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Kang SY, Amratia P, Dunn J, Vilay P, Connell M, Symons T, Rumisha S, Zhang S, Ward A, Sichanthongthip O, Banouvong V, Shortus M, Reyburn R, Butphomvihane P, Phiphakavong V, Hahm M, Phongchantha V, Khamlome B, Chindavongsa K, Chanthavisouk C, Weiss DJ, Gething PW, Cameron E. Fine-scale maps of malaria incidence to inform risk stratification in Laos. Malar J 2024; 23:196. [PMID: 38918779 PMCID: PMC11202256 DOI: 10.1186/s12936-024-05007-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Accepted: 06/01/2024] [Indexed: 06/27/2024] Open
Abstract
BACKGROUND Malaria risk maps are crucial for controlling and eliminating malaria by identifying areas of varying transmission risk. In the Greater Mekong Subregion, these maps guide interventions and resource allocation. This article focuses on analysing changes in malaria transmission and developing fine-scale risk maps using five years of routine surveillance data in Laos (2017-2021). The study employed data from 1160 geolocated health facilities in Laos, along with high-resolution environmental data. METHODS A Bayesian geostatistical framework incorporating population data and treatment-seeking propensity was developed. The models incorporated static and dynamic factors and accounted for spatial heterogeneity. RESULTS Results showed a significant decline in malaria cases in Laos over the five-year period and a shift in transmission patterns. While the north became malaria-free, the south experienced ongoing transmission with sporadic outbreaks. CONCLUSION The risk maps provided insights into changing transmission patterns and supported risk stratification. These risk maps are valuable tools for malaria control in Laos, aiding resource allocation, identifying intervention gaps, and raising public awareness. The study enhances understanding of malaria transmission dynamics and facilitates evidence-based decision-making for targeted interventions in high-risk areas.
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Affiliation(s)
- Su Yun Kang
- Telethon Kids Institute, Perth Children's Hospital, Perth, Australia.
| | - Punam Amratia
- Telethon Kids Institute, Perth Children's Hospital, Perth, Australia.
- Ifakara Health Institute, Dar es Salaam, Tanzania.
| | - Julia Dunn
- Clinton Health Access Initiative, Boston, USA
| | - Phoutnalong Vilay
- Centre of Malariology, Parasitology and Entomology, Vientiane, Lao PDR
| | - Mark Connell
- Telethon Kids Institute, Perth Children's Hospital, Perth, Australia
| | - Tasmin Symons
- Telethon Kids Institute, Perth Children's Hospital, Perth, Australia
- Curtin University, Perth, Australia
| | - Susan Rumisha
- Telethon Kids Institute, Perth Children's Hospital, Perth, Australia
- Ifakara Health Institute, Dar es Salaam, Tanzania
| | - Song Zhang
- Telethon Kids Institute, Perth Children's Hospital, Perth, Australia
| | | | | | | | | | | | | | | | - Mary Hahm
- Clinton Health Access Initiative, Boston, USA
| | | | - Boualam Khamlome
- Centre of Malariology, Parasitology and Entomology, Vientiane, Lao PDR
| | | | | | - Daniel J Weiss
- Telethon Kids Institute, Perth Children's Hospital, Perth, Australia
- Curtin University, Perth, Australia
| | - Peter W Gething
- Telethon Kids Institute, Perth Children's Hospital, Perth, Australia
- Curtin University, Perth, Australia
| | - Ewan Cameron
- Telethon Kids Institute, Perth Children's Hospital, Perth, Australia
- Curtin University, Perth, Australia
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St Laurent B. Genomic complexity of parasites and vectors challenges malaria control in Southeast Asia. CURRENT OPINION IN INSECT SCIENCE 2023; 60:101113. [PMID: 37690774 DOI: 10.1016/j.cois.2023.101113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Revised: 09/02/2023] [Accepted: 09/05/2023] [Indexed: 09/12/2023]
Abstract
Southeast Asia is a uniquely complex region of malaria transmission that maintains an astounding level of species diversity among potential malaria vectors and also generates drug-resistant and quickly diverging populations of malaria parasites. All five human malaria species circulate in Southeast Asia with over 50 Anopheles species that vary in their ability to transmit these pathogens. The intricate relationships of these parasites and vectors are not well-understood. Human activity in Southeast Asian countries has created an increasingly fragmented landscape, bringing humans and mosquitoes into more frequent contact, sustaining malaria transmission in a region where few control tools are effective. Genomic shifts at the species, population, and individual level in parasites and vectors introduce variation that has produced drug- and insecticide resistance. The goal of this review is to highlight genomic studies of Southeast Asian malaria parasites and vectors that demonstrate how diversity in these organisms presents unique challenges and opportunities for global malaria control and eradication efforts.
