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Cassidy-Seyoum SA, Chheng K, Chanpheakdey P, Meershoek A, Hsiang MS, von Seidlein L, Tripura R, Adhikari B, Ley B, Price RN, Lek D, Engel N, Thriemer K. Implementation of Glucose-6-Phosphate Dehydrogenase (G6PD) testing for Plasmodium vivax case management, a mixed method study from Cambodia. PLOS GLOBAL PUBLIC HEALTH 2024; 4:e0003476. [PMID: 39028699 PMCID: PMC11259306 DOI: 10.1371/journal.pgph.0003476] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Accepted: 06/20/2024] [Indexed: 07/21/2024]
Abstract
Plasmodium vivax remains a challenge for malaria elimination since it forms dormant liver stages (hypnozoites) that can reactivate after initial infection. 8-aminoquinolone drugs kill hypnozoites but can cause severe hemolysis in individuals with Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency. The STANDARD G6PD test (Biosensor) is a novel point-of-care diagnostic capable of identifying G6PD deficiency prior to treatment. In 2021, Cambodia implemented the Biosensor to facilitate radical cure treatment for vivax malaria. To assess the Biosensor's implementation after its national rollout, a mixed-methods study was conducted in eight districts across three provinces in Cambodia. Interviews, focus group discussions, and observations explored stakeholders' experiences with G6PD testing and factors influencing its implementation. Quantitative data illustrative of test implementation were gathered from routine surveillance forms and key proportions derived. Qualitative data were analyzed thematically. The main challenge to implementing G6PD testing was that only 49.2% (437/888) of eligible patients reached health centers for G6PD testing following malaria diagnosis by community health workers. Factors influencing this included road conditions and long distances to the health center, compounded by the cost of seeking further care and patients' perceptions of vivax malaria and its treatment. 93.9% (790/841) of eligible vivax malaria patients who successfully completed referral (429/434) and directly presented to the health center (360/407) were G6PD tested. Key enabling factors included the test's acceptability among health workers and their understanding of the rationale for testing. Only 36.5% (443/1213) of eligible vivax episodes appropriately received primaquine. 70.5% (165/234) of female patients and all children under 20 kilograms never received primaquine. Our findings suggest that access to radical cure requires robust infrastructure and income security, which would likely improve referral rates to health centers enabling access. Bringing treatment closer to patients, through community health workers and nuanced community engagement, would improve access to curative treatment of vivax malaria.
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Affiliation(s)
- Sarah A. Cassidy-Seyoum
- Global and Tropical Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, Australia
- Department of Health Ethics and Society, Care and Public Health Research Institute (CAPHRI), Maastricht University, Maastricht, The Netherlands
| | - Keoratha Chheng
- Faculty of Tropical Medicine, Mahidol Oxford Research Unit, Mahidol University, Bangkok, Thailand
| | - Phal Chanpheakdey
- Faculty of Tropical Medicine, Mahidol Oxford Research Unit, Mahidol University, Bangkok, Thailand
| | - Agnes Meershoek
- Department of Health Ethics and Society, Care and Public Health Research Institute (CAPHRI), Maastricht University, Maastricht, The Netherlands
| | - Michelle S. Hsiang
- Institute for Global Health Sciences, Malaria Elimination Initiative, University of California San Francisco, San Francisco, California, United States of America
- Department of Epidemiology and Biostatistics, University of California San Francisco, San Francisco, California, United States of America
- Department of Pediatrics, Division of Pediatric Infectious Diseases, University of California San Francisco, San Francisco, California, United States of America
| | - Lorenz von Seidlein
- Faculty of Tropical Medicine, Mahidol Oxford Research Unit, Mahidol University, Bangkok, Thailand
- Nuffield Department of Medicine, Center for Tropical Medicine and Global Health, University of Oxford, Oxford, United Kingdom
| | - Rupam Tripura
- Faculty of Tropical Medicine, Mahidol Oxford Research Unit, Mahidol University, Bangkok, Thailand
- Nuffield Department of Medicine, Center for Tropical Medicine and Global Health, University of Oxford, Oxford, United Kingdom
| | - Bipin Adhikari
- Faculty of Tropical Medicine, Mahidol Oxford Research Unit, Mahidol University, Bangkok, Thailand
- Nuffield Department of Medicine, Center for Tropical Medicine and Global Health, University of Oxford, Oxford, United Kingdom
| | - Benedikt Ley
- Global and Tropical Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, Australia
- Division of Education, Menzies School of Health Research, Charles Darwin University, Darwin, Australia
| | - Ric N. Price
- Global and Tropical Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, Australia
- Faculty of Tropical Medicine, Mahidol Oxford Research Unit, Mahidol University, Bangkok, Thailand
- Nuffield Department of Medicine, Center for Tropical Medicine and Global Health, University of Oxford, Oxford, United Kingdom
| | - Dysoley Lek
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
- National Institute of Public Health, School of Public Health, Phnom Penh, Cambodia
| | - Nora Engel
- Department of Health Ethics and Society, Care and Public Health Research Institute (CAPHRI), Maastricht University, Maastricht, The Netherlands
| | - Kamala Thriemer
- Global and Tropical Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, Australia
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Dysoley L, Callery JJ, Bunreth V, Vanna M, Davoeung C, Sovann Y, You S, Ol S, Tripura R, Chew R, Chandna A, Christiansen-Jucht C, Hughes J, Sokomar N, Sophornarann T, Rideout J, Veyvath T, Sarith O, Puthy T, Sothearoth H, An SS, Zaman SI, von Seidlein L, Vanthy L, Sodavuth P, Vannak C, Dondorp AM, Lubell Y, Maude RJ, Peto TJ, Adhikari B. Expanding the roles of community health workers to sustain programmes during malaria elimination: a meeting report on operational research in Southeast Asia. Malar J 2024; 23:2. [PMID: 38166839 PMCID: PMC10759643 DOI: 10.1186/s12936-023-04828-4] [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: 10/17/2023] [Accepted: 12/20/2023] [Indexed: 01/05/2024] Open
Abstract
In Southeast Asia malaria elimination is targeted by 2030. Cambodia aims to achieve this by 2025, driven in large part by the urgent need to control the spread of artemisinin-resistant falciparum malaria infections. Rapid elimination depends on sustaining early access to diagnosis and effective treatment. In much of Cambodia, rapid elimination will rely on a village malaria worker (VMW) network. Yet as malaria declines and is no longer a common cause of febrile illness, VMWs may become less popular with febrile patients, as VMWs do not diagnose or treat other conditions at present. There is a risk that VMWs become inactive and malaria rebounds before the complete interruption of transmission is achieved.During 2021-23 a large-scale operational research study was conducted in western Cambodia to explore how a VMW network could be sustained by including health activities that cover non-malarial illnesses to encourage febrile patients to continue to attend. 105 VMWs received new rapid diagnostic tests (including dengue antigen-antibody and combined malaria/C-reactive protein tests), were trained in electronic data collection, and attended health education packages on hygiene and sanitation, disease surveillance and first aid, management of mild illness, and vaccination and antenatal care.In August 2023 the National Malaria Control Programme of Cambodia convened a stakeholder meeting in Battambang, Cambodia. Findings from the study were reviewed in the context of current malaria elimination strategies. The discussions informed policy options to sustain the relevance of the VMW network in Cambodia, and the potential for its integration with other health worker networks. This expansion could ensure VMWs remain active and relevant until malaria elimination is accomplished.
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Affiliation(s)
- Lek Dysoley
- National Centre for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia.
