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He Q, Chaillet JK, Labbé F. Antigenic strain diversity predicts different biogeographic patterns of maintenance and decline of antimalarial drug resistance. eLife 2024; 12:RP90888. [PMID: 38363295 PMCID: PMC10942604 DOI: 10.7554/elife.90888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2024] Open
Abstract
The establishment and spread of antimalarial drug resistance vary drastically across different biogeographic regions. Though most infections occur in sub-Saharan Africa, resistant strains often emerge in low-transmission regions. Existing models on resistance evolution lack consensus on the relationship between transmission intensity and drug resistance, possibly due to overlooking the feedback between antigenic diversity, host immunity, and selection for resistance. To address this, we developed a novel compartmental model that tracks sensitive and resistant parasite strains, as well as the host dynamics of generalized and antigen-specific immunity. Our results show a negative correlation between parasite prevalence and resistance frequency, regardless of resistance cost or efficacy. Validation using chloroquine-resistant marker data supports this trend. Post discontinuation of drugs, resistance remains high in low-diversity, low-transmission regions, while it steadily decreases in high-diversity, high-transmission regions. Our study underscores the critical role of malaria strain diversity in the biogeographic patterns of resistance evolution.
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Affiliation(s)
- Qixin He
- Department of Biological Sciences, Purdue UniversityWest LafayetteUnited States
| | - John K Chaillet
- Department of Biological Sciences, Purdue UniversityWest LafayetteUnited States
| | - Frédéric Labbé
- Department of Ecology and Evolution, University of ChicagoChicagoUnited States
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He Q, Chaillet JK, Labbé F. Antigenic strain diversity predicts different biogeographic patterns of maintenance and decline of anti-malarial drug resistance. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.06.531320. [PMID: 37987011 PMCID: PMC10659383 DOI: 10.1101/2023.03.06.531320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
The establishment and spread of anti-malarial drug resistance vary drastically across different biogeographic regions. Though most infections occur in Sub-Saharan Africa, resistant strains often emerge in low-transmission regions. Existing models on resistance evolution lack consensus on the relationship between transmission intensity and drug resistance, possibly due to overlooking the feedback between antigenic diversity, host immunity, and selection for resistance. To address this, we developed a novel compartmental model that tracks sensitive and resistant parasite strains, as well as the host dynamics of generalized and antigen-specific immunity. Our results show a negative correlation between parasite prevalence and resistance frequency, regardless of resistance cost or efficacy. Validation using chloroquine-resistant marker data supports this trend. Post discontinuation of drugs, resistance remains high in low-diversity, low-transmission regions, while it steadily decreases in high-diversity, high-transmission regions. Our study underscores the critical role of malaria strain diversity in the biogeographic patterns of resistance evolution.
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Affiliation(s)
- Qixin He
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - John K. Chaillet
- Department of Biological Sciences, Purdue University, West Lafayette, IN, USA
| | - Frédéric Labbé
- Department of Ecology and Evolution, University of Chicago, Chicago, IL, USA
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Beshir KB, Muwanguzi J, Nader J, Mansukhani R, Traore A, Gamougam K, Ceesay S, Bazie T, Kolie F, Lamine MM, Cairns M, Snell P, Scott S, Diallo A, Merle CS, NDiaye JL, Razafindralambo L, Moroso D, Ouedraogo JB, Zongo I, Kessely H, Doumagoum D, Bojang K, Ceesay S, Loua K, Maiga H, Dicko A, Sagara I, Laminou IM, Ogboi SJ, Eloike T, Milligan P, Sutherland CJ. Prevalence of Plasmodium falciparum haplotypes associated with resistance to sulfadoxine-pyrimethamine and amodiaquine before and after upscaling of seasonal malaria chemoprevention in seven African countries: a genomic surveillance study. THE LANCET. INFECTIOUS DISEASES 2023; 23:361-370. [PMID: 36328000 DOI: 10.1016/s1473-3099(22)00593-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Revised: 08/08/2022] [Accepted: 09/02/2022] [Indexed: 12/26/2022]
Abstract
BACKGROUND Seasonal malaria chemoprevention is used in 13 countries in the Sahel region of Africa to prevent malaria in children younger than 5 years. Resistance of Plasmodium falciparum to seasonal malaria chemoprevention drugs across the region is a potential threat to this intervention. METHODS Between December, 2015, and March, 2016, and between December, 2017, and March, 2018, immediately following the 2015 and 2017 malaria transmission seasons, community surveys were done among children younger than 5 years and individuals aged 10-30 years in districts implementing seasonal malaria chemoprevention with sulfadoxine-pyrimethamine and amodiaquine in Burkina Faso, Chad, Guinea, Mali, Nigeria, Niger and The Gambia. Dried blood samples were collected and tested for P falciparum DNA by PCR. Resistance-associated haplotypes of the P falciparum genes crt, mdr1, dhfr, and dhps were identified by quantitative PCR and sequencing of isolates from the collected samples, and survey-weighted prevalence and prevalence ratio between the first and second surveys were estimated for each variant. FINDINGS 5130 (17·5%) of 29 274 samples from 2016 and 2176 (7·6%) of 28 546 samples from 2018 were positive for P falciparum on quantitative PCR. Among children younger than 5 years, parasite carriage decreased from 2844 of 14 345 samples (19·8% [95% CI 19·2-20·5]) in 2016 to 801 of 14 019 samples (5·7% [5·3-6·1]) in 2018 (prevalence ratio 0·27 [95% CI 0·24-0·31], p<0·0001). Genotyping found no consistent evidence of increasing prevalence of amodiaquine resistance-associated variants of crt and mdr1 between 2016 and 2018. The dhfr haplotype IRN (consisting of 51Ile-59Arg-108Asn) was common at both survey timepoints, but the dhps haplotype ISGEAA (431Ile-436Ser-437Gly-540Glu-581Ala-613Ala), crucial for resistance to sulfadoxine-pyrimethamine, was always rare. Parasites carrying amodiaquine resistance-associated variants of both crt and mdr1 together with dhfr IRN and dhps ISGEAA occurred in 0·05% of isolates. The emerging dhps haplotype VAGKGS (431Val-436Ala-437Gly-540Lys-581Gly-613Ser) was present in four countries. INTERPRETATION In seven African countries, evidence of a significant reduction in parasite carriage among children receiving seasonal malaria chemoprevention was found 2 years after intervention scale-up. Combined resistance-associated haplotypes remained rare, and seasonal malaria chemoprevention with sulfadoxine-pyrimethamine and amodiaquine is expected to retain effectiveness. The threat of future erosion of effectiveness due to dhps variant haplotypes requires further monitoring. FUNDING Unitaid.
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Affiliation(s)
- Khalid B Beshir
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, UK
| | - Julian Muwanguzi
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, UK
| | - Johanna Nader
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, UK; Department of Genetics and Bioinformatics, Division of Health Data and Digitalization, Norwegian Institute of Public Health, Oslo, Norway
| | - Raoul Mansukhani
- Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, UK
| | - Aliou Traore
- Malaria Research and Training Centre, University of Bamako, Bamako, Mali
| | | | - Sainey Ceesay
- Medical Research Council Laboratories, London School of Hygiene & Tropical Medicine, Fajara, The Gambia
| | - Thomas Bazie
- Institute of Health Science Research, Bobo-Dioulasso, Burkina Faso
| | - Fassou Kolie
- Université Gamal Abdel Nasser de Conakry, Conakry, Guinea
| | | | - Matt Cairns
- Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, UK
| | - Paul Snell
- Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, UK
| | - Susana Scott
- Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, UK
| | | | - Corinne S Merle
- Special Programme for Research & Training in Tropical Diseases, WHO, Geneva, Switzerland
| | | | | | - Diego Moroso
- Malaria Consortium, Kampala, Uganda; UK Foreign, Commonwealth, & Development Office, Lagos, Nigeria
| | | | - Issaka Zongo
- Institute of Health Science Research, Bobo-Dioulasso, Burkina Faso
| | - Hamit Kessely
- Centre de Support en Santé Internationale, N'Djamena, Chad
| | | | - Kalifa Bojang
- Medical Research Council Laboratories, London School of Hygiene & Tropical Medicine, Fajara, The Gambia
| | - Serign Ceesay
- Medical Research Council Laboratories, London School of Hygiene & Tropical Medicine, Fajara, The Gambia
| | - Kovana Loua
- Université Gamal Abdel Nasser de Conakry, Conakry, Guinea
| | - Hamma Maiga
- Malaria Research and Training Centre, University of Bamako, Bamako, Mali
| | - Alassane Dicko
- Malaria Research and Training Centre, University of Bamako, Bamako, Mali
| | - Issaka Sagara
- Malaria Research and Training Centre, University of Bamako, Bamako, Mali
| | | | | | - Tony Eloike
- Jedima International Health Consult, Lagos, Nigeria
| | - Paul Milligan
- Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, UK
| | - Colin J Sutherland
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, UK.
