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Kearney EA, Amratia P, Kang SY, Agius PA, Alene KA, O’Flaherty K, Oo WH, Cutts JC, Htike W, Da Silva Goncalves D, Razook Z, Barry AE, Drew D, Thi A, Aung KZ, Thu HK, Thein MM, Zaw NN, Htay WYM, Soe AP, Beeson JG, Simpson JA, Gething PW, Cameron E, Fowkes FJI. Geospatial joint modeling of vector and parasite serology to microstratify malaria transmission. Proc Natl Acad Sci U S A 2024; 121:e2320898121. [PMID: 38833464 PMCID: PMC11181033 DOI: 10.1073/pnas.2320898121] [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: 11/28/2023] [Accepted: 04/30/2024] [Indexed: 06/06/2024] Open
Abstract
The World Health Organization identifies a strong surveillance system for malaria and its mosquito vector as an essential pillar of the malaria elimination agenda. Anopheles salivary antibodies are emerging biomarkers of exposure to mosquito bites that potentially overcome sensitivity and logistical constraints of traditional entomological surveys. Using samples collected by a village health volunteer network in 104 villages in Southeast Myanmar during routine surveillance, the present study employs a Bayesian geostatistical modeling framework, incorporating climatic and environmental variables together with Anopheles salivary antigen serology, to generate spatially continuous predictive maps of Anopheles biting exposure. Our maps quantify fine-scale spatial and temporal heterogeneity in Anopheles salivary antibody seroprevalence (ranging from 9 to 99%) that serves as a proxy of exposure to Anopheles bites and advances current static maps of only Anopheles occurrence. We also developed an innovative framework to perform surveillance of malaria transmission. By incorporating antibodies against the vector and the transmissible form of malaria (sporozoite) in a joint Bayesian geostatistical model, we predict several foci of ongoing transmission. In our study, we demonstrate that antibodies specific for Anopheles salivary and sporozoite antigens are a logistically feasible metric with which to quantify and characterize heterogeneity in exposure to vector bites and malaria transmission. These approaches could readily be scaled up into existing village health volunteer surveillance networks to identify foci of residual malaria transmission, which could be targeted with supplementary interventions to accelerate progress toward elimination.
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Affiliation(s)
- Ellen A. Kearney
- Disease Elimination Program, Burnet Institute, Melbourne, VIC3004, Australia
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, VIC3010, Australia
| | - Punam Amratia
- Malaria Atlas Project, Telethon Kids Institute, Perth, WA6009, Australia
| | - Su Yun Kang
- Malaria Atlas Project, Telethon Kids Institute, Perth, WA6009, Australia
| | - Paul A. Agius
- Disease Elimination Program, Burnet Institute, Melbourne, VIC3004, Australia
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, VIC3010, Australia
- Biostatistics Unit, Faculty of Health, Deakin University, Melbourne, VIC3125, Australia
| | - Kefyalew Addis Alene
- Malaria Atlas Project, Telethon Kids Institute, Perth, WA6009, Australia
- Faculty of Health Sciences, Curtin University, Perth, WA6102, Australia
| | | | - Win Han Oo
- Health Security and Malaria Program, Burnet Institute Myanmar, Yangon11201, Myanmar
| | - Julia C. Cutts
- Disease Elimination Program, Burnet Institute, Melbourne, VIC3004, Australia
- Department of Medicine at the Doherty Institute, The University of Melbourne, Melbourne, VIC3000, Australia
| | - Win Htike
- Health Security and Malaria Program, Burnet Institute Myanmar, Yangon11201, Myanmar
| | | | - Zahra Razook
- Disease Elimination Program, Burnet Institute, Melbourne, VIC3004, Australia
- Institute for Physical and Mental Health and Clinical Translation, School of Medicine, Deakin University, Geelong, VIC3216, Australia
| | - Alyssa E. Barry
- Disease Elimination Program, Burnet Institute, Melbourne, VIC3004, Australia
- Institute for Physical and Mental Health and Clinical Translation, School of Medicine, Deakin University, Geelong, VIC3216, Australia
| | - Damien Drew
- Disease Elimination Program, Burnet Institute, Melbourne, VIC3004, Australia
| | - Aung Thi
- Department of Public Health, Myanmar Ministry of Health and Sports, Nay Pyi Taw15011, Myanmar
| | - Kyaw Zayar Aung
- Health Security and Malaria Program, Burnet Institute Myanmar, Yangon11201, Myanmar
| | - Htin Kyaw Thu
- Health Security and Malaria Program, Burnet Institute Myanmar, Yangon11201, Myanmar
| | - Myat Mon Thein
- Health Security and Malaria Program, Burnet Institute Myanmar, Yangon11201, Myanmar
| | - Nyi Nyi Zaw
- Health Security and Malaria Program, Burnet Institute Myanmar, Yangon11201, Myanmar
| | - Wai Yan Min Htay
- Health Security and Malaria Program, Burnet Institute Myanmar, Yangon11201, Myanmar
| | - Aung Paing Soe
- Health Security and Malaria Program, Burnet Institute Myanmar, Yangon11201, Myanmar
| | - James G. Beeson
- Disease Elimination Program, Burnet Institute, Melbourne, VIC3004, Australia
- Department of Infectious Diseases, The University of Melbourne, Melbourne, VIC3000, Australia
- Department of Microbiology, Monash University, Melbourne, VIC3800, Australia
- Central Clinical School, Monash University, Melbourne, VIC3004, Australia
| | - Julie A. Simpson
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, VIC3010, Australia
| | - Peter W. Gething
- Malaria Atlas Project, Telethon Kids Institute, Perth, WA6009, Australia
- Faculty of Health Sciences, Curtin University, Perth, WA6102, Australia
| | - Ewan Cameron
- Malaria Atlas Project, Telethon Kids Institute, Perth, WA6009, Australia
- Faculty of Health Sciences, Curtin University, Perth, WA6102, Australia
| | - Freya J. I. Fowkes
- Disease Elimination Program, Burnet Institute, Melbourne, VIC3004, Australia
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, VIC3010, Australia
- Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, VIC3004, Australia
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Ronse M, Nguyen TT, Nguyen XX, Ingelbeen B, Schneiders ML, Tran DT, Muela Ribera J, Gryseels C, Peeters Grietens K. Use of antimicrobials and other medical products in an ethnic minority context of South-Central Vietnam: A qualitative study of vulnerability. PLOS GLOBAL PUBLIC HEALTH 2024; 4:e0002982. [PMID: 38593159 PMCID: PMC11003614 DOI: 10.1371/journal.pgph.0002982] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Accepted: 02/09/2024] [Indexed: 04/11/2024]
Abstract
Despite the global threat of antimicrobial resistance (AMR), evidence on the use and quality of medicines at community level is limited, particularly in impoverished, rural areas where prevalence of (bacterial) infections is high. To better understand the processes that drive vulnerability to AMR' effects, this study aimed to assess social factors underpinning access to-and use of-medical products and healthcare, among people from the Raglai ethnic minority in Ninh Thuan Province, Vietnam. We conducted ethnographic research in eight villages in 2018-2019, using interviewing and participant observation methods for data collection. Different types of informants (including community members and healthcare providers) were selected using purposive sampling strategies and analysis was retroductive. Our findings show that, despite the existence of a government-funded health insurance scheme, Raglai people's flexible therapeutic itineraries did not systematically start with formal healthcare. Different types of care (private/informal, public, shamanic) were combined in parallel or in alternation, determined by distance to the provider, cost, workload, perceived diagnostic capacity, perceived severity and aetiology of the illness, and trust in the provider. Available medicines were often tablets dispensed in plastic bags containing labelled tablets, unlabelled tablets (in bulk) or tablets ground to powder. Treatment was often considered effective when it relieved symptoms, which led to abandonment of the treatment course. When symptoms did not speedily abate, the illness aetiology would be reinterpreted, and "stronger" medicines would be sought. The precarious socio-economic status of some Raglai drove them in cycles of severe poverty when additional unforeseen factors such as illness, animal disease or loss of crops arose, hampering access to (in)formal healthcare providers and/or appropriate diagnosis and treatment. We conclude that Raglai communities are structurally unable to buffer themselves against the threat and consequences of AMR. Despite this vulnerability, they are among the least targeted by efforts to optimize antibiotic use, which are concentrated in secondary and tertiary healthcare facilities targeted at urban populations.
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Affiliation(s)
- Maya Ronse
- Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium
| | - Thuan Thi Nguyen
- Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium
- Department of Malaria Epidemiology, National Institute of Malariology, Parasitology, and Entomology, Hanoi, Vietnam
| | - Xa Xuan Nguyen
- Department of Malaria Epidemiology, National Institute of Malariology, Parasitology, and Entomology, Hanoi, Vietnam
| | - Brecht Ingelbeen
- Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium
| | | | - Duong Thanh Tran
- Department of Malaria Epidemiology, National Institute of Malariology, Parasitology, and Entomology, Hanoi, Vietnam
| | - Joan Muela Ribera
- Department of Anthropology, Philosophy and Social Work, Rovira i Virgili, Tarragona, Spain
| | - Charlotte Gryseels
- Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium
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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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Van Dung N, Thieu NQ, Canh HD, Le Duy B, Hung VV, Ngoc NTH, Mai NVT, Van Anh NT, Son LD, Oo WH, Htike W, Oo MC, Galau NH, Thu KM, Zaw AK, Htwe EP, Cutts JC, Kearney EA, Wang B, Agius PA, Fowkes FJI, O'Flaherty K. Anopheles diversity, biting behaviour and transmission potential in forest and farm environments of Gia Lai province, Vietnam. Malar J 2023; 22:204. [PMID: 37408026 DOI: 10.1186/s12936-023-04631-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Accepted: 06/20/2023] [Indexed: 07/07/2023] Open
Abstract
BACKGROUND Despite recent reductions in Vietnam, malaria transmission persists in some areas in forests and farmlands where a high density of Anopheles mosquitoes relative to other environments occurs. To inform effective malaria control measures, it is important to understand vector bionomics and the malaria transmission role of Anopheles spp. in the highland regions of Vietnam. This study was conducted to quantify the abundance, composition and biting behaviour of the Anopheles mosquito population, and the proportion of Plasmodium spp. infected mosquitoes collected from forest and agricultural farm sites in Gia Lai province, Vietnam. METHODS Forest and agricultural farm sites in Gia Lai province were selected for mosquito collections (total eight sites). Mosquito collection was performed by Human-baited Double Net Trap (HDNT), animal-baited traps (ABT) using cattle, and CDC light traps. Captured mosquitoes were identified morphologically, and salivary glands of Anopheles mosquitoes were examined for sporozoites using microscopy. Plasmodium infection was determined by Polymerase Chain Reaction (PCR), and identification of blood meal type was determined by PCR and diffuse serum agglutination assay. RESULTS A total of 1815 Anopheles mosquitoes belonging to 19 species were collected by ABT (n = 1169), HDNT (n = 471) and CDC light trap (n = 175). Anopheles abundance and diversity varied by district and environment. Capture by HDNT of Anopheles of vectorial concern was observed between early evening and early morning. Plasmodium vivax infection was determined by PCR in two Anopheles dirus specimens captured by HDNT in forest sites. Blood from a range of hosts could, including human blood, could be detected in species considered primary and secondary vectors An. dirus, and Anopheles aconitus, and Anopheles maculatus, respectively. CONCLUSIONS A low number of Anopheles spp. considered primary vectors of concern and very low numbers of Plasmodium spp. infected Anopheles mosquitoes were captured at the end of the rainy season in the Central Highlands of Vietnam. However, capture species of vectorial concern by HDNT throughout the early to late evening demonstrates that use of additional personal protective measures could supplement current preventative measures, such as bed nets to prevent exposure to vectors of concern in this region.
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Affiliation(s)
- Nguyen Van Dung
- National Institute of Malariology, Parasitology and Entomology, Hanoi, Vietnam.
| | - Nguyen Quang Thieu
- National Institute of Malariology, Parasitology and Entomology, Hanoi, Vietnam
| | - Hoang Dinh Canh
- National Institute of Malariology, Parasitology and Entomology, Hanoi, Vietnam
| | - Bui Le Duy
- National Institute of Malariology, Parasitology and Entomology, Hanoi, Vietnam
| | - Vu Viet Hung
- National Institute of Malariology, Parasitology and Entomology, Hanoi, Vietnam
| | | | | | | | - Le Duy Son
- Health Poverty Action Vietnam, Hanoi, Vietnam
| | - Win Han Oo
- Health Security Program, Burnet Institute Myanmar, Yangon, Myanmar
| | - Win Htike
- Health Security Program, Burnet Institute Myanmar, Yangon, Myanmar
| | - May Chan Oo
- Health Security Program, Burnet Institute Myanmar, Yangon, Myanmar
| | - Naw Hkawng Galau
- Health Security Program, Burnet Institute Myanmar, Yangon, Myanmar
| | - Kaung Myat Thu
- Health Security Program, Burnet Institute Myanmar, Yangon, Myanmar
| | - Aung Khine Zaw
- Health Security Program, Burnet Institute Myanmar, Yangon, Myanmar
| | - Ei Phyu Htwe
- Health Security Program, Burnet Institute Myanmar, Yangon, Myanmar
| | - Julia C Cutts
- Disease Elimination Program, Burnet Institute, Melbourne, Australia
- Department of Medicine, The University of Melbourne, Melbourne, Australia
| | - Ellen A Kearney
- Disease Elimination Program, Burnet Institute, Melbourne, Australia
- Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia
| | | | - Paul A Agius
- Disease Elimination Program, Burnet Institute, Melbourne, Australia
- Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia
- Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia
- Biostatistics Unit, Faculty of Health, Deakin University, Melbourne, Australia
| | - Freya J I Fowkes
- Disease Elimination Program, Burnet Institute, Melbourne, Australia
- Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia
- Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia
- Department of Infectious Diseases, Monash University, Melbourne, Australia
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5
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Vajda ÉA, Saeung M, Ross A, McIver DJ, Tatarsky A, Moore SJ, Lobo NF, Chareonviriyaphap T. A semi-field evaluation in Thailand of the use of human landing catches (HLC) versus human-baited double net trap (HDN) for assessing the impact of a volatile pyrethroid spatial repellent and pyrethroid-treated clothing on Anopheles minimus landing. Malar J 2023; 22:202. [PMID: 37400831 PMCID: PMC10318828 DOI: 10.1186/s12936-023-04619-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 06/10/2023] [Indexed: 07/05/2023] Open
Abstract
BACKGROUND The mosquito landing rate measured by human landing catches (HLC) is the conventional endpoint used to evaluate the impact of vector control interventions on human-vector exposure. Non-exposure based alternatives to the HLC are desirable to minimize the risk of accidental mosquito bites. One such alternative is the human-baited double net trap (HDN), but the estimated personal protection of interventions using the HDN has not been compared to the efficacy estimated using HLC. This semi-field study in Sai Yok District, Kanchanaburi Province, Thailand, evaluates the performance of the HLC and the HDN for estimating the effect on Anopheles minimus landing rates of two intervention types characterized by contrasting modes of action, a volatile pyrethroid spatial repellent (VSPR) and insecticide-treated clothing (ITC). METHODS Two experiments to evaluate the protective efficacy of (1) a VPSR and (2) ITC, were performed. A block randomized cross-over design over 32 nights was carried out with both the HLC or HDN. Eight replicates per combination of collection method and intervention or control arm were conducted. For each replicate, 100 An. minimus were released and were collected for 6 h. The odds ratio (OR) of the released An. minimus mosquitoes landing in the intervention compared to the control arm was estimated using logistic regression, including collection method, treatment, and experimental day as fixed effects. RESULTS For the VPSR, the protective efficacy was similar for the two methods: 99.3%, 95% CI (99.5-99.0) when measured by HLC, and 100% (100, Inf) when measured by HDN where no mosquitoes were caught (interaction test p = 0.99). For the ITC, the protective efficacy was 70% (60-77%) measured by HLC but there was no evidence of protection when measured by HDN [4% increase (15-27%)] (interaction test p < 0.001). CONCLUSIONS Interactions between mosquitoes, bite prevention tools and the sampling method may impact the estimated intervention protective efficacy. Consequently, the sampling method must be considered when evaluating these interventions. The HDN is a valid alternative trapping method (relative to the HLC) for evaluating the impact of bite prevention methods that affect mosquito behaviour at a distance (e.g. VPSR), but not for interventions that operate through tarsal contact (e.g., ITC).
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Affiliation(s)
- Élodie A Vajda
- Malaria Elimination Initiative, University of California, 550 16th street, San Francisco, CA, 94158, USA.
- Swiss Tropical and Public Health Institute (Swiss TPH), Kreuzstrasse 2, 4123, Allschwil, Switzerland.
