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Mandai SS, Francis F, Challe DP, Seth MD, Madebe RA, Petro DA, Budodo R, Kisambale AJ, Chacha GA, Moshi R, Mbwambo RB, Pereus D, Bakari C, Aaron S, Mbwambo D, Lusasi A, Kajange S, Lazaro S, Kapologwe N, Mandara CI, Ishengoma DS. High prevalence and risk of malaria among asymptomatic individuals from villages with high prevalence of artemisinin partial resistance in Kyerwa district of Kagera region, north-western Tanzania. Malar J 2024; 23:197. [PMID: 38926854 PMCID: PMC11201325 DOI: 10.1186/s12936-024-05019-5] [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: 10/11/2023] [Accepted: 06/16/2024] [Indexed: 06/28/2024] Open
Abstract
BACKGROUND Although Tanzania adopted and has been implementing effective interventions to control and eventually eliminate malaria, the disease is still a leading public health problem, and the country experiences heterogeneous transmission. Recent studies reported the emergence of parasites with artemisinin partial resistance (ART-R) in Kagera region with high prevalence (> 10.0%) in two districts of Karagwe and Kyerwa. This study assessed the prevalence and predictors/risk of malaria infections among asymptomatic individuals living in a hyperendemic area where ART-R has emerged in Kyerwa District of Kagera region, north-western Tanzania. METHODS This was a community-based cross-sectional survey which was conducted in July and August 2023 and involved individuals aged ≥ 6 months from five villages in Kyerwa district. Demographic, anthropometric, clinical, parasitological, type of house inhabited and socio-economic status (SES) data were collected using electronic capture tools run on Open Data Kit (ODK) software. Predictors/risks of malaria infections were determined by univariate and multivariate logistic regression, and the results were presented as crude (cORs) and adjusted odds ratios (aORs), with 95% confidence intervals (CIs). RESULTS Overall, 4454 individuals were tested using rapid diagnostic tests (RDTs), and 1979 (44.4%) had positive results. The prevalence of malaria infections ranged from 14.4% to 68.5% and varied significantly among the villages (p < 0.001). The prevalence and odds of infections were significantly higher in males (aOR = 1.28, 95% CI 1.08 -1.51, p = 0.003), school children (aged 5-≤10 years (aOR = 3.88, 95% CI 3.07-4.91, p < 0.001) and 10-≤15 years (aOR = 4.06, 95% CI 3.22-5.13, p < 0.001)) and among individuals who were not using bed nets (aOR = 1.22, 95% CI 1.03-1.46, p = 0.024). The odds of malaria infections were also higher in individuals with lower SES (aOR = 1.42, 95% CI 1.17-1.72, p < 0.001), and living in houses without windows (aOR = 2.08, 95% CI 1.46-2.96, p < 0.001), partially open (aOR = 1.33, 95% CI 1.11-1.58, p = 0.002) or fully open windows (aOR = 1.30, 95%CI 1.05-1.61, p = 0.015). CONCLUSION The five villages had a high prevalence of malaria infections and heterogeneity at micro-geographic levels. Groups with higher odds of malaria infections included school children, males, and individuals with low SES, living in poorly constructed houses or non-bed net users. These are important baseline data from an area with high prevalence of parasites with ART-R and will be useful in planning interventions for these groups, and in future studies to monitor the trends and potential spread of such parasites, and in designing a response to ART-R.
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Affiliation(s)
- Salehe S Mandai
- National Institute for Medical Research, Dar es Salaam, Tanzania
| | - Filbert Francis
- National Institute for Medical Research, Tanga Research Centre, Tanga, Tanzania
| | - Daniel P Challe
- National Institute for Medical Research, Tanga Research Centre, Tanga, Tanzania
| | - Misago D Seth
- National Institute for Medical Research, Dar es Salaam, Tanzania
| | - Rashid A Madebe
- National Institute for Medical Research, Dar es Salaam, Tanzania
| | | | - Rule Budodo
- National Institute for Medical Research, Dar es Salaam, Tanzania
| | | | - Gervas A Chacha
- National Institute for Medical Research, Dar es Salaam, Tanzania
| | - Ramadhan Moshi
- National Institute for Medical Research, Dar es Salaam, Tanzania
| | - Ruth B Mbwambo
- National Institute for Medical Research, Dar es Salaam, Tanzania
| | - Dativa Pereus
- National Institute for Medical Research, Dar es Salaam, Tanzania
| | - Catherine Bakari
- National Institute for Medical Research, Dar es Salaam, Tanzania
| | | | | | | | - Stella Kajange
- President's Office, Regional Administration and Local Government, Dodoma, Tanzania
| | - Samuel Lazaro
- National Malaria Control Programme, Dodoma, Tanzania
| | - Ntuli Kapologwe
- Directorate of Preventive Services, Ministry of Health, Dodoma, Tanzania
| | - Celine I Mandara
- National Institute for Medical Research, Dar es Salaam, Tanzania
| | - Deus S Ishengoma
- National Institute for Medical Research, Dar es Salaam, Tanzania.
- Faculty of Pharmaceutical Sciences, Monash University, Melbourne, Australia.
- Harvard T.H Chan School of Public Health, Harvard University, Boston, MA, USA.
- Department of Biochemistry, Kampala International University in Tanzania, Dar es Salaam, Tanzania.
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Hailemeskel E, Tebeje SK, Ramjith J, Ashine T, Lanke K, Behaksra SW, Emiru T, Tsegaye T, Gashaw A, Kedir S, Chali W, Esayas E, Tafesse T, Abera H, Bulto MG, Shumie G, Petros B, Mamo H, Drakeley C, Gadisa E, Bousema T, Tadesse FG. Dynamics of asymptomatic Plasmodium falciparum and Plasmodium vivax infections and their infectiousness to mosquitoes in a low transmission setting of Ethiopia: a longitudinal observational study. Int J Infect Dis 2024; 143:107010. [PMID: 38490637 DOI: 10.1016/j.ijid.2024.107010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Revised: 03/11/2024] [Accepted: 03/11/2024] [Indexed: 03/17/2024] Open
Abstract
OBJECTIVE A 15-month longitudinal study was conducted to determine the duration and infectivity of asymptomatic qPCR-detected Plasmodium falciparum and Plasmodium vivax infections in Ethiopia. METHOD Total parasite and gametocyte kinetics were determined by molecular methods; infectivity to Anopheles arabiensis mosquitoes by repeated membrane feeding assays. Infectivity results were contrasted with passively recruited symptomatic malaria cases. RESULTS For P. falciparum and P. vivax infections detected at enrolment, median durations of infection were 37 days (95% confidence interval [CI], 15-93) and 60 days (95% CI, 18-213), respectively. P. falciparum and P. vivax parasite densities declined over the course of infections. From 47 feeding assays on 22 asymptomatic P. falciparum infections, 6.4% (3/47) were infectious and these infected 1.8% (29/1579) of mosquitoes. No transmission was observed in feeding assays on asymptomatic P. vivax mono-infections (0/56); one mixed-species infection was highly infectious. Among the symptomatic cases, 4.3% (2/47) of P. falciparum and 73.3% (53/86) of P. vivax patients were infectious to mosquitoes. CONCLUSION The majority of asymptomatic infections were of short duration and low parasite density. Only a minority of asymptomatic individuals were infectious to mosquitoes. This contrasts with earlier findings and is plausibly due to the low parasite densities in this population.
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Affiliation(s)
- Elifaged Hailemeskel
- Armauer Hansen Research Institute, Addis Ababa, Ethiopia; Department of Medical Microbiology and Radboud Center for Infectious Diseases, Radboud University Medical Center, Nijmegen, Netherlands; Department of Biology, College of Natural and Computational Sciences, Wollo university, Dessie, Ethiopia; Department of Microbial, Cellular and Molecular Biology, Addis Ababa University, Addis Ababa, Ethiopia
| | - Surafel K Tebeje
- Armauer Hansen Research Institute, Addis Ababa, Ethiopia; Department of Medical Microbiology and Radboud Center for Infectious Diseases, Radboud University Medical Center, Nijmegen, Netherlands
| | - Jordache Ramjith
- Department of Medical Microbiology and Radboud Center for Infectious Diseases, Radboud University Medical Center, Nijmegen, Netherlands
| | | | - Kjerstin Lanke
- Department of Medical Microbiology and Radboud Center for Infectious Diseases, Radboud University Medical Center, Nijmegen, Netherlands
| | | | - Tadele Emiru
- Armauer Hansen Research Institute, Addis Ababa, Ethiopia
| | - Tizita Tsegaye
- Armauer Hansen Research Institute, Addis Ababa, Ethiopia
| | - Abrham Gashaw
- Armauer Hansen Research Institute, Addis Ababa, Ethiopia
| | - Soria Kedir
- Adama Regional Laboratory, Oromia Region Health Bureau, Adama, Ethiopia
| | - Wakweya Chali
- Armauer Hansen Research Institute, Addis Ababa, Ethiopia
| | | | | | - Haile Abera
- Armauer Hansen Research Institute, Addis Ababa, Ethiopia
| | | | - Girma Shumie
- Armauer Hansen Research Institute, Addis Ababa, Ethiopia
| | - Beyene Petros
- Department of Microbial, Cellular and Molecular Biology, Addis Ababa University, Addis Ababa, Ethiopia
| | - Hassen Mamo
- Department of Microbial, Cellular and Molecular Biology, Addis Ababa University, Addis Ababa, Ethiopia
| | - Chris Drakeley
- London School of Hygiene & Tropical Medicine, London, United Kingdom
| | | | - Teun Bousema
- Department of Medical Microbiology and Radboud Center for Infectious Diseases, Radboud University Medical Center, Nijmegen, Netherlands
| | - Fitsum G Tadesse
- Armauer Hansen Research Institute, Addis Ababa, Ethiopia; Department of Medical Microbiology and Radboud Center for Infectious Diseases, Radboud University Medical Center, Nijmegen, Netherlands; London School of Hygiene & Tropical Medicine, London, United Kingdom.
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3
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Fontoura PS, Macedo EG, Calil PR, Corder RM, Rodrigues PT, Tonini J, Esquivel FD, Ladeia WA, Fernandes ARJ, Johansen IC, Silva MF, Fernandes AOS, Ladeia-Andrade S, Castro MC, Ferreira MU. Changing Clinical Epidemiology of Plasmodium vivax Malaria as Transmission Decreases: Population-Based Prospective Panel Survey in the Brazilian Amazon. J Infect Dis 2024; 229:947-958. [PMID: 38324758 PMCID: PMC11011196 DOI: 10.1093/infdis/jiad456] [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: 06/03/2023] [Accepted: 10/16/2023] [Indexed: 02/09/2024] Open
Abstract
BACKGROUND Malarial infections are often missed by microscopy, and most parasite carriers are asymptomatic in low-endemicity settings. Whether parasite detectability and its ability to elicit symptoms change as transmission declines remains unclear. METHODS We performed a prospective panel survey with repeated measurements on the same participants over 12 months to investigate whether Plasmodium vivax detectability by microscopy and risk of symptoms upon infection varied during a community-wide larviciding intervention in the Amazon basin of Brazil that markedly reduced vector density. We screened 1096 to 1400 residents in the intervention site for malaria by microscopy and quantitative TaqMan assays at baseline and twice during intervention. RESULTS We found that more P vivax infections than expected from their parasite densities measured by TaqMan assays were missed by microscopy as transmission decreased. At lower transmission, study participants appeared to tolerate higher P vivax loads without developing symptoms. We hypothesize that changes in the ratio between circulating parasites and those that accumulate in the bone marrow and spleen, by avoiding peripheral blood microscopy detection, account for decreased parasite detectability and lower risk of symptoms under low transmission. CONCLUSIONS P vivax infections are more likely to be subpatent and remain asymptomatic as malaria transmission decreases.
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Affiliation(s)
- Pablo S Fontoura
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo
- Secretary of Health Surveillance, Ministry of Health, Brasília, Brazil
| | - Evelyn G Macedo
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo
| | - Priscila R Calil
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo
| | - Rodrigo M Corder
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo
- Divisions of Epidemiology and Biostatistics, Berkeley School of Public Health, University of California
| | - Priscila T Rodrigues
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo
| | - Juliana Tonini
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo
| | - Fabiana D Esquivel
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo
| | - Winni A Ladeia
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo
| | | | - Igor C Johansen
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo
| | - Marcos F Silva
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo
| | - Amanda O S Fernandes
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo
| | | | - Marcia C Castro
- Department of Global Health and Population, Harvard T. H. Chan School of Public Health, Boston, Massachusetts
| | - Marcelo U Ferreira
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo
- Global Health and Tropical Medicine, Institute of Hygiene and Tropical Medicine, Nova University of Lisbon, Portugal
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Jebiwott S, Gutapaka N, Sumari D, Loss G, Athuman T, Nyandele JP, Cummins H, Chemba M, Benjamin-Chung J, Gangar P, Wu X, Smith J, Chen I, Dorsey G, Fink G, Olotu A, Hsiang M. Child Health and Infection with Low Density (CHILD) malaria: a protocol for a randomised controlled trial to assess the long-term health and socioeconomic impacts of testing and treating low-density malaria infection among children in Tanzania. BMJ Open 2024; 14:e082227. [PMID: 38538037 PMCID: PMC10982758 DOI: 10.1136/bmjopen-2023-082227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Accepted: 02/15/2024] [Indexed: 04/04/2024] Open
Abstract
INTRODUCTION As malaria declines, low-density malaria infections (LMIs) represent an increasing proportion of infections and may have negative impacts on child health and cognition, necessitating development of targeted and effective solutions. This trial assesses the health, cognitive and socioeconomic impact of two strategies for detecting and treating LMI in a low transmission setting. METHODS AND ANALYSIS The study is a 3-arm open-label individually randomised controlled trial enrolling 600 children aged 6 months to 10 years in Bagamoyo district, Tanzania. Children are randomised to one of three arms: active case detection with molecular (ACDm) testing by high volume quantitative PCR (qPCR), passive case detection also with molecular testing (PCDm) and a control of standard PCD using rapid diagnostics tests (RDTs). Over the 2-year trial, ACDm participants receive malaria testing using RDT and qPCR three times annually, and malaria testing by RDT only when presenting with fever. PCDm and PCD participants receive malaria testing by RDT and qPCR or RDT only, respectively, when presenting with fever. RDT or qPCR positive participants with uncomplicated malaria are treated with artemether lumefantrine. The primary outcome is cumulative incidence of all-cause sick visits. Secondary outcomes include fever episodes, clinical failure after fever episodes, adverse events, malaria, non-malarial infection, antibiotic use, anaemia, growth faltering, cognition and attention, school outcomes, immune responses, and socioeconomic effects. Outcomes are assessed through monthly clinical assessments and testing, and baseline and endline neurodevelopmental testing. The trial is expected to provide key evidence and inform policy on health, cognitive and socioeconomic impact of interventions targeting LMI in children. ETHICS AND DISSEMINATION Study is approved by Tanzania NatHREC and institutional review boards at University of California San Francisco and Ifakara Health Institute. Findings will be reported on ClinicalTrials.gov, in peer-reviewed journals and through stakeholder meetings. TRIAL REGISTRATION NUMBER NCT05567016.