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Temporal trends in molecular markers of drug resistance in Plasmodium falciparum in human blood and profiles of corresponding resistant markers in mosquito oocysts in Asembo, western Kenya. Malar J 2022; 21:265. [PMID: 36100912 PMCID: PMC9472345 DOI: 10.1186/s12936-022-04284-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Accepted: 08/30/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Over the last two decades, the scale-up of vector control and changes in the first-line anti-malarial, from chloroquine (CQ) to sulfadoxine-pyrimethamine (SP) and then to artemether-lumefantrine (AL), have resulted in significant decreases in malaria burden in western Kenya. This study evaluated the long-term effects of control interventions on molecular markers of Plasmodium falciparum drug resistance using parasites obtained from humans and mosquitoes at discrete time points. METHODS Dried blood spot samples collected in 2012 and 2017 community surveys in Asembo, Kenya were genotyped by Sanger sequencing for markers associated with resistance to SP (Pfdhfr, Pfdhps), CQ, AQ, lumefantrine (Pfcrt, Pfmdr1) and artemisinin (Pfk13). Temporal trends in the prevalence of these markers, including data from 2012 to 2017 as well as published data from 1996, 2001, 2007 from same area, were analysed. The same markers from mosquito oocysts collected in 2012 were compared with results from human blood samples. RESULTS The prevalence of SP dhfr/dhps quintuple mutant haplotype C50I51R59N108I164/S436G437E540A581A613 increased from 19.7% in 1996 to 86.0% in 2012, while an increase in the sextuple mutant haplotype C50I51R59N108I164/H436G437E540A581A613 containing Pfdhps-436H was found from 10.5% in 2012 to 34.6% in 2017. Resistant Pfcrt-76 T declined from 94.6% in 2007 to 18.3% in 2012 and 0.9% in 2017. Mutant Pfmdr1-86Y decreased across years from 74.8% in 1996 to zero in 2017, mutant Pfmdr1-184F and wild Pfmdr1-D1246 increased from 17.9% to 58.9% in 2007 to 55.9% and 90.1% in 2017, respectively. Pfmdr1 haplotype N86F184S1034N1042D1246 increased from 11.0% in 2007 to 49.6% in 2017. No resistant mutations in Pfk13 were found. Prevalence of Pfdhps-436H was lower while prevalence of Pfcrt-76 T was higher in mosquitoes than in human blood samples. CONCLUSION This study showed an increased prevalence of dhfr/dhps resistant markers over 20 years with the emergence of Pfdhps-436H mutant a decade ago in Asembo. The reversal of Pfcrt from CQ-resistant to CQ-sensitive genotype occurred following 19 years of CQ withdrawal. No Pfk13 markers associated with artemisinin resistance were detected, but the increased haplotype of Pfmdr1 N86F184S1034N1042D1246 was observed. The differences in prevalence of Pfdhps-436H and Pfcrt-76 T SNPs between two hosts and the role of mosquitoes in the transmission of drug resistant parasites require further investigation.
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Madkhali AM, Abdulhaq AA, Atroosh WM, Ghzwani AH, Zain KA, Ghailan KY, Hamali HA, Mobarki AA, Eisa ZM, Lau YL, Al-Mekhlafi HM. The return of chloroquine-sensitive Plasmodium falciparum parasites in Jazan region, southwestern Saudi Arabia over a decade after the adoption of artemisinin-based combination therapy: analysis of genetic mutations in the pfcrt gene. Parasitol Res 2021; 120:3771-3781. [PMID: 34561749 DOI: 10.1007/s00436-021-07323-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Accepted: 09/15/2021] [Indexed: 11/25/2022]
Abstract
This study investigated the polymorphism in the P. falciparum chloroquine resistance transporter (pfcrt) gene 11 years after chloroquine (CQ) cessation in Jazan region, southwestern Saudi Arabia. Two hundred and thirty-five P. falciparum isolates were amplified to detect mutations in the pfcrt gene. The pfcrt 76 T molecular marker for CQ resistance was detected in 66.4% (156/235) of the isolates, while the K76 CQ-sensitive wild type was detected in 33.6%. The pfcrt 74I and pfcrt 75E point mutations were each found to be present in 56.2% of isolates, while only four isolates (1.7%) were found to carry the pfcrt 72S mutation. Moreover, four pfcrt haplotypes were identified as follows: the CVIET triple-allele (56.2%), SVMET double-allele (1.7%) and CVMNT single-allele (8.5%) mutant haplotypes and the CVMNK wild haplotype (33.6%). The analysis also revealed significant associations between the prevalence of mutant pfcrt alleles and haplotypes and the age group, governorate and nationality of the patients as well as the parasitaemia level (p < 0.05). The findings provide evidence of the potential re-emergence of CQ-susceptible P. falciparum strains in Jazan region over a decade after CQ discontinuation, with about one third of the isolates analysed carrying the pfcrt K76 CQ-sensitive wild allele and the CVMNK ancestral wild haplotype. Although the reintroduction of CQ cannot be recommended at present in Saudi Arabia, these findings support the rationale for a potential future role for CQ in malaria treatment. Therefore, continuous molecular and in vitro monitoring mutations of pfcrt polymorphism in Jazan region is highly recommended.
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Affiliation(s)
- Aymen M Madkhali
- Department of Medical Laboratory Technology, Faculty of Applied Medical Sciences, Jazan University, Jazan, Kingdom of Saudi Arabia.,Medical Research Centre, Jazan University, Jazan, Kingdom of Saudi Arabia
| | - Ahmed A Abdulhaq
- Department of Medical Laboratory Technology, Faculty of Applied Medical Sciences, Jazan University, Jazan, Kingdom of Saudi Arabia
| | - Wahib M Atroosh
- Department of Parasitology, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Malaysia.,Department of Microbiology and Parasitology, Faculty of Medicine and Health Sciences, University of Aden, Aden, Yemen
| | | | - Khalid Ammash Zain
- Medical Research Centre, Jazan University, Jazan, Kingdom of Saudi Arabia
| | - Khalid Y Ghailan
- Faculty of Public Health and Tropical Medicine, Jazan University, Jazan, Kingdom of Saudi Arabia
| | - Hassan A Hamali
- Department of Medical Laboratory Technology, Faculty of Applied Medical Sciences, Jazan University, Jazan, Kingdom of Saudi Arabia
| | - Abdullah A Mobarki
- Department of Medical Laboratory Technology, Faculty of Applied Medical Sciences, Jazan University, Jazan, Kingdom of Saudi Arabia
| | - Zaki M Eisa
- Saudi Centre for Disease Prevention and Control, Ministry of Health, Jazan, Kingdom of Saudi Arabia
| | - Yee-Ling Lau
- Department of Parasitology, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Malaysia
| | - Hesham M Al-Mekhlafi
- Medical Research Centre, Jazan University, Jazan, Kingdom of Saudi Arabia. .,Department of Parasitology, Faculty of Medicine, University of Malaya, 50603, Kuala Lumpur, Malaysia. .,Department of Parasitology, Faculty of Medicine and Health Sciences, Sana'a University, Sana'a, Yemen.