- University of Basel, Petersplatz 1, CH-2003, Basel, Switzerland.
| | - Manop Saeung
- Kasetsart University, 50 Thanon Ngamwongwan, Lat Yao, Chatuchak, Bangkok, 10900, Thailand
| | - Amanda Ross
- Swiss Tropical and Public Health Institute (Swiss TPH), Kreuzstrasse 2, 4123, Allschwil, Switzerland
- University of Basel, Petersplatz 1, CH-2003, Basel, Switzerland
| | - David J McIver
- Malaria Elimination Initiative, University of California, 550 16th street, San Francisco, CA, 94158, USA
| | - Allison Tatarsky
- Malaria Elimination Initiative, University of California, 550 16th street, San Francisco, CA, 94158, USA
| | - Sarah J Moore
- Swiss Tropical and Public Health Institute (Swiss TPH), Kreuzstrasse 2, 4123, Allschwil, Switzerland
- University of Basel, Petersplatz 1, CH-2003, Basel, Switzerland
- Vector Control Product Testing Unit, Department of Environmental and Ecological Sciences, Ifakara Health Institute, P.O. Box 74, Bagamoyo, Tanzania
- Nelson Mandela African Institute of Science and Technology (NM-AIST), P.O. Box 447, Tengeru, Tanzania
| | - Neil F Lobo
- Malaria Elimination Initiative, University of California, 550 16th street, San Francisco, CA, 94158, USA
- University of Notre Dame, Notre Dame, IN, 46556, USA
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6
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Kobylinski KC, Tipthara P, Wamaket N, Chainarin S, Kullasakboonsri R, Sriwichai P, Phasomkusolsil S, Hanboonkunupakarn B, Jittamala P, Gemmell R, Boyle J, Wrigley S, Steele J, White NJ, Tarning J. Ivermectin metabolites reduce Anopheles survival. Sci Rep 2023; 13:8131. [PMID: 37208382 DOI: 10.1038/s41598-023-34719-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Accepted: 05/05/2023] [Indexed: 05/21/2023] Open
Abstract
Ivermectin mass drug administration to humans or livestock is a potential vector control tool for malaria elimination. The mosquito-lethal effect of ivermectin in clinical trials exceeds that predicted from in vitro laboratory experiments, suggesting that ivermectin metabolites have mosquito-lethal effect. The three primary ivermectin metabolites in humans (i.e., M1 (3″-O-demethyl ivermectin), M3 (4-hydroxymethyl ivermectin), and M6 (3″-O-demethyl, 4-hydroxymethyl ivermectin) were obtained by chemical synthesis or bacterial modification/metabolism. Ivermectin and its metabolites were mixed in human blood at various concentrations, blood-fed to Anopheles dirus and Anopheles minimus mosquitoes, and mortality was observed daily for fourteen days. Ivermectin and metabolite concentrations were quantified by liquid chromatography linked with tandem mass spectrometry to confirm the concentrations in the blood matrix. Results revealed that neither the LC50 nor LC90 values differed between ivermectin and its major metabolites for An. dirus or An. minimus., Additionally, there was no substantial differences in the time to median mosquito mortality when comparing ivermectin and its metabolites, demonstrating an equal rate of mosquito killing between the compounds evaluated. These results demonstrate that ivermectin metabolites have a mosquito-lethal effect equal to the parent compound, contributing to Anopheles mortality after treatment of humans.
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Affiliation(s)
- Kevin C Kobylinski
- Department of Entomology, Armed Forces Research Institute of Medical Sciences, 315/6 Rajvithi Road, Bangkok, 10400, Thailand.
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Road, Ratchathewi, Bangkok, 10400, Thailand.
| | - Phornpimon Tipthara
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Road, Ratchathewi, Bangkok, 10400, Thailand
| | - Narenrit Wamaket
- Department of Entomology, Armed Forces Research Institute of Medical Sciences, 315/6 Rajvithi Road, Bangkok, 10400, Thailand
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Road, Ratchathewi, Bangkok, 10400, Thailand
| | - Sittinont Chainarin
- Department of Entomology, Armed Forces Research Institute of Medical Sciences, 315/6 Rajvithi Road, Bangkok, 10400, Thailand
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Road, Ratchathewi, Bangkok, 10400, Thailand
| | - Rattawan Kullasakboonsri
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Road, Ratchathewi, Bangkok, 10400, Thailand
| | - Patchara Sriwichai
- Department of Medical Entomology, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Road, Ratchathewi, Bangkok, 10400, Thailand
| | - Siriporn Phasomkusolsil
- Department of Entomology, Armed Forces Research Institute of Medical Sciences, 315/6 Rajvithi Road, Bangkok, 10400, Thailand
| | - Borimas Hanboonkunupakarn
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Road, Ratchathewi, Bangkok, 10400, Thailand
- Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Road, Ratchathewi, Bangkok, 10400, Thailand
| | - Podjanee Jittamala
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Road, Ratchathewi, Bangkok, 10400, Thailand
- Department of Tropical Hygiene, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Road, Ratchathewi, Bangkok, 10400, Thailand
| | - Renia Gemmell
- Hypha Discovery Limited, 154B Brook Drive, Abingdon, OX14 4SD, Oxfordshire, UK
| | - John Boyle
- Hypha Discovery Limited, 154B Brook Drive, Abingdon, OX14 4SD, Oxfordshire, UK
| | - Stephen Wrigley
- Hypha Discovery Limited, 154B Brook Drive, Abingdon, OX14 4SD, Oxfordshire, UK
| | - Jonathan Steele
- Hypha Discovery Limited, 154B Brook Drive, Abingdon, OX14 4SD, Oxfordshire, UK
| | - Nicholas J White
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Road, Ratchathewi, Bangkok, 10400, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Old Road Campus, Oxford, OX3 7BN, UK
| | - Joel Tarning
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Road, Ratchathewi, Bangkok, 10400, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Old Road Campus, Oxford, OX3 7BN, UK
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7
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Yan C, Hii J, Ngoen-Klan R, Ahebwa A, Saeung M, Chareonviriyaphap T. The effect of transfluthrin-treated jute and cotton emanator vests on human landing and fecundity of Anopheles minimus in Thailand. Acta Trop 2023; 242:106904. [PMID: 36967063 DOI: 10.1016/j.actatropica.2023.106904] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2022] [Revised: 03/17/2023] [Accepted: 03/18/2023] [Indexed: 04/03/2023]
Abstract
Complementary approaches to tackle outdoor and early evening biting mosquitoes are urgently required. Transfluthrin (TFT) is a volatile pyrethroid capable of altering mosquito feeding behavior. This study investigated the efficacy of TFT-treated jute (TFT-J) and cotton (TFT-C) fabrics on human landing activity, feeding and fecundity of Anopheles minimus in Thailand. Jute and cotton fabrics each measuring 1024 cm2 were impregnated with 7.34 × 10-4 g/cm2 TFT (20%, w/v), and evaluated in a semi-field screen house system. Two collectors, wearing an untreated control or TFT-treated vests, conducted human-landing collections of released 100 laboratory-reared adult females of An. minimus from 18:00-00:00 h for 16 consecutive nights. Recaptured mosquitoes were given a blood meal for 30 min. with a membrane feeding system for assessment of blood feeding and fecundity. TFT-J, relative to control, significantly reduced human landings (Odds Ratio (OR) =0.27 (95% Confidence Interval (CI) [0.10-0.74], p = 0.011)), however no significant reduction was observed for TFT-C (OR=0.67 [95% CI 0.24-1.82], p = 0.43). Blood feeding was significantly lower among mosquitoes exposed to TFT-J (12.45% [95% CI, 2.04-22.85], p = 0.029) and TFT-C (13% [95% CI, 0.99-26.84], p = 0.016) relative to control. Impregnated fabrics had no effect on the mean number of egg oviposition. However, egg hatchability was reduced in TFT-J (49.5% [95% CI, 21.74-77.26], p = 0.029) and TFT-C (40.2% [95% CI, 17.21-63.19], p = 0.008) relative to control. TFT-J significantly reduced the landing, blood feeding, and fertility of An. minimus. Further studies are needed to evaluate different treatment methods on fabrics and their incorporation in integrated mosquito management.
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Affiliation(s)
- Chanly Yan
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok 10900, Thailand
| | - Jeffrey Hii
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok 10900, Thailand; College of Public Health, Medical & Veterinary Sciences, James Cook University, North Queensland, QLD 4810, Australia
| | - Ratchadawan Ngoen-Klan
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok 10900, Thailand
| | - Alex Ahebwa
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok 10900, Thailand
| | - Manop Saeung
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok 10900, Thailand
| | - Theeraphap Chareonviriyaphap
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok 10900, Thailand; Royal Society of Thailand, Thailand.
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8
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Population genomics reveal distinct and diverging populations of An. minimus in Cambodia. Commun Biol 2022; 5:1308. [PMID: 36443434 PMCID: PMC9705317 DOI: 10.1038/s42003-022-04259-y] [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: 12/21/2021] [Accepted: 11/15/2022] [Indexed: 11/29/2022] Open
Abstract
Anopheles minimus is an important malaria vector throughout its wide geographic range across Southeast Asia. Genome sequencing could provide important insights into the unique malaria transmission dynamics in this region, where many vector species feed and rest outdoors. We describe results from a study using Illumina deep whole-genome sequencing of 302 wild-caught An. minimus collected from three Cambodian provinces over several years (2010, 2014, 2016) and seasons to examine the level of population structure and genetic diversity within this species. These specimens cluster into four distinct populations of An. minimus s.s., with two populations overlapping geographically. We describe the underlying genetic diversity and divergence of these populations and investigated the genetic variation in genes known to be involved in insecticide resistance. We found strong signals of selection within these An. minimus populations, most of which were present in the two Northeastern Cambodian populations and differ from those previously described in African malaria vectors. Cambodia is the focus of the emergence and spread of drug-resistant malaria parasites, so understanding the underlying genetic diversity and resilience of the vectors of these parasites is key to implementing effective malaria control and elimination strategies. These data are publicly available as part of the MalariaGEN Vector Observatory, an open access resource of genome sequence data.
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9
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Yan C, Hii J, Ngoen-Klan R, Saeung M, Chareonviriyaphap T. Semi-field evaluation of human landing catches versus human double net trap for estimating human biting rate of Anopheles minimus and Anopheles harrisoni in Thailand. PeerJ 2022; 10:e13865. [PMID: 36101880 PMCID: PMC9464434 DOI: 10.7717/peerj.13865] [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: 05/02/2022] [Accepted: 07/18/2022] [Indexed: 01/24/2023] Open
Abstract
Background Whilst the human landing catch (HLC) technique is considered the 'gold standard' for estimating human-biting rates, it is labor-intensive and fraught with potential risk of exposure to infectious mosquito bites. This study evaluated the feasibility and performance of an alternative method, the human double net trap (HDNT) relative to HLC for monitoring host-seeking malaria vectors of the Anopheles minimus complex in a semi-field system (SFS). Methods HDNT and HLC were positioned in two rooms, 30 m apart at both ends of the SFS. Two human volunteers were rotated between both traps and collected released mosquitoes (n = 100) from 6:00 pm till 6:00 am. Differences in Anopheles mosquito densities among the trapping methods were compared using a generalized linear model based on a negative binomial distribution. Results There were 82.80% (2,136/2,580) of recaptures of wild-caught and 94.50% (2,835/3,000) of laboratory-reared mosquitoes that were molecularly identified as An. harrisoni and An. minimus, respectively. Mean density of An. harrisoni was significantly lower in HNDT (15.50 per night, 95% CI [12.48-18.52]) relative to HLC (25.32 per night (95% CI [22.28-28.36]), p < 0.001). Similarly, the mean density of a laboratory strain of An. minimus recaptured in HDNT was significantly lower (37.87 per night, 95% CI [34.62-41.11]) relative to HLC (56.40 per night, 95% CI [55.37-57.43]), p < 0.001. Relative sampling efficiency analysis showed that HLC was the more efficient trap in collecting the An. minimus complex in the SFS. Conclusion HDNT caught proportionately fewer An. minimus complex than HLC. HDNT was not sensitive nor significantly correlated with HLC, suggesting that it is not an alternative method to HLC.
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Affiliation(s)
- Chanly Yan
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand
| | - Jeffrey Hii
- College of Public Health, Medical and Veterinary Sciences, James Cook University of North Queensland, North Queensland, Australia
| | - Ratchadawan Ngoen-Klan
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand
| | - Manop Saeung
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand
| | - Theeraphap Chareonviriyaphap
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand,Royal Society of Thailand, Bangkok, Thailand
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10
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Dakorah MP, Aninagyei E, Attoh J, Adedia D, Tettey CO, Kyei-Barffour I, Acheampong DO. Ecological and seasonal variations and other factors associated with clinical malaria in the Central Region of Ghana: A cross-sectional study. J Infect Public Health 2022; 15:631-637. [PMID: 35580448 DOI: 10.1016/j.jiph.2022.04.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Revised: 04/11/2022] [Accepted: 04/28/2022] [Indexed: 10/18/2022] Open
Abstract
BACKGROUND This study investigated malaria transmission under various contrasting settings in the Central Region, a malaria endemic region in Ghana. METHODS This cross-sectional study was carried out in five randomly selected districts in the Central Region of Ghana. Three of the districts were forested, while the rest was coastal. Study participants were selected to coincide with either the regular rainy or dry season. From each study site, hospital attendees were randomly selected with prior consent. Consciously, study participants were selected in both rainy (September and October, 2020) and dry (November and December, 2020) seasons. Clinical data for each patient was checked for clinical malaria suspicion and microscopic confirmation of malaria. Using SPSS Version 24 (Chicago, IL, USA), bivariate analysis was done to determine the association of independent variables (ecological and seasonal variations) with malaria status. When the overall analysis did not yield significant association, further statistical analysis was performed after stratification of variables (into age and gender) to determine whether any or both of them would significantly associate with the dependent variable. RESULTS Of the 3993 study participants, 62.5% were suspected of malaria whereas 38.2% were confirmed to have clinical falciparum malaria. Data analysis revealed that in both rainy and dry seasons, malaria cases were significantly higher in forested districts ) than coastal districts (x2 = 217.9 vs x2 = 50.9; p < 0.001). Taken together, the risk of malaria was significantly higher in the dry season (COR = 1.471, p < 0.001) and lower in coastal zones (COR = 0.826, p = 0.007). There was significant reduced risk of participants aged over 39 years of malaria (COR=0.657, p < 0.001). Whereas, in general patients between 10 and 19 years were insignificantly less likely to have malaria (COR = 0.911, p = 0.518) compared to participants aged less than< 10 years, the reverse was observed in coastal districts where patients less than 10 years of age in coastal districts were less likely to have malaria (COR=2.440, p = 0.003). In general, gender did not associate with malaria, but when stratified by study district, the risk of female gender to malaria was significantly higher in Agona Swedru (COR = 5.605, p < 0.001), Assin central (COR = 2.172, p < 0.001), Awutu Senya (COR = 2.410, p < 0.001) and Cape Coast (COR = 3.939, p < 0.001) compared to Abura-Asebu-Kwamankese. CONCLUSION This study demonstrated that the predictors of malaria differ from one endemic area to another. Therefore, malaria control interventions such as distribution of long-lasting insecticide treated bed nets, residual spraying with insecticide and mass distribution of antimalaria prophylaxis must be intensified in forested districts in all seasons with particular attention on females.
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Affiliation(s)
- Mavis Puopelle Dakorah
- Department of Biomedical Sciences, School of Allied Health Sciences, University of Cape Coast, Cape Coast, Ghana
| | - Enoch Aninagyei
- Department of Biomedical Sciences, School of Basic and Biomedical Sciences, University of Health and Allied Sciences, Ho, Volta Region, Ghana.
| | - Juliana Attoh
- Department of Biomedical Sciences, School of Allied Health Sciences, University of Cape Coast, Cape Coast, Ghana
| | - David Adedia
- Department of Basic Sciences, School of Basic and Biomedical Sciences, University of Health and Allied Sciences, Ho, Volta Region, Ghana
| | - Clement Okraku Tettey
- Department of Biomedical Sciences, School of Allied Health Sciences, University of Cape Coast, Cape Coast, Ghana
| | - Isaac Kyei-Barffour
- Department of Biomedical Sciences, School of Allied Health Sciences, University of Cape Coast, Cape Coast, Ghana
| | - Desmond Omane Acheampong
- Department of Biomedical Sciences, School of Allied Health Sciences, University of Cape Coast, Cape Coast, Ghana.
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11
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Shah JA. Learnings from Thailand in building strong surveillance for malaria elimination. Nat Commun 2022; 13:2677. [PMID: 35562343 PMCID: PMC9106678 DOI: 10.1038/s41467-022-30267-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Accepted: 04/20/2022] [Indexed: 12/02/2022] Open
Affiliation(s)
- Jui A Shah
- RTI International, Unit 406, 208 Wireless Road, Lumpini, Pathumwan, Bangkok, 10330, Thailand.
