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Nguetsa GC, Elanga-Ndille E, Essangui Same EG, Nganso Keptchouang T, Mandeng SE, Ekoko Eyisap W, Binyang JA, Fogang B, Nouage L, Piameu M, Ayong L, Etang J, Wanji S, Eboumbou Moukoko CE. Utility of plasma anti-gSG6-P1 IgG levels in determining changes in Anopheles gambiae bite rates in a rural area of Cameroon. Sci Rep 2024; 14:14294. [PMID: 38906949 PMCID: PMC11192751 DOI: 10.1038/s41598-024-58337-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Accepted: 03/27/2024] [Indexed: 06/23/2024] Open
Abstract
The applicability of the specific human IgG antibody response to Anopheles gambiae salivary Gland Protein-6 peptide 1 (gSG6-P1 salivary peptide) as a biomarker able to distinguish the level of exposure to mosquito bites according to seasonal variations has not yet been evaluated in Central African regions. The study aimed to provide the first reliable data on the IgG anti-gSG6-P1 response in rural area in Cameroon according to the dry- and rainy-season. Between May and December 2020, dry blood samples were collected from people living in the Bankeng village in the forest area of the Centre region of Cameroon. Malaria infection was determined by thick-blood smear microscopy and multiplex PCR. The level of IgG anti-gSG6-P1 response, was assessed by enzyme-linked immunosorbent assay. Anopheles density and aggressiveness were assessed using human landing catches. The prevalence of malaria infection remains significantly higher in the rainy season than in the dry season (77.57% vs 61.44%; p = 0.0001). The specific anti-gSG6-P1 IgG response could be detected in individuals exposed to few mosquito bites and showed inter-individual heterogeneity even when living in the same exposure area. In both seasons, the level of anti-gSG6-P1 IgG response was not significantly different between Plasmodium infected and non-infected individuals. Mosquito bites were more aggressive in the rainy season compared to the dry season (human biting rate-HBR of 15.05 b/p/n vs 1.5 b/p/n) where mosquito density was very low. Infected mosquitoes were found only during the rainy season (sporozoite rate = 10.63% and entomological inoculation rate-EIR = 1.42 ib/p/n). The level of IgG anti-gSG6-P1 response was significantly higher in the rainy season and correlated with HBR (p ˂ 0.0001). This study highlights the high heterogeneity of individual's exposure to the Anopheles gambiae s.l vector bites depending on the transmission season in the same area. These findings reinforce the usefulness of the anti-gSG6-P1 IgG response as an accurate immunological biomarker for detecting individual exposure to Anopheles gambiae s.l. bites during the low risk period of malaria transmission in rural areas and for the differentiating the level of exposure to mosquitoes.
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Affiliation(s)
- Glwadys Cheteug Nguetsa
- Malaria Research Unit, Centre Pasteur Cameroon, P.O. Box 1274, Yaoundé, Cameroon.
- Department of Microbiology and Parasitology, Faculty of Sciences, The University of Buea, P.O. Box 63, Buea, Cameroon.
| | - Emmanuel Elanga-Ndille
- Department of Animal Biology, Faculty of Sciences, The University of Dschang, P.O. Box 96, Dschang, Cameroon
- Department of Medical Entomology, Centre for Research in Infectious Diseases, P.O. Box 13591, Yaoundé, Cameroon
| | - Estelle Géraldine Essangui Same
- Malaria Research Unit, Centre Pasteur Cameroon, P.O. Box 1274, Yaoundé, Cameroon
- Department of Biological Sciences, Faculty of Medicine and Pharmaceutical Sciences, The University of Douala, P.O. Box 2701, Douala, Cameroon
| | - Tatiana Nganso Keptchouang
- Malaria Research Unit, Centre Pasteur Cameroon, P.O. Box 1274, Yaoundé, Cameroon
- Department of Biological Sciences, Faculty of Medicine and Pharmaceutical Sciences, The University of Douala, P.O. Box 2701, Douala, Cameroon
| | - Stanilas Elysée Mandeng
- Department of Animal Biology and Physiology, Faculty of Sciences, The University of Yaoundé, P.O. Box 337, Yaounde 1, Cameroon
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon
| | - Wolfgang Ekoko Eyisap
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon
| | - Jérome Achille Binyang
- Department of Medical Entomology, Centre for Research in Infectious Diseases, P.O. Box 13591, Yaoundé, Cameroon
- Department of Animal Biology and Physiology, Faculty of Sciences, The University of Yaoundé, P.O. Box 337, Yaounde 1, Cameroon
| | - Balotin Fogang
- Malaria Research Unit, Centre Pasteur Cameroon, P.O. Box 1274, Yaoundé, Cameroon
- Department of Animal Biology and Physiology, Faculty of Sciences, The University of Yaoundé, P.O. Box 337, Yaounde 1, Cameroon
| | - Lynda Nouage
- Department of Medical Entomology, Centre for Research in Infectious Diseases, P.O. Box 13591, Yaoundé, Cameroon
- Department of Animal Biology and Physiology, Faculty of Sciences, The University of Yaoundé, P.O. Box 337, Yaounde 1, Cameroon
| | - Micheal Piameu
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon
- Ecole des Sciences de La Santé, Université Catholique d'Afrique Centrale, P.O. Box 1110, Yaoundé, Cameroon
| | - Lawrence Ayong
- Malaria Research Unit, Centre Pasteur Cameroon, P.O. Box 1274, Yaoundé, Cameroon
| | - Josiane Etang
- Department of Biological Sciences, Faculty of Medicine and Pharmaceutical Sciences, The University of Douala, P.O. Box 2701, Douala, Cameroon
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon
| | - Samuel Wanji
- Department of Microbiology and Parasitology, Faculty of Sciences, The University of Buea, P.O. Box 63, Buea, Cameroon
| | - Carole Else Eboumbou Moukoko
- Malaria Research Unit, Centre Pasteur Cameroon, P.O. Box 1274, Yaoundé, Cameroon.
- Department of Biological Sciences, Faculty of Medicine and Pharmaceutical Sciences, The University of Douala, P.O. Box 2701, Douala, Cameroon.
- Laboratory of Parasitology, Mycology and Virology, Postgraduate Training Unit for Health Sciences, Postgraduate School for Pure and Applied Sciences, The University of Douala, P.O. Box 2701, Douala, Cameroon.
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Elamin EM, Eshage SE, Mohmmode SM, Mukhtar RM, Mahjoub M, Sadelin E, Shoaib TH, Edris A, Elshamly EM, Makki AA, Ashour A, Sherif AE, Osman W, Ibrahim SRM, Mohamed GA, Alzain AA. Discovery of dual-target natural antimalarial agents against DHODH and PMT of Plasmodium falciparum: pharmacophore modelling, molecular docking, quantum mechanics, and molecular dynamics simulations. SAR AND QSAR IN ENVIRONMENTAL RESEARCH 2023; 34:709-728. [PMID: 37665563 DOI: 10.1080/1062936x.2023.2251876] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2023] [Accepted: 08/18/2023] [Indexed: 09/05/2023]
Abstract
Malaria is a lethal disease that claims thousands of lives worldwide annually. The objective of this study was to identify new natural compounds that can target two P. falciparum enzymes; P. falciparum Dihydroorotate dehydrogenase (PfDHODH) and P. falciparum phosphoethanolamine methyltransferase (PfPMT). To accomplish this, e-pharmacophore modelling and molecular docking were employed against PfDHODH. Following this, 1201 natural compounds with docking scores of ≤ -7 kcal/mol were docked into the active site of the second enzyme PMT. The top nine compounds were subjected to further investigation using MM-GBSA free binding energy calculations and ADME analysis. The results revealed favourable free binding energy values better than the references, as well as acceptable pharmacokinetic properties. Compounds ZINC000013377887, ZINC000015113777, and ZINC000085595753 were scrutinized to assess their interaction stability with the PfDHODH enzyme, and chemical stability reactivity using molecular dynamics (MD) simulation and density functional theory (DFT) calculations. These findings indicate that the three natural compounds are potential candidates for dual PfDHODH and PfPMT inhibitors for malaria treatment.
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Affiliation(s)
- E M Elamin
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Gezira, Gezira, Sudan
| | - S E Eshage
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Gezira, Gezira, Sudan
| | - S M Mohmmode
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Gezira, Gezira, Sudan
| | - R M Mukhtar
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Gezira, Gezira, Sudan
| | - M Mahjoub
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Gezira, Gezira, Sudan
| | - E Sadelin
- Department of Pharmaceutics, Faculty of Pharmacy, University of Gezira, Gezira, Sudan
| | - T H Shoaib
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Gezira, Gezira, Sudan
| | - A Edris
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Gezira, Gezira, Sudan
| | - E M Elshamly
- Department of Molecular Biotechnology, Hochschule Anhalt, Köthen, Germany
| | - A A Makki
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Gezira, Gezira, Sudan
| | - A Ashour
- Department of Pharmacognosy, Faculty of Pharmacy, Prince Sattam Bin Abdulaziz University, AlKharj, Saudi Arabia
- Department of Pharmacognosy, Faculty of Pharmacy, Mansoura University, Al Mansurah, Egypt
| | - A E Sherif
- Department of Pharmacognosy, Faculty of Pharmacy, Prince Sattam Bin Abdulaziz University, AlKharj, Saudi Arabia
- Department of Pharmacognosy, Faculty of Pharmacy, Mansoura University, Al Mansurah, Egypt
| | - W Osman
- Department of Pharmacognosy, Faculty of Pharmacy, Prince Sattam Bin Abdulaziz University, AlKharj, Saudi Arabia
- Department of Pharmacognosy, Faculty of Pharmacy, University of Khartoum, Khartoum, Sudan
| | - S R M Ibrahim
- Preparatory Year Program, Department of Chemistry, Batterjee Medical College, Jeddah, Saudi Arabia
- Department of Pharmacognosy, Faculty of Pharmacy, Assiut University, Assiut, Egypt
| | - G A Mohamed
- Department of Natural Products and Alternative Medicine, Faculty of Pharmacy, King Abdulaziz University, Jeddah, Saudi Arabia
| | - A A Alzain
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Gezira, Gezira, Sudan
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A single dose of genetically-attenuated malaria blood-stage parasites protects against two Plasmodium species infections. Vaccine 2023; 41:1281-1285. [PMID: 36653222 DOI: 10.1016/j.vaccine.2023.01.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 10/31/2022] [Accepted: 01/03/2023] [Indexed: 01/18/2023]
Abstract
Genetically-growth-attenuated blood-stage parasites were generated inPlasmodium falciparumby targeted deletion of NT1 (Nucleoside Transporter-1) gene, and Pfnt1(-) parasites only grew after providing the culture with supra-physiological concentrations of purines. Genetically-attenuatedP. yoeliint1(-)parasites induced sterile-protection against homologous blood-stage infectious challenge after immunization with single subpatent doses, which remained subpatent even in immune-compromised mice. Here, we showed that immunizations with frozen-stocks of equally-mixedP. bergheiandP. yoelii nt1(-)parasites in single subcutaneous doses, which did not lead to patent blood-stage infection, conferred sterile protection against intravenous infectious blood-stage challenge with wild-type parasites ofP. bergheiANKA andP. yoelii17X-NL strains. This data highlights the possibility that a single subcutaneous sub-patent dose of two species of genetically-growth-attenuated parasites, which can protect humans against twoPlasmodiumspp. infections, could be developed in cultures provided with supra-physiological concentrations of purines, and shipped to endemic areas as frozen-stock doses.
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Lê HG, Naw H, Kang JM, Võ TC, Myint MK, Htun ZT, Lee J, Yoo WG, Kim TS, Shin HJ, Na BK. Molecular Profiles of Multiple Antimalarial Drug Resistance Markers in Plasmodium falciparum and Plasmodium vivax in the Mandalay Region, Myanmar. Microorganisms 2022; 10:2021. [PMID: 36296297 PMCID: PMC9612053 DOI: 10.3390/microorganisms10102021] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Revised: 10/05/2022] [Accepted: 10/08/2022] [Indexed: 09/21/2023] Open
Abstract
Emergence and spreading of antimalarial drug resistant malaria parasites are great hurdles to combating malaria. Although approaches to investigate antimalarial drug resistance status in Myanmar malaria parasites have been made, more expanded studies are necessary to understand the nationwide aspect of antimalarial drug resistance. In the present study, molecular epidemiological analysis for antimalarial drug resistance genes in Plasmodium falciparum and P. vivax from the Mandalay region of Myanmar was performed. Blood samples were collected from patients infected with P. falciparum and P. vivax in four townships around the Mandalay region, Myanmar in 2015. Partial regions flanking major mutations in 11 antimalarial drug resistance genes, including seven genes (pfdhfr, pfdhps, pfmdr-1, pfcrt, pfk13, pfubp-1, and pfcytb) of P. falciparum and four genes (pvdhfr, pvdhps, pvmdr-1, and pvk12) of P. vivax were amplified, sequenced, and overall mutation patterns in these genes were analyzed. Substantial levels of mutations conferring antimalarial drug resistance were detected in both P. falciparum and P. vivax isolated in Mandalay region of Myanmar. Mutations associated with sulfadoxine-pyrimethamine resistance were found in pfdhfr, pfdhps, pvdhfr, and pvdhps of Myanmar P. falciparum and P. vivax with very high frequencies up to 90%. High or moderate levels of mutations were detected in genes such as pfmdr-1, pfcrt, and pvmdr-1 associated with chloroquine resistance. Meanwhile, low frequency mutations or none were found in pfk13, pfubp-1, pfcytb, and pvk12 of the parasites. Overall molecular profiles for antimalarial drug resistance genes in malaria parasites in the Mandalay region suggest that parasite populations in the region have substantial levels of mutations conferring antimalarial drug resistance. Continuous monitoring of mutations linked with antimalarial drug resistance is necessary to provide useful information for policymakers to plan for proper antimalarial drug regimens to control and eliminate malaria in the country.