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Chaturvedi R, Chhibber-Goel J, Verma I, Gopinathan S, Parvez S, Sharma A. Geographical spread and structural basis of sulfadoxine-pyrimethamine drug-resistant malaria parasites. Int J Parasitol 2021; 51:505-525. [PMID: 33775670 DOI: 10.1016/j.ijpara.2020.12.011] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 11/24/2020] [Accepted: 12/03/2020] [Indexed: 12/22/2022]
Abstract
The global spread of sulfadoxine (Sdx, S) and pyrimethamine (Pyr, P) resistance is attributed to increasing number of mutations in DHPS and DHFR enzymes encoded by malaria parasites. The association between drug resistance mutations and SP efficacy is complex. Here we provide an overview of the geographical spread of SP resistance mutations in Plasmodium falciparum (Pf) and Plasmodium vivax (Pv) encoded dhps and dhfr genes. In addition, we have collated the mutation data and mapped it on to the three-dimensional structures of DHPS and DHFR which have become available. Data from genomic databases and 286 studies were collated to provide a comprehensive landscape of mutational data from 2005 to 2019. Our analyses show that the Pyr-resistant double mutations are widespread in Pf/PvDHFR (P. falciparum ∼61% in Asia and the Middle East, and in the Indian sub-continent; in P. vivax ∼33% globally) with triple mutations prevailing in Africa (∼66%) and South America (∼33%). For PfDHPS, triple mutations dominate South America (∼44%), Asia and the Middle East (∼34%) and the Indian sub-continent (∼27%), while single mutations are widespread in Africa (∼45%). Contrary to the status for P. falciparum, Sdx-resistant single point mutations in PvDHPS dominate globally. Alarmingly, highly resistant quintuple and sextuple mutations are rising in Africa (PfDHFR-DHPS) and Asia (Pf/PvDHFR-DHPS). Structural analyses of DHFR and DHPS proteins in complexes with substrates/drugs have revealed that resistance mutations map proximal to Sdx and Pyr binding sites. Thus new studies can focus on discovery of novel inhibitors that target the non-substrate binding grooves in these two validated malaria parasite drug targets.
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Affiliation(s)
- Rini Chaturvedi
- Molecular Medicine Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, India; Department of Toxicology, Jamia Hamdard, New Delhi, India
| | - Jyoti Chhibber-Goel
- Molecular Medicine Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, India
| | - Ishika Verma
- Molecular Medicine Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, India
| | - Sreehari Gopinathan
- Molecular Medicine Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, India
| | - Suhel Parvez
- Department of Toxicology, Jamia Hamdard, New Delhi, India
| | - Amit Sharma
- Molecular Medicine Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, India; National Institute of Malaria Research, Dwarka, New Delhi, India.
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Myers-Hansen JL, Abuaku B, Oyebola MK, Mensah BA, Ahorlu C, Wilson MD, Awandare G, Koram KA, Ngwa AA, Ghansah A. Assessment of antimalarial drug resistant markers in asymptomatic Plasmodium falciparum infections after 4 years of indoor residual spraying in Northern Ghana. PLoS One 2020; 15:e0233478. [PMID: 33284800 PMCID: PMC7721464 DOI: 10.1371/journal.pone.0233478] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2020] [Accepted: 08/18/2020] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Drug resistance remains a concern for malaria control and elimination. The effect of interventions on its prevalence needs to be monitored to pre-empt further selection. We assessed the prevalence of Plasmodium falciparum gene mutations associated with resistance to the antimalarial drugs: sulfadoxine-pyrimethamine (SP), chloroquine (CQ) and artemisinin combination therapy (ACTs) after the scale-up of a vector control activity that reduced transmission. METHODS A total of 400 P. falciparum isolates from children under five years were genotyped for seventeen single nucleotide polymorphisms (SNPs) in pfcrt, pfmdr1, pfdhfr, pfdhps and pfk13 genes using polymerase chain reaction (PCR) and high resolution melting (HRM) analysis. These included 80 isolates, each randomly selected from cross-sectional surveys of asymptomatic infections across 2010 (baseline), 2011, 2012, 2013 (midline: post-IRS) and 2014 (endline: post-IRS) during the peak transmission season, when IRS intervention was rolled out in Bunkpurugu Yunyoo (BY) District, Ghana. The proportions of isolates with drug resistant alleles were assessed over this period. RESULTS There were significant decreases in the prevalence of pfdhfr- I51R59N108 haplotype from 2010 to 2014, while the decline in pfdhfr/pfdhps- I51R59N108G437 during the same period was not significant. The prevalence of lumefantrine (LM), mefloquine (MQ) and amodiaquine (AQ) resistance-associated haplotypes pfmdr1-N86F184D1246 and pfmdr1-Y86Y184Y1246 showed decreasing trends (z = -2.86, P = 0.004 and z = -2.71, P = 0.007, respectively). Each of pfcrt-T76 and pfmdr1-Y86 mutant alleles also showed a declining trend in the asymptomatic reservoir, after the IRS rollout in 2014 (z = -2.87, P = 0.004 and z = -2.65, P = 0.008, respectively). Similarly, Pyrimethamine resistance mediating polymorphisms pfdhfr-N108, pfdhfr-I51 and pfdhfr-R59 also declined (z = -2.03, P = 0.042, z = -3.54, P<0.001 and z = -4.63, P<0.001, respectively), but not the sulphadoxine resistance mediating pfdhps-G437 and pfdhps-F436 (z = -0.36, P = 0.715 and z = 0.41, P = 0.684, respectively). No mutant pfk13-Y580 were detected during the study period. CONCLUSION The study demonstrated declining trends in the prevalence of drug resistant mutations in asymptomatic P. falciparum infections following transmission reduction after an enhanced IRS intervention in Northern Ghana.
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Affiliation(s)
| | - Benjamin Abuaku
- Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | - Muyiwa K. Oyebola
- West African Center for Cell Biology of Infectious Pathogens, University of Ghana, Legon, Ghana
| | - Benedicta A. Mensah
- Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | - Collins Ahorlu
- Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | - Michael D. Wilson
- Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | - Gordon Awandare
- West African Center for Cell Biology of Infectious Pathogens, University of Ghana, Legon, Ghana
| | - Kwadwo A. Koram
- Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | | | - Anita Ghansah
- Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
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Jiang T, Cheng W, Yao Y, Tan H, Wu K, Li J. Molecular surveillance of anti-malarial resistance Pfdhfr and Pfdhps polymorphisms in African and Southeast Asia Plasmodium falciparum imported parasites to Wuhan, China. Malar J 2020; 19:434. [PMID: 33238987 PMCID: PMC7691106 DOI: 10.1186/s12936-020-03509-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 11/19/2020] [Indexed: 01/02/2023] Open
Abstract
Background Anti-malarial drug resistance is a severe challenge for eventual control and global elimination of malaria. Resistance to sulfadoxine-pyrimethamine (SP) increases as mutations accumulate in the Pfdhfr and Pfdhps genes. This study aimed to assess the polymorphisms and prevalence of mutation in these genes in the Plasmodium falciparum infecting migrant workers returning to Wuhan, China. Methods Blood samples were collected for 9 years (2011–2019). Parasite genomic DNA was extracted from blood spots on filter paper. The mutations were evaluated by nested PCR and sequencing. The single-nucleotide polymorphisms (SNPs) and haplotypes of the Pfdhfr and Pfdhps genes were analysed. Results Pfdhfr codon 108 showed a 94.7% mutation rate, while for Pfdhps, the rate for codon 437 was 79.0%. In total, five unique haplotypes at the Pfdhfr locus and 11 haplotypes at the Pfdhps locus were found while the Pfdhfr-Pfdhps combined loci revealed 28 unique haplotypes. A triple mutant (IRNI) of Pfdhfr was the most prevalent haplotype (84.4%). For Pfdhps, a single mutant (SGKAA) and a double mutant (SGEAA) were detected at frequencies of 37.8 and 22.3%, respectively. Among the combined haplotypes, a quadruple mutant (IRNI-SGKAA) was the most common, with a 30.0% frequency, followed by a quintuplet mutant (IRNI-SGEAA) with a frequency of 20.4%. Conclusion The high prevalence and saturation of Pfdhfr haplotypes and the medium prevalence of Pfdhps haplotypes demonstrated in the present data will provide support for predicting the status and progression of antifolate resistance in malaria-endemic regions and imported malaria in nonendemic areas. Additional interventions to evaluate and prevent SP resistance should be continuously considered.