- National Institute for Public Health, Phnom Penh, Cambodia.
| | - James J Callery
- Mahidol‑Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK
| | | | - Moul Vanna
- Action for Health Development, Battambang, Cambodia
| | | | - Yok Sovann
- Provincial Health Department, Pailin, Cambodia
| | - Sles You
- Provincial Health Department, Battambang, Cambodia
| | - Sam Ol
- Action for Health Development, Battambang, Cambodia
- President's Malaria Initiative, Phnom Penh, Cambodia
| | - Rupam Tripura
- Mahidol‑Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK
| | - Rusheng Chew
- Mahidol‑Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK
- Faculty of Medicine, University of Queensland, Brisbane, Australia
| | - Arjun Chandna
- Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK
- Cambodia Oxford Medical Research Unit, Angkor Hospital for Children, Siem Reap, Cambodia
| | | | - Jayme Hughes
- Clinton Health Access Initiative, Phnom Penh, Cambodia
| | - Nguon Sokomar
- Cambodia Malaria Elimination Project 2, Phnom Penh, Cambodia
- University Research Company Ltd, Phnom Penh, Cambodia
- United States Agency for International Development, Phnom Penh, Cambodia
| | - Top Sophornarann
- Cambodia Malaria Elimination Project 2, Phnom Penh, Cambodia
- University Research Company Ltd, Phnom Penh, Cambodia
- United States Agency for International Development, Phnom Penh, Cambodia
| | - Jeanne Rideout
- Cambodia Malaria Elimination Project 2, Phnom Penh, Cambodia
- University Research Company Ltd, Phnom Penh, Cambodia
- United States Agency for International Development, Phnom Penh, Cambodia
| | - Tat Veyvath
- Provincial Health Department, Battambang, Cambodia
| | - Oum Sarith
- Provincial Health Department, Pailin, Cambodia
| | - Thaung Puthy
- Provincial Health Department, Battambang, Cambodia
| | | | - Sen Sam An
- Cambodia Malaria Elimination Project 2, Phnom Penh, Cambodia
- University Research Company Ltd, Phnom Penh, Cambodia
- United States Agency for International Development, Phnom Penh, Cambodia
| | - Sazid Ibna Zaman
- Mahidol‑Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Lorenz von Seidlein
- Mahidol‑Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK
| | - Lim Vanthy
- Action for Health Development, Battambang, Cambodia
| | - Preap Sodavuth
- United Nations Office for Project Services, Phnom Penh, Cambodia
| | - Chrun Vannak
- United Nations Office for Project Services, Phnom Penh, Cambodia
| | - Arjen M Dondorp
- Mahidol‑Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK
| | - Yoel Lubell
- Mahidol‑Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK
| | - Richard J Maude
- Mahidol‑Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK
- The Open University, Milton Keynes, 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, 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, University of Oxford, Oxford, UK.
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Adhikari B, Bayo M, Peto TJ, Callery JJ, Tripura R, Dysoley L, Mshamu S, Gesase S, von Seidlein L, Dondorp AM. Comparing the roles of community health workers for malaria control and elimination in Cambodia and Tanzania. BMJ Glob Health 2023; 8:e013593. [PMID: 38070880 PMCID: PMC10729139 DOI: 10.1136/bmjgh-2023-013593] [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: 08/01/2023] [Accepted: 11/12/2023] [Indexed: 12/18/2023] Open
Abstract
The reduction of deaths from malaria in sub-Saharan Africa (SSA) is stalling, whereas many countries in Southeast Asia are approaching malaria elimination. We reviewed the role of community health worker (CHW) programmes in malaria control and elimination between regions, with a more detailed description of the programmes in Tanzania and Cambodia. Compared with Tanzania, Cambodia has a much more developed CHW network, which has been pivotal in the near elimination of malaria. In Tanzania, the malaria burden has remained similar over the last decade and treatment continues to rely on healthcare facilities, which provide more limited access to early diagnosis and treatment. Overall, the proportion of malaria cases treated by CHWs is substantially lower in SSA than in Southeast Asia. Even though networks of CHWs are resource intensive and malaria epidemiology differs substantially between countries, there is a strong case for expanding CHW networks in rural SSA to improve early access to effective malaria treatment and reduce the malaria burden.
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Affiliation(s)
- 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, Oxford, UK
| | - Makhily Bayo
- Faculty of Medicine, University of Amsterdam, Amsterdam, The Netherlands
| | - 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, Oxford, UK
| | - James J Callery
- 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, 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, Oxford, UK
| | - Lek Dysoley
- C.N.M National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
- School of Public Health, National Institute of Public Health, Phnom Penh, Cambodia
| | - Salum Mshamu
- Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK, Oxford, UK
- CSK Research Solutions, Mtwara, Tanzania
| | - Samwel Gesase
- Korogwe Research Laboratory, National Institute for Medical Research, Tanga, Tanzania
| | - 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, Oxford, UK
| | - 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 Clinical Medicine, University of Oxford, Oxford, UK, Oxford, UK
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Adhikari B, Tripura R, Peto TJ, Callery JJ, von Seidlein L, Dysoley L, Dondorp AM. Village malaria workers for the community-based management of vivax malaria. THE LANCET REGIONAL HEALTH. SOUTHEAST ASIA 2023; 9:100128. [PMID: 37383038 PMCID: PMC10306055 DOI: 10.1016/j.lansea.2022.100128] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 11/23/2022] [Accepted: 11/25/2022] [Indexed: 06/30/2023]
Abstract
In Cambodia, malaria cases are on a trajectory towards the goal of malaria elimination by 2025. Vivax malaria is difficult to eliminate because of hypnozoites that can cause relapse. Primaquine, an 8-aminoquinoline, clears hypnozoites but requires testing for glucose-6-phosphate dehydrogenase (G6PD) deficiency. Routine primaquine treatment of vivax malaria has recently been implemented in Cambodia in which Village Malaria Workers (VMWs) diagnose vivax malaria by rapid diagnostic test and refer patients to health centres for G6PD testing and further treatment. Patients are referred back to the VMWs for monitoring adverse symptoms and treatment adherence. This article explores how VMWs' roles might be optimized for the community-based management of vivax malaria. With sufficient training and supervision, the role of VMWs might be expanded to include G6PD testing, making referral to the health centre superfluous. Community-based management of vivax malaria could increase the coverage of radical cure and accelerate vivax malaria elimination.