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Affiliation(s)
- Hương Giang Lê
- Department of Parasitology and Tropical Medicine, Institute of Health Sciences, Gyeongsang National University College of Medicine, Jinju 52727, Korea
- Department of Convergence Medical Science, Gyeongsang National University, Jinju 52727, Korea
| | - Haung Naw
- Department of Parasitology and Tropical Medicine, Institute of Health Sciences, Gyeongsang National University College of Medicine, Jinju 52727, Korea
- Department of Convergence Medical Science, Gyeongsang National University, Jinju 52727, Korea
| | - Jung-Mi Kang
- Department of Parasitology and Tropical Medicine, Institute of Health Sciences, Gyeongsang National University College of Medicine, Jinju 52727, Korea
- Department of Convergence Medical Science, Gyeongsang National University, Jinju 52727, Korea
| | - Tuấn Cường Võ
- Department of Parasitology and Tropical Medicine, Institute of Health Sciences, Gyeongsang National University College of Medicine, Jinju 52727, Korea
- Department of Convergence Medical Science, Gyeongsang National University, Jinju 52727, Korea
| | - Moe Kyaw Myint
- Department of Medical Research Pyin Oo Lwin Branch, Pyin Oo Lwin 05062, Myanmar
| | - Zaw Than Htun
- Department of Medical Research Pyin Oo Lwin Branch, Pyin Oo Lwin 05062, Myanmar
| | - Jinyoung Lee
- Department of Tropical Medicine, Inha Research Institute for Medical Sciences, Inha University College of Medicine, Incheon 22212, Korea
| | - Won Gi Yoo
- Department of Parasitology and Tropical Medicine, Institute of Health Sciences, Gyeongsang National University College of Medicine, Jinju 52727, Korea
- Department of Convergence Medical Science, Gyeongsang National University, Jinju 52727, Korea
| | - Tong-Soo Kim
- Department of Tropical Medicine, Inha Research Institute for Medical Sciences, Inha University College of Medicine, Incheon 22212, Korea
| | - Ho-Joon Shin
- Department of Microbiology, Ajou University College of Medicine, Suwon 16499, Korea
| | - Byoung-Kuk Na
- Department of Parasitology and Tropical Medicine, Institute of Health Sciences, Gyeongsang National University College of Medicine, Jinju 52727, Korea
- Department of Convergence Medical Science, Gyeongsang National University, Jinju 52727, Korea
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Venter F, Matthews KR, Silvester E. Parasite co-infection: an ecological, molecular and experimental perspective. Proc Biol Sci 2022; 289:20212155. [PMID: 35042410 PMCID: PMC8767208 DOI: 10.1098/rspb.2021.2155] [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] [Indexed: 11/12/2022] Open
Abstract
Laboratory studies of pathogens aim to limit complexity in order to disentangle the important parameters contributing to an infection. However, pathogens rarely exist in isolation, and hosts may sustain co-infections with multiple disease agents. These interact with each other and with the host immune system dynamically, with disease outcomes affected by the composition of the community of infecting pathogens, their order of colonization, competition for niches and nutrients, and immune modulation. While pathogen-immune interactions have been detailed elsewhere, here we examine the use of ecological and experimental studies of trypanosome and malaria infections to discuss the interactions between pathogens in mammal hosts and arthropod vectors, including recently developed laboratory models for co-infection. The implications of pathogen co-infection for disease therapy are also discussed.
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Affiliation(s)
- Frank Venter
- Institute for Immunology and Infection Research, Ashworth Laboratories, School of Biological Sciences, University of Edinburgh, Scotland EH9 3FL, UK
| | - Keith R Matthews
- Institute for Immunology and Infection Research, Ashworth Laboratories, School of Biological Sciences, University of Edinburgh, Scotland EH9 3FL, UK
| | - Eleanor Silvester
- Institute for Immunology and Infection Research, Ashworth Laboratories, School of Biological Sciences, University of Edinburgh, Scotland EH9 3FL, UK.,Cambridge Institute for Medical Research, University of Cambridge, Cambridge Biomedical Campus, The Keith Peters Building, Hills Road, Cambridge CB2 0XY, UK
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Mahittikorn A, Masangkay FR, Kotepui KU, Milanez GDJ, Kotepui M. The high risk of malarial recurrence in patients with Plasmodium-mixed infection after treatment with antimalarial drugs: a systematic review and meta-analysis. Parasit Vectors 2021; 14:280. [PMID: 34034802 PMCID: PMC8145851 DOI: 10.1186/s13071-021-04792-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Accepted: 05/11/2021] [Indexed: 11/29/2022] Open
Abstract
Background Malaria mixed infections are often unrecognized by microscopists in the hospitals, and a delay or failure to treat Plasmodium-mixed infection may lead to aggravated morbidity and increased mortality. The present study aimed to quantify the pooled proportion and risk of malarial recurrences after the treatment of Plasmodium-mixed infection. The results of the study may provide benefits in the management of Plasmodium-mixed infection in co-endemic regions. Methods This systematic review and meta-analysis searched the international Prospective Register of Systematic Reviews (PROSPERO; ID = CRD42020199709), MEDLINE, Web of Science, and Scopus for potentially relevant studies in any language published between January 1, 1936, and July 20, 2020, assessing drug efficacy in patients with Plasmodium-mixed infection. The primary outcome was the pooled prevalence of Plasmodium parasitemia after initiating antimalarial treatment for Plasmodium-mixed infection. The secondary outcome was the pooled risk ratio (RR) of malarial recurrence in Plasmodium-mixed infection compared with those in Plasmodium falciparum and Plasmodium vivax mono-infection. The pooled analyses were calculated by random-effects meta-analysis. After the initial treatment in different days of recurrences (≤ 28 days or > 28 days), the risk of Plasmodium parasitemia was compared in subgroup analysis. Results Out of 5217 screened studies, 11 were included in the meta-analysis, including 4390 patients from six countries. The pooled prevalence of all recurrences of Plasmodium-mixed parasitemia was 30% (95% confidence interval (CI) 16–43; I2: 99.2%; 11 studies). The RR of malarial recurrence within 28 days after the initial treatment (clinical treatment failure) of Plasmodium-mixed parasitemia compared with the treatment of P. falciparum was 1.22 (p: 0.029; 95% CI 1.02–1.47; Cochran Q: 0.93; I2: 0%; six studies), while there was no significant difference in the risk of recurrence 28 days after initial treatment compared with the treatment of P. falciparum (p: 0.696, RR: 1.14; 95% CI 0.59–2.18; Cochran Q < 0.05; I2: 98.2%; four studies). The subgroup analysis of antimalarial drugs showed that significant malarial recurrence within 28 days was observed in patients treated with artemisinin-based combination therapies (ACTs) with no significant heterogeneity (p: 0.028, RR: 1.31; 95% CI 1.03–1.66; Cochran Q: 0.834; I2: 0%). Conclusions The present findings showed a high prevalence of malarial recurrence after the initial treatment of Plasmodium-mixed infection. Moreover, significant malaria recurrence of mixed infection occurred within 28 days after treatment with ACTs. Graphic Abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1186/s13071-021-04792-5.
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Affiliation(s)
- Aongart Mahittikorn
- Department of Protozoology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Frederick Ramirez Masangkay
- Department of Medical Technology, Institute of Arts and Sciences, Far Eastern University-Manila, Manila, Philippines
| | - Kwuntida Uthaisar Kotepui
- Medical Technology, School of Allied Health Sciences, Walailak University, Tha Sala, Nakhon Si Thammarat, Thailand
| | - Giovanni De Jesus Milanez
- Department of Medical Technology, Institute of Arts and Sciences, Far Eastern University-Manila, Manila, Philippines
| | - Manas Kotepui
- Medical Technology, School of Allied Health Sciences, Walailak University, Tha Sala, Nakhon Si Thammarat, Thailand.
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Paengsri W, Promsawan N, Baramee A. Synthesis and Evaluation of 2-Hydroxy-1,4-naphthoquinone Derivatives as Potent Antimalarial Agents. Chem Pharm Bull (Tokyo) 2021; 69:253-257. [PMID: 33431728 DOI: 10.1248/cpb.c20-00770] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A series of 3-substituted-2-hydroxy-1,4-naphthoquinone derivatives with a variety of side chains were successfully synthesized by Mannich reaction of 2-hydroxy-1,4-naphthoquinone (lawsone) with selected amines and aldehydes. All substances (1-16) were evaluated for in-vitro antimalarial activity against strains of Plasmodium falciparum by microculture radioisotope technique. Bioassay data revealed that ten derivatives (1-8, 11 and 13) displayed significantly good activity with values of IC50 ranging from 0.77 to 4.05 µg/mL. The best biological profile (IC50 = 0.77 µg/mL) was observed in compound 1, possessing a n-butyl substituted aminomethyl group. Experimental results support the potential use of our active Mannich components as promising antimalarial agents in the fight against malaria infections and multidrug resistance problems.
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Affiliation(s)
- Wanthani Paengsri
- Department of Chemistry, Faculty of Science, Chiang Mai Universit.,Center of Excellence for Innovation in Chemistry, Faculty of Science, Chiang Mai University
| | | | - Apiwat Baramee
- Department of Chemistry, Faculty of Science, Chiang Mai Universit
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High Plasmodium infection intensity in naturally infected malaria vectors in Africa. Int J Parasitol 2020; 50:985-996. [PMID: 32681932 DOI: 10.1016/j.ijpara.2020.05.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 05/14/2020] [Accepted: 05/17/2020] [Indexed: 01/18/2023]
Abstract
The population dynamics of human to mosquito malaria transmission in the field has important implications for the genetics, epidemiology and control of malaria. The number of oocysts in oocyst-positive mosquitoes developing from a single, naturally acquired infectious blood meal (herein referred to as a single-feed infection load) greatly influences the efficacy of transmission blocking interventions but still remains poorly documented. During a year-long analysis of malaria parasite transmission in Burkina Faso we caught and dissected wild malaria vectors to assess Plasmodium oocyst prevalence and load (the number of oocysts counted in mosquitoes with detectable oocysts) and the prevalence of salivary gland sporozoites. This was compared with malaria endemicity in the human population, assessed in cross-sectional surveys. Data were analysed using a novel transmission mathematical model to estimate the per bite transmission probability and the average single-feed infection load for each location. The observed oocyst load and the estimated single-feed infection load in naturally infected mosquitoes were substantially higher than previous estimates (means ranging from 3.2 to 24.5 according to seasons and locations) and indicate a strong positive association between the single-feed infection load and parasite prevalence in humans. This work suggests that highly infected mosquitoes are not rare in the field and might have a greater influence on the epidemiology and genetics of the parasite, and on the efficacy of novel transmission blocking interventions.
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Tang J, Templeton TJ, Cao J, Culleton R. The Consequences of Mixed-Species Malaria Parasite Co-Infections in Mice and Mosquitoes for Disease Severity, Parasite Fitness, and Transmission Success. Front Immunol 2020; 10:3072. [PMID: 32038623 PMCID: PMC6987389 DOI: 10.3389/fimmu.2019.03072] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2019] [Accepted: 12/16/2019] [Indexed: 11/13/2022] Open
Abstract
The distributions of human malaria parasite species overlap in most malarious regions of the world, and co-infections involving two or more malaria parasite species are common. Little is known about the consequences of interactions between species during co-infection for disease severity and parasite transmission success. Anti-malarial interventions can have disproportionate effects on malaria parasite species and may locally differentially reduce the number of species in circulation. Thus, it is important to have a clearer understanding of how the interactions between species affect disease and transmission dynamics. Controlled competition experiments using human malaria parasites are impossible, and thus we assessed the consequences of mixed-species infections on parasite fitness, disease severity, and transmission success using the rodent malaria parasite species Plasmodium chabaudi, Plasmodium yoelii, and Plasmodium vinckei. We compared the fitness of individual species within single species and co-infections in mice. We also assessed the disease severity of single vs. mixed infections in mice by measuring mortality rates, anemia, and weight loss. Finally, we compared the transmission success of parasites in single or mixed species infections by quantifying oocyst development in Anopheles stephensi mosquitoes. We found that co-infections of P. yoelii with either P. vinckei or P. chabaudi led to a dramatic increase in infection virulence, with 100% mortality observed in mixed species infections, compared to no mortality for P. yoelii and P. vinckei single infections, and 40% mortality for P. chabaudi single infections. The increased mortality in the mixed infections was associated with an inability to clear parasitaemia, with the non-P. yoelii parasite species persisting at higher parasite densities than in single infections. P. yoelii growth was suppressed in all mixed infections compared to single infections. Transmissibility of P. vinckei and P. chabaudi to mosquitoes was also reduced in the presence of P. yoelii in co-infections compared to single infections. The increased virulence of co-infections containing P. yoelii (reticulocyte restricted) and P. chabaudi or P. vinckei (predominantly normocyte restricted) may be due to parasite cell tropism and/or immune modulation of the host. We explain the reduction in transmission success of species in co-infections in terms of inter-species gamete incompatibility.