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12
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Zhong D, Aung PL, Mya MM, Wang X, Qin Q, Soe MT, Zhou G, Kyaw MP, Sattabongkot J, Cui L, Yan G. Community structure and insecticide resistance of malaria vectors in northern-central Myanmar. Parasit Vectors 2022; 15:155. [PMID: 35505366 PMCID: PMC9062858 DOI: 10.1186/s13071-022-05262-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Accepted: 03/29/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Myanmar is one of the six countries in the Greater Mekong Subregion (GMS) of Southeast Asia. Malaria vectors comprise many Anopheles species, which vary in abundance and importance in malaria transmission among different geographical locations in the GMS. Information about the species composition, abundance, and insecticide resistance status of vectorial systems in Myanmar is scarce, hindering our efforts to effectively control malaria vectors in this region. METHODS During October and November 2019, larvae and adult females of Anopheles mosquitoes were collected in three sentinel villages of Banmauk township in northern Myanmar. Adult female mosquitoes collected by cow-baited tent collection (CBTC) and adults reared from field-collected larvae (RFCL) were used to determine mortality rates and knockdown resistance (kdr) against deltamethrin using the standard WHO susceptibility test. Molecular species identification was performed by multiplex PCR and ITS2 PCR, followed by DNA sequencing. The kdr mutation at position 1014 of the voltage-gated sodium channel gene was genotyped by DNA sequencing for all Anopheles species tested. RESULTS A total of 1596 Anopheles mosquitoes from seven morphologically identified species groups were bioassayed. Confirmed resistance to deltamethrin was detected in the populations of An. barbirostris (s.l.), An. hyrcanus (s.l.), and An. vagus, while possible resistance was detected in An. annularis (s.l.), An. minimus, and An. tessellatus. Anopheles kochi was found susceptible to deltamethrin. Compared to adults collected by CBTC, female adults from RFCL had significantly lower mortality rates in the four species complexes. A total of 1638 individuals from 22 Anopheles species were molecularly identified, with the four most common species being An. dissidens (20.5%) of the Barbirostris group, An. peditaeniatus (19.4%) of the Hyrcanus group, An. aconitus (13.4%) of the Funestus group, and An. nivipes (11.5%) of the Annularis group. The kdr mutation L1014F was only detected in the homozygous state in two An. subpictus (s.l.) specimens and in a heterozygous state in one An. culicifacies (s.l.) specimen. CONCLUSIONS This study provides updated information about malaria vector species composition and insecticide resistance status in northern Myanmar. The confirmed deltamethrin resistance in multiple species groups constitutes a significant threat to malaria vector control. The lack or low frequency of target-site resistance mutations suggests that other mechanisms are involved in resistance. Continual monitoring of the insecticide resistance of malaria vectors is required for effective vector control and insecticide resistance management.
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Affiliation(s)
- Daibin Zhong
- Program in Public Health, College of Health Sciences, University of California at Irvine, Irvine, CA 92697 USA
| | | | | | - Xiaoming Wang
- Program in Public Health, College of Health Sciences, University of California at Irvine, Irvine, CA 92697 USA
| | - Qian Qin
- Medical College, Lishui University, Zhejiang, China
| | - Myat Thu Soe
- Myanmar Health Network Organization, Yangon, Myanmar
| | - Guofa Zhou
- Program in Public Health, College of Health Sciences, University of California at Irvine, Irvine, CA 92697 USA
| | | | - Jetsumon Sattabongkot
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Liwang Cui
- Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL 33612 USA
| | - Guiyun Yan
- Program in Public Health, College of Health Sciences, University of California at Irvine, Irvine, CA 92697 USA
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13
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Nguyen TT, Nguyen XX, Wilson-Barthes M, Sawada I, Muela J, Hausmann-Muela S, Pham TV, Van Nguyen H, Van Nguyen V, Tran DT, Gryseels C, D'Alessandro U, Grietens KP, Erhart A. Why using bed nets is a challenge among minority populations in Central Vietnam. Malar J 2022; 21:87. [PMID: 35292018 PMCID: PMC8922825 DOI: 10.1186/s12936-022-04114-9] [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: 08/10/2021] [Accepted: 03/02/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Despite freely distributed insecticide-treated nets (ITNs) and health information campaigns to increase their use among populations at risk, malaria transmission persists in forested areas in Vietnam, especially among ethnic minority communities. A mixed-methods study was conducted in four villages of Ca Dong and M'nong ethnicity in Central Vietnam between 2009 and 2011 to assess factors limiting the uptake of ITNs. METHODS The mixed-methods research design consisted of a qualitative study to explore the context and barriers to ITN use, and a cross-sectional household survey (n = 141) to quantify factors for limited and appropriate net use. RESULTS The Ca Dong and M'nong's livelihood was dependent on swidden farming in the forest. Poverty-related factors, including the lack of beds, blankets, the practice of sleeping around the kitchen fire and deteriorated ITNs due to open housing structures, were reasons for alternative and non-use of ITNs. When household members stayed overnight in plot huts at fields, ITNs were even more unavailable and easily deteriorated. 72.5% of households reported having received one net for every two persons, and 82.2% of participants reported to have used ITNs the night before the survey. However, only 18.4% of participants were estimated to be effectively protected by ITNs after accounting for the availability of torn ITNs and the way ITNs were used, for example as blankets, at both village and fields. Multi-variable logistic regression showed the effect of four significant factors for appropriate ITN use: i) being female (AOR = 8.08; p = 0.009); ii) aware of mosquito bites as the sole cause of malaria (AOR = 7.43; p = 0.008); iii) not sleeping around the kitchen fire (AOR = 24.57; p = 0.001); and iv) having sufficient number of ITNs in the household (AOR = 21.69; p = 0.001). CONCLUSION This study showed how social factors rooted in poverty and swidden agriculture limited the effective use of ITNs, despite high coverage, among ethnic minority populations in Central Vietnam. An in-depth understanding of the local context is essential to develop specific indicators for measuring ITN use.
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Affiliation(s)
- Thuan Thi Nguyen
- Socio-Ecological Health Research Unit, Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium. .,National Institute of Malariology, Parasitology and Entomology, Hanoi, Vietnam.
| | - Xa Xuan Nguyen
- National Institute of Malariology, Parasitology and Entomology, Hanoi, Vietnam
| | - Marta Wilson-Barthes
- International Health Institute, Brown University School of Public Health, Providence, USA
| | - Ikumi Sawada
- Department of Clinical Tropical Medicine, Institute of Tropical Medicine, Graduate School of Biomedical Science, Nagasaki University, Nagasaki, Japan
| | - Joan Muela
- University Ramon I Virgili, Tarragona, Spain.,Partners for Applied Social Sciences, PASS International, Tessenderlo, Belgium
| | | | - Thanh Vinh Pham
- National Institute of Malariology, Parasitology and Entomology, Hanoi, Vietnam
| | - Hong Van Nguyen
- National Institute of Malariology, Parasitology and Entomology, Hanoi, Vietnam
| | | | - Duong Thanh Tran
- National Institute of Malariology, Parasitology and Entomology, Hanoi, Vietnam
| | - Charlotte Gryseels
- Socio-Ecological Health Research Unit, Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium
| | - Umberto D'Alessandro
- Medical Research Council Unit The Gambia at the London School of Hygiene and Tropical Medicine, Fajara, The Gambia
| | - Koen Peeters Grietens
- Socio-Ecological Health Research Unit, Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium.,Partners for Applied Social Sciences, PASS International, Tessenderlo, Belgium.,School of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, Japan
| | - Annette Erhart
- Medical Research Council Unit The Gambia at the London School of Hygiene and Tropical Medicine, Fajara, The Gambia
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14
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Nguyen TT, Gryseels C, Tran DT, Smekens T, Gerrets R, Nguyen XX, Peeters Grietens K. Understanding Malaria Persistence: A Mixed-Methods Study on the Effectiveness of Malaria Elimination Strategies in South-Central Vietnam. Front Public Health 2021; 9:742378. [PMID: 34950624 PMCID: PMC8688690 DOI: 10.3389/fpubh.2021.742378] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 11/02/2021] [Indexed: 11/17/2022] Open
Abstract
Despite the scale-up of vector control, diagnosis and treatment, and health information campaigns, malaria persists in the forested areas of South-Central Vietnam, home to ethnic minority populations. A mixed-methods study using an exploratory sequential design was conducted in 10 Ra-glai villages in Bac Ai district of Ninh Thuan province to examine which social factors limited the effectiveness of the national malaria elimination strategy in the local setting. Territorial arrangements and mobility were found to directly limit the effectiveness of indoor residual spraying and long-lasting insectidical treated nets (LLINs). Households (n=410) were resettled in the “new villages” by the government, where they received brick houses (87.1%) and sufficient LLINs (97.3%). However, 97.6% of households went back to their “old villages” to continue slash-and-burn agriculture. In the old village, 48.5% of households lived in open-structured plot huts and only 5.7% of them had sufficient LLIN coverage. Household representatives believed malaria could be cured with antimalarials (57.8%), but also perceived non-malarial medicines, rituals, and vitamin supplements to be effective against malaria. Household members (n = 1,957) used public health services for their most recent illness (62.9%), but also reported to buy low-cost medicines from the private sector to treat fevers and discomfort as these were perceived to be the most cost-effective treatment option for slash-and-burn farmers. The study shows the relevance of understanding social factors to improve the uptake of public health interventions and calls for contextually adapted strategies for malaria elimination in ethnic minority populations in Vietnam and similar settings.
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Affiliation(s)
- Thuan Thi Nguyen
- Department of Malaria Epidemiology, National Institute of Malariology, Parasitology and Entomology (NIMPE), Hanoi, Vietnam.,Unit of Socio-Ecological Health Research, Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium.,Faculty of Social and Behavioural Sciences, Amsterdam Institute for Social Science Research (AISSR), University of Amsterdam, Amsterdam, Netherlands
| | - Charlotte Gryseels
- Unit of Socio-Ecological Health Research, Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium
| | - Duong Thanh Tran
- Department of Malaria Epidemiology, National Institute of Malariology, Parasitology and Entomology (NIMPE), Hanoi, Vietnam
| | - Tom Smekens
- Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium
| | - René Gerrets
- Faculty of Social and Behavioural Sciences, Amsterdam Institute for Social Science Research (AISSR), University of Amsterdam, Amsterdam, Netherlands.,Amsterdam Institute for Global Health and Development (AIGHD), Amsterdam, Netherlands
| | - Xa Xuan Nguyen
- Department of Malaria Epidemiology, National Institute of Malariology, Parasitology and Entomology (NIMPE), Hanoi, Vietnam
| | - Koen Peeters Grietens
- Unit of Socio-Ecological Health Research, Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium.,School of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, Japan
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15
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Kearney EA, Agius PA, Chaumeau V, Cutts JC, Simpson JA, Fowkes FJI. Anopheles salivary antigens as serological biomarkers of vector exposure and malaria transmission: A systematic review with multilevel modelling. eLife 2021; 10:e73080. [PMID: 34939933 PMCID: PMC8860437 DOI: 10.7554/elife.73080] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Accepted: 12/21/2021] [Indexed: 12/25/2022] Open
Abstract
Background Entomological surveillance for malaria is inherently resource-intensive and produces crude population-level measures of vector exposure which are insensitive in low-transmission settings. Antibodies against Anopheles salivary proteins measured at the individual level may serve as proxy biomarkers for vector exposure and malaria transmission, but their relationship is yet to be quantified. Methods A systematic review of studies measuring antibodies against Anopheles salivary antigens (PROSPERO: CRD42020185449). Multilevel modelling (to account for multiple study-specific observations [level 1], nested within study [level 2], and study nested within country [level 3]) estimated associations between seroprevalence with Anopheles human biting rate (HBR) and malaria transmission measures. Results From 3981 studies identified in literature searches, 42 studies across 16 countries were included contributing 393 study-specific observations of anti-Anopheles salivary antibodies determined in 42,764 samples. A positive association between HBR (log transformed) and seroprevalence was found; overall a twofold (100% relative) increase in HBR was associated with a 23% increase in odds of seropositivity (OR: 1.23, 95% CI: 1.10-1.37; p<0.001). The association between HBR and Anopheles salivary antibodies was strongest with concordant, rather than discordant, Anopheles species. Seroprevalence was also significantly positively associated with established epidemiological measures of malaria transmission: entomological inoculation rate, Plasmodium spp. prevalence, and malarial endemicity class. Conclusions Anopheles salivary antibody biomarkers can serve as a proxy measure for HBR and malaria transmission, and could monitor malaria receptivity of a population to sustain malaria transmission. Validation of Anopheles species-specific biomarkers is important given the global heterogeneity in the distribution of Anopheles species. Salivary biomarkers have the potential to transform surveillance by replacing impractical, inaccurate entomological investigations, especially in areas progressing towards malaria elimination. Funding Australian National Health and Medical Research Council, Wellcome Trust.
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Affiliation(s)
- Ellen A Kearney
- The McFarlane Burnet Institute of Medical Research and Public HealthMelbourneAustralia
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of MelbourneMelbourneAustralia
| | - Paul A Agius
- The McFarlane Burnet Institute of Medical Research and Public HealthMelbourneAustralia
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of MelbourneMelbourneAustralia
- Department of Epidemiology and Preventive Medicine, Monash UniversityMelbourneAustralia
| | - Victor Chaumeau
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol UniversityMae SotThailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of OxfordOxfordUnited Kingdom
| | - Julia C Cutts
- The McFarlane Burnet Institute of Medical Research and Public HealthMelbourneAustralia
- Department of Medicine at the Doherty Institute, The University of MelbourneMelbourneAustralia
| | - Julie A Simpson
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of MelbourneMelbourneAustralia
| | - Freya JI Fowkes
- The McFarlane Burnet Institute of Medical Research and Public HealthMelbourneAustralia
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of MelbourneMelbourneAustralia
- Department of Epidemiology and Preventive Medicine, Monash UniversityMelbourneAustralia
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16
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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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17
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Nguyen TQ, Nguyen MD, Pham VX, Ro HM, Edstein MD, Chow WK, Martin NJ, Hertz JC, Motoki MT. Entomological survey in two communes with residual malaria transmission in Gia Lai Province in the central highlands of Vietnam. Malar J 2021; 20:403. [PMID: 34656112 PMCID: PMC8520203 DOI: 10.1186/s12936-021-03941-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 10/04/2021] [Indexed: 12/02/2022] Open
Abstract
Background In 2018, the National Malaria Control Programme in Vietnam switched from prioritizing malaria control to elimination. However, with the ongoing elimination programme, there are still areas where residual malaria transmission persists, including the central highlands. This entomological survey was conducted to evaluate Anopheles diversity and host-seeking activity of Anopheles vectors in two communes with very low malaria transmission in Gia Lai Province. Methods Anopheles species were collected in Ia DReh commune and Ia KDam commune, Gia Lai Province in the central highlands of Vietnam. Collections were conducted using human-baited double net trap, light trap and manual aspiration collections around cattle sheds, in the dry and rainy season. Mosquito specimens were identified morphologically, and members of species complexes were distinguished molecularly. Mosquito night-feeding patterns were investigated during the dry and rainy seasons. Results Overall, 18,835 specimens including 19 taxa were collected in Ia KDam and Ia DReh communes. These included the primary malaria vectors, Anopheles dirus and Anopheles minimus, and other secondary vector species. Anopheles dirus was observed to be an anthropophilic species, whereas An. minimus and a number of secondary vectors were observed to be zoophilic. Anopheles vagus was the dominant species, followed by Anopheles sinensis and Anopheles peditaeniatus. The majority of specimens were collected in the rainy season due to the relatively large number of An. vagus, while An. peditaeniatus, An. dirus, Anopheles kochi, Anopheles monstrosus and Anopheles tessellatus were collected in greater numbers during the dry season. The peak of host-seeking activity for An. dirus, An. sinensis, and An. vagus was between 18.00 and 19.00 h. Conclusion This study provided information on the diversity, seasonal prevalence and behaviour of Anopheles at the study sites. Identifying the diverse mosquito fauna in the central highlands of Vietnam allows species-specific control measures to be implemented by the National Programme to reduce malaria in areas of very low malaria transmission. The peak Anopheles host-seeking activity observed in this study was between 18.00 and 23.00 h, which highlights the need to better characterize Anopheles behaviour in this region of Vietnam to inform on vector control strategies. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-021-03941-6.
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Affiliation(s)
- Thai Quang Nguyen
- Vietnam People's Army Military, Institute of Preventive Medicine, Hanoi, Vietnam
| | - Manh Duc Nguyen
- Vietnam People's Army Military, Institute of Preventive Medicine, Hanoi, Vietnam
| | - Vinh Xuan Pham
- Vietnam People's Army Military, Institute of Preventive Medicine, Hanoi, Vietnam
| | - Huan Mah Ro
- Gia Lai Center for Disease Control (CDC), Pleiku, Gia Lai, Vietnam
| | - Michael D Edstein
- Australian Defence Force Malaria and Infectious Disease Institute, Brisbane, Australia
| | - Weng K Chow
- Australian Defence Force Malaria and Infectious Disease Institute, Brisbane, Australia
| | | | - Jeffrey C Hertz
- US Naval Medical Research Unit-Two (NAMRU-2), Singapore, Singapore
| | - 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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18
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Abstract
J. Kevin Baird and colleagues, examine and discuss the estimated global burden of vivax malaria and it's biological, clinical, and public health complexity.
