseases, Perelman School of Medicine, University of Pennsylvania, PA, USA; Department of Biomedical Sciences, University of Botswana, Gaborone, Botswana.
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23
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Kakilla C, Manjurano A, Nelwin K, Martin J, Mashauri F, Kinung'hi SM, Lyimo E, Mangalu D, Bernard L, Iwuchukwu N, Mwalimu D, Serbantez N, Greer G, George K, Oxborough RM, Magesa SM. Malaria vector species composition and entomological indices following indoor residual spraying in regions bordering Lake Victoria, Tanzania. Malar J 2020; 19:383. [PMID: 33115495 PMCID: PMC7594290 DOI: 10.1186/s12936-020-03452-w] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Accepted: 10/18/2020] [Indexed: 11/17/2022] Open
Abstract
Background Vector control through long-lasting insecticidal nets (LLINs) and focal indoor residual spraying (IRS) is a major component of the Tanzania national malaria control strategy. In mainland Tanzania, IRS has been conducted annually around Lake Victoria basin since 2007. Due to pyrethroid resistance in malaria vectors, use of pyrethroids for IRS was phased out and from 2014 to 2017 pirimiphos-methyl (Actellic® 300CS) was sprayed in regions of Kagera, Geita, Mwanza, and Mara. Entomological surveillance was conducted in 10 sprayed and 4 unsprayed sites to determine the impact of IRS on entomological indices related to malaria transmission risk. Methods WHO cone bioassays were conducted monthly on interior house walls to determine residual efficacy of pirimiphos-methyl CS. Indoor CDC light traps with or without bottle rotator were hung next to protected sleepers indoors and also set outdoors (unbaited) as a proxy measure for indoor and outdoor biting rate and time of biting. Prokopack aspirators were used indoors to capture resting malaria vectors. A sub-sample of Anopheles was tested by PCR to determine species identity and ELISA for sporozoite rate. Results Annual IRS with Actellic® 300CS from 2015 to 2017 was effective on sprayed walls for a mean of 7 months in cone bioassay. PCR of 2016 and 2017 samples showed vector populations were predominantly Anopheles arabiensis (58.1%, n = 4,403 IRS sites, 58%, n = 2,441 unsprayed sites). There was a greater proportion of Anopheles funestus sensu stricto in unsprayed sites (20.4%, n = 858) than in sprayed sites (7.9%, n = 595) and fewer Anopheles parensis (2%, n = 85 unsprayed, 7.8%, n = 591 sprayed). Biting peaks of Anopheles gambiae sensu lato (s.l.) followed periods of rainfall occurring between October and April, but were generally lower in sprayed sites than unsprayed. In most sprayed sites, An. gambiae s.l. indoor densities increased between January and February, i.e., 10–12 months after IRS. The predominant species An. arabiensis had a sporozoite rate in 2017 of 2.0% (95% CI 1.4–2.9) in unsprayed sites compared to 0.8% (95% CI 0.5–1.3) in sprayed sites (p = 0.003). Sporozoite rates were also lower for An. funestus collected in sprayed sites. Conclusion This study contributes to the understanding of malaria vector species composition, behaviour and transmission risk following IRS around Lake Victoria and can be used to guide malaria vector control strategies in Tanzania.
