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Connelly SV, Brazeau NF, Msellem M, Ngasala BE, Aydemir O, Goel V, Niaré K, Giesbrecht DJ, Popkin-Hall ZR, Hennelly C, Park Z, Moormann AM, Ong'echa JM, Verity R, Mohammed S, Shija SJ, Mhamilawa LE, Morris U, Mårtensson A, Lin JT, Björkman A, Juliano JJ, Bailey JA. Strong isolation by distance and evidence of population microstructure reflect ongoing Plasmodium falciparum transmission in Zanzibar. eLife 2024; 12:RP90173. [PMID: 38935423 PMCID: PMC11210957 DOI: 10.7554/elife.90173] [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: 06/28/2024] Open
Abstract
Background The Zanzibar archipelago of Tanzania has become a low-transmission area for Plasmodium falciparum. Despite being considered an area of pre-elimination for years, achieving elimination has been difficult, likely due to a combination of imported infections from mainland Tanzania and continued local transmission. Methods To shed light on these sources of transmission, we applied highly multiplexed genotyping utilizing molecular inversion probes to characterize the genetic relatedness of 282 P. falciparum isolates collected across Zanzibar and in Bagamoyo district on the coastal mainland from 2016 to 2018. Results Overall, parasite populations on the coastal mainland and Zanzibar archipelago remain highly related. However, parasite isolates from Zanzibar exhibit population microstructure due to the rapid decay of parasite relatedness over very short distances. This, along with highly related pairs within shehias, suggests ongoing low-level local transmission. We also identified highly related parasites across shehias that reflect human mobility on the main island of Unguja and identified a cluster of highly related parasites, suggestive of an outbreak, in the Micheweni district on Pemba island. Parasites in asymptomatic infections demonstrated higher complexity of infection than those in symptomatic infections, but have similar core genomes. Conclusions Our data support importation as a main source of genetic diversity and contribution to the parasite population in Zanzibar, but they also show local outbreak clusters where targeted interventions are essential to block local transmission. These results highlight the need for preventive measures against imported malaria and enhanced control measures in areas that remain receptive to malaria reemergence due to susceptible hosts and competent vectors. Funding This research was funded by the National Institutes of Health, grants R01AI121558, R01AI137395, R01AI155730, F30AI143172, and K24AI134990. Funding was also contributed from the Swedish Research Council, Erling-Persson Family Foundation, and the Yang Fund. RV acknowledges funding from the MRC Centre for Global Infectious Disease Analysis (reference MR/R015600/1), jointly funded by the UK Medical Research Council (MRC) and the UK Foreign, Commonwealth & Development Office (FCDO), under the MRC/FCDO Concordat agreement and is also part of the EDCTP2 program supported by the European Union. RV also acknowledges funding by Community Jameel.
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Affiliation(s)
- Sean V Connelly
- MD-PhD Program, University of North Carolina at Chapel HillChapel HillUnited States
| | - Nicholas F Brazeau
- MD-PhD Program, University of North Carolina at Chapel HillChapel HillUnited States
| | - Mwinyi Msellem
- Research Division, Ministry of HealthZanzibarUnited Republic of Tanzania
| | - Billy E Ngasala
- Department of Parasitology and Medical Entomology, Muhimbili University of Health and Allied SciencesDar es SalaamUnited Republic of Tanzania
- Global Health and Migration Unit, Department of Women's and Children's Health, Uppsala UniversityUppsalaSweden
| | - Ozkan Aydemir
- Department of Medicine, University of Massachusetts Chan Medical SchoolWorcesterUnited States
| | - Varun Goel
- Carolina Population Center, University of North Carolina at Chapel HillChapel HillUnited States
| | - Karamoko Niaré
- Department of Pathology and Laboratory Medicine, Brown UniversityProvidenceUnited States
| | - David J Giesbrecht
- Department of Pathology and Laboratory Medicine, Brown UniversityProvidenceUnited States
