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Chaumeau V, Piarroux M, Kulabkeeree T, Sawasdichai S, Inta A, Watthanaworawit W, Nosten F, Piarroux R, Nabet C. Identification of Southeast Asian Anopheles mosquito species using MALDI-TOF mass spectrometry. PLoS One 2024; 19:e0305167. [PMID: 38968228 PMCID: PMC11226003 DOI: 10.1371/journal.pone.0305167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2024] [Accepted: 05/24/2024] [Indexed: 07/07/2024] Open
Abstract
Malaria elimination in Southeast Asia remains a challenge, underscoring the importance of accurately identifying malaria mosquitoes to understand transmission dynamics and improve vector control. Traditional methods such as morphological identification require extensive training and cannot distinguish between sibling species, while molecular approaches are costly for extensive screening. Matrix-assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI-TOF MS) has emerged as a rapid and cost-effective tool for Anopheles species identification, yet its current use is limited to few specialized laboratories. This study aimed to develop and validate an online reference database for MALDI-TOF MS identification of Southeast Asian Anopheles species. The database, constructed using the in-house data analysis pipeline MSI2 (Sorbonne University), comprised 2046 head mass spectra from 209 specimens collected at the Thailand-Myanmar border. Molecular identification via COI and ITS2 DNA barcodes enabled the identification of 20 sensu stricto species and 5 sibling species complexes. The high quality of the mass spectra was demonstrated by a MSI2 median score (min-max) of 61.62 (15.94-77.55) for correct answers, using the best result of four technical replicates of a test panel. Applying an identification threshold of 45, 93.9% (201/214) of the specimens were identified, with 98.5% (198/201) consistency with the molecular taxonomic assignment. In conclusion, MALDI-TOF MS holds promise for malaria mosquito identification and can be scaled up for entomological surveillance in Southeast Asia. The free online sharing of our database on the MSI2 platform (https://msi.happy-dev.fr/) represents an important step towards the broader use of MALDI-TOF MS in malaria vector surveillance.
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Affiliation(s)
- Victor Chaumeau
- Faculty of Tropical Medicine, Shoklo Malaria Research Unit, Mahidol-Oxford Research Unit, Mahidol University, Mae Ramat, Thailand
- Nuffield Department of Medicine, Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, United Kingdom
| | - Martine Piarroux
- Institut Pierre-Louis d’Epidémiologie et de Santé Publique, Inserm, IPLESP, AP-HP, Groupe Hospitalier Pitié-Salpêtrière, Service de Parasitologie-Mycologie, Sorbonne Université, Paris, France
| | - Thithiworada Kulabkeeree
- Faculty of Tropical Medicine, Shoklo Malaria Research Unit, Mahidol-Oxford Research Unit, Mahidol University, Mae Ramat, Thailand
| | - Sunisa Sawasdichai
- Faculty of Tropical Medicine, Shoklo Malaria Research Unit, Mahidol-Oxford Research Unit, Mahidol University, Mae Ramat, Thailand
| | - Aritsara Inta
- Faculty of Tropical Medicine, Shoklo Malaria Research Unit, Mahidol-Oxford Research Unit, Mahidol University, Mae Ramat, Thailand
| | - Wanitda Watthanaworawit
- Faculty of Tropical Medicine, Shoklo Malaria Research Unit, Mahidol-Oxford Research Unit, Mahidol University, Mae Ramat, Thailand
| | - François Nosten
- Faculty of Tropical Medicine, Shoklo Malaria Research Unit, Mahidol-Oxford Research Unit, Mahidol University, Mae Ramat, Thailand
- Nuffield Department of Medicine, Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, United Kingdom
| | - Renaud Piarroux
- Institut Pierre-Louis d’Epidémiologie et de Santé Publique, Inserm, IPLESP, AP-HP, Groupe Hospitalier Pitié-Salpêtrière, Service de Parasitologie-Mycologie, Sorbonne Université, Paris, France
| | - Cécile Nabet
- Institut Pierre-Louis d’Epidémiologie et de Santé Publique, Inserm, IPLESP, AP-HP, Groupe Hospitalier Pitié-Salpêtrière, Service de Parasitologie-Mycologie, Sorbonne Université, Paris, France
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Sawasdichai S, Chaumeau V, Kearney E, Wasisakun P, Simpson JA, Price DJ, Chotirat S, Rénia L, Bergmann-Leitner E, Fowkes F, Nosten F. Characterizing antibody responses to mosquito salivary antigens of the Southeast Asian vectors of malaria and dengue with a human challenge model of controlled exposure: a protocol. Wellcome Open Res 2023; 8:135. [PMID: 37456919 PMCID: PMC10338987 DOI: 10.12688/wellcomeopenres.19049.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/28/2023] [Indexed: 07/18/2023] Open
Abstract
Background: Measurement of antibody titers directed against mosquito salivary antigens in blood samples has been proposed as an outcome measure to assess human exposure to vector bites. However, only a handful of antigens have been identified and the specificity and longitudinal dynamics of antibody responses are not well known. We report the protocol of a clinical trial of controlled exposure to mosquito bites that aims to identify and validate biomarkers of exposure to bites of mosquito vector species that transmit malaria and dengue in Southeast Asia and some other parts of the world. Methods: This study is an exploratory factorial randomized control trial of controlled exposure to mosquito bites with 10 arms corresponding to different species ( Aedes aegypti, Ae. albopictus, Anopheles dirus, An. maculatus and An. minimus) and numbers of bites (35 or 305 bites in total over 6 weeks). Blood samples will be collected from study participants before, during and after mosquito biting challenges. Candidate peptides will be identified from published literature with antigen prediction algorithms using mosquito DNA sequence data and with immunoblotting assays carried out using protein extracts of dissected mosquito salivary glands and participants samples. Antibody titers against candidate peptides will be determined in participants samples with high-throughput cutting-edge immuno-assays. Quantification of the antibody response profile over time (including an estimate of the decay rate) and the effect of the number of bites on the antibody response will be determined using linear and logistic mixed-effects models for the continuous and the binary response, respectively. Conclusion: This research is expected to generate important knowledge for vector sero-surveillance and evaluation of vector-control interventions against malaria and dengue in the Greater Mekong Subregion. Registration: This study is registered with clinicaltrials.gov (NCT04478370) on July 20 th, 2020.