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Marcombe S, Maithaviphet S, Reyburn R, Kunlaya K, Silavong K, Hongvanthong B, Vanisaveth V, Sengsavath V, Banouvong V, Chindavongsa K, Khamlome B, Shortus M. Bionomics of malaria vectors in Lao PDR, 2018-2020: entomological surveillance as a key tool for malaria elimination. Malar J 2023; 22:319. [PMID: 37865735 PMCID: PMC10589990 DOI: 10.1186/s12936-023-04754-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Accepted: 10/13/2023] [Indexed: 10/23/2023] Open
Abstract
BACKGROUND The Lao PDR National Strategic Plan for malaria control and elimination for year 2021-2025 emphasizes the importance of routine entomological surveillance being conducted in areas with high transmission and in active malaria foci in elimination targeted areas. The collection of entomological surveillance data that is closely linked to recent epidemiological data is crucial for improving impact, as it contributes to the evidence package that supports operational and strategic decision-making of national malaria programmes, as they accelerate their last mile of elimination. METHODS The Center for Malariology Parasitology and Epidemiology (CMPE) entomology team conducted entomological surveillance activities at 13 sentinel sites in 8 provinces and at active transmission foci sites from 2018 to 2020. The techniques used for the mosquito collection were indoor and outdoor human landing collections (from houses and from cultivation areas) and cattle baited net trap collections. RESULTS There were 5601 Anopheles mosquito females captured and identified throughout the study, on both human and cow bait. They represented 15 different species or species complexes. The primary malaria vectors as well as the secondary vectors were present in all collection sites in the south, indicating that people living in these rural areas with high malaria incidence are exposed to the vectors. The vectors were highly zoophilic, but they still bite humans throughout the night with a high peak of activity before midnight, both indoors and outdoors. Overall, 17% of the malaria vectors were collected indoors when the people are sleeping. This confirms the importance of bed net use during the night. Thirty-two percent of primary and secondary vectors were collected outdoors at times when people are usually awake and outdoors, which shows that people are exposed to potentially infectious mosquitoes and the importance of personal protection at these times. The findings showed that residual transmission may occur outdoors in the villages, and outside the villages in cultivation fields and forested areas. Epidemiological data showed that transmission was higher in surveillance sites which were targeted as part of a malaria response rather than sentinel sites. CONCLUSIONS Understanding where and how transmission is persisting, monitoring and mapping vector species distribution in areas with active transmission, monitoring biting trends, and designing evidence based and effective vector control interventions are critical to accelerating progress toward malaria elimination. In this context, the role of entomological surveillance combined with epidemiological data should be considered as a cornerstone in achieving malaria elimination.