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Affiliation(s)
- 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
| | - 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
| | - James J. Callery
- 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
| | - 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
| | - Lek Dysoley
- C.N.M National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
- School of Public Health, National Institute of Public Health, Phnom Penh, Cambodia
| | - 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 Clinical Medicine, University of Oxford, Oxford, UK
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Kheang ST, Ridley R, Ngeth E, Ir P, Ngor P, Sovannaroth S, Lek D, Phon S, Kak N, Yeung S. G6PD testing and radical cure for Plasmodium vivax in Cambodia: A mixed methods implementation study. PLoS One 2022; 17:e0275822. [PMID: 36264996 PMCID: PMC9584508 DOI: 10.1371/journal.pone.0275822] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 09/25/2022] [Indexed: 11/06/2022] Open
Abstract
Introduction Cambodia aims to eliminate malaria by 2025, however tackling Plasmodium vivax (P.v) presents multiple challenges. The prevalence of glucose-6-phosphate dehydrogenase (G6PD) deficiency has prevented the deployment of 8-aminoquinolones for “radical cure”, due to the risk of severe haemolysis. Patients with P. vivax have therefore continued to experience recurrent relapses leading to cumulative health and socioeconomic burden. The recent advent of point of care testing for G6PD deficiency has made radical cure a possibility, however at the time of the study lack of operational experience and guidance meant that they had not been introduced. This study therefore aimed to design, implement and evaluate a new care pathway for the radical cure of P.vivax. Methods This implementation study took place in Pursat province, Western Cambodia. The interventions were co-developed with key stakeholders at the national, district, and local level, through a continuous process of consultations as well as formal meetings. Mixed methods were used to evaluate the feasibility of the intervention including its uptake (G6PD testing rate and the initiation of primaquine treatment according to G6PD status); adherence (self-reported); and acceptability, using quantitative analysis of primary and secondary data as well as focus group discussions and key informant interviews. Results The co-development process resulted in the design of a new care pathway with supporting interventions, and a phased approach to their implementation. Patients diagnosed with P.v infection by Village Malaria Workers (VMWs) were referred to local health centres for point-of-care G6PD testing and initiation of radical cure treatment with 14-day or 8-week primaquine regimens depending on G6PD status. VMWs carried out follow-up in the community on days 3, 7 and 14. Supporting interventions included training, community sensitisation, and the development of a smartphone and tablet application to aid referral, follow-up and surveillance. The testing rate was low initially but increased rapidly over time, reflecting the deliberately cautious phased approach to implementation. In total 626 adults received G6PD testing, for a total of 675 episodes. Of these 555 occurred in patients with normal G6PD activity and nearly all (549/555, 98.8%) were initiated on PQ14. Of the 120 with deficient/intermediate G6PD activity 61 (50.8%) were initiated on PQ8W. Self-reported adherence was high (100% and 95.1% respectively). No severe adverse events were reported. The pathway was found to be highly acceptable by both staff and patients. The supporting interventions and gradual introduction were critical to success. Challenges included travel to remote areas and mobility of P.v patients. Conclusion The new care pathway with supporting interventions was highly feasible with high levels of uptake, adherence and acceptability in this setting where high prevalence of G6PD deficiency is high and there is a well-established network of VMWs. Scaling up of the P.v radical cure programme is currently underway in Cambodia and a decline in reduction in the burden of malaria is being seen, bringing Cambodia a step closer to elimination.
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Affiliation(s)
- Soy Ty Kheang
- The Center for Health and Social Development (HSD), Phnom Penh, Cambodia
- National Institute of Public Health (NIPH), Phnom Penh, Cambodia
| | - Rosemarie Ridley
- Clinical Research Department, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine (LSHTM), London, United Kingdom
| | - Eng Ngeth
- The Center for Health and Social Development (HSD), Phnom Penh, Cambodia
| | - Por Ir
- The Center for Health and Social Development (HSD), Phnom Penh, Cambodia
- National Institute of Public Health (NIPH), Phnom Penh, Cambodia
| | - Pengby Ngor
- National Malaria Control Program, The National Center for Parasitology, Entomology and Malaria Control (CNM), Phnom Penh, Cambodia
| | - Siv Sovannaroth
- National Malaria Control Program, The National Center for Parasitology, Entomology and Malaria Control (CNM), Phnom Penh, Cambodia
| | - Dysoley Lek
- National Malaria Control Program, The National Center for Parasitology, Entomology and Malaria Control (CNM), Phnom Penh, Cambodia
| | - Somaly Phon
- The Center for Health and Social Development (HSD), Phnom Penh, Cambodia
| | - Neeraj Kak
- The Center for Health and Social Development (HSD), Phnom Penh, Cambodia
| | - Shunmay Yeung
- Clinical Research Department, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine (LSHTM), London, United Kingdom
- * E-mail:
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White M, Chitnis CE. Potential role of vaccines in elimination of Plasmodium vivax. Parasitol Int 2022; 90:102592. [PMID: 35489701 DOI: 10.1016/j.parint.2022.102592] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Accepted: 04/25/2022] [Indexed: 10/18/2022]
Abstract
The unique biology of Plasmodium vivax, with its ability to form latent hypnozoites in the liver stage and the early appearance of gametocytes during blood stage infection, makes it difficult to target for elimination with standard malaria control tools. Here, we use modelling studies to demonstrate that vaccines that target different stages of P. vivax could greatly assist efforts to eliminate P. vivax. Combination of vaccines that target different P. vivax life cycle stages may be required to achieve high efficacy. Our simulations demonstrate that repeated rounds of mass vaccination with multi-stage vaccines can help achieve pre-elimination levels of P. vivax in both low and high transmission settings. We review the status of global efforts to develop vaccines for P. vivax malaria. We describe the status of the leading P. vivax vaccine candidates and share some thoughts on the prospects for availability of an effective vaccine for P. vivax malaria.
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Affiliation(s)
- Michael White
- Infectious Disease Epidemiology and Analytics G5 Unit, Department of Global Health, Institut Pasteur, Université de Paris, Paris, France
| | - Chetan E Chitnis
- Malaria Parasite Biology and Vaccines Unit, Department of Parasites and Insect Vectors, Institut Pasteur, Université de Paris, Paris, France.
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Zhang C, Luo C, Yang R, Yang Y, Guo X, Deng Y, Zhou H, Zhang Y. Morphological and molecular identification reveals a high diversity of Anopheles species in the forest region of the Cambodia-Laos border. Parasit Vectors 2022; 15:94. [PMID: 35303948 PMCID: PMC8933986 DOI: 10.1186/s13071-022-05167-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Accepted: 01/17/2022] [Indexed: 11/25/2022] Open
Abstract
Background To develop an effective malaria vector intervention method in forested international border regions within the Greater Mekong Subregion (GMS), more in-depth studies should be conducted on local Anopheles species composition and bionomic features. There is a paucity of comprehensive surveys of biodiversity integrating morphological and molecular species identification conducted within the border of Laos and Cambodia. Methods A total of 2394 adult mosquitoes were trapped in the Cambodia–Laos border region. We first performed morphological identification of Anopheles mosquitoes and subsequently performed molecular identification using 412 recombinant DNA–internal transcribed spacer 2 (rDNA-ITS2) and 391 mitochondrial DNA–cytochrome c oxidase subunit 2 (mtDNA-COII) sequences. The molecular and morphological identification results were compared, and phylogenetic analysis of rDNA-ITS2 and mtDNA-COII was conducted for the sequence divergence among species. Results Thirteen distinct species of Anopheles were molecularly identified in a 26,415 km2 border region in Siem Pang (Cambodia) and Pathoomphone (Laos). According to the comparisons of morphological and molecular identity, the interpretation of local species composition for dominant species in the Cambodia–Laos border (An. dirus, An. maculatus, An. philippinensis, An. kochi and An. sinensis) achieved the highest accuracy of morphological identification, from 98.37 to 100%. In contrast, the other species which were molecularly identified were less frequently identified correctly (0–58.3%) by morphological methods. The average rDNA-ITS2 and mtDNA-COII interspecific divergence was respectively 318 times and 15 times higher than their average intraspecific divergence. The barcoding gap ranged from 0.042 to 0.193 for rDNA-ITS2, and from 0.033 to 0.047 for mtDNA-COII. Conclusions The Cambodia–Laos border hosts a high diversity of Anopheles species. The morphological identification of Anopheles species provides higher accuracy for dominant species than for other species. Molecular methods combined with morphological analysis to determine species composition, population dynamics and bionomic characteristics can facilitate a better understanding of the factors driving malaria transmission and the effects of interventions, and can aid in achieving the goal of eliminating malaria. Graphical Abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1186/s13071-022-05167-0.