| | - Zachary R Popkin-Hall
- Institute for Global Health and Infectious Diseases, School of Medicine, University of North Carolina at Chapel HillChapel HillUnited States
| | - Chris Hennelly
- Institute for Global Health and Infectious Diseases, School of Medicine, University of North Carolina at Chapel HillChapel HillUnited States
| | - Zackary Park
- Division of Infectious Diseases, Department of Medicine, School of Medicine, University of North Carolina at Chapel HillChapel HillUnited States
| | - Ann M Moormann
- Department of Medicine, University of Massachusetts Chan Medical SchoolWorcesterUnited States
| | - John M Ong'echa
- Center for Global Health Research, Kenya Medical Research InstituteKisumuKenya
| | - Robert Verity
- MRC Centre for Global Infectious Disease Analysis, Imperial College LondonLondonUnited Kingdom
| | - Safia Mohammed
- Zanzibar Malaria Elimination Program (ZAMEP)ZanzibarUnited Republic of Tanzania
| | - Shija J Shija
- Zanzibar Malaria Elimination Program (ZAMEP)ZanzibarUnited Republic of Tanzania
| | - Lwidiko E Mhamilawa
- Department of Parasitology and Medical Entomology, Muhimbili University of Health and Allied SciencesDar es SalaamUnited Republic of Tanzania
- Global Health and Migration Unit, Department of Women's and Children's Health, Uppsala UniversityUppsalaSweden
| | - Ulrika Morris
- Department of Microbiology, Tumor and Cell Biology, Karolinska InstitutetStockholmSweden
| | - Andreas Mårtensson
- Global Health and Migration Unit, Department of Women's and Children's Health, Uppsala UniversityUppsalaSweden
| | - Jessica T Lin
- Division of Infectious Diseases, Department of Medicine, School of Medicine, University of North Carolina at Chapel HillChapel HillUnited States
| | - Anders Björkman
- Department of Microbiology, Tumor and Cell Biology, Karolinska InstitutetStockholmSweden
- Department of Global Public Health, Karolinska InstituteStockholmSweden
| | - Jonathan J Juliano
- Division of Infectious Diseases, Department of Medicine, School of Medicine, University of North Carolina at Chapel HillChapel HillUnited States
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel HillChapel HillUnited States
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel HillChapel HillUnited States
| | - Jeffrey A Bailey
- Department of Pathology and Laboratory Medicine, Brown UniversityProvidenceUnited States
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Diffendall G, Claes A, Barcons-Simon A, Nyarko P, Dingli F, Santos MM, Loew D, Claessens A, Scherf A. RNA polymerase III is involved in regulating Plasmodium falciparum virulence. eLife 2024; 13:RP95879. [PMID: 38921824 PMCID: PMC11208047 DOI: 10.7554/elife.95879] [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: 06/27/2024] Open
Abstract
While often undetected and untreated, persistent seasonal asymptomatic malaria infections remain a global public health problem. Despite the presence of parasites in the peripheral blood, no symptoms develop. Disease severity is correlated with the levels of infected red blood cells (iRBCs) adhering within blood vessels. Changes in iRBC adhesion capacity have been linked to seasonal asymptomatic malaria infections, however how this is occurring is still unknown. Here, we present evidence that RNA polymerase III (RNA Pol III) transcription in Plasmodium falciparum is downregulated in field isolates obtained from asymptomatic individuals during the dry season. Through experiments with in vitro cultured parasites, we have uncovered an RNA Pol III-dependent mechanism that controls pathogen proliferation and expression of a major virulence factor in response to external stimuli. Our findings establish a connection between P. falciparum cytoadhesion and a non-coding RNA family transcribed by Pol III. Additionally, we have identified P. falciparum Maf1 as a pivotal regulator of Pol III transcription, both for maintaining cellular homeostasis and for responding adaptively to external signals. These results introduce a novel perspective that contributes to our understanding of P. falciparum virulence. Furthermore, they establish a connection between this regulatory process and the occurrence of seasonal asymptomatic malaria infections.