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Affiliation(s)
- Sunisa Sawasdichai
- Shoklo Malaria Research Unit, Mahidol-Oxford Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Ramat, Tak, 63140, Thailand
| | - Victor Chaumeau
- Shoklo Malaria Research Unit, Mahidol-Oxford Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Ramat, Tak, 63140, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, England, OX3 7BN, UK
| | - Ellen Kearney
- Burnet Institute, Melbourne, VIC 3004, Australia
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Victoria, VIC 3010, Australia
| | - Praphan Wasisakun
- Shoklo Malaria Research Unit, Mahidol-Oxford Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Ramat, Tak, 63140, Thailand
| | - Julie A. Simpson
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Victoria, VIC 3010, Australia
| | - David J. Price
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Victoria, VIC 3010, Australia
- Department of Infectious Diseases, University of Melbourne, at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, VIC 3000, Australia
| | - Sadudee Chotirat
- Malaria Vivax Research Unit, Faculty of Tropical medicine, Mahidol University, Bangkok, 10400, Thailand
| | - Laurent Rénia
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore
- A*STAR Infectious Diseases Labs, Agency for Science, Technology, and Research, Singapore, 138648, Singapore
| | | | - Freya Fowkes
- Burnet Institute, Melbourne, VIC 3004, Australia
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Victoria, VIC 3010, Australia
- Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Victoria, VIC 3052, Australia
| | - François Nosten
- Shoklo Malaria Research Unit, Mahidol-Oxford Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Ramat, Tak, 63140, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, England, OX3 7BN, UK
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Sawasdichai S, Chaumeau V, Kearney E, Wasisakun P, Simpson JA, Price DJ, Chotirat S, Rénia L, Bergmann-Leitner E, Fowkes F, Nosten F. Characterizing antibody responses to mosquito salivary antigens of the Southeast Asian vectors of malaria and dengue with a human challenge model of controlled exposure: a protocol. Wellcome Open Res 2023. [DOI: 10.12688/wellcomeopenres.19049.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/29/2023] Open
Abstract
Background: Measurement of antibody titers directed against mosquito salivary antigens in blood samples has been proposed as an outcome measure to assess human exposure to vector bites. However, only a handful of antigens have been identified and the specificity and longitudinal dynamics of antibody responses are not well known. We report the protocol of a clinical trial of controlled exposure to mosquito bites that aims to identify and validate biomarkers of exposure to bites of mosquito vector species that transmit malaria and dengue in Southeast Asia and some other parts of the world. Methods: This study is an exploratory factorial randomized control trial of controlled exposure to mosquito bites with 10 arms corresponding to different species (Aedes aegypt, Ae. albopictus, Anopheles dirus, An. maculatus and An. minimus) and numbers of bites (35 or 305 bites in total over 6 weeks). Blood samples will be collected from study participants before, during and after mosquito biting challenges. Candidate peptides will be identified from published literature with antigen prediction algorithms using mosquito DNA sequence data and with immunoblotting assays carried out using protein extracts of dissected mosquito salivary glands and participants samples. Antibody titers against candidate peptides will be determined in participants samples with high-throughput cutting-edge immuno-assays. Quantification of the antibody response profile over time (including an estimate of the decay rate) and the effect of the number of bites on the antibody response will be determined using linear and logistic mixed-effects models for the continuous and the binary response, respectively. Conclusion: This research is expected to generate important knowledge for vector sero-surveillance and evaluation of vector-control interventions against malaria and dengue in the Greater Mekong Subregion. Registration: This study is registered with clinicaltrials.gov (NCT04478370) on July 20th, 2020.
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Chaumeau V, Kajeechiwa L, Kulabkeeree T, Sawasdichai S, Haohankhunnatham W, Inta A, Phanaphadungtham M, Girond F, Herbreteau V, Delmas G, Nosten F. Outdoor residual spraying for malaria vector-control in Kayin (Karen) state, Myanmar: A cluster randomized controlled trial. PLoS One 2022; 17:e0274320. [PMID: 36083983 PMCID: PMC9462579 DOI: 10.1371/journal.pone.0274320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 08/26/2022] [Indexed: 11/19/2022] Open
Abstract
Outdoor and early biting by mosquitoes challenge the efficacy of bed nets and indoor residual spraying against malaria in the Greater Mekong Subregion. The objective of this study was to assess the efficacy of outdoor residual spraying (ORS) for malaria vector-control in this region. A cluster randomized controlled trial was conducted between July 2018 and April 2019 in twelve villages in Karen (Kayin) state, Myanmar. Villages were randomly assigned to receive either a single round of ORS with a capsule suspension of lambda-cyhalothrin for two days in October or no intervention (six villages per group). The primary endpoint was the biting rate of malaria mosquitoes assessed with human-landing catch and cow-baited trap collection methods, and was analyzed with a Bayesian multi-level model. In the intervention villages, the proportion of households located within the sprayed area ranged between 42 and 100% and the application rate ranged between 63 and 559 g of active ingredient per hectare. At baseline, the median of Anopheles biting rate estimates in the twelve villages was 2 bites per person per night (inter-quartile range [IQR] 0–5, range 0–48) indoors, 6 bites per person per night (IQR 2–16, range 0–342) outdoors and 206 bites per cow per night (IQR 83–380, range 19–1149) in the cow-baited trap. In intention-to-treat analysis, it was estimated that ORS reduced biting rate by 72% (95% confidence interval [CI] 63–79) from Month 0 to Month 3 and by 79% (95% CI 62–88) from Month 4 to Month 6, considering control villages as the reference. In conclusion, ORS rapidly reduces the biting rates of malaria mosquitoes in a Southeast Asian setting where the vectors bite mostly outdoors and at a time when people are not protected by mosquito bed nets.
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Affiliation(s)
- Victor Chaumeau
- Shoklo Malaria Research Unit, Mahidol-Oxford Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
- * E-mail:
| | - Ladda Kajeechiwa
- Shoklo Malaria Research Unit, Mahidol-Oxford Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - Thithiworada Kulabkeeree
- Shoklo Malaria Research Unit, Mahidol-Oxford Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - Sunisa Sawasdichai
- Shoklo Malaria Research Unit, Mahidol-Oxford Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - Warat Haohankhunnatham
- Shoklo Malaria Research Unit, Mahidol-Oxford Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - Aritsara Inta
- Shoklo Malaria Research Unit, Mahidol-Oxford Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - Monthicha Phanaphadungtham
- Shoklo Malaria Research Unit, Mahidol-Oxford Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - Florian Girond
- Institut Pasteur du Cambodge, Institut Pasteur International Network, Phnom Penh, Cambodia
- Institut de Recherche pour le Développement, UMR 228 Espace-Dev (IRD, UA, UG, UM, UR), Phnom Penh, Cambodia
| | - Vincent Herbreteau
- Institut de Recherche pour le Développement, UMR 228 Espace-Dev (IRD, UA, UG, UM, UR), Phnom Penh, Cambodia
| | - Gilles Delmas
- Shoklo Malaria Research Unit, Mahidol-Oxford Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - François Nosten
- Shoklo Malaria Research Unit, Mahidol-Oxford Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
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Rae JD, Nosten S, Kajeechiwa L, Wiladphaingern J, Parker DM, Landier J, Thu AM, Dah H, Be A, Cho WC, Paw K, Paw ES, Shee PB, Poe C, Nu C, Nyaw B, Simpson JA, Devine A, Maude RJ, Moo KL, Min MC, Thwin MM, Tun SW, Nosten FH. Surveillance to achieve malaria elimination in eastern Myanmar: a 7-year observational study. Malar J 2022; 21:175. [PMID: 35672747 PMCID: PMC9171744 DOI: 10.1186/s12936-022-04175-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 05/05/2022] [Indexed: 12/02/2022] Open
Abstract
BACKGROUND The collection and utilization of surveillance data is essential in monitoring progress towards achieving malaria elimination, in the timely response to increases in malaria case numbers and in the assessment of programme functioning. This paper describes the surveillance activities used by the malaria elimination task force (METF) programme which operates in eastern Myanmar, and provides an analysis of data collected from weekly surveillance, case investigations, and monitoring and evaluation of programme performance. METHODS This retrospective analysis was conducted using data collected from a network of 1250 malaria posts operational between 2014 and 2021. To investigate changes in data completeness, malaria post performance, malaria case numbers, and the demographic details of malaria cases, summary statistics were used to compare data collected over space and time. RESULTS In the first 3 years of the METF programme, improvements in data transmission routes resulted in a 18.9% reduction in late reporting, allowing for near real-time analysis of data collected at the malaria posts. In 2020, travel restrictions were in place across Karen State in response to COVID-19, and from February 2021 the military coup in Myanmar resulted in widescale population displacement. However, over that period there has been no decline in malaria post attendance, and the majority of consultations continue to occur within 48 h of fever onset. Case investigations found that 43.8% of cases travelled away from their resident village in the 3 weeks prior to diagnosis and 36.3% reported never using a bed net whilst sleeping in their resident village, which increased to 72.2% when sleeping away from their resident village. Malaria post assessments performed in 82.3% of the METF malaria posts found malaria posts generally performed to a high standard. CONCLUSIONS Surveillance data collected by the METF programme demonstrate that despite significant changes in the context in which the programme operates, malaria posts have remained accessible and continue to provide early diagnosis and treatment contributing to an 89.3% decrease in Plasmodium falciparum incidence between 2014 and 2021.