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Affiliation(s)
- Canglin Zhang
- Yunnan Provincial Key Laboratory of Vector-Borne Diseases Control and Research, Yunnan Provincial Collaborative Innovation Center for Public Health and Disease Prevention and Control, Yunnan Institute of Parasitic Diseases Innovative Team of Key Techniques for Vector Borne Disease Control and Prevention (Developing), Yunnan Institute of Parasitic Diseases, Pu'er, 665099, People's Republic of China
| | - Chunhai Luo
- Yunnan Provincial Key Laboratory of Vector-Borne Diseases Control and Research, Yunnan Provincial Collaborative Innovation Center for Public Health and Disease Prevention and Control, Yunnan Institute of Parasitic Diseases Innovative Team of Key Techniques for Vector Borne Disease Control and Prevention (Developing), Yunnan Institute of Parasitic Diseases, Pu'er, 665099, People's Republic of China
| | - Rui Yang
- Yunnan Provincial Key Laboratory of Vector-Borne Diseases Control and Research, Yunnan Provincial Collaborative Innovation Center for Public Health and Disease Prevention and Control, Yunnan Institute of Parasitic Diseases Innovative Team of Key Techniques for Vector Borne Disease Control and Prevention (Developing), Yunnan Institute of Parasitic Diseases, Pu'er, 665099, People's Republic of China
| | - Yaming Yang
- Yunnan Provincial Key Laboratory of Vector-Borne Diseases Control and Research, Yunnan Provincial Collaborative Innovation Center for Public Health and Disease Prevention and Control, Yunnan Institute of Parasitic Diseases Innovative Team of Key Techniques for Vector Borne Disease Control and Prevention (Developing), Yunnan Institute of Parasitic Diseases, Pu'er, 665099, People's Republic of China
| | - Xiaofang Guo
- Yunnan Provincial Key Laboratory of Vector-Borne Diseases Control and Research, Yunnan Provincial Collaborative Innovation Center for Public Health and Disease Prevention and Control, Yunnan Institute of Parasitic Diseases Innovative Team of Key Techniques for Vector Borne Disease Control and Prevention (Developing), Yunnan Institute of Parasitic Diseases, Pu'er, 665099, People's Republic of China
| | - Yan Deng
- Yunnan Provincial Key Laboratory of Vector-Borne Diseases Control and Research, Yunnan Provincial Collaborative Innovation Center for Public Health and Disease Prevention and Control, Yunnan Institute of Parasitic Diseases Innovative Team of Key Techniques for Vector Borne Disease Control and Prevention (Developing), Yunnan Institute of Parasitic Diseases, Pu'er, 665099, People's Republic of China
| | - Hongning Zhou
- Yunnan Provincial Key Laboratory of Vector-Borne Diseases Control and Research, Yunnan Provincial Collaborative Innovation Center for Public Health and Disease Prevention and Control, Yunnan Institute of Parasitic Diseases Innovative Team of Key Techniques for Vector Borne Disease Control and Prevention (Developing), Yunnan Institute of Parasitic Diseases, Pu'er, 665099, People's Republic of China.
| | - Yilong Zhang
- Department of Tropical Diseases, Faculty of Naval Medicine, Naval Medical University, Shanghai, 200433, China.
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Zhang Y, Zhang C, Yang R, Luo C, Deng Y, Liu Y, Zhang Y, Zhou H, Zhang D. Molecular phylogeny of Anopheles nivipes based on mtDNA-COII and mosquito diversity in Cambodia-Laos border. Malar J 2022; 21:91. [PMID: 35300704 PMCID: PMC8932176 DOI: 10.1186/s12936-022-04121-w] [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: 08/24/2021] [Accepted: 03/06/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Few studies have been conducted to investigate the distribution of mosquito vectors and the population structure of secondary vectors in the border region of Cambodia-Laos. The aim of this work was to study the mosquito diversity and molecular phylogeny of secondary vectors, i.e., Anopheles nivipes in this area. METHODS 1440 adult mosquitoes were trapped in the Cambodia-Laos border. mtDNA-COII were amplified and sequenced from 53 An. nivipes DNA samples. Together with COII sequences deposited in GenBank, a total of 86 COII sequences were used for examining population variations, genetic differentiation, spatial population structure, population expansion, and gene flow patterns. RESULTS The adult mosquitoes were classified into 5 genera and 27 species in this border region. The predominant genera were Culex (60.07%, 865/1440) and Anopheles (31.25%, 450/1440), and the major Anopheles species were An. nivipes (73.56%, 331/450) and Anopheles maculatus (14.22%, 64/450). Based on sequences analysis of COII, a high level of genetic differentiation was reported in two Northwest India (Cheema and Bathinda, Punjab) and Cambodia-Laos (Siem Pang, Stung treng) populations (FST = 0.97824, 0.97343, P < 0.05), as well as lower gene flow (Nm = 0.01112, 0.01365) in the An. nivipes populations. Phylogenetic analysis and SAMOVA revealed a gene barrier restricting gene flow among three An. nivipes populations. Mantel test suggested a significant correlation between geography and gene distance in all An. nivipes populations (Z = 44,983.1865, r = 0.5575, P = 0.0070). Neutrality test and Mismatch distribution revealed a recent population expansion of An. nivipes in the Cambodia-Laos population. CONCLUSIONS Anopheles nivipes was one of the major Anopheles species in the Cambodia-Laos border. Based on sequences analysis of COII, a genetic barrier between Cambodia-Laos and two Indian populations was found, and a recent population expanding or selecting of An. nivipes occurred in the Cambodia-Laos population, suggesting that COII might be an effective marker for describing the molecular phylogeny of An. nivipes. Further investigation and continuous surveillance of An. nivipes are warranted in this region.
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Affiliation(s)
- Yilong Zhang
- Department of Tropical Diseases, Faculty of Naval Medicine, Naval Medical University, Shanghai, 200433, China
| | - Canglin Zhang
- Yunnan Institute of Parasitic Diseases, Yunnan Provincial Key Laboratory of Vector-Borne Diseases Control and Research, Yunnan Provincial Center of Malaria Research, Yunnan Provincial Collaborative Innovation Center for Public Health and Disease Prevention and Control, Yunnan Institute of Parasitic Diseases Innovative Team of Key Techniques for Vector Borne Disease Control and Prevention (Developing), Pu'er, 665099, China
| | - Rui Yang
- Yunnan Institute of Parasitic Diseases, Yunnan Provincial Key Laboratory of Vector-Borne Diseases Control and Research, Yunnan Provincial Center of Malaria Research, Yunnan Provincial Collaborative Innovation Center for Public Health and Disease Prevention and Control, Yunnan Institute of Parasitic Diseases Innovative Team of Key Techniques for Vector Borne Disease Control and Prevention (Developing), Pu'er, 665099, China
| | - Chunhai Luo
- Yunnan Institute of Parasitic Diseases, Yunnan Provincial Key Laboratory of Vector-Borne Diseases Control and Research, Yunnan Provincial Center of Malaria Research, Yunnan Provincial Collaborative Innovation Center for Public Health and Disease Prevention and Control, Yunnan Institute of Parasitic Diseases Innovative Team of Key Techniques for Vector Borne Disease Control and Prevention (Developing), Pu'er, 665099, China
| | - Yan Deng
- Yunnan Institute of Parasitic Diseases, Yunnan Provincial Key Laboratory of Vector-Borne Diseases Control and Research, Yunnan Provincial Center of Malaria Research, Yunnan Provincial Collaborative Innovation Center for Public Health and Disease Prevention and Control, Yunnan Institute of Parasitic Diseases Innovative Team of Key Techniques for Vector Borne Disease Control and Prevention (Developing), Pu'er, 665099, China
| | - Yan Liu
- Yunnan Institute of Parasitic Diseases, Yunnan Provincial Key Laboratory of Vector-Borne Diseases Control and Research, Yunnan Provincial Center of Malaria Research, Yunnan Provincial Collaborative Innovation Center for Public Health and Disease Prevention and Control, Yunnan Institute of Parasitic Diseases Innovative Team of Key Techniques for Vector Borne Disease Control and Prevention (Developing), Pu'er, 665099, China
| | - Yilong Zhang
- Department of Tropical Diseases, Faculty of Naval Medicine, Naval Medical University, Shanghai, 200433, China.