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Affiliation(s)
- Sylvia Jebiwott
- Malaria Elimination Initiative, Institute of Global Health Sciences, University of California, San Francisco, San Francisco, California, USA
| | | | - Deborah Sumari
- Ifakara Health Institute, Bagamoyo, Tanzania, United Republic of
| | - Georg Loss
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Thabit Athuman
- Ifakara Health Institute, Bagamoyo, Tanzania, United Republic of
| | | | - Hannah Cummins
- Malaria Elimination Initiative, Institute of Global Health Sciences, University of California, San Francisco, San Francisco, California, USA
| | - Mwajuma Chemba
- Ifakara Health Institute, Bagamoyo, Tanzania, United Republic of
| | - Jade Benjamin-Chung
- Epidemiology and Population Health, Stanford University School of Medicine, Stanford, California, USA
- Chan Zuckerberg Biohub, San Francisco, California, USA
| | - Pamela Gangar
- Malaria Elimination Initiative, Institute of Global Health Sciences, University of California, San Francisco, San Francisco, California, USA
| | - Xue Wu
- Malaria Elimination Initiative, Institute of Global Health Sciences, University of California, San Francisco, San Francisco, California, USA
| | - Jennifer Smith
- Malaria Elimination Initiative, Institute of Global Health Sciences, University of California, San Francisco, San Francisco, California, USA
| | - Ingrid Chen
- Malaria Elimination Initiative, Institute of Global Health Sciences, University of California, San Francisco, San Francisco, California, USA
| | - Grant Dorsey
- Department of Medicine, University of California, San Francisco, San Francisco, California, USA
| | - Günther Fink
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Ally Olotu
- Ifakara Health Institute, Bagamoyo, Tanzania, United Republic of
| | - Michelle Hsiang
- Malaria Elimination Initiative, Institute of Global Health Sciences, University of California, San Francisco, San Francisco, California, USA
- Chan Zuckerberg Biohub, San Francisco, California, USA
- Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, California, USA
- Department of Pediatrics, University of California, San Francisco, San Francisco, California, USA
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5
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Andolina C, Graumans W, Guelbeogo M, van Gemert GJ, Ramijth J, Harouna S, Soumanaba Z, Stoter R, Vegte-Bolmer M, Pangos M, Sinnis P, Collins K, Staedke SG, Tiono AB, Drakeley C, Lanke K, Bousema T. Quantification of sporozoite expelling by Anopheles mosquitoes infected with laboratory and naturally circulating P. falciparum gametocytes. eLife 2024; 12:RP90989. [PMID: 38517746 PMCID: PMC10959522 DOI: 10.7554/elife.90989] [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: 03/24/2024] Open
Abstract
It is currently unknown whether all Plasmodium falciparum-infected mosquitoes are equally infectious. We assessed sporogonic development using cultured gametocytes in the Netherlands and naturally circulating strains in Burkina Faso. We quantified the number of sporozoites expelled into artificial skin in relation to intact oocysts, ruptured oocysts, and residual salivary gland sporozoites. In laboratory conditions, higher total sporozoite burden was associated with shorter duration of sporogony (p<0.001). Overall, 53% (116/216) of infected Anopheles stephensi mosquitoes expelled sporozoites into artificial skin with a median of 136 expelled sporozoites (interquartile range [IQR], 34-501). There was a strong positive correlation between ruptured oocyst number and salivary gland sporozoite load (ρ = 0.8; p<0.0001) and a weaker positive correlation between salivary gland sporozoite load and number of sporozoites expelled (ρ = 0.35; p=0.0002). In Burkina Faso, Anopheles coluzzii mosquitoes were infected by natural gametocyte carriers. Among salivary gland sporozoite positive mosquitoes, 89% (33/37) expelled sporozoites with a median of 1035 expelled sporozoites (IQR, 171-2969). Again, we observed a strong correlation between ruptured oocyst number and salivary gland sporozoite load (ρ = 0.9; p<0.0001) and a positive correlation between salivary gland sporozoite load and the number of sporozoites expelled (ρ = 0.7; p<0.0001). Several mosquitoes expelled multiple parasite clones during probing. Whilst sporozoite expelling was regularly observed from mosquitoes with low infection burdens, our findings indicate that mosquito infection burden is positively associated with the number of expelled sporozoites. Future work is required to determine the direct implications of these findings for transmission potential.
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Affiliation(s)
- Chiara Andolina
- Department of Medical Microbiology, Radboud University Nijmegen Medical CentreNijmegenNetherlands
| | - Wouter Graumans
- Department of Medical Microbiology, Radboud University Nijmegen Medical CentreNijmegenNetherlands
| | - Moussa Guelbeogo
- Centre National de Recherche et de Formation sur le PaludismeOuagadougouBurkina Faso
| | - Geert-Jan van Gemert
- Department of Medical Microbiology, Radboud University Nijmegen Medical CentreNijmegenNetherlands
| | - Jordache Ramijth
- Department of Medical Microbiology, Radboud University Nijmegen Medical CentreNijmegenNetherlands
| | - Soré Harouna
- Centre National de Recherche et de Formation sur le PaludismeOuagadougouBurkina Faso
| | - Zongo Soumanaba
- Centre National de Recherche et de Formation sur le PaludismeOuagadougouBurkina Faso
| | - Rianne Stoter
- Department of Medical Microbiology, Radboud University Nijmegen Medical CentreNijmegenNetherlands
| | - Marga Vegte-Bolmer
- Department of Medical Microbiology, Radboud University Nijmegen Medical CentreNijmegenNetherlands
| | - Martina Pangos
- Department of Plastic and Reconstructive Surgery, Azienda Ospedaliero Universitaria GiulianoIsontina TriesteTriesteItaly
| | - Photini Sinnis
- Department of Molecular Microbiology and Immunology, Johns HopkinsBloomberg School of Public HealthBaltimoreUnited States
| | - Katharine Collins
- Department of Medical Microbiology, Radboud University Nijmegen Medical CentreNijmegenNetherlands
| | - Sarah G Staedke
- Liverpool School of Tropical MedicineLiverpoolUnited Kingdom
| | - Alfred B Tiono
- Centre National de Recherche et de Formation sur le PaludismeOuagadougouBurkina Faso
| | - Chris Drakeley
- Department of Immunology and Infection, London School of Hygiene and Tropical MedicineLondonUnited Kingdom
| | - Kjerstin Lanke
- Department of Medical Microbiology, Radboud University Nijmegen Medical CentreNijmegenNetherlands
| | - Teun Bousema
- Department of Medical Microbiology, Radboud University Nijmegen Medical CentreNijmegenNetherlands
- Department of Immunology and Infection, London School of Hygiene and Tropical MedicineLondonUnited Kingdom
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6
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Emery JC, Dodd PJ, Banu S, Frascella B, Garden FL, Horton KC, Hossain S, Law I, van Leth F, Marks GB, Nguyen HB, Nguyen HV, Onozaki I, Quelapio MID, Richards AS, Shaikh N, Tiemersma EW, White RG, Zaman K, Cobelens F, Houben RMGJ. Estimating the contribution of subclinical tuberculosis disease to transmission: An individual patient data analysis from prevalence surveys. eLife 2023; 12:e82469. [PMID: 38109277 PMCID: PMC10727500 DOI: 10.7554/elife.82469] [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: 08/04/2022] [Accepted: 08/04/2023] [Indexed: 12/20/2023] Open
Abstract
Background Individuals with bacteriologically confirmed pulmonary tuberculosis (TB) disease who do not report symptoms (subclinical TB) represent around half of all prevalent cases of TB, yet their contribution to Mycobacterium tuberculosis (Mtb) transmission is unknown, especially compared to individuals who report symptoms at the time of diagnosis (clinical TB). Relative infectiousness can be approximated by cumulative infections in household contacts, but such data are rare. Methods We reviewed the literature to identify studies where surveys of Mtb infection were linked to population surveys of TB disease. We collated individual-level data on representative populations for analysis and used literature on the relative durations of subclinical and clinical TB to estimate relative infectiousness through a cumulative hazard model, accounting for sputum-smear status. Relative prevalence of subclinical and clinical disease in high-burden settings was used to estimate the contribution of subclinical TB to global Mtb transmission. Results We collated data on 414 index cases and 789 household contacts from three prevalence surveys (Bangladesh, the Philippines, and Viet Nam) and one case-finding trial in Viet Nam. The odds ratio for infection in a household with a clinical versus subclinical index case (irrespective of sputum smear status) was 1.2 (0.6-2.3, 95% confidence interval). Adjusting for duration of disease, we found a per-unit-time infectiousness of subclinical TB relative to clinical TB of 1.93 (0.62-6.18, 95% prediction interval [PrI]). Fourteen countries across Asia and Africa provided data on relative prevalence of subclinical and clinical TB, suggesting an estimated 68% (27-92%, 95% PrI) of global transmission is from subclinical TB. Conclusions Our results suggest that subclinical TB contributes substantially to transmission and needs to be diagnosed and treated for effective progress towards TB elimination. Funding JCE, KCH, ASR, NS, and RH have received funding from the European Research Council (ERC) under the Horizon 2020 research and innovation programme (ERC Starting Grant No. 757699) KCH is also supported by UK FCDO (Leaving no-one behind: transforming gendered pathways to health for TB). This research has been partially funded by UK aid from the UK government (to KCH); however, the views expressed do not necessarily reflect the UK government's official policies. PJD was supported by a fellowship from the UK Medical Research Council (MR/P022081/1); this UK-funded award is part of the EDCTP2 programme supported by the European Union. RGW is funded by the Wellcome Trust (218261/Z/19/Z), NIH (1R01AI147321-01), EDTCP (RIA208D-2505B), UK MRC (CCF17-7779 via SET Bloomsbury), ESRC (ES/P008011/1), BMGF (OPP1084276, OPP1135288 and INV-001754), and the WHO (2020/985800-0).
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Affiliation(s)
- Jon C Emery
- TB Modelling Group, TB Centre and Centre for Mathematical Modelling of Infectious Diseases, Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical MedicineLondonUnited Kingdom
| | - Peter J Dodd
- School of Health and Related Research, University of SheffieldSheffieldUnited Kingdom
| | - Sayera Banu
- International Centre for Diarrhoeal Disease ResearchDhakaBangladesh
| | | | - Frances L Garden
- South West Sydney Clinical Campuses, University of New South WalesSydneyAustralia
- Ingham Institute of Applied Medical ResearchSydneyAustralia
| | - Katherine C Horton
- TB Modelling Group, TB Centre and Centre for Mathematical Modelling of Infectious Diseases, Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical MedicineLondonUnited Kingdom
| | - Shahed Hossain
- James P. Grant School of Public Health, BRAC UniversityDhakaBangladesh
| | - Irwin Law
- Global Tuberculosis Programme, World Health OrganizationGenevaSwitzerland
| | - Frank van Leth
- Department of Health Sciences, VU UniversityAmsterdamNetherlands
- Amsterdam Public Health Research InstituteAmsterdamNetherlands
| | - Guy B Marks
- South West Sydney Clinical Campuses, University of New South WalesSydneyAustralia
- Woolcock Institute of Medical ResearchSydneyAustralia
| | - Hoa Binh Nguyen
- National Lung Hospital, National Tuberculosis Control ProgramHa NoiViet Nam
| | - Hai Viet Nguyen
- National Lung Hospital, National Tuberculosis Control ProgramHa NoiViet Nam
| | - Ikushi Onozaki
- Research Institute of Tuberculosis, Japan Anti-Tuberculosis AssociationTokyoJapan
| | | | - Alexandra S Richards
- TB Modelling Group, TB Centre and Centre for Mathematical Modelling of Infectious Diseases, Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical MedicineLondonUnited Kingdom
| | - Nabila Shaikh
- TB Modelling Group, TB Centre and Centre for Mathematical Modelling of Infectious Diseases, Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical MedicineLondonUnited Kingdom
- Sanofi PasteurReadingUnited Kingdom
| | | | - Richard G White
- TB Modelling Group, TB Centre and Centre for Mathematical Modelling of Infectious Diseases, Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical MedicineLondonUnited Kingdom
| | - Khalequ Zaman
- International Centre for Diarrhoeal Disease ResearchDhakaBangladesh
| | - Frank Cobelens
- Department of Global Health and Amsterdam Institute for Global Health and Development, Amsterdam University Medical Centers, University of AmsterdamAmsterdamNetherlands
| | - Rein MGJ Houben
- TB Modelling Group, TB Centre and Centre for Mathematical Modelling of Infectious Diseases, Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical MedicineLondonUnited Kingdom
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7
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Walker IS, Rogerson SJ. Pathogenicity and virulence of malaria: Sticky problems and tricky solutions. Virulence 2023; 14:2150456. [PMID: 36419237 PMCID: PMC9815252 DOI: 10.1080/21505594.2022.2150456] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2022] [Revised: 10/18/2022] [Accepted: 10/19/2022] [Indexed: 11/25/2022] Open
Abstract
Infections with Plasmodium falciparum and Plasmodium vivax cause over 600,000 deaths each year, concentrated in Africa and in young children, but much of the world's population remain at risk of infection. In this article, we review the latest developments in the immunogenicity and pathogenesis of malaria, with a particular focus on P. falciparum, the leading malaria killer. Pathogenic factors include parasite-derived toxins and variant surface antigens on infected erythrocytes that mediate sequestration in the deep vasculature. Host response to parasite toxins and to variant antigens is an important determinant of disease severity. Understanding how parasites sequester, and how antibody to variant antigens could prevent sequestration, may lead to new approaches to treat and prevent disease. Difficulties in malaria diagnosis, drug resistance, and specific challenges of treating P. vivax pose challenges to malaria elimination, but vaccines and other preventive strategies may offer improved disease control.
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Affiliation(s)
- Isobel S Walker
- Department of Infectious Diseases, The University of Melbourne, The Doherty Institute, Melbourne, Australia
| | - Stephen J Rogerson
- Department of Infectious Diseases, The University of Melbourne, The Doherty Institute, Melbourne, Australia
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8
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de Roos AM, He Q, Pascual M. An immune memory-structured SIS epidemiological model for hyperdiverse pathogens. Proc Natl Acad Sci U S A 2023; 120:e2218499120. [PMID: 37910552 PMCID: PMC10636369 DOI: 10.1073/pnas.2218499120] [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: 10/28/2022] [Accepted: 10/02/2023] [Indexed: 11/03/2023] Open
Abstract
A hyperdiverse class of pathogens of humans and wildlife, including the malaria parasite Plasmodium falciparum, relies on multigene families to encode antigenic variation. As a result, high (asymptomatic) prevalence is observed despite high immunity in local populations under high-transmission settings. The vast diversity of "strains" and genes encoding this variation challenges the application of established models for the population dynamics of such infectious diseases. Agent-based models have been formulated to address theory on strain coexistence and structure, but their complexity can limit application to gain insights into population dynamics. Motivated by P. falciparum malaria, we develop an alternative formulation in the form of a structured susceptible-infected-susceptible population model in continuous time, where individuals are classified not only by age, as is standard, but also by the diversity of parasites they have been exposed to and retain in their specific immune memory. We analyze the population dynamics and bifurcation structure of this system of partial-differential equations, showing the existence of alternative steady states and an associated tipping point with transmission intensity. We attribute the critical transition to the positive feedback between parasite genetic diversity and force of infection. Basins of attraction show that intervention must drastically reduce diversity to prevent a rebound to high infection levels. Results emphasize the importance of explicitly considering pathogen diversity and associated specific immune memory in the population dynamics of hyperdiverse epidemiological systems. This statement is discussed in a more general context for ecological competition systems with hyperdiverse trait spaces.
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Affiliation(s)
- André M. de Roos
- Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam1090 GE, The Netherlands
- Santa Fe Institute, Santa Fe, NM87501
| | - Qixin He
- Department of Biological Sciences, Purdue University, West Lafayette, IN47907
| | - Mercedes Pascual
- Santa Fe Institute, Santa Fe, NM87501
- Department of Ecology and Evolution, The University of Chicago, Chicago, IL60637
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9
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Gelband H, Carshon-Marsh R, Ansumana R, Swaray IB, Pandey A, Aimone A, Bogoch I, Eikelboom J, Jha P. Could vaccinating adults against malaria materially reduce adult mortality in high-transmission areas? Malar J 2023; 22:278. [PMID: 37726804 PMCID: PMC10507840 DOI: 10.1186/s12936-023-04714-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Accepted: 09/12/2023] [Indexed: 09/21/2023] Open
Abstract
After a period of unprecedented progress against malaria in the 2000s, halving the global disease burden by 2015, gains overall in sub-Saharan Africa have slowed and even reversed in some places, beginning well before the COVID-19 pandemic. The highly effective drugs, treated nets, and diagnostics that fueled the initial progress all face some threats to their effectiveness, and global funding to maintain and increase their use over the long term is not guaranteed. Malaria vaccines are among the most promising new interventions that could accelerate the elimination of malaria. Vaccines are still in early stages of rollout in children, the age group (along with pregnant women) that has been the focus of malaria strategies for a century. At the same time, over the past decade, a case has been made, based largely on evidence from verbal autopsies in at least a few high-transmission areas, that the malaria death rate among adults has been greatly underestimated. Could vaccinating adults help to bring down the adult malaria mortality rate, contribute to reduced transmission, or both? A randomized trial of a malaria vaccine is proposed in Sierra Leone, a highly endemic setting, to shed light on this proposition.
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Affiliation(s)
- Hellen Gelband
- Centre for Global Health Research, Unity Health Toronto, University of Toronto, Toronto, Canada.