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Affiliation(s)
- Tingting Jiang
- Department of Human Parasitology, School of Basic Medical Sciences, Hubei University of Medicine, Shiyan, 442000, China.,Department of Infectious Diseases, Renmin Hospital, Hubei University of Medicine, Shiyan, 442000, China
| | - Weijia Cheng
- Department of Human Parasitology, School of Basic Medical Sciences, Hubei University of Medicine, Shiyan, 442000, China.,Department of Infectious Diseases, Renmin Hospital, Hubei University of Medicine, Shiyan, 442000, China
| | - Yi Yao
- Department of Human Parasitology, School of Basic Medical Sciences, Hubei University of Medicine, Shiyan, 442000, China.,Department of Infectious Diseases, Renmin Hospital, Hubei University of Medicine, Shiyan, 442000, China
| | - Huabing Tan
- Department of Human Parasitology, School of Basic Medical Sciences, Hubei University of Medicine, Shiyan, 442000, China.,Department of Infectious Diseases, Renmin Hospital, Hubei University of Medicine, Shiyan, 442000, China
| | - Kai Wu
- Department of Schistosomiasis and Endemic Diseases, Wuhan City Center for Disease Prevention and Control, Wuhan, 430015, China.
| | - Jian Li
- Department of Human Parasitology, School of Basic Medical Sciences, Hubei University of Medicine, Shiyan, 442000, China. .,Department of Infectious Diseases, Renmin Hospital, Hubei University of Medicine, Shiyan, 442000, China.
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Pacheco MA, Schneider KA, Cheng Q, Munde EO, Ndege C, Onyango C, Raballah E, Anyona SB, Ouma C, Perkins DJ, Escalante AA. Changes in the frequencies of Plasmodium falciparum dhps and dhfr drug-resistant mutations in children from Western Kenya from 2005 to 2018: the rise of Pfdhps S436H. Malar J 2020; 19:378. [PMID: 33092587 PMCID: PMC7583259 DOI: 10.1186/s12936-020-03454-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Accepted: 10/18/2020] [Indexed: 01/29/2023] Open
Abstract
BACKGROUND Sulfadoxine-pyrimethamine (SP) is the only anti-malarial drug formulation approved for intermittent preventive treatment in pregnancy (IPTp). However, mutations in the Plasmodium falciparum dhfr (Pfdhfr) and dhps (Pfdhps) genes confer resistance to pyrimethamine and sulfadoxine, respectively. Here, the frequencies of SP resistance-associated mutations from 2005 to 2018 were compared in samples from Kenyan children with malaria residing in a holoendemic transmission region. METHODS Partial sequences of the Pfdhfr and Pfdhps genes were amplified and sequenced from samples collected in 2005 (n = 81), 2010 (n = 95), 2017 (n = 43), and 2018 (n = 55). The frequency of known mutations conferring resistance to pyrimethamine and sulfadoxine were estimated and compared. Since artemisinin-based combination therapy (ACT) is the current first-line treatment for malaria, the presence of mutations in the propeller domain of P. falciparum kelch13 gene (Pfk13) linked to ACT-delayed parasite clearance was studied in the 2017/18 samples. RESULTS Among other changes, the point mutation of Pfdhps S436H increased in frequency from undetectable in 2005 to 28% in 2017/18. Triple Pfdhfr mutant allele (CIRNI) increased in frequency from 84% in 2005 to 95% in 2017/18, while the frequency of Pfdhfr double mutant alleles declined (allele CICNI from 29% in 2005 to 6% in 2017/18, and CNRNI from 9% in 2005 to undetectable in 2010 and 2017/18). Thus, a multilocus Pfdhfr/Pfdhps genotype with six mutations (HGEAA/CIRNI), including Pfdhps S436H, increased in frequency from 2010 to 2017/18. Although none of the mutations associated with ACT-delayed parasite clearance was observed, the Pfk13 mutation A578S, the most widespread Pfk13 SNP found in Africa, was detected in low frequency (2.04%). CONCLUSIONS There were changes in SP resistance mutant allele frequencies, including an increase in the Pfdhps S436H. Although these patterns seem consistent with directional selection due to drug pressure, there is a lack of information to determine the actual cause of such changes. These results suggest incorporating molecular surveillance of Pfdhfr/Pfdhps mutations in the context of SP efficacy studies for intermittent preventive treatment in pregnancy (IPTp).
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Affiliation(s)
- M Andreína Pacheco
- Biology Department/Institute of Genomics and Evolutionary Medicine (iGEM), Temple University, Philadelphia, PA, USA
| | - Kristan A Schneider
- Department of Applied Computer and Biosciences, University of Applied Sciences Mittweida, Technikumplatz, Mittweida, Germany
| | - Qiuying Cheng
- Center for Global Health, University of New Mexico Health Sciences Center, Albuquerque, NM, USA
| | - Elly O Munde
- University of New Mexico-Kenya Global Health Programs, Kisumu, Siaya, Kenya
- Department of Clinical Medicine, School of Health Sciences, Kirinyaga University, Kerugoya, Kenya
| | - Caroline Ndege
- University of New Mexico-Kenya Global Health Programs, Kisumu, Siaya, Kenya
- Department of Biomedical Sciences and Technology, Maseno University, Maseno, Kenya
| | - Clinton Onyango
- University of New Mexico-Kenya Global Health Programs, Kisumu, Siaya, Kenya
- Department of Biomedical Sciences and Technology, Maseno University, Maseno, Kenya
| | - Evans Raballah
- University of New Mexico-Kenya Global Health Programs, Kisumu, Siaya, Kenya
- Department of Medical Laboratory Sciences, School of Public Health, Biomedical Sciences and Technology, Masinde Muliro University of Science and Technology, Kakamega, Kenya
| | - Samuel B Anyona
- University of New Mexico-Kenya Global Health Programs, Kisumu, Siaya, Kenya
- Department of Medical Biochemistry, School of Medicine, Maseno University, Maseno, Kenya
| | - Collins Ouma
- University of New Mexico-Kenya Global Health Programs, Kisumu, Siaya, Kenya
- Department of Biomedical Sciences and Technology, Maseno University, Maseno, Kenya
| | - Douglas J Perkins
- Center for Global Health, University of New Mexico Health Sciences Center, Albuquerque, NM, USA.
- University of New Mexico-Kenya Global Health Programs, Kisumu, Siaya, Kenya.
| | - Ananias A Escalante
- Biology Department/Institute of Genomics and Evolutionary Medicine (iGEM), Temple University, Philadelphia, PA, USA.
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Eboumbou Moukoko CE, Huang F, Nsango SE, Kojom Foko LP, Ebong SB, Epee Eboumbou P, Yan H, Sitchueng L, Garke B, Ayong L. K-13 propeller gene polymorphisms isolated between 2014 and 2017 from Cameroonian Plasmodium falciparum malaria patients. PLoS One 2019; 14:e0221895. [PMID: 31479501 PMCID: PMC6719859 DOI: 10.1371/journal.pone.0221895] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Accepted: 08/16/2019] [Indexed: 12/23/2022] Open
Abstract
The emergence of artemisinin-resistant parasites since the late 2000s at the border of Cambodia and Thailand poses serious threats to malaria control globally, particularly in Africa which bears the highest malaria transmission burden. This study aimed to obtain reliable data on the current state of the kelch13 molecular marker for artemisinin resistance in Plasmodium falciparum in Cameroon. DNA was extracted from the dried blood spots collected from epidemiologically distinct endemic areas in the Center, Littoral and North regions of Cameroon. Nested PCR products from the Kelch13-propeller gene were sequenced and analyzed on an ABI 3730XL automatic sequencer. Of 219 dried blood spots, 175 were sequenced successfully. We identified six K13 mutations in 2.9% (5/175) of samples, including 2 non-synonymous, the V589I allele had been reported in Africa already and one new allele E612K had not been reported yet. These two non-synonymous mutations were uniquely found in parasites from the Littoral region. One sample showed two synonymous mutations within the kelch13 gene. We also observed two infected samples with mixed K13 mutant and K13 wild-type infection. Taken together, our data suggested the circulation of the non-synonymous K13 mutations in Cameroon. Albeit no mutations known to be associated with parasite clearance delays in the study population, there is need for continuous surveillance for earlier detection of resistance as long as ACTs are used and scaled up in the community.