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Affiliation(s)
- Katherine E. Battle
- Institute for Disease Modeling, Seattle, Washington, United States of America
| | - J. Kevin Baird
- Eijkman-Oxford Clinical Research Unit, Eijkman Institute of Molecular Biology, Jakarta, Indonesia
- Nuffield Department of Medicine, Centre for Tropical Medicine, University of Oxford, Oxford, United Kingdom
- * E-mail:
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19
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Masunaga Y, Muela Ribera J, Nguyen TT, Tesfazghi K, Peeters Grietens K. In search of the last malaria cases: ethnographic methods for community and private-sector engagement in malaria elimination in Vietnam, Laos, and Cambodia. Malar J 2021; 20:370. [PMID: 34535133 PMCID: PMC8447739 DOI: 10.1186/s12936-021-03903-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2021] [Accepted: 09/02/2021] [Indexed: 08/21/2023] Open
Abstract
Background Despite significant strides made in reducing malaria morbidity and mortality in the Greater Mekong Subregion, malaria transmission continues amongst the most ‘hard-to-reach’, such as forest-goers and mobile and migrant populations, who face access obstacles to malaria diagnosis and treatment. As such, regional malaria elimination strategies endeavour to incorporate the private sector and local communities in improving surveillance and detection of the last malaria cases in remote forested areas. The question remains, however, whether such strategies can reach these hard-to-reach populations and effectively reduce their disproportionate burden of malaria. This paper evaluates the strategy of community and private sector engagement in a malaria elimination project in Vietnam, Laos, and Cambodia. Methods Ethnographic research, incorporating in-depth interviews, participant observations with informal discussions, and group discussions were conducted in Bu Gia Map commune, Binh Phuc province of Vietnam; in Phouvong district, Attapeu province of Laos; and, in nine newly established and informal communities in the provinces of Mondul Kiri, Steung Treng, Kratie, Kampong Thom, and Prah Vihear of Cambodia. Results Different types of factors limited or enhanced the effectiveness of the participatory approaches in the different settings. In Vietnam, inter-ethnic tensions and sensitivity around forest-work negatively affected local population’s health-seeking behaviour and consequent uptake of malaria testing and treatment. In Laos, the location of the project collaborative pharmacies in the district-centre were a mismatch for reaching hard-to-reach populations in remote villages. In Cambodia, the strategy of recruiting community malaria-workers, elected by the community members, did manage to reach the remote forested areas where people visited or stayed. Conclusions ‘Hard-to-reach’ populations remain hard to reach without proper research identifying the socio-economic-political environment and the key dynamics determining uptake in involved communities and populations. Solid implementation research with a strong ethnographic component is required to tailor malaria elimination strategies to local contexts.
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Affiliation(s)
- Yoriko Masunaga
- Socio-Ecological Health Research Unit, Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium. .,Faculty of Social and Behavioural Science, Department of Sociology and Anthropology, University of Amsterdam, Amsterdam, The Netherlands.
| | - Joan Muela Ribera
- PASS Suisse, Neuchâtel, Switzerland.,Universitat Rovira i Virgili, Tarragona, Spain
| | - Thuan Thi Nguyen
- Socio-Ecological Health Research Unit, Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium.,Faculty of Social and Behavioural Science, Department of Sociology and Anthropology, University of Amsterdam, Amsterdam, The Netherlands.,National Institute of Malariology, Parasitology and Entomology, Hanoi, Vietnam
| | | | - Koen Peeters Grietens
- Socio-Ecological Health Research Unit, Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium.,School of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, Japan
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20
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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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21
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Canavati SE, Kelly GC, Vo TH, Tran LK, Ngo TD, Tran DT, Edgel KA, Martin NJ. Mosquito Net Ownership, Utilization, and Preferences among Mobile and Migrant Populations Sleeping in Forests and Farms in Central Vietnam: A Cross-Sectional Study. Am J Trop Med Hyg 2021; 104:1917-1924. [PMID: 33819169 PMCID: PMC8103484 DOI: 10.4269/ajtmh.20-0711] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2020] [Accepted: 02/05/2021] [Indexed: 11/07/2022] Open
Abstract
Strengthening vector control measures among mobile and migrant populations (MMPs) is crucial to malaria elimination, particularly in areas with multidrug-resistant malaria. Although a global priority, providing access and ensuring high coverage of available tools such as long-lasting insecticidal nets (LLINs) among these vulnerable groups remains a significant challenge. We assessed mosquito net ownership, utilization, and preference among individuals who slept in a forest and/or on a farm against those residing only in village "home" settings in a priority malaria elimination area of Vietnam. Proportions of respondents owning bed nets were similar among forest, farm, and home sleeping sites, ranging between 96% and 98%. The proportion of respondents owning hammock nets was higher for the forest group (92%), whereas ownership of hammocks in general was significantly lower for the home group (55%). Most respondents (97%) preferred to bring hammock nets to their remote sleeping site, whereas a smaller proportion (25%) also considered bed nets as an option. Respondent preferences included thick hammock nets with zippers (53%), hammocks with a flip cover (17%), and thin hammock nets with zippers (15%), with none choosing polyethylene (hard) LLINs. Although there is high coverage and access to nets for this high-priority MMP group, there was a noted gap between coverage and net use, potentially undermining the effectiveness of net-related interventions that could impact malaria prevention and elimination efforts in Vietnam. The design and material of nets are important factors for user preferences that appear to drive net use.
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Affiliation(s)
| | - Gerard C. Kelly
- Vysnova Partners, Inc., Landover, Maryland;,Address correspondence to Gerard C. Kelly, Vysnova Partners, Inc., 8400 Corporate Dr., Suite 130, Landover, MD 20875. E-mail:
| | | | | | - Thang Duc Ngo
- National Institute of Malariology, Parasitology and Entomology, Hanoi, Vietnam
| | - Duong Thanh Tran
- National Institute of Malariology, Parasitology and Entomology, Hanoi, Vietnam
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22
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Management of insecticides for use in disease vector control: Lessons from six countries in Asia and the Middle East. PLoS Negl Trop Dis 2021; 15:e0009358. [PMID: 33930033 PMCID: PMC8115796 DOI: 10.1371/journal.pntd.0009358] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2020] [Revised: 05/12/2021] [Accepted: 03/31/2021] [Indexed: 01/22/2023] Open
Abstract
Interventions to control the vectors of human diseases, notably malaria, leishmaniasis and dengue, have relied mainly on the action of chemical insecticides. However, concerns have been raised regarding the management of insecticides in vector-borne disease-endemic countries. Our study aimed to analyze how vector control insecticides are managed in selected countries to extract lessons learned. A qualitative analysis of the situation of vector control insecticides management was conducted in six countries. Multi-stakeholder meetings and key informer interviews were conducted on aspects covering the pesticide lifecycle. Findings were compared and synthesized to extract lessons learned. Centrally executed guidelines and standards on the management of insecticides offered direction and control in most malaria programs, but were largely lacking from decentralized dengue programs, where practices of procurement, application, safety, storage, and disposal were variable between districts. Decentralized programs were better at facilitating participation of stakeholders and local communities and securing financing from local budgets. However, little coordination existed between malaria, visceral leishmaniasis and dengue programs within countries. Entomological capacity was concentrated in malaria programs at central level, while dengue and visceral leishmaniasis programs were missing out on expertise. Monitoring systems for insecticide resistance in malaria vectors were rarely used for dengue or visceral leishmaniasis vectors. Strategies for insecticide resistance management, where present, did not extend across programs or sectors in most countries. Dengue programs in most countries continued to rely on space spraying which, considering the realities on the ground, call for revision of international guidelines. Vector control programs in the selected countries were confronted with critical shortcomings in the procurement, application, safety measures, storage, and disposal of vector control insecticides, with implications for the efficiency, effectiveness, and safety of vector control. Further international support is needed to assist countries in situation analysis, action planning and development of national guidelines on vector control insecticide management. Vector-borne diseases such as dengue, malaria and leishmaniasis are transmitted by insect vectors. Transmission can be interrupted through vector control. Chemical insecticides are the mainstay for controlling these insect vectors. However, the use of chemicals also introduces risks to health and the environment and may lead to insecticide resistance. Hence, proper management of those insecticides is critical. To find out how the insecticides used for vector control are being managed, the authors conducted investigations in six countries in Asia and the Middle East. They found that the practices of insecticide procurement, application, storage, and disposal depended on how a program is organized. Dengue programs were operated in a decentralized manner and, consequently, lacked coordination through guidelines and standards on best practices. Also, coordination between malaria, visceral leishmaniasis and dengue programs within countries was minimal, and expertise needed to guide decisions on vector control and to monitor insecticide resistance was in short supply. The identified shortcomings in how vector control insecticides are managed likely affected the efficiency, effectiveness, and safety of vector control operations.
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23
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Hii J, Hustedt J, Bangs MJ. Residual Malaria Transmission in Select Countries of Asia-Pacific Region: Old Wine in a New Barrel. J Infect Dis 2021; 223:S111-S142. [PMID: 33906222 PMCID: PMC8079134 DOI: 10.1093/infdis/jiab004] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Background Despite substantial reductions in malaria burden and improvement in case management, malaria remains a major public health challenge in the Asia-Pacific region. Residual malaria transmission (RMT) is the fraction of total transmission that persists after achievement of full operational coverage with effective insecticide-treated bed nets (ITNs)/long-lasting insecticidal nets (LLINs) and/or indoor residual spray interventions. There is a critical need to standardize and share best practices for entomological, anthropological, and product development investigative protocols to meet the challenges of RMT and elimination goals. Methods A systematic review was conducted to describe when and where RMT is occurring, while specifically targeting ownership and usage of ITN/LLINs, indoor residual spray application, insecticide susceptibility of vectors, and human and vector biting behavior, with a focus on nighttime activities. Results Sixty-six publications from 1995 to present met the inclusion criteria for closer review. Associations between local vector control coverage and use with behaviors of human and mosquito vectors varied by locality and circumstance. Consequently, the magnitude of RMT is insufficiently studied and analyzed with sparse estimates of individual exposure in communities, insufficient or incomplete observations of ITN/LLIN use, and the local human population movement into and from high-risk areas. Conclusions This review identified significant gaps or deficiencies that require urgent attention, namely, developing standardized procedures and methods to estimate risk exposure beyond the peridomestic setting, analytical approaches to measure key human-vector interactions, and seasonal location-specific agricultural or forest use calendars, and establishing the collection of longitudinal human and vector data close in time and location.
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Affiliation(s)
- Jeffrey Hii
- Malaria Consortium Asia, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, Queensland, Australia
| | | | - Michael J Bangs
- Public Health and Malaria Control Department, PT Freeport Indonesia, International SOS, Jl. Kertajasa, Kuala Kencana, Papua, Indonesia.,Department of Entomology, Faculty of Agriculture, Kasertart University, Bangkok, Thailand
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24
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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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25
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Cramer EY, Quang NX, Hertz JC, Van Nguyen D, Quang HH, Mendenhall I, Lover AA. Ivermectin Treatment for Cattle Reduced the Survival of Two Malaria Vectors, Anopheles dirus and Anopheles epiroticus, Under Laboratory Conditions in Central Vietnam. Am J Trop Med Hyg 2021; 104:2165-2168. [PMID: 33901003 PMCID: PMC8176477 DOI: 10.4269/ajtmh.20-1239] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 03/03/2021] [Indexed: 01/30/2023] Open
Abstract
Ivermectin is a low-cost and nontoxic mosquitocide that may have a role in malaria elimination. However, the extent to which this drug impacts the mortality of Anopheles dirus and Anopheles epiroticus, two important malaria vectors in Southeast Asia, is unknown. This study compared and quantified anopheline mortality after feeding on ivermectin-treated cattle and control cattle in Vietnam. Local anopheline colonies fed on cattle 1 to 3, 6 to 8, 13 to 15, 20 to 22, and 28 to 30 days after injection (DAI) with ivermectin (intervention) or saline (control). An. dirus that fed on ivermectin-treated cattle had higher mortality rates than controls for up to 20 DAI (P < 0.05); An. epiroticus that fed on ivermectin-treated cattle had consistently higher mortality rates than controls for up to 8 DAI (P < 0.05). Feeding on ivermectin-treated cattle increased the mortality rate of these vector species for biologically relevant time periods. Therefore, ivermectin has the potential to become an important tool for integrated vector management.
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Affiliation(s)
- Estee Y Cramer
- 1Department of Biostatistics and Epidemiology, School of Public Health and Health Sciences, University of Massachusetts-Amherst, Amherst, Massachusetts
| | - Nguyen Xuan Quang
- 2Institute for Malariology, Parasitology and Entomology, Ministry of Health, Quy Nhon, Vietnam
| | | | - Do Van Nguyen
- 2Institute for Malariology, Parasitology and Entomology, Ministry of Health, Quy Nhon, Vietnam
| | - Huynh Hong Quang
- 2Institute for Malariology, Parasitology and Entomology, Ministry of Health, Quy Nhon, Vietnam
| | - Ian Mendenhall
- 4Programme in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore
| | - Andrew A Lover
- 1Department of Biostatistics and Epidemiology, School of Public Health and Health Sciences, University of Massachusetts-Amherst, Amherst, Massachusetts
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Ngo TD, Canavati SE, Dung DV, Vo TH, Tran DT, Tran LK, Whedbee RJ, Milgotina EI, Kelly GC, Edgel KA, Martin NJ. Results from a malaria indicator survey highlight the importance of routine data capture in high-risk forest and farm transmission sites in Vietnam to tailor location-specific malaria elimination interventions. PLoS One 2021; 16:e0250045. [PMID: 33861798 PMCID: PMC8051764 DOI: 10.1371/journal.pone.0250045] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2021] [Accepted: 03/29/2021] [Indexed: 11/18/2022] Open
Abstract
In-line with the World Health Organization's (WHO) Global Technical Strategy for Malaria (2016-2030), Vietnam is striving to eliminate malaria by 2030. Targeting appropriate interventions in high-risk populations such as forest and forest-fringe communities is a critical component of malaria elimination efforts in Vietnam. In 2016, a household-level malaria indicator survey was conducted in Phu Yen Province, Vietnam with the aim of assessing the knowledge, behaviors and associated risks of malaria infection among priority mobile and migrant populations (MMPs) working and sleeping in forests and on farms. A total of 4211 people were included in the survey, comprised of 1074 heads of households and 3137 associated household members. Of the 1074 head-of-household respondents, 472 slept in a forest, 92 slept on a farm, 132 slept in both forests and farms, and 378 slept at their villages within the last 12 months. Age, literacy, and occupation were significantly different among those who slept in a forest versus on a farm. Of 301 respondents who answered questions about malaria risk factors at sleeping sites, 35% were somewhat aware of malaria prevention practices, but only 4% could recall at least four malaria prevention messages. Among the same group of 301 respondents, only 29% used nets and only 11% used treated nets. Ownership and use of nets among forest-goers was significantly lower than those who slept on a farm or in their village. Huts without walls were significantly prominent forest sleeping site locations (POR = 10.3; 95% CI 4.67-22.7). All respondents who slept in a forest requested standby malaria drugs and one-third of them self-treated without blood testing. Results from this study highlight the importance of capturing relevant location-specific data among priority populations such as remote forest and farm going mobile and migrant populations in Vietnam. Data regarding behavioral practices, knowledge, preventative measures, and intervention coverage at remote-area transmission sites must be routinely captured to effectively monitor progress and refine targeted intervention strategies accordingly.