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Affiliation(s)
- Jianxia Tang
- National Health Commission Key Laboratory of Parasitic Disease Control and Prevention, Jiangsu Provincial Key Laboratory on Parasite and Vector Control Technology, Jiangsu Institute of Parasitic Diseases, Wuxi, China.,Malaria Unit, Department of Pathology, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
| | - Thomas J Templeton
- Department of Protozoology, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
| | - Jun Cao
- National Health Commission Key Laboratory of Parasitic Disease Control and Prevention, Jiangsu Provincial Key Laboratory on Parasite and Vector Control Technology, Jiangsu Institute of Parasitic Diseases, Wuxi, China
| | - Richard Culleton
- Malaria Unit, Department of Pathology, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
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10
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Balasubramanian S, Rahman RS, Lon C, Parobek C, Ubalee R, Hathaway N, Kuntawunginn W, My M, Vy D, Saxe J, Lanteri C, Lin FC, Spring M, Meshnick SR, Juliano JJ, Saunders DL, Lin JT. Efficient Transmission of Mixed Plasmodium falciparum/vivax Infections From Humans to Mosquitoes. J Infect Dis 2020; 221:428-437. [PMID: 31549156 PMCID: PMC7184918 DOI: 10.1093/infdis/jiz388] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Accepted: 07/23/2019] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND In Southeast Asia, people are often coinfected with different species of malaria (Plasmodium falciparum [Pf] and Plasmodium vivax [Pv]) as well as with multiple clones of the same species. Whether particular species or clones within mixed infections are more readily transmitted to mosquitoes remains unknown. METHODS Laboratory-reared Anopheles dirus were fed on blood from 119 Pf-infected Cambodian adults, with 5950 dissected to evaluate for transmitted infection. Among 12 persons who infected mosquitoes, polymerase chain reaction and amplicon deep sequencing were used to track species and clone-specific transmission to mosquitoes. RESULTS Seven of 12 persons that infected mosquitoes harbored mixed Pf/Pv infection. Among these 7 persons, all transmitted Pv with 2 transmitting both Pf and Pv, leading to Pf/Pv coinfection in 21% of infected mosquitoes. Up to 4 clones of each species were detected within persons. Shifts in clone frequency were detected during transmission. However, in general, all parasite clones in humans were transmitted to mosquitoes, with individual mosquitoes frequently carrying multiple transmitted clones. CONCLUSIONS Malaria diversity in human hosts was maintained in the parasite populations recovered from mosquitoes fed on their blood. However, in persons with mixed Pf/Pv malaria, Pv appears to be transmitted more readily, in association with more prevalent patent gametocytemia.
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Affiliation(s)
- Sujata Balasubramanian
- Institute of Global Health and Infectious Diseases, University of North Carolina, Chapel Hill
| | - Rifat S Rahman
- Institute of Global Health and Infectious Diseases, University of North Carolina, Chapel Hill
| | - Chanthap Lon
- Armed Forces Research Institute of Medical Sciences, Phnom Penh, Cambodia
| | - Christian Parobek
- Institute of Global Health and Infectious Diseases, University of North Carolina, Chapel Hill
| | - Ratawan Ubalee
- Department of Entomology, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Nicholas Hathaway
- Department of Bioinformatics and Integrated Biology, University of Massachusetts, Worcester
| | - Worachet Kuntawunginn
- Department of Bacterial and Parasitic Diseases, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Mok My
- Royal Cambodian Armed Forces, Phnom Penh, Cambodia
| | - Dav Vy
- Royal Cambodian Armed Forces, Phnom Penh, Cambodia
| | - Jeremy Saxe
- Department of Biostatistics, Gillings School of Global Public Health, University of North Carolina, Chapel Hill
| | - Charlotte Lanteri
- Department of Bacterial and Parasitic Diseases, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Feng-Chang Lin
- Department of Biostatistics, Gillings School of Global Public Health, University of North Carolina, Chapel Hill
| | - Michele Spring
- Department of Bacterial and Parasitic Diseases, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Steven R Meshnick
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill
| | - Jonathan J Juliano
- Institute of Global Health and Infectious Diseases, University of North Carolina, Chapel Hill
| | - David L Saunders
- Department of Bacterial and Parasitic Diseases, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
- US Army Medical Materiel Development Activity, Fort Detrick, Maryland
| | - Jessica T Lin
- Institute of Global Health and Infectious Diseases, University of North Carolina, Chapel Hill
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11
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von Seidlein L, Peerawaranun P, Mukaka M, Nosten FH, Nguyen TN, Hien TT, Tripura R, Peto TJ, Pongvongsa T, Phommasone K, Mayxay M, Imwong M, Watson J, Pukrittayakamee S, Day NPJ, Dondorp AM. The probability of a sequential Plasmodium vivax infection following asymptomatic Plasmodium falciparum and P. vivax infections in Myanmar, Vietnam, Cambodia, and Laos. Malar J 2019; 18:449. [PMID: 31888643 PMCID: PMC6937799 DOI: 10.1186/s12936-019-3087-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Accepted: 12/21/2019] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND Adding 8-aminoquinoline to the treatment of falciparum, in addition to vivax malaria, in locations where infections with both species are prevalent could prevent vivax reactivation. The potential risk of haemolysis under a universal radical cure policy using 8-aminoquinoline needs to be weighed against the benefit of preventing repeated vivax episodes. Estimating the frequency of sequential Plasmodium vivax infections following either falciparum or vivax malaria episodes is needed for such an assessment. METHODS Quarterly surveillance data collected during a mass drug administration trial in the Greater Mekong Subregion in 2013-17 was used to estimate the probability of asymptomatic sequential infections by the same and different Plasmodium species. Asymptomatic Plasmodium infections were detected by high-volume ultrasensitive qPCR. Quarterly surveys of asymptomatic Plasmodium prevalence were used to estimate the probability of a P. vivax infection following Plasmodium falciparum and P. vivax infections. RESULTS 16,959 valid sequential paired test results were available for analysis. Of these, 534 (3%) had an initial P. falciparum monoinfection, 1169 (7%) a P. vivax monoinfection, 217 (1%) had mixed (P. falciparum + P. vivax) infections, and 15,039 (89%) had no Plasmodium detected in the initial survey. Participants who had no evidence of a Plasmodium infection had a 4% probability to be found infected with P. vivax during the subsequent survey. Following an asymptomatic P. falciparum monoinfection participants had a 9% probability of having a subsequent P. vivax infection (RR 2.4; 95% CI 1.8 to 3.2). Following an asymptomatic P. vivax monoinfection, the participants had a 45% probability of having a subsequent P. vivax infection. The radical cure of 12 asymptomatic P. falciparum monoinfections would have prevented one subsequent P. vivax infection, whereas treatment of 2 P. vivax monoinfections may suffice to prevent one P. vivax relapse. CONCLUSION Universal radical cure could play a role in the elimination of vivax malaria. The decision whether to implement universal radical cure for P. falciparum as well as for P. vivax depends on the prevalence of P. falciparum and P. vivax infections, the prevalence and severity of G6PD deficiency in the population and the feasibility to administer 8-aminoquinoline regimens safely. Trial registration ClinicalTrials.gov Identifier: NCT01872702, first posted June 7th 2013, https://clinicaltrials.gov/ct2/show/NCT01872702. This study was registered with ClinicalTrials.gov under NCT02802813 on 16th June 2016. https://clinicaltrials.gov/ct2/show/NCT02802813.
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Affiliation(s)
- Lorenz von Seidlein
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK.
| | - Pimnara Peerawaranun
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Mavuto Mukaka
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Francois H Nosten
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
- MShoklo Malaria Research Unit, Mae Sot, Thailand
| | - Thuy-Nhien Nguyen
- Oxford University Clinical Research Unit, Wellcome Trust Major Oversea Programme, Ho Chi Minh City, Vietnam
| | - Tran Tinh Hien
- Oxford University Clinical Research Unit, Wellcome Trust Major Oversea Programme, Ho Chi Minh City, Vietnam
| | - Rupam Tripura
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
- Center of Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Amsterdam University Medical Centers, Meibergdreef, 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 Medicine, University of Oxford, Oxford, UK
| | - Tiengkham Pongvongsa
- Savannakhet Provincial Health Department, Savannakhet, Savannakhet Province, Lao PDR
- Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Koukeo Phommasone
- Lao-Oxford-Mahosot Hospital-Wellcome Trust Research Unit (LOMWRU), Microbiology Laboratory, Mahosot Hospital, Vientiane, Lao PDR
- Amsterdam Institute for Global Health & Development, AHTC, Amsterdam, Netherlands
| | - Mayfong Mayxay
- Lao-Oxford-Mahosot Hospital-Wellcome Trust Research Unit (LOMWRU), Microbiology Laboratory, Mahosot Hospital, Vientiane, Lao PDR
- Institute of Research and Education Development, University of Health Sciences, Vientiane, Lao PDR
| | - Mallika Imwong
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Department of Molecular Tropical Medicine and Genetics, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - James Watson
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Sasithon Pukrittayakamee
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- The Royal Society of Thailand, Dusit, Bangkok, Thailand
| | - Nicholas P J Day
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, 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 Medicine, University of Oxford, Oxford, UK
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12
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Ashley EA, Phyo AP, Carrara VI, Tun KM, Nosten F, Smithuis F, White NJ. Plasmodium vivax Relapse Rates Following Plasmodium falciparum Malaria Reflect Previous Transmission Intensity. J Infect Dis 2019; 220:100-104. [PMID: 30698794 PMCID: PMC6548896 DOI: 10.1093/infdis/jiz052] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Accepted: 01/28/2019] [Indexed: 11/13/2022] Open
Abstract
From 2003 through 2009, 687 of 2885 patients (23.8%) treated for Plasmodium falciparum malaria in clinical studies in Myanmar or on the Thailand-Myanmar border had recurrent Plasmodium vivax malaria within 63 days, compared with 18 of 429 patients (4.2%) from 2010 onward (risk ratio [RR], 0.176; 95% confidence interval, .112-.278; P < .0001). Corresponding data from 42 days of follow-up revealed that 820 of 3883 patients (21.1%) had recurrent P. vivax malaria before 2010, compared with 22 of 886 (2.5%) from 2010 onward (RR, 0.117; 95% CI, .077-.177; P < .0001). This 6-fold reduction suggests a recent decline in P. vivax transmission intensity and, thus, a substantial reduction in the proportion of individuals harboring hypnozoites.