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Affiliation(s)
| | | | - Karen Nelwin
- National Institute for Medical Research, Mwanza, Tanzania
| | | | | | | | - Eric Lyimo
- National Institute for Medical Research, Mwanza, Tanzania
| | - Doris Mangalu
- National Institute for Medical Research, Mwanza, Tanzania
| | - Lucy Bernard
- National Institute for Medical Research, Mwanza, Tanzania
| | | | - Dismasi Mwalimu
- National Malaria Control Program, Ministry of Health, Community Development, Gender, Elderly and Children, Dodoma, Tanzania
| | - Naomi Serbantez
- U.S. President's Malaria Initiative, Dar es Salaam, Tanzania
| | - George Greer
- U.S. President's Malaria Initiative, Dar es Salaam, Tanzania
| | - Kristen George
- U.S. President's Malaria Initiative, U.S. Agency for International Development, Washington, DC, USA
| | - Richard M Oxborough
- PMI AIRS/VectorLink Project, Abt Associates, 6130 Executive Blvd, Rockville, MD, 20852, USA
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24
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The Impact of Insecticide Pre-Exposure on Longevity, Feeding Succession, and Egg Batch Size of Wild Anopheles gambiae s.l. J Trop Med 2020; 2020:8017187. [PMID: 33061994 PMCID: PMC7539113 DOI: 10.1155/2020/8017187] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 09/11/2020] [Accepted: 09/19/2020] [Indexed: 11/18/2022] Open
Abstract
Background Insecticide resistance among the vector population is the main threat to existing control tools available. The current vector control management options rely on applications of recommended public health insecticides, mainly pyrethroids through long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS). Regular monitoring of insecticide resistance does not provide information on important factors that affect parasite transmission. Such factors include vector longevity, vector competence, feeding success, and fecundity. This study investigated the impacts of insecticide resistance on longevity, feeding behaviour, and egg batch size of Anopheles gambiae s.l. Method The larval sampling was conducted in rice fields using a standard dipper (350 ml) and reared to adults in field insectary. A WHO susceptibility test was conducted using standard treated permethrin (0.75%) and deltamethrin (0.05%) papers. The susceptible Kisumu strain was used for reference. Feeding succession and egg batch size were monitored for all survivors and control. Results The results revealed that mortality rates declined by 52.5 and 59.5% for permethrin and deltamethrin, respectively. The mortality rate for the Kisumu susceptible strain was 100%. The survival rates of wild An. gambiae s.l. was between 24 and 27 days. However, the Kisumu susceptible strain blood meal feeding was significantly higher than resistant colony (t = 2.789, df = 21, P=0.011). Additionally, the susceptible An. gambiae s.s. laid more eggs than the resistant An.gambiae s.l. colony (Χ2 = 1366, df = 1, P ≤ 0.05). Conclusion It can, therefore, be concluded that the wild An. gambiae s.l. had increased longevity, blood feeding, and small egg batch size compared to Kisumu susceptible colonies.
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25
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Semifield Evaluation of Improved Passive Outdoor Host Seeking Device (POHD) for Outdoor Control of Anopheles arabiensis Mosquitoes. ScientificWorldJournal 2020; 2020:8938309. [PMID: 32547328 PMCID: PMC7271259 DOI: 10.1155/2020/8938309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2019] [Revised: 03/07/2020] [Accepted: 04/13/2020] [Indexed: 12/03/2022] Open
Abstract
Despite the considerable progress made so far, the effectiveness and mass application of odour-baited outdoor mosquito control devices in pipelines is limited by several factors. These include the design and size of the devices, optimal placement of attractive blends, and nature of materials into which the blends are impregnated. The primary aim of this study was to manipulate these factors to improve the attractiveness of our recently developed passive outdoor host seeking device (POHD) to outdoor biting Anopheles arabiensis. Specifically, the study aimed to determine optimal placement of odour blends and killing bioactives in POHD for maximum attraction and killing of An. arabiensis and to assess the effects of blend types, formulation, and residual activity on attractiveness of the POHD to An. arabiensis. The POHDs baited with attractive blends, carbon dioxide (CO2), and bendiocarb-treated electrostatic netting were placed either towards the top or bottom openings, and other modifications were exposed to An. arabiensis under the semifield system at Ifakara Health Institute (IHI). Each night, a total of 100 starved female, 3–7-day-old, semifield reared An. arabiensis mosquitoes were released, collected the next morning (alive or dead), counted, and recorded. Live mosquitoes were maintained in the semifield insectary and monitored for 24 hours mortality. Each treatment combination of the POHD was tested in three replicates. Overall, the results indicated that the proportion of mosquitoes attracted to and killed in the POHD varied with position of attractants and killing agent (bendiocarb). The POHD with bottom placed attractants and bendiocarb attracted and killed higher proportion of mosquitoes compared to the POHD with top placed attractants and bendiocarb. The highest mortalities were observed when the POHD was baited with a combination of attractive blends and CO2. Moreover, the residual activity of attractive blends applied inside POHD varied with type and formulation of attractive blend. The POHD packed with Mbita and Ifakara blend in microencapsulated pellets (granules) attracted higher proportion of mosquitoes than that baited with soaked nylon-strip formulation of either blends. Interestingly, POHD baited with Mbita blend in microencapsulated pellets (granules) formulation attracted and killed higher proportion of mosquitoes (>90%) than that baited with Ifakara blend even 9 months after application. Conclusively, the POHD remained effective for a relatively longer period of time when baited with bottom placed synthetic blends and CO2 combination, thus warranting further trials under real life situations.