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Affiliation(s)
- Thang Duc Ngo
- Department of Epidemiology, National Institute of Malariology, Parasitology and Entomology, Hanoi, Vietnam
| | - Sara E. Canavati
- Vysnova Partners, Inc., Landover, Maryland, United States of America
- Burnet Institute, Melbourne, Victoria, Australia
| | - Dang Viet Dung
- Department of Epidemiology, National Institute of Malariology, Parasitology and Entomology, Hanoi, Vietnam
| | - Thuan Huu Vo
- Vysnova Partners, Inc., Landover, Maryland, United States of America
| | - Duong Thanh Tran
- Department of Epidemiology, National Institute of Malariology, Parasitology and Entomology, Hanoi, Vietnam
| | - Long Khanh Tran
- Vysnova Partners, Inc., Landover, Maryland, United States of America
| | - Rosalie J. Whedbee
- Global Scientific Solutions for Health, Baltimore, Maryland, United States of America
| | | | - Gerard C. Kelly
- Vysnova Partners, Inc., Landover, Maryland, United States of America
- * E-mail:
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Li MI, Mailepessov D, Vythilingam I, Lee V, Lam P, Ng LC, Tan CH. Prevalence of simian malaria parasites in macaques of Singapore. PLoS Negl Trop Dis 2021; 15:e0009110. [PMID: 33493205 PMCID: PMC7861519 DOI: 10.1371/journal.pntd.0009110] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2019] [Revised: 02/04/2021] [Accepted: 01/06/2021] [Indexed: 02/04/2023] Open
Abstract
Plasmodium knowlesi is a simian malaria parasite currently recognized as the fifth causative agent of human malaria. Recently, naturally acquired P. cynomolgi infection in humans was also detected in Southeast Asia. The main reservoir of both parasites is the long-tailed and pig-tailed macaques, which are indigenous in this region. Due to increased urbanization and changes in land use, there has been greater proximity and interaction between the long-tailed macaques and the general population in Singapore. As such, this study aims to determine the prevalence of simian malaria parasites in local macaques to assess the risk of zoonosis to the general human population. Screening for the presence of malaria parasites was conducted on blood samples from 660 peridomestic macaques collected between Jan 2008 and Mar 2017, and 379 wild macaques collected between Mar 2009 and Mar 2017, using a Pan-Plasmodium-genus specific PCR. Positive samples were then screened using a simian Plasmodium species-specific nested PCR assay to identify the species of parasites (P. knowlesi, P. coatneyi, P. fieldi, P. cynomolgi, and P. inui) present. All the peridomestic macaques sampled were tested negative for malaria, while 80.5% of the 379 wild macaques were infected. All five simian Plasmodium species were detected; P. cynomolgi being the most prevalent (71.5%), followed by P. knowlesi (47.5%), P. inui (42.0%), P. fieldi (32.5%), and P. coatneyi (28.5%). Co-infection with multiple species of Plasmodium parasites was also observed. The study revealed that Singapore's wild long-tailed macaques are natural hosts of the five simian malaria parasite species, while no malaria was detected in all peridomestic macaques tested. Therefore, the risk of simian malaria transmission to the general human population is concluded to be low. However, this can be better demonstrated with the incrimination of the vectors of simian malaria parasites in Singapore.
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Affiliation(s)
- Meizhi Irene Li
- Environmental Health Institute, National Environment Agency, Singapore
| | - Diyar Mailepessov
- Environmental Health Institute, National Environment Agency, Singapore
| | - Indra Vythilingam
- Parasitology Department, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Vernon Lee
- Saw Swee Hock School of Public Health, National University of Singapore, Singapore
| | - Patrick Lam
- Biodefence Centre, Force Medical Protection Command, Headquarters Medical Corps, Singapore Armed Forces, Singapore
| | - Lee Ching Ng
- Environmental Health Institute, National Environment Agency, Singapore
- School of Biological Sciences, Nanyang Technological University, Singapore
| | - Cheong Huat Tan
- Environmental Health Institute, National Environment Agency, Singapore
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28
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Wangdi K, Canavati SE, Ngo TD, Nguyen TM, Tran LK, Kelly GC, Martin NJ, Clements ACA. Spatial and Temporal Patterns of Malaria in Phu Yen Province, Vietnam, from 2005 to 2016. Am J Trop Med Hyg 2020; 103:1540-1548. [PMID: 32748781 PMCID: PMC7543816 DOI: 10.4269/ajtmh.20-0392] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Malaria in Vietnam has become focal to a few provinces, including Phu Yen. This study aimed to assess correlations between intervention (population proportion protected by insecticide-treated nets and indoor residual spraying) and climatic variables with malaria incidence in Phu Yen Province. The Vietnam National Institute of Malariology, Parasitology, and Entomology provided incidence data for Plasmodium falciparum and Plasmodium vivax for 104 communes of Phu Yen Province from January 2005 to December 2016. A multivariable, zero-inflated Poisson regression model was developed with a conditional autoregressive prior structure to identify the underlying spatial structure of the data and quantify associations with covariates. There were a total of 2,778 P. falciparum and 1,770 P. vivax cases during the study period. Plasmodium falciparum and P. vivax incidence increased by 5.4% (95% credible interval [CrI] 5.1%, 5.7%) and 3.2% (95% CrI 2.9%, 3.5%) for a 10-mm increase in precipitation without lag, respectively. Plasmodium falciparum and P. vivax incidence decreased by 7.7% (95% CrI 5.6%, 9.7%) and 10.5% (95% CrI 8.3%, 12.6%) for a 1°C increase in minimum temperature without lag, respectively. There was a > 95% probability of a higher than provincial average trend of P. falciparum and P. vivax in Song Cau and Song Hoa districts. There was a > 95% probability of a lower than provincial average trend in Tuy Dong Xuan and Hoa districts for both species. Targeted distribution of resources, including intensified interventions, in this part of the province will be required for local malaria elimination.
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Affiliation(s)
- Kinley Wangdi
- Department of Global Health, Research School of Population Health, Australian National University, Canberra, Australia
| | | | - Thang Duc Ngo
- National Institute of Malariology, Parasitology, and Entomology, Hanoi, Vietnam
| | | | | | | | | | - Archie C A Clements
- Telethon Kids Institute, Nedlands, Australia.,Faculty of Health Sciences, Curtin University, Bentley, Australia
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29
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Sumarnrote A, Overgaard HJ, Corbel V, Thanispong K, Chareonviriyaphap T, Manguin S. Species diversity and insecticide resistance within the Anopheles hyrcanus group in Ubon Ratchathani Province, Thailand. Parasit Vectors 2020; 13:525. [PMID: 33069255 PMCID: PMC7568835 DOI: 10.1186/s13071-020-04389-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2020] [Accepted: 10/06/2020] [Indexed: 01/04/2023] Open
Abstract
Background Members of the Anopheles hyrcanus group have been incriminated as important malaria vectors. This study aims to identify the species and explore the insecticide susceptibility profile within the Anopheles hyrcanus group in Ubon Ratchathani Province, northeastern Thailand where increasing numbers of malaria cases were reported in 2014. Methods Between 2013 and 2015, five rounds of mosquito collections were conducted using human landing and cattle bait techniques during both the rainy and dry seasons. Anopheles mosquitoes were morphologically identified and their insecticide susceptibility status was investigated. Synergist bioassays were carried out with An. hyrcanus (s.l.) due to their resistance to all insecticides. An ITS2-PCR assay was conducted to identify to species the Hyrcanus group specimens. Results Out of 10,361 Anopheles females collected, representing 18 taxa in 2 subgenera, 71.8% were morphologically identified as belonging to the Hyrcanus Group (subgenus Anopheles), followed by An. barbirostris group (7.9%), An. nivipes (6.5%), An. philippinensis (5.9%) and the other 14 Anopheles species. Specimens of the Hyrcanus Group were more prevalent during the rainy season and were found to be highly zoophilic. Anopheles hyrcanus (s.l.) was active throughout the night, with an early peak of activity between 18:00 h and 21:00 h. ITS2-PCR assay conducted on 603 DNA samples from specimens within the Hyrcanus Group showed the presence of five sisters species. Anopheles peditaeniatus was the most abundant species (90.5%, n = 546), followed by An. nitidus (4.5%, n = 27), An. nigerrimus (4.3%, n = 26), An. argyropus (0.5%, n = 3), and An. sinensis (0.2%, n = 1). All An. hyrcanus (s.l.) specimens that were found resistant to insecticides (deltamethrin 0.05%, permethrin 0.75% and DDT 4% and synergist tests) belonged to An. peditaeniatus. The degree of resistance in An. peditaeniatus to each of these three insecticides was approximately 50%. Addition of PBO (Piperonyl butoxide), but not DEF (S.S.S-tributyl phosphotritioate), seemed to restore susceptibility, indicating a potential role of oxidases as a detoxifying enzyme resistance mechanism. Conclusions A better understanding of mosquito diversity related to host preference, biting activity and insecticide resistance status will facilitate the implementation of locally adapted vector control strategies.![]()
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Affiliation(s)
- Anchana Sumarnrote
- Department of Entomology, Faculty of Agriculture at Kamphaeng Saen, Kasetsart University, Kamphaeng Saen Campus, Nakhon Pathom, Thailand
| | - Hans J Overgaard
- Department of Entomology, Faculty of Agriculture at Kamphaeng Saen, Kasetsart University, Kamphaeng Saen Campus, Nakhon Pathom, Thailand.,Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), Institut de Recherche pour le Développement (IRD), University of Montpellier, Montpellier, France.,Faculty of Science and Technology, Norwegian University of Life Sciences, Ås, Norway
| | - Vincent Corbel
- Department of Entomology, Faculty of Agriculture at Kamphaeng Saen, Kasetsart University, Kamphaeng Saen Campus, Nakhon Pathom, Thailand.,Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), Institut de Recherche pour le Développement (IRD), University of Montpellier, Montpellier, France
| | - Kanutcharee Thanispong
- Bureau of Vector-borne Disease, Department of Disease control, Ministry of Public Health, Nonthaburi, Thailand
| | | | - Sylvie Manguin
- HydroSciences Montpellier (HSM), Institut de Recherche pour le Développement (IRD), CNRS, Université Montpellier, Montpellier, France.
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30
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Behavioral responses to transfluthrin by Aedes aegypti, Anopheles minimus, Anopheles harrisoni, and Anopheles dirus (Diptera: Culicidae). PLoS One 2020; 15:e0237353. [PMID: 32785255 PMCID: PMC7423148 DOI: 10.1371/journal.pone.0237353] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Accepted: 07/23/2020] [Indexed: 11/26/2022] Open
Abstract
Airborne spatial repellency (SR) is characterized and distinguished from other chemical actions including contact locomotor excitation and toxicity. The use of volatile spatial repellents is a potential new intervention class for combatting mosquito-borne pathogen transmission; therefore, continuing investigations on the actions of these chemicals that modify mosquito host‐seeking behavior (i.e., bite prevention) is needed. The objective of this study is to characterize the key behavioral avoidance actions of transfluthrin (TFT) to advance spatial repellent development into practical products. Behavioral avoidance responses were observed for adult laboratory strains of Aedes aegypti, Anopheles minimus and An. dirus, and two field populations of An. harrisoni and Ae. aegypti, respectively. Established TFT sublethal (LC50 and LC75), lethal concentrations (LC99) and discriminating concentrations (DCs) were selected corresponding to each mosquito test species. Spatial repellency and contact excitation (‘irritancy’) responses on adult mosquitoes to TFT were assessed using an excito-repellency assay system. At LC50, TFT exhibited strong avoidance with An. minimus (60.1% escape) and An. dirus (80% escape) laboratory strains, showing between 12 and 16x greater escape response than Ae. aegypti (5% escape). Repellency responses for field collected Ae. aegypti and An. harrisoni were 54.9 and 47.1% escape, respectively. After adjusting the initial contact escape response (a measure of combined irritancy and repellency) to estimate only escape due to contact, the LC50 and LC99 showed moderate escape irritancy with laboratory Ae. aegypti (41.4% escape) and no contact activity against the field population. Adjustment showed only weak contact activity (16.1% escape) in laboratory An. minimus at LC50. Spatial repellency is the predominant mode of action of TFT among colonized and field mosquitoes used in this study. Established baseline (susceptible) dose-response curves assist in optimizing SR products for mosquito control and pathogen transmission prevention.
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31
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Soma DD, Zogo BM, Somé A, Tchiekoi BN, Hien DFDS, Pooda HS, Coulibaly S, Gnambani JE, Ouari A, Mouline K, Dahounto A, Ouédraogo GA, Fournet F, Koffi AA, Pennetier C, Moiroux N, Dabiré RK. Anopheles bionomics, insecticide resistance and malaria transmission in southwest Burkina Faso: A pre-intervention study. PLoS One 2020; 15:e0236920. [PMID: 32745085 PMCID: PMC7398507 DOI: 10.1371/journal.pone.0236920] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Accepted: 07/17/2020] [Indexed: 11/21/2022] Open
Abstract
Background Twenty-seven villages were selected in southwest Burkina Faso to implement new vector control strategies in addition to long lasting insecticidal nets (LLINs) through a Randomized Controlled Trial (RCT). We conducted entomological surveys in the villages during the dry cold season (January 2017), dry hot season (March 2017) and rainy season (June 2017) to describe malaria vectors bionomics, insecticide resistance and transmission prior to this trial. Methods We carried out hourly catches (from 17:00 to 09:00) inside and outside 4 houses in each village using the Human Landing Catch technique. Mosquitoes were identified using morphological taxonomic keys. Specimens belonging to the Anopheles gambiae complex and Anopheles funestus group were identified using molecular techniques as well as detection of Plasmodium falciparum infection and insecticide resistance target-site mutations. Results Eight Anopheles species were detected in the area. Anopheles funestus s.s was the main vector during the dry cold season. It was replaced by Anopheles coluzzii during the dry hot season whereas An. coluzzii and An. gambiae s.s. were the dominant species during the rainy season. Species composition of the Anopheles population varied significantly among seasons. All insecticide resistance mechanisms (kdr-w, kdr-e and ace-1 target site mutations) investigated were found in each members of the An. gambiae complex but at different frequencies. We observed early and late biting phenotypes in the main malaria vector species. Entomological inoculation rates were 2.61, 2.67 and 11.25 infected bites per human per month during dry cold season, dry hot season and rainy season, respectively. Conclusion The entomological indicators of malaria transmission were high despite the universal coverage with LLINs. We detected early and late biting phenotypes in the main malaria vector species as well as physiological insecticide resistance mechanisms. These data will be used to evaluate the impact of complementary tools to LLINs in an upcoming RCT.
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Affiliation(s)
- Dieudonné Diloma Soma
- Institut de Recherche en Sciences de la Santé (IRSS), Bobo-Dioulasso, Burkina Faso
- Université Nazi Boni, Bobo-Dioulasso, Burkina Faso
- MIVEGEC, Université de Montpellier, CNRS, IRD, Montpellier, France
- * E-mail:
| | - Barnabas Mahugnon Zogo
- MIVEGEC, Université de Montpellier, CNRS, IRD, Montpellier, France
- Institut Pierre Richet (IPR), Bouaké, Côte d’Ivoire
- Université d’Abomey Calavi, Abomey-Calavi, Benin
| | - Anthony Somé
- Institut de Recherche en Sciences de la Santé (IRSS), Bobo-Dioulasso, Burkina Faso
- MIVEGEC, Université de Montpellier, CNRS, IRD, Montpellier, France
| | - Bertin N’Cho Tchiekoi
- MIVEGEC, Université de Montpellier, CNRS, IRD, Montpellier, France
- Institut Pierre Richet (IPR), Bouaké, Côte d’Ivoire
| | | | - Hermann Sié Pooda
- Institut de Recherche en Sciences de la Santé (IRSS), Bobo-Dioulasso, Burkina Faso
- Université de Dédougou, Dédougou, Burkina Faso
| | - Sanata Coulibaly
- Institut de Recherche en Sciences de la Santé (IRSS), Bobo-Dioulasso, Burkina Faso
| | | | - Ali Ouari
- Institut de Recherche en Sciences de la Santé (IRSS), Bobo-Dioulasso, Burkina Faso
| | - Karine Mouline
- Institut de Recherche en Sciences de la Santé (IRSS), Bobo-Dioulasso, Burkina Faso
- MIVEGEC, Université de Montpellier, CNRS, IRD, Montpellier, France
| | - Amal Dahounto
- Institut de Recherche en Sciences de la Santé (IRSS), Bobo-Dioulasso, Burkina Faso
- MIVEGEC, Université de Montpellier, CNRS, IRD, Montpellier, France
| | | | - Florence Fournet
- MIVEGEC, Université de Montpellier, CNRS, IRD, Montpellier, France
| | | | - Cédric Pennetier
- MIVEGEC, Université de Montpellier, CNRS, IRD, Montpellier, France
- Institut Pierre Richet (IPR), Bouaké, Côte d’Ivoire
| | - Nicolas Moiroux
- Institut de Recherche en Sciences de la Santé (IRSS), Bobo-Dioulasso, Burkina Faso
- MIVEGEC, Université de Montpellier, CNRS, IRD, Montpellier, France
| | - Roch Kounbobr Dabiré
- Institut de Recherche en Sciences de la Santé (IRSS), Bobo-Dioulasso, Burkina Faso
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32
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Agius PA, Cutts JC, Han Oo W, Thi A, O'Flaherty K, Zayar Aung K, Kyaw Thu H, Poe Aung P, Mon Thein M, Nyi Zaw N, Yan Min Htay W, Paing Soe A, Razook Z, Barry AE, Htike W, Devine A, Simpson JA, Crabb BS, Beeson JG, Pasricha N, Fowkes FJI. Evaluation of the effectiveness of topical repellent distributed by village health volunteer networks against Plasmodium spp. infection in Myanmar: A stepped-wedge cluster randomised trial. PLoS Med 2020; 17:e1003177. [PMID: 32817632 PMCID: PMC7444540 DOI: 10.1371/journal.pmed.1003177] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Accepted: 07/29/2020] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND The World Health Organization has yet to endorse deployment of topical repellents for malaria prevention as part of public health campaigns. We aimed to quantify the effectiveness of repellent distributed by the village health volunteer (VHV) network in the Greater Mekong Subregion (GMS) in reducing malaria in order to advance regional malaria elimination. METHODS AND FINDINGS Between April 2015 and June 2016, a 15-month stepped-wedge cluster randomised trial was conducted in 116 villages in Myanmar (stepped monthly in blocks) to test the effectiveness of 12% N,N-diethylbenzamide w/w cream distributed by VHVs, on Plasmodium spp. infection. The median age of participants was 18 years, approximately half were female, and the majority were either village residents (46%) or forest dwellers (40%). No adverse events were reported during the study. Generalised linear mixed modelling estimated the effect of repellent on infection detected by rapid diagnostic test (RDT) (primary outcome) and polymerase chain reaction (PCR) (secondary outcome). Overall Plasmodium infection detected by RDT was low (0.16%; 50/32,194), but infection detected by PCR was higher (3%; 419/13,157). There was no significant protection against RDT-detectable infection (adjusted odds ratio [AOR] = 0.25, 95% CI 0.004-15.2, p = 0.512). In Plasmodium-species-specific analyses, repellent protected against PCR-detectable P. falciparum (adjusted relative risk ratio [ARRR] = 0.67, 95% CI 0.47-0.95, p = 0.026), but not P. vivax infection (ARRR = 1.41, 95% CI 0.80-2.47, p = 0.233). Repellent effects were similar when delayed effects were modelled, across risk groups, and regardless of village-level and temporal heterogeneity in malaria prevalence. The incremental cost-effectiveness ratio was US$256 per PCR-detectable infection averted. Study limitations were a lower than expected Plasmodium spp. infection rate and potential geographic dilution of the intervention. CONCLUSIONS In this study, we observed apparent protection against new infections associated with the large-scale distribution of repellent by VHVs. Incorporation of repellent into national strategies, particularly in areas where bed nets are less effective, may contribute to the interruption of malaria transmission. Further studies are warranted across different transmission settings and populations, from the GMS and beyond, to inform WHO public health policy on the deployment of topical repellents for malaria prevention. TRIAL REGISTRATION Australian and New Zealand Clinical Trials Registry (ACTRN12616001434482).