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Affiliation(s)
- Elizabeth A Ashley
- Myanmar Oxford Clinical Research Unit, Myanmar
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, United Kingdom
| | - Aung Pyae Phyo
- Myanmar Oxford Clinical Research Unit, Myanmar
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot
| | - Verena I Carrara
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot
| | - Kyaw Myo Tun
- Department of Preventive and Social Medicine, Defence Services Medical Academy
| | - Francois Nosten
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, United Kingdom
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot
| | - Frank Smithuis
- Myanmar Oxford Clinical Research Unit, Myanmar
- Medical Action Myanmar, Yangon, Myanmar
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, United Kingdom
| | - 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, Bangkok, Thailand
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13
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Commons RJ, Simpson JA, Thriemer K, Hossain MS, Douglas NM, Humphreys GS, Sibley CH, Guerin PJ, Price RN. Risk of Plasmodium vivax parasitaemia after Plasmodium falciparum infection: a systematic review and meta-analysis. THE LANCET. INFECTIOUS DISEASES 2019; 19:91-101. [PMID: 30587297 PMCID: PMC6300482 DOI: 10.1016/s1473-3099(18)30596-6] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 09/11/2018] [Accepted: 09/13/2018] [Indexed: 01/12/2023]
Abstract
BACKGROUND A 14-day course of primaquine is used for radical cure of Plasmodium vivax and Plasmodium ovale malaria only. We quantified the risk of P vivax parasitaemia after treatment of Plasmodium falciparum with commonly used antimalarial drugs to assess the potential benefits of radical cure for all patients with uncomplicated malaria in co-endemic regions. METHODS In this systematic review and meta-analysis, we searched MEDLINE, Embase, Web of Science, and the Cochrane Database of Systematic Reviews for prospective clinical studies in any language, published between Jan 1, 1960, and Jan 5, 2018, assessing drug efficacy in patients with uncomplicated P falciparum malaria in countries co-endemic for P vivax. Studies were included if the presence or absence of P vivax parasitaemia was recorded after treatment. The primary outcome was the risk of P vivax parasitaemia between day 7 and day 42 after initiation of antimalarial treatment for P falciparum, with the pooled risk calculated by random-effects meta-analysis. We compared the risk of P vivax parasitaemia after treatment with different artemisinin-based combination therapies (ACTs). This study is registered with PROSPERO, number CRD42017064838. FINDINGS 153 of 891 screened studies were included in the analysis, including 31 262 patients from 323 site-specific treatment groups: 130 (85%) studies were from the Asia-Pacific region, 16 (10%) from the Americas, and seven (5%) from Africa. The risk of P vivax parasitaemia by day 42 was 5·6% (95% CI 4·0-7·4; I2=92·0%; 117 estimates). The risk of P vivax parasitaemia was 6·5% (95% CI 4·6-8·6) in regions of short relapse periodicity compared with 1·9% (0·4-4·0) in regions of long periodicity, and was greater after treatment with a more rapidly eliminated ACT: 15·3% (5·1-29·3) for artemether-lumefantrine compared with 4·5% (1·2-9·3) for dihydroartemisinin-piperaquine and 5·2% (2·9-7·9) for artesunate-mefloquine. Recurrent parasitaemia was delayed in patients treated with ACTs containing mefloquine or piperaquine compared with artemether-lumefantrine, but by day 63 the risk of vivax parasitaemia was more than 15% for all ACTs assessed. INTERPRETATION Our findings show a high risk of vivax parasitaemia after treatment of falciparum malaria, particularly in areas with short relapse periodicity and after rapidly eliminated treatment. In co-endemic regions, universal radical cure for all patients with uncomplicated malaria has the potential to substantially reduce recurrent malaria. FUNDING Australian National Health and Medical Research Council, Royal Australasian College of Physicians, Wellcome Trust, and Bill & Melinda Gates Foundation.
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Affiliation(s)
- Robert J Commons
- Global Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, NT, Australia; WorldWide Antimalarial Resistance Network, Oxford, UK.
| | - Julie A Simpson
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, VIC, Australia
| | - Kamala Thriemer
- Global Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, NT, Australia
| | - Mohammad S Hossain
- Global Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, NT, Australia; WorldWide Antimalarial Resistance Network, Oxford, UK; Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, VIC, Australia; International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh
| | - Nicholas M Douglas
- Global Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, NT, Australia; Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, VIC, Australia
| | - Georgina S Humphreys
- WorldWide Antimalarial Resistance Network, Oxford, UK; Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Carol H Sibley
- WorldWide Antimalarial Resistance Network, Oxford, UK; Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK; Department of Genome Sciences, University of Washington, Seattle, WA, USA
| | - Philippe J Guerin
- WorldWide Antimalarial Resistance Network, Oxford, UK; Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Ric N Price
- Global Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, NT, Australia; WorldWide Antimalarial Resistance Network, Oxford, UK; Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
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14
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Plasmodium genomics: an approach for learning about and ending human malaria. Parasitol Res 2018; 118:1-27. [PMID: 30402656 DOI: 10.1007/s00436-018-6127-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Accepted: 10/19/2018] [Indexed: 12/31/2022]
Abstract
Malaria causes high levels of morbidity and mortality in human beings worldwide. According to the World Health Organization (WHO), about half a million people die of this disease each year. Malaria is caused by six species of parasites belonging to the Plasmodium genus: P. falciparum, P. knowlesi, P. vivax, P. malariae, P. ovale curtisi, and P. ovale wallikeri. Currently, malaria is being kept under control with varying levels of elimination success in different countries. The development of new molecular tools as well as the use of next-generation sequencing (NGS) technologies and novel bioinformatic approaches has improved our knowledge of malarial epidemiology, diagnosis, treatment, vaccine development, and surveillance strategies. In this work, the genetics and genomics of human malarias have been analyzed. Since the first P. falciparum genome was sequenced in 2002, various population-level genetic and genomic surveys, together with transcriptomic and proteomic studies, have shown the importance of molecular approaches in supporting malaria elimination.
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15
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Umer MF, Zofeen S, Majeed A, Hu W, Qi X, Zhuang G. Spatiotemporal Clustering Analysis of Malaria Infection in Pakistan. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2018; 15:E1202. [PMID: 29880778 PMCID: PMC6025434 DOI: 10.3390/ijerph15061202] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 05/24/2018] [Accepted: 06/04/2018] [Indexed: 11/21/2022]
Abstract
Despite tremendous progress, malaria remains a serious public health problem in Pakistan. Very few studies have been done on spatiotemporal evaluation of malaria infection in Pakistan. The study aimed to detect the spatiotemporal pattern of malaria infection at the district level in Pakistan, and to identify the clusters of high-risk disease areas in the country. Annual data on malaria for two dominant species (Plasmodium falciparum, Plasmodium vivax) and mixed infections from 2011 to 2016 were obtained from the Directorate of Malaria Control Program, Pakistan. Population data were collected from the Pakistan Bureau of Statistics. A geographical information system was used to display the spatial distribution of malaria at the district level throughout Pakistan. Purely spatiotemporal clustering analysis was performed to identify the high-risk areas of malaria infection in Pakistan. A total of 1,593,409 positive cases were included in this study over a period of 6 years (2011⁻2016). The maximum number of P. vivax cases (474,478) were reported in Khyber Pakhtunkhwa (KPK). The highest burden of P. falciparum (145,445) was in Balochistan, while the highest counts of mixed Plasmodium cases were reported in Sindh (22,421) and Balochistan (22,229), respectively. In Balochistan, incidence of all three types of malaria was very high. Cluster analysis showed that primary clusters of P. vivax malaria were in the same districts in 2014, 2015 and 2016 (total 24 districts, 12 in Federally Administered Tribal Areas (FATA), 9 in KPK, 2 in Punjab and 1 in Balochistan); those of P. falciparum malaria were unchanged in 2012 and 2013 (total 18 districts, all in Balochistan), and mixed infections remained the same in 2014 and 2015 (total 7 districts, 6 in Balochistan and 1 in FATA). This study indicated that the transmission cycles of malaria infection vary in different spatiotemporal settings in Pakistan. Efforts in controlling P. vivax malaria in particular need to be enhanced in high-risk areas. Based on these findings, further research is needed to investigate the impact of risk factors on transmission of malaria in Pakistan.
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Affiliation(s)
- Muhammad Farooq Umer
- School of Public Health, Xi'an Jiaotong University Health Science Center, Xi'an 710061, China.
| | - Shumaila Zofeen
- School of Public Health, Xi'an Jiaotong University Health Science Center, Xi'an 710061, China.
| | - Abdul Majeed
- Directorate of Malaria Control Program, Islamabad 44000, Pakistan.
| | - Wenbiao Hu
- School of Public Health and Social Work, Queensland University of Technology, Kelvin Grove, QLD 4059, Australia.
| | - Xin Qi
- School of Public Health, Xi'an Jiaotong University Health Science Center, Xi'an 710061, China.
- Global Health Institute, Xi'an Jiaotong University Health Science Center, Xi'an 710061, China.
| | - Guihua Zhuang
- School of Public Health, Xi'an Jiaotong University Health Science Center, Xi'an 710061, China.
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16
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Ya-Umphan P, Cerqueira D, Cottrell G, Parker DM, Fowkes FJI, Nosten F, Corbel V. Anopheles Salivary Biomarker as a Proxy for Estimating Plasmodium falciparum Malaria Exposure on the Thailand-Myanmar Border. Am J Trop Med Hyg 2018; 99:350-356. [PMID: 29869601 DOI: 10.4269/ajtmh.18-0081] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Timely identification and treatment of malaria transmission "hot spots" is essential to achieve malaria elimination. Here we investigate the relevance of using an Anopheles salivary biomarker to estimate Plasmodium falciparum malaria exposure risk along the Thailand-Myanmar border to guide malaria control. Between May 2013 and December 2014, > 9,000 blood samples collected in a cluster randomized control trial were screened with serological assays to measure the antibody responses to Anopheles salivary antigen (gSG6-P1) and P. falciparum malaria antigens (circumsporozoite protein, merozoite surface protein 119 [MSP-119]). Plasmodium falciparum infections were monitored through passive and active case detection. Seroprevalence to gSG6-P1, MSP-119, and CSP were 71.8% (95% Confidence interval [CI]: 70.9, 72.7), 68.6% (95% CI: 67.7, 69.5), and 8.6% (95% CI: 8.0, 9.2), respectively. Multivariate analysis showed that individuals with the highest Ab response to gSG6-P1 had six times the odds of being positive to CSP antigens (P < 0.001) and two times the odds of P. falciparum infection compared with low gSG6-P1 responders (P = 0.004). Spatial scan statistics revealed the presence of clusters of gSG6-P1 that partially overlapped P. falciparum infections. The gSG6-P1 salivary biomarker represents a good proxy for estimating P. falciparum malaria risk and could serve to implement hot spot-targeted vector control interventions to achieve malaria elimination.
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Affiliation(s)
- Phubeth Ya-Umphan
- Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle (IRD 224-CNRS 5290 UM1-UM2), Institut de Recherche pour le Développement (IRD), University of Montpellier, Montpellier, France
| | - Dominique Cerqueira
- Shoklo Malaria Research Unit, Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Tak, Thailand
| | - Gilles Cottrell
- Institut de Recherche pour le Développement (IRD), Université Paris Descartes, Sorbonne Paris Cité, UMR 216, Paris, France
| | - Daniel M Parker
- Department of Population Health and Disease Prevention, University of California, Irvine, California.,Shoklo Malaria Research Unit, Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Tak, Thailand
| | - Freya J I Fowkes
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia.,Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia.,Disease Elimination Program, Life Sciences, Burnet Institute, Melbourne, Australia
| | - Francois Nosten
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine Research Building, University of Oxford Old Road Campus, Oxford, United Kingdom.,Shoklo Malaria Research Unit, Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Tak, Thailand
| | - Vincent Corbel
- Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle (IRD 224-CNRS 5290 UM1-UM2), Institut de Recherche pour le Développement (IRD), University of Montpellier, Montpellier, France
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17
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Malaria diagnosis by PCR revealed differential distribution of mono and mixed species infections by Plasmodium falciparum and P. vivax in India. PLoS One 2018; 13:e0193046. [PMID: 29565981 PMCID: PMC5863947 DOI: 10.1371/journal.pone.0193046] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2017] [Accepted: 02/02/2018] [Indexed: 11/20/2022] Open
Abstract
Malaria is a vector-borne infectious disease, caused by five different species of the genus Plasmodium, and is endemic to many tropical and sub-tropical countries of the globe. At present, malaria diagnosis at the primary health care level in India is conducted by either microscopy or rapid diagnostic test (RDT). In recent years, molecular diagnosis (by PCR assay), has emerged as the most sensitive method for malaria diagnosis. India is highly endemic to malaria and shoulders the burden of two major malaria parasites, Plasmodium falciparum and P. vivax. Previous studies using PCR diagnostic assay had unraveled several interesting facts on distribution of malaria parasites in India. However, these studies had several limitations from small sample size to limited geographical areas of sampling. In order to mitigate these limitations, we have collected finger-prick blood samples from 2,333 malaria symptomatic individuals in nine states from 11 geographic locations, covering almost the entire malaria endemic regions of India and performed all the three diagnostic tests (microscopy, RDT and PCR assay) and also have conducted comparative assessment on the performance of the three diagnostic tests. Since PCR assay turned out to be highly sensitive (827 malaria positive cases) among the three types of tests, we have utilized data from PCR diagnostic assay for analyses and inferences. The results indicate varied distributional prevalence of P. vivax and P. falciparum according to locations in India, and also the mixed species infection due to these two species. The proportion of P. falciparum to P. vivax was found to be 49:51, and percentage of mixed species infections due to these two parasites was found to be 13% of total infections. Considering India is set for malaria elimination by 2030, the present malaria epidemiological information is of high importance.
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Ohm JR, Baldini F, Barreaux P, Lefevre T, Lynch PA, Suh E, Whitehead SA, Thomas MB. Rethinking the extrinsic incubation period of malaria parasites. Parasit Vectors 2018. [PMID: 29530073 PMCID: PMC5848458 DOI: 10.1186/s13071-018-2761-4] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The time it takes for malaria parasites to develop within a mosquito, and become transmissible, is known as the extrinsic incubation period, or EIP. EIP is a key parameter influencing transmission intensity as it combines with mosquito mortality rate and competence to determine the number of mosquitoes that ultimately become infectious. In spite of its epidemiological significance, data on EIP are scant. Current approaches to estimate EIP are largely based on temperature-dependent models developed from data collected on parasite development within a single mosquito species in the 1930s. These models assume that the only factor affecting EIP is mean environmental temperature. Here, we review evidence to suggest that in addition to mean temperature, EIP is likely influenced by genetic diversity of the vector, diversity of the parasite, and variation in a range of biotic and abiotic factors that affect mosquito condition. We further demonstrate that the classic approach of measuring EIP as the time at which mosquitoes first become infectious likely misrepresents EIP for a mosquito population. We argue for a better understanding of EIP to improve models of transmission, refine predictions of the possible impacts of climate change, and determine the potential evolutionary responses of malaria parasites to current and future mosquito control tools.