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26
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Braack L, Bornman R, Kruger T, Dahan-Moss Y, Gilbert A, Kaiser M, Oliver SV, Cornel AJ, Lee Y, Norris DE, Coetzee M, Brooke B, de Jager C. Malaria Vectors and Vector Surveillance in Limpopo Province (South Africa): 1927 to 2018. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2020; 17:ijerph17114125. [PMID: 32527067 PMCID: PMC7313001 DOI: 10.3390/ijerph17114125] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Revised: 06/05/2020] [Accepted: 06/06/2020] [Indexed: 11/16/2022]
Abstract
Despite the annual implementation of a robust and extensive indoor residual spraying programme against malaria vectors in Limpopo Province (South Africa), significant transmission continues and is a serious impediment to South Africa’s malaria elimination objectives. In order to gain a better understanding regarding possible causes of this residual malaria, we conducted a literature review of the historical species composition and abundance of malaria vector mosquitoes in the Limpopo River Valley region of the Vhembe District, northern Limpopo Province, the region with the highest remaining annual malaria cases in South Africa. In addition, mosquito surveys were carried out in the same region between October 2017 and October 2018. A total of 2225 adult mosquitoes were collected using CO2-baited tent and light traps, human landing catches and cow-baited traps. Of the 1443 Anopheles collected, 516 were members of the An. gambiae complex and 511 An. funestus group. In the malaria endemic rural areas outside the Kruger National Park, one specimen each of An. gambiae s.s. and An. funestus and only three of An. arabiensis were collected. The latter species was abundant at a remote hot spring in the neighboring Kruger National Park. Eighteen other species of Anopheles were collected. Our survey results support the historical findings that An. arabiensis, the species widely held to be the prime malaria vector in South Africa, is a rare species in the malaria endemic Limpopo River Valley. The implications of the mosquito surveys for malaria transmission, elimination and vector control in northern Limpopo Province and neighboring regions are discussed.
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Affiliation(s)
- Leo Braack
- University of Pretoria Institute for Sustainable Malaria Control, School of Health Systems and Public Health, Faculty of Health Sciences, University of Pretoria, Pretoria 0028, South Africa; (R.B.); (T.K.); (A.J.C.); (C.d.J.)
- Correspondence:
| | - Riana Bornman
- University of Pretoria Institute for Sustainable Malaria Control, School of Health Systems and Public Health, Faculty of Health Sciences, University of Pretoria, Pretoria 0028, South Africa; (R.B.); (T.K.); (A.J.C.); (C.d.J.)
| | - Taneshka Kruger
- University of Pretoria Institute for Sustainable Malaria Control, School of Health Systems and Public Health, Faculty of Health Sciences, University of Pretoria, Pretoria 0028, South Africa; (R.B.); (T.K.); (A.J.C.); (C.d.J.)
| | - Yael Dahan-Moss
- Vector Control Reference Laboratory, Centre for Emerging, Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg2001, South Africa; (Y.D.-M.); (A.G.); (M.K.); (S.V.O.); (M.C.); (B.B.)