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Affiliation(s)
- Carole Else Eboumbou Moukoko
- Biological Sciences Department, Faculty of Medicine and Pharmaceutical Sciences, University of Douala, Douala, Cameroon
- Malaria Research Unit, Centre Pasteur Cameroon, Yaoundé, Cameroon
- * E-mail: , (CEEM); (FH)
| | - Fang Huang
- Malarial Department, National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, Shanghai, China
- * E-mail: , (CEEM); (FH)
| | - Sandrine Eveline Nsango
- Biological Sciences Department, Faculty of Medicine and Pharmaceutical Sciences, University of Douala, Douala, Cameroon
- Malaria Research Unit, Centre Pasteur Cameroon, Yaoundé, Cameroon
| | - Loic Pradel Kojom Foko
- Parasitology and Entomology Research Unit, Department of Animal Organisms, Faculty of Science, University of Douala, Douala, Cameroon
| | - Serge Bruno Ebong
- Animal Organisms Biology and Physiology Department, Faculty of Sciences, University of Douala, Douala, Cameroon
| | | | - He Yan
- Malarial Department, National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, Shanghai, China
| | - Livia Sitchueng
- Malaria Research Unit, Centre Pasteur Cameroon, Yaoundé, Cameroon
| | - Bouba Garke
- Centre Pasteur Cameroon, Garoua Center, Yaoundé, Cameroon
| | - Lawrence Ayong
- Malaria Research Unit, Centre Pasteur Cameroon, Yaoundé, Cameroon
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Dieng CC, Gonzalez L, Pestana K, Dhikrullahi SB, Amoah LE, Afrane YA, Lo E. Contrasting Asymptomatic and Drug Resistance Gene Prevalence of Plasmodium falciparum in Ghana: Implications on Seasonal Malaria Chemoprevention. Genes (Basel) 2019; 10:genes10070538. [PMID: 31315304 PMCID: PMC6678124 DOI: 10.3390/genes10070538] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Revised: 07/11/2019] [Accepted: 07/12/2019] [Indexed: 11/28/2022] Open
Abstract
Malaria is a significant public health problem in Ghana. Seasonal Malaria Chemoprevention (SMC) using a combination of sulfadoxine-pyrimethamine and amodiaquine has been implemented since 2015 in northern Ghana where malaria transmission is intense and seasonal. In this study, we estimated the prevalence of asymptomatic P. falciparum carriers in three ecological zones of Ghana, and compared the sensitivity and specificity of different molecular methods in identifying asymptomatic infections. Moreover, we examined the frequency of mutations in pfcrt, pfmdr1, pfdhfr, and pfdhps that relate to the ongoing SMC. A total of 535 asymptomatic schoolchildren were screened by microscopy and PCR (18s rRNA and TARE-2) methods. Among all samples, 28.6% were detected as positive by 18S nested PCR, whereas 19.6% were detected by microscopy. A high PCR-based asymptomatic prevalence was observed in the north (51%) compared to in the central (27.8%) and south (16.9%). The prevalence of pfdhfr-N51I/C59R/S108N/pfdhps-A437G quadruple mutant associated with sulfadoxine-pyrimethamine resistance was significantly higher in the north where SMC was implemented. Compared to 18S rRNA, TARE-2 serves as a more sensitive molecular marker for detecting submicroscopic asymptomatic infections in high and low transmission settings. These findings establish a baseline for monitoring P. falciparum prevalence and resistance in response to SMC over time.
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Affiliation(s)
- Cheikh Cambel Dieng
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223, USA.
| | - Lauren Gonzalez
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Kareen Pestana
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Shittu B Dhikrullahi
- Department of Medical Microbiology, College of Health Sciences, University of Ghana, P.O. Box LG 25, Accra, Ghana
| | - Linda E Amoah
- Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana
| | - Yaw A Afrane
- Department of Medical Microbiology, College of Health Sciences, University of Ghana, P.O. Box LG 25, Accra, Ghana
| | - Eugenia Lo
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223, USA.
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Okell LC, Reiter LM, Ebbe LS, Baraka V, Bisanzio D, Watson OJ, Bennett A, Verity R, Gething P, Roper C, Alifrangis M. Emerging implications of policies on malaria treatment: genetic changes in the Pfmdr-1 gene affecting susceptibility to artemether-lumefantrine and artesunate-amodiaquine in Africa. BMJ Glob Health 2018; 3:e000999. [PMID: 30397515 PMCID: PMC6202998 DOI: 10.1136/bmjgh-2018-000999] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Revised: 08/21/2018] [Accepted: 08/31/2018] [Indexed: 11/04/2022] Open
Abstract
Artemether–lumefantrine (AL) and artesunate–amodiaquine (AS-AQ) are the most commonly used artemisinin-based combination therapies (ACT) for treatment of Plasmodium falciparum in Africa. Both treatments remain efficacious, but single nucleotide polymorphisms (SNPs) in the Plasmodium falciparum multidrug resistance 1 (Pfmdr1) gene may compromise sensitivity. AL and AS-AQ exert opposing selective pressures: parasites with genotype 86Y, Y184 and 1246Y are partially resistant to AS-AQ treatment, while N86, 184 F and D1246 are favoured by AL treatment. Through a systematic review, we identified 397 surveys measuring the prevalence of Pfmdr1 polymorphisms at positions 86 184 or 1246 in 30 countries in Africa. Temporal trends in SNP frequencies after introduction of AL or AS-AQ as first-line treatment were analysed in 32 locations, and selection coefficients estimated. We examined associations between antimalarial policies, consumption, transmission intensity and rate of SNP selection. 1246Y frequency decreased on average more rapidly in locations where national policy recommended AL (median selection coefficient(s) of −0.083), compared with policies of AS-AQ or both AL and AS-AQ (median s=−0.035 and 0.021, p<0.001 respectively). 86Y frequency declined markedly after ACT policy introduction, with a borderline significant trend for a more rapid decline in countries with AL policies (p=0.055). However, these trends could also be explained by a difference in initial SNP frequencies at the time of ACT introduction. There were non-significant trends for faster selection of N86 and D1246 in areas with higher AL consumption and no trend with transmission intensity. Recorded consumption of AS-AQ was low in the locations and times Pfmdr1 data were collected. SNP trends in countries with AL policies suggest a broad increase in sensitivity of parasites to AS-AQ, by 7–10 years after AL introduction. Observed rates of selection have implications for planning strategies to cycle drugs or use multiple first-line therapies to maintain drug efficacy.