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Affiliation(s)
- Gretchen Diffendall
- Institut Pasteur, Universite Paris CitéParisFrance
- Institut Pasteur, Sorbonne Université Ecole doctorale Complexité du VivantParisFrance
| | | | - Anna Barcons-Simon
- Institut Pasteur, Universite Paris CitéParisFrance
- Institut Pasteur, Sorbonne Université Ecole doctorale Complexité du VivantParisFrance
- Institut Pasteur, Biomedical Center, Division of Physiological Chemistry, Faculty of Medicine, Ludwig-Maximilians-Universität MünchenMunichGermany
| | - Prince Nyarko
- Institut Pasteur, Laboratory of Pathogen-Host Interaction (LPHI), CNRS, University of MontpellierMontpellierFrance
| | - Florent Dingli
- Institut Pasteur, Institut Curie, PSL Research University, Centre de Recherche, CurieCoreTech Mass Spectrometry ProteomicsParisFrance
| | - Miguel M Santos
- Institut Pasteur, Instituto de Medicina Molecular João Lobo Antunes, Faculdade de Medicina da Universidade de LisboaLisboaPortugal
| | - Damarys Loew
- Institut Pasteur, Institut Curie, PSL Research University, Centre de Recherche, CurieCoreTech Mass Spectrometry ProteomicsParisFrance
| | - Antoine Claessens
- Institut Pasteur, Laboratory of Pathogen-Host Interaction (LPHI), CNRS, University of MontpellierMontpellierFrance
- Institut Pasteur, LPHI, MIVEGEC, CNRS, INSERM, University of MontpellierMontpellierFrance
| | - Artur Scherf
- Institut Pasteur, Universite Paris CitéParisFrance
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Soremekun S, Conteh B, Nyassi A, Soumare HM, Etoketim B, Ndiath MO, Bradley J, D'Alessandro U, Bousema T, Erhart A, Moreno M, Drakeley C. Household-level effects of seasonal malaria chemoprevention in the Gambia. COMMUNICATIONS MEDICINE 2024; 4:97. [PMID: 38778226 PMCID: PMC11111771 DOI: 10.1038/s43856-024-00503-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Accepted: 04/18/2024] [Indexed: 05/25/2024] Open
Abstract
BACKGROUND In 2022 the WHO recommended the discretionary expansion of the eligible age range for seasonal malaria chemoprevention (SMC) to children older than 4 years. Older children are at lower risk of clinical disease and severe malaria so there has been uncertainty about the cost-benefit for national control programmes. However, emerging evidence from laboratory studies suggests protecting school-age children reduces the infectious reservoir for malaria and may significantly impact on transmission. This study aimed to assess whether these effects were detectable in the context of a routinely delivered SMC programme. METHODS In 2021 the Gambia extended the maximum eligible age for SMC from 4 to 9 years. We conducted a prospective population cohort study over the 2021 malaria transmission season covering 2210 inhabitants of 10 communities in the Upper River Region, and used a household-level mixed modelling approach to quantify impacts of SMC on malaria transmission. RESULTS We demonstrate that the hazard of clinical malaria in older participants aged 10+ years ineligible for SMC decreases by 20% for each additional SMC round per child 0-9 years in the same household. Older inhabitants also benefit from reduced risk of asymptomatic infections in high SMC coverage households. Spatial autoregression tests show impacts are highly localised, with no detectable spillover from nearby households. CONCLUSIONS Evidence for the transmission-reducing effects of extended-age SMC from routine programmes implemented at scale has been previously limited. Here we demonstrate benefits to the entire household, indicating such programmes may be more cost-effective than previously estimated.
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Affiliation(s)
- Seyi Soremekun
- Department of Infection Biology, London School of Hygiene & Tropical Medicine, Keppel Street, London, UK.