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Affiliation(s)
- Jade D. Rae
- Shoklo Malaria Research Unit (SMRU), Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
- 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
| | - Suphak Nosten
- Shoklo Malaria Research Unit (SMRU), Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - Ladda Kajeechiwa
- Shoklo Malaria Research Unit (SMRU), Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - Jacher Wiladphaingern
- Shoklo Malaria Research Unit (SMRU), Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - Daniel M. Parker
- Population Health and Disease Prevention, University of California-Irvine, Irvine, CA USA
- Epidemiology and Biostatistics, University of California-Irvine, Irvine, CA USA
| | - Jordi Landier
- IRD (Institut de Recherche Pour Le Developpement), Aix Marseille Univ, INSERM, SESSTIM, Aix Marseille Institute of Public Health, ISSPAM, Marseille, France
| | - Aung Myint Thu
- Shoklo Malaria Research Unit (SMRU), Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - Hsa Dah
- Shoklo Malaria Research Unit (SMRU), Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - Aye Be
- Shoklo Malaria Research Unit (SMRU), Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - Win Cho Cho
- Shoklo Malaria Research Unit (SMRU), Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - K.’Nyaw Paw
- Shoklo Malaria Research Unit (SMRU), Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - Eh Shee Paw
- Shoklo Malaria Research Unit (SMRU), Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - Paw Bway Shee
- Shoklo Malaria Research Unit (SMRU), Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - Christ Poe
- Shoklo Malaria Research Unit (SMRU), Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - Chit Nu
- Shoklo Malaria Research Unit (SMRU), Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - Baw Nyaw
- Shoklo Malaria Research Unit (SMRU), Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - Julie A. Simpson
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia
| | - Angela Devine
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia
- Global and Tropical Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, Australia
| | - 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
- Harvard TH Chan School of Public Health, Harvard University, Boston, USA
- The Open University, Milton Keynes, UK
| | - Ku Ler Moo
- Shoklo Malaria Research Unit (SMRU), Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - Myo Chit Min
- Shoklo Malaria Research Unit (SMRU), Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - May Myo Thwin
- Shoklo Malaria Research Unit (SMRU), Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - Saw Win Tun
- Shoklo Malaria Research Unit (SMRU), Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - François H. Nosten
- Shoklo Malaria Research Unit (SMRU), Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
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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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Impact of outdoor residual spraying on the biting rate of malaria vectors: A pilot study in four villages in Kayin state, Myanmar. PLoS One 2020; 15:e0240598. [PMID: 33119645 PMCID: PMC7595390 DOI: 10.1371/journal.pone.0240598] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 09/29/2020] [Indexed: 11/19/2022] Open
Abstract
Outdoor and early mosquito biters challenge the efficacy of bed-nets and indoor residual spraying on the Thailand-Myanmar border. Outdoor residual spraying is proposed for the control of exophilic mosquito species. The objective of this study was to assess the impact of outdoor residual spraying on the biting rate of malaria vectors in Kayin state, Myanmar. Outdoor residual spraying using lambda-cyhalothrin was carried out in two villages in December 2016 (beginning of the dry season) and two villages were used as a control. Malaria mosquitoes were captured at baseline and monthly for four months after the intervention using human-landing catch and cow-baited trap collection methods. The impact of outdoor residual spraying on human-biting rate was estimated with propensity score adjusted generalized linear mixed-effect regressions. At baseline, mean indoor and outdoor human-biting rate estimates ranged between 2.12 and 29.16 bites /person /night, and between 0.20 and 1.72 bites /person /night in the intervention and control villages respectively. Using model output, we estimated that human-biting rate was reduced by 91% (95%CI = 88–96, P <0.0001) immediately after outdoor residual spraying. Human-biting rate remained low in all sprayed villages for 3 months after the intervention. Malaria vector populations rose at month 4 in the intervention villages but not in the controls. This coincided with the expected end of insecticide mist residual effects, thereby suggesting that residual effects are important determinants of intervention outcome. We conclude that outdoor residual spraying with a capsule suspension of lambda-cyhalothrin rapidly reduced the biting rate malaria vectors in this area where pyrethroid resistance has been documented.
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Ome-Kaius M, Kattenberg JH, Zaloumis S, Siba M, Kiniboro B, Jally S, Razook Z, Mantila D, Sui D, Ginny J, Rosanas-Urgell A, Karl S, Obadia T, Barry A, Rogerson SJ, Laman M, Tisch D, Felger I, Kazura JW, Mueller I, Robinson LJ. Differential impact of malaria control interventions on P. falciparum and P. vivax infections in young Papua New Guinean children. BMC Med 2019; 17:220. [PMID: 31813381 PMCID: PMC6900859 DOI: 10.1186/s12916-019-1456-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2019] [Accepted: 10/29/2019] [Indexed: 12/21/2022] Open
Abstract
INTRODUCTION As malaria transmission declines, understanding the differential impact of intensified control on Plasmodium falciparum relative to Plasmodium vivax and identifying key drivers of ongoing transmission is essential to guide future interventions. METHODS Three longitudinal child cohorts were conducted in Papua New Guinea before (2006/2007), during (2008) and after scale-up of control interventions (2013). In each cohort, children aged 1-5 years were actively monitored for infection and illness. Incidence of malaria episodes, molecular force of blood-stage infections (molFOB) and population-averaged prevalence of infections were compared across the cohorts to investigate the impact of intensified control in young children and the key risk factors for malaria infection and illness in 2013. RESULTS Between 2006 and 2008, P. falciparum infection prevalence, molFOB, and clinical malaria episodes reduced by 47%, 59% and 69%, respectively, and a further 49%, 29% and 75% from 2008 to 2013 (prevalence 41.6% to 22.1% to 11.2%; molFOB: 3.4 to 1.4 to 1.0 clones/child/year; clinical episodes incidence rate (IR) 2.6 to 0.8 to IR 0.2 episodes/child/year). P. vivax clinical episodes declined at rates comparable to P. falciparum between 2006, 2008 and 2013 (IR 2.5 to 1.1 to 0.2), while P. vivax molFOB (2006, 9.8; 2008, 12.1) and prevalence (2006, 59.6%; 2008, 65.0%) remained high in 2008. However, in 2013, P. vivax molFOB (1.2) and prevalence (19.7%) had also substantially declined. In 2013, 89% of P. falciparum and 93% of P. vivax infections were asymptomatic, 62% and 47%, respectively, were sub-microscopic. Area of residence was the major determinant of malaria infection and illness. CONCLUSION Intensified vector control and routine case management had a differential impact on rates of P. falciparum and P. vivax infections but not clinical malaria episodes in young children. This suggests comparable reductions in new mosquito-derived infections but a delayed impact on P. vivax relapsing infections due to a previously acquired reservoir of hypnozoites. This demonstrates the need to strengthen implementation of P. vivax radical cure to maximise impact of control in co-endemic areas. The high heterogeneity of malaria in 2013 highlights the importance of surveillance and targeted interventions to accelerate towards elimination.