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Affiliation(s)
- Lucy C Okell
- MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, Imperial College London, London, UK
| | - Lisa Malene Reiter
- Global Health Section, Department of Public Health, University of Copenhagen, Copenhagen, Denmark
| | - Lene Sandø Ebbe
- Centre for Medical Parasitology, Department of Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark.,Department of Infectious Disease, Copenhagen University Hospital, Copenhagen, Denmark
| | - Vito Baraka
- Department of Biomedical Sciences, National Institute for Medical Research, Tanga, United Republic of Tanzania
| | - Donal Bisanzio
- RTI International, Washington, District of Columbia, USA
| | - Oliver J Watson
- MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, Imperial College London, London, UK
| | - Adam Bennett
- Malaria Elimination Initiative, Global Health Group, University of San FranciscO, San Francisco, California, USA
| | - Robert Verity
- MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, Imperial College London, London, UK
| | - Peter Gething
- Malaria Atlas Project, Oxford Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Cally Roper
- Department of Pathogen Molecular Biology, London School of Hygiene and Tropical Medicine, London, UK
| | - Michael Alifrangis
- Centre for Medical Parasitology, Department of Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark
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13
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Apinjoh TO, Mugri RN, Miotto O, Chi HF, Tata RB, Anchang-Kimbi JK, Fon EM, Tangoh DA, Nyingchu RV, Jacob C, Amato R, Djimde A, Kwiatkowski D, Achidi EA, Amambua-Ngwa A. Molecular markers for artemisinin and partner drug resistance in natural Plasmodium falciparum populations following increased insecticide treated net coverage along the slope of mount Cameroon: cross-sectional study. Infect Dis Poverty 2017; 6:136. [PMID: 29110722 PMCID: PMC5674235 DOI: 10.1186/s40249-017-0350-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Accepted: 08/09/2017] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND Drug resistance is one of the greatest challenges of malaria control programmes, with the monitoring of parasite resistance to artemisinins or to Artemisinin Combination Therapy (ACT) partner drugs critical to elimination efforts. Markers of resistance to a wide panel of antimalarials were assessed in natural parasite populations from southwestern Cameroon. METHODS Individuals with asymptomatic parasitaemia or uncomplicated malaria were enrolled through cross-sectional surveys from May 2013 to March 2014 along the slope of mount Cameroon. Plasmodium falciparum malaria parasitaemic blood, screened by light microscopy, was depleted of leucocytes using CF11 cellulose columns and the parasite genotype ascertained by sequencing on the Illumina HiSeq platform. RESULTS A total of 259 participants were enrolled in this study from three different altitudes. While some alleles associated with drug resistance in pfdhfr, pfmdr1 and pfcrt were highly prevalent, less than 3% of all samples carried mutations in the pfkelch13 gene, none of which were amongst those associated with slow artemisinin parasite clearance rates in Southeast Asia. The most prevalent haplotypes were triple mutants Pfdhfr I 51 R 59 N 108 I 164(99%), pfcrt- C72V73 I 74 E 75 T 76 (47.3%), and single mutants PfdhpsS436 G 437K540A581A613(69%) and Pfmdr1 N86 F 184D1246 (53.2%). CONCLUSIONS The predominance of the Pf pfcrt CVIET and Pf dhfr IRN triple mutant parasites and absence of pfkelch13 resistance alleles suggest that the amodiaquine and pyrimethamine components of AS-AQ and SP may no longer be effective in their role while chloroquine resistance still persists in southwestern Cameroon.
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Affiliation(s)
- Tobias O. Apinjoh
- Department of Biochemistry and Molecular Biology, University of Buea, Buea, Cameroon
| | - Regina N. Mugri
- Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
| | - Olivo Miotto
- Mahidol-Oxford Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Hanesh F. Chi
- Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
| | - Rolland B. Tata
- Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
| | | | - Eleanor M. Fon
- Department of Biochemistry and Molecular Biology, University of Buea, Buea, Cameroon
| | - Delphine A. Tangoh
- Department of Biochemistry and Molecular Biology, University of Buea, Buea, Cameroon
- Department of Medical Laboratory Science, University of Buea, Buea, Cameroon
| | - Robert V. Nyingchu
- Department of Biochemistry and Molecular Biology, University of Buea, Buea, Cameroon
- Department of Medical Laboratory Science, University of Buea, Buea, Cameroon
| | | | - Roberto Amato
- Wellcome Trust Sanger Institute, Hinxton, Cambridge, CB10 1SA UK
| | | | | | - Eric A. Achidi
- Department of Biochemistry and Molecular Biology, University of Buea, Buea, Cameroon
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14
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Using remote sensing environmental data to forecast malaria incidence at a rural district hospital in Western Kenya. Sci Rep 2017; 7:2589. [PMID: 28572680 PMCID: PMC5453969 DOI: 10.1038/s41598-017-02560-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Accepted: 04/13/2017] [Indexed: 01/11/2023] Open
Abstract
Malaria surveillance data provide opportunity to develop forecasting models. Seasonal variability in environmental factors correlate with malaria transmission, thus the identification of transmission patterns is useful in developing prediction models. However, with changing seasonal transmission patterns, either due to interventions or shifting weather seasons, traditional modelling approaches may not yield adequate predictive skill. Two statistical models,a general additive model (GAM) and GAMBOOST model with boosted regression were contrasted by assessing their predictive accuracy in forecasting malaria admissions at lead times of one to three months. Monthly admission data for children under five years with confirmed malaria at the Siaya district hospital in Western Kenya for the period 2003 to 2013 were used together with satellite derived data on rainfall, average temperature and evapotranspiration(ET). There was a total of 8,476 confirmed malaria admissions. The peak of malaria season changed and malaria admissions reduced overtime. The GAMBOOST model at 1-month lead time had the highest predictive skill during both the training and test periods and thus can be utilized in a malaria early warning system.
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15
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Lynch CA, Pearce R, Pota H, Egwang C, Egwang T, Bhasin A, Cox J, Abeku TA, Roper C. Travel and the emergence of high-level drug resistance in Plasmodium falciparum in southwest Uganda: results from a population-based study. Malar J 2017; 16:150. [PMID: 28415996 PMCID: PMC5392983 DOI: 10.1186/s12936-017-1812-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Accepted: 04/08/2017] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND The I164L mutation on the dhfr gene confers high level resistance to sulfadoxine-pyrimethamine (SP) but it is rare in Africa except in a cluster of reports where prevalence >10% in highland areas of southwest Uganda and eastern Rwanda. The occurrence of the dhfr I164L mutation was investigated in community surveys in this area and examined the relationship to migration. METHODS A cross-sectional prevalence survey was undertaken in among villages within the catchment areas of two health facilities in a highland site (Kabale) and a highland fringe site (Rukungiri) in 2007. Sociodemographic details, including recent migration, were collected for each person included in the study. A total of 206 Plasmodium falciparum positive subjects were detected by rapid diagnostic test; 203 in Rukungiri and 3 in Kabale. Bloodspot samples were taken and were screened for dhfr I164L. RESULTS Sequence analysis confirmed the presence of the I164L mutations in twelve P. falciparum positive samples giving an estimated prevalence of 8.6% in Rukungiri. Of the three parasite positive samples in Kabale, none had I164L mutations. Among the twelve I164L positives three were male, ages ranged from 5 to 90 years of age. None of those with the I164L mutation had travelled in the 8 weeks prior to the survey, although three were from households from which at least one household member had travelled during that period. Haplotypes were determined in non-mixed infections and showed the dhfr I164L mutation occurs in both as a N51I + S108N + I164L haplotype (n = 2) and N51I + C59R + S108N + I164L haplotype (n = 5). Genotyping of flanking microsatellite markers showed that the I164L occurred independently on the triple mutant (N51I, C59R + S108N) and double mutant (N51I + S108N) background. CONCLUSIONS There is sustained local transmission of parasites with the dhfr I164L mutation in Rukungiri and no evidence to indicate its occurrence is associated with recent travel to highly resistant neighbouring areas. The emergence of a regional cluster of I164L in SW Uganda and Rwanda indicates that transmission of I164L is facilitated by strong drug pressure in low transmission areas potentially catalysed in those areas by travel and the importation of parasites from relatively higher transmission settings.
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Affiliation(s)
- Caroline A Lynch
- Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, UK.