- Dalla Lana School of Public Health, University of Toronto, Toronto, Canada.
| | | | - Rashid Ansumana
- School of Community Health Sciences, Njala University, Bo, Sierra Leone
| | - Ibrahim Bob Swaray
- Centre for Global Health Research, Unity Health Toronto, University of Toronto, Toronto, Canada
| | - Arjun Pandey
- Department of Medicine, Temerty Faculty of Medicine, University of Toronto, Toronto, Canada
| | - Ashley Aimone
- Centre for Global Health Research, Unity Health Toronto, University of Toronto, Toronto, Canada
- Dalla Lana School of Public Health, University of Toronto, Toronto, Canada
| | - Isaac Bogoch
- Divisions of General Internal Medicine and Infectious Diseases, Toronto General Hospital, University Health Network, Toronto, Canada
- Department of Medicine, University of Toronto, Toronto, Canada
| | - John Eikelboom
- Population Health Research Institute, Hamilton Health Sciences, McMaster University, Hamilton, ON, Canada
| | - Prabhat Jha
- Centre for Global Health Research, Unity Health Toronto, University of Toronto, Toronto, Canada
- Dalla Lana School of Public Health, University of Toronto, Toronto, Canada
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10
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Fakih BS, Holzschuh A, Ross A, Stuck L, Abdul R, Al-Mafazy AWH, Irema I, Mbena A, Thawer SG, Shija SJ, Aliy SM, Ali A, Fink G, Yukich J, Hetzel MW. Risk of imported malaria infections in Zanzibar: a cross-sectional study. Infect Dis Poverty 2023; 12:80. [PMID: 37641152 PMCID: PMC10464242 DOI: 10.1186/s40249-023-01129-5] [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: 04/11/2023] [Accepted: 08/11/2023] [Indexed: 08/31/2023] Open
Abstract
BACKGROUND Zanzibar has made substantial progress in malaria control with vector control, improved diagnosis, and artemisinin-based combination therapy. Parasite prevalence in the population has remained around 1% but imported infections from mainland Tanzania contribute to sustained local transmission. Understanding travel patterns between mainland Tanzania and Zanzibar, and the risk of malaria infection, may help to control malaria importation to Zanzibar. METHODS A rolling cross-sectional survey linked to routine reactive case detection of malaria was carried out in Zanzibar between May 2017 and October 2018. Households of patients diagnosed with malaria at health facilities were surveyed and household members were tested for malaria using rapid diagnostic tests and a sub-sample by quantitative PCR (qPCR). Interviews elicited a detailed travel history of all household members who had travelled within the past two months, including trips within and outside of Zanzibar. We estimated the association of malaria infection with travel destinations in pre-defined malaria endemicity categories, trip duration, and other co-variates using logistic regression. RESULTS Of 17,891 survey participants, 1177 (7%) reported a recent trip, of which 769 (65%) visited mainland Tanzania. Among travellers to mainland Tanzania with travel destination details and a qPCR result available, 241/378 (64%) reported traveling to districts with a 'high' malaria endemicity and for 12% the highest endemicity category was 'moderate'. Travelers to the mainland were more likely to be infected with malaria parasites (29%, 108/378) than those traveling within Zanzibar (8%, 16/206) or to other countries (6%, 2/17). Among travellers to mainland Tanzania, those visiting highly endemic districts had a higher odds of being qPCR-positive than those who travelled only to districts where malaria-endemicity was classified as low or very low (adjusted odd ratio = 7.0, 95% confidence interval: 1.9-25.5). Among travellers to the mainland, 110/378 (29%) never or only sometimes used a mosquito net during their travel. CONCLUSIONS Strategies to reduce malaria importation to Zanzibar may benefit from identifying population groups traveling to highly endemic areas in mainland Tanzania. Targeted interventions to prevent and clear infections in these groups may be more feasible than attempting to screen and treat all travellers upon arrival in Zanzibar.
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Affiliation(s)
- Bakar S Fakih
- Ifakara Health Institute, Dar es Salaam, Tanzania.
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland.
- University of Basel, Basel, Switzerland.
| | - Aurel Holzschuh
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland
- Department of Biological Sciences, Eck Institute for Global Health, University of Notre Dame, Notre Dame, USA
| | - Amanda Ross
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland
- University of Basel, Basel, Switzerland
| | - Logan Stuck
- Tulane University School of Public Health and Tropical Medicine, New Orleans, LA, USA
- Amsterdam Institute for Global Health and Development, Amsterdam, Netherlands
| | - Ramadhan Abdul
- Ifakara Health Institute, Dar es Salaam, Tanzania
- Amsterdam Institute for Global Health and Development, Amsterdam, Netherlands
| | | | - Imani Irema
- Ifakara Health Institute, Dar es Salaam, Tanzania
| | | | - Sumaiyya G Thawer
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland
- University of Basel, Basel, Switzerland
| | - Shija J Shija
- Zanzibar Malaria Elimination Programme, Zanzibar, United Republic of Tanzania
| | - Safia M Aliy
- Zanzibar Malaria Elimination Programme, Zanzibar, United Republic of Tanzania
| | - Abdullah Ali
- Zanzibar Malaria Elimination Programme, Zanzibar, United Republic of Tanzania
| | - Günther Fink
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland
- University of Basel, Basel, Switzerland
| | - Joshua Yukich
- Tulane University School of Public Health and Tropical Medicine, New Orleans, LA, USA
| | - Manuel W Hetzel
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland
- University of Basel, Basel, Switzerland
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11
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Win Han Oo, Nguyen XT, Ngo TVA, Ngo DT, Win Htike, Aye Tun N, Kaung Myat Thu, Cutts J, Nguyen THP, May Chan Oo, Ei Phyu Htwe, Aung Khine Zaw, O'Flaherty K, Agius PA, Fowkes FJI. Performance and feasibility of reactive surveillance and response strategies for malaria elimination in Vietnam: a mixed-methods study. Malar J 2023; 22:229. [PMID: 37545009 PMCID: PMC10405448 DOI: 10.1186/s12936-023-04660-w] [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: 02/13/2023] [Accepted: 07/27/2023] [Indexed: 08/08/2023] Open
Abstract
BACKGROUND To enhance malaria elimination, Vietnam adopted a Reactive Surveillance and Response (RASR) Strategy in which malaria case notification and investigation must be completed within 2 days followed by a focus investigation within 7 days. The nationwide performance of Vietnam's RASR strategy has yet to be evaluated. This study aims to evaluate the performance and feasibility of RASR in Vietnam, thereby providing recommendations for improved RASR. METHODS To assess malaria RASR in Vietnam, a mixed-methods study of (1) secondary data analysis of nationwide malaria case-based dataset from 2017 to 2021; (2) a quantitative survey, and (3) qualitative in-depth interviews and focus group discussions administered to central, provincial and district level stakeholders/staff and to the commune and community level front line health services providers was conducted. RESULTS In Vietnam, there are guidelines and procedures for implementation of each step of RASR. The completeness of case notification on the reported monthly aggregated data was very high in both the paper-based (12,463/12,498, 99.7% in 2017-2020) and electronic reporting systems (467/467, 100% in 2021 when electronic reporting was introduced); however, there were delays in notification while using the paper-based system (timely notification-7,978/12,498, 63.8%). In 2021, the completeness (453/467, 97.0%) and timeliness (371/467, 79.4%) of case investigation were found to be high. Reactive case detection was the major focus investigation response, with fever screening achievement of 88.6% (11,481 / 12,965) and 88.5% (11,471 / 12,965) among index case and neighbouring household members, respectively. CONCLUSIONS Overall, there was policy commitment for implementation of RASR in Vietnam. The completeness and timeliness of case notification and case investigation were high and improved after the introduction of the electronic reporting system. More evidence is required for reactive case detection in defining the screening area or population.
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Affiliation(s)
- Win Han Oo
- Disease Elimination Programme, Burnet Institute, 85 Commercial Rd, Melbourne, VIC, Australia.
- Health Security Programme, Burnet Institute Myanmar, 226 U Wisara Road, Yangon, Myanmar.
| | - Xuan Thang Nguyen
- Department of Epidemiology, National Institute of Malariology, Parasitology and Entomology, Hanoi, Vietnam
| | | | - Duc Thang Ngo
- Department of Epidemiology, National Institute of Malariology, Parasitology and Entomology, Hanoi, Vietnam
| | - Win Htike
- Health Security Programme, Burnet Institute Myanmar, 226 U Wisara Road, Yangon, Myanmar
| | - Nilar Aye Tun
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, University of Melbourne, Melbourne, VIC, Australia
| | - Kaung Myat Thu
- Health Security Programme, Burnet Institute Myanmar, 226 U Wisara Road, Yangon, Myanmar
| | - Julia Cutts
- Disease Elimination Programme, Burnet Institute, 85 Commercial Rd, Melbourne, VIC, Australia
| | - T Hong Phuc Nguyen
- Department of Epidemiology, National Institute of Malariology, Parasitology and Entomology, Hanoi, Vietnam
| | - May Chan Oo
- Health Security Programme, Burnet Institute Myanmar, 226 U Wisara Road, Yangon, Myanmar
| | - Ei Phyu Htwe
- Health Security Programme, Burnet Institute Myanmar, 226 U Wisara Road, Yangon, Myanmar
| | - Aung Khine Zaw
- Health Security Programme, Burnet Institute Myanmar, 226 U Wisara Road, Yangon, Myanmar
| | - Katherine O'Flaherty
- Disease Elimination Programme, Burnet Institute, 85 Commercial Rd, Melbourne, VIC, Australia
| | - Paul A Agius
- Disease Elimination Programme, Burnet Institute, 85 Commercial Rd, Melbourne, VIC, Australia
- Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, VIC, Australia
| | - Freya J I Fowkes
- Disease Elimination Programme, Burnet Institute, 85 Commercial Rd, Melbourne, VIC, Australia
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, University of Melbourne, Melbourne, VIC, Australia
- Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, VIC, Australia
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12
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Hofer LM, Kweyamba PA, Sayi RM, Chabo MS, Maitra SL, Moore SJ, Tambwe MM. Malaria rapid diagnostic tests reliably detect asymptomatic Plasmodium falciparum infections in school-aged children that are infectious to mosquitoes. Parasit Vectors 2023; 16:217. [PMID: 37391770 DOI: 10.1186/s13071-023-05761-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Accepted: 03/29/2023] [Indexed: 07/02/2023] Open
Abstract
BACKGROUND Asymptomatic malaria infections (Plasmodium falciparum) are common in school-aged children and represent a disease transmission reservoir as they are potentially infectious to mosquitoes. To detect and treat such infections, convenient, rapid and reliable diagnostic tools are needed. In this study, malaria rapid diagnostic tests (mRDT), light microscopy (LM) and quantitative polymerase chain reaction (qPCR) were used to evaluate their performance detecting asymptomatic malaria infections that are infectious to mosquitoes. METHODS One hundred seventy asymptomatic school-aged children (6-14 years old) from the Bagamoyo district in Tanzania were screened for Plasmodium spp. infections using mRDT (SD BIOLINE), LM and qPCR. In addition, gametocytes were detected using reverse transcription quantitative polymerase chain reaction (RT-qPCR) for all qPCR-positive children. Venous blood from all P. falciparum positive children was fed to female Anopheles gambiae sensu stricto mosquitoes via direct membrane feeding assays (DMFAs) after serum replacement. Mosquitoes were dissected for oocyst infections on day 8 post-infection. RESULTS The P. falciparum prevalence in study participants was 31.7% by qPCR, 18.2% by mRDT and 9.4% by LM. Approximately one-third (31.2%) of asymptomatic malaria infections were infectious to mosquitoes in DMFAs. In total, 297 infected mosquitoes were recorded after dissections, from which 94.9% (282/297) were derived from infections detected by mRDT and 5.1% (15/297) from subpatent mRDT infections. CONCLUSION The mRDT can be used reliably to detect children carrying gametocyte densities sufficient to infect high numbers of mosquitoes. Subpatent mRDT infections contributed marginally to the pool of oocyts-infected mosquitoes.
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Affiliation(s)
- Lorenz M Hofer
- Vector Biology Unit, Department of Epidemiology and Public Health, Swiss Tropical and Public Health, Institute, Kreuzstrasse 2, 4123, Allschwil, Basel, Switzerland
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, 74, Bagamoyo, Tanzania
| | - Prisca A Kweyamba
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, 74, Bagamoyo, Tanzania
| | - Rajabu M Sayi
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, 74, Bagamoyo, Tanzania
| | - Mohamed S Chabo
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, 74, Bagamoyo, Tanzania
| | - Sonali L Maitra
- Vector Biology Unit, Department of Epidemiology and Public Health, Swiss Tropical and Public Health, Institute, Kreuzstrasse 2, 4123, Allschwil, Basel, Switzerland
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, 74, Bagamoyo, Tanzania
| | - Sarah J Moore
- Vector Biology Unit, Department of Epidemiology and Public Health, Swiss Tropical and Public Health, Institute, Kreuzstrasse 2, 4123, Allschwil, Basel, Switzerland
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, 74, Bagamoyo, Tanzania
- The Nelson Mandela African Institution of Science and Technology (NM-AIST), 447, Tengeru, Arusha, Tanzania
| | - Mgeni M Tambwe
- Vector Control Product Testing Unit (VCPTU) Ifakara Health Institute, Environmental Health, and Ecological Sciences, 74, Bagamoyo, Tanzania.
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13
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Holzschuh A, Lerch A, Gerlovina I, Fakih BS, Al-Mafazy AWH, Reaves EJ, Ali A, Abbas F, Ali MH, Ali MA, Hetzel MW, Yukich J, Koepfli C. Multiplexed ddPCR-amplicon sequencing reveals isolated Plasmodium falciparum populations amenable to local elimination in Zanzibar, Tanzania. Nat Commun 2023; 14:3699. [PMID: 37349311 PMCID: PMC10287761 DOI: 10.1038/s41467-023-39417-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Accepted: 06/13/2023] [Indexed: 06/24/2023] Open
Abstract
Zanzibar has made significant progress toward malaria elimination, but recent stagnation requires novel approaches. We developed a highly multiplexed droplet digital PCR (ddPCR)-based amplicon sequencing method targeting 35 microhaplotypes and drug-resistance loci, and successfully sequenced 290 samples from five districts covering both main islands. Here, we elucidate fine-scale Plasmodium falciparum population structure and infer relatedness and connectivity of infections using an identity-by-descent (IBD) approach. Despite high genetic diversity, we observe pronounced fine-scale spatial and temporal parasite genetic structure. Clusters of near-clonal infections on Pemba indicate persistent local transmission with limited parasite importation, presenting an opportunity for local elimination efforts. Furthermore, we observe an admixed parasite population on Unguja and detect a substantial fraction (2.9%) of significantly related infection pairs between Zanzibar and the mainland, suggesting recent importation. Our study provides a high-resolution view of parasite genetic structure across the Zanzibar archipelago and provides actionable insights for prioritizing malaria elimination efforts.
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Affiliation(s)
- Aurel Holzschuh
- Department of Biological Sciences, Eck Institute for Global Health, University of Notre Dame, Indiana, IN, USA.
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland.
| | - Anita Lerch
- Department of Biological Sciences, Eck Institute for Global Health, University of Notre Dame, Indiana, IN, USA
| | - Inna Gerlovina
- EPPIcenter Research Program, Division of HIV, ID and Global Medicine, Department of Medicine, University of California, San Francisco, CA, USA
| | - Bakar S Fakih
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland
- University of Basel, Basel, Switzerland
- Ifakara Health Institute, Dar es Salaam, United Republic of Tanzania
| | | | - Erik J Reaves
- U.S. Centers for Disease Control and Prevention, President's Malaria Initiative, Dar es Salaam, United Republic of Tanzania
| | - Abdullah Ali
- Zanzibar Malaria Elimination Programme, Zanzibar, United Republic of Tanzania
| | - Faiza Abbas
- Zanzibar Malaria Elimination Programme, Zanzibar, United Republic of Tanzania
| | - Mohamed Haji Ali
- Zanzibar Malaria Elimination Programme, Zanzibar, United Republic of Tanzania
| | - Mohamed Ali Ali
- Zanzibar Malaria Elimination Programme, Zanzibar, United Republic of Tanzania
| | - Manuel W Hetzel
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland
- University of Basel, Basel, Switzerland
| | - Joshua Yukich
- School of Public Health and Tropical Medicine, Tulane University, New Orleans, LA, USA
| | - Cristian Koepfli
- Department of Biological Sciences, Eck Institute for Global Health, University of Notre Dame, Indiana, IN, USA.