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Affiliation(s)
- Paul A Agius
- Burnet Institute, Victoria, Australia, and Yangon, Myanmar.,Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Victoria, Australia
| | - Julia C Cutts
- Burnet Institute, Victoria, Australia, and Yangon, Myanmar
| | - Win Han Oo
- Burnet Institute, Victoria, Australia, and Yangon, Myanmar
| | - Aung Thi
- Department of Public Health, Myanmar Ministry of Health and Sports, Nay Pyi Taw, Myanmar
| | - Katherine O'Flaherty
- Burnet Institute, Victoria, Australia, and Yangon, Myanmar.,Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, University of Melbourne, Melbourne, Victoria, Australia
| | | | - Htin Kyaw Thu
- Burnet Institute, Victoria, Australia, and Yangon, Myanmar
| | - Poe Poe Aung
- Burnet Institute, Victoria, Australia, and Yangon, Myanmar
| | - Myat Mon Thein
- Burnet Institute, Victoria, Australia, and Yangon, Myanmar
| | - Nyi Nyi Zaw
- Burnet Institute, Victoria, Australia, and Yangon, Myanmar
| | | | - Aung Paing Soe
- Burnet Institute, Victoria, Australia, and Yangon, Myanmar
| | - Zahra Razook
- Population Health and Immunity Division, Walter and Eliza Hall Institute of Medical Research, Melbourne, Victoria, Australia
| | - Alyssa E Barry
- Burnet Institute, Victoria, Australia, and Yangon, Myanmar.,Population Health and Immunity Division, Walter and Eliza Hall Institute of Medical Research, Melbourne, Victoria, Australia.,Global Health Division, Department of Medical Biology, University of Melbourne, Melbourne, Victoria, Australia
| | - Win Htike
- Burnet Institute, Victoria, Australia, and Yangon, Myanmar
| | - Angela Devine
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, University of Melbourne, Melbourne, Victoria, Australia.,Menzies School of Health Research, Charles Darwin University, Darwin, Northern Territory, Australia
| | - Julie A Simpson
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, University of Melbourne, Melbourne, Victoria, Australia
| | | | - James G Beeson
- Burnet Institute, Victoria, Australia, and Yangon, Myanmar.,Department of Medicine, University of Melbourne, Melbourne, Victoria, Australia.,Central Clinical School, Monash University, Melbourne, Victoria, Australia
| | | | - Freya J I Fowkes
- Burnet Institute, Victoria, Australia, and Yangon, Myanmar.,Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Victoria, Australia.,Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, University of Melbourne, Melbourne, Victoria, Australia
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33
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Shimizu S, Chotirat S, Dokkulab N, Hongchad I, Khowsroy K, Kiattibutr K, Maneechai N, Manopwisedjaroen K, Petchvijit P, Phumchuea K, Rachaphaew N, Sripoorote P, Suansomjit C, Thongyod W, Khamsiriwatchara A, Lawpoolsri S, Hanboonkunupakarn B, Sattabongkot J, Nguitragool W. Malaria cross-sectional surveys identified asymptomatic infections of Plasmodium falciparum, Plasmodium vivax and Plasmodium knowlesi in Surat Thani, a southern province of Thailand. Int J Infect Dis 2020; 96:445-451. [PMID: 32407902 DOI: 10.1016/j.ijid.2020.05.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 05/06/2020] [Accepted: 05/06/2020] [Indexed: 01/08/2023] Open
Abstract
OBJECTIVES Malaria cross-sectional surveys are rarely conducted in very low transmission settings. This study aimed to determine the prevalence and risk factors of Plasmodium infection in a near-elimination setting in southern Thailand. METHODS Two cross-sectional surveys were conducted in areas of active transmission in the Surat Thani province of Thailand in January and May 2019. PCR was used to detect Plasmodium infection. RESULTS The prevalence of Plasmodium blood infection was 0.45% and 0.61% in January and May 2019, respectively. The major parasite species was Plasmodium falciparum in January and Plasmodium vivax in May. Unexpectedly, Plasmodium knowlesi infections were also detected. Most infections, including those of Plasmodium knowlesi, were asymptomatic. Being male and staying outdoors at night-time were the only significant identified risk factors. Of people infected in January 28.0% were positive in May for the same parasite species, suggesting persistent asymptomatic infections. CONCLUSIONS Despite the very low incidence rate in Surat Thani, most malaria infections were asymptomatic. Outdoor mosquito biting at night-time is likely an important mode of malaria transmission. Unexpectedly, asymptomatic Plasmodium knowlesi infection was found, confirming previous reports of such infection in mainland Southeast Asia.
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Affiliation(s)
- Shoichi Shimizu
- Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Sadudee Chotirat
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Nichakan Dokkulab
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Isarachai Hongchad
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Kessuda Khowsroy
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Kirakorn Kiattibutr
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Nongnuj Maneechai
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | | | - Pattamaporn Petchvijit
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Kanit Phumchuea
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Nattawan Rachaphaew
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Piyarat Sripoorote
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Chayanut Suansomjit
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Waraporn Thongyod
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Amnat Khamsiriwatchara
- Center of Excellence for Biomedical and Public Health Informatics (BIOPHICS), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Saranath Lawpoolsri
- Department of Tropical Hygiene, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Borimas Hanboonkunupakarn
- Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Jetsumon Sattabongkot
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Wang Nguitragool
- Department of Molecular Tropical Medicine & Genetics, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
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Ipa M, Widawati M, Laksono AD, Kusrini I, Dhewantara PW. Variation of preventive practices and its association with malaria infection in eastern Indonesia: Findings from community-based survey. PLoS One 2020; 15:e0232909. [PMID: 32379812 PMCID: PMC7205284 DOI: 10.1371/journal.pone.0232909] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Accepted: 04/23/2020] [Indexed: 12/23/2022] Open
Abstract
Background Geographical variation may likely influence the effectiveness of prevention efforts for malaria across Indonesia, in addition to factors at the individual level, household level, and contextual factors. This study aimed to describe preventive practices at individual and a household levels applied by rural communities in five provinces in eastern Indonesia and its association with the incidence of malaria among adult (≥15 years) populations. Methods This study analyzed a subset of data of nationally representative community-based survey 2018 Riset Kesehatan Dasar (Riskesdas). Data for socio-demographic (age, gender, education and occupation) and preventive behaviors (use of mosquito bed nets while slept, insecticide-treated mosquito nets (ITNs), mosquito repellent, mosquito electric rackets, mosquito coil/electric anti-mosquito mats, and mosquito window screen) were collected. Data were analyzed using bivariate and multivariable logistic regression model. Results Total of 56,159 respondents (n = 23,070 households) living in rural areas in Maluku (n = 8044), North Maluku (n = 7356), East Nusa Tenggara (n = 23,254), West Papua (n = 5759) and Papua (n = 11,746) were included in the study. In the multivariable models, using a bed net while slept likely reduced the odds of self-reported malaria among Maluku participants. Reduced odds ratios of self-reported malaria were identified in those participants who used ITNs (North Maluku, ENT, Papua), repellent (Maluku, West Papua, Papua), anti-mosquito racket (ENT), coil (Maluku, North Maluku, Papua) and window screen (West Papua, Papua). Conclusion Our study concluded that the protective effects of preventive practices were varied among localities, suggesting the need for specific intervention programs.
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Affiliation(s)
- Mara Ipa
- Pangandaran Unit for Health Research and Development, National Institute of Health Research and Development, National Ministry of Health of Indonesia, Pangandaran, West Java, Indonesia
- * E-mail:
| | - Mutiara Widawati
- Pangandaran Unit for Health Research and Development, National Institute of Health Research and Development, National Ministry of Health of Indonesia, Pangandaran, West Java, Indonesia
| | - Agung Dwi Laksono
- Center of Research and Development of Humanities and Health Management, National Institute of Health Research and Development, National Ministry of Health of Indonesia, Jakarta, Indonesia
| | - Ina Kusrini
- Magelang Unit for Health Research and Development, National Institute of Health Research and Development, National Ministry of Health of Indonesia, Magelang, Central Java, Indonesia
| | - Pandji Wibawa Dhewantara
- Pangandaran Unit for Health Research and Development, National Institute of Health Research and Development, National Ministry of Health of Indonesia, Pangandaran, West Java, Indonesia
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35
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Lek D, Callery JJ, Nguon C, Debackere M, Sovannaroth S, Tripura R, Wojnarski M, Piola P, Khean ST, Manion K, Nguon S, Kunkel A, Vernaeve L, Peto TJ, Dantzer E, Davoeung C, Etienne W, Dondorp AM, Tuseo L, von Seidlein L, Guintran JO. Tools to accelerate falciparum malaria elimination in Cambodia: a meeting report. Malar J 2020; 19:151. [PMID: 32293452 PMCID: PMC7161105 DOI: 10.1186/s12936-020-03197-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2020] [Accepted: 03/20/2020] [Indexed: 02/06/2023] Open
Abstract
Cambodia targets malaria elimination by 2025. Rapid elimination will depend on successfully identifying and clearing malaria foci linked to forests. Expanding and maintaining universal access to early diagnosis and effective treatment remains the key to malaria control and ultimately malaria elimination in the Greater Mekong Subregion (GMS) in the foreseeable future. Mass Drug Administration (MDA) holds some promise in the rapid reduction of Plasmodium falciparum infections, but requires considerable investment of resources and time to mobilize the target communities. Furthermore, the most practical drug regimen for MDA in the GMS—three rounds of DHA/piperaquine—has lost some of its efficacy. Mass screening and treatment benefits asymptomatic P. falciparum carriers by clearing chronic infections, but in its current form holds little promise for malaria elimination. Hopes that “highly sensitive” diagnostic tests would provide substantial advances in screen and treat programmes have been shown to be misplaced. To reduce the burden on P. falciparum and Plasmodium vivax infections in people working in forested areas novel approaches to the use of malaria prophylaxis in forest workers should be explored. During an October 2019 workshop in Phnom Penh researchers and policymakers reviewed evidence of acceptability, feasibility and effectiveness of interventions to target malaria foci and interrupt P. falciparum transmission and discussed operational requirements and conditions for programmatic implementation.
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Affiliation(s)
- Dysoley Lek
- Centre for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - James J Callery
- Mahidol-Oxford University Tropical Medicine Research Unit, Mahidol University, Bangkok, Thailand
| | - Chea Nguon
- Centre for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | | | - Siv Sovannaroth
- Centre for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Rupam Tripura
- Mahidol-Oxford University Tropical Medicine Research Unit, Mahidol University, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK
| | - Marius Wojnarski
- Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | | | - Soy Ty Khean
- University Research Company Ltd., Phnom Penh, Cambodia.,London School of Hygiene and Tropical Medicine, London, UK
| | | | - Sokomar Nguon
- University Research Company Ltd., Phnom Penh, Cambodia
| | - Amber Kunkel
- Institut Pasteur du Cambodge, Phnom Penh, Cambodia.,Emerging Diseases Epidemiology Unit, Institut Pasteur, Paris, France
| | | | - Thomas J Peto
- Mahidol-Oxford University Tropical Medicine Research Unit, Mahidol University, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK
| | - Emily Dantzer
- University of California at San Francisco, San Francisco, USA
| | | | | | - Arjen M Dondorp
- Mahidol-Oxford University Tropical Medicine Research Unit, Mahidol University, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK
| | | | - Lorenz von Seidlein
- Mahidol-Oxford University Tropical Medicine Research Unit, Mahidol University, Bangkok, Thailand. .,Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK.
| | - Jean-Olivier Guintran
- Centre for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia. .,Mahidol-Oxford University Tropical Medicine Research Unit, Mahidol University, Bangkok, Thailand.
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36
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Kobylinski KC, Jittamala P, Hanboonkunupakarn B, Pukrittayakamee S, Pantuwatana K, Phasomkusolsil S, Davidson SA, Winterberg M, Hoglund RM, Mukaka M, van der Pluijm RW, Dondorp A, Day NPJ, White NJ, Tarning J. Safety, Pharmacokinetics, and Mosquito-Lethal Effects of Ivermectin in Combination With Dihydroartemisinin-Piperaquine and Primaquine in Healthy Adult Thai Subjects. Clin Pharmacol Ther 2019; 107:1221-1230. [PMID: 31697848 PMCID: PMC7285759 DOI: 10.1002/cpt.1716] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Accepted: 10/15/2019] [Indexed: 12/30/2022]
Abstract
Mass administration of antimalarial drugs and ivermectin are being considered as potential accelerators of malaria elimination. The safety, tolerability, pharmacokinetics, and mosquito‐lethal effects of combinations of ivermectin, dihydroartemisinin‐piperaquine, and primaquine were evaluated. Coadministration of ivermectin and dihydroartemisinin‐piperaquine resulted in increased ivermectin concentrations with corresponding increases in mosquito‐lethal effect across all subjects. Exposure to piperaquine was also increased when coadministered with ivermectin, but electrocardiograph QT‐interval prolongation was not increased. One subject had transiently impaired liver function. Ivermectin mosquito‐lethal effect was greater than predicted previously against the major Southeast Asian malaria vectors. Both Anopheles dirus and Anopheles minimus mosquito mortality was increased substantially (20‐fold and 35‐fold increase, respectively) when feeding on volunteer blood after ivermectin administration compared with in vitro ivermectin‐spiked blood. This suggests the presence of ivermectin metabolites that impart mosquito‐lethal effects. Further studies of this combined approach to accelerate malaria elimination are warranted.