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Affiliation(s)
| | - Santi Maithaviphet
- Center for Malariology, Parasitology and Entomology, Ministry of Health, Vientiane, Lao PDR
| | - Rita Reyburn
- World Health Organization, Saphanthong Tai Rd, Vientiane, Laos
| | | | - Khambang Silavong
- Center for Malariology, Parasitology and Entomology, Ministry of Health, Vientiane, Lao PDR
| | - Bouasy Hongvanthong
- Center for Malariology, Parasitology and Entomology, Ministry of Health, Vientiane, Lao PDR
| | - Viengxay Vanisaveth
- Center for Malariology, Parasitology and Entomology, Ministry of Health, Vientiane, Lao PDR
| | - Viengphone Sengsavath
- Center for Malariology, Parasitology and Entomology, Ministry of Health, Vientiane, Lao PDR
| | - Vilasack Banouvong
- Center for Malariology, Parasitology and Entomology, Ministry of Health, Vientiane, Lao PDR
| | | | - Boualam Khamlome
- Center for Malariology, Parasitology and Entomology, Ministry of Health, Vientiane, Lao PDR
| | - Matthew Shortus
- World Health Organization, Saphanthong Tai Rd, Vientiane, Laos
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Survey of malaria vectors on the Cambodia, Thailand and China-Laos Borders. Malar J 2022; 21:399. [PMID: 36585690 PMCID: PMC9801360 DOI: 10.1186/s12936-022-04418-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Accepted: 12/15/2022] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Anopheles maculatus, Anopheles minimus and Anopheles dirus are the major vectors of malaria transmission in the Greater Mekong Subregion (GMS). The malaria burden in this region has decreased significantly in recent years as all GMS countries progress towards malaria elimination. It is necessary to investigate the Anopheles diversity and abundance status and assess the Plasmodium infection rates to understand the malaria transmission potential of these vector species in GMS countries to guide the development of up-to-date vector control strategies and interventions. METHODS A survey of mosquitoes was conducted in Stung Treng, Sainyabuli and Phongsaly Provinces on the Cambodia-Laos, Thailand-Laos and China-Laos borders, respectively. Mosquito collection was done by overnight trapping at sentinel sites in each province. After morphological identification, the 18S rRNA-based nested-PCR was performed to detect malaria parasites in the captured Anopheles mosquitoes. RESULTS A total of 18 965 mosquitoes comprising of 35 species of 2 subgenera (Subgenus Anopheles and Subgenus Cellia) and 4 tribes (Tribes Culicini, Aedini, Armigerini and Mansoniini) were captured. Tribe Culicini accounted for 85.66% of captures, followed by Subgenus Anopheles (8.15%). Anopheles sinensis dominated the Subgenus Anopheles by 99.81%. Plasmodium-infection was found in 25 out of the 1 683 individual or pooled samples of Anopheles. Among the 25 positive samples, 19, 5 and 1 were collected from Loum, Pangkhom and Siem Pang village, respectively. Eight Anopheles species were found infected with Plasmodium, i.e., An. sinensis, Anopheles kochi, Anopheles vagus, An. minimus, Anopheles annularis, Anopheles philippinensis, Anopheles tessellatus and An. dirus. The infection rates of Plasmodium falciparum, Plasmodium vivax and mixture of Plasmodium parasite species were 0.12% (2/1 683), 1.31% (22/1 683) and 0.06% (1/1 683), respectively. CONCLUSIONS Overall, this survey re-confirmed that multiple Anopheles species carry malaria parasites in the international border areas of the GMS countries. Anopheles sinensis dominated the Anopheles collections and as carriers of malaria parasites, therefore may play a significant role in malaria transmission. More extensive investigations of malaria vectors are required to reveal the detailed vector biology, ecology, behaviour, and genetics in GMS regions in order to assist with the planning and implementation of improved malaria control strategies.