| | - Bakary Conteh
- Medical Research Council Unit The Gambia at the London School of Hygiene & Tropical Medicine, Banjul, The Gambia
| | - Abdoullah Nyassi
- Medical Research Council Unit The Gambia at the London School of Hygiene & Tropical Medicine, Banjul, The Gambia
| | - Harouna M Soumare
- Medical Research Council Unit The Gambia at the London School of Hygiene & Tropical Medicine, Banjul, The Gambia
| | - Blessed Etoketim
- Medical Research Council Unit The Gambia at the London School of Hygiene & Tropical Medicine, Banjul, The Gambia
| | - Mamadou Ousmane Ndiath
- Medical Research Council Unit The Gambia at the London School of Hygiene & Tropical Medicine, Banjul, The Gambia
| | - John Bradley
- Medical Research Council International Statistics and Epidemiology Group, London School of Hygiene & Tropical Medicine, Keppel Street, London, UK
| | - Umberto D'Alessandro
- Medical Research Council Unit The Gambia at the London School of Hygiene & Tropical Medicine, Banjul, The Gambia
| | - Teun Bousema
- Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Annette Erhart
- Medical Research Council Unit The Gambia at the London School of Hygiene & Tropical Medicine, Banjul, The Gambia
| | - Marta Moreno
- Department of Infection Biology, London School of Hygiene & Tropical Medicine, Keppel Street, London, UK
| | - Chris Drakeley
- Department of Infection Biology, London School of Hygiene & Tropical Medicine, Keppel Street, London, UK.
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4
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Connelly SV, Brazeau NF, Msellem M, Ngasala BE, Aydemir Ö, Goel V, Niaré K, Giesbrecht DJ, Popkin-Hall ZR, Hennelly CM, Park Z, Moormann AM, Ong'echa JM, Verity R, Mohammed S, Shija SJ, Mhamilawa LE, Morris U, Mårtensson A, Lin JT, Björkman A, Juliano JJ, Bailey JA. Strong isolation by distance and evidence of population microstructure reflect ongoing Plasmodium falciparum transmission in Zanzibar. MEDRXIV : THE PREPRINT SERVER FOR HEALTH SCIENCES 2024:2023.02.15.23285960. [PMID: 36865135 PMCID: PMC9980253 DOI: 10.1101/2023.02.15.23285960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The Zanzibar archipelago of Tanzania has become a low-transmission area for Plasmodium falciparum. Despite being considered an area of pre-elimination for years, achieving elimination has been difficult, likely due to a combination of imported infections from mainland Tanzania, and continued local transmission. To shed light on these sources of transmission, we applied highly multiplexed genotyping utilizing molecular inversion probes to characterize the genetic relatedness of 282 P. falciparum isolates collected across Zanzibar and in Bagamoyo District on the coastal mainland from 2016-2018. Overall, parasite populations on the coastal mainland and Zanzibar archipelago remain highly related. However, parasite isolates from Zanzibar exhibit population microstructure due to rapid decay of parasite relatedness over very short distances. This, along with highly related pairs within shehias, suggests ongoing low level local transmission. We also identified highly related parasites across shehias that reflect human mobility on the main island of Unguja and identified a cluster of highly related parasites, suggestive of an outbreak, in the Micheweni district on Pemba island. Parasites in asymptomatic infections demonstrated higher complexity of infection than those in symptomatic infections, but have similar core genomes. Our data support importation as a main source of genetic diversity and contribution to the parasite population on Zanzibar, but they also show local outbreak clusters where targeted interventions are essential to block local transmission. These results highlight the need for preventive measures against imported malaria and enhanced control measures in areas that remain receptive for malaria reemergence due to susceptible hosts and competent vectors.