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Affiliation(s)
- Maria Ome-Kaius
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea.,Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia.,Department of Medical Biology, University of Melbourne, Melbourne, Australia
| | - Johanna Helena Kattenberg
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea.,Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia.,Institute of Tropical Medicine, Antwerp, Belgium
| | - Sophie Zaloumis
- Department of Medical Biology, University of Melbourne, Melbourne, Australia
| | - Matthew Siba
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - Benson Kiniboro
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - Shadrach Jally
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - Zahra Razook
- Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
| | - Daisy Mantila
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - Desmond Sui
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - Jason Ginny
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | | | - Stephan Karl
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea.,Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
| | | | - Alyssa Barry
- Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia
| | - Stephen J Rogerson
- Department of Medical Biology, University of Melbourne, Melbourne, Australia
| | - Moses Laman
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | | | - Ingrid Felger
- Swiss Tropical and Public Health Institute, Basel, Switzerland
| | | | - Ivo Mueller
- Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia.,Department of Medical Biology, University of Melbourne, Melbourne, Australia.,Institut Pasteur, Paris, France
| | - Leanne J Robinson
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea. .,Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia. .,Department of Medical Biology, University of Melbourne, Melbourne, Australia. .,Burnet Institute, Melbourne, Australia.
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9
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Chaumeau V, Fustec B, Nay Hsel S, Montazeau C, Naw Nyo S, Metaane S, Sawasdichai S, Kittiphanakun P, Phatharakokordbun P, Kwansomboon N, Andolina C, Cerqueira D, Chareonviriyaphap T, Nosten FH, Corbel V. Entomological determinants of malaria transmission in Kayin state, Eastern Myanmar: A 24-month longitudinal study in four villages. Wellcome Open Res 2019; 3:109. [PMID: 31206035 PMCID: PMC6544137 DOI: 10.12688/wellcomeopenres.14761.4] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/04/2019] [Indexed: 11/20/2022] Open
Abstract
Background: The Thailand-Myanmar borderland is an area endemic for malaria where transmission is low, seasonal and unstable. The epidemiology has been described but there is relatively few data on the entomological determinants of malaria transmission. Methods: Entomological investigations were conducted during 24 months in four villages located in Kayin state, on the Myanmar side of the Thailand-Myanmar border.
Anopheles mosquitoes were identified by morphology, and molecular assays were used in order to discriminate between closely related sibling species of malaria vectors.
Plasmodium infection rate was determined using quantitative real-time PCR. Results: The diversity of
Anopheles mosquitoes was very high and multiple species were identified as malaria vectors. The intensity of human-vector contact (mean human-biting rate= 369 bites/person/month) compensates for the low infection rate in naturally infected populations of malaria vectors (mean sporozoite index= 0.04 and 0.17 % for
P. falciparum and
P. vivax respectively), yielding intermediary level of transmission intensity (mean entomological inoculation rate= 0.13 and 0.64 infective bites/person/month for
P. falciparum and
P. vivax, respectively). Only 36% of the infected mosquitoes were collected indoors between 09:00 pm and 05:00 am, suggesting that mosquito bed-nets would fail to prevent most of the infective bites in the study area. Conclusion: This study provided a unique opportunity to describe the entomology of malaria in low transmission settings of Southeast Asia. Our data are important in the context of malaria elimination in the Greater Mekong Subregion.
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Affiliation(s)
- Victor Chaumeau
- Centre Hospitalier Universitaire de Montpellier, Montpellier, 34295, France.,Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle, Institut de Recherche pour le Développement, Montpellier, 34394, France.,Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, 63110, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, OX3 7BN, UK
| | - Bénédicte Fustec
- Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle, Institut de Recherche pour le Développement, Montpellier, 34394, France
| | - Saw Nay Hsel
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, 63110, Thailand
| | - Céline Montazeau
- Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle, Institut de Recherche pour le Développement, Montpellier, 34394, France
| | - Saw Naw Nyo
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, 63110, Thailand
| | - Selma Metaane
- Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle, Institut de Recherche pour le Développement, Montpellier, 34394, France
| | - Sunisa Sawasdichai
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, 63110, Thailand
| | - Prapan Kittiphanakun
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, 63110, Thailand
| | - Phabele Phatharakokordbun
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, 63110, Thailand
| | - Nittipha Kwansomboon
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, 10900, Thailand
| | - Chiara Andolina
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, 63110, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, OX3 7BN, UK
| | - Dominique Cerqueira
- Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle, Institut de Recherche pour le Développement, Montpellier, 34394, France
| | | | - François H Nosten
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, 63110, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, OX3 7BN, UK
| | - Vincent Corbel
- Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle, Institut de Recherche pour le Développement, Montpellier, 34394, France
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10
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Chaumeau V, Fustec B, Nay Hsel S, Montazeau C, Naw Nyo S, Metaane S, Sawasdichai S, Kittiphanakun P, Phatharakokordbun P, Kwansomboon N, Andolina C, Cerqueira D, Chareonviriyaphap T, Nosten FH, Corbel V. Entomological determinants of malaria transmission in Kayin state, Eastern Myanmar: A 24-month longitudinal study in four villages. Wellcome Open Res 2019; 3:109. [DOI: 10.12688/wellcomeopenres.14761.3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/01/2019] [Indexed: 11/20/2022] Open
Abstract
Background: The Thailand-Myanmar borderland is an area endemic for malaria where transmission is low, seasonal and unstable. The epidemiology has been described but there is relatively few data on the entomological determinants of malaria transmission. Methods: Entomological investigations were conducted during 24 months in four villages located in Kayin state, on the Myanmar side of the Thailand-Myanmar border. Anopheles mosquitoes were identified by morphology, and molecular assays were used in order to discriminate between closely related sibling species of malaria vectors. Plasmodium infection rate was determined using quantitative real-time PCR. Results: The diversity of Anopheles mosquitoes was very high and multiple species were identified as malaria vectors. The intensity of human-vector contact (mean human-biting rate= 369 bites/person/month) compensates for the low infection rate in naturally infected populations of malaria vectors (mean sporozoite index= 0.04 and 0.17 % for P. falciparum and P. vivax respectively), yielding intermediary level of transmission intensity (mean entomological inoculation rate= 0.13 and 0.64 infective bites/person/month for P. falciparum and P. vivax, respectively). Only 36% of the infected mosquitoes were collected indoors between 09:00 pm and 05:00 am, suggesting that mosquito bed-nets would fail to prevent most of the infective bites in the study area. Conclusion: This study provided a unique opportunity to describe the entomology of malaria in low transmission settings of Southeast Asia. Our data are important in the context of malaria elimination in the Greater Mekong Subregion.
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11
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Chaumeau V, Kajeechiwa L, Fustec B, Landier J, Naw Nyo S, Nay Hsel S, Phatharakokordbun P, Kittiphanakun P, Nosten S, Thwin MM, Win Tun S, Wiladphaingern J, Cottrell G, Parker DM, Minh MC, Kwansomboon N, Metaane S, Montazeau C, Kunjanwong K, Sawasdichai S, Andolina C, Ling C, Haohankhunnatham W, Christiensen P, Wanyatip S, Konghahong K, Cerqueira D, Imwong M, Dondorp AM, Chareonviriyaphap T, White NJ, Nosten FH, Corbel V. Contribution of Asymptomatic Plasmodium Infections to the Transmission of Malaria in Kayin State, Myanmar. J Infect Dis 2019; 219:1499-1509. [PMID: 30500927 PMCID: PMC6467188 DOI: 10.1093/infdis/jiy686] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Accepted: 11/27/2018] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND The objective of mass antimalarial drug administration (MDA) is to eliminate malaria rapidly by eliminating the asymptomatic malaria parasite reservoirs and interrupting transmission. In the Greater Mekong Subregion, where artemisinin-resistant Plasmodium falciparum is now widespread, MDA has been proposed as an elimination accelerator, but the contribution of asymptomatic infections to malaria transmission has been questioned. The impact of MDA on entomological indices has not been characterized previously. METHODS MDA was conducted in 4 villages in Kayin State (Myanmar). Malaria mosquito vectors were captured 3 months before, during, and 3 months after MDA, and their Plasmodium infections were detected by polymerase chain reaction (PCR) analysis. The relationship between the entomological inoculation rate, the malaria prevalence in humans determined by ultrasensitive PCR, and MDA was characterized by generalized estimating equation regression. RESULTS Asymptomatic P. falciparum and Plasmodium vivax infections were cleared by MDA. The P. vivax entomological inoculation rate was reduced by 12.5-fold (95% confidence interval [CI], 1.6-100-fold), but the reservoir of asymptomatic P. vivax infections was reconstituted within 3 months, presumably because of relapses. This was coincident with a 5.3-fold (95% CI, 4.8-6.0-fold) increase in the vector infection rate. CONCLUSION Asymptomatic infections are a major source of malaria transmission in Southeast Asia.