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Byrne I, Cramer E, Nelli L, Rerolle F, Wu L, Patterson C, Rosado J, Dumont E, Tetteh KKA, Dantzer E, Hongvanthong B, Fornace KM, Stresman G, Lover A, Bennett A, Drakeley C. Characterizing the spatial distribution of multiple malaria diagnostic endpoints in a low-transmission setting in Lao PDR. Front Med (Lausanne) 2022; 9:929366. [PMID: 36059850 PMCID: PMC9433740 DOI: 10.3389/fmed.2022.929366] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Accepted: 07/22/2022] [Indexed: 11/21/2022] Open
Abstract
The epidemiology of malaria changes as prevalence falls in low-transmission settings, with remaining infections becoming more difficult to detect and diagnose. At this stage active surveillance is critical to detect residual hotspots of transmission. However, diagnostic tools used in active surveillance generally only detect concurrent infections, and surveys may benefit from sensitive tools such as serological assays. Serology can be used to interrogate and characterize individuals' previous exposure to malaria over longer durations, providing information essential to the detection of remaining foci of infection. We ran blood samples collected from a 2016 population-based survey in the low-transmission setting of northern Lao PDR on a multiplexed bead assay to characterize historic and recent exposures to Plasmodium falciparum and vivax. Using geostatistical methods and remote-sensing data we assessed the environmental and spatial associations with exposure, and created predictive maps of exposure within the study sites. We additionally linked the active surveillance PCR and serology data with passively collected surveillance data from health facility records. We aimed to highlight the added information which can be gained from serology as a tool in active surveillance surveys in low-transmission settings, and to identify priority areas for national surveillance programmes where malaria risk is higher. We also discuss the issues faced when linking malaria data from multiple sources using multiple diagnostic endpoints.
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Affiliation(s)
- Isabel Byrne
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, United Kingdom
- *Correspondence: Isabel Byrne
| | - Estee Cramer
- Department of Biostatistics and Epidemiology, School of Public Health and Health Sciences, University of Massachusetts-Amherst, Amherst, MA, United States
| | - Luca Nelli
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, United Kingdom
| | - Francois Rerolle
- Malaria Elimination Initiative, The Global Health Group, University of California, San Francisco, San Francisco, CA, United States
- Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, CA, United States
| | - Lindsey Wu
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Catriona Patterson
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Jason Rosado
- Unit of Malaria: Parasites and Hosts, Institut Pasteur, Paris, France
- Infectious Diseases Epidemiology and Analytics G5 Unit, Institut Pasteur, Paris, France
| | - Elin Dumont
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Kevin K. A. Tetteh
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Emily Dantzer
- Malaria Elimination Initiative, The Global Health Group, University of California, San Francisco, San Francisco, CA, United States
| | - Bouasy Hongvanthong
- Center for Malariology, Parasitology and Entomology, Ministry of Health, Vientiane, Laos
| | - Kimberley M. Fornace
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, United Kingdom
| | - Gillian Stresman
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Andrew Lover
- Department of Biostatistics and Epidemiology, School of Public Health and Health Sciences, University of Massachusetts-Amherst, Amherst, MA, United States
| | - Adam Bennett
- Malaria Elimination Initiative, The Global Health Group, University of California, San Francisco, San Francisco, CA, United States
- Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, CA, United States
| | - Chris Drakeley
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, United Kingdom
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Vu NS, Hertz JC, Martin NJ, Tran TC, Fiorenzano JM, Tran PV, Nguyen HV, Dang AD, Tran DN, Motoki MT. Mosquitoes (Diptera: Culicidae) from Villages and Forest Areas of Rural Communes in Khanh Hoa and Binh Phuoc Provinces, Vietnam. JOURNAL OF MEDICAL ENTOMOLOGY 2021; 58:2264-2273. [PMID: 34144599 PMCID: PMC8577722 DOI: 10.1093/jme/tjab106] [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] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Indexed: 06/12/2023]
Abstract
This study presents the diversity of mosquitoes collected from communes, endemic with malaria and dengue, located in Khanh Hoa and Binh Phuoc Provinces, Vietnam. A total of 10,288 mosquitoes were collected in the village and forested sites using standard larval dippers, cow-baited traps, ultra-violet light traps, and mechanical aspirators. Mosquito taxa were identified morphologically and species complexes/groups were further characterized molecularly. Five genera of mosquitoes were morphologically identified: Anopheles Meigen (21 species), Aedes Meigen (2 species), Culex Linnaeus (5 species), Mansonia Blanchard sp., and Armigeres Theobald sp. The PCR-based identification methods allowed the distinction of members of Maculatus Group, Funestus Group, and Dirus Complex; and DNA barcodes enabled the further identification of the Barbirostris Complex. Data reported here include the first report of An. saeungae Taai & Harbach and An. wejchoochotei Taai & Harbach from Vietnam, and re-emphasizes the significance of using molecular data in an integrated systematic approach to identify cryptic species and better understand their role in disease transmission.