| | - Hongning Zhou
- Yunnan Institute of Parasitic Diseases, Yunnan Provincial Key Laboratory of Vector-Borne Diseases Control and Research, Yunnan Provincial Center of Malaria Research, Yunnan Provincial Collaborative Innovation Center for Public Health and Disease Prevention and Control, Yunnan Institute of Parasitic Diseases Innovative Team of Key Techniques for Vector Borne Disease Control and Prevention (Developing), Pu'er, 665099, China.
| | - Dongmei Zhang
- Department of Tropical Diseases, Faculty of Naval Medicine, Naval Medical University, Shanghai, 200433, China.
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Discovering disease-causing pathogens in resource-scarce Southeast Asia using a global metagenomic pathogen monitoring system. Proc Natl Acad Sci U S A 2022; 119:e2115285119. [PMID: 35238677 PMCID: PMC8931249 DOI: 10.1073/pnas.2115285119] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
SignificanceMetagenomic pathogen sequencing offers an unbiased approach to characterizing febrile illness. In resource-scarce settings with high biodiversity, it is critical to identify disease-causing pathogens in order to understand burden and to prioritize efforts for control. Here, metagenomic next-generation sequencing (mNGS) characterization of the pathogen landscape in Cambodia revealed diverse vector-borne and zoonotic pathogens irrespective of age and gender as risk factors. Identification of key pathogens led to changes in national program surveillance. This study is a "real world" example of the use of mNGS surveillance of febrile individuals, executed in-country, to identify outbreaks of vector-borne, zoonotic, and other emerging pathogens in a resource-scarce setting.
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10
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Nekkab N, Lana R, Lacerda M, Obadia T, Siqueira A, Monteiro W, Villela D, Mueller I, White M. Estimated impact of tafenoquine for Plasmodium vivax control and elimination in Brazil: A modelling study. PLoS Med 2021; 18:e1003535. [PMID: 33891582 PMCID: PMC8064585 DOI: 10.1371/journal.pmed.1003535] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Accepted: 01/06/2021] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Despite recent intensification of control measures, Plasmodium vivax poses a major challenge for malaria elimination efforts. Liver-stage hypnozoite parasites that cause relapsing infections can be cleared with primaquine; however, poor treatment adherence undermines drug effectiveness. Tafenoquine, a new single-dose treatment, offers an alternative option for preventing relapses and reducing transmission. In 2018, over 237,000 cases of malaria were reported to the Brazilian health system, of which 91.5% were due to P. vivax. METHODS AND FINDINGS We evaluated the impact of introducing tafenoquine into case management practices on population-level transmission dynamics using a mathematical model of P. vivax transmission. The model was calibrated to reflect the transmission dynamics of P. vivax endemic settings in Brazil in 2018, informed by nationwide malaria case reporting data. Parameters for treatment pathways with chloroquine, primaquine, and tafenoquine with glucose-6-phosphate dehydrogenase deficiency (G6PDd) testing were informed by clinical trial data and the literature. We assumed 71.3% efficacy for primaquine and tafenoquine, a 66.7% adherence rate to the 7-day primaquine regimen, a mean 5.5% G6PDd prevalence, and 8.1% low metaboliser prevalence. The introduction of tafenoquine is predicted to improve effective hypnozoite clearance among P. vivax cases and reduce population-level transmission over time, with heterogeneous levels of impact across different transmission settings. According to the model, while achieving elimination in only few settings in Brazil, tafenoquine rollout in 2021 is estimated to improve the mean effective radical cure rate from 42% (95% uncertainty interval [UI] 41%-44%) to 62% (95% UI 54%-68%) among clinical cases, leading to a predicted 38% (95% UI 7%-99%) reduction in transmission and over 214,000 cumulative averted cases between 2021 and 2025. Higher impact is predicted in settings with low transmission, low pre-existing primaquine adherence, and a high proportion of cases in working-aged males. High-transmission settings with a high proportion of cases in children would benefit from a safe high-efficacy tafenoquine dose for children. Our methodological limitations include not accounting for the role of imported cases from outside the transmission setting, relying on reported clinical cases as a measurement of community-level transmission, and implementing treatment efficacy as a binary condition. CONCLUSIONS In our modelling study, we predicted that, provided there is concurrent rollout of G6PDd diagnostics, tafenoquine has the potential to reduce P. vivax transmission by improving effective radical cure through increased adherence and increased protection from new infections. While tafenoquine alone may not be sufficient for P. vivax elimination, its introduction will improve case management, prevent a substantial number of cases, and bring countries closer to achieving malaria elimination goals.