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Affiliation(s)
- Johanna R Ohm
- Center for Infectious Disease Dynamics, Pennsylvania State University, University Park, PA, USA.
| | - Francesco Baldini
- Institute of Biodiversity Animal Health and Comparative Medicine, University of Glasgow, Glasgow, Scotland, UK
| | - Priscille Barreaux
- Center for Infectious Disease Dynamics, Pennsylvania State University, University Park, PA, USA
| | - Thierry Lefevre
- MIVEGEC, IRD, CNRS, University of Montpellier, Montpellier, France
| | - Penelope A Lynch
- College of Life and Environmental Sciences, Penryn Campus, University of Exeter, Cornwall, UK
| | - Eunho Suh
- Center for Infectious Disease Dynamics, Pennsylvania State University, University Park, PA, USA
| | - Shelley A Whitehead
- Center for Infectious Disease Dynamics, Pennsylvania State University, University Park, PA, USA
| | - Matthew B Thomas
- Center for Infectious Disease Dynamics, Pennsylvania State University, University Park, PA, USA
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19
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Sumarnrote A, Corbel V, Overgaard HJ, Celhay O, Marasri N, Fustec B, Thanispong K, Chareonviriyaphap T. Plasmodium Infections in Anopheles Mosquitoes in Ubon Ratchathani Province, Northeastern Thailand During a Malaria Outbreak. JOURNAL OF THE AMERICAN MOSQUITO CONTROL ASSOCIATION 2018; 34:11-17. [PMID: 31442122 DOI: 10.2987/17-6715.1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
An unprecedented malaria outbreak occurred in Ubon Ratchathani Province, northeastern Thailand, in 2014. The province showed the highest number of malaria cases of all Thai provinces. Five entomological surveys were conducted at 8 sentinel sites from September 2013 to September 2015 to address the role of different Anopheles species in malaria transmission. Mosquito collections were conducted using human landing catches and cow bait. A total of 10,369 Anopheles mosquitoes were collected and 2,240 were morphologically identified as potential malaria vectors, including An. dirus (n = 78), An. minimus (n = 18), An. sawadwongporni (n = 4), An. barbirostris s.l. (n = 819), An. philippinensis (n = 612), An. nivipes (n = 676), An. annularis (n = 42), An. aconitus (n = 7), and An. rampae (n = 142). Real-time polymerase chain reaction was used to screen for the presence of Plasmodium spp. in salivary glands. The proportion of primary vectors of surveyed villages was very low (<1%), and no Plasmodium-infected specimens were detected among in the 2,240 Anopheles mosquitoes tested. The absence of positive Plasmodium samples during malaria outbreaks suggests that malaria transmission most likely occurred outside the villages, particularly in the deep-forested hilly areas that provided suitable habitats for competent malaria vectors. These results emphasize the need to develop vector control related to village community activities to reduce malaria transmission along Thailand border areas.
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Brown LD, Thompson GA, Hillyer JF. Transstadial transmission of larval hemocoelic infection negatively affects development and adult female longevity in the mosquito Anopheles gambiae. J Invertebr Pathol 2017; 151:21-31. [PMID: 29111355 DOI: 10.1016/j.jip.2017.10.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 10/06/2017] [Accepted: 10/26/2017] [Indexed: 01/30/2023]
Abstract
During all life stages, mosquitoes are exposed to pathogens, and employ an immune system to resist or limit infection. Although much attention has been paid to how adult mosquitoes fight infection, little is known about how an infection during the larval stage affects the biology of the resultant adult. In this study, we investigated whether a bacterial infection in the hemocoel of the African malaria mosquito, Anopheles gambiae, is transstadially transmitted from larvae to adults (both females and males), and whether immune stimulation in the hemocoel as a larva alters development or biological traits of the adult. Specifically, larvae were injected in the hemocoel with either fluorescent microspheres or Escherichia coli, and the following traits were examined: transstadial transmission, larval development to adulthood, adult survival, and adult body size. Our results show that transstadial transmission of hemocoel contents occurs from larvae to pupae and from pupae to adults, but that bacterial prevalence and intensity varies with age. Injury, immune stimulation or infection decreases the proportion of larvae that undergo pupation and eclosion, infection decreases the longevity of adult females, and treatment has complex effects on the body size of the resultant adults. The present study adds larval hemocoelic infection to the known non-genetic factors that reduce overall fitness by negatively affecting development and adult biological traits that influence mosquito vector competence.
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Affiliation(s)
- Lisa D Brown
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA
| | - Grayson A Thompson
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA
| | - Julián F Hillyer
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA.
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21
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González C, Molina AG, León C, Salcedo N, Rondón S, Paz A, Atencia MC, Tovar C, Ortiz M. Entomological characterization of malaria in northern Colombia through vector and parasite species identification, and analyses of spatial distribution and infection rates. Malar J 2017; 16:431. [PMID: 29078770 PMCID: PMC5658941 DOI: 10.1186/s12936-017-2076-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Accepted: 10/19/2017] [Indexed: 11/13/2022] Open
Abstract
Background Malaria remains a worldwide public health concern and, in Colombia, despite the efforts to stop malaria transmission, the incidence of cases has increased over the last few years. In this context, it is necessary to evaluate vector diversity, infection rates, and spatial distribution, to better understand disease transmission dynamics. This information may contribute to the planning and development of vector control strategies. Results A total of 778 Anopheles mosquitoes were collected in fifteen localities of Córdoba from August 2015 to October 2016. Six species were identified and overall, Anopheles albimanus was the most widespread and abundant species (83%). Other species of the Nyssorhynchus subgenus were collected, including Anopheles triannulatus (13%), Anopheles nuneztovari (1%), Anopheles argyritarsis (< 1%) and two species belonging to the Anopheles subgenus: Anopheles pseudopunctipennis (3%) and Anopheles neomaculipalpus (< 1%). Four species were found naturally infected with two Plasmodium species: Anopheles nuneztovari was detected naturally infected with Plasmodium falciparum and Anopheles pseudopunctipennis with Plasmodium vivax, whereas An. albimanus and An. triannulatus were found infected with both parasite species and confirmed by nested PCR. Conclusions In general, the obtained results were contrasting with previous studies in terms of the most abundant and widespread collected species, and regarding infection rates, which were higher than those previously reported. A positive relationship between mosquito local abundance at the locality level and human infection at the municipality level was found. Mosquito local abundance and the number of houses with mosquitoes in each village are factors explaining malaria human cases in these villages. The obtained results suggest that other factors related to the apparent variation in malaria eco-epidemiology in northern Colombia, must be identified, to provide health authorities with better decision tools aiming to design control and prevention strategies. Electronic supplementary material The online version of this article (doi:10.1186/s12936-017-2076-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Camila González
- Centro de Investigaciones en Microbiología y Parasitología Tropical, CIMPAT, Departamento de Ciencias Biológicas, Universidad de los Andes, Cra. 1 No 18A-12, Bogotá, Colombia.
| | - Astrid Gisell Molina
- Centro de Investigaciones en Microbiología y Parasitología Tropical, CIMPAT, Departamento de Ciencias Biológicas, Universidad de los Andes, Cra. 1 No 18A-12, Bogotá, Colombia
| | - Cielo León
- Centro de Investigaciones en Microbiología y Parasitología Tropical, CIMPAT, Departamento de Ciencias Biológicas, Universidad de los Andes, Cra. 1 No 18A-12, Bogotá, Colombia
| | - Nicolás Salcedo
- Centro de Investigaciones en Microbiología y Parasitología Tropical, CIMPAT, Departamento de Ciencias Biológicas, Universidad de los Andes, Cra. 1 No 18A-12, Bogotá, Colombia
| | - Silvia Rondón
- Centro de Investigaciones en Microbiología y Parasitología Tropical, CIMPAT, Departamento de Ciencias Biológicas, Universidad de los Andes, Cra. 1 No 18A-12, Bogotá, Colombia
| | - Andrea Paz
- Centro de Investigaciones en Microbiología y Parasitología Tropical, CIMPAT, Departamento de Ciencias Biológicas, Universidad de los Andes, Cra. 1 No 18A-12, Bogotá, Colombia
| | - Maria Claudia Atencia
- Facultad de Ciencias de la Salud, Universidad del Sinú, Cra 1w No 38-153, Montería, Colombia
| | - Catalina Tovar
- Grupo de Enfermedades Tropicales y Resistencia Bacteriana, Facultad de Ciencias de la Salud, Universidad del Sinú, Cra 1w No 38-153, Montería, Colombia
| | - Mario Ortiz
- Centro de Investigaciones en Microbiología y Parasitología Tropical, CIMPAT, Departamento de Ciencias Biológicas, Universidad de los Andes, Cra. 1 No 18A-12, Bogotá, Colombia
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22
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Abstract
Malaria is caused in humans by five species of single-celled eukaryotic Plasmodium parasites (mainly Plasmodium falciparum and Plasmodium vivax) that are transmitted by the bite of Anopheles spp. mosquitoes. Malaria remains one of the most serious infectious diseases; it threatens nearly half of the world's population and led to hundreds of thousands of deaths in 2015, predominantly among children in Africa. Malaria is managed through a combination of vector control approaches (such as insecticide spraying and the use of insecticide-treated bed nets) and drugs for both treatment and prevention. The widespread use of artemisinin-based combination therapies has contributed to substantial declines in the number of malaria-related deaths; however, the emergence of drug resistance threatens to reverse this progress. Advances in our understanding of the underlying molecular basis of pathogenesis have fuelled the development of new diagnostics, drugs and insecticides. Several new combination therapies are in clinical development that have efficacy against drug-resistant parasites and the potential to be used in single-dose regimens to improve compliance. This ambitious programme to eliminate malaria also includes new approaches that could yield malaria vaccines or novel vector control strategies. However, despite these achievements, a well-coordinated global effort on multiple fronts is needed if malaria elimination is to be achieved.
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Affiliation(s)
- Margaret A Phillips
- Department of Biochemistry, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, Texas 75390-9038, USA
| | | | | | | | - Wesley C Van Voorhis
- University of Washington, Department of Medicine, Division of Allergy and Infectious Diseases, Center for Emerging and Re-emerging Infectious Diseases, Seattle, Washington, USA
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23
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Kwansomboon N, Chaumeau V, Kittiphanakun P, Cerqueira D, Corbel V, Chareonviriyaphap T. Vector bionomics and malaria transmission along the Thailand-Myanmar border: a baseline entomological survey. JOURNAL OF VECTOR ECOLOGY : JOURNAL OF THE SOCIETY FOR VECTOR ECOLOGY 2017; 42:84-93. [PMID: 28504441 DOI: 10.1111/jvec.12242] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2016] [Accepted: 12/16/2016] [Indexed: 06/07/2023]
Abstract
Baseline entomological surveys were conducted in four sentinel sites along the Thailand-Myanmar border to address vector bionomics and malaria transmission in the context of a study on malaria elimination. Adult Anopheles mosquitoes were collected using human-landing catch and cow-bait collection in four villages during the rainy season from May-June, 2013. Mosquitoes were identified to species level by morphological characters and by AS-PCR. Sporozoite indexes were determined on head/thoraces of primary and secondary malaria vectors using real-time PCR. A total of 4,301 anopheles belonging to 12 anopheline taxa were identified. Anopheles minimus represented >98% of the Minimus Complex members (n=1,683), whereas the An. maculatus group was composed of two dominant species, An. sawadwongporni and An. maculatus. Overall, 25 Plasmodium-positive mosquitoes (of 2,323) were found, representing a sporozoite index of 1.1% [95%CI 0.66-1.50]. The transmission intensity as measured by the EIR strongly varied according to the village (ANOVA, F=17.67, df=3, P<0.0001). Our findings highlight the diversity and complexity of the biting pattern of malaria vectors along the Thailand-Myanmar border that represent a formidable challenge for malaria control and elimination.