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Affiliation(s)
- Nam S Vu
- National Institute of Hygiene and Epidemiology, Medical Entomology and Zoology Department, Hai Ba Trung, Hanoi 100000, Vietnam
| | | | | | - Tu C Tran
- National Institute of Hygiene and Epidemiology, Medical Entomology and Zoology Department, Hai Ba Trung, Hanoi 100000, Vietnam
| | | | - Phong V Tran
- National Institute of Hygiene and Epidemiology, Medical Entomology and Zoology Department, Hai Ba Trung, Hanoi 100000, Vietnam
| | - Hoang V Nguyen
- National Institute of Hygiene and Epidemiology, Medical Entomology and Zoology Department, Hai Ba Trung, Hanoi 100000, Vietnam
| | - Anh D Dang
- National Institute of Hygiene and Epidemiology, Medical Entomology and Zoology Department, Hai Ba Trung, Hanoi 100000, Vietnam
| | - Duong N Tran
- National Institute of Hygiene and Epidemiology, Medical Entomology and Zoology Department, Hai Ba Trung, Hanoi 100000, Vietnam
| | - Maysa T Motoki
- Vysnova Partners Inc., Landover, MD, USA
- Department of Entomology, Natural Museum of Natural History, Smithsonian Institution, Museum Support Center, Suitland, MD, USA
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Maquart PO, Fontenille D, Rahola N, Yean S, Boyer S. Checklist of the mosquito fauna (Diptera, Culicidae) of Cambodia. ACTA ACUST UNITED AC 2021; 28:60. [PMID: 34374642 PMCID: PMC8354007 DOI: 10.1051/parasite/2021056] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Accepted: 07/04/2021] [Indexed: 11/14/2022]
Abstract
Between 2016 and 2020, the Medical and Veterinary Entomology unit of the Institut Pasteur du Cambodge collected over 230,000 mosquitoes. Based on this sampling effort, a checklist of 290 mosquito species in Cambodia is presented. This is the first attempt to list the Culicidae fauna of the country. We report 49 species for the first time in Cambodia. The 290 species belong to 20 genera: Aedeomyia (1 sp.), Aedes (55 spp.), Anopheles (53 spp.), Armigeres (26 spp.), Coquillettidia (3 spp.), Culex (57 spp.), Culiseta (1 sp.), Ficalbia (1 sp.), Heizmannia (10 spp.), Hodgesia (3 spp.), Lutzia (3 spp.), Malaya (2 spp.), Mansonia (5 spp.), Mimomyia (7 spp.), Orthopodomyia (3 spp.), Topomyia (4 spp.), Toxorhynchites (4 spp.), Tripteroides (6 spp.), Uranotaenia (27 spp.), and Verrallina (19 spp.). The Cambodian Culicidae fauna is discussed in its Southeast Asian context. Forty-three species are reported to be of medical importance, and are involved in the transmission of pathogens.