| | - Richard Pearce
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK
| | - Hirva Pota
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK
| | | | | | - Amit Bhasin
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK
| | - Jonathan Cox
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK
| | | | - Cally Roper
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK
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16
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Kateera F, Nsobya SL, Tukwasibwe S, Hakizimana E, Mutesa L, Mens PF, Grobusch MP, van Vugt M, Kumar N. Molecular surveillance of Plasmodium falciparum drug resistance markers reveals partial recovery of chloroquine susceptibility but sustained sulfadoxine-pyrimethamine resistance at two sites of different malaria transmission intensities in Rwanda. Acta Trop 2016; 164:329-336. [PMID: 27647575 PMCID: PMC10600949 DOI: 10.1016/j.actatropica.2016.09.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Revised: 09/01/2016] [Accepted: 09/05/2016] [Indexed: 12/23/2022]
Abstract
Faced with intense levels of chloroquine (CQ) resistance in Plasmodium falciparum malaria, Rwanda replaced CQ with amodiaquine (AQ)+sulfadoxine-pyrimethamine (SP) in 2001, and subsequently with artemether-lumefantrine (AL) in 2006, as first-line treatments for uncomplicated malaria. Following years of discontinuation of CQ use, re-emergence of CQ-susceptible parasites has been reported in countries including Malawi, Kenya and Tanzania. In contrast, high levels of SP resistant mutant parasites continue to be reported even in countries of presumed reduced SP drug selection pressure. The prevalence and distributions of genetic polymorphisms linked with CQ and SP resistance at two sites of different malaria transmission intensities are described here to better understand drug-related genomic adaptations over time and exposure to varying drug pressures in Rwanda. Using filter paper blood isolates collected from P. falciparum infected patients, DNA was extracted and a nested PCR performed to identify resistance-mediating polymorphisms in the pfcrt, pfmdr1, pfdhps and pfdhfr genes. Amplicons from a total of 399 genotyped samples were analysed by ligase detection reaction fluorescent microsphere assay. CQ susceptible pfcrt 76K and pfmdr1 86N wild-type parasites were found in about 50% and 81% of isolates, respectively. Concurrently, SP susceptible pfdhps double (437G-540E), pfdhfr triple (108N-51I-59R), quintuple pfdhps 437G-540E/pfdhfr 51I-59R-108N and sextuple haplotypes were found in about 84%, 85%, 74% and 18% of isolates, respectively. High-level SP resistance associated pfdhfr 164L and pfdhps 581G mutant prevalences were noted to decline. Mutations pfcrt 76T, pfdhfr 59R and pfdhfr 164L were found differentially distributed between the two study sites with the pfdhfr 164L mutants found only at Ruhuha site, eastern Rwanda. Overall, sustained intense levels of SP resistance mutations and a recovery of CQ susceptible parasites were found in this study following 7 years and 14 years of drug withdrawal from use, respectively. Most likely, the sustained high prevalence of resistant parasites is due to the use of DHFR/DHPS inhibitors like trimethoprim-sulfamethoxazole (TS) for the treatment of and prophylaxis against bacterial infections among HIV infected individuals as well as the continued use of IPTp-SP within the East and Central African regions for malaria prevention among pregnant women. With regard to CQ, the slow recovery of CQ susceptible parasites may have been caused partly by the continued use of CQ and/or CQ mimicking antimalarial drugs like AQ in spite of policies to withdraw it from Rwanda and the neighbouring countries of Uganda and Tanzania. Continued surveillance of P. falciparum CQ and SP associated polymorphisms is recommended for guiding future rational drug policy-making and mitigation of future risk of anti-malaria drug resistance development.
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Affiliation(s)
- Fredrick Kateera
- Medical Research Centre Division, Rwanda Biomedical Centre, PO Box 7162, Kigali, Rwanda; Centre of Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Division of Internal Medicine, Meibergdreef 9, 1100 DD, Amsterdam, The Netherlands.
| | - Sam L Nsobya
- Molecular Research Laboratory, Infectious Disease Research Collaboration (IDRC), New Mulago Hospital Complex, PO Box 7051, Kampala, Uganda; School of Biomedical Science, College of Medicine, Makerere University, Uganda.
| | - Steven Tukwasibwe
- Molecular Research Laboratory, Infectious Disease Research Collaboration (IDRC), New Mulago Hospital Complex, PO Box 7051, Kampala, Uganda.
| | - Emmanuel Hakizimana
- Medical Research Centre Division, Rwanda Biomedical Centre, PO Box 7162, Kigali, Rwanda; Malaria & Other Parasitic Diseases Division, Rwanda Biomedical Centre, Kigali, Rwanda.
| | - Leon Mutesa
- College of Medicine & Health Sciences, University of Rwanda, PO Box 3286, Kigali, Rwanda.
| | - Petra F Mens
- Centre of Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Division of Internal Medicine, Meibergdreef 9, 1100 DD, Amsterdam, The Netherlands; Royal Tropical Institute/Koninklijk Instituutvoor de Tropen, KIT Biomedical Research, Meibergdreef 39, 1105 AZ, Amsterdam, The Netherlands.
| | - Martin P Grobusch
- Centre of Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Division of Internal Medicine, Meibergdreef 9, 1100 DD, Amsterdam, The Netherlands.
| | - Michèle van Vugt
- Centre of Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Division of Internal Medicine, Meibergdreef 9, 1100 DD, Amsterdam, The Netherlands.
| | - Nirbhay Kumar
- Department of Tropical Medicine, School of Public Health and Tropical Medicine, Vector-Borne Infectious Disease Research Centre, Tulane University, 333S Liberty Street, Mail code 8317, New Orleans, LA 70112, United States.
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Maiga H, Lasry E, Diarra M, Sagara I, Bamadio A, Traore A, Coumare S, Bahonan S, Sangare B, Dicko Y, Diallo N, Tembely A, Traore D, Niangaly H, Dao F, Haidara A, Dicko A, Doumbo OK, Djimde AA. Seasonal Malaria Chemoprevention with Sulphadoxine-Pyrimethamine and Amodiaquine Selects Pfdhfr-dhps Quintuple Mutant Genotype in Mali. PLoS One 2016; 11:e0162718. [PMID: 27662368 PMCID: PMC5035027 DOI: 10.1371/journal.pone.0162718] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Accepted: 08/26/2016] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Seasonal malaria chemoprevention (SMC) with sulphadoxine-pyrimethamine (SP) plus amodiaquine (AQ) is being scaled up in Sahelian countries of West Africa. However, the potential development of Plasmodium falciparum resistance to the respective component drugs is a major concern. METHODS Two cross-sectional surveys were conducted before (August 2012) and after (June 2014) a pilot implementation of SMC in Koutiala, Mali. Children aged 3-59 months received 7 rounds of curative doses of SP plus AQ over two malaria seasons. Genotypes of P. falciparum Pfdhfr codons 51, 59 and 108; Pfdhps codons 437 and 540, Pfcrt codon 76 and Pfmdr1codon 86 were analyzed by PCR on DNA from samples collected before and after SMC, and in non-SMC patient population as controls (November 2014). RESULTS In the SMC population 191/662 (28.9%) and 85/670 (12.7%) of children were P. falciparum positive by microscopy and were included in the molecular analysis before (2012) and after SMC implementation (2014), respectively. In the non-SMC patient population 220/310 (71%) were successfully PCR analyzed. In the SMC children, the prevalence of all molecular markers of SP resistance increased significantly after SMC including the Pfdhfr-dhps quintuple mutant genotype, which was 1.6% before but 7.1% after SMC (p = 0.02). The prevalence of Pfmdr1-86Y significantly decreased from 26.7% to 15.3% (p = 0.04) while no significant change was seen for Pfcrt 76T. In 2014, prevalence of all molecular markers of SP resistance were significantly higher among SMC children compared to the non-SMC population patient (p < 0.01). No Pfdhfr-164 mutation was found neither at baseline nor post SMC. CONCLUSION SMC increased the prevalence of molecular markers of P. falciparum resistance to SP in the treated children. However, there was no significant increase of these markers of resistance in the general parasite population after 2 years and 7 rounds of SMC.