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14
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Amaral LC, Salazar YEAR, de Alvarenga DAM, de Pina-Costa A, Nunes AJD, de Souza Junior JC, Gonçalves GHP, Hirano ZMB, Moreira SB, Pissinatti A, Daniel-Ribeiro CT, de Sousa TN, Alves de Brito CF. Detection of Plasmodium simium gametocytes in non-human primates from the Brazilian Atlantic Forest. Malar J 2023; 22:170. [PMID: 37268984 DOI: 10.1186/s12936-023-04601-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Accepted: 05/20/2023] [Indexed: 06/04/2023] Open
Abstract
BACKGROUND Plasmodium species of non-human primates (NHP) are of great interest because they can naturally infect humans. Plasmodium simium, a parasite restricted to the Brazilian Atlantic Forest, was recently shown to cause a zoonotic outbreak in the state of Rio de Janeiro. The potential of NHP to act as reservoirs of Plasmodium infection presents a challenge for malaria elimination, as NHP will contribute to the persistence of the parasite. The aim of the current study was to identify and quantify gametocytes in NHP naturally-infected by P. simium. METHODS Whole blood samples from 35 NHP were used in quantitative reverse transcription PCR (RT-qPCR) assays targeting 18S rRNA, Pss25 and Pss48/45 malaria parasite transcripts. Absolute quantification was performed in positive samples for 18S rRNA and Pss25 targets. Linear regression was used to compare the quantification cycle (Cq) and the Spearman's rank correlation coefficient was used to assess the correlation between the copy numbers of 18S rRNA and Pss25 transcripts. The number of gametocytes/µL was calculated by applying a conversion factor of 4.17 Pss25 transcript copies per gametocyte. RESULTS Overall, 87.5% of the 26 samples, previously diagnosed as P. simium, were positive for 18S rRNA transcript amplification, of which 13 samples (62%) were positive for Pss25 transcript amplification and 7 samples (54%) were also positive for Pss48/45 transcript. A strong positive correlation was identified between the Cq of the 18S rRNA and Pss25 and between the Pss25 and Pss48/45 transcripts. The 18S rRNA and Pss25 transcripts had an average of 1665.88 and 3.07 copies/µL, respectively. A positive correlation was observed between the copy number of Pss25 and 18S rRNA transcripts. Almost all gametocyte carriers exhibited low numbers of gametocytes (< 1/µL), with only one howler monkey having 5.8 gametocytes/µL. CONCLUSIONS For the first time, a molecular detection of P. simium gametocytes in the blood of naturally-infected brown howler monkeys (Alouatta guariba clamitans) was reported here, providing evidence that they are likely to be infectious and transmit P. simium infection, and, therefore, may act as a reservoir of malaria infection for humans in the Brazilian Atlantic Forest.
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Affiliation(s)
- Lara Cotta Amaral
- Grupo de Pesquisa em Biologia Molecular e Imunologia da Malária, Instituto René Rachou, Fundação Oswaldo Cruz (Fiocruz), Belo Horizonte, Brazil
| | | | - Denise Anete Madureira de Alvarenga
- Grupo de Pesquisa em Biologia Molecular e Imunologia da Malária, Instituto René Rachou, Fundação Oswaldo Cruz (Fiocruz), Belo Horizonte, Brazil
| | - Anielle de Pina-Costa
- Laboratório de Doenças Febris Agudas, Instituto Nacional de Infectologia Evandro Chagas, Fiocruz, Rio de Janeiro, Brazil
- Centro de Pesquisa, Diagnóstico e Treinamento em Malária, Fiocruz, Rio de Janeiro, Brazil
- Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil
- Departamento de Doenças Infecciosas e Parasitárias, Escola de Enfermagem Aurora de Afonso Costa, Universidade Federal Fluminense, Niterói, Brazil
| | - Ana Júlia Dutra Nunes
- Programa de Conservação do Bugio Ruivo, Joinville, Brazil
- Centro de Pesquisas Biológicas de Indaial, Indaial, Brazil
- Universidade Regional de Blumenau - FURB, Blumenau, Brazil
| | - Júlio Cesar de Souza Junior
- Centro de Pesquisas Biológicas de Indaial, Indaial, Brazil
- Universidade Regional de Blumenau - FURB, Blumenau, Brazil
| | | | - Zelinda Maria Braga Hirano
- Centro de Pesquisas Biológicas de Indaial, Indaial, Brazil
- Universidade Regional de Blumenau - FURB, Blumenau, Brazil
| | | | - Alcides Pissinatti
- Centro de Primatologia do Rio de Janeiro/INEA, Guapimirim, Brazil
- Centro Universitário Serra dos Órgãos, Teresópolis, Brazil
| | - Cláudio Tadeu Daniel-Ribeiro
- Centro de Pesquisa, Diagnóstico e Treinamento em Malária, Fiocruz, Rio de Janeiro, Brazil
- Laboratório de Pesquisa em Malária, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil
| | - Taís Nóbrega de Sousa
- Grupo de Pesquisa em Biologia Molecular e Imunologia da Malária, Instituto René Rachou, Fundação Oswaldo Cruz (Fiocruz), Belo Horizonte, Brazil
| | - Cristiana Ferreira Alves de Brito
- Grupo de Pesquisa em Biologia Molecular e Imunologia da Malária, Instituto René Rachou, Fundação Oswaldo Cruz (Fiocruz), Belo Horizonte, Brazil.
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15
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Ding XC, Incardona S, Serra-Casas E, Charnaud SC, Slater HC, Domingo GJ, Adams ER, ter Kuile FO, Samuels AM, Kariuki S, Dittrich S. Malaria in pregnancy (MiP) studies assessing the clinical performance of highly sensitive rapid diagnostic tests (HS-RDT) for Plasmodium falciparum detection. Malar J 2023; 22:60. [PMID: 36803858 PMCID: PMC9942317 DOI: 10.1186/s12936-023-04445-1] [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: 07/12/2022] [Accepted: 01/06/2023] [Indexed: 02/22/2023] Open
Abstract
BACKGROUND Rapid diagnostic tests (RDTs) are effective tools to diagnose and inform the treatment of malaria in adults and children. The recent development of a highly sensitive rapid diagnostic test (HS-RDT) for Plasmodium falciparum has prompted questions over whether it could improve the diagnosis of malaria in pregnancy and pregnancy outcomes in malaria endemic areas. METHODS This landscape review collates studies addressing the clinical performance of the HS-RDT. Thirteen studies were identified comparing the HS-RDT and conventional RDT (co-RDT) to molecular methods to detect malaria in pregnancy. Using data from five completed studies, the association of epidemiological and pregnancy-related factors on the sensitivity of HS-RDT, and comparisons with co-RDT were investigated. The studies were conducted in 4 countries over a range of transmission intensities in largely asymptomatic women. RESULTS Sensitivity of both RDTs varied widely (HS-RDT range 19.6 to 85.7%, co-RDT range 22.8 to 82.8% compared to molecular testing) yet HS-RDT detected individuals with similar parasite densities across all the studies including different geographies and transmission areas [geometric mean parasitaemia around 100 parasites per µL (p/µL)]. HS-RDTs were capable of detecting low-density parasitaemias and in one study detected around 30% of infections with parasite densities of 0-2 p/µL compared to the co-RDT in the same study which detected around 15%. CONCLUSION The HS-RDT has a slightly higher analytical sensitivity to detect malaria infections in pregnancy than co-RDT but this mostly translates to only fractional and not statistically significant improvement in clinical performance by gravidity, trimester, geography or transmission intensity. The analysis presented here highlights the need for larger and more studies to evaluate incremental improvements in RDTs. The HS-RDT could be used in any situation where co-RDT are currently used for P. falciparum diagnosis, if storage conditions can be adhered to.
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Affiliation(s)
- Xavier C. Ding
- grid.452485.a0000 0001 1507 3147FIND, Geneva, Switzerland
| | | | | | | | - Hannah C. Slater
- grid.415269.d0000 0000 8940 7771Diagnostics Program, PATH, Seattle, USA
| | | | - Emily R. Adams
- grid.48004.380000 0004 1936 9764Department of Tropical Disease Biology and Department of Clinical Sciences, Liverpool School of Tropical Medicine, Liverpool, L3 5QA UK
| | - Feiko O. ter Kuile
- grid.48004.380000 0004 1936 9764Department of Tropical Disease Biology and Department of Clinical Sciences, Liverpool School of Tropical Medicine, Liverpool, L3 5QA UK
| | - Aaron M. Samuels
- grid.512515.7Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention (CDC), Kisumu, Kenya ,grid.467642.50000 0004 0540 3132Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention (CDC), Atlanta, Georgia USA
| | - Simon Kariuki
- grid.33058.3d0000 0001 0155 5938Kenya Medical Research Institute-Centre for Global Health Research, Kisumu, Kenya
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16
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Stadler E, Cromer D, Ogunlade S, Ongoiba A, Doumbo S, Kayentao K, Traore B, Crompton PD, Portugal S, Davenport MP, Khoury DS. Evidence for exposure dependent carriage of malaria parasites across the dry season: modelling analysis of longitudinal data. Malar J 2023; 22:42. [PMID: 36737743 PMCID: PMC9898990 DOI: 10.1186/s12936-023-04461-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Accepted: 01/17/2023] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND In malaria endemic regions, transmission of Plasmodium falciparum parasites is often seasonal with very low transmission during the dry season and high transmission in the wet season. Parasites survive the dry season within some individuals who experience prolonged carriage of parasites and are thought to 'seed' infection in the next transmission season. METHODS Dry season carriers and their role in the subsequent transmission season are characterized using a combination of mathematical simulations and data analysis of previously described data from a longitudinal study in Mali of individuals aged 3 months-12 years (n = 579). RESULTS Simulating the life-history of individuals experiencing repeated exposure to infection predicts that dry season carriage is more likely in the oldest, most exposed and most immune individuals. This hypothesis is supported by the data from Mali, which shows that carriers are significantly older, experience a higher biting rate at the beginning of the transmission season and develop clinical malaria later than non-carriers. Further, since the most exposed individuals in a community are most likely to be dry season carriers, this is predicted to enable a more than twofold faster spread of parasites into the mosquito population at the start of the subsequent wet season. CONCLUSIONS Carriage of malaria parasites over the months-long dry season in Mali is most likely in the older, more exposed and more immune children. These children may act as super-spreaders facilitating the fast spread of parasites at the beginning of the next transmission season.
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Affiliation(s)
- Eva Stadler
- grid.1005.40000 0004 4902 0432The Kirby Institute, UNSW Sydney, Sydney, NSW 2052 Australia
| | - Deborah Cromer
- grid.1005.40000 0004 4902 0432The Kirby Institute, UNSW Sydney, Sydney, NSW 2052 Australia
| | - Samson Ogunlade
- grid.1005.40000 0004 4902 0432The Kirby Institute, UNSW Sydney, Sydney, NSW 2052 Australia
| | - Aissata Ongoiba
- grid.461088.30000 0004 0567 336XMalaria Research and Training Centre, Department of Epidemiology of Parasitic Diseases, International Center of Excellence in Research, University of Sciences, Technique, and Technology of Bamako, 91094 Bamako, Mali
| | - Safiatou Doumbo
- grid.461088.30000 0004 0567 336XMalaria Research and Training Centre, Department of Epidemiology of Parasitic Diseases, International Center of Excellence in Research, University of Sciences, Technique, and Technology of Bamako, 91094 Bamako, Mali
| | - Kassoum Kayentao
- grid.461088.30000 0004 0567 336XMalaria Research and Training Centre, Department of Epidemiology of Parasitic Diseases, International Center of Excellence in Research, University of Sciences, Technique, and Technology of Bamako, 91094 Bamako, Mali
| | - Boubacar Traore
- grid.461088.30000 0004 0567 336XMalaria Research and Training Centre, Department of Epidemiology of Parasitic Diseases, International Center of Excellence in Research, University of Sciences, Technique, and Technology of Bamako, 91094 Bamako, Mali
| | - Peter D. Crompton
- grid.419681.30000 0001 2164 9667Malaria Infection Biology and Immunity Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, USA
| | - Silvia Portugal
- grid.419681.30000 0001 2164 9667Malaria Infection Biology and Immunity Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, USA
| | - Miles P. Davenport
- grid.1005.40000 0004 4902 0432The Kirby Institute, UNSW Sydney, Sydney, NSW 2052 Australia
| | - David S. Khoury
- grid.1005.40000 0004 4902 0432The Kirby Institute, UNSW Sydney, Sydney, NSW 2052 Australia
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17
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Oyibo W, Latham V, Oladipo O, Ntadom G, Uhomoibhi P, Ogbulafor N, Okoronkwo C, Okoh F, Mahmoud A, Shekarau E, Oresanya O, Cherima YJ, Jalingo I, Abba B, Audu M, Conway DJ. Malaria parasite density and detailed qualitative microscopy enhances large-scale profiling of infection endemicity in Nigeria. Sci Rep 2023; 13:1599. [PMID: 36709336 PMCID: PMC9884197 DOI: 10.1038/s41598-023-27535-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Accepted: 01/04/2023] [Indexed: 01/29/2023] Open
Abstract
With global progress towards malaria reduction stalling, further analysis of epidemiology is required, particularly in countries with the highest burden. National surveys have mostly analysed infection prevalence, while large-scale data on parasite density and different developmental forms rarely available. In Nigeria, the country with the largest burden globally, blood slide microscopy of children up to 5 years of age was conducted in the 2018 National Demographic and Health Survey, and parasite prevalence previously reported. In the current study, malaria parasite density measurements are reported and analysed for 7783 of the children sampled across the 36 states within the six geopolitical zones of the country. Asexual and sexual stages, and infections with different malaria parasite species are analysed. Across all states of Nigeria, there was a positive correlation between mean asexual parasite density within infected individuals and prevalence of infection in the community (Spearman's rho = 0.39, P = 0.02). Asexual parasite densities were highest in the northern geopolitical zones (geometric means > 2000 μL-1), extending the evidence of exceptionally high infection burden in many areas. Sexual parasite prevalence in each state was highly correlated with asexual parasite prevalence (Spearman's rho = 0.70, P < 0.001), although sexual parasite densities were low (geometric means < 100 μL-1 in all zones). Infants had lower parasite densities than children above 1 year of age, but there were no differences between male and female children. Most infections were of P. falciparum, which had higher asexual densities but lower sexual parasite densities than P. malariae or P. ovale mono-infections. However, mixed species infections had the highest asexual parasite densities. It is recommended that future large surveys in high burden countries measure parasite densities as well as developmental stages and species, to improve the quality of malaria epidemiology and tracking of future changes.
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Affiliation(s)
- Wellington Oyibo
- ANDI Centre of Excellence for Malaria Diagnosis, College of Medicine, University of Lagos, Lagos, Nigeria.
| | | | - Oladosu Oladipo
- ANDI Centre of Excellence for Malaria Diagnosis, College of Medicine, University of Lagos, Lagos, Nigeria
- Pure and Applied Biology Programme, Bowen University, Iwo, Osun State, Nigeria
| | - Godwin Ntadom
- Epidemiology Unit, Federal Ministry of Health, Abuja, Nigeria
- National Malaria Elimination Programme (NMEP), Federal Ministry of Health, Abuja, Nigeria
| | - Perpetua Uhomoibhi
- National Malaria Elimination Programme (NMEP), Federal Ministry of Health, Abuja, Nigeria
| | - Nnenna Ogbulafor
- National Malaria Elimination Programme (NMEP), Federal Ministry of Health, Abuja, Nigeria
| | - Chukwu Okoronkwo
- National Malaria Elimination Programme (NMEP), Federal Ministry of Health, Abuja, Nigeria
| | - Festus Okoh
- National Malaria Elimination Programme (NMEP), Federal Ministry of Health, Abuja, Nigeria
| | - Aminu Mahmoud
- National Malaria Elimination Programme (NMEP), Federal Ministry of Health, Abuja, Nigeria
| | - Emmanuel Shekarau
- National Malaria Elimination Programme (NMEP), Federal Ministry of Health, Abuja, Nigeria
| | | | | | | | - Bintu Abba
- National Population Commission, Abuja, Nigeria
| | - Mohammed Audu
- National Malaria Elimination Programme (NMEP), Federal Ministry of Health, Abuja, Nigeria
| | - David J Conway
- London School of Hygiene and Tropical Medicine, London, UK.
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18
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Asymptomatic Plasmodium infection among primary schoolchildren and Anopheles-mediated malaria transmission: A cross-sectional study in Ouidah; south-western Benin. Parasite Epidemiol Control 2023; 21:e00285. [PMID: 36714884 PMCID: PMC9880241 DOI: 10.1016/j.parepi.2023.e00285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Revised: 11/11/2022] [Accepted: 01/16/2023] [Indexed: 01/20/2023] Open
Abstract
Understanding the contribution of asymptomatic Plasmodium carriers in malaria transmission might be helpful to design and implement new control measures. The present study explored the prevalence of asymptomatic and symptomatic Plasmodium infections (asexual and sexual stages) and the contribution of asymptomatic P. falciparum carriers to Anopheles-mediated malaria transmission in Ouidah (Benin). Thick and thin blood smears were examined from finger-prick blood specimens using light microscopy, and the density of both asexual and sexual stages of Plasmodium species was calculated. Infectivity of gametocyte-infected blood samples to Anopheles gambiae was assessed through direct membrane feeding assays. The prevalence of asymptomatic Plasmodium infections was 28.73% (289/1006). All the asymptomatic gametocyte-carriers (19/19), with gametocytaemia ranging from 10 - 1200 gametocytes/μL of blood, were infectious to An. gambiae mosquitoes. The mean oocyst prevalences varied significantly (χ 2 = 16.42, df = 7, p = 0.02) among laboratory mosquito strains (6.9 - 39.4%) and near-field mosquitoes (4.9 - 27.2%). Likewise, significant variation (χ 2 = 56.85, df = 7, p = 6.39 × 10-10) was observed in oocyst intensity. Our findings indicate that asymptomatic Plasmodium carriers could significantly contribute to malaria transmission. Overall, this study highlights the importance of diagnosing and treating asymptomatic and symptomatic infection carriers during malaria control programmes.