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Affiliation(s)
- Pierre-Olivier Maquart
- Medical and Veterinary Entomology Unit, Institut Pasteur du Cambodge 5, BP 983, Blvd. Monivong, 12201 Phnom Penh, Cambodia
| | - Didier Fontenille
- Medical and Veterinary Entomology Unit, Institut Pasteur du Cambodge 5, BP 983, Blvd. Monivong, 12201 Phnom Penh, Cambodia - MIVEGEC, University of Montpellier, CNRS, IRD, 911 Avenue Agropolis, 34394 Montpellier, France
| | - Nil Rahola
- MIVEGEC, University of Montpellier, CNRS, IRD, 911 Avenue Agropolis, 34394 Montpellier, France
| | - Sony Yean
- Medical and Veterinary Entomology Unit, Institut Pasteur du Cambodge 5, BP 983, Blvd. Monivong, 12201 Phnom Penh, Cambodia
| | - Sébastien Boyer
- Medical and Veterinary Entomology Unit, Institut Pasteur du Cambodge 5, BP 983, Blvd. Monivong, 12201 Phnom Penh, Cambodia
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Rasmussen C, Alonso P, Ringwald P. Current and emerging strategies to combat antimalarial resistance. Expert Rev Anti Infect Ther 2021; 20:353-372. [PMID: 34348573 DOI: 10.1080/14787210.2021.1962291] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
INTRODUCTION Since the spread of chloroquine resistance in Plasmodium falciparum in the 1960s, recommendations have been made on how to respond to antimalarial resistance. Only with the advent of artemisinin partial resistance were large scale efforts made in the Greater Mekong Subregion to carry out recommendations in a coordinated and well-funded manner. Independent emergence of parasites partially resistant to artemisinins has now been reported in Rwanda. AREAS COVERED We reviewed past recommendations and activities to respond to resistance as well as the research ongoing into new ways to stop or delay the spread of resistant parasites. EXPERT OPINION Inadequate information limits the options and support for a strong, coordinated response to artemisinin partial resistance in Africa, making better phenotypic and genotypic surveillance a priority. A response to resistance needs to address factors that may have hastened the emergence and could speed the spread, including overuse of drugs and lack of access to quality treatment. New ways to use the existing treatments in the response to resistance such as multiple first-lines are currently impeded by the limited number of drugs available.
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Affiliation(s)
| | - Pedro Alonso
- Global Malaria Programme, World Health Organization, Geneva, Switzerland
| | - Pascal Ringwald
- Global Malaria Programme, World Health Organization, Geneva, Switzerland
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Wamaket N, Khamprapa O, Chainarin S, Thamsawet P, Ninsaeng U, Thongsalee S, Suwan V, Sakolvaree J, Takhampunya R, Davidson SA, McCardle PW, Sa-Angchai P, Mukaka M, Kiattibutr K, Khamsiriwatchara A, Nguitragool W, Sattabongkot J, Sirichaisinthop J, Kobylinski KC. Anopheles bionomics in a malaria endemic area of southern Thailand. Parasit Vectors 2021; 14:378. [PMID: 34315509 PMCID: PMC8317318 DOI: 10.1186/s13071-021-04870-8] [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: 04/09/2021] [Accepted: 07/02/2021] [Indexed: 12/26/2022] Open
Abstract
Background Ivermectin mass drug administration (MDA) could accelerate malaria elimination in the Greater Mekong Subregion. This study was performed to characterize the bionomics of Anopheles in Surat Thani province, Thailand. Methods Mosquitoes were collected via human landing collections between February and October 2019. Anopheles mosquitoes were morphologically identified to species. Primary Anopheles malaria vectors were dissected to assess parity status, and a subset were evaluated for molecular identification and Plasmodium detection. Results A total of 17,348 mosquitoes were collected during the study period; of these, 5777 were Anopheles mosquitoes. Morphological studies identified 15 Anopheles species, of which the most abundant were Anopheles minimus (s.l.) (87.16%, n = 5035), An. dirus s.l. (7.05%, n = 407) and An. barbirostris s.l. (2.86%, n = 165). Molecular identification confirmed that of the An. minimus s.l. mosquitoes collected, 99.80% were An. minimus (s.s.) (n = 484) and 0.2% were An. aconitus (n = 1), of the An. dirus (s.l.) collected, 100% were An. baimaii (n = 348), and of the An. maculatus (s.l.) collected, 93.62% were An. maculatus (s.s.) (n = 44) and 6.38% were An. sawadwongporni (n = 3). No Anopheles mosquito tested was Plasmodium positive (0/879). An average of 11.46 Anopheles were captured per collector per night. There were differences between species in hour of collection (Kruskal–Wallis H-test: χ2 = 80.89, P < 0.0001, n = 5666), with more An. barbirostris (s.l.) and An. maculatus (s.l.) caught earlier compared to An. minimus (s.l.) (P = 0.0001 and P < 0.0001, respectively) and An. dirus (s.l.) (P = 0.0082 and P < 0.001, respectively). The proportion of parous An. minimus (s.l.) captured by hour increased throughout the night (Wald Chi-square: χ2 = 17.31, P = 0.000, odds ratio = 1.0535, 95% confidence interval 1.0279–1.0796, n = 3400). Overall, An. minimus (s.l.) parity was 67.68% (2375/3509) with an intra-cluster correlation of 0.0378. A power calculation determined that an An. minimus (s.l.) parity reduction treatment effect size = 34%, with four clusters per treatment arm and a minimum of 300 mosquitoes dissected per cluster, at an α = 0.05, will provide 82% power to detect a significant difference following ivermectin MDA. Conclusions The study area in Surat Thani province is an ideal location to evaluate the impact of ivermectin MDA on An. minimus parity. Graphical abstract ![]()
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Affiliation(s)
- Narenrit Wamaket
- Department of Entomology, Armed Forces Research Institute of Medical Sciences, Ratchathewi, Bangkok, Thailand.,Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Ratchathewi, Bangkok, Thailand
| | - Oranicha Khamprapa
- Department of Entomology, Armed Forces Research Institute of Medical Sciences, Ratchathewi, Bangkok, Thailand.,Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Ratchathewi, Bangkok, Thailand
| | - Sittinont Chainarin
- Department of Entomology, Armed Forces Research Institute of Medical Sciences, Ratchathewi, Bangkok, Thailand.,Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Ratchathewi, Bangkok, Thailand
| | - Panisa Thamsawet
- Surat Thani Vector-Borne Diseases Control Center 11.3, Muang, Surat Thani, Thailand
| | - Ubolrat Ninsaeng
- Surat Thani Vector-Borne Diseases Control Center 11.3, Muang, Surat Thani, Thailand
| | - Suttipong Thongsalee
- Surat Thani Vector-Borne Diseases Control Center 11.3, Muang, Surat Thani, Thailand
| | - Veerast Suwan
- Surat Thani Vector-Borne Diseases Control Center 11.3, Muang, Surat Thani, Thailand
| | - Jira Sakolvaree
- Department of Entomology, Armed Forces Research Institute of Medical Sciences, Ratchathewi, Bangkok, Thailand
| | - Ratree Takhampunya
- Department of Entomology, Armed Forces Research Institute of Medical Sciences, Ratchathewi, Bangkok, Thailand
| | - Silas A Davidson
- Department of Entomology, Armed Forces Research Institute of Medical Sciences, Ratchathewi, Bangkok, Thailand
| | - Patrick W McCardle
- Department of Entomology, Armed Forces Research Institute of Medical Sciences, Ratchathewi, Bangkok, Thailand
| | - Patiwat Sa-Angchai
- Department of Tropical Hygiene, Faculty of Tropical Medicine, Mahidol University, Ratchathewi, Bangkok, Thailand
| | - Mavuto Mukaka
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Ratchathewi, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Kirakorn Kiattibutr
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Ratchathewi, Bangkok, Thailand
| | - Amnat Khamsiriwatchara
- Center of Excellence for Biomedical and Public Health Informatics, Faculty of Tropical Medicine, Mahidol University, Ratchathewi, Bangkok, Thailand
| | - Wang Nguitragool
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Ratchathewi, Bangkok, Thailand.,Department of Molecular Tropical Medicine and Genetics, Faculty of Tropical Medicine, Mahidol University, Ratchathewi, Bangkok, Thailand
| | - Jetsumon Sattabongkot
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Ratchathewi, Bangkok, Thailand
| | | | - Kevin C Kobylinski
- Department of Entomology, Armed Forces Research Institute of Medical Sciences, Ratchathewi, Bangkok, Thailand.