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Affiliation(s)
- Narimane Nekkab
- Malaria: Parasites and Hosts, Department of Parasites and Insect Vectors, Institut Pasteur, Paris, France
| | - Raquel Lana
- Programa de Computação Científica, Fundação Oswaldo Cruz, Rio de Janeiro, Brazil
| | - Marcus Lacerda
- Diretoria de Ensino e Pesquisa, Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Brazil
- Instituto Leônidas e Maria Deane, Fundação Oswaldo Cruz, Manaus, Brazil
| | - Thomas Obadia
- Malaria: Parasites and Hosts, Department of Parasites and Insect Vectors, Institut Pasteur, Paris, France
| | - André Siqueira
- Instituto Nacional de Infectologia Evandro Chagas, Fundação Oswaldo Cruz, Rio de Janeiro, Brazil
| | - Wuelton Monteiro
- Diretoria de Ensino e Pesquisa, Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Brazil
- School of Health Sciences, Universidade do Estado do Amazonas, Manaus, Brazil
| | - Daniel Villela
- Programa de Computação Científica, Fundação Oswaldo Cruz, Rio de Janeiro, Brazil
| | - Ivo Mueller
- Malaria: Parasites and Hosts, Department of Parasites and Insect Vectors, Institut Pasteur, Paris, France
- Population Health & Immunity Division, Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, Australia
- Department of Medical Biology, University of Melbourne, Melbourne, Victoria, Australia
| | - Michael White
- Malaria: Parasites and Hosts, Department of Parasites and Insect Vectors, Institut Pasteur, Paris, France
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11
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Stratil AS, Vernaeve L, Lopes S, Bourny Y, Mannion K, Hamade P, Roca-Feltrer A, Tibenderana JK, Sovannaroth S, Debackere M. Eliminating Plasmodium falciparum malaria: results from tailoring active case detection approaches to remote populations in forested border areas in north-eastern Cambodia. Malar J 2021; 20:108. [PMID: 33618718 PMCID: PMC7898252 DOI: 10.1186/s12936-021-03622-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Accepted: 02/04/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Remaining Plasmodium falciparum cases in Cambodia are concentrated in forested border areas and in remote populations who are hard to reach through passive case detection. A key approach to reach these populations is active case detection by mobile malaria workers (MMWs). However, this is operationally challenging because of changing movement patterns of the target population moving into less accessible areas. From January 2018 to December 2020, a tailored package of active case detection approaches was implemented in forested border areas of three provinces in north-eastern Cambodia to reach remote populations and support the elimination of falciparum malaria. METHODS Key elements of this project were to tailor approaches to local populations, use responsive monitoring systems, maintain operational flexibility, build strong relationships with local communities, and implement close supervision practices. MMWs were recruited from local communities. Proactive case detection approaches included mobile malaria posts positioned at frequented locations around and within forests, and locally informed outreach activities targeting more remote locations. Reactive case detection was conducted among co-travellers of confirmed cases. Testing for malaria was conducted independent of fever symptoms. Routine monitoring of programmatic data informed tactical adaptations, while supervision exercises ensured service quality. RESULTS Despite operational challenges, service delivery sites were able to maintain consistently high testing rates throughout the implementation period, with each of 45 sites testing a monthly average of 64 (SD 6) people in 2020. In 2020, project MMWs detected only 32 P. falciparum cases. Over the project period, the P. falciparum/P. vivax ratio steadily inversed. Including data from neighbouring health centres and village malaria workers, 45% (80,988/180,732) of all people tested and 39% (1280/3243) of P. falciparum cases detected in the area can be attributed to project MMWs. Remaining challenges of the last elimination phase include maintaining intensified elimination efforts, addressing the issue of detecting low parasitaemia cases and shifting focus to P. vivax malaria. CONCLUSIONS Reaching remote populations through active case detection should remain a key strategy to eliminate P. falciparum malaria. This case study presented a successful approach combining tailored proactive and reactive strategies that could be transferred to similar settings in other areas of the Greater Mekong Subregion.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Siv Sovannaroth
- National Center for Parasitology, Entomology and Malaria Control (CNM), Phnom Penh, Cambodia
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12
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Malaria in Cambodia: A Retrospective Analysis of a Changing Epidemiology 2006-2019. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2021; 18:ijerph18041960. [PMID: 33670471 PMCID: PMC7922556 DOI: 10.3390/ijerph18041960] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 01/22/2021] [Accepted: 02/12/2021] [Indexed: 11/17/2022]
Abstract
Background: In Cambodia, malaria persists with changing epidemiology and resistance to antimalarials. This study aimed to describe how malaria has evolved spatially from 2006 to 2019 in Cambodia. Methods: We undertook a secondary analysis of existing malaria data from all government healthcare facilities in Cambodia. The epidemiology of malaria was described by sex, age, seasonality, and species. Spatial clusters at the district level were identified with a Poisson model. Results: Overall, incidence decreased from 7.4 cases/1000 population in 2006 to 1.9 in 2019. The decrease has been drastic for females, from 6.7 to 0.6/1000. Adults aged 15–49 years had the highest malaria incidence among all age groups. The proportion of Plasmodium (P.) falciparum + Mixed among confirmed cases declined from 87.9% (n = 67,489) in 2006 to 16.6% (n = 5290) in 2019. Clusters of P. falciparum + Mixed and P. vivax + Mixed were detected in forested provinces along all national borders. Conclusions: There has been a noted decrease in P. falciparum cases in 2019, suggesting that an intensification plan should be maintained. A decline in P. vivax cases was also noted, although less pronounced. Interventions aimed at preventing new infections of P. vivax and relapses should be prioritized. All detected malaria cases should be captured by the national surveillance system to avoid misleading trends.
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13
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Spring MD, Lon C, Sok S, Sea D, Wojnarski M, Chann S, Kuntawunginn W, Kheang Heng T, Nou S, Arsanok M, Sriwichai S, Vanachayangkul P, Lin JT, Manning JE, Jongsakul K, Pichyangkul S, Satharath P, Smith PL, Dysoley L, Saunders DL, Waters NC. Prevalence of CYP2D6 Genotypes and Predicted Phenotypes in a Cohort of Cambodians at High Risk for Infections with Plasmodium vivax. Am J Trop Med Hyg 2020; 103:756-759. [PMID: 32394887 PMCID: PMC7410472 DOI: 10.4269/ajtmh.20-0061] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Clinical failure of primaquine (PQ) has been demonstrated in people with CYP450 2D6 genetic polymorphisms that result in reduced or no enzyme activity. The distribution of CYP2D6 genotypes and predicted phenotypes in the Cambodian population is not well described. Surveys in other Asian countries have shown an approximate 50% prevalence of the reduced activity CYP2D6 allele *10, which could translate into increased risk of PQ radical cure failure and repeated relapses, making interruption of transmission and malaria elimination difficult to achieve. We determined CYP2D6 genotypes from 96 volunteers from Oddor Meanchey Province, Cambodia, an area endemic for Plasmodium vivax. We found a 54.2% frequency of the *10 allele, but in approximately half of our subjects, it was paired with a normal activity allele, either *1 or *2. The prevalence of *5, a null allele, was 9.4%. Overall predicted phenotype percentages were normal metabolizers, 46%; intermediate metabolizers, 52%; and poor metabolizers, 1%.
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Affiliation(s)
- Michele D Spring
- US Army Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand.,The Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc., Bethesda, Maryland
| | - Chanthap Lon
- US Army Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Somethy Sok
- US Army Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Darapiseth Sea
- US Army Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Mariusz Wojnarski
- US Army Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Soklyda Chann
- US Army Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | | | - Thay Kheang Heng
- US Army Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Samon Nou
- US Army Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Montri Arsanok
- US Army Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Sabaithip Sriwichai
- US Army Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | | | - Jessica T Lin
- University of North Carolina-Chapel Hill, Chapel Hill, North Carolina
| | - Jessica E Manning
- US National Institute of Allergy and Infectious Diseases, National Institutes of Health, Phnom Penh, Cambodia
| | - Krisada Jongsakul
- US Army Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Sathit Pichyangkul
- US Army Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | | | - Philip L Smith
- Walter Reed Army Institute of Research, Silver Spring, Maryland
| | - Lek Dysoley
- National Malaria Program of Cambodia, Phnom Penh, Cambodia
| | - David L Saunders
- U.S. Army Medical Research Institute of Infectious Diseases, Ft. Detrick, Maryland
| | - Norman C Waters
- US Army Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
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14
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Wojnarski B, Lon C, Sea D, Sok S, Sriwichai S, Chann S, Hom S, Boonchan T, Ly S, Sok C, Nou S, Oung P, Kong N, Pheap V, Thay K, Dao V, Kuntawunginn W, Feldman M, Gosi P, Buathong N, Ittiverakul M, Uthaimongkol N, Huy R, Spring M, Lek D, Smith P, Fukuda MM, Wojnarski M. Evaluation of the CareStart™ glucose-6-phosphate dehydrogenase (G6PD) rapid diagnostic test in the field settings and assessment of perceived risk from primaquine at the community level in Cambodia. PLoS One 2020; 15:e0228207. [PMID: 32004348 PMCID: PMC6994100 DOI: 10.1371/journal.pone.0228207] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2019] [Accepted: 01/10/2020] [Indexed: 11/19/2022] Open
Abstract
Background Primaquine is an approved radical cure treatment for Plasmodium vivax malaria but treatment can result in life-threatening hemolysis if given to a glucose-6-phosphate dehydrogenase deficient (G6PDd) patient. There is a need for reliable point-of-care G6PD diagnostic tests. Objectives To evaluate the performance of the CareStart™ rapid diagnostic test (RDT) in the hands of healthcare workers (HCWs) and village malaria workers (VMWs) in field settings, and to better understand user perceptions about the risks and benefits of PQ treatment guided by RDT results. Methods This study enrolled 105 HCWs and VMWs, herein referred to as trainees, who tested 1,543 healthy adult male volunteers from 84 villages in Cambodia. The trainees were instructed on G6PD screening, primaquine case management, and completed pre and post-training questionnaires. Each trainee tested up to 16 volunteers in the field under observation by the study staff. Results Out of 1,542 evaluable G6PD volunteers, 251 (16.28%) had quantitative enzymatic activity less than 30% of an adjusted male median (8.30 U/g Hb). There was no significant difference in test sensitivity in detecting G6PDd between trainees (97.21%), expert study staff in the field (98.01%), and in a laboratory setting (95.62%) (p = 0.229); however, test specificity was different for trainees (96.62%), expert study staff in the field (98.14%), and experts in the laboratory (98.99%) (p < 0.001). Negative predictive values were not statistically different for trainees, expert staff, and laboratory testing: 99.44%, 99.61%, and 99.15%, respectively. Knowledge scores increased significantly post-training, with 98.7% willing to prescribe primaquine for P.vivax malaria, an improvement from 40.6% pre-training (p < 0.001). Conclusion This study demonstrated ability of medical staff with different background to accurately use CareStart™ RDT to identify G6PDd in male patients, which may enable safer prescribing of primaquine; however, pharmacovigilance is required to address possible G6PDd misclassifications.