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Affiliation(s)
- Victor Chaumeau
- Centre hospitalier universitaire de Montpellier, Montpellier
- UMR 224 “Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle,” Institut de Recherche pour le Développement, Montpellier
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, United Kingdom
| | - Ladda Kajeechiwa
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot
| | - Bénédicte Fustec
- UMR 224 “Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle,” Institut de Recherche pour le Développement, Montpellier
| | - Jordi Landier
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot
- Institut de Recherches pour le Développement, Aix Marseille Univ, INSERM, SESSTIM, Marseille
| | - Saw Naw Nyo
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot
| | - Saw Nay Hsel
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot
| | - Phabele Phatharakokordbun
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot
| | - Prapan Kittiphanakun
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot
| | - Suphak Nosten
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot
| | - May Myo Thwin
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot
| | - Saw Win Tun
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot
| | - Jacher Wiladphaingern
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot
| | - Gilles Cottrell
- UMR 216 “Mère et enfant face aux infections tropicales,” Institut de Recherche pour le Développement, Université Paris Descartes, Paris, France
| | - Daniel M Parker
- Department of Population Health and Disease Prevention, University of California, Irvine
| | - Myo Chit Minh
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot
| | - Nittpha Kwansomboon
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand
| | - Selma Metaane
- UMR 224 “Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle,” Institut de Recherche pour le Développement, Montpellier
| | - Céline Montazeau
- UMR 224 “Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle,” Institut de Recherche pour le Développement, Montpellier
| | - Kitti Kunjanwong
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand
| | - Sunisa Sawasdichai
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot
| | - Chiara Andolina
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, United Kingdom
| | - Clare Ling
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, United Kingdom
| | - Warat Haohankhunnatham
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot
| | - Peter Christiensen
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot
| | - Sunaree Wanyatip
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot
| | - Kamonchanok Konghahong
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot
| | - Dominique Cerqueira
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand
| | - Mallika Imwong
- Department of Molecular Tropical Medicine and Genetics, Faculty of Tropical Medicine, Mahidol University
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University
| | - Arjen M Dondorp
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, United Kingdom
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University
| | | | - Nicholas J White
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, United Kingdom
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University
| | - François H Nosten
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, United Kingdom
| | - Vincent Corbel
- UMR 224 “Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle,” Institut de Recherche pour le Développement, Montpellier
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12
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Chaumeau V, Fustec B, Nay Hsel S, Montazeau C, Naw Nyo S, Metaane S, Sawasdichai S, Kittiphanakun P, Phatharakokordbun P, Kwansomboon N, Andolina C, Cerqueira D, Chareonviriyaphap T, Nosten FH, Corbel V. Entomological determinants of malaria transmission in Kayin state, Eastern Myanmar: A 24-month longitudinal study in four villages. Wellcome Open Res 2019; 3:109. [DOI: 10.12688/wellcomeopenres.14761.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/29/2019] [Indexed: 11/20/2022] Open
Abstract
Background: The Thailand-Myanmar borderland is an area endemic for malaria where transmission is low, seasonal and unstable. The epidemiology has been described but there is relatively few data on the entomological determinants of malaria transmission. Methods: Entomological investigations were conducted during 24 months in four villages located in Kayin state, on the Myanmar side of the Thailand-Myanmar border. Anopheles mosquitoes were identified by morphology, and molecular assays were used in order to discriminate between closely related sibling species of malaria vectors. Plasmodium infection rate was determined using quantitative real-time PCR. Results: The diversity of Anopheles mosquitoes was very high and multiple species were identified as malaria vectors. The intensity of human-vector contact (mean human-biting rate= 369 bites/person/month) compensates for the low infection rate in naturally infected populations of malaria vectors (mean sporozoite index= 0.04 and 0.17 % for P. falciparum and P. vivax respectively), yielding intermediary level of transmission intensity (mean entomological inoculation rate= 0.13 and 0.64 infective bites/person/month for P. falciparum and P. vivax, respectively). Only 36% of the infected mosquitoes were collected indoors between 09:00 pm and 05:00 am, suggesting that mosquito bed-nets would fail to prevent most of the infective bites in the study area. Conclusion: This study provided a unique opportunity to describe the entomology of malaria in low transmission settings of Southeast Asia. Our data are important in the context of malaria elimination in the Greater Mekong Subregion.
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13
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Chaumeau V, Fustec B, Nay Hsel S, Montazeau C, Naw Nyo S, Metaane S, Sawasdichai S, Kittiphanakun P, Phatharakokordbun P, Kwansomboon N, Andolina C, Cerqueira D, Chareonviriyaphap T, Nosten FH, Corbel V. Entomological determinants of malaria transmission in Kayin state, Eastern Myanmar: A 24-month longitudinal study in four villages. Wellcome Open Res 2018; 3:109. [DOI: 10.12688/wellcomeopenres.14761.1] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/23/2018] [Indexed: 11/20/2022] Open
Abstract
Background: The Thailand-Myanmar borderland is an area endemic for malaria where transmission is low, seasonal and unstable. The epidemiology has been described but there is relatively few data on the entomological determinants of malaria transmission. Methods: As part of a pilot study on Targeted Malaria Elimination, entomological investigations were conducted during 24 months in four villages located in Kayin state, Myanmar. Anopheles mosquitoes were identified by morphology, and molecular assays were used in order to discriminate between closely related sibling species of malaria vectors. Plasmodium infection rate was determined using quantitative real-time PCR. Results: The biodiversity of Anopheles entomo-fauna was very high and multiple species were identified as malaria vectors. The intensity of human-vector contact (mean human-biting rate= 369 bites/person/month) compensates for the low infection rate in naturally infected populations of malaria vectors (mean sporozoite index= 0.4 and 1.7 /1,000 mosquitoes for P. falciparum and P. vivax respectively), yielding intermediary level of transmission intensity (mean entomological inoculation rate= 0.13 and 0.64 infective bites/person/month for P. falciparum and P. vivax, respectively). We estimated that 65% of the potential infective bites are not prevented by mosquito bed nets because of outdoor and early biters. Conclusion: This study provided a unique opportunity to describe the entomology of malaria in low transmission settings of Southeast Asia. Our data are important in the context of malaria elimination in the Greater Mekong Subregion.