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Affiliation(s)
- Kevin C Kobylinski
- Department of Entomology, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand.,Entomology Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland, USA
| | - Podjanee Jittamala
- Department of Tropical Hygiene, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Borimas Hanboonkunupakarn
- Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Sasithon Pukrittayakamee
- Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,The Royal Society of Thailand, Dusit, Bangkok, Thailand
| | - Kanchana Pantuwatana
- Department of Entomology, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Siriporn Phasomkusolsil
- Department of Entomology, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Silas A Davidson
- Department of Entomology, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand.,Entomology Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland, USA
| | - Markus Winterberg
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Richard M Hoglund
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Mavuto Mukaka
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Rob W van der Pluijm
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Arjen Dondorp
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Nicholas P J Day
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Nicholas J White
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Joel Tarning
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
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37
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Edwards HM, Sriwichai P, Kirabittir K, Prachumsri J, Chavez IF, Hii J. Transmission risk beyond the village: entomological and human factors contributing to residual malaria transmission in an area approaching malaria elimination on the Thailand-Myanmar border. Malar J 2019; 18:221. [PMID: 31262309 PMCID: PMC6604376 DOI: 10.1186/s12936-019-2852-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2019] [Accepted: 06/19/2019] [Indexed: 11/12/2022] Open
Abstract
Background A mixed methods study was conducted to look at the
magnitude of residual malaria transmission (RMT) and factors contributing to low (< 1% prevalence), but sustained transmission in rural communities on the Thai–Myanmar border. Methods A cross-sectional behaviour and net survey, observational surveys and entomological collections in both villages and forested farm huts frequented by community members for subsistence farming practices were conducted. Results Community members frequently stayed overnight at subsistence farm huts or in the forest. Entomological collections showed higher biting rates of primary vectors in forested farm hut sites and in a more forested village setting compared to a village with clustered housing and better infrastructure. Despite high levels of outdoor biting, biting exposure occurred predominantly indoors, particularly for non-users of long-lasting insecticidal nets (LLINs). Risk of biting exposure was exacerbated by sub-optimal coverage of LLINs, particularly in subsistence farm huts and in the forest. Furthermore, early waking hours when people had left the safety of their nets coincided with peaks in biting in later morning hours. Conclusions Entomological and epidemiological findings suggest drivers and modulators of sustained infection prevalence in the area to be: higher mosquito abundance in forested areas where LLINs were used less frequently or could not be used; late sleeping and waking times coinciding with peak biting hours; feeding preferences of Anopheles taking them away from contact with LLIN and indoor residual spraying (IRS), e.g. exophagy and zoophagy; non-use of LLIN and use of damaged/torn LLIN; high population movement across the border and into forested areas thereby increasing risk of exposure, decreasing use of protection and limiting access to healthcare; and, Plasmodium vivax predominance resulting in relapse(s) of previous infection. The findings highlight gaps in current intervention coverage beyond the village setting. Electronic supplementary material The online version of this article (10.1186/s12936-019-2852-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Hannah M Edwards
- Department of Disease Epidemiology, Imperial College London, London, UK. .,Malaria Consortium Asia, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Road, Bangkok, 10400, Thailand.
| | - Patchara Sriwichai
- Department of Entomology, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Road, Bangkok, 10400, Thailand
| | - Kirakorn Kirabittir
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Road, Bangkok, 10400, Thailand
| | - Jetsumon Prachumsri
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Road, Bangkok, 10400, Thailand
| | - Irwin F Chavez
- Department of Tropical Hygiene, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Road, Bangkok, 10400, Thailand
| | - Jeffrey Hii
- Department of Disease Epidemiology, Imperial College London, London, UK
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38
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Patterns of anopheline feeding/resting behaviour and Plasmodium infections in North Cameroon, 2011-2014: implications for malaria control. Parasit Vectors 2019; 12:297. [PMID: 31196161 PMCID: PMC6567421 DOI: 10.1186/s13071-019-3552-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 06/03/2019] [Indexed: 11/10/2022] Open
Abstract
Background Effective malaria control relies on evidence-based interventions. Anopheline behaviour and Plasmodium infections were investigated in North Cameroon, following long-lasting insecticidal net (LLIN) distribution in 2010. Methods During four consecutive years from 2011 to 2014, adult mosquitoes were collected indoors, outdoors and in exit traps across 38 locations in the Garoua, Pitoa and Mayo-Oulo health districts. Anophelines were morphologically and molecularly identified, then analysed for blood meal origins and Plasmodium falciparum circumsporozoite protein (Pf-CSP). Blood from children under 5 years-old using LLINs was examined for Plasmodium infections. Results Overall, 9376 anophelines belonging to 14 species/sibling species were recorded. Anopheles gambiae (s.l.) [An. arabiensis (73.3%), An. coluzzii (17.6%) and An. gambiae (s.s.) (9.1%)] was predominant (72%), followed by An. funestus (s.l.) (20.5%) and An. rufipes (6.5%). The recorded blood meals were mainly from humans (28%), cattle (15.6%) and sheep (11.6%) or mixed (45%). Pf-CSP rates were higher indoors (3.2–5.4%) versus outdoors (0.8–2.0%), and increased yearly (χ2 < 18, df = 10, P < 0.03). Malaria prevalence in children under 5 years-old, in households using LLINs was 30% (924/3088). Conclusions The present study revealed the variability of malaria vector resting and feeding behaviour, and the persistence of Plasmodium infections regardless the use of LLINs. Supplementary interventions to LLINs are therefore needed to sustain malaria prevention in North Cameroon.
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39
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Tananchai C, Manguin S, Bangs MJ, Chareonviriyaphap T. Malaria Vectors and Species Complexes in Thailand: Implications for Vector Control. Trends Parasitol 2019; 35:544-558. [PMID: 31182384 DOI: 10.1016/j.pt.2019.04.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 04/25/2019] [Accepted: 04/30/2019] [Indexed: 11/18/2022]
Abstract
There are seven Anopheles species incriminated as important (primary) malaria vectors in Thailand. These vectors belong to species complexes or are in closely related groups that are difficult to separate morphologically. Precise species identification, using molecular methods, enables control operations to target only important vectors and to increase understanding of their specific ecological requirements, bionomic characteristics, and behavioral traits. This review focuses on adult mosquito behavior, vector transmission capacity, and geographical distribution of malaria vectors in Thailand identified using genetic and molecular identification methods between 1994 and 2019. A better understanding of Anopheles biodiversity, biology, behavior, vector capacity, and distribution in Thailand and neighboring countries in the Greater Mekong Subregion (GMS) will facilitate more effective and efficient vector-control strategies and consequently contribute to a further decrease in the malaria burden.
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Affiliation(s)
- Chatchai Tananchai
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok 10900, Thailand
| | - Sylvie Manguin
- HydroSciences Montpellier (UMR-HSM), Institut de Recherche pour le Développement France (IRD), CNRS, Université Montpellier, Montpellier, France
| | - Michael J Bangs
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok 10900, Thailand; Public Health and Malaria Control Department, PT Freeport Indonesia, International SOS, Jl. Kertajasa, Kuala Kencana, Papua 99920, Indonesia
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40
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Alasil SM, Abdullah KA. An Epidemiological Review on Emerging and Re-Emerging Parasitic Infectious Diseases in Malaysia. Open Microbiol J 2019. [DOI: 10.2174/1874285801913010112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Emerging infectious diseases are infections that have recently appeared in a population over a defined period of time whereas, re-emerging infectious diseases are those that were once a health problem in a particular region or a country and are now emerging again. Parasitic infectious diseases represent a serious health problem in many developing countries and recently have started spreading to developed nations via international traveling or immigration. Malaysia is facing many challenges caused by various parasitic pathogens. The lack of awareness among disadvantaged populations such as the Orang Asli community and the dependency on foreign workers has led to an influx of immigrants to Malaysia from countries endemic to various parasitic diseases. Understanding the social and economic dynamics of such diseases can help anticipate and subsequently control their emergence. Raising public awareness, developing robust public health infrastructure and implementing point-of-care diagnostics will help curb the spread of such diseases. This review provides epidemiological insights into the reported emerging and re-emerging parasitic infectious diseases in Malaysia over the past two decades.
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41
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Pell CL, Adhikari B, Myo Thwin M, Kajeechiwa L, Nosten S, Nosten FH, Sahan KM, Smithuis FM, Nguyen TN, Hien TT, Tripura R, Peto TJ, Sanann N, Nguon C, Pongvongsa T, Phommasone K, Mayxay M, Mukaka M, Peerawaranun P, Kaehler N, Cheah PY, Day NPJ, White NJ, Dondorp AM, von Seidlein L. Community engagement, social context and coverage of mass anti-malarial administration: Comparative findings from multi-site research in the Greater Mekong sub-Region. PLoS One 2019; 14:e0214280. [PMID: 30908523 PMCID: PMC6433231 DOI: 10.1371/journal.pone.0214280] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Accepted: 03/11/2019] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Between 2013 and 2017, targeted malaria elimination (TME), a package of interventions that includes mass drug administration (MDA)-was piloted in communities with reservoirs of asymptomatic P. falciparum across the Greater Mekong sub-Region (GMS). Coverage in target communities is a key determinant of the effectiveness of MDA. Drawing on mixed methods research conducted alongside TME pilot studies, this article examines the impact of the community engagement, local social context and study design on MDA coverage. METHODS AND FINDINGS Qualitative and quantitative data were collected using questionnaire-based surveys, semi-structured and in-depth interviews, focus group discussions, informal conversations, and observations of study activities. Over 1500 respondents were interviewed in Myanmar, Vietnam, Cambodia and Laos. Interview topics included attitudes to malaria and experiences of MDA. Overall coverage of mass anti-malarial administration was high, particularly participation in at least a single round (85%). Familiarity with and concern about malaria prompted participation in MDA; as did awareness of MDA and familiarity with the aim of eliminating malaria. Fear of adverse events and blood draws discouraged people. Hence, community engagement activities sought to address these concerns but their impact was mediated by the trust relationships that study staff could engender in communities. In contexts of weak healthcare infrastructure and (cash) poverty, communities valued the study's ancillary care and the financial compensation. However, coverage did not necessarily decrease in the absence of cash compensation. Community dynamics, affected by politics, village conformity, and household decision-making also affected coverage. CONCLUSIONS The experimental nature of TME presented particular challenges to achieving high coverage. Nonetheless, the findings reflect those from studies of MDA under implementation conditions and offer useful guidance for potential regional roll-out of MDA: it is key to understand target communities and provide appropriate information in tailored ways, using community engagement that engenders trust.
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Affiliation(s)
- Christopher L. Pell
- Amsterdam Institute for Global Health and Development (AIGHD), Amsterdam, The Netherlands
- Centre for Social Science and Global Health, University of Amsterdam, Amsterdam, The Netherlands
| | - Bipin Adhikari
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - May Myo Thwin
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - Ladda Kajeechiwa
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - Suphak Nosten
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - Francois H. Nosten
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
- Sorbonne Universités, UPMC Univ Paris 06, UPMC UMRS CR7, Paris, France
| | - Kate M. Sahan
- Ethox Centre and Wellcome Centre for Ethics and Humanities, Nuffield Department of Population Health, Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, United Kingdom
| | - Frank M. Smithuis
- Medical Action Myanmar, Yangon, Myanmar
- Myanmar Oxford Clinical Research Unit, Yangon, Myanmar
| | - Thuy-Nhien Nguyen
- Oxford University Clinical Research Unit, Wellcome Trust Asia Programme, Ho Chi Minh City, Vietnam
| | - Tran Tinh Hien
- Oxford University Clinical Research Unit, Wellcome Trust Asia Programme, Ho Chi Minh City, Vietnam
| | - Rupam Tripura
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Thomas J. Peto
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Nou Sanann
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Chea Nguon
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | | | - Koukeo Phommasone
- Lao-Oxford-Mahosot Hospital-Wellcome Trust Research Unit (LOMWRU), Microbiology Laboratory, Vientiane, Lao PDR
| | - Mayfong Mayxay
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
- Lao-Oxford-Mahosot Hospital-Wellcome Trust Research Unit (LOMWRU), Microbiology Laboratory, Vientiane, Lao PDR
- Institute of Research and Educational Development, University of Health Sciences, Vientiane, Lao PDR
| | - Mavuto Mukaka
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Pimnara Peerawaranun
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Nils Kaehler
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Phaik Yeong Cheah
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
- Ethox Centre and Wellcome Centre for Ethics and Humanities, Nuffield Department of Population Health, Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, United Kingdom
| | - Nicholas P. J. Day
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Nicholas J. White
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Arjen M. Dondorp
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Lorenz von Seidlein
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
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Tananchai C, Pattanakul M, Nararak J, Sinou V, Manguin S, Chareonviriyaphap T. Diversity and biting patterns of Anopheles species in a malaria endemic area, Umphang Valley, Tak Province, western Thailand. Acta Trop 2019; 190:183-192. [PMID: 30439344 DOI: 10.1016/j.actatropica.2018.11.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Revised: 11/07/2018] [Accepted: 11/09/2018] [Indexed: 11/26/2022]
Abstract
Malaria is highly endemic in Umphang Valley, a district in the western edge of Tak Province, along the boundary with Kayin State of Myanmar. Although there are high indigenous malaria cases in this area every year, nothing about malaria vectors and their transmission role have been investigated before this study. The objective of this work is to characterize the Anopheles species diversity and trophic behavior of malaria vectors in the transmission area of Umphang Valley. Females of Anopheles mosquitoes were collected every two months during a two-year period. Mosquito collections were using standard collection technique, indoor and outdoor human landing collections and outdoor cattle bait collection. Anopheles mosquitoes were identified using morphological characters and multiplex AS-PCR assay for the identification of sibling species within groups and complexes present. From a total of 16,468 Anopheles females, 2723 specimens (16.54%) were collected from humans and 13,745 specimens (83.46%) were captured from cattle. From human landing collections, 2447 specimens (89.86%) of Anopheles minimus were obtained, followed by 119 Anopheles peditaeniatus (4.37%), 62 Anopheles maculatus (2.28%), 17 Anopheles dirus (0.6%), 15 Anopheles aconitus (0.5%) and 6 Anopheles sawadwongporni (0.2%) respectively. Seven putative malaria vectors, including An. minimus, An. dirus, An. baimaii, An. sawadwongporni, An. maculatus, An. pseudowillmori and An. aconitus were documented from this study and trophic behavior of each respective species were observed. Such information is definitely crucial for defining the vector capacity of each single species and for designing appropriate vector prevention and control strategies against target vector species.
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Nofal SD, Peto TJ, Adhikari B, Tripura R, Callery J, Bui TM, von Seidlein L, Pell C. How can interventions that target forest-goers be tailored to accelerate malaria elimination in the Greater Mekong Subregion? A systematic review of the qualitative literature. Malar J 2019; 18:32. [PMID: 30709399 PMCID: PMC6359845 DOI: 10.1186/s12936-019-2666-5] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 01/27/2019] [Indexed: 11/26/2022] Open
Abstract
Background Despite decreases in incidence and related mortality, malaria remains a major public health challenge in the Greater Mekong Sub-region (GMS). The emergence of artemisinin resistance threatens these gains and has prompted efforts to accelerate elimination in the region. In the GMS, transmission now clusters in hotspots along international borders and among high-risk populations, including forest-goers. To eliminate malaria in the region, interventions must target such hard-to-reach populations. This review provides a comprehensive overview of the qualitative research on behaviours and perceptions that influence uptake of and adherence to malaria interventions among forest-goers in the GMS. Methods A systematic search strategy was used to identify relevant sources, including database (OVID SP, PubMed, ISI Web of Knowledge) and bibliographic searches. Relevant findings from qualitative research methods were extracted and thematic analysis undertaken. Results Of 268 sources retrieved in searches twenty-two were reviewed. Most reported studies were conducted in Cambodia (n = 10), and were published after 2014 (n = 16). Four major themes emerged that are particularly relevant to the design of intervention packages targeted at forest-goers: (1) understanding of malaria and perceived risk; (2) preventive measures used when visiting the forest; (3) behaviours that put forest-goers at risk of infection; and, (4) malaria-related treatment seeking. There were notable differences across the reviewed articles that suggest the need for a locally tailored approach. Conclusion A more detailed characterization of forest activities is needed but research on this topic raises methodological challenges. Current vector control measures have limitations, with use of insecticidal-treated nets, hammocks and repellents influenced by the type of forest activities and the characteristics of these measures. In contrast, anti-malarial drugs, for example, as chemoprophylaxis, hold promise but require further evaluation. Electronic supplementary material The online version of this article (10.1186/s12936-019-2666-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Stephanie D Nofal
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK
| | - Thomas J Peto
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand. .,Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK.
| | - Bipin Adhikari
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Rupam Tripura
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - James Callery
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Thanh Mai Bui
- Faculty of Health, Medicine and Life Sciences, Maastricht University, Maastricht, The Netherlands
| | - Lorenz von Seidlein
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Christopher Pell
- Centre for Social Sciences and Global Health, University of Amsterdam, Amsterdam, The Netherlands.,Amsterdam Institute for Global Health and Development, Amsterdam, The Netherlands
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Chinh VD, Masuda G, Hung VV, Takagi H, Kawai S, Annoura T, Maeno Y. Prevalence of human and non-human primate Plasmodium parasites in anopheline mosquitoes: a cross-sectional epidemiological study in Southern Vietnam. Trop Med Health 2019; 47:9. [PMID: 30692869 PMCID: PMC6343293 DOI: 10.1186/s41182-019-0139-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Accepted: 01/14/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Human malaria is a major threat in rural communities of central Vietnam. Anopheles dirus and Anopheles minimus species are critical malaria vectors in Vietnam, which transmit Plasmodium parasites. However, the entomological aspects of malaria transmission in some of the central provinces of Vietnam remain unexplored. Hence, a cross-sectional entomological survey was carried out to identify the malaria vector species and the transmission of Plasmodium parasites in seven endemic provinces of Vietnam. METHODS Mosquitoes were collected from seven provinces, Gia Lai, Khanh Hoa, Phu Yen, Ninh Thuan, Binh Thuan, Dong Nai, and Binh Phuoc. The collection was conducted for four to eight consecutive nights using three established methods, indoor and outdoor human landing catches and light trap method. Nested-PCR analysis was performed to detect the Plasmodium species in the separated thorax and the abdomen of the individual mosquitoes. RESULTS A total of 2278 mosquitoes belonging to one of the four species of anopheline mosquitoes, An. dirus, An. maculatus, An. aconitus, and An. minimus were collected. Among the collected mosquitoes, 1398 were analysed using nested-PCR, of which, 40 mosquitoes were positive for Plasmodium parasites. Most of these parasites were detected in the samples from the thorax region, followed by the abdominal portion. The parasites were detected in both the thorax and abdomen of An. dirus. Seven species of Plasmodium parasites were detected during the analysis, of which, Plasmodium inui was the most common species, followed by Plasmodium falciparum, Plasmodium vivax, Plasmodium cynomolgi, Plasmodium coatneyi, Plasmodium knowlesi, and Plasmodium fieldi. Out of the 49 positive samples, 12 showed mixed infections. Co-infection of P. inui with human and other non-human primate Plasmodium species was common. CONCLUSIONS This study demonstrated the presence of human and non-human primate Plasmodium infection in An. dirus, a predominant malarial vector. Further, we showed that An. maculatus and An. minimus species also take part in malarial transmission. This might potentially lead to an alarming situation conducive for the emergence of novel zoonotic malaria.