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Vantaux A, Riehle MM, Piv E, Farley EJ, Chy S, Kim S, Corbett AG, Fehrman RL, Pepey A, Eiglmeier K, Lek D, Siv S, Mueller I, Vernick KD, Witkowski B. Anopheles ecology, genetics and malaria transmission in northern Cambodia. Sci Rep 2021; 11:6458. [PMID: 33742030 PMCID: PMC7979810 DOI: 10.1038/s41598-021-85628-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 03/04/2021] [Indexed: 12/20/2022] Open
Abstract
In the Greater Mekong Subregion, malaria cases have significantly decreased but little is known about the vectors or mechanisms responsible for residual malaria transmission. We analysed a total of 3920 Anopheles mosquitoes collected during the rainy and dry seasons from four ecological settings in Cambodia (villages, forested areas near villages, rubber tree plantations and forest sites). Using odor-baited traps, 81% of the total samples across all sites were collected in cow baited traps, although 67% of the samples attracted by human baited traps were collected in forest sites. Overall, 20% of collected Anopheles were active during the day, with increased day biting during the dry season. 3131 samples were identified morphologically as 14 different species, and a subset was also identified by DNA amplicon sequencing allowing determination of 29 Anopheles species. The investigation of well characterized insecticide mutations (ace-1, kdr, and rdl genes) indicated that individuals carried mutations associated with response to all the different classes of insecticides. There also appeared to be a non-random association between mosquito species and insecticide resistance with Anopheles peditaeniatus exhibiting nearly fixed mutations. Molecular screening for Plasmodium sp. presence indicated that 3.6% of collected Anopheles were positive, most for P. vivax followed by P. falciparum. These results highlight some of the key mechanisms driving residual human malaria transmission in Cambodia, and illustrate the importance of diverse collection methods, sites and seasons to avoid bias and better characterize Anopheles mosquito ecology in Southeast Asia.
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Affiliation(s)
- Amélie Vantaux
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia.
| | - Michelle M Riehle
- Department of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Eakpor Piv
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | - Elise J Farley
- Department of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Sophy Chy
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | - Saorin Kim
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | - Anneli G Corbett
- Department of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Rachel L Fehrman
- Department of Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Anais Pepey
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
| | - Karin Eiglmeier
- Unit of Insect Vector Genetics and Genomics, Department of Parasites and Insect Vectors, Institut Pasteur, Paris, France.,CNRS Unit of Evolutionary Genomics, Modeling, and Health (UMR2000), Institut Pasteur, Paris, France
| | - Dysoley Lek
- National Center for Parasitology, Entomology and Malaria Control Program, Phnom Penh, Cambodia.,School of Public Health, National Institute of Public Health, Phnom Penh, Cambodia
| | - Sovannaroth Siv
- National Center for Parasitology, Entomology and Malaria Control Program, Phnom Penh, Cambodia
| | - Ivo Mueller
- Malaria: Parasites and Hosts Unit, Institut Pasteur, Paris, France
| | - Kenneth D Vernick
- Unit of Insect Vector Genetics and Genomics, Department of Parasites and Insect Vectors, Institut Pasteur, Paris, France.,CNRS Unit of Evolutionary Genomics, Modeling, and Health (UMR2000), Institut Pasteur, Paris, France
| | - Benoit Witkowski
- Malaria Molecular Epidemiology Unit, Institut Pasteur du Cambodge, Phnom Penh, Cambodia
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