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Key Words
- An. gambiae
- An., Anopheles
- Asymptomatic
- CX, Carbamates
- DDT, Dichlorodiphenyltrichloroethane
- DMFAs, Direct membrane feeding assays
- G119S, Glycine substitution by Serine at codon 119
- Gametocyte
- IPT, Intermittent Preventive Therapy
- IRS, Indoor residual spraying
- ITNs, Insecticide-treated bed nets
- L1014F, Leucine substitution by Phenylalanine at codon 1014
- MDA, Mass Drug Administration
- MSaT, Mass Screening and Treatment
- NMCP, National Malaria Control Programme
- OP, Organophosphates
- PYR, Pyrethroids
- Plasmodium falciparum
- Transmission
- USA, United States of America
- WBCs, White blood cells
- WHO, Word Health Organization
- s.l., sensu lato
- s.s., sensu stricto
- spp., species
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19
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Sustainable Radical Cure of the Latent Malarias. Infect Dis (Lond) 2023. [DOI: 10.1007/978-1-0716-2463-0_896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/09/2023] Open
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20
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Singh A, Singh MP, Bhandari S, Rajvanshi H, Nisar S, Telasey V, Jayswar H, Mishra AK, Das A, Kaur H, Lal AA, Bharti PK. Significance of nested PCR testing for the detection of low-density malaria infection amongst febrile patients from the Malaria Elimination Demonstration Project in Mandla, Madhya Pradesh, India. Malar J 2022; 21:341. [PMCID: PMC9669540 DOI: 10.1186/s12936-022-04355-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 10/27/2022] [Indexed: 11/18/2022] Open
Abstract
Abstract
Background
Low-density malaria infections (LDMI) are defined as infections that are missed by the rapid diagnostic test (RDT) and/or microscopy which can lead to continued transmission and poses a challenge in malaria elimination efforts. This study was conducted to investigate the prevalence of LDMI in febrile cases using species-specific nested Polymerase Chain Reaction (PCR) tests in the Malaria Elimination Demonstration Project, where routine diagnosis was conducted using RDT.
Methods
Every 10th fever case from a cross-sectional community based fever surveillance was tested with RDT, microscopy and nested PCR. Parasite DNA was isolated from the filter paper using Chelex based method. Molecular diagnosis by nested PCR was performed targeting 18SrRNA gene for Plasmodium species.
Results
The prevalence of malaria was 2.50% (436/17405) diagnosed by PCR, 1.13% (196/17405) by RDT, and 0.68% (118/ 17,405) by microscopy. Amongst 17,405 febrile samples, the prevalence of LDMI was 1.51% (263/17405) (95% CI 1.33–1.70), which were missed by conventional methods. Logistic regression analysis revealed that illness during summer season [OR = 1.90 (p < 0.05)] and cases screened within three days of febrile illness [OR = 5.27 (p < 0.001)] were the statistically significant predictors of LDMI.
Conclusion
The prevalence of malaria among febrile cases using PCR was 2.50% (436/17405) as compared to 1.13% (196/17405) by RDT. Higher number of the LDMI cases were found in subjects with ≤ 3 days mean duration of reported fever, which was statistically significant (p < 0.001). This observation suggests that an early detection of malaria with a more sensitive diagnostic method or repeat testing of the all negative cases may be useful for curtailing malaria transmission. Therefore, malaria elimination programme would benefit from using more sensitive and specific diagnostic methods, such as PCR.
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21
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Turnbull LB, Ayodo G, Knight V, John CC, McHenry MS, Tran TM. Evaluation of an ultrasensitive HRP2-based rapid diagnostic test for detection of asymptomatic Plasmodium falciparum parasitaemia among children in western Kenya. Malar J 2022; 21:337. [PMID: 36380379 PMCID: PMC9667565 DOI: 10.1186/s12936-022-04351-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: 06/10/2022] [Accepted: 10/21/2022] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND Accurate detection of asymptomatic malaria parasitaemia in children living in high transmission areas is important for malaria control and reduction programmes that employ screen-and-treat surveillance strategies. Relative to microscopy and conventional rapid diagnostic tests (RDTs), ultrasensitive RDTs (us-RDTs) have demonstrated reduced limits of detection with increased sensitivity to detect parasitaemia in symptomatic individuals. In this study, the performance of the NxTek™ Eliminate Malaria P.f test was compared with traditional microscopy and quantitative polymerase chain reaction (qPCR) testing methods of detection for P. falciparum parasitaemia among asymptomatic children aged 7-14 years living in an area of high malaria transmission intensity in western Kenya. METHODS In October 2020, 240 healthy children without any reported malaria symptoms were screened for the presence of P. falciparum parasitaemia; 120 children were randomly selected to participate in a follow-up visit at 6-10 weeks. Malaria parasitaemia was assessed by blood-smear microscopy, us-RDT, and qPCR of a conserved var gene sequence from genomic DNA extracted from dried blood spots. Sensitivity, specificity, and predictive values were calculated for field diagnostic methods using qPCR as the gold standard. Comparison of detectable parasite density distributions and area under the curve were also calculated to determine the effectiveness of the us-RDT in detecting asymptomatic infections with low parasite densities. RESULTS The us-RDT detected significantly more asymptomatic P. falciparum infections than microscopy (42.5% vs. 32.2%, P = 0.002). The positive predictive value was higher for microscopy (92.2%) than for us-RDT (82.4%). However, false negative rates were high for microscopy and us-RDT, with negative predictive values of 53.7% and 54.6%, respectively. While us-RDT detected significantly more infections than microscopy overall, the density distribution of detectable infections did not differ (P = 0.21), and qPCR detected significantly more low-density infections than both field methods (P < 0.001, for both comparisons). CONCLUSIONS Us-RDT is more sensitive than microscopy for detecting asymptomatic malaria parasitaemia in children. Though the detectable parasite density distributions by us-RDT in our specific study did not significantly differ from microscopy, the additional sensitivity of the us-RDT resulted in more identified asymptomatic infections in this important group of the population and makes the use of the us-RDT advisable compared to other currently available malaria field detection methods.
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Affiliation(s)
- Lindsey B Turnbull
- Ryan White Center for Pediatric Infectious Diseases and Global Health, Indiana University School of Medicine, Indianapolis, IN, USA.
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, USA.
| | - George Ayodo
- Jaramogi Oginga Odinga University of Science and Technology, Bondo, Kenya
| | - Veronicah Knight
- Academic Model Providing Access to Healthcare (AMPATH), Eldoret, Kenya
| | - Chandy C John
- Ryan White Center for Pediatric Infectious Diseases and Global Health, Indiana University School of Medicine, Indianapolis, IN, USA
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Megan S McHenry
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, USA
- Academic Model Providing Access to Healthcare (AMPATH), Eldoret, Kenya
| | - Tuan M Tran
- Ryan White Center for Pediatric Infectious Diseases and Global Health, Indiana University School of Medicine, Indianapolis, IN, USA
- Division of Infectious Diseases, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
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22
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Shah MP, Chebore W, Lyles RH, Otieno K, Zhou Z, Plucinski M, Waller LA, Odongo W, Lindblade KA, Kariuki S, Samuels AM, Desai M, Mitchell RM, Shi YP. Novel application of one-step pooled molecular testing and maximum likelihood approaches to estimate the prevalence of malaria parasitaemia among rapid diagnostic test negative samples in western Kenya. Malar J 2022; 21:319. [PMID: 36336700 PMCID: PMC9638440 DOI: 10.1186/s12936-022-04323-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Accepted: 10/07/2022] [Indexed: 11/08/2022] Open
Abstract
Abstract
Background
Detection of malaria parasitaemia in samples that are negative by rapid diagnostic tests (RDTs) requires resource-intensive molecular tools. While pooled testing using a two-step strategy provides a cost-saving alternative to the gold standard of individual sample testing, statistical adjustments are needed to improve accuracy of prevalence estimates for a single step pooled testing strategy.
Methods
A random sample of 4670 malaria RDT negative dried blood spot samples were selected from a mass testing and treatment trial in Asembo, Gem, and Karemo, western Kenya. Samples were tested for malaria individually and in pools of five, 934 pools, by one-step quantitative polymerase chain reaction (qPCR). Maximum likelihood approaches were used to estimate subpatent parasitaemia (RDT-negative, qPCR-positive) prevalence by pooling, assuming poolwise sensitivity and specificity was either 100% (strategy A) or imperfect (strategy B). To improve and illustrate the practicality of this estimation approach, a validation study was constructed from pools allocated at random into main (734 pools) and validation (200 pools) subsets. Prevalence was estimated using strategies A and B and an inverse-variance weighted estimator and estimates were weighted to account for differential sampling rates by area.
Results
The prevalence of subpatent parasitaemia was 14.5% (95% CI 13.6–15.3%) by individual qPCR, 9.5% (95% CI (8.5–10.5%) by strategy A, and 13.9% (95% CI 12.6–15.2%) by strategy B. In the validation study, the prevalence by individual qPCR was 13.5% (95% CI 12.4–14.7%) in the main subset, 8.9% (95% CI 7.9–9.9%) by strategy A, 11.4% (95% CI 9.9–12.9%) by strategy B, and 12.8% (95% CI 11.2–14.3%) using inverse-variance weighted estimator from poolwise validation. Pooling, including a 20% validation subset, reduced costs by 52% compared to individual testing.
Conclusions
Compared to individual testing, a one-step pooled testing strategy with an internal validation subset can provide accurate prevalence estimates of PCR-positivity among RDT-negatives at a lower cost.
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23
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Assogba BS, Sillah S, Opondo KO, Cham ST, Camara MM, Jadama L, Camara L, Ndiaye A, Wathuo M, Jawara M, Diabaté A, Achan J, D'Alessandro U. Anopheles gambiae s.l. swarms trapping as a complementary tool against residual malaria transmission in eastern Gambia. Sci Rep 2022; 12:17057. [PMID: 36224312 PMCID: PMC9556655 DOI: 10.1038/s41598-022-21577-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Accepted: 09/29/2022] [Indexed: 12/30/2022] Open
Abstract
Malaria remains a major health problem and vector control is an essential approach to decrease its burden, although it is threatened by insecticide resistance. New approaches for vector control are needed. The females of Anopheles gambiae s.l. mate once in their life and in the swarms formed by males. Trapping swarms of Anopheles gambiae s.l. males is a potential new intervention for vector control, alternative to the use of insecticides, as it would disrupt mating . The proof-of-concept pilot study aiming at investigating swarm trapping as a potential vector control intervention, was carried out in 6 villages as in eastern Gambia. Swarms of Anopheles gambiae s.l. were identified and their size, height, and duration determined during the baseline year. Swarm trapping by local volunteers was implemented the following transmission season in 4 villages while the other 2 villages were taken as controls. Entomological outcomes were monitored by Human Landing Catches and Pyrethrum Spray Catches. A cross-sectional survey to determine malaria prevalence was carried out at the peak of the malaria transmission season for two consecutive years. At baseline, 23 swarming sites of Anopheles gambiae s.l. were identified. Before the intervention, mean indoor resting density per house and malaria prevalence were similar between control and intervention villages. Following the intervention, Anopheles gambiae s.l. indoor resting density was 44% lower in intervention than in control villages (adj IRR: 0.0.56; 95% CI 0.47-0.68); the odds of malaria infections were 68% lower in intervention than in control villages (OR: 0.32; 95% CI 0.11-0.97). Swarm trapping seems to be a promising, community-based vector control intervention that could reduce malaria prevalence by reducing vector density. Such results should be further investigated and confirmed by larger cluster-randomized trials.
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Affiliation(s)
- Benoît Sessinou Assogba
- Disease Control and Elimination Theme, Medical Research Council, Unit The Gambia at London School of Hygiene and Tropical Medicine, PO Box 273, Banjul, The Gambia.
| | - Salimina Sillah
- Disease Control and Elimination Theme, Medical Research Council, Unit The Gambia at London School of Hygiene and Tropical Medicine, PO Box 273, Banjul, The Gambia
| | - Kevin O Opondo
- Disease Control and Elimination Theme, Medical Research Council, Unit The Gambia at London School of Hygiene and Tropical Medicine, PO Box 273, Banjul, The Gambia
| | - Sheikh Tijan Cham
- Disease Control and Elimination Theme, Medical Research Council, Unit The Gambia at London School of Hygiene and Tropical Medicine, PO Box 273, Banjul, The Gambia
| | - Muhammed M Camara
- Disease Control and Elimination Theme, Medical Research Council, Unit The Gambia at London School of Hygiene and Tropical Medicine, PO Box 273, Banjul, The Gambia
| | - Lamin Jadama
- Disease Control and Elimination Theme, Medical Research Council, Unit The Gambia at London School of Hygiene and Tropical Medicine, PO Box 273, Banjul, The Gambia
| | - Lamin Camara
- Disease Control and Elimination Theme, Medical Research Council, Unit The Gambia at London School of Hygiene and Tropical Medicine, PO Box 273, Banjul, The Gambia
| | - Assane Ndiaye
- Laboratoire d'Ecologie Vectorielle et Parasitaire, Faculté des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal
| | - Miriam Wathuo
- Statistic and Bioinformatic Department, Medical Research Council, Unit The Gambia at London School of Hygiene and Tropical Medicine, PO Box 273, Banjul, The Gambia
| | - Musa Jawara
- Disease Control and Elimination Theme, Medical Research Council, Unit The Gambia at London School of Hygiene and Tropical Medicine, PO Box 273, Banjul, The Gambia
| | - Abdoulaye Diabaté
- Institut de Recherche en Science de la Santé/Centre Muraz, BP 545, Bobo-Dioulasso, Burkina Faso
| | - Jane Achan
- Disease Control and Elimination Theme, Medical Research Council, Unit The Gambia at London School of Hygiene and Tropical Medicine, PO Box 273, Banjul, The Gambia
| | - Umberto D'Alessandro
- Disease Control and Elimination Theme, Medical Research Council, Unit The Gambia at London School of Hygiene and Tropical Medicine, PO Box 273, Banjul, The Gambia.
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24
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Torres K, Ferreira MU, Castro MC, Escalante AA, Conn JE, Villasis E, da Silva Araujo M, Almeida G, Rodrigues PT, Corder RM, Fernandes ARJ, Calil PR, Ladeia WA, Garcia-Castillo SS, Gomez J, do Valle Antonelli LR, Gazzinelli RT, Golenbock DT, Llanos-Cuentas A, Gamboa D, Vinetz JM. Malaria Resilience in South America: Epidemiology, Vector Biology, and Immunology Insights from the Amazonian International Center of Excellence in Malaria Research Network in Peru and Brazil. Am J Trop Med Hyg 2022; 107:168-181. [PMID: 36228921 PMCID: PMC9662219 DOI: 10.4269/ajtmh.22-0127] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 05/28/2022] [Indexed: 11/07/2022] Open
Abstract
The 1990s saw the rapid reemergence of malaria in Amazonia, where it remains an important public health priority in South America. The Amazonian International Center of Excellence in Malaria Research (ICEMR) was designed to take a multidisciplinary approach toward identifying novel malaria control and elimination strategies. Based on geographically and epidemiologically distinct sites in the Northeastern Peruvian and Western Brazilian Amazon regions, synergistic projects integrate malaria epidemiology, vector biology, and immunology. The Amazonian ICEMR's overarching goal is to understand how human behavior and other sociodemographic features of human reservoirs of transmission-predominantly asymptomatically parasitemic people-interact with the major Amazonian malaria vector, Nyssorhynchus (formerly Anopheles) darlingi, and with human immune responses to maintain malaria resilience and continued endemicity in a hypoendemic setting. Here, we will review Amazonian ICEMR's achievements on the synergies among malaria epidemiology, Plasmodium-vector interactions, and immune response, and how those provide a roadmap for further research, and, most importantly, point toward how to achieve malaria control and elimination in the Americas.