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg 2001, South Africa
| | - Allison Gilbert
- Vector Control Reference Laboratory, Centre for Emerging, Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg2001, South Africa; (Y.D.-M.); (A.G.); (M.K.); (S.V.O.); (M.C.); (B.B.)
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg 2001, South Africa
| | - Maria Kaiser
- Vector Control Reference Laboratory, Centre for Emerging, Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg2001, South Africa; (Y.D.-M.); (A.G.); (M.K.); (S.V.O.); (M.C.); (B.B.)
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg 2001, South Africa
| | - Shüné V. Oliver
- Vector Control Reference Laboratory, Centre for Emerging, Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg2001, South Africa; (Y.D.-M.); (A.G.); (M.K.); (S.V.O.); (M.C.); (B.B.)
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg 2001, South Africa
| | - Anthony J. Cornel
- University of Pretoria Institute for Sustainable Malaria Control, School of Health Systems and Public Health, Faculty of Health Sciences, University of Pretoria, Pretoria 0028, South Africa; (R.B.); (T.K.); (A.J.C.); (C.d.J.)
- Department of Entomology & Nematology, University of California, Davis, CA 95616, USA;
| | - Yoosook Lee
- Department of Entomology & Nematology, University of California, Davis, CA 95616, USA;
| | - Douglas E. Norris
- The W Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA;
| | - Maureen Coetzee
- Vector Control Reference Laboratory, Centre for Emerging, Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg2001, South Africa; (Y.D.-M.); (A.G.); (M.K.); (S.V.O.); (M.C.); (B.B.)
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg 2001, South Africa
| | - Basil Brooke
- Vector Control Reference Laboratory, Centre for Emerging, Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg2001, South Africa; (Y.D.-M.); (A.G.); (M.K.); (S.V.O.); (M.C.); (B.B.)
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg 2001, South Africa
| | - Christiaan de Jager
- University of Pretoria Institute for Sustainable Malaria Control, School of Health Systems and Public Health, Faculty of Health Sciences, University of Pretoria, Pretoria 0028, South Africa; (R.B.); (T.K.); (A.J.C.); (C.d.J.)
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Dahan-Moss Y, Hendershot A, Dhoogra M, Julius H, Zawada J, Kaiser M, Lobo NF, Brooke BD, Koekemoer LL. Member species of the Anopheles gambiae complex can be misidentified as Anopheles leesoni. Malar J 2020; 19:89. [PMID: 32093677 PMCID: PMC7038563 DOI: 10.1186/s12936-020-03168-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Accepted: 02/17/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Accurate Anopheles species identification is key for effective malaria vector control. Identification primarily depends on morphological analysis of field samples as well as molecular species-specific identifications. During an intra-laboratory assessment (proficiency testing) of the Anopheles funestus group multiplex PCR assay, it was noted that Anopheles arabiensis can be misidentified as Anopheles leesoni, a zoophilic member of the An. funestus group. The aim of this project was, therefore, to ascertain whether other members of the Anopheles gambiae complex can also be misidentified as An. leesoni when using the standard An. funestus multiplex PCR. METHODS The An. funestus multiplex PCR was used to amplify DNA from An. gambiae complex specimens. These included specimens from the laboratory colonies and field samples from the Democratic Republic of Congo. Amplified DNA from these specimens, using the universal (UV) and An. leesoni species-specific primers (LEES), were sequence analysed. Additionally, An. leesoni DNA was processed through the diagnostic An. gambiae multiplex PCR to determine if this species can be misidentified as a member of the An. gambiae complex. RESULTS Laboratory-colonized as well as field-collected samples of An. arabiensis, An. gambiae, Anopheles merus, Anopheles quadriannulatus, Anopheles coluzzii as well as Anopheles moucheti produced an amplicon of similar size to that of An. leesoni when using an An. funestus multiplex PCR. Sequence analysis confirmed that the UV and LEES primers amplify a segment of the ITS2 region of members of the An. gambiae complex and An. moucheti. The reverse was not true, i.e. the An. gambiae multiplex PCR does not amplify DNA from An. leesoni. CONCLUSION This investigation shows that An. arabiensis, An. gambiae, An. merus, An. quadriannulatus, An. coluzzii and An. moucheti can be misidentified as An. leesoni when using An. funestus multiplex PCR. This shows the importance of identifying specimens using standard morphological dichotomous keys as far as possible prior to the use of appropriate PCR-based identification methods. Should there be doubt concerning field-collected specimens molecularly identified as An. leesoni, the An. gambiae multiplex PCR and sequencing of the internal transcribed spacer 2 (ITS2) can be used to eliminate false identifications.