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Affiliation(s)
- Hamma Maiga
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Medicine and Odontostomatology and Faculty of Pharmacy, University of Sciences, Techniques and Technologies of Bamako, Mali
| | - Estrella Lasry
- Médecins Sans Frontières (MSF), New York, New York, United States of America
| | - Modibo Diarra
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Medicine and Odontostomatology and Faculty of Pharmacy, University of Sciences, Techniques and Technologies of Bamako, Mali
| | - Issaka Sagara
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Medicine and Odontostomatology and Faculty of Pharmacy, University of Sciences, Techniques and Technologies of Bamako, Mali
| | - Amadou Bamadio
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Medicine and Odontostomatology and Faculty of Pharmacy, University of Sciences, Techniques and Technologies of Bamako, Mali
| | - Aliou Traore
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Medicine and Odontostomatology and Faculty of Pharmacy, University of Sciences, Techniques and Technologies of Bamako, Mali
| | - Samba Coumare
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Medicine and Odontostomatology and Faculty of Pharmacy, University of Sciences, Techniques and Technologies of Bamako, Mali
| | | | - Boubou Sangare
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Medicine and Odontostomatology and Faculty of Pharmacy, University of Sciences, Techniques and Technologies of Bamako, Mali
| | - Yeyia Dicko
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Medicine and Odontostomatology and Faculty of Pharmacy, University of Sciences, Techniques and Technologies of Bamako, Mali
| | - Nouhoum Diallo
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Medicine and Odontostomatology and Faculty of Pharmacy, University of Sciences, Techniques and Technologies of Bamako, Mali
| | - Aly Tembely
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Medicine and Odontostomatology and Faculty of Pharmacy, University of Sciences, Techniques and Technologies of Bamako, Mali
| | - Djibril Traore
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Medicine and Odontostomatology and Faculty of Pharmacy, University of Sciences, Techniques and Technologies of Bamako, Mali
| | - Hamidou Niangaly
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Medicine and Odontostomatology and Faculty of Pharmacy, University of Sciences, Techniques and Technologies of Bamako, Mali
| | - François Dao
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Medicine and Odontostomatology and Faculty of Pharmacy, University of Sciences, Techniques and Technologies of Bamako, Mali
| | - Aboubecrine Haidara
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Medicine and Odontostomatology and Faculty of Pharmacy, University of Sciences, Techniques and Technologies of Bamako, Mali
| | - Alassane Dicko
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Medicine and Odontostomatology and Faculty of Pharmacy, University of Sciences, Techniques and Technologies of Bamako, Mali
| | - Ogobara K. Doumbo
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Medicine and Odontostomatology and Faculty of Pharmacy, University of Sciences, Techniques and Technologies of Bamako, Mali
| | - Abdoulaye A. Djimde
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Medicine and Odontostomatology and Faculty of Pharmacy, University of Sciences, Techniques and Technologies of Bamako, Mali
- * E-mail:
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Genetic diversity of Plasmodium falciparum parasite by microsatellite markers after scale-up of insecticide-treated bed nets in western Kenya. Malar J 2015; 13 Suppl 1:495. [PMID: 26651480 PMCID: PMC4675068 DOI: 10.1186/s12936-015-1003-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 11/19/2015] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND An initial study of genetic diversity of Plasmodium falciparum in Asembo, western Kenya showed that the parasite maintained overall genetic stability 5 years after insecticide-treated bed net (ITN) introduction in 1997. This study investigates further the genetic diversity of P. falciparum 10 years after initial ITN introduction in the same study area and compares this with two other neighbouring areas, where ITNs were introduced in 1998 (Gem) and 2004 (Karemo). METHODS From a cross-sectional survey conducted in 2007, 235 smear-positive blood samples collected from children ≤15-year-old in the original study area and two comparison areas were genotyped employing eight neutral microsatellites. Differences in multiple infections, allele frequency, parasite genetic diversity and parasite population structure between the three areas were assessed. Further, molecular data reported previously (1996 and 2001) were compared to the 2007 results in the original study area Asembo. RESULTS Overall proportion of multiple infections (MA) declined with time in the original study area Asembo (from 95.9 %-2001 to 87.7 %-2007). In the neighbouring areas, MA was lower in the site where ITNs were introduced in 1998 (Gem 83.7 %) compared to where they were introduced in 2004 (Karemo 96.7 %) in 2007. Overall mean allele count (MAC ~ 2.65) and overall unbiased heterozygosity (H e ~ 0.77) remained unchanged in 1996, 2001 and 2007 in Asembo and was the same level across the two neighbouring areas in 2007. Overall parasite population differentiation remained low over time and in the three areas at FST < 0.04. Both pairwise and multilocus linkage disequilibrium showed limited to no significant association between alleles in Asembo (1996, 2001 and 2007) and between three areas. CONCLUSIONS This study showed the P. falciparum high genetic diversity and parasite population resilience on samples collected 10 years apart and in different areas in western Kenya. The results highlight the need for long-term molecular monitoring after implementation and use of combined and intensive prevention and intervention measures in the region.
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In Vitro and Molecular Surveillance for Antimalarial Drug Resistance in Plasmodium falciparum Parasites in Western Kenya Reveals Sustained Artemisinin Sensitivity and Increased Chloroquine Sensitivity. Antimicrob Agents Chemother 2015; 59:7540-7. [PMID: 26392510 DOI: 10.1128/aac.01894-15] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Accepted: 09/16/2015] [Indexed: 01/06/2023] Open
Abstract
Malaria control is hindered by the evolution and spread of resistance to antimalarials, necessitating multiple changes to drug policies over time. A comprehensive antimalarial drug resistance surveillance program is vital for detecting the potential emergence of resistance to antimalarials, including current artemisinin-based combination therapies. An antimalarial drug resistance surveillance study involving 203 Plasmodium falciparum malaria-positive children was conducted in western Kenya between 2010 and 2013. Specimens from enrolled children were analyzed in vitro for sensitivity to chloroquine (CQ), amodiaquine (AQ), mefloquine (MQ), lumefantrine, and artemisinin derivatives (artesunate and dihydroartemisinin) and for drug resistance allele polymorphisms in P. falciparum crt (Pfcrt), Pfmdr-1, and the K13 propeller domain (K13). We observed a significant increase in the proportion of samples with the Pfcrt wild-type (CVMNK) genotype, from 61.2% in 2010 to 93.0% in 2013 (P < 0.0001), and higher proportions of parasites with elevated sensitivity to CQ in vitro. The majority of isolates harbored the wild-type N allele in Pfmdr-1 codon 86 (93.5%), with only 7 (3.50%) samples with the N86Y mutant allele (the mutant nucleotide is underlined). Likewise, most isolates harbored the wild-type Pfmdr-1 D1246 allele (79.8%), with only 12 (6.38%) specimens with the D1246Y mutant allele and 26 (13.8%) with mixed alleles. All the samples had a single copy of the Pfmdr-1 gene (mean of 0.907 ± 0.141 copies). None of the sequenced parasites had mutations in K13. Our results suggest that artemisinin is likely to remain highly efficacious and that CQ sensitivity appears to be on the rise in western Kenya.
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Prevalence of Plasmodium falciparum resistance markers to sulfadoxine-pyrimethamine among pregnant women receiving intermittent preventive treatment for malaria in Uganda. Antimicrob Agents Chemother 2015; 59:5475-82. [PMID: 26124154 DOI: 10.1128/aac.00507-15] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Accepted: 06/17/2015] [Indexed: 01/13/2023] Open
Abstract
The aim of this study was to assess the prevalence of mutations in Plasmodium falciparum dihydrofolate reductase (Pfdhfr) and dihydropteroate synthase (Pfdhps) genes among pregnant women using sulfadoxine-pyrimethamine (SP) as an intermittent preventive treatment (IPTp). A molecular epidemiological study of P. falciparum parasite resistance markers to SP was conducted from August 2010 to February 2012 in Mukono district in central Uganda. DNA was extracted from 413 P. falciparum-positive samples. Real-time PCR, followed by melting curve analysis, was used to characterize point mutations in the Pfdhfr and Pfdhps genes that are associated with SP resistance. The prevalence of the single-nucleotide mutations in Pfdhfr at codons 51I, 59R, and 108N and in Pfdhps at codons 437G and 540E was high (>98%), reaching 100% fixation after one dose of SP, while the prevalence of 581G was 3.3% at baseline, reaching 12.5% after one dose of SP. At baseline, the prevalence of Pfdhfr and Pfdhps quintuple mutations was 89%, whereas the sextuple mutations (including 581G) were not prevalent (3.9%), reaching 16.7% after one dose of SP. However, the numbers of infections at follow-up visits were small, and hence there was insufficient statistical power to test whether there was a true rise in the prevalence of this allele. The overall high frequency of Pfdhfr and Pfdhps quintuple mutations throughout pregnancy excluded further analyses of possible associations between certain haplotypes and the risk of lower birth weight and anemia. However, women infected with P. falciparum had 1.3-g/dl-lower hemoglobin levels (P = 0.001) and delivered babies with a 400-g-lower birth weight (P = 0.001) compared to nonparasitemic women. Despite this, 44 women who were P. falciparum positive at baseline became negative after one or two doses of SP (i.e., 50.5%), implying that SP-IPTp still has some efficacy. P. falciparum resistance markers to SP are high in this population, whereas P. falciparum infection was associated with poor birth outcomes.
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