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Affiliation(s)
- N Kwansomboon
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand
| | - V Chaumeau
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand
- Centre hospitalier universitaire de Montpellier, Montpellier, France
- Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), Institut de Recherche pour le Développement (IRD), Montpellier, France
| | - P Kittiphanakun
- Shoklo Malaria Research Unit (SMRU), Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Mae Sot, Tak, Thailand
| | - D Cerqueira
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand
- Shoklo Malaria Research Unit (SMRU), Mahidol-Oxford Tropical Medicine Research Unit (MORU), Faculty of Tropical Medicine, Mahidol University, Mae Sot, Tak, Thailand
| | - V Corbel
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand
- Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle (MIVEGEC), Institut de Recherche pour le Développement (IRD), Montpellier, France
| | - T Chareonviriyaphap
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand
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24
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Ya-Umphan P, Cerqueira D, Parker DM, Cottrell G, Poinsignon A, Remoue F, Brengues C, Chareonviriyaphap T, Nosten F, Corbel V. Use of an Anopheles Salivary Biomarker to Assess Malaria Transmission Risk Along the Thailand-Myanmar Border. J Infect Dis 2017; 215:396-404. [PMID: 27932615 PMCID: PMC5853934 DOI: 10.1093/infdis/jiw543] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 11/15/2016] [Indexed: 11/13/2022] Open
Abstract
Background The modalities of malaria transmission along the Thailand-Myanmar border are poorly understood. Here we address the relevance of using a specific Anopheles salivary biomarker to measure the risk among humans of exposure to Anopheles bites. Methods Serologic surveys were conducted from May 2013 to December 2014 in 4 sentinel villages. More than 9400 blood specimens were collected in filter papers from all inhabitants at baseline and then every 3 months thereafter, for up to 18 months, for analysis by enzyme-linked immunosorbent assay. The relationship between the intensity of the human antibody response and entomological indicators of transmission (human biting rates and entomological inoculation rates [EIRs]) was studied using a multivariate 3-level mixed model analysis. Heat maps for human immunoglobulin G (IgG) responses for each village and survey time point were created using QGIS 2.4. Results The levels of IgG response among participants varied significantly according to village, season, and age (P<.001) and were positively associated with the abundance of total Anopheles species and primary malaria vectors and the EIR (P<.001). Spatial clusters of high-IgG responders were identified across space and time within study villages. Conclusions The gSG6-P1 biomarker has great potential to address the risk of transmission along the Thailand-Myanmar border and represents a promising tool to guide malaria interventions.
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Affiliation(s)
- Phubeth Ya-Umphan
- Institut de Recherche pour le Développement, Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle, Montpellier, and
- Department of Entomology, Faculty of Agriculture, and
| | - Dominique Cerqueira
- Department of Entomology, Faculty of Agriculture, and
- Shoklo Malaria Research Unit, Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand; and
| | - Daniel M Parker
- Shoklo Malaria Research Unit, Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand; and
| | - Gilles Cottrell
- Institut de Recherche pour le Développement, Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Anne Poinsignon
- Institut de Recherche pour le Développement, Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle, Montpellier, and
| | - Franck Remoue
- Institut de Recherche pour le Développement, Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle, Montpellier, and
| | - Cecile Brengues
- Institut de Recherche pour le Développement, Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle, Montpellier, and
| | - Theeraphap Chareonviriyaphap
- Department of Entomology, Faculty of Agriculture, and
- Center for Advanced Studies for Agriculture and Food, Kasetsart University Institute for Advanced Studies, Kasetsart University, Bangkok, and
| | - Francois Nosten
- Shoklo Malaria Research Unit, Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand; and
- Nuffield Department of Medicine, Centre for Tropical Medicine, University of Oxford, United Kingdom
| | - Vincent Corbel
- Institut de Recherche pour le Développement, Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle, Montpellier, and
- Institut de Recherche pour le Développement, Université Paris Descartes, Sorbonne Paris Cité, Paris, France
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25
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Deng S, Ruan Y, Bai Y, Hu Y, Deng Z, He Y, Ruan R, Wu Y, Yang Z, Cui L. Genetic diversity of the Pvk12 gene in Plasmodium vivax from the China-Myanmar border area. Malar J 2016; 15:528. [PMID: 27809837 PMCID: PMC5096284 DOI: 10.1186/s12936-016-1592-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 10/28/2016] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Plasmodium falciparum resistance to artemisinin emerged in the Greater Mekong Sub-region has been associated with mutations in the propeller domain of the kelch gene Pfk13. METHODS Here the polymorphisms in Pvk12 gene, the orthologue of Pfk13 in Plasmodium vivax, were determined by PCR and sequencing in 262 clinical isolates collected in recent years (2012-2015) from the China-Myanmar border area. RESULTS Sequencing of full-length Pvk12 genes from these isolates identified three synonymous mutations (N172N, S360S, S697S) and one non-synonymous mutation M124I, all of which were at very low prevalence (2.0-3.1%). Moreover, these mutations were non-overlapping between the two study sites on both sides of the border. Molecular evolutionary analysis detected signature of purifying selection on Pvk12. CONCLUSIONS There is no direct evidence that Pvk12 is involved in artemisinin resistance in P. vivax, but it remains a potential candidate requiring further investigation. Continuous monitoring of potential drug resistance in this parasite is needed in order to facilitate the regional malaria elimination campaign.
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Affiliation(s)
- Shuang Deng
- Department of Pathogen Biology and Immunology, Kunming Medical University, Kunming, 650500, Yunnan Province, China.,Department of Pathology, Kunming Medical University, Kunming, 650500, Yunnan Province, China
| | - Yonghua Ruan
- Department of Pathology, Kunming Medical University, Kunming, 650500, Yunnan Province, China
| | - Yao Bai
- Department of Pathogen Biology and Immunology, Kunming Medical University, Kunming, 650500, Yunnan Province, China.,Department of Pharmacology, Kunming Medical University, Kunming, 650500, Yunnan Province, China
| | - Yue Hu
- Department of Pathogen Biology and Immunology, Kunming Medical University, Kunming, 650500, Yunnan Province, China.,Department of Pathology, Kunming Medical University, Kunming, 650500, Yunnan Province, China
| | - Zeshuai Deng
- Department of Cell Biology and Medical Genetics, Kunming Medical University, Kunming, 650500, Yunnan Province, China
| | - Yongshu He
- Department of Cell Biology and Medical Genetics, Kunming Medical University, Kunming, 650500, Yunnan Province, China
| | - Rui Ruan
- Department of Orthopedics, The First Affiliated Hospital, Kunming Medical University, Kunming, 650500, Yunnan Province, China
| | - Yanrui Wu
- Department of Cell Biology and Medical Genetics, Kunming Medical University, Kunming, 650500, Yunnan Province, China
| | - Zhaoqing Yang
- Department of Pathogen Biology and Immunology, Kunming Medical University, Kunming, 650500, Yunnan Province, China.
| | - Liwang Cui
- Department of Pathogen Biology and Immunology, Kunming Medical University, Kunming, 650500, Yunnan Province, China.
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26
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Chaumeau V, Andolina C, Fustec B, Tuikue Ndam N, Brengues C, Herder S, Cerqueira D, Chareonviriyaphap T, Nosten F, Corbel V. Comparison of the Performances of Five Primer Sets for the Detection and Quantification of Plasmodium in Anopheline Vectors by Real-Time PCR. PLoS One 2016; 11:e0159160. [PMID: 27441839 PMCID: PMC4956213 DOI: 10.1371/journal.pone.0159160] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Accepted: 06/28/2016] [Indexed: 02/07/2023] Open
Abstract
Quantitative real-time polymerase chain reaction (qrtPCR) has made a significant improvement for the detection of Plasmodium in anopheline vectors. A wide variety of primers has been used in different assays, mostly adapted from molecular diagnosis of malaria in human. However, such an adaptation can impact the sensitivity of the PCR. Therefore we compared the sensitivity of five primer sets with different molecular targets on blood stages, sporozoites and oocysts standards of Plasmodium falciparum (Pf) and P. vivax (Pv). Dilution series of standard DNA were used to discriminate between methods at low concentrations of parasite and to generate standard curves suitable for the absolute quantification of Plasmodium sporozoites. Our results showed that the best primers to detect blood stages were not necessarily the best ones to detect sporozoites. Absolute detection threshold of our qrtPCR assay varied between 3.6 and 360 Pv sporozoites and between 6 and 600 Pf sporozoites per mosquito according to the primer set used in the reaction mix. In this paper, we discuss the general performance of each primer set and highlight the need to use efficient detection methods for transmission studies.
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Affiliation(s)
- V. Chaumeau
- Centre hospitalier universitaire de Montpellier, Montpellier, France
- Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle, Institut de Recherche pour le Développement, Montpellier, France
- Centre for Advanced Studies for Agriculture and Food, Institute of Advanced Studies, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand
- * E-mail: (V. Chaumeau); (V. Corbel)
| | - C. Andolina
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - B. Fustec
- Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle, Institut de Recherche pour le Développement, Montpellier, France
- Centre for Advanced Studies for Agriculture and Food, Institute of Advanced Studies, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand
| | - N. Tuikue Ndam
- Institut de Recherche pour le développement, UMR216, Mère et enfant face aux infections tropicales, Paris, France
- Communauté d’Universités et d’Etablissements Sorbonne Paris Cité, Faculté de Pharmacie, Paris, France
| | - C. Brengues
- Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle, Institut de Recherche pour le Développement, Montpellier, France
| | - S. Herder
- UMR Intertryp, Institut de Recherche pour le Développement, Montpellier, France
- Department of Parasitology, Faculty of Veterinary Medicine, Kasetsart University, Bangkok, Thailand
| | - D. Cerqueira
- Centre for Advanced Studies for Agriculture and Food, Institute of Advanced Studies, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - T. Chareonviriyaphap
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand
| | - F. Nosten
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine 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
| | - V. Corbel
- Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle, Institut de Recherche pour le Développement, Montpellier, France
- Centre for Advanced Studies for Agriculture and Food, Institute of Advanced Studies, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand
- * E-mail: (V. Chaumeau); (V. Corbel)
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27
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Ramiro RS, Khan SM, Franke-Fayard B, Janse CJ, Obbard DJ, Reece SE. Hybridization and pre-zygotic reproductive barriers in Plasmodium. Proc Biol Sci 2016; 282:20143027. [PMID: 25854886 PMCID: PMC4426616 DOI: 10.1098/rspb.2014.3027] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Sexual reproduction is an obligate step in the life cycle of many parasites, including the causative agents of malaria (Plasmodium). Mixed-species infections are common in nature and consequently, interactions between heterospecific gametes occur. Given the importance of managing gene flow across parasite populations, remarkably little is understood about how reproductive isolation between species is maintained. We use the rodent malaria parasites P. berghei and P. yoelii to investigate the ecology of mixed-species mating groups, identify proteins involved in pre-zygotic barriers, and examine their evolution. Specifically, we show that (i) hybridization occurs, but at low frequency; (ii) hybridization reaches high levels when female gametes lack the surface proteins P230 or P48/45, demonstrating that these proteins are key for pre-zygotic reproductive isolation; (iii) asymmetric reproductive interference occurs, where the fertility of P. berghei gametes is reduced in the presence of P. yoelii and (iv) as expected for gamete recognition proteins, strong positive selection acts on a region of P230 and P47 (P48/45 paralogue). P230 and P48/45 are leading candidates for interventions to block malaria transmission. Our results suggest that depending on the viability of hybrids, applying such interventions to populations where mixed-species infections occur could either facilitate or hinder malaria control.
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Affiliation(s)
- Ricardo S Ramiro
- Institute of Evolutionary Biology, University of Edinburgh, Ashworth Laboratories, West Mains Road, Edinburgh EH9 3JT, UK
| | - Shahid M Khan
- Department of Parasitology, Leiden Malaria Research Group, LUMC, Albinusdreef 2, ZA Leiden 2333, The Netherlands
| | - Blandine Franke-Fayard
- Department of Parasitology, Leiden Malaria Research Group, LUMC, Albinusdreef 2, ZA Leiden 2333, The Netherlands
| | - Chris J Janse
- Department of Parasitology, Leiden Malaria Research Group, LUMC, Albinusdreef 2, ZA Leiden 2333, The Netherlands
| | - Darren J Obbard
- Institute of Evolutionary Biology, University of Edinburgh, Ashworth Laboratories, West Mains Road, Edinburgh EH9 3JT, UK Centre for Immunity, Infection and Evolution, University of Edinburgh, Ashworth Laboratories, West Mains Road, Edinburgh EH9 3JT, UK
| | - Sarah E Reece
- Institute of Evolutionary Biology, University of Edinburgh, Ashworth Laboratories, West Mains Road, Edinburgh EH9 3JT, UK Centre for Immunity, Infection and Evolution, University of Edinburgh, Ashworth Laboratories, West Mains Road, Edinburgh EH9 3JT, UK Institute of Immunology and Infection Research, University of Edinburgh, Ashworth Laboratories, West Mains Road, Edinburgh EH9 3JT, UK
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Cross-Immunity and Community Structure of a Multiple-Strain Pathogen in the Tick Vector. Appl Environ Microbiol 2015; 81:7740-52. [PMID: 26319876 DOI: 10.1128/aem.02296-15] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Accepted: 08/25/2015] [Indexed: 12/11/2022] Open
Abstract
Many vector-borne pathogens consist of multiple strains that circulate in both the vertebrate host and the arthropod vector. Characterization of the community of pathogen strains in the arthropod vector is therefore important for understanding the epidemiology of mixed vector-borne infections. Borrelia afzelii and B. garinii are two species of tick-borne bacteria that cause Lyme disease in humans. These two sympatric pathogens use the same tick, Ixodes ricinus, but are adapted to different classes of vertebrate hosts. Both Borrelia species consist of multiple strains that are classified using the highly polymorphic ospC gene. Vertebrate cross-immunity against the OspC antigen is predicted to structure the community of multiple-strain Borrelia pathogens. Borrelia isolates were cultured from field-collected I. ricinus ticks over a period spanning 11 years. The Borrelia species of each isolate was identified using a reverse line blot (RLB) assay. Deep sequencing was used to characterize the ospC communities of 190 B. afzelii isolates and 193 B. garinii isolates. Infections with multiple ospC strains were common in ticks, but vertebrate cross-immunity did not influence the strain structure in the tick vector. The pattern of genetic variation at the ospC locus suggested that vertebrate cross-immunity exerts strong selection against intermediately divergent ospC alleles. Deep sequencing found that more than 50% of our isolates contained exotic ospC alleles derived from other Borrelia species. Two alternative explanations for these exotic ospC alleles are cryptic coinfections that were not detected by the RLB assay or horizontal transfer of the ospC gene between Borrelia species.