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14
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Wangdi K, Furuya-Kanamori L, Clark J, Barendregt JJ, Gatton ML, Banwell C, Kelly GC, Doi SAR, Clements ACA. Comparative effectiveness of malaria prevention measures: a systematic review and network meta-analysis. Parasit Vectors 2018; 11:210. [PMID: 29587882 PMCID: PMC5869791 DOI: 10.1186/s13071-018-2783-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Accepted: 03/06/2018] [Indexed: 11/24/2022] Open
Abstract
Background Malaria causes significant morbidity and mortality worldwide. There are several preventive measures that are currently employed, including insecticide-treated nets (ITNs, including long-lasting insecticidal nets and insecticidal-treated bed nets), indoor residual spraying (IRS), prophylactic drugs (PD), and untreated nets (UN). However, it is unclear which measure is the most effective for malaria prevention. We therefore undertook a network meta-analysis to compare the efficacy of different preventive measures on incidence of malaria infection. Methods A systematic literature review was undertaken across four medical and life sciences databases (PubMed, Cochrane Central, Embase, and Web of Science) from their inception to July 2016 to compare the effectiveness of different preventive measures on malaria incidence. Data from the included studies were analysed for the effectiveness of several measures against no intervention (NI). This was carried out using an automated generalized pairwise modeling (GPM) framework for network meta-analysis to generate mixed treatment effects against a common comparator of no intervention (NI). Results There were 30 studies that met the inclusion criteria from 1998–2016. The GPM framework led to a final ranking of effectiveness of measures in the following order from best to worst: PD, ITN, IRS and UN, in comparison with NI. However, only ITN (RR: 0.49, 95% CI: 0.32–0.74) showed precision while other methods [PD (RR: 0.24, 95% CI: 0.004–15.43), IRS (RR: 0.55, 95% CI: 0.20–1.56) and UN (RR: 0.73, 95% CI: 0.28–1.90)] demonstrating considerable uncertainty associated with their point estimates. Conclusion Current evidence is strong for the protective effect of ITN interventions in malaria prevention. Even though ITNs were found to be the only preventive measure with statistical support for their effectiveness, the role of other malaria control measures may be important adjuncts in the global drive to eliminate malaria. Electronic supplementary material The online version of this article (10.1186/s13071-018-2783-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Kinley Wangdi
- Research School of Population Health, College of Health and Medicine, The Australian National University, ACT, Canberra, Australia.
| | - Luis Furuya-Kanamori
- Research School of Population Health, College of Health and Medicine, The Australian National University, ACT, Canberra, Australia.,Department of Population Medicine, College of Medicine, Qatar University, Doha, Qatar
| | - Justin Clark
- Centre for Research in Evidence-Based Practice (CREBP), Faculty of Health Sciences and Medicine, Bond University, Gold Coast, Queensland, Australia
| | - Jan J Barendregt
- School of Public Health, The University of Queensland, Brisbane, Queensland, Australia.,Epigear International Pty Ltd, Sunrise Beach, Queensland, Australia
| | - Michelle L Gatton
- School of Public Health & Social Work, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Cathy Banwell
- Research School of Population Health, College of Health and Medicine, The Australian National University, ACT, Canberra, Australia
| | - Gerard C Kelly
- Research School of Population Health, College of Health and Medicine, The Australian National University, ACT, Canberra, Australia
| | - Suhail A R Doi
- Research School of Population Health, College of Health and Medicine, The Australian National University, ACT, Canberra, Australia.,Department of Population Medicine, College of Medicine, Qatar University, Doha, Qatar
| | - Archie C A Clements
- Research School of Population Health, College of Health and Medicine, The Australian National University, ACT, Canberra, Australia
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Gosling RD, Whittaker M, Gueye CS, Fullman N, Baquilod M, Kusriastuti R, Feachem RGA. Malaria elimination gaining ground in the Asia Pacific. Malar J 2012; 11:346. [PMID: 23078536 PMCID: PMC3504559 DOI: 10.1186/1475-2875-11-346] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Accepted: 10/14/2012] [Indexed: 11/12/2022] Open
Abstract
Countries in the Asia Pacific region are making substantial progress toward eliminating malaria, but their success stories are rarely heard by a global audience. “Malaria 2012: Saving Lives in the Asia-Pacific,” a conference hosted by the Australian Government in Sydney, Australia from October 31 to November 2, 2012, will provide a unique opportunity to showcase the region’s work in driving down malaria transmission. One of the features of Malaria 2012 will be the Asia Pacific Malaria Elimination Network (APMEN), which has focused on harnessing the collective experiences of 13 countries through regional political and technical collaboration since its inception in 2009. Run by country partners, APMEN unites a range of partners – from national malaria programmes and academic institutions to global and regional policymaking bodies – to support each country’s malaria elimination goals through knowledge sharing, capacity building, operational research and advocacy.
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Affiliation(s)
- Roly D Gosling
- The Global Health Group, University of California, San Francisco, San Francisco, CA, USA.
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Tisgratog R, Tananchai C, Juntarajumnong W, Tuntakom S, Bangs MJ, Corbel V, Chareonviriyaphap T. Host feeding patterns and preference of Anopheles minimus (Diptera: Culicidae) in a malaria endemic area of western Thailand: baseline site description. Parasit Vectors 2012; 5:114. [PMID: 22676415 PMCID: PMC3407501 DOI: 10.1186/1756-3305-5-114] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Accepted: 06/07/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Host feeding patterns of Anopheles minimus in relation to ambient environmental conditions were observed during a 2-year period at Tum Sua Village, located in Mae Sot District, Tak Province, in western Thailand, where An. minimus is found in abundance and regarded as the most predominant malaria vector species. Detailed information on mosquito behavior is important for understanding the epidemiology of disease transmission and developing more effective and efficient vector control methods. METHODS Adult mosquitoes were collected every 2 months for two consecutive nights from 1800 to 0600 hrs. Three collection methods were used; indoor human-landing collections (HLC), outdoor HLC, and outdoor cattle-bait collections (CBC). RESULTS A total of 7,663 female Anopheles mosquitoes were collected of which 5,392 were identified as members of 3 different species complexes, the most prevalent being Anopheles minimus complex (50.36%), followed by Anopheles maculatus complex (19.68%) and Anopheles dirus complex (0.33%). An. minimus s.s. comprised virtually all (> 99.8 percent) of Minimus Complex species captured. Blood feeding behavior of An. minimus was more pronounced during the second half of the evening, showing a slight preference to blood feed outdoors (~60%) versus inside structures. Significantly (P < 0.0001) more An. minimus were collected from human-baited methods compared with a tethered cow, indicating a more anthropophilic feeding behavior. Although a significant difference in total number of mosquitoes from the HLC was recorded between the first and second year, the mean biting frequency over the course of the evening hours remained similar. CONCLUSIONS The Human landing activity of An. minimus in Tum Sua Village showed a stronger preference/attraction for humans compared to a cow-baited collection method. This study supports the incrimination of An. minimus as the primary malaria vector in the area. A better understanding of mosquito behavior related to host preference, and the temporal and spatial blood feeding activity will help facilitate the design of vector control strategies and effectiveness of vector control management programs in Thailand.
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Affiliation(s)
- Rungarun Tisgratog
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, 10900, Thailand
| | - Chatchai Tananchai
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, 10900, Thailand
| | - Waraporn Juntarajumnong
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, 10900, Thailand
| | - Siripun Tuntakom
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Kamphaengsaen, Nakhon Pathom, 73140, Thailand
| | - Michael J Bangs
- Public Health & Malaria Control Department, Jl. Kertajasa, Kuala Kencana, Papua, 99920, Indonesia
| | - Vincent Corbel
- Institut de Recherche pour le Développement (IRD), Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle (IRD 224-CNRS 5290 UM1-UM2), Montpellier Cedex 5, France
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Jongwutiwes S, Buppan P, Kosuvin R, Seethamchai S, Pattanawong U, Sirichaisinthop J, Putaporntip C. Plasmodium knowlesiMalaria in Humans and Macaques, Thailand. Emerg Infect Dis 2011; 17:1799-806. [PMID: 22000348 PMCID: PMC3310673 DOI: 10.3201/eid1710.110349] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
This parasite may be transmitted from macaques to humans. Naturally acquired human infections with Plasmodium knowlesi are endemic to Southeast Asia. To determine the prevalence of P. knowlesi malaria in malaria-endemic areas of Thailand, we analyzed genetic characteristics of P. knowlesi circulating among naturally infected macaques and humans. This study in 2008–2009 and retrospective analysis of malaria species in human blood samples obtained in 1996 from 1 of these areas showed that P. knowlesi accounted for 0.67% and 0.48% of human malaria cases, respectively, indicating that this simian parasite is not a newly emergent human pathogen in Thailand. Sequence analysis of the complete merozoite surface protein 1 gene of P. knowlesi from 10 human and 5 macaque blood samples showed considerable genetic diversity among isolates. The sequence from 1 patient was identical with that from a pig-tailed macaque living in the same locality, suggesting cross-transmission of P. knowlesi from naturally infected macaques to humans.