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Affiliation(s)
- Sean V Connelly
- MD-PhD Program, University of North Carolina, Chapel Hill, NC 27599
| | | | - Mwinyi Msellem
- Research Division, Ministry of Health, Zanzibar, Tanzania
| | - Billy E Ngasala
- Department of Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
- Global Health and Migration Unit, Department of Women's and Children's Health, Uppsala University, Uppsala, Sweden
| | - Özkan Aydemir
- Department of Medicine, University of Massachusetts Chan Medical School, Worcester, MA
| | - Varun Goel
- Carolina Population Center, University of North Carolina, Chapel Hill, NC 27599
| | - Karamoko Niaré
- Department of Pathology and Laboratory Medicine, Brown University, Providence, RI, 02912 USA
| | - David J Giesbrecht
- Department of Pathology and Laboratory Medicine, Brown University, Providence, RI, 02912 USA
| | - Zachary R Popkin-Hall
- Institute for Global Health and Infectious Diseases, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599 USA
| | - Christopher M Hennelly
- Institute for Global Health and Infectious Diseases, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599 USA
| | - Zackary Park
- Division of Infectious Diseases, Department of Medicine, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599 USA
| | - Ann M Moormann
- Department of Medicine, University of Massachusetts Chan Medical School, Worcester, MA
| | | | - Robert Verity
- MRC Centre for Global Infectious Disease Analysis, Imperial College, London
| | - Safia Mohammed
- Zanzibar Malaria Elimination Program (ZAMEP), Zanzibar, Tanzania
| | - Shija J Shija
- Zanzibar Malaria Elimination Program (ZAMEP), Zanzibar, Tanzania
| | - Lwidiko E Mhamilawa
- Department of Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
- Global Health and Migration Unit, Department of Women's and Children's Health, Uppsala University, Uppsala, Sweden
| | - Ulrika Morris
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, 17177 Stockholm, Sweden
| | - Andreas Mårtensson
- Global Health and Migration Unit, Department of Women's and Children's Health, Uppsala University, Uppsala, Sweden
| | - Jessica T Lin
- Division of Infectious Diseases, Department of Medicine, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599 USA
| | - Anders Björkman
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, 17177 Stockholm, Sweden
- Department of Global Public Health, Karolinska Institutet, Stockholm, Sweden
| | - Jonathan J Juliano
- Division of Infectious Diseases, Department of Medicine, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599 USA
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, 27599 USA
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC 27599 USA
| | - Jeffrey A Bailey
- Department of Pathology and Laboratory Medicine, Brown University, Providence, RI, 02912 USA
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5
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Fogang B, Lellouche L, Ceesay S, Drammeh S, Jaiteh FK, Guery MA, Landier J, Haanappel CP, Froberg J, Conway D, D'Alessandro U, Bousema T, Claessens A. Asymptomatic Plasmodium falciparum carriage at the end of the dry season is associated with subsequent infection and clinical malaria in Eastern Gambia. Malar J 2024; 23:22. [PMID: 38229097 DOI: 10.1186/s12936-024-04836-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Accepted: 01/03/2024] [Indexed: 01/18/2024] Open
Abstract
BACKGROUND Chronic carriage of asymptomatic low-density Plasmodium falciparum parasitaemia in the dry season may support maintenance of acquired immunity that protects against clinical malaria. However, the relationship between chronic low-density infections and subsequent risk of clinical malaria episodes remains unclear. METHODS In a 2-years study (December 2014 to December 2016) in eastern Gambia, nine cross-sectional surveys using molecular parasite detection were performed in the dry and wet season. During the 2016 malaria transmission season, passive case detection identified episodes of clinical malaria. RESULTS Among the 5256 samples collected, 444 (8.4%) were positive for P. falciparum. A multivariate model identified village of residence, male sex, age ≥ 5 years old, anaemia, and fever as independent factors associated with P. falciparum parasite carriage. Infections did not cluster over time within the same households or recurred among neighbouring households. Asymptomatic parasite carriage at the end of dry season was associated with a higher risk of infection (Hazard Ratio, HR = 3.0, p < 0.0001) and clinical malaria (HR = 1.561, p = 0.057) during the following transmission season. Age and village of residence were additional predictors of infection and clinical malaria during the transmission season. CONCLUSION Chronic parasite carriage during the dry season is associated with an increased risk of malaria infection and clinical malaria. It is unclear whether this is due to environmental exposure or to other factors.