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Affiliation(s)
- Katherine Torres
- Institute of Tropical Medicine Alexander von Humboldt, Universidad Peruana Cayetano Heredia, Lima, Peru
- Laboratorios de Investigación y Desarrollo, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Marcelo U. Ferreira
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, Sao Paulo, Brazil
| | - Marcia C. Castro
- Department of Global Health and Population, Harvard T. H. Chan School of Public Health, Boston, Massachusetts
| | - Ananias A. Escalante
- Department of Biology and Institute for Genomics and Evolutionary Medicine, Temple University, Philadelphia, Pennsylvania
| | - Jan E. Conn
- Department of Biomedical Sciences, School of Public Health, University at Albany, State University of New York, Albany, New York
- Wadsworth Center, New York State Department of Health, Albany, New York
| | - Elizabeth Villasis
- Institute of Tropical Medicine Alexander von Humboldt, Universidad Peruana Cayetano Heredia, Lima, Peru
- Laboratorios de Investigación y Desarrollo, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru
| | | | - Gregorio Almeida
- Instituto de Pesquisas Rene Rachou, Fundação Oswaldo Cruz, Belo Horizonte, Brazil
| | - Priscila T. Rodrigues
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, Sao Paulo, Brazil
| | - Rodrigo M. Corder
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, Sao Paulo, Brazil
| | - Anderson R. J. Fernandes
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, Sao Paulo, Brazil
| | - Priscila R. Calil
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, Sao Paulo, Brazil
| | - Winni A. Ladeia
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, Sao Paulo, Brazil
| | - Stefano S. Garcia-Castillo
- Laboratorios de Investigación y Desarrollo, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Joaquin Gomez
- Laboratorios de Investigación y Desarrollo, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru
| | | | - Ricardo T. Gazzinelli
- Instituto de Pesquisas Rene Rachou, Fundação Oswaldo Cruz, Belo Horizonte, Brazil
- Division of Infectious Disease and Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts
| | - Douglas T. Golenbock
- Division of Infectious Disease and Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts
| | - Alejandro Llanos-Cuentas
- Institute of Tropical Medicine Alexander von Humboldt, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Dionicia Gamboa
- Institute of Tropical Medicine Alexander von Humboldt, Universidad Peruana Cayetano Heredia, Lima, Peru
- Laboratorios de Investigación y Desarrollo, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Joseph M. Vinetz
- Institute of Tropical Medicine Alexander von Humboldt, Universidad Peruana Cayetano Heredia, Lima, Peru
- Laboratorios de Investigación y Desarrollo, Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru
- Section of Infectious Diseases, Department of Internal Medicine, Yale School of Medicine, New Haven, Connecticut
- Address correspondence to Joseph M. Vinetz, Section of Infectious Diseases, Department of Internal Medicine, Yale School of Medicine, 25 York St., Winchester 403D, PO Box 802022, New Haven, CT 06520. E-mail:
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25
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Hergott DEB, Owalla TJ, Balkus JE, Apio B, Lema J, Cemeri B, Akileng A, Seilie AM, Chavtur C, Staubus W, Chang M, Egwang TG, Murphy SC. Feasibility of community at-home dried blood spot collection combined with pooled reverse transcription PCR as a viable and convenient method for malaria epidemiology studies. Malar J 2022; 21:221. [PMID: 35836179 PMCID: PMC9284728 DOI: 10.1186/s12936-022-04239-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 06/26/2022] [Indexed: 01/08/2023] Open
Abstract
Background Many Plasmodium infections in endemic regions exist at densities below the limit of detection of standard diagnostic tools. These infections threaten control efforts and may impact vaccine and therapeutic drug studies. Simple, cost-effective methods are needed to study the natural history of asymptomatic submicroscopic parasitaemia. Self-collected dried blood spots (DBS) analysed using pooled and individual quantitative reverse transcription polymerase chain reaction (qRT-PCR) provide such a solution. Here, the feasibility and acceptability of daily at-home DBS collections for qRT-PCR was studied to better understand low-density infections. Methods Rapid diagnostic test (RDT)-negative individuals in Katakwi District, northeastern Uganda, were recruited between April and May 2021. Venous blood samples and clinic-collected DBS were taken at enrollment and at four weekly clinic visits. Participants were trained in DBS collection and asked to collect six DBS weekly between clinic visits. Opinions about the collection process were solicited using daily Diary Cards and a Likert scale survey at the final study visit. Venous blood and DBS were analysed by Plasmodium 18S rRNA qRT-PCR. The number of participants completing the study, total DBS collected, and opinions of the process were analysed to determine compliance and acceptability. The human internal control mRNA and Plasmodium 18S rRNA were evaluated for at-home vs. clinic-collected DBS and venous blood to assess quality and accuracy of at-home collected samples. Results One-hundred two adults and 29 children were enrolled, and 95 and 26 completed the study, respectively. Three individuals withdrew due to pain or inconvenience of procedures. Overall, 96% of participants collected ≥ 16 of 24 at-home DBS, and 87% of DBS contained ≥ 40 µL of blood. The procedure was well tolerated and viewed favourably by participants. At-home collected DBS were acceptable for qRT-PCR and showed less than a one qRT-PCR cycle threshold shift in the human control mRNA compared to clinic-collected DBS. Correlation between Plasmodium falciparum 18S rRNA from paired whole blood and DBS was high (R = 0.93). Conclusions At-home DBS collection is a feasible, acceptable, and robust method to obtain blood to evaluate the natural history of low-density Plasmodium infections by qRT-PCR. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-022-04239-x.
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Affiliation(s)
- Dianna E B Hergott
- Department of Laboratory Medicine and Pathology, University of Washington, 750 Republican St., F870, Seattle, WA, 98109, USA.,Department of Epidemiology, School of Public Health, University of Washington, Seattle, WA, USA
| | - Tonny J Owalla
- Med Biotech Laboratories, P.O. Box 9364, Kampala, Uganda
| | - Jennifer E Balkus
- Department of Epidemiology, School of Public Health, University of Washington, Seattle, WA, USA
| | | | - Jimmy Lema
- Med Biotech Laboratories, P.O. Box 9364, Kampala, Uganda
| | - Barbara Cemeri
- Med Biotech Laboratories, P.O. Box 9364, Kampala, Uganda
| | - Andrew Akileng
- Med Biotech Laboratories, P.O. Box 9364, Kampala, Uganda
| | - Annette M Seilie
- Department of Laboratory Medicine and Pathology, University of Washington, 750 Republican St., F870, Seattle, WA, 98109, USA.,Center for Emerging and Re-Emerging Infectious Diseases, University of Washington, Seattle, WA, USA
| | - Chris Chavtur
- Department of Laboratory Medicine and Pathology, University of Washington, 750 Republican St., F870, Seattle, WA, 98109, USA.,Center for Emerging and Re-Emerging Infectious Diseases, University of Washington, Seattle, WA, USA
| | - Weston Staubus
- Department of Laboratory Medicine and Pathology, University of Washington, 750 Republican St., F870, Seattle, WA, 98109, USA.,Center for Emerging and Re-Emerging Infectious Diseases, University of Washington, Seattle, WA, USA
| | - Ming Chang
- Department of Laboratory Medicine and Pathology, University of Washington, 750 Republican St., F870, Seattle, WA, 98109, USA.,Center for Emerging and Re-Emerging Infectious Diseases, University of Washington, Seattle, WA, USA
| | | | - Sean C Murphy
- Department of Laboratory Medicine and Pathology, University of Washington, 750 Republican St., F870, Seattle, WA, 98109, USA. .,Center for Emerging and Re-Emerging Infectious Diseases, University of Washington, Seattle, WA, USA. .,Department of Microbiology, University of Washington, Seattle, WA, USA.
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26
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Lyimo BM, Popkin-Hall ZR, Giesbrecht DJ, Mandara CI, Madebe RA, Bakari C, Pereus D, Seth MD, Ngamba RM, Mbwambo RB, MacInnis B, Mbwambo D, Garimo I, Chacky F, Aaron S, Lusasi A, Molteni F, Njau R, Cunningham JA, Lazaro S, Mohamed A, Juliano JJ, Bailey J, Ishengoma DS. Potential Opportunities and Challenges of Deploying Next Generation Sequencing and CRISPR-Cas Systems to Support Diagnostics and Surveillance Towards Malaria Control and Elimination in Africa. Front Cell Infect Microbiol 2022; 12:757844. [PMID: 35909968 PMCID: PMC9326448 DOI: 10.3389/fcimb.2022.757844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Accepted: 03/17/2022] [Indexed: 12/02/2022] Open
Abstract
Recent developments in molecular biology and genomics have revolutionized biology and medicine mainly in the developed world. The application of next generation sequencing (NGS) and CRISPR-Cas tools is now poised to support endemic countries in the detection, monitoring and control of endemic diseases and future epidemics, as well as with emerging and re-emerging pathogens. Most low and middle income countries (LMICs) with the highest burden of infectious diseases still largely lack the capacity to generate and perform bioinformatic analysis of genomic data. These countries have also not deployed tools based on CRISPR-Cas technologies. For LMICs including Tanzania, it is critical to focus not only on the process of generation and analysis of data generated using such tools, but also on the utilization of the findings for policy and decision making. Here we discuss the promise and challenges of NGS and CRISPR-Cas in the context of malaria as Africa moves towards malaria elimination. These innovative tools are urgently needed to strengthen the current diagnostic and surveillance systems. We discuss ongoing efforts to deploy these tools for malaria detection and molecular surveillance highlighting potential opportunities presented by these innovative technologies as well as challenges in adopting them. Their deployment will also offer an opportunity to broadly build in-country capacity in pathogen genomics and bioinformatics, and to effectively engage with multiple stakeholders as well as policy makers, overcoming current workforce and infrastructure challenges. Overall, these ongoing initiatives will build the malaria molecular surveillance capacity of African researchers and their institutions, and allow them to generate genomics data and perform bioinformatics analysis in-country in order to provide critical information that will be used for real-time policy and decision-making to support malaria elimination on the continent.
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Affiliation(s)
- Beatus M. Lyimo
- National Institute for Medical Research, Dar es Salaam, Tanzania
- School of Life Sciences and Bio-Engineering, Nelson Mandela African Institution of Science and Technology, Arusha, Tanzania
| | | | - David J. Giesbrecht
- Pathology and Laboratory Medicine, Center for International Health Research, Brown University, Providence, RI, United States
| | | | - Rashid A. Madebe
- National Institute for Medical Research, Dar es Salaam, Tanzania
| | - Catherine Bakari
- National Institute for Medical Research, Dar es Salaam, Tanzania
| | - Dativa Pereus
- National Institute for Medical Research, Dar es Salaam, Tanzania
| | - Misago D. Seth
- National Institute for Medical Research, Dar es Salaam, Tanzania
| | | | - Ruth B. Mbwambo
- National Institute for Medical Research, Dar es Salaam, Tanzania
| | - Bronwyn MacInnis
- Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, MA, United States
- Infectious Disease and Microbiome Program, Broad Institute, Boston, MA, United States
| | | | - Issa Garimo
- National Malaria Control Programme, Dodoma, Tanzania
| | - Frank Chacky
- National Malaria Control Programme, Dodoma, Tanzania
| | | | | | | | - Ritha Njau
- World Health Organization, Country Office, Dar es Salaam, Tanzania
| | - Jane A. Cunningham
- Global Malaria Programme, World Health Organization, Headquarters, Geneva, Switzerland
| | - Samwel Lazaro
- National Malaria Control Programme, Dodoma, Tanzania
| | - Ally Mohamed
- National Malaria Control Programme, Dodoma, Tanzania
| | - Jonathan J. Juliano
- School of Medicine, University of North Carolina, Chapel Hill, NC, United States
| | - Jeffrey A. Bailey
- Pathology and Laboratory Medicine, Center for International Health Research, Brown University, Providence, RI, United States
| | - Deus S. Ishengoma
- National Institute for Medical Research, Dar es Salaam, Tanzania
- Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, MA, United States
- Faculty of Pharmaceutical Sciences, Monash University, Melbourne, VIC, Australia
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27
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RAVAOARISOA É, ANDRIANARANJAKA VHI, RAMANANTSAHALA AD, RAKOTOMANGA TA, RALINORO F, RAKOTOSAONA R, RANDRIANARIVO RH, RAKOTO DAD, JEANNODA V, RATSIMBASOA A. [Pcr-rflp genotyping of pfcrt and pfmdr1 in plasmodium falciparum isolates from children in Vatomandry, Madagascar]. MEDECINE TROPICALE ET SANTE INTERNATIONALE 2022; 2:mtsi.v2i2.2022.198. [PMID: 35919251 PMCID: PMC9326783 DOI: 10.48327/mtsi.v2i2.2022.198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Accepted: 05/17/2022] [Indexed: 11/14/2022]
Abstract
Background Malaria is a parasitic disease caused by a hematozoan of the genus Plasmodium. Early diagnosis followed by effective treatment is one of the keys to control this disease. In Madagascar, after more than 60 years of use for the treatment of uncomplicated malaria, chloroquine (CQ) was abandoned in favor of artesunate + amodiaquine (ASAQ) combination because of high prevalence of CQ treatment failure. Surveillance based on the assessment of therapeutic efficacy and genetic markers of resistance to antimalarials is therefore essential in order to detect the emergence of potentially resistant parasites as early as possible. In this context, our study aimed to genotype the Plasmodium falciparum chloroquine resistance transporter gene or Pfcrt and Plasmodium falciparum multidrug resistance gene 1 or Pfmdr1 in isolates collected from children in the district of Vatomandry. Methods A total of 142 P. falciparum isolates collected during active case detection of malaria in children under 15 years old, between February and March of 2016 and 2017 in Vatomandry district, were analyzed. Pfcrt (K76T codon) and Pfmdr1 (N86Y codon) genotyping was carried out by polymerase chain reaction followed by enzymatic digestion (restriction fragment length polymorphism) or PCR-RFLP. Results The successful rates of amplification of Pfcrt and Pfmdr1 genes were low, around 27% and 39% respectively. The prevalence of isolates carrying the mutant Pfcrt K76T codon and the mutant Pfmdr1 N86Y codon was 2.6% [95% confidence interval (95% CI): 0.1 - 15.0%] and 36% [95% CI: 23.7 - 49.7%] respectively. Conclusion Despite the limited number of samples analyzed, our study highlighted the circulation of isolates carrying both the mutant Pfcrt K76T and Pfmdr1 N86Y alleles. Although the prevalence of mutations in Pfcrt and Pfmdr1 genes that we observed was low, other studies should be carried out in order to follow the evolution of these markers in time and space. The use of more sensitive methods will better characterize P. falciparum strains circulating in Madagascar. Artesunate-amodiaquine is used as a first-line treatment for uncomplicated malaria in the country; it is also crucial to monitor the other codons, i.e. 184 and 1246 of the Pfmdr1 gene, implicated in the resistance of P. falciparum to amodiaquine in Africa.