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Phimpraphi W, Paul RE, Yimsamran S, Puangsa-art S, Thanyavanich N, Maneeboonyang W, Prommongkol S, Sornklom S, Chaimungkun W, Chavez IF, Blanc H, Looareesuwan S, Sakuntabhai A, Singhasivanon P. Longitudinal study of Plasmodium falciparum and Plasmodium vivax in a Karen population in Thailand. Malar J 2008; 7:99. [PMID: 18518964 PMCID: PMC2443811 DOI: 10.1186/1475-2875-7-99] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2007] [Accepted: 06/02/2008] [Indexed: 11/16/2022] Open
Abstract
Background Clinical case treatment of malaria infections where Plasmodium falciparum and Plasmodium vivax are sympatric has achieved effective reductions in P. falciparum prevalence and incidence rates, but has been less successful for P. vivax. The high transmissibility of P. vivax and its capacity to relapse have been suggested to make it a harder parasite species to control. Methods A clinical malaria case treatment programme was carried out over a decade in a Karen community composed of seven hamlets on the Thai-Myanmar border. Results From 1994 to 2004, prevalence rates of both P. falciparum and P. vivax decreased by 70–90% in six of the seven study hamlets, but were unchanged in one hamlet. Overall, incidence rates decreased by 72% and 76% for P. falciparum and P. vivax respectively over the period 1999–2004. The age-incidence and prevalence curves suggested that P. vivax was more transmissible than P. falciparum despite a greater overall burden of infection with P. falciparum. Male gender was associated with increased risk of clinical presentation with either parasite species. Children (< 15 years old) had an increased risk of presenting with P. vivax but not P. falciparum. Conclusion There was a considerable reduction in incidence rates of both P. vivax and P. falciparum over a decade following implementation of a case treatment programme. The concern that intervention methods would inadvertently favour one species over another, or even lead to an increase in one parasite species, does not appear to be fulfilled in this case.
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Affiliation(s)
- Waraphon Phimpraphi
- Department of Tropical Hygiene, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
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Obsomer V, Defourny P, Coosemans M. The Anopheles dirus complex: spatial distribution and environmental drivers. Malar J 2007; 6:26. [PMID: 17341297 PMCID: PMC1838916 DOI: 10.1186/1475-2875-6-26] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2006] [Accepted: 03/06/2007] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The Anopheles dirus complex includes efficient malaria vectors of the Asian forested zone. Studies suggest ecological and biological differences between the species of the complex but variations within species suggest possible environmental influences. Behavioural variation might determine vector capacity and adaptation to changing environment. It is thus necessary to clarify the species distributions and the influences of environment on behavioural heterogeneity. METHODS A literature review highlights variation between species, influences of environmental drivers, and consequences on vector status and control. The localisation of collection sites from the literature and from a recent project (MALVECASIA) produces detailed species distributions maps. These facilitate species identification and analysis of environmental influences. RESULTS The maps give a good overview of species distributions. If species status partly explains behavioural heterogeneity, occurrence and vectorial status, some environmental drivers have at least the same importance. Those include rainfall, temperature, humidity, shade, soil type, water chemistry and moon phase. Most factors are probably constantly favourable in forest. Biological specificities, behaviour and high human-vector contact in the forest can explain the association of this complex with high malaria prevalence, multi-drug resistant Plasmodium falciparum and partial control failure of forest malaria in Southeast Asia. CONCLUSION Environmental and human factors seem better than species specificities at explaining behavioural heterogeneity. Although forest seems essential for mosquito survival, adaptations to orchards and wells have been recorded. Understanding the relationship between landscape components and mosquito population is a priority in foreseeing the influence of land-cover changes on malaria occurrence and in shaping control strategies for the future.
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Affiliation(s)
- Valérie Obsomer
- Department of Parasitology, Prince Leopold Institute of Tropical Medicine, Nationalestraat 155, 2000 Antwerp, Belgium
- Department of Environmental Sciences and Land Use Planning, Université Catholique de Louvain, Croix du Sud 2/16, B-1348 Louvain-la-Neuve, Belgium
| | - Pierre Defourny
- Department of Environmental Sciences and Land Use Planning, Université Catholique de Louvain, Croix du Sud 2/16, B-1348 Louvain-la-Neuve, Belgium
| | - Marc Coosemans
- Department of Parasitology, Prince Leopold Institute of Tropical Medicine, Nationalestraat 155, 2000 Antwerp, Belgium
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Chaiyasit D, Choochote W, Rattanachanpichai E, Chaithong U, Chaiwong P, Jitpakdi A, Tippawangkosol P, Riyong D, Pitasawat B. Essential oils as potential adulticides against two populations of Aedes aegypti, the laboratory and natural field strains, in Chiang Mai province, northern Thailand. Parasitol Res 2006; 99:715-21. [PMID: 16738885 DOI: 10.1007/s00436-006-0232-x] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2006] [Accepted: 04/27/2006] [Indexed: 11/24/2022]
Abstract
Essential oils derived from five plant species, celery (Apium graveolens), caraway (Carum carvi), zedoary (Curcuma zedoaria), long pepper (Piper longum), and Chinese star anise (Illicium verum), were subjected to investigation of adulticidal activity against mosquito vectors. Two populations of Aedes aegypti, the laboratory and natural field strains, collected in Chiang Mai province, northern Thailand were tested in pyrethroid-susceptibility bioassays. The results revealed that the natural field strain of A. aegypti was resistant to permethrin, with mortality rates ranging from 51 to 66%. A mild susceptibility, with mortality rates ranging from 82 to 88%, was observed in the natural field strain of A. aegypti exposed to lambdacyhalothrin, which suggested that this strain was tolerant and might be resistant to this insecticide. However, laboratory-reared A. aegypti exposed to discriminating dosages of permethrin and lambdacyhalothrin induced 100% mortality in all cases, thus indicating complete susceptibility of this strain to these insecticides. The adulticidal activity determined by topical application revealed that all five essential oils exerted a promising adulticidal efficacy against both laboratory and natural field strains of A. aegypti. Although the laboratory strain was slightly more susceptible to these essential oils than the natural field strain, no statistically significant difference was observed. Moreover, comparison of the adulticidal activity indicated that the performance of these essential oils against the two strains of A. aegypti was similar. The highest potential was established from caraway, followed by zedoary, celery, long pepper, and Chinese star anise, with an LC(50) in the laboratory strain of 5.44, 5.94, 5.96, 6.21, and 8.52 microg/mg female, respectively, and 5.54, 6.02, 6.14, 6.35, and 8.83 microg/mg female, respectively, in the field strain. These promising essential oils are, therefore, an alternative in developing and producing mosquito adulticides as an effective measure used in controlling and eradicating mosquito vectors.