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Al-Amin HM, Elahi R, Mohon AN, Kafi MAH, Chakma S, Lord JS, Khan WA, Haque R, Norris DE, Alam MS. Role of underappreciated vectors in malaria transmission in an endemic region of Bangladesh-India border. Parasit Vectors 2015; 8:195. [PMID: 25889228 PMCID: PMC4416289 DOI: 10.1186/s13071-015-0803-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Accepted: 03/17/2015] [Indexed: 11/19/2022] Open
Abstract
Background Despite the efforts of the National Malaria Control Programme, malaria remains as an important public health problem in Bangladesh, particularly in the south-eastern region bordering India. Successful malaria control strategies rely on a detailed understanding of the underlying causes of malaria transmission. Here, an entomological survey was conducted in a malaria endemic area of Bangladesh bordering India to investigate the Anopheles mosquito community and assess their Plasmodium infection status. Methods Monthly entomological collections were undertaken from October 2010 to September 2011 in five villages in the Matiranga sub-district, Khagrachari district in Bangladesh, bordering the Indian State of Tripura. CDC miniature light traps were placed inside houses to collect adult Anopheles mosquitoes. Following morphological and molecular identification of the female Anopheles mosquitoes collected, they were screened for circumsporozoite proteins (CSP) of Plasmodium falciparum (Pf), Plasmodium vivax-210 (Pv-210) and Plasmodium vivax-247 (Pv-247), by ELISA to determine natural infection rates. Variation in Anopheles species composition, relative abundance and Plasmodium infection rates were analysed between sampled villages. Results A total of 2,027 female Anopheles were collected, belonging to 20 species. Anopheles nivipes was the most abundant species in our test villages during the peak malaria transmission season, and was observed sympatrically with An. philippinensis in the studied area. However, in the dry off-peak season, An. jeyporiensis was the most abundant species. Shannon’s diversity index was highest in October (2.12) and evenness was highest in May (0.91). The CSP ELISA positive rate overall was 0.44%. Anopheles karwari (n = 2), An. barbirostris s.l. (n = 1) and An. vagus (n = 1) were recorded positive for Pf. Anopheles kochi (n = 1) was positive for Pv-210 while An. umbrosus (n = 1), An. nivipes (n = 1) and An. kochi (n = 1) were positive for Pv-247. A mixed infection of Pf and Pv-247 was detected in An. barbirostris s.l.. Conclusion High diversity of Anopheles species was observed in areas close to the international border where species that were underestimated for malaria transmission significantly outnumbered principal vector species and these may play a significantly heightened role in malaria transmission. Electronic supplementary material The online version of this article (doi:10.1186/s13071-015-0803-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Hasan Mohammad Al-Amin
- International Centre for Diarrhoeal Disease Research Bangladesh (icddr,b), 68 Shaheed Tajuddin Ahmed Sarani, Mohakhali, Dhaka, 1212, Bangladesh.
| | - Rubayet Elahi
- International Centre for Diarrhoeal Disease Research Bangladesh (icddr,b), 68 Shaheed Tajuddin Ahmed Sarani, Mohakhali, Dhaka, 1212, Bangladesh. .,Department of Biochemistry, Virginia Tech, Blacksburg, VA, 24061, USA.
| | - Abu Naser Mohon
- International Centre for Diarrhoeal Disease Research Bangladesh (icddr,b), 68 Shaheed Tajuddin Ahmed Sarani, Mohakhali, Dhaka, 1212, Bangladesh. .,Department of Microbiology and Infectious Disease, Cumming School of Medicine, University of Calgary, Alberta, T2N1N4, Canada.
| | - Mohammad Abdullah Heel Kafi
- International Centre for Diarrhoeal Disease Research Bangladesh (icddr,b), 68 Shaheed Tajuddin Ahmed Sarani, Mohakhali, Dhaka, 1212, Bangladesh.
| | - Sumit Chakma
- International Centre for Diarrhoeal Disease Research Bangladesh (icddr,b), 68 Shaheed Tajuddin Ahmed Sarani, Mohakhali, Dhaka, 1212, Bangladesh.
| | - Jennifer S Lord
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.
| | - Wasif A Khan
- International Centre for Diarrhoeal Disease Research Bangladesh (icddr,b), 68 Shaheed Tajuddin Ahmed Sarani, Mohakhali, Dhaka, 1212, Bangladesh.
| | - Rashidul Haque
- International Centre for Diarrhoeal Disease Research Bangladesh (icddr,b), 68 Shaheed Tajuddin Ahmed Sarani, Mohakhali, Dhaka, 1212, Bangladesh.
| | - Douglas E Norris
- Johns Hopkins Malaria Research Institute, Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD, 21205, USA.
| | - Mohammad Shafiul Alam
- International Centre for Diarrhoeal Disease Research Bangladesh (icddr,b), 68 Shaheed Tajuddin Ahmed Sarani, Mohakhali, Dhaka, 1212, Bangladesh.
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Within-host competition does not select for virulence in malaria parasites; studies with Plasmodium yoelii. PLoS Pathog 2015; 11:e1004628. [PMID: 25658331 PMCID: PMC4450063 DOI: 10.1371/journal.ppat.1004628] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Accepted: 12/14/2014] [Indexed: 11/19/2022] Open
Abstract
In endemic areas with high transmission intensities, malaria infections are very often composed of multiple genetically distinct strains of malaria parasites. It has been hypothesised that this leads to intra-host competition, in which parasite strains compete for resources such as space and nutrients. This competition may have repercussions for the host, the parasite, and the vector in terms of disease severity, vector fitness, and parasite transmission potential and fitness. It has also been argued that within-host competition could lead to selection for more virulent parasites. Here we use the rodent malaria parasite Plasmodium yoelii to assess the consequences of mixed strain infections on disease severity and parasite fitness. Three isogenic strains with dramatically different growth rates (and hence virulence) were maintained in mice in single infections or in mixed strain infections with a genetically distinct strain. We compared the virulence (defined as harm to the mammalian host) of mixed strain infections with that of single infections, and assessed whether competition impacted on parasite fitness, assessed by transmission potential. We found that mixed infections were associated with a higher degree of disease severity and a prolonged infection time. In the mixed infections, the strain with the slower growth rate was often responsible for the competitive exclusion of the faster growing strain, presumably through host immune-mediated mechanisms. Importantly, and in contrast to previous work conducted with Plasmodium chabaudi, we found no correlation between parasite virulence and transmission potential to mosquitoes, suggesting that within-host competition would not drive the evolution of parasite virulence in P. yoelii.
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Putaporntip C, Miao J, Kuamsab N, Sattabongkot J, Sirichaisinthop J, Jongwutiwes S, Cui L. The Plasmodium vivax merozoite surface protein 3β sequence reveals contrasting parasite populations in southern and northwestern Thailand. PLoS Negl Trop Dis 2014; 8:e3336. [PMID: 25412166 PMCID: PMC4238993 DOI: 10.1371/journal.pntd.0003336] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Accepted: 10/13/2014] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Malaria control efforts have a significant impact on the epidemiology and parasite population dynamics. In countries aiming for malaria elimination, malaria transmission may be restricted to limited transmission hot spots, where parasite populations may be isolated from each other and experience different selection forces. Here we aim to examine the Plasmodium vivax population divergence in geographically isolated transmission zones in Thailand. METHODOLOGY We employed the P. vivax merozoite surface protein 3β (PvMSP3β) as a molecular marker for characterizing P. vivax populations based on the extensive diversity of this gene in Southeast Asian parasite populations. To examine two parasite populations with different transmission levels in Thailand, we obtained 45 P. vivax isolates from Tak Province, northwestern Thailand, where the annual parasite incidence (API) was more than 2%, and 28 isolates from Yala and Narathiwat Provinces, southern Thailand, where the API was less than 0.02%. We sequenced the PvMSP3β gene and examined its genetic diversity and molecular evolution between the parasite populations. PRINCIPAL FINDINGS Of 58 isolates containing single PvMSP3β alleles, 31 sequence types were identified. The overall haplotype diversity was 0.77 ± 0.06 and nucleotide diversity 0.0877±0.0054. The northwestern vivax malaria population exhibited extensive haplotype diversity (HD) of PvMSP3β (HD=1.0). In contrast, the southern parasite population displayed a single PvMSP3β allele (HD=0), suggesting a clonal population expansion. This result revealed that the extent of allelic diversity in P. vivax populations in Thailand varies among endemic areas. CONCLUSION Malaria parasite populations in a given region may vary significantly in genetic diversity, which may be the result of control and influenced by the magnitude of malaria transmission intensity. This is an issue that should be taken into account for the implementation of P. vivax control measures such as drug policy and vaccine development.
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Affiliation(s)
- Chaturong Putaporntip
- Molecular Biology of Malaria and Opportunistic Parasites Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Jun Miao
- Department of Entomology, The Pennsylvania State University, State College, Pennsylvania, United States of America
| | - Napaporn Kuamsab
- Molecular Biology of Malaria and Opportunistic Parasites Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Jetsumon Sattabongkot
- Vivax Malaria Research Center, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | | | - Somchai Jongwutiwes
- Molecular Biology of Malaria and Opportunistic Parasites Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Liwang Cui
- Department of Entomology, The Pennsylvania State University, State College, Pennsylvania, United States of America
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Reduced polymorphism in the Kelch propeller domain in Plasmodium vivax isolates from Cambodia. Antimicrob Agents Chemother 2014; 59:730-3. [PMID: 25385109 DOI: 10.1128/aac.03908-14] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Polymorphism in the ortholog gene of the Plasmodium falciparum K13 gene was investigated in Plasmodium vivax isolates collected in Cambodia. All of them were Sal-1 wild-type alleles except two (2/284, 0.7%), and P. vivax K12 polymorphism was reduced compared to that of the P. falciparum K13 gene. Both mutant allele isolates had the same nonsynonymous mutation at codon 552 (V552I) and were from Ratanak Kiri province. These preliminary data should encourage additional studies for associating artemisinin or chloroquine resistance and K12 polymorphism.
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Pharmacokinetic interactions between primaquine and pyronaridine-artesunate in healthy adult Thai subjects. Antimicrob Agents Chemother 2014; 59:505-13. [PMID: 25385096 PMCID: PMC4291381 DOI: 10.1128/aac.03829-14] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pyronaridine-artesunate is a newly introduced artemisinin-based combination treatment which may be deployed together with primaquine. A single-dose, randomized, three-sequence crossover study was conducted in healthy Thai volunteers to characterize potential pharmacokinetic interactions between these drugs. Seventeen healthy adults received a single oral dose of primaquine alone (30 mg base) and were then randomized to receive pyronaridine-artesunate alone (540−180 mg) or pyronaridine-artesunate plus primaquine in combination, with intervening washout periods between all treatments. The pharmacokinetic properties of primaquine, its metabolite carboxyprimaquine, artesunate, its metabolite dihydroartemisinin, and pyronaridine were assessed in 15 subjects using a noncompartmental approach followed by a bioequivalence evaluation. All drugs were well tolerated. The single oral dose of primaquine did not result in any clinically relevant pharmacokinetic alterations to pyronaridine, artesunate, or dihydroartemisinin exposures. There were significantly higher primaquine maximum plasma drug concentrations (geometric mean ratio, 30%; 90% confidence interval [CI], 17% to 46%) and total exposures (15%; 6.4% to 24%) during coadministration with pyronaridine-artesunate than when primaquine was given alone. Pyronaridine, like chloroquine and piperaquine, increases plasma primaquine concentrations. (This study has been registered at ClinicalTrials.gov under registration no. NCT01552330.)