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Affiliation(s)
- Vu Duc Chinh
- Department of Entomology, National Institute of Malariology, Parasitology and Entomology, Hanoi, Vietnam
| | - Gaku Masuda
- Center for Southeast Asian Studies, Kyoto University, Kyoto, Kyoto Japan
| | - Vu Viet Hung
- Department of Entomology, National Institute of Malariology, Parasitology and Entomology, Hanoi, Vietnam
| | - Hidekazu Takagi
- Department of Microbiology and Immunology, Aichi Medical University School of Medicine, Nagakute, Aichi Japan
| | - Satoru Kawai
- Laboratory of Tropical Medicine and Parasitology, Dokkyo Medical University, Mibu, Tochigi Japan
| | - Takeshi Annoura
- Department of Parasitology, National Institute of Infectious Diseases, Tokyo, Japan
| | - Yoshimasa Maeno
- Department of Virology and Parasitology, Fujita Health University School of Medicine, 1-98 Kutsukake, Toyoake, Aichi 470-1192 Japan
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Abstract
Vector control has significantly reduced malaria morbidity in many regions of the world where the disease was endemic and is now moving toward malaria elimination. Among the tools available for vector control, the use of long-lasting insecticidal bed nets (LLINs) and indoor residual spraying (IRS) has proved most effective. However, Anopheles mosquitoes are becoming increasingly resistant to insecticides. In this chapter, we describe the main aspects of vector control-with a particular focus on insecticidal products commonly used in vector control as well as on mechanisms of insecticide resistance. We also discuss the impact of insecticide resistance on malaria transmission.
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46
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Win Han Oo, Cutts JC, Agius PA, Kyaw Zayar Aung, Poe Poe Aung, Aung Thi, Nyi Nyi Zaw, Htin Kyaw Thu, Wai Yan Min Htay, Ataide R, O'Flaherty K, Ai Pao Yawn, Aung Paing Soe, Beeson JG, Crabb B, Pasricha N, Fowkes FJI. Effectiveness of repellent delivered through village health volunteers on malaria incidence in villages in South-East Myanmar: a stepped-wedge cluster-randomised controlled trial protocol. BMC Infect Dis 2018; 18:663. [PMID: 30547749 PMCID: PMC6295052 DOI: 10.1186/s12879-018-3566-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Accepted: 11/29/2018] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND To combat emerging drug resistance in the Greater Mekong Sub-region (GMS) the World Health Organization and GMS countries have committed to eliminating malaria in the region by 2030. The overall approach includes providing universal access to diagnosis and treatment of malaria, and sustainable preventive measures, including vector control. Topical repellents are an intervention that can be used to target residual malaria transmission not covered by long lasting insecticide nets and indoor residual spraying. Although there is strong evidence that topical repellents protect against mosquito bites, evidence is not well established for the effectiveness of repellents distributed as part of malaria control activities in protecting against episodes of malaria. A common approach to deliver malaria services is to assign Village Health Volunteers (VHVs) to villages, particularly where limited or no services exist. The proposed trial aims to provide evidence for the effectiveness of repellent distributed through VHVs in reducing malaria. METHODS The study is an open stepped-wedge cluster-randomised controlled trial randomised at the village level. Using this approach, repellent (N,N-diethyl-benzamide - 12% w/w, cream) is distributed by VHVs in villages sequentially throughout the malaria transmission season. Villages will be grouped into blocks, with blocks transitioned monthly from control (no repellent) to intervention states (to receive repellent) across 14 monthly intervals in random order). This follows a 4-week baseline period where all villages do not receive repellent. The primary endpoint is defined as the number of individuals positive for Plasmodium falciparum and Plasmodium vivax infections diagnosed by a rapid diagnostic test. Secondary endpoints include symptomatic malaria, Polymerase Chain Reaction (PCR)-detectable Plasmodium spp. infections, molecular markers of drug resistance and antibodies specific for Plasmodium spp. parasites. DISCUSSION This study has been approved by relevant institutional ethics committees in Myanmar and Australia. Results will be disseminated through workshops, conferences and peer-reviewed publications. Findings will contribute to a better understanding of the optimal distribution mechanisms of repellent, context specific effectiveness and inform policy makers and implementers of malaria elimination programs in the GMS. TRIAL REGISTRATION Australian and New Zealand Clinical Trials Registry ( ACTRN12616001434482 ). Retrospectively registered 14th October 2016.
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Affiliation(s)
- Win Han Oo
- Burnet Institute, Melbourne, Australia.,Burnet Institute, Yangon, Myanmar
| | | | - Paul A Agius
- Burnet Institute, Melbourne, Australia.,Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia.,Judith Lumley Centre, La Trobe University, Melbourne, Australia
| | | | | | - Aung Thi
- Department of Public Health, Myanmar Ministry of Health and Sport, Nay Pyi Taw, Myanmar
| | | | | | | | | | - Katherine O'Flaherty
- Burnet Institute, Melbourne, Australia.,Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, University of Melbourne, Melbourne, Australia
| | | | | | - James G Beeson
- Burnet Institute, Melbourne, Australia.,Department of Medicine, University of Melbourne, Melbourne, Australia.,Department of Microbiology and Central Clinical School, Monash University, Melbourne, Australia
| | | | | | - Freya J I Fowkes
- Burnet Institute, Melbourne, Australia. .,Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia. .,Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, University of Melbourne, Melbourne, Australia.
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Lek D, Gopinath D, Ek S, Heng S, Bun S, Say C, Sokomar N, Ty KS, Rekol H. Assessment of net lending strategy to better reach mobile and migrant populations in malaria endemic areas of Cambodia. Infect Dis Poverty 2018; 7:107. [PMID: 30340543 PMCID: PMC6194585 DOI: 10.1186/s40249-018-0489-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Accepted: 10/04/2018] [Indexed: 11/06/2022] Open
Abstract
Background In Cambodia, internal migration involves migrants moving from non-malaria endemic areas to malaria endemic areas and vice versa. The majority of them work in farms or forests with various malaria transmission levels. In Cambodia, as one of the national approaches to ensure LLIN accessibility and use among mobile and migrant populations (MMPs), a lending scheme of long lasting insecticide treated nets (LLINs) was initiated among farm workers. Through this net lending program, LLINs and long-lasting insecticide treated hammock nets (LLIHNs) will be distributed annually at workplace (e.g. longstanding farms, plantations, industrial sites, as identified by operational district and health center staff) on a ratio of one LLIN per one worker. The main objective of this study is to assess MMPs’ accessibility to LLINs through a lending scheme with plantation owners in remote malaria endemic areas of Cambodia. Methods The study used a cross-sectional survey among MMPs using two-stage cluster sampling method. The sampling frame is the list of farms in the four provinces of Banteay Meanchey, Battambang, Pailin, and Pursat in western and northwestern Cambodia bordering with Thailand where the LLIN lending scheme was implemented and where an estimated 100 000 MMPs worked annually. The assessment was carried out from January to February 2013 in these four provinces. It was estimated that 768 workers would be required. Results A total of 702 MMPs were interviewed. The ratio of male: female is 1:1. The age group of 21–60 was the largest accounting for 77.6%. About 91% of the MMPs stayed on the farm for less than 6 months. 93.2% of them owned either untreated or insecticide treated nets. LLINs and LLIHNs accounted for 89.5%; and 46.6% of them borrowed the nets from a lending scheme. Among those workers who have LLINs/LLIHNs, 99% slept under LLINs/LLIHNs the night before. However, only 87.4% knew that sleeping under LLINs/LLIHNs protects against malaria. Conclusions LLIN lending scheme provides an important delivery channel for a substantial percentage of net accessibility (46.6%) to the Cambodian national free-net distribution campaign in remote malaria endemic areas. Electronic supplementary material The online version of this article (10.1186/s40249-018-0489-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Dysoley Lek
- National Center for Parasitology Entomology and Malaria Control, Corner St. 92, village Trapeng Svay, Phnom Penh Thmey, Sen Sok, Phnom Penh, Cambodia. .,School of Public Health, National Institute of Public Health, Phnom Penh, Cambodia.
| | - Deyer Gopinath
- World Health Organization Country Office for Thailand, Nonthaburi, Thailand
| | - Sovann Ek
- University Research Co, LLC, Phnom Penh, Cambodia
| | - Sopheab Heng
- School of Public Health, National Institute of Public Health, Phnom Penh, Cambodia
| | - Sreng Bun
- Department of Communicable Diseases Control, Ministry of Health, Phnom Penh, Cambodia
| | - Chy Say
- University Research Co, LLC, Phnom Penh, Cambodia
| | | | | | - Huy Rekol
- National Center for Parasitology Entomology and Malaria Control, Corner St. 92, village Trapeng Svay, Phnom Penh Thmey, Sen Sok, Phnom Penh, Cambodia
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Wangdi K, Canavati SE, Ngo TD, Tran LK, Nguyen TM, Tran DT, Martin NJ, Clements ACA. Analysis of clinical malaria disease patterns and trends in Vietnam 2009-2015. Malar J 2018; 17:332. [PMID: 30223843 PMCID: PMC6142383 DOI: 10.1186/s12936-018-2478-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Accepted: 09/05/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Viet Nam has made tremendous progress towards reducing mortality and morbidity associated with malaria in recent years. Despite the success in malaria control, there has been a recent increase in cases in some provinces. In order to understand the changing malaria dynamics in Viet Nam and measure progress towards elimination, the aim of this study was to describe and quantify spatial and temporal trends of malaria by species at district level across the country. METHODS Malaria case reports at the Viet Nam National Institute of Malariology, Parasitology, and Entomology were reviewed for the period of January 2009 to December 2015. The population of each district was obtained from the Population and Housing Census-2009. A multivariate (insecticide-treated mosquito nets [ITN], indoor residual spraying [IRS], maximum temperature), zero-inflated, Poisson regression model was developed with spatial and spatiotemporal random effects modelled using a conditional autoregressive prior structure, and with posterior parameters estimated using Bayesian Markov chain Monte Carlo simulation with Gibbs sampling. Covariates included in the models were coverage of intervention (ITN and IRS) and maximum temperature. RESULTS There was a total of 57,713 Plasmodium falciparum and 32,386 Plasmodium vivax cases during the study period. The ratio of P. falciparum to P. vivax decreased from 4.3 (81.0% P. falciparum; 11,121 cases) in 2009 to 0.8 (45.0% P. falciparum; 3325 cases) in 2015. Coverage of ITN was associated with decreased P. falciparum incidence, with a 1.1% (95% credible interval [CrI] 0.009%, 1.2%) decrease in incidence for 1% increase in the ITN coverage, but this was not the case for P. vivax, nor was it the case for IRS coverage. Maximum temperature was associated with increased incidence of both species, with a 4% (95% CrI 3.5%, 4.3%) and 1.6% (95% CrI 0.9%, 2.0%) increase in P. falciparum and P. vivax incidence for a temperature increase of 1 °C, respectively. Temporal trends of P. falciparum and P. vivax incidence were significantly higher than the national average in Central and Central-Southern districts. CONCLUSION Interventions (ITN distribution) and environmental factors (increased temperature) were associated with incidence of P. falciparum and P. vivax during the study period. The factors reviewed were not exhaustive, however the data suggest distribution of resources can be targeted to areas and times of increased malaria transmission. Additionally, changing distribution of the two predominant malaria species in Viet Nam will require different programmatic approaches for control and elimination.
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Affiliation(s)
- Kinley Wangdi
- Department of Global Health, Research School of Population Health, Australian National University, Canberra, Australia.
| | | | | | | | | | - Duong Thanh Tran
- National Institute of Malariology, Parasitology, and Entomology, Hanoi, Viet Nam
| | - Nicholas J Martin
- U.S. Naval Medical Research Unit No. 2, PSA Sembawang Deptford Rd, Building 7-4, 759657, Singapore, Singapore
| | - Archie C A Clements
- Department of Global Health, Research School of Population Health, Australian National University, Canberra, Australia.,Faculty of Health Sciences, Curtin University, Bentley, Perth, Australia
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49
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Killeen GF, Reed TE. The portfolio effect cushions mosquito populations and malaria transmission against vector control interventions. Malar J 2018; 17:291. [PMID: 30097031 PMCID: PMC6086012 DOI: 10.1186/s12936-018-2441-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 08/02/2018] [Indexed: 12/03/2022] Open
Abstract
BACKGROUND Portfolio effects were first described as a basis for mitigating against financial risk by diversifying investments. Distributing investment across several different assets can stabilize returns and reduce risks by statistical averaging of individual asset dynamics that often correlate weakly or negatively with each other. The same simple probability theory is equally applicable to complex ecosystems, in which biological and environmental diversity stabilizes ecosystems against natural and human-mediated perturbations. Given the fundamental limitations to how well the full complexity of ecosystem dynamics can be understood or anticipated, the portfolio effect concept provides a simple framework for more critical data interpretation and pro-active conservation management. Applied to conservation ecology purposes, the portfolio effect concept informs management strategies emphasizing identification and maintenance of key ecological processes that generate complexity, diversity and resilience against inevitable, often unpredictable perturbations. IMPLICATIONS Applied to the reciprocal goal of eliminating the least valued elements of global biodiversity, specifically lethal malaria parasites and their vector mosquitoes, simply understanding the portfolio effect concept informs more cautious interpretation of surveillance data and simulation model predictions. Malaria transmission mediated by guilds of multiple vectors in complex landscapes, with highly variable climatic and meteorological conditions, as well as changing patterns of land use and other human behaviours, will systematically tend to be more resilient to attack with vector control than it appears based on even the highest quality surveillance data or predictive models. CONCLUSION Malaria vector control programmes may need to be more ambitious, interpret their short-to-medium term assessments of intervention impact more cautiously, and manage stakeholder expectations more conservatively than has often been the case thus far.
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Affiliation(s)
- Gerry F Killeen
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Ifakara, United Republic of Tanzania.
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.
| | - Thomas E Reed
- School of Biological, Earth and Environmental Sciences, University College Cork, Western Road, Cork, Republic of Ireland
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50
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Goldlust SM, Thuan PD, Giang DDH, Thang ND, Thwaites GE, Farrar J, Thanh NV, Nguyen TD, Grenfell BT, Boni MF, Hien TT. The decline of malaria in Vietnam, 1991-2014. Malar J 2018; 17:226. [PMID: 29880051 PMCID: PMC5992833 DOI: 10.1186/s12936-018-2372-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 05/28/2018] [Indexed: 02/04/2023] Open
Abstract
Background Despite the well-documented clinical efficacy of artemisinin-based combination therapy (ACT) against malaria, the population-level effects of ACT have not been studied thoroughly until recently. An ideal case study for these population-level effects can be found in Vietnam’s gradual adoption of artemisinin in the 1990s. Methods and results Analysis of Vietnam’s national annual malaria reports (1991–2014) revealed that a 10% increase in artemisinin procurement corresponded to a 32.8% (95% CI 27.7–37.5%) decline in estimated malaria cases. There was no consistent national or regional effect of vector control on malaria. The association between urbanization and malaria was generally negative and sometimes statistically significant. Conclusions The decline of malaria in Vietnam can largely be attributed to the adoption of artemisinin-based case management. Recent analyses from Africa showed that insecticide-treated nets had the greatest effect on lowering malaria prevalence, suggesting that the success of interventions is region-specific. Continuing malaria elimination efforts should focus on both vector control and increased access to ACT. Electronic supplementary material The online version of this article (10.1186/s12936-018-2372-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Sandra M Goldlust
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Ho Chi Minh City, Vietnam.,Department of Biology, Georgetown University, Washington, DC, USA.,Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA
| | - Phung Duc Thuan
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Ho Chi Minh City, Vietnam
| | - Dang Duy Hoang Giang
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Ho Chi Minh City, Vietnam
| | - Ngo Duc Thang
- National Institutes for Malariology, Parasitology, and Entomology, Hanoi, Vietnam
| | - Guy E Thwaites
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Ho Chi Minh City, Vietnam.,Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Jeremy Farrar
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Ho Chi Minh City, Vietnam.,The Wellcome Trust, London, UK
| | - Ngo Viet Thanh
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Ho Chi Minh City, Vietnam
| | - Tran Dang Nguyen
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Ho Chi Minh City, Vietnam
| | - Bryan T Grenfell
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA
| | - Maciej F Boni
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Ho Chi Minh City, Vietnam. .,Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK. .,Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University, University Park, PA, USA.
| | - Tran Tinh Hien
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Ho Chi Minh City, Vietnam.,Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
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