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Affiliation(s)
- Balotin Fogang
- LPHI, MIVEGEC, CNRS, INSERM, University of Montpellier, Montpellier, France
| | - Lionel Lellouche
- LPHI, MIVEGEC, CNRS, INSERM, University of Montpellier, Montpellier, France
| | - Sukai Ceesay
- Medical Research Council Unit The Gambia at the London School of Hygiene and Tropical Medicine, Banjul, The Gambia
| | - Sainabou Drammeh
- Medical Research Council Unit The Gambia at the London School of Hygiene and Tropical Medicine, Banjul, The Gambia
| | - Fatou K Jaiteh
- Medical Research Council Unit The Gambia at the London School of Hygiene and Tropical Medicine, Banjul, The Gambia
| | - Marc-Antoine Guery
- LPHI, MIVEGEC, CNRS, INSERM, University of Montpellier, Montpellier, France
| | - Jordi Landier
- IRD, INSERM, SESSTIM, ISSPAM, Aix Marseille University, 27 Boulevard Jean Moulin, 13005, Marseille, France
| | - Cynthia P Haanappel
- Department of Medical Microbiology, Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Janeri Froberg
- Department of Medical Microbiology, Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - David Conway
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, UK
| | - Umberto D'Alessandro
- Medical Research Council Unit The Gambia at the London School of Hygiene and Tropical Medicine, Banjul, The Gambia
| | - Teun Bousema
- Department of Medical Microbiology, Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Antoine Claessens
- LPHI, MIVEGEC, CNRS, INSERM, University of Montpellier, Montpellier, France.
- Medical Research Council Unit The Gambia at the London School of Hygiene and Tropical Medicine, Banjul, The Gambia.
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6
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Andolina C, Ramjith J, Rek J, Lanke K, Okoth J, Grignard L, Arinaitwe E, Briggs J, Bailey J, Aydemir O, Kamya MR, Greenhouse B, Dorsey G, Staedke SG, Drakeley C, Jonker M, Bousema T. Plasmodium falciparum gametocyte carriage in longitudinally monitored incident infections is associated with duration of infection and human host factors. Sci Rep 2023; 13:7072. [PMID: 37127688 PMCID: PMC10150352 DOI: 10.1038/s41598-023-33657-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Accepted: 04/17/2023] [Indexed: 05/03/2023] Open
Abstract
Malaria transmission depends on the presence of Plasmodium gametocytes that are the only parasite life stage that can infect mosquitoes. Gametocyte production varies between infections and over the course of infections. Infection duration is highly important for gametocyte production but poorly quantified. Between 2017 and 2019 an all-age cohort of individuals from Tororo, eastern Uganda was followed by continuous passive and routine assessments. We longitudinally monitored 104 incident infections from 98 individuals who were sampled once every 28 days and on any day of symptoms. Among infections that lasted ≥ 3 months, gametocyte appearance was near-universal with 96% of infections having detectable gametocytes prior to clearance. However, most infections were of much shorter duration; 55.7% of asymptomatic infections were detected only once. When considering all asymptomatic infections, regardless of their duration, only 36.3% had detectable gametocytes on at least one time-point prior to parasite clearance. Infections in individuals with sickle-cell trait (HbAS) were more likely to have gametocytes detected (Hazard Rate (HR) = 2.68, 95% CI 1.12, 6.38; p = 0.0231) and had gametocytes detected at higher densities (Density Ratio (DR) = 9.19, 95% CI 2.79, 30.23; p = 0.0002) compared to infections in wildtype (HbAA) individuals. Our findings suggest that a large proportion of incident infections is too short in duration and of too low density to contribute to onward transmission.
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Affiliation(s)
- Chiara Andolina
- Department of Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Jordache Ramjith
- Department of Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
- Department for Health Evidence, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - John Rek
- Infectious Diseases Research Collaboration, Kampala, Uganda
| | - Kjerstin Lanke
- Department of Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Joseph Okoth
- Infectious Diseases Research Collaboration, Kampala, Uganda
| | - Lynn Grignard
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, UK
| | | | - Jessica Briggs
- Department of Medicine, San Francisco General Hospital, University of California, San Francisco, USA
| | - Jeffrey Bailey
- Department of Pathology and Laboratory Medicine, Brown University, Providence, RI, USA
| | - Ozkan Aydemir
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA, USA
| | - Moses R Kamya
- Infectious Diseases Research Collaboration, Kampala, Uganda
- Department of Medicine, Makerere University College of Health Sciences, Kampala, Uganda
| | - Bryan Greenhouse
- Department of Medicine, San Francisco General Hospital, University of California, San Francisco, USA
| | - Grant Dorsey
- Department of Medicine, San Francisco General Hospital, University of California, San Francisco, USA
| | - Sarah G Staedke
- Department of Clinical Research, London School of Hygiene and Tropical Medicine, London, UK
| | - Chris Drakeley
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, UK
| | - Marianne Jonker
- Department for Health Evidence, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - Teun Bousema
- Department of Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, UK.