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Senn H, Alattas N, Boggild AK, Morris SK. Mixed-species Plasmodium falciparum and Plasmodium ovale malaria in a paediatric returned traveller. Malar J 2014; 13:78. [PMID: 24593188 PMCID: PMC3975726 DOI: 10.1186/1475-2875-13-78] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2013] [Accepted: 02/26/2014] [Indexed: 12/02/2022] Open
Abstract
Malaria is a common and potentially fatal cause of febrile illness in returned travellers. Endemic areas for different malaria parasites overlap, but mixed species infections are rare. An adolescent male returned from a trip to Ghana in late summer 2013. He subsequently presented with blood smears positive for two species of malaria parasite, Plasmodium falciparum and Plasmodium ovale, on two isolated hospital visits within a six-week period. The epidemiology of mixed infections, likely pathophysiology of his presentation, and the implications for malaria testing and treatment in returned travellers are discussed.
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Affiliation(s)
- Heather Senn
- University of Toronto Faculty of Medicine, 1 King’s College Circle, Toronto, ON M5S 1A8, Canada
| | - Nadia Alattas
- Division of Infectious Diseases, Hospital for Sick Children, 555 University Ave., Toronto, ON M5G 1X8, Canada
| | - Andrea K Boggild
- Tropical Disease Unit, Division of Infectious Diseases, University Health Network-Toronto General Hospital, 200 Elizabeth Street, Toronto, ON M5G 2C4, Canada
- Department of Medicine, University of Toronto, Suite RFE 3–805, 200 Elizabeth Street, Toronto, ON M5G 2C4, Canada
- Public Health Ontario Laboratories, 81 Resources Road, Etobicoke, ON M9P 3T1, Canada
| | - Shaun K Morris
- Division of Infectious Diseases, Hospital for Sick Children, 555 University Ave., Toronto, ON M5G 1X8, Canada
- Department of Paediatrics, The Hospital for Sick Children, 555 University Avenue, Toronto, ON M5G 1X8, Canada
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Khandelwal K, Pachauri SD, Zaidi S, Dwivedi P, Sharma AK, Singh C, Dwivedi AK. Assay method for quality control and stability studies of a new antimalarial agent (CDRI 99/411). J Pharm Anal 2013; 3:335-340. [PMID: 29403836 PMCID: PMC5761009 DOI: 10.1016/j.jpha.2013.04.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
CDRI compound no. 99/411 is a potent 1,2,4-trioxane antimalarial candidate drug under development at our Institute. An HPLC method for determination of CDRI 99/411 with its starting material and intermediates has been developed and validated for in process quality control and stability studies. The analytical performance parameters such as linearity, precision, accuracy, specificity, limit of detection (LOD) and lower limit of quantification (LLOQ) were determined according to International Conference on Harmonization ICH Q2(R1) guidelines. HPLC separation was achieved on a RP-select B Lichrosphere® column (250 mm×4 mm, 5 μm, Merck) using water containing 0.1% glacial acetic acid and acetonitrile as the mobile phase in a gradient elution. The eluents were monitored by a photo diode array detector at 245 and 275 nm. Based on signal to noise ratio of 3 and 10 the LOD of CDRI 99/411 was 0.55 µg/mL, while the LLOQ was 1.05 µg/mL. The calibration curves were linear in the range of 1.05-68 µg/mL. Precision of the method was determined by inter- and intra-assay variations within the acceptable range.
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Affiliation(s)
- Kiran Khandelwal
- Division of Pharmaceutics, CSIR-Central Drug Research Institute, Chattar Manzil Palace, Lucknow 226001, India
| | - Shakti Deep Pachauri
- Division of Pharmaceutics, CSIR-Central Drug Research Institute, Chattar Manzil Palace, Lucknow 226001, India
| | - Sofia Zaidi
- Division of Pharmaceutics, CSIR-Central Drug Research Institute, Chattar Manzil Palace, Lucknow 226001, India
| | - Pankaj Dwivedi
- Division of Pharmaceutics, CSIR-Central Drug Research Institute, Chattar Manzil Palace, Lucknow 226001, India
| | - Ashok Kumar Sharma
- Division of Medicinal and Process Chemistry, CSIR-Central Drug Research Institute, Chattar Manzil Palace, Lucknow 226001, India
| | - Chandan Singh
- Division of Medicinal and Process Chemistry, CSIR-Central Drug Research Institute, Chattar Manzil Palace, Lucknow 226001, India
| | - Anil Kumar Dwivedi
- Division of Pharmaceutics, CSIR-Central Drug Research Institute, Chattar Manzil Palace, Lucknow 226001, India
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Lefèvre T, Vantaux A, Dabiré KR, Mouline K, Cohuet A. Non-genetic determinants of mosquito competence for malaria parasites. PLoS Pathog 2013; 9:e1003365. [PMID: 23818841 PMCID: PMC3688545 DOI: 10.1371/journal.ppat.1003365] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Understanding how mosquito vectors and malaria parasites interact is of fundamental interest, and it also offers novel perspectives for disease control. Both the genetic and environmental contexts are known to affect the ability of mosquitoes to support malaria development and transmission, i.e., vector competence. Although the role of environment has long been recognized, much work has focused on host and parasite genetic effects. However, the last few years have seen a surge of studies revealing a great diversity of ways in which non-genetic factors can interfere with mosquito-Plasmodium interactions. Here, we review the current evidence for such environmentally mediated effects, including ambient temperature, mosquito diet, microbial gut flora, and infection history, and we identify additional factors previously overlooked in mosquito-Plasmodium interactions. We also discuss epidemiological implications, and the evolutionary consequences for vector immunity and parasite transmission strategies. Finally, we propose directions for further research and argue that an improved knowledge of non-genetic influences on mosquito-Plasmodium interactions could aid in implementing conventional malaria control measures and contribute to the design of novel strategies.
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Affiliation(s)
- Thierry Lefèvre
- MIVEGEC, Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle, UMR Universités Montpellier 1 & 2, CNRS 5290, IRD 224, Montpellier, France.
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Abstract
Plasmodium vivax is a major cause of febrile illness in endemic areas of Asia, Central and South America, and the horn of Africa. P. vivax infections are characterized by relapses of malaria arising from persistent liver stages of the parasite (hypnozoites), which can be prevented currently only by 8-aminoquinoline anti-malarials. Tropical P. vivax infections relapse at approximately 3-week intervals if rapidly eliminated anti-malarials are given for treatment, whereas in temperate regions and parts of the sub-tropics, P. vivax infections are characterized by either a long incubation or a long-latency period between illness and relapse - in both cases approximating 8-10 months. The epidemiology of the different relapse phenotypes has not been defined adequately despite obvious relevance to malaria therapeutic assessment, control, and elimination. The number of sporozoites inoculated by the anopheline mosquito is an important determinant of both the timing and the number of relapses. The intervals between P. vivax relapses display a remarkable periodicity which has not been explained. Evidence is presented that the proportion of patients who have successive relapses is relatively constant and that the factor which activates hypnozoites and leads to regular interval relapse in vivax malaria is the systemic febrile illness itself. It is proposed that in endemic areas, a large proportion of the population harbours latent hypnozoites which can be activated by a systemic illness such as vivax or falciparum malaria. This explains the high rates of vivax following falciparum malaria, the high proportion of heterologous genotypes in relapses, the higher rates of relapse in people living in endemic areas compared with artificial infection studies, and, by facilitating recombination between different genotypes, contributes to P. vivax genetic diversity particularly in low transmission settings. Long-latency P. vivax phenotypes may be more widespread and more prevalent than currently thought. These observations have important implications for the assessment of radical treatment efficacy and for malaria control and elimination.
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Affiliation(s)
- Nicholas J White
- Mahidol Oxford Research Unit, Mahidol University, Bangkok, Thailand.
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Sharma A, Santos IO, Gaur P, Ferreira VF, Garcia CR, da Rocha DR. Addition of thiols to o-quinone methide: New 2-hydroxy-3-phenylsulfanylmethyl[1,4]naphthoquinones and their activity against the human malaria parasite Plasmodium falciparum (3D7). Eur J Med Chem 2013. [DOI: 10.1016/j.ejmech.2012.10.052] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Nkhoma SC, Nair S, Al-Saai S, Ashley E, McGready R, Phyo AP, Nosten F, Anderson TJC. Population genetic correlates of declining transmission in a human pathogen. Mol Ecol 2012; 22:273-85. [PMID: 23121253 PMCID: PMC3537863 DOI: 10.1111/mec.12099] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Revised: 09/14/2012] [Accepted: 09/19/2012] [Indexed: 12/17/2022]
Abstract
Pathogen control programs provide a valuable, but rarely exploited, opportunity to directly examine the relationship between population decline and population genetics. We investigated the impact of an ~12-fold decline in transmission on the population genetics of Plasmodium falciparum infections (n = 1731) sampled from four clinics on the Thai-Burma border over 10 years and genotyped using 96 genome-wide SNPs. The most striking associated genetic change was a reduction in the frequency of infections containing multiple parasite genotypes from 63% in 2001 to 14% in 2010 (P = 3 × 10(-15)). Two measures of the clonal composition of populations (genotypic richness and the β-parameter of the Pareto distribution) declined over time as more people were infected by parasites with identical multilocus genotypes, consistent with increased selfing and a reduction in the rate at which multilocus genotypes are broken apart by recombination. We predicted that the reduction in transmission, multiple clone carriage and outbreeding would be mirrored by an increased influence of genetic drift. However, geographical differentiation and expected heterozygosity remained stable across the sampling period. Furthermore, N(e) estimates derived from allele frequencies fluctuation between years remained high (582 to ∞) and showed no downward trend. These results demonstrate how genetic data can compliment epidemiological assessments of infectious disease control programs. The temporal changes in a single declining population parallel to those seen in comparisons of parasite genetics in regions of differing endemicity, strongly supporting the notion that reduced opportunity for outbreeding is the key driver of these patterns.
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Affiliation(s)
- Standwell C Nkhoma
- Texas Biomedical Research Institute, 7620 NW Loop 410, San Antonio, TX 78227, USA
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Imwong M, Boel ME, Pagornrat W, Pimanpanarak M, McGready R, Day NPJ, Nosten F, White NJ. The first Plasmodium vivax relapses of life are usually genetically homologous. J Infect Dis 2011; 205:680-3. [PMID: 22194628 PMCID: PMC3266132 DOI: 10.1093/infdis/jir806] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
In a prospective infant cohort, 21 infants developed Plasmodium vivax malaria during their first year. Twelve of their mothers also had vivax malaria in the corresponding pregnancies or postpartum period. The genotypes of the maternal and infant infections were all different. Eight of the 12 mothers and 9 of the 21 infants had recurrent infections. Relapse parasite genotypes were different to the initial infection in 13 of 20 (65%) mothers compared with 5 of 24 (21%) infants (P = .02). The first P. vivax relapses of life are usually genetically homologous, whereas relapse in adults may result from activation of heterologous latent hypnozoites acquired from previous inoculations.
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Affiliation(s)
- Mallika Imwong
- Department of Molecular Tropical Medicine and Genetics, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
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White NJ. Determinants of relapse periodicity in Plasmodium vivax malaria. Malar J 2011; 10:297. [PMID: 21989376 PMCID: PMC3228849 DOI: 10.1186/1475-2875-10-297] [Citation(s) in RCA: 420] [Impact Index Per Article: 32.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Accepted: 10/11/2011] [Indexed: 02/05/2023] Open
Abstract
Plasmodium vivax is a major cause of febrile illness in endemic areas of Asia, Central and South America, and the horn of Africa. Plasmodium vivax infections are characterized by relapses of malaria arising from persistent liver stages of the parasite (hypnozoites) which can be prevented only by 8-aminoquinoline anti-malarials. Tropical P. vivax relapses at three week intervals if rapidly eliminated anti-malarials are given for treatment, whereas in temperate regions and parts of the sub-tropics P. vivax infections are characterized either by a long incubation or a long-latency period between illness and relapse - in both cases approximating 8-10 months. The epidemiology of the different relapse phenotypes has not been defined adequately despite obvious relevance to malaria control and elimination. The number of sporozoites inoculated by the anopheline mosquito is an important determinant of both the timing and the number of relapses. The intervals between relapses display a remarkable periodicity which has not been explained. Evidence is presented that the proportion of patients who have successive relapses is relatively constant and that the factor which activates hypnozoites and leads to regular interval relapse in vivax malaria is the systemic febrile illness itself. It is proposed that in endemic areas a large proportion of the population harbours latent hypnozoites which can be activated by a systemic illness such as vivax or falciparum malaria. This explains the high rates of vivax following falciparum malaria, the high proportion of heterologous genotypes in relapses, the higher rates of relapse in people living in endemic areas compared with artificial infection studies, and, by facilitating recombination between different genotypes, contributes to P. vivax genetic diversity particularly in low transmission settings. Long-latency P. vivax phenotypes may be more widespread and more prevalent than currently thought. These observations have important implications for the assessment of radical treatment efficacy and for malaria control and elimination.
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Affiliation(s)
- Nicholas J White
- Mahidol Oxford Tropical Medicine Research Unit, Mahidol University, Bangkok, Thailand.
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