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Affiliation(s)
- Bertha Wojnarski
- Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
- The George Washington University, School of Nursing, Washington, DC, United States of America
| | - Chanthap Lon
- Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Darapiseth Sea
- Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Somethy Sok
- Ministry of National Defense, Department of Health, Phnom Penh, Cambodia
| | | | | | - Sohei Hom
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | | | - Sokna Ly
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Chandara Sok
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Samon Nou
- Chenda Polyclinic (CPC), Phnom Penh, Cambodia
| | - Pheaktra Oung
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Nareth Kong
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Vannak Pheap
- Ministry of National Defense, Department of Health, Phnom Penh, Cambodia
| | - Khengheang Thay
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Vy Dao
- Ministry of National Defense, Department of Health, Phnom Penh, Cambodia
| | | | - Mitra Feldman
- Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Panita Gosi
- Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Nillawan Buathong
- Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Mali Ittiverakul
- Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | | | - Rekol Huy
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Michele Spring
- Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Dysoley Lek
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
- School of Public Health, National Institute of Public Health, Phnom Penh, Cambodia
| | - Philip Smith
- Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Mark M. Fukuda
- Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Mariusz Wojnarski
- Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
- * E-mail:
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15
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Mercado CEG, Lawpoolsri S, Sudathip P, Kaewkungwal J, Khamsiriwatchara A, Pan-Ngum W, Yimsamran S, Lawawirojwong S, Ho K, Ekapirat N, Maude RR, Wiladphaingern J, Carrara VI, Day NPJ, Dondorp AM, Maude RJ. Spatiotemporal epidemiology, environmental correlates, and demography of malaria in Tak Province, Thailand (2012-2015). Malar J 2019; 18:240. [PMID: 31311606 PMCID: PMC6636027 DOI: 10.1186/s12936-019-2871-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Accepted: 07/06/2019] [Indexed: 12/14/2022] Open
Abstract
Background Tak Province, at the Thai–Myanmar border, is one of three high malaria incidence areas in Thailand. This study aimed to describe and identify possible factors driving the spatiotemporal trends of disease incidence from 2012 to 2015. Methods Climate variables and forest cover were correlated with malaria incidence using Pearson’s r. Statistically significant clusters of high (hot spots) and low (cold spots) annual parasite incidence per 1000 population (API) were identified using Getis-Ord Gi* statistic. Results The total number of confirmed cases declined by 76% from 2012 to 2015 (Plasmodium falciparum by 81%, Plasmodium vivax by 73%). Incidence was highly seasonal with two main annual peaks. Most cases were male (62.75%), ≥ 15 years (56.07%), and of Myanmar (56.64%) or Thai (39.25%) nationality. Median temperature (1- and 2-month lags), average temperature (1- and 2-month lags) and average relative humidity (2- and 3-month lags) correlated positively with monthly total, P. falciparum and P. vivax API. Total rainfall in the same month correlated with API for total cases and P. vivax but not P. falciparum. At sub-district level, percentage forest cover had a low positive correlation with P. falciparum, P. vivax, and total API in most years. There was a decrease in API in most sub-districts for both P. falciparum and P. vivax. Sub-districts with the highest API were in the Tha Song Yang and Umphang Districts along the Thai–Myanmar border. Annual hot spots were mostly in the extreme north and south of the province. Conclusions There has been a large decline in reported clinical malaria from 2012 to 2015 in Tak Province. API was correlated with monthly climate and annual forest cover but these did not account for the trends over time. Ongoing elimination interventions on one or both sides of the border are more likely to have been the cause but it was not possible to assess this due to a lack of suitable data. Two main hot spot areas were identified that could be targeted for intensified elimination activities. Electronic supplementary material The online version of this article (10.1186/s12936-019-2871-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Chris Erwin G Mercado
- Mahidol Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand. .,Department of Tropical Hygiene, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
| | - Saranath Lawpoolsri
- Department of Tropical Hygiene, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Center of Excellence for Biomedical and Public Health Informatics (BIOPHICS), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Prayuth Sudathip
- Bureau of Vector-borne Diseases (BVBD), Department of Disease Control (DDC), Ministry of Public Health (MOPH), Nonthaburi, Thailand
| | - Jaranit Kaewkungwal
- Department of Tropical Hygiene, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Center of Excellence for Biomedical and Public Health Informatics (BIOPHICS), 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
| | - Wirichada Pan-Ngum
- Mahidol Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Department of Tropical Hygiene, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Surapon Yimsamran
- Department of Tropical Hygiene, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Siam Lawawirojwong
- Geo-Informatics and Space Technology Development Agency (GISTDA), Bangkok, Thailand
| | - Kevin Ho
- Mahidol Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Nattwut Ekapirat
- Mahidol Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Rapeephan R Maude
- Mahidol Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Jacher Wiladphaingern
- Mahidol Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Shoklo Malaria Research Unit (SMRU), Faculty of Tropical Medicine, Mahidol University, Mae Sot, Tak, Thailand
| | - Verena I Carrara
- Mahidol Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Shoklo Malaria Research Unit (SMRU), Faculty of Tropical Medicine, Mahidol University, Mae Sot, Tak, Thailand
| | - Nicholas P J Day
- Mahidol Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Arjen M Dondorp
- Mahidol Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Richard J Maude
- Mahidol Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK.,Department of Epidemiology, Harvard T.H. Chan School of Public Health, Harvard University, Boston, USA
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16
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Popovici J, Vantaux A, Primault L, Samreth R, Piv EP, Bin S, Kim S, Lek D, Serre D, Menard D. Therapeutic and Transmission-Blocking
Efficacy of Dihydroartemisinin/Piperaquine and Chloroquine against Plasmodium vivax Malaria, Cambodia. Emerg Infect Dis 2018; 24:1516-1519. [PMID: 29798745 PMCID: PMC6056113 DOI: 10.3201/eid2408.170768] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
We assessed the efficacy of standard 3-day courses of chloroquine and dihydroartemisinin/piperaquine against Plasmodium vivax malaria. Compared with chloroquine, dihydroartemisinin/piperaquine was faster in clearing asexual P. vivax parasites and blocking human-to-mosquito transmission. This drug combination was also more effective in preventing potential recurrences for >2 months.