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7
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Ahmad A, Mohammed NI, Joof F, Affara M, Jawara M, Abubakar I, Okebe J, Ceesay S, Hamid-Adiamoh M, Bradley J, Amambua-Ngwa A, Nwakanma D, D'Alessandro U. Asymptomatic Plasmodium falciparum carriage and clinical disease: a 5-year community-based longitudinal study in The Gambia. Malar J 2023; 22:82. [PMID: 36882754 PMCID: PMC9993664 DOI: 10.1186/s12936-023-04519-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Accepted: 02/28/2023] [Indexed: 03/09/2023] Open
Abstract
BACKGROUND Carriers of persistent asymptomatic Plasmodium falciparum infections constitute an infectious reservoir that maintains malaria transmission. Understanding the extent of carriage and characteristics of carriers specific to endemic areas could guide use of interventions to reduce infectious reservoir. METHODS In eastern Gambia, an all-age cohort from four villages was followed up from 2012 to 2016. Each year, cross-sectional surveys were conducted at the end of the malaria transmission season (January) and just before the start of the next one (June) to determine asymptomatic P. falciparum carriage. Passive case detection was conducted during each transmission season (August to January) to determine incidence of clinical malaria. Association between carriage at the end of the season and at start of the next one and the risk factors for this were assessed. Effect of carriage before start of the season on risk of clinical malaria during the season was also examined. RESULTS A total of 1403 individuals-1154 from a semi-urban village and 249 from three rural villages were enrolled; median age was 12 years (interquartile range [IQR] 6, 30) and 12 years (IQR 7, 27) respectively. In adjusted analysis, asymptomatic P. falciparum carriage at the end of a transmission season and carriage just before start of the next one were strongly associated (adjusted odds ratio [aOR] = 19.99; 95% CI 12.57-31.77, p < 0.001). The odds of persistent carriage (i.e. infected both in January and in June) were higher in rural villages (aOR = 13.0; 95% CI 6.33-26.88, p < 0.001) and in children aged 5-15 years (aOR = 5.03; 95% CI 2.47-10.23, p = < 0.001). In the rural villages, carriage before start of the season was associated with a lower risk of clinical malaria during the season (incidence risk ratio [IRR] 0.48, 95% CI 0.27-0.81, p = 0.007). CONCLUSIONS Asymptomatic P. falciparum carriage at the end of a transmission season strongly predicted carriage just before start of the next one. Interventions that clear persistent asymptomatic infections when targeted at the subpopulation with high risk of carriage may reduce the infectious reservoir responsible for launching seasonal transmission.
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Affiliation(s)
- Abdullahi Ahmad
- Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, P.O Box 273, Banjul, The Gambia.
- Global Health Institute, University of Antwerp, Gouverneur Kinsbergencentrum, Campus Drie Eiken, Doornstraat 331, 2610, Wilrijk, Belgium.
| | - Nuredin Ibrahim Mohammed
- Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, P.O Box 273, Banjul, The Gambia
| | - Fatou Joof
- Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, P.O Box 273, Banjul, The Gambia
| | - Muna Affara
- Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, P.O Box 273, Banjul, The Gambia
| | - Musa Jawara
- Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, P.O Box 273, Banjul, The Gambia
| | - Ismaela Abubakar
- Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, P.O Box 273, Banjul, The Gambia
| | - Joseph Okebe
- International Public Health Department, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Serign Ceesay
- Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, P.O Box 273, Banjul, The Gambia
| | - Majidah Hamid-Adiamoh
- Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, P.O Box 273, Banjul, The Gambia
| | - John Bradley
- MRC International Statistics and Epidemiology Group, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK
| | - Alfred Amambua-Ngwa
- Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, P.O Box 273, Banjul, The Gambia
| | - Davis Nwakanma
- Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, P.O Box 273, Banjul, The Gambia.