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Affiliation(s)
- Yael Dahan-Moss
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa. .,Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
| | - Allison Hendershot
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, USA
| | - Minishca Dhoogra
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa.,Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Henry Julius
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa
| | - Jacek Zawada
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa.,Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Maria Kaiser
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa.,Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Neil F Lobo
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, USA
| | - Basil D Brooke
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa.,Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Lizette L Koekemoer
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa.,Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
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Musiime AK, Smith DL, Kilama M, Rek J, Arinaitwe E, Nankabirwa JI, Kamya MR, Conrad MD, Dorsey G, Akol AM, Staedke SG, Lindsay SW, Egonyu JP. Impact of vector control interventions on malaria transmission intensity, outdoor vector biting rates and Anopheles mosquito species composition in Tororo, Uganda. Malar J 2019; 18:445. [PMID: 31881898 PMCID: PMC6935116 DOI: 10.1186/s12936-019-3076-4] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Accepted: 12/14/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Long-lasting insecticidal nets (LLINs) and indoor residual spraying of insecticide (IRS) are widely recommended for the prevention of malaria in endemic regions. Data from human landing catches provide information on the impact of vector control on vector populations. Here, malaria transmission indoors and outdoors, before and after mass deployment of LLINs and IRS in Uganda was compared. METHODS The study took place in Tororo district, a historically high transmission area where universal LLIN distribution was conducted in November 2013 and May 2017 and 6 rounds of IRS implemented from December 2014 to July 2018. Human landing catches were performed in 8 houses monthly from October 2011 to September 2012 (pre-intervention period) and every 4 weeks from November 2017 to October 2018 (post-intervention period). Mosquitoes were collected outdoors from 18:00 to 22:00 h and indoors from 18:00 to 06:00 h. Female Anopheles were tested for the presence of Plasmodium falciparum sporozoites and species identification performed using gross dissection and polymerase chain reaction (PCR). RESULTS The interventions were associated with a decline in human biting rate from 19.6 to 2.3 female Anopheles mosquitoes per house per night (p < 0.001) and annual entomological inoculation rate from 129 to 0 infective bites per person per year (p < 0.001). The proportion of mosquitoes collected outdoors increased from 11.6 to 49.4% (p < 0.001). Prior to the interventions the predominant species was Anopheles gambiae sensu stricto (s.s.), which comprised an estimated 76.7% of mosquitoes. Following the interventions, the predominant species was Anopheles arabiensis, which comprised 99.5% of mosquitoes, with almost complete elimination of An. gambiae s.s. (0.5%). CONCLUSIONS Mass distribution of LLINs and 6 rounds of IRS dramatically decreased vector density and sporozoite rate resulting in a marked reduction in malaria transmission intensity in a historically high transmission site in Uganda. These changes were accompanied by a shift in vector species from An. gambiae s.s. to An. arabiensis and a relative increase in outdoor biting.