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Affiliation(s)
- Dana Chaiyasit
- Department of Parasitology, Chiang Mai University, Chiang Mai 50200, Thailand
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Abstract
Effective indoor residual spraying against malaria vectors depends on whether mosquitoes rest indoors (i.e., endophilic behavior). This varies among species and is affected by insecticidal irritancy. Exophilic behavior has evolved in certain populations exposed to prolonged spraying programs. Optimum effectiveness of insecticide-treated nets presumably depends on vectors biting at hours when most people are in bed. Time of biting varies among different malaria vector species, but so far there is inconclusive evidence for these evolving so as to avoid bednets. Use of an untreated net diverts extra biting to someone in the same room who is without a net. Understanding choice of oviposition sites and dispersal behavior is important for the design of successful larval control programs including those using predatory mosquito larvae. Prospects for genetic control by sterile males or genes rendering mosquitoes harmless to humans will depend on competitive mating behavior. These methods are hampered by the immigration of monogamous, already-mated females.
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Affiliation(s)
- Helen Pates
- London School of Hygiene & Tropical Medicine, London WC1E 7HT, United Kingdom.
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Zhou G, Minakawa N, Githeko A, Yan G. Spatial distribution patterns of malaria vectors and sample size determination in spatially heterogeneous environments: a case study in the west Kenyan highland. JOURNAL OF MEDICAL ENTOMOLOGY 2004; 41:1001-1009. [PMID: 15605637 DOI: 10.1603/0022-2585-41.6.1001] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The current study examined temporal and spatial distribution patterns of anopheline malaria vectors in a highland site and determined the number of houses to be sampled to achieve the targeted precision level. Adult mosquito sampling was conducted seasonally in May and August 2002 in a 3 by 3-km2 area, and in November 2002 and February 2003 in an expanded 4 by 4-km2 area in Kakamega District, western Kenya. Anopheles gambiae Giles was the predominant malaria vector species, constituting 84.6% of the specimens, whereas Anopheles funestus Giles constituted 15.4% of the vector populations. An. gambiae abundance increased by six- to eight-fold in the long rainy season over the dry seasons, but An. funestus abundance peaked 3 mo after the long rainy season. For both species, the coefficient of variation was larger than 1, suggesting that the distribution of mosquito adults was aggregated. Mosquito clustering occurred in houses <400 m from a valley bottom. The negative binomial distribution was accepted in one sample period (August 2002) for An. gambiae and in two sampling periods (May and August 2002) for An. funestus. Taylor's power law analyses indicated that An. gambiae distribution was more aggregated in the wet seasons than in the dry seasons, whereas the degree of aggregation of An. funestus was similar in all four seasons. The minimum number of houses required to estimate anopheline female abundance within the commonly acceptable precision level (0.2) should be 17 houses per km2 for An. gambiae and 42 houses per km2 for An. funestus. The potential factors causing aggregated anopheline mosquito distribution are discussed.
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Affiliation(s)
- Guofa Zhou
- Department of Biological Sciences, State University of New York, Buffalo, NY 14260, USA
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Sattabongkot J, Tsuboi T, Zollner GE, Sirichaisinthop J, Cui L. Plasmodium vivax transmission: chances for control? Trends Parasitol 2004; 20:192-8. [PMID: 15099559 DOI: 10.1016/j.pt.2004.02.001] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
- Jetsumon Sattabongkot
- Entomology Department, USAMC Armed Forces Research Institute of Medical Sciences, 315/6 Rajavithi Road, Bangkok 10400, Thailand.
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Santos JB, dos Santos F, Macêdo V. [Variation of anopheles density with deltamethrin-impregnated mosquito nets in an endemic malaria area of the Brazilian Amazon]. CAD SAUDE PUBLICA 1999; 15:281-92. [PMID: 10409781 DOI: 10.1590/s0102-311x1999000200013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In 1992 a survey on the use of deltamethrin-impregnated mosquito nets was conducted in the municipality of Costa Marques, Rondonia. In the intradomicile, impregnated nets decreased the vector density at rates similar to those for non-impregnated nets during low-transmission periods; during high anopheline density periods, they led to a significant reduction in vector density, while in the non-impregnated net group there was an increase in the number of anophelines captured. There was no change in vector density in the peridomicile. In the impregnated net group, the most frequently captured species was Anopheles darlingi (63.2%), found mostly in the peridomicile, while Anopheles deaneorum (35.3%) was most frequent indoors. The impregnated mosquito nets' excitatory-repellent effect decreased the intradomiciliary vector density but did not alter density in the peridomicile.
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Affiliation(s)
- J B Santos
- Núcleo de Medicina Tropical, Universidade de Brasília, C. P. 4517, Brasília, DF 70919-970, Brasil
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Quiñones ML, Lines J, Thomson MC, Jawara M, Greenwood BM. Permethrin-treated bed nets do not have a 'mass-killing effect' on village populations of Anopheles gambiae s.l. in The Gambia. Trans R Soc Trop Med Hyg 1998; 92:373-8. [PMID: 9850383 DOI: 10.1016/s0035-9203(98)91053-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
In The Gambia, the use of permethrin-treated bed nets has led to a reduction in morbidity and mortality from malaria in children. However, no clear evidence has been found for a 'mass-killing effect' on the mosquito vectors as a result of this intervention. Two further entomological studies to investigate this phenomenon have been carried out. In one study, 20 villages were paired so that bed nets in one member of each pair were treated with permethrin. In the other, a cross-over design was used in which treated and untreated bed nets were exchanged between 2 villages. Longevity, biting rate and resting density of the malaria vector population and sporozoite rates were assessed in both studies. Malaria vectors were equally abundant and long-lived, and as likely to be infective, in villages with treated bed nets as in those with untreated nets. However, a clear reduction in the density of the indoor-resting population of mosquitoes in rooms with treated bed nets was found, probably reflecting the excito-repellency of the insecticide. This study confirmed that, in The Gambia, the protection against death and morbidity from malaria seen in children using treated bed nets must be due primarily to personal protection rather than to a 'mass-killing effect' on the mosquito vector population at a village level.
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Affiliation(s)
- M L Quiñones
- Medical Research Council Laboratories, The Gambia, Banjul, The Gambia
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Magbity EB, Marbiah NT, Maude G, Curtis CF, Bradley DJ, Greenwood BM, Petersen E, Lines JD. Effects of community-wide use of lambdacyhalothrin-impregnated bednets on malaria vectors in rural Sierra Leone. MEDICAL AND VETERINARY ENTOMOLOGY 1997; 11:79-86. [PMID: 9061681 DOI: 10.1111/j.1365-2915.1997.tb00293.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The effect of community-wide use of bednets treated with lambdacyhalothrin 10 mg/m2 on the malaria vector Anopheles gambiae (forest form) was evaluated in Sierra Leone. Sixteen similar villages near the town of Bo were randomly allocated either to remain without nets or to receive treated bednets for all inhabitants, with effect from June 1992. Mosquitoes were sampled using human biting catches on verandas, light-trap catch (beside an occupied untreated bednet), window exit-trap catch and pyrethrum spray collections. During the first year of intervention (June 1992 to July 1993) the treated bednets provided personal protection for people sleeping under them, but had very little impact on densities of An.gambiae collected on human bait. The human blood index (HBI) of An.gambiae was not affected (HBI = 99% in villages with and without nets). An.gambiae parous rates were significantly reduced in all intervention villages, but malaria sporozoite rates fell in only some of the villages. These results are intermediate between those obtained from other projects in Tanzania and Burkina Faso, where treated bednets reduced man-biting, parity and sporozoite rates, versus The Gambia where treated bednets had no significant impact on any of these factors. Possible reasons for these contrasted findings are discussed.
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