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Affiliation(s)
- Élisabeth RAVAOARISOA
- Université d'Antananarivo Faculté des sciences, Mention Biochimie fondamentale et appliquée, Madagascar,Programme national de lutte contre le paludisme, Ministère de la Santé publique, Antananarivo, Madagascar,*
| | - Voahangy Hanitriniaina Isabelle ANDRIANARANJAKA
- Université d'Antananarivo Faculté des sciences, Mention Biochimie fondamentale et appliquée, Madagascar,Programme national de lutte contre le paludisme, Ministère de la Santé publique, Antananarivo, Madagascar
| | - Aina David RAMANANTSAHALA
- Université d'Antananarivo Faculté des sciences, Mention Biochimie fondamentale et appliquée, Madagascar
| | - Tovonahary Angelo RAKOTOMANGA
- Université d'Antananarivo Faculté des sciences, Mention Biochimie fondamentale et appliquée, Madagascar,Programme national de lutte contre le paludisme, Ministère de la Santé publique, Antananarivo, Madagascar
| | - Fanomezantsoa RALINORO
- Université d'Antananarivo Faculté des sciences, Mention Biochimie fondamentale et appliquée, Madagascar,Programme national de lutte contre le paludisme, Ministère de la Santé publique, Antananarivo, Madagascar
| | | | | | | | - Victor JEANNODA
- Université d'Antananarivo Faculté des sciences, Mention Biochimie fondamentale et appliquée, Madagascar
| | - Arsène RATSIMBASOA
- Université d'Antananarivo Faculté des sciences, Mention Biochimie fondamentale et appliquée, Madagascar,Faculté de médecine, Université de Fianarantsoa, Madagascar
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28
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Ukawuba I, Shaman J. Inference and dynamic simulation of malaria using a simple climate-driven entomological model of malaria transmission. PLoS Comput Biol 2022; 18:e1010161. [PMID: 35679241 PMCID: PMC9182318 DOI: 10.1371/journal.pcbi.1010161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 05/02/2022] [Indexed: 12/02/2022] Open
Abstract
Given the crucial role of climate in malaria transmission, many mechanistic models of malaria represent vector biology and the parasite lifecycle as functions of climate variables in order to accurately capture malaria transmission dynamics. Lower dimension mechanistic models that utilize implicit vector dynamics have relied on indirect climate modulation of transmission processes, which compromises investigation of the ecological role played by climate in malaria transmission. In this study, we develop an implicit process-based malaria model with direct climate-mediated modulation of transmission pressure borne through the Entomological Inoculation Rate (EIR). The EIR, a measure of the number of infectious bites per person per unit time, includes the effects of vector dynamics, resulting from mosquito development, survivorship, feeding activity and parasite development, all of which are moderated by climate. We combine this EIR-model framework, which is driven by rainfall and temperature, with Bayesian inference methods, and evaluate the model’s ability to simulate local transmission across 42 regions in Rwanda over four years. Our findings indicate that the biologically-motivated, EIR-model framework is capable of accurately simulating seasonal malaria dynamics and capturing of some of the inter-annual variation in malaria incidence. However, the model unsurprisingly failed to reproduce large declines in malaria transmission during 2018 and 2019 due to elevated anti-malaria measures, which were not accounted for in the model structure. The climate-driven transmission model also captured regional variation in malaria incidence across Rwanda’s diverse climate, while identifying key entomological and epidemiological parameters important to seasonal malaria dynamics. In general, this new model construct advances the capabilities of implicitly-forced lower dimension dynamical malaria models by leveraging climate drivers of malaria ecology and transmission. Climate plays a fundamental and complex role in malaria transmission, by acting on multiple aspects of mosquito ecology and parasite transmissibility. However, to express malaria transmission pressure, malaria models with implicit vector dynamics have relied on indirect predictors of vector ecology, such as temporal seasonality or interpolations of rainfall/temperature, instead of entomological processes directly informed by ambient conditions. This approach obscures the specific influence of environmental conditions on relevant vector and parasite ecology, as well as meaningful interpretation of climate variability within these models. Here, we demonstrate that both interpretability and ecological effect from climate can be instantiated in lower dimension dynamical models through representation of transmission pressures via a climate-driven Entomological Inoculation Rate (EIR). This process-based model framework is driven by local rainfall and temperature, which regulate multiple aspects of the EIR, namely mosquito density, host-seeking activity, and parasite infectivity. Our results indicate that the climate-driven model construct is able to reproduce regional and local malaria transmission at seasonal and inter-annual time scales, while enabling identification of key entomological determinants of transmission.
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Affiliation(s)
- Israel Ukawuba
- Columbia University, Mailman School of Public Health, New York, New York, United States of America
- * E-mail:
| | - Jeffrey Shaman
- Columbia University, Mailman School of Public Health, New York, New York, United States of America
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29
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Mooney JP, DonVito SM, Jahateh M, Bittaye H, Bottomley C, D'Alessandro U, Riley EM. Dry season prevalence of Plasmodium falciparum in asymptomatic gambian children, with a comparative evaluation of diagnostic methods. Malar J 2022; 21:171. [PMID: 35672850 PMCID: PMC9172138 DOI: 10.1186/s12936-022-04184-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 05/10/2022] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND Subclinical infection with Plasmodium falciparum remains highly prevalent, yet diagnosing these often low-density infections remains a challenge. Infections can be subpatent, falling below the limit of detection for conventional thick-film microscopy and rapid diagnostic testing (RDT). In this study, the prevalence of subclinical P. falciparum infections in school-aged children was characterised at the start of the dry season in the Upper River Region of The Gambia in 2017/2018, with a goal to also compare the utility of different diagnostic tools. METHODS In a cross-sectional survey of children living in 29 villages on the south bank of the Gambia river (median age of 10 years), matched microscopy, rapid diagnostic test (RDT, detecting histidine-rich protein 2) and polymerase chain reaction (PCR, targeting either 18S rRNA or var gene acidic terminal sequence) were used to determine the prevalence of patent and subpatent infections and to compare the performance of the different diagnostic methods. RESULTS The prevalence of var gene acidic terminal sequence (varATS) qPCR-detectable infections was 10.2% (141/1381) with a median density of 3.12 parasites/µL. Malaria prevalence was highly heterogeneous across the region, ranging from < 1% to ~ 40% prevalence in different village clusters. Compared to varATS, 18S rRNA PCR detected fewer low-density infections, with an assay sensitivity of 50% and specificity of 98.8%. Parasite prevalence in the cohort was 2.9% by microscopy and 1.5% by RDT. Compared to varATS qPCR, microscopy and RDT had sensitivities of 11.5% and 9.2%, respectively, although both methods were highly specific (> 98%). Samples that were positive by all three tests (varATS qPCR, RDT and microscopy) had significantly higher parasite densities (median = 1705 parasites/µL) than samples that were positive by varATS qPCR only (median = 2.4 parasites/µL). CONCLUSIONS The majority of subclinical malaria infections in school-aged children were of extremely low parasite density and detectable only by ultra-sensitive PCR analysis. Understanding the duration of these low density infections, their physiological impact and their contribution to sustained parasite transmission is necessary to inform malaria elimination strategies.
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Affiliation(s)
- Jason P Mooney
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Ashworth Laboratories, Kings Buildings, Charlotte Auerbach Rd, Edinburgh, EH9 3FL, UK.
| | - Sophia M DonVito
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Ashworth Laboratories, Kings Buildings, Charlotte Auerbach Rd, Edinburgh, EH9 3FL, UK
| | - Maimuna Jahateh
- Medical Research Council Unit in The Gambia at the London School of Hygiene and Tropical Medicine, Fajara, The Gambia
| | - Haddy Bittaye
- Medical Research Council Unit in The Gambia at the London School of Hygiene and Tropical Medicine, Fajara, The Gambia
| | - Christian Bottomley
- Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, UK
| | - Umberto D'Alessandro
- Medical Research Council Unit in The Gambia at the London School of Hygiene and Tropical Medicine, Fajara, The Gambia
| | - Eleanor M Riley
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Ashworth Laboratories, Kings Buildings, Charlotte Auerbach Rd, Edinburgh, EH9 3FL, UK
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30
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Rek J, Blanken SL, Okoth J, Ayo D, Onyige I, Musasizi E, Ramjith J, Andolina C, Lanke K, Arinaitwe E, Olwoch P, Collins KA, Kamya MR, Dorsey G, Drakeley C, Staedke SG, Bousema T, Conrad MD. Asymptomatic School-Aged Children Are Important Drivers of Malaria Transmission in a High Endemicity Setting in Uganda. J Infect Dis 2022; 226:708-713. [PMID: 35578987 PMCID: PMC9441202 DOI: 10.1093/infdis/jiac169] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 05/06/2022] [Indexed: 12/24/2022] Open
Abstract
Achieving malaria elimination requires a better understanding of the transmissibility of human infections in different transmission settings. This study aimed to characterize the human infectious reservoir in a high endemicity setting in eastern Uganda, using gametocyte quantification and mosquito feeding assays. In asymptomatic infections, gametocyte densities were positively associated with the proportion of infected mosquitoes (β = 1.60; 95% CI, 1.32-1.92; P < .0001). Combining transmissibility and abundance in the population, symptomatic and asymptomatic infections were estimated to contribute to 5.3% and 94.7% of the infectious reservoir, respectively. School-aged children (5-15 years old) contributed to 50.4% of transmission events and were important drivers of malaria transmission.
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Affiliation(s)
| | | | - Joseph Okoth
- Infectious Diseases Research Collaboration, Kampala, Uganda
| | - Daniel Ayo
- Infectious Diseases Research Collaboration, Kampala, Uganda
| | - Ismail Onyige
- Infectious Diseases Research Collaboration, Kampala, Uganda
| | - Eric Musasizi
- Infectious Diseases Research Collaboration, Kampala, Uganda
| | - Jordache Ramjith
- Department for Health Evidence, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Chiara Andolina
- Department of Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Kjerstin Lanke
- Department of Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | | | - Peter Olwoch
- Infectious Diseases Research Collaboration, Kampala, Uganda
| | - Katharine A Collins
- Department of Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - Moses R Kamya
- Department of Medicine, Makerere University College of Health Sciences, Kampala, Uganda
| | - Grant Dorsey
- Department of Medicine, San Francisco General Hospital, University of California, San Francisco, USA
| | - Chris Drakeley
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Sarah G Staedke
- Department of Clinical Research, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Teun Bousema
- Correspondence: Teun Bousema, PhD, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands ()
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Malaria and Helminthic Co-Infection during Pregnancy in Sub-Saharan Africa: A Systematic Review and Meta-Analysis. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 19:ijerph19095444. [PMID: 35564842 PMCID: PMC9101176 DOI: 10.3390/ijerph19095444] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/13/2022] [Revised: 04/25/2022] [Accepted: 04/26/2022] [Indexed: 12/22/2022]
Abstract
Malaria and helminthic co-infection during pregnancy causes fetomaternal haemorrhage and foetal growth retardation. This study determined the pooled burden of pregnancy malaria and helminthic co-infection in sub-Saharan Africa. CINAHL, EMBASE, Google Scholar, Scopus, PubMed, and Web of Science databases were used to retrieve data from the literature, without restricting language and publication year. The Joanna Briggs Institute’s critical appraisal tool for prevalence studies was used for quality assessment. STATA Version 14.0 was used to conduct the meta-analysis. The I2 statistics and Egger’s test were used to test heterogeneity and publication bias. The random-effects model was used to estimate the pooled prevalence at a 95% confidence interval (CI). The review protocol has been registered in PROSPERO, with the number CRD42019144812. In total, 24 studies (n = 14,087 participants) were identified in this study. The pooled analysis revealed that 20% of pregnant women were co-infected by malaria and helminths in sub-Saharan Africa. The pooled prevalence of malaria and helminths were 33% and 35%, respectively. The most prevalent helminths were Hookworm (48%), Ascaris lumbricoides (37%), and Trichuris trichiura (15%). Significantly higher malaria and helminthic co-infection during pregnancy were observed. Health systems in sub-Saharan Africa must implement home-grown innovative solutions to underpin context-specific policies for the early initiation of effective intermittent preventive therapy.
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Henry JM, Carter A, Smith DL. Infection age as a predictor of epidemiological metrics for malaria. Malar J 2022; 21:117. [PMID: 35392918 PMCID: PMC8991475 DOI: 10.1186/s12936-022-04134-5] [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: 07/23/2021] [Accepted: 03/22/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Accurate estimation of the burden of Plasmodium falciparum is essential for strategic planning for control and elimination. Due in part to the extreme heterogeneity in malaria exposure, immunity, other causes of disease, direct measurements of fever and disease attributable to malaria can be difficult. This can make a comparison of epidemiological metrics both within and between populations hard to interpret. An essential part of untangling this is an understanding of the complex time-course of malaria infections. METHODS Historic data from malariatherapy infections, in which individuals were intentionally infected with malaria parasites, were reexamined in aggregate. In this analysis, the age of each infection was examined as a potential predictor describing aggregate patterns across all infections. A series of piecewise linear and generalized linear regressions were performed to highlight the infection age-dependent patterns in both parasitaemia and gametocytaemia, and from parasitaemia and gametocytaemia to fever and transmission probabilities, respectively. RESULTS The observed duration of untreated patent infection was 130 days. As infections progressed, the fraction of infections subpatent by microscopy was seen to increase steadily. The time-averaged malaria infections had three distinct phases in parasitaemia: a growth phase for the first 6 days of patency, a rapid decline from day 6 to day 18, and a slowly declining chronic phase for the remaining duration of the infection. During the growth phase, parasite densities increased sharply to a peak. Densities sharply decline for a short period of time after the peak. During the chronic phase, infections declined steadily as infections age. gametocytaemia was strongly correlated with lagged asexual parasitaemia. Fever rates and transmission efficiency were strongly correlated with parasitaemia and gametocytaemia. The comparison between raw data and prediction from the age of infection has good qualitative agreement across all quantities of interest for predicting averaged effects. CONCLUSION The age of infection was established as a potentially useful covariate for malaria epidemiology. Infection age can be estimated given a history of exposure, and accounting for exposure history may potentially provide a new way to estimate malaria-attributable fever rates, transmission efficiency, and patent fraction in immunologically naïve individuals such as children and people in low-transmission regions. These data were collected from American adults with neurosyphilis, so there are reasons to be cautious about extending the quantitative results reported here to general populations in malaria-endemic regions. Understanding how immune responses modify these statistical relationships given past exposure is key for being able to apply these results more broadly.
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Affiliation(s)
- John M Henry
- College of the Environment, University of Washington, 1492 NE Boat St., 98105, Seattle, USA. .,Institute for Health Metrics and Evaluation, University of Washington, 3980 15th Ave. NE, 98195, Seattle, USA.
| | - Austin Carter
- Institute for Health Metrics and Evaluation, University of Washington, 3980 15th Ave. NE, 98195, Seattle, USA
| | - David L Smith
- Institute for Health Metrics and Evaluation, University of Washington, 3980 15th Ave. NE, 98195, Seattle, USA
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Mpina M, Stabler TC, Schindler T, Raso J, Deal A, Acuche Pupu L, Nyakarungu E, Del Carmen Ovono Davis M, Urbano V, Mtoro A, Hamad A, Lopez MSA, Pasialo B, Eyang MAO, Rivas MR, Falla CC, García GA, Momo JC, Chuquiyauri R, Saverino E, Preston Church LW, Kim Lee Sim B, Manguire B, Tanner M, Maas C, Abdulla S, Billingsley PF, Hoffman SL, Jongo S, Richie TL, Daubenberger CA. Diagnostic performance and comparison of ultrasensitive and conventional rapid diagnostic test, thick blood smear and quantitative PCR for detection of low-density Plasmodium falciparum infections during a controlled human malaria infection study in Equatorial Guinea. Malar J 2022; 21:99. [PMID: 35331251 PMCID: PMC8943516 DOI: 10.1186/s12936-022-04103-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Accepted: 02/23/2022] [Indexed: 12/02/2022] Open
Abstract
Background Progress towards malaria elimination has stagnated, partly because infections persisting at low parasite densities comprise a large reservoir contributing to ongoing malaria transmission and are difficult to detect. This study compared the performance of an ultrasensitive rapid diagnostic test (uRDT) designed to detect low density infections to a conventional RDT (cRDT), expert microscopy using Giemsa-stained thick blood smears (TBS), and quantitative polymerase chain reaction (qPCR) during a controlled human malaria infection (CHMI) study conducted in malaria exposed adults (NCT03590340). Methods Blood samples were collected from healthy Equatoguineans aged 18–35 years beginning on day 8 after CHMI with 3.2 × 103 cryopreserved, infectious Plasmodium falciparum sporozoites (PfSPZ Challenge, strain NF54) administered by direct venous inoculation. qPCR (18s ribosomal DNA), uRDT (Alere™ Malaria Ag P.f.), cRDT [Carestart Malaria Pf/PAN (PfHRP2/pLDH)], and TBS were performed daily until the volunteer became TBS positive and treatment was administered. qPCR was the reference for the presence of Plasmodium falciparum parasites. Results 279 samples were collected from 24 participants; 123 were positive by qPCR. TBS detected 24/123 (19.5% sensitivity [95% CI 13.1–27.8%]), uRDT 21/123 (17.1% sensitivity [95% CI 11.1–25.1%]), cRDT 10/123 (8.1% sensitivity [95% CI 4.2–14.8%]); all were 100% specific and did not detect any positive samples not detected by qPCR. TBS and uRDT were more sensitive than cRDT (TBS vs. cRDT p = 0.015; uRDT vs. cRDT p = 0.053), detecting parasitaemias as low as 3.7 parasites/µL (p/µL) (TBS and uRDT) compared to 5.6 p/µL (cRDT) based on TBS density measurements. TBS, uRDT and cRDT did not detect any of the 70/123 samples positive by qPCR below 5.86 p/µL, the qPCR density corresponding to 3.7 p/µL by TBS. The median prepatent periods in days (ranges) were 14.5 (10–20), 18.0 (15–28), 18.0 (15–20) and 18.0 (16–24) for qPCR, TBS, uRDT and cRDT, respectively; qPCR detected parasitaemia significantly earlier (3.5 days) than the other tests. Conclusions TBS and uRDT had similar sensitivities, both were more sensitive than cRDT, and neither matched qPCR for detecting low density parasitaemia. uRDT could be considered an alternative to TBS in selected applications, such as CHMI or field diagnosis, where qualitative, dichotomous results for malaria infection might be sufficient. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-022-04103-y.