| | - Umberto D'Alessandro
- Medical Research Council Unit The Gambia at London School of Hygiene and Tropical Medicine, P.O Box 273, Banjul, The Gambia
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8
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Neal A, Sassi J, Vardo-Zalik A. Drought correlates with reduced infection complexity and possibly prevalence in a decades-long study of the lizard malaria parasite Plasmodium mexicanum. PeerJ 2023; 11:e14908. [PMID: 36860770 PMCID: PMC9969858 DOI: 10.7717/peerj.14908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Accepted: 01/25/2023] [Indexed: 03/03/2023] Open
Abstract
Microparasites often exist as a collection of genetic 'clones' within a single host (termed multi-clonal, or complex, infections). Malaria parasites are no exception, with complex infections playing key roles in parasite ecology. Even so, we know little about what factors govern the distribution and abundance of complex infections in natural settings. Utilizing a natural dataset that spans more than 20 years, we examined the effects of drought conditions on infection complexity and prevalence in the lizard malaria parasite Plasmodium mexicanum and its vertebrate host, the western fence lizard, Sceloporus occidentalis. We analyzed data for 14,011 lizards sampled from ten sites over 34 years with an average infection rate of 16.2%. Infection complexity was assessed for 546 infected lizards sampled during the most recent 20 years. Our data illustrate significant, negative effects of drought-like conditions on infection complexity, with infection complexity expected to increase by a factor of 2.27 from the lowest to highest rainfall years. The relationship between rainfall and parasite prevalence is somewhat more ambiguous; when prevalence is modeled over the full range in years, a 50% increase in prevalence is predicted between the lowest and highest rainfall years, but this trend is not apparent or is reversed when data are analyzed over a shorter timeframe. To our knowledge, this is the first reported evidence for drought affecting the abundance of multi-clonal infections in malaria parasites. It is not yet clear what mechanism might connect drought with infection complexity, but the correlation we observed suggests that additional research on how drought influences parasite features like infection complexity, transmission rates and within-host competition may be worthwhile.
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Affiliation(s)
- Allison Neal
- Norwich University, Northfield, VT, United States
| | - Joshua Sassi
- Norwich University, Northfield, VT, United States
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Zhang X, Deitsch KW. The mystery of persistent, asymptomatic Plasmodium falciparum infections. Curr Opin Microbiol 2022; 70:102231. [PMID: 36327690 PMCID: PMC10500611 DOI: 10.1016/j.mib.2022.102231] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 08/31/2022] [Accepted: 10/12/2022] [Indexed: 01/25/2023]
Abstract
Plasmodium falciparum causes millions of malaria infections and hundreds of thousands of deaths annually. These parasites avoid the adaptive immune response by systematically cycling through a limited repertoire of variant surface antigens after which the number of circulating parasites drops to extremely low levels, coinciding with a loss of symptoms and eventual clearance of the infection. However, in regions with extended dry seasons or in individuals who no longer reside in endemic areas, asymptomatic infections have been observed to persist for many months or years, potentially serving as reservoirs for transmission. Recent work suggests the possibility that parasites can assume a state in which no variant surface antigens are expressed, thus rendering them virtually invisible to the immune system and enabling them to persist at low levels indefinitely.
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Affiliation(s)
- Xu Zhang
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, NY, USA
| | - Kirk W Deitsch
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, NY, USA.
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10
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Genetic Diversity of Plasmodium falciparum and Distribution of Antimalarial Drug Resistance Mutations in Symptomatic and Asymptomatic Infections. Antimicrob Agents Chemother 2022; 66:e0018822. [DOI: 10.1128/aac.00188-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Malaria control relies on passive case detection, and this strategy fails detecting asymptomatic infections. In addition, infections in endemic areas harbor multiple parasite genotypes that could affect case management and malaria epidemiology.
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