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17
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Kitchakarn S, Lek D, Thol S, Hok C, Saejeng A, Huy R, Chinanonwait N, Thimasarn K, Wongsrichanalai C. Implementation of G6PD testing and primaquine for P. vivax radical cure: Operational perspectives from Thailand and Cambodia. WHO South East Asia J Public Health 2018; 6:60-68. [PMID: 28857064 DOI: 10.4103/2224-3151.213793] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Following progressive success in reducing the burden of malaria over the past two decades, countries of the Asia Pacific are now aiming for elimination of malaria by 2030. Plasmodium falciparum and Plasmodium vivax are the two main malaria species that are endemic in the region. P. vivax is generally perceived to be less severe but will be harder to eliminate, owing partly to its dormant liver stage (known as a hypnozoite) that can cause multiple relapses following an initial clinical episode caused by a mosquito-borne infection. Primaquine is the only anti-hypnozoite drug against P. vivax relapse currently available, with tafenoquine in the pipeline. However, both drugs may cause severe haemolysis in individuals with deficiency of the enzyme glucose-6-phosphate dehydrogenase (G6PD), a hereditary defect. The overall incidence of malaria has significantly declined in both Thailand and Cambodia over the last 15 years. However, P. vivax has replaced P. falciparum as the dominant species in large parts of both countries. This paper presents the experience of the national malaria control programmes of the two countries, in their efforts to implement safe primaquine therapy for the radical cure, i.e. relapse prevention, of P. vivax malaria by introducing a rapid, point-of-care test to screen for G6PD deficiency.
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Affiliation(s)
- Suravadee Kitchakarn
- Bureau of Vector Borne Diseases, Ministry of Public Health, Nonthaburi, Thailand
| | - Dysoley Lek
- National Centre for Parasitology, Entomology and Malaria Control; School of Public Health, National Institute of Public Health, Phnom Penh, Cambodia, Thailand
| | - Sea Thol
- Cambodian Pharmacovigilance Centre, Department of Drugs and Food, Ministry of Health, Phnom Penh, Cambodia
| | - Chantheasy Hok
- National Centre for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Aungkana Saejeng
- Office of Disease Prevention and Control No. 10, Chiang Mai, Thailand
| | - Rekol Huy
- National Centre for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Nipon Chinanonwait
- Bureau of Vector Borne Diseases, Ministry of Public Health, Nonthaburi, Thailand
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18
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Genomic Analyses Reveal the Common Occurrence and Complexity of Plasmodium vivax Relapses in Cambodia. mBio 2018; 9:mBio.01888-17. [PMID: 29362233 PMCID: PMC5784252 DOI: 10.1128/mbio.01888-17] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Plasmodium vivax parasites have a unique dormant stage that can cause relapses weeks or months after the initial infection. These dormant parasites are among the main challenges of vivax malaria control as they constitute a reservoir that is difficult to eliminate. Since field studies are confounded by reinfections and possible recrudescence of drug-resistant parasites, most analyses of P. vivax relapses have focused on travelers returning from regions of malaria endemicity. However, it is not clear whether these individuals accurately recapitulate the relapse patterns of repeatedly infected individuals residing in areas of endemicity. Here, we present analyses of vivax malaria patients enrolled in a tightly controlled field study in Cambodia. After antimalarial drug treatment was administered, we relocated 20 individuals to a nontransmission area and followed them for 60 days, with blood collection performed every second day. Our analyses reveal that 60% of the patients relapsed during the monitoring period. Using whole-genome sequencing and high-throughput genotyping, we showed that relapses in Cambodia are often polyclonal and that the relapsing parasites harbor various degrees of relatedness to the parasites present in the initial infection. Our analyses also showed that clone populations differed dynamically, with new clones emerging during the course of the relapsing infections. Overall, our study data show that it is possible to investigate the patterns, dynamics, and diversity of P. vivax relapses of individuals living in a region of malaria endemicity and reveal that P. vivax relapses are much more pervasive and complex than previously considered. (This study has been registered at ClinicalTrials.gov under registration no. NCT02118090)IMPORTANCEP. vivax parasites can remain dormant in the liver and relapse weeks or months after the initial infection, greatly complicating malaria control and elimination efforts. The few investigations of this dormant stage have relied on travelers and military personnel returning from areas of malaria endemicity. However, it is not clear whether these individuals, exposed to a limited number of infections, accurately represent the patterns of relapses of individuals living in areas of endemicity, who are repeatedly infected by P. vivax parasites. Our study combined tightly controlled fieldwork with comprehensive genomic analyses, and our report provides a first opportunity to investigate the patterns, dynamics, and diversity of P. vivax relapses directly with individuals living in areas of endemicity.
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19
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Heng S, Durnez L, Mao S, Siv S, Tho S, Mean V, Sluydts V, Coosemans M. Passive case detection of malaria in Ratanakiri Province (Cambodia) to detect villages at higher risk for malaria. Malar J 2017; 16:104. [PMID: 28264678 PMCID: PMC5340042 DOI: 10.1186/s12936-017-1758-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Accepted: 02/28/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Cambodia reduced malaria incidence by more than 75% between 2000 and 2015, a target of the Millennium Development Goal 6. The Cambodian Government aims to eliminate all forms of malaria by 2025. The country's malaria incidence is highly variable at provincial level, but less is known at village level. This study used passive case detection (PCD) data at village level in Ratanakiri Province from 2010 to 2014 to describe incidence trends and identify high-risk areas of malaria to be primarily targeted towards malaria elimination. METHODS In 2010, the Cambodian malaria programme created a Malaria Information System (MIS) to capture malaria information at village level through PCD by village malaria workers and health facilities. The MIS data of Ratanakiri Province 2010-2014 were used to calculate annual incidence rates by Plasmodium species at province and commune levels. For estimating the trend at provincial level only villages reporting each year were selected. The communal incidences and the number of cases per village were visualized on a map per Plasmodium species and per year. Analysis of spatial clustering of village malaria cases by Plasmodium species was performed by year. RESULTS Overall, malaria annual incidence rates per 1000 inhabitants decreased from 86 (2010) to 30 (2014). Falciparum incidence decreased (by 79% in 2014 compared to 2010; CI 95% 76-82%) more rapidly than vivax incidence (by 19% in 2014 compared to 2010; CI 95% 5-32%). There were ten to 16 significant spatial clusters each year. Big clusters tended to extend along the Cambodian-Vietnamese border and along the Sesan River. Three clusters appeared throughout all years (2010-2014): one with 21 villages appeared each year, the second shrunk progressively from 2012 to 2014 and the third was split into two smaller clusters in 2013 and 2014. CONCLUSION The decline of malaria burden can be attributed to intensive malaria control activities implemented in the areas: distribution of a long-lasting insecticidal net per person and early diagnosis and prompt treatment. Dihydro-artemisinin piperaquine was the only first-line treatment for all malaria cases. No radical treatment with primaquine was provided for Plasmodium vivax cases, which could explain the slow decrease of P. vivax due to relapses. To achieve malaria elimination by 2025, priority should be given to the control of stable malaria clusters appearing over time.
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Affiliation(s)
- Somony Heng
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia. .,Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium. .,Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium.
| | - Lies Durnez
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Sokny Mao
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Sovannaroth Siv
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Sochantha Tho
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Vanna Mean
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Vincent Sluydts
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium.,Department of Biology, University of Antwerp, Antwerp, Belgium
| | - Marc Coosemans
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium.,Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium
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