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Affiliation(s)
- Alex K Musiime
- Infectious Diseases Research Collaboration, Kampala, Uganda. .,Department of Zoology, Entomology and Fisheries Sciences, College of Natural Sciences, Makerere University, Kampala, Uganda.
| | - David L Smith
- Institute for Health Metrics & Evaluation, University of Washington, Seattle, WA, USA
| | - Maxwell Kilama
- Infectious Diseases Research Collaboration, Kampala, Uganda
| | - John Rek
- Infectious Diseases Research Collaboration, Kampala, Uganda
| | | | - Joaniter I Nankabirwa
- Infectious Diseases Research Collaboration, Kampala, Uganda.,Department of Medicine, Makerere University College of Health Sciences, Kampala, Uganda
| | - Moses R Kamya
- Infectious Diseases Research Collaboration, Kampala, Uganda.,Department of Medicine, Makerere University College of Health Sciences, Kampala, Uganda
| | - Melissa D Conrad
- Department of Medicine, University of California San Francisco, San Francisco, CA, USA
| | - Grant Dorsey
- Department of Medicine, University of California San Francisco, San Francisco, CA, USA
| | - Anne M Akol
- Department of Zoology, Entomology and Fisheries Sciences, College of Natural Sciences, Makerere University, Kampala, Uganda
| | - Sarah G Staedke
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK
| | | | - James P Egonyu
- Department of Zoology, Entomology and Fisheries Sciences, College of Natural Sciences, Makerere University, Kampala, Uganda.,International Center of Insect Physiology and Ecology, Nairobi, Kenya
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29
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Burke AM, Brooke BD, Duncan FD. Metabolic rate does not vary with seasonal change in Anopheles arabiensis adults in South Africa. JOURNAL OF INSECT PHYSIOLOGY 2019; 118:103942. [PMID: 31505200 DOI: 10.1016/j.jinsphys.2019.103942] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 07/24/2019] [Accepted: 09/06/2019] [Indexed: 06/10/2023]
Abstract
An important component of South Africa's malaria elimination agenda is identifying the entomological drivers of residual transmission, especially those that present opportunities for enhanced vector control. Seasonal mosquito density correlates directly with malaria transmission in South Africa. Transmission is highest during the warm rainy season and lowest but not entirely absent during the cooler dry season. The factors that sustain dry-season mosquito survival remain unknown. The aim of this project was therefore to investigate seasonal change in metabolic rate to determine the presence or absence of winter dormancy in malaria vector mosquitoes. Metabolic rate, determined by CO2 production during closed-system respirometry, was measured from wild anophelines collected from KwaZulu-Natal Province, South Africa. Monthly sampling spanned all four seasons (summer, autumn, winter, and spring) in 2017. Anopheles arabiensis and An. parensis specimens formed the majority of the total 437 identified specimens (n = 216 and n = 162, respectively). Metabolic rate data from wild-caught mosquitoes showed no significant seasonal disparities for An. arabiensis and An. parensis males and females. Further laboratory experiments assessed the effect of manipulated photoperiod, representing seasonal day-length changes, on the metabolic rate of colonized An. arabiensis mosquitoes. Simulations of midwinter (10 h:14 h light dark) and midsummer (14 h:10 h) day-length showed no significant effect on the metabolic rate of these mosquitoes. Age (in days) had a significant effect on the metabolic rate of both male and female colonized adult An. arabiensis mosquitoes which may be linked to developmental factors during maturation of adults. These data suggest that the South African populations of the malaria vector species An. arabiensis and An. parensis do not curtail their breeding and foraging activities during the colder and drier winter months. Overwintering by diapause does not appear to be triggered in the adult mosquito stage in An. arabiensis. However, their respective population densities do decrease considerably during winter leading to reduced malaria transmission and the opportunity for control by winter larviciding of known breeding sites.
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Affiliation(s)
- Ashley M Burke
- Wits Research Institute for Malaria and Wits/MRC Collaborating Centre for Multidisciplinary Research on Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa; Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg, South Africa
| | - Basil D Brooke
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg, South Africa; Wits Research Institute for Malaria and Wits/MRC Collaborating Centre for Multidisciplinary Research on Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Frances D Duncan
- School of Animal, Plant & Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa.
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