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Affiliation(s)
- Maxmillian Mpina
- Swiss Tropical and Public Health Institute, Basel, Switzerland. .,University of Basel, Basel, Switzerland. .,Ifakara Health Institute, Ifakara, Tanzania.
| | - Thomas C Stabler
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Tobias Schindler
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Jose Raso
- Medical Care Development International, Malabo, Equatorial Guinea.,Equatorial Guinea Ministry of Health and Social Welfare, Malabo, Equatorial Guinea
| | - Anna Deal
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | | | - Elizabeth Nyakarungu
- Ifakara Health Institute, Ifakara, Tanzania.,Medical Care Development International, Malabo, Equatorial Guinea
| | | | - Vicente Urbano
- Medical Care Development International, Malabo, Equatorial Guinea.,Equatorial Guinea Ministry of Health and Social Welfare, Malabo, Equatorial Guinea
| | - Ali Mtoro
- Ifakara Health Institute, Ifakara, Tanzania.,Medical Care Development International, Malabo, Equatorial Guinea
| | - Ali Hamad
- Ifakara Health Institute, Ifakara, Tanzania.,Medical Care Development International, Malabo, Equatorial Guinea
| | - Maria Silvia A Lopez
- Medical Care Development International, Malabo, Equatorial Guinea.,Equatorial Guinea Ministry of Health and Social Welfare, Malabo, Equatorial Guinea
| | - Beltran Pasialo
- Medical Care Development International, Malabo, Equatorial Guinea.,Equatorial Guinea Ministry of Health and Social Welfare, Malabo, Equatorial Guinea
| | - Marta Alene Owono Eyang
- Medical Care Development International, Malabo, Equatorial Guinea.,Equatorial Guinea Ministry of Health and Social Welfare, Malabo, Equatorial Guinea
| | - Matilde Riloha Rivas
- Equatorial Guinea Ministry of Health and Social Welfare, Malabo, Equatorial Guinea
| | | | | | - Juan Carlos Momo
- Medical Care Development International, Malabo, Equatorial Guinea.,Equatorial Guinea Ministry of Health and Social Welfare, Malabo, Equatorial Guinea
| | - Raul Chuquiyauri
- Medical Care Development International, Malabo, Equatorial Guinea.,Sanaria Inc., 9800 Medical Center Drive, Rockville, MD, 20850, USA
| | | | | | - B Kim Lee Sim
- Sanaria Inc., 9800 Medical Center Drive, Rockville, MD, 20850, USA
| | | | - Marcel Tanner
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Carl Maas
- Marathon EG production Ltd., Houston, USA
| | | | | | | | - Said Jongo
- Ifakara Health Institute, Ifakara, Tanzania.,Medical Care Development International, Malabo, Equatorial Guinea
| | - Thomas L Richie
- Sanaria Inc., 9800 Medical Center Drive, Rockville, MD, 20850, USA
| | - Claudia A Daubenberger
- Swiss Tropical and Public Health Institute, Basel, Switzerland. .,University of Basel, Basel, Switzerland.
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Tenfold difference in DNA recovery rate: systematic comparison of whole blood vs. dried blood spot sample collection for malaria molecular surveillance. Malar J 2022; 21:88. [PMID: 35292038 PMCID: PMC8922754 DOI: 10.1186/s12936-022-04122-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Accepted: 03/07/2022] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Molecular and genomic surveillance is becoming increasingly used to track malaria control and elimination efforts. Blood samples can be collected as whole blood and stored at - 20 °C until DNA extraction, or as dried blood spots (DBS), circumventing the need for a cold chain. Despite the wide use of either method, systematic comparisons of how the method of blood sample preservation affects the limit of detection (LOD) of molecular diagnosis and the proportion of DNA recovered for downstream applications are lacking. METHODS Extractions based on spin columns, magnetic beads, Tween-Chelex, and direct PCR without prior extraction were compared for whole blood and dried blood spots (DBS) using dilution series of Plasmodium falciparum culture samples. Extracted DNA was quantified by qPCR and droplet digital PCR (ddPCR). RESULTS DNA recovery was 5- to 10-fold higher for whole blood compared to DBS, resulting in a 2- to 3-fold lower LOD for both extraction methods compared to DBS. For whole blood, a magnetic bead-based method resulted in a DNA recovery rate of 88-98% when extracting from whole blood compared to 17-33% for a spin-column based method. For extractions from DBS, the magnetic bead-based method resulted in 8-20% DNA recovery, while the spin-column based method resulted in only 2% DNA recovery. The Tween-Chelex method was superior to other methods with 15-21% DNA recovery, and even more sensitive than extractions from whole blood samples. The direct PCR method was found to have the lowest LOD overall for both, whole blood and DBS. CONCLUSIONS Pronounced differences in LOD and DNA yield need to be considered when comparing prevalence estimates based on molecular methods and when selecting sampling protocols for other molecular surveillance applications.
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Oo MC, Phongluxa K, Oo WH, Kounnavong S, Xayyavong S, Louangphaxay C, Htike W, Cutts JC, Thu KM, Hkawng GN, Fowkes FJI. Perspectives of health and community stakeholders on community-delivered models of malaria elimination in Lao People’s Democratic Republic: A qualitative study. PLoS One 2022; 17:e0264399. [PMID: 35271594 PMCID: PMC8912149 DOI: 10.1371/journal.pone.0264399] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 02/10/2022] [Indexed: 11/22/2022] Open
Abstract
In the Lao People’s Democratic Republic (Lao PDR), village health volunteers play an important role in providing health services including those to reduce the burden of malaria. Over the last two decades, the volunteer network has expanded to bring malaria services closer to communities and contributed to the reduction of malaria cases. However, as malaria test positivity rates decreased, many volunteers have lost motivation to continue providing routine malaria services, and other services they provide may not reflect growing healthcare demands for common diseases in the community. This study explored the perspectives, knowledge and inputs of key health stakeholders and community members in southern Lao PDR on community-delivered models in order to refine the volunteer model in the context of Lao PDR’s primary health care sector and malaria elimination goals. Semi-structured interviews with multi-level health stakeholders, participatory workshops with community leaders, and focus group discussions with community members and current village health volunteers were conducted. Deductive followed by inductive thematic analysis was used to explore and categorise stakeholders’ perspectives on community-delivered models for malaria elimination. Both stakeholders and community members agreed that village health volunteers are essential providers of malaria services in rural communities. Apart from malaria, community members identified dengue, diarrhoea, influenza, skin infections and tuberculosis as priorities (in descending order of importance) and requested community-based primary health care for these diseases. Stakeholders and community members suggested integrating prevention, diagnosis, and treatment services for the five priority diseases into the current malaria volunteer model. A divergence was identified between community members’ expectations of health services and the services currently provided by village health volunteers. Stakeholders proposed an integrated model of healthcare to meet the needs of the community and help to maintain volunteers’ motivation and the long-term sustainability of the role. An evidence-based, integrated community-delivered model of healthcare should be developed to balance the needs of both community members and stakeholders, with consideration of available resources and current health policies in Lao PDR.
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Affiliation(s)
- May Chan Oo
- Health Security Program, Burnet Institute Myanmar, Yangon, Myanmar
- * E-mail: (MCO); (WHO)
| | | | - Win Han Oo
- Health Security Program, Burnet Institute Myanmar, Yangon, Myanmar
- Disease Elimination Program, Burnet Institute, Victoria, Australia
- * E-mail: (MCO); (WHO)
| | | | - Syda Xayyavong
- Lao Tropical and Public Health Institute, Vientiane, Lao PDR
| | | | - Win Htike
- Health Security Program, Burnet Institute Myanmar, Yangon, Myanmar
| | - Julia C. Cutts
- Disease Elimination Program, Burnet Institute, Victoria, Australia
| | - Kaung Myat Thu
- Health Security Program, Burnet Institute Myanmar, Yangon, Myanmar
| | - Galau Naw Hkawng
- Health Security Program, Burnet Institute Myanmar, Yangon, Myanmar
| | - Freya J. I. Fowkes
- Disease Elimination Program, Burnet Institute, Victoria, Australia
- Melbourne School of Population and Global Health, University of Melbourne, Victoria, Australia
- Department of Epidemiology and Preventive Medicine, Monash University, Victoria, Australia
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Leonard CM, Assefa A, McCaffery JN, Herman C, Plucinski M, Sime H, Mohammed H, Kebede A, Solomon H, Haile M, Murphy M, Hwang J, Rogier E. Investigation of Plasmodium falciparum pfhrp2 and pfhrp3 gene deletions and performance of a rapid diagnostic test for identifying asymptomatic malaria infection in northern Ethiopia, 2015. Malar J 2022; 21:70. [PMID: 35246151 PMCID: PMC8895513 DOI: 10.1186/s12936-022-04097-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Accepted: 02/18/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Rapid diagnostic tests (RDTs) are widely used for malaria diagnosis of both symptomatic and asymptomatic infections. Although RDTs are a reliable and practical diagnostic tool, the sensitivity of histidine-rich protein 2 (HRP2)-based RDTs can be reduced if pfhrp2 or pfhrp3 (pfhrp2/3) gene deletions exist in the Plasmodium falciparum parasite population. This study evaluated dried blood spot (DBS) samples collected from a national household survey to investigate the presence of pfhrp2/3 deletions and the performance of the RDT used in the cross-sectional survey in a low transmission setting. METHODS The 2015 Ethiopia Malaria Indicator Survey tested household members by RDT and collected DBS samples. DBS (n = 2648) from three regions in northern Ethiopia were tested by multiplex bead-based antigen detection assay after completion of the survey. The multiplex assay detected pan-Plasmodium lactate dehydrogenase (LDH), pAldolase, and HRP2 antigens in samples. Samples suspected for pfhrp2/3 gene deletions (pLDH and/or pAldolase positive but low or absent HRP2) were further investigated by molecular assays for gene deletions. Antigen results were also compared to each individual's RDT results. Dose-response logistic regression models were fit to estimate RDT level of detection (LOD) antigen concentrations at which 50, 75, 90, and 95% of the RDTs returned a positive result during this survey. RESULTS Out of 2,648 samples assayed, 29 were positive for pLDH or pAldolase antigens but low or absent for HRP2 signal, and 15 of these samples (51.7%) were successfully genotyped for pfhrp2/3. Of these 15 P. falciparum infections, eight showed single deletions in pfhrp3, one showed a single pfhrp2 deletion, and six were pfhrp2/3 double-deletions. Six pfhrp2 deletions were observed in Tigray and one in Amhara. Twenty-five were positive for HRP2 by the survey RDT while the more sensitive bead assay detected 30 HRP2-positive samples. A lower concentration of HRP2 antigen generated a positive test result by RDT compared to pLDH (95% LOD: 16.9 ng/mL vs. 319.2 ng/mL, respectively). CONCLUSIONS There is evidence of dual pfhrp2/3 gene deletions in the Tigray and Amhara regions of Ethiopia in 2015. As the prevalence of malaria was very low (< 2%), it is difficult to make strong conclusions on RDT performance, but these results challenge the utility of biomarkers in household surveys in very low transmission settings.
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Affiliation(s)
- Colleen M Leonard
- Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, GA, 30329, USA.,Oak Ridge Institute for Science and Education, US. Department of Energy, Oak Ridge, TN, 37831, USA
| | - Ashenafi Assefa
- Ethiopian Public Health Institute, Addis Ababa, Ethiopia.,Infectious Disease Ecology and Epidemiology Laboratory, University of North Carolina at Chapel Hill, Chapel Hill, USA
| | - Jessica N McCaffery
- Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, GA, 30329, USA.,Oak Ridge Institute for Science and Education, US. Department of Energy, Oak Ridge, TN, 37831, USA
| | - Camelia Herman
- Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, GA, 30329, USA
| | - Mateusz Plucinski
- Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, GA, 30329, USA.,U.S. President's Malaria Initiative, Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, GA, 30329, USA
| | - Heven Sime
- Ethiopian Public Health Institute, Addis Ababa, Ethiopia
| | | | - Amha Kebede
- African Society for Laboratory Medicine, Addis Ababa, Ethiopia
| | - Hiwot Solomon
- Ethiopian Federal Ministry of Health, Addis Ababa, Ethiopia
| | | | - Matt Murphy
- Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, GA, 30329, USA.,U.S. President's Malaria Initiative, Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, GA, 30329, USA
| | - Jimee Hwang
- Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, GA, 30329, USA.,U.S. President's Malaria Initiative, Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, GA, 30329, USA
| | - Eric Rogier
- Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, GA, 30329, USA.
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Agbana HB, Rogier E, Lo A, Abukari Z, Jones S, Gyan B, Aidoo M, Amoah LE. Detecting asymptomatic carriage of Plasmodium falciparum in southern Ghana: utility of molecular and serological diagnostic tools. Malar J 2022; 21:57. [PMID: 35183178 PMCID: PMC8858553 DOI: 10.1186/s12936-022-04078-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Accepted: 02/06/2022] [Indexed: 12/04/2022] Open
Abstract
Background Asymptomatic malaria infections can serve as potential reservoirs for malaria transmission. The density of parasites contained in these infections range from microscopic to submicroscopic densities, making the accurate detection of asymptomatic parasite carriage highly dependent on the sensitivity of the tools used for the diagnosis. This study sought to evaluate the sensitivities of a variety of molecular and serological diagnostic tools at determining the prevalence of asymptomatic Plasmodium falciparum parasite infections in two communities with varying malaria parasite prevalence. Methods Whole blood was collected from 194 afebrile participants aged between 6 and 70 years old living in a high (Obom) and a low (Asutsuare) malaria transmission setting of Ghana. Thick and thin blood smears, HRP2 based malaria rapid diagnostic test (RDT) and filter paper dried blood spots (DBS) were prepared from each blood sample. Genomic DNA was extracted from the remaining blood and used in Plasmodium specific photo-induced electron transfer polymerase chain reaction (PET-PCR) and Nested PCR, whilst the HRP2 antigen content of the DBS was estimated using a bead immunoassay. A comparison of malaria parasite prevalence as determined by each method was performed. Results Parasite prevalence in the high transmission site of Obom was estimated at 71.4%, 61.9%, 60%, 37.8% and 19.1% by Nested PCR, the HRP2 bead assay, PET-PCR, HRP2-RDT and microscopy respectively. Parasite prevalence in the low transmission site of Asutsuare was estimated at 50.1%, 11.2%, 5.6%, 0% and 2.2% by Nested PCR, the HRP2 bead assay, PET-PCR, RDT and microscopy, respectively. The diagnostic performance of Nested PCR, PET-PCR and the HRP2 bead assay was similar in Obom but in Asutsuare, Nested PCR had a significantly higher sensitivity than PET-PCR and the HRP2 bead assay, which had similar sensitivity. Conclusions Nested PCR exhibited the highest sensitivity by identifying the highest prevalence of asymptomatic P. falciparum in both the high and low parasite prevalence settings. However, parasite prevalence estimated by the HRP2 bead assay and PET-PCR had the highest level of inter-rater agreement relative to all the other tools tested and have the advantage of requiring fewer processing steps relative to Nested PCR and producing quantitative results. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-022-04078-w.
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Chen S, Gao Y, Fan Y, Guo S, Zhou J, Liu T, Xu W. The Dynamic Change of Immune Responses Between Acute and Recurrence Stages of Rodent Malaria Infection. Front Microbiol 2022; 13:844975. [PMID: 35250958 PMCID: PMC8891988 DOI: 10.3389/fmicb.2022.844975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Accepted: 01/31/2022] [Indexed: 11/13/2022] Open
Abstract
Malaria infections are persistent as frequent recrudescence of the disease may occur following the acute infection stage, but the different immune responses that control the acute and recrudescence stages are still largely unknown. Using single-cell RNA sequencing (scRNA-seq), we showed that the number of Th1 and plasma cells in the spleen was significantly reduced during the recurrence stage compared to the acute stage of Plasmodium chabaudi chabaudi AS (P. chabaudi) infection. Additionally, the ability of both CD4+ T cell responses and B cells to control P. chabaudi recurrence was significantly reduced compared to their roles in the control of acute infection. In contrast, the number of innate immune cells, including red pulp macrophages (RPMs), gamma delta (γδ) T cells, and Dendritic cells (DCs) were significantly increased during the recurrence stage and showed to be critical for P. chabaudi infection recurrence control. Thus, our data strongly suggest the complementary role of innate immune responses in controlling malaria recrudescence when adaptive immune responses are suppressed. These findings shed new light on the development of immune interventions against malaria.
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Affiliation(s)
- Suilin Chen
- Department of Pathogenic Biology, Army Medical University (Third Military Medical University), Chongqing, China
- Key Laboratory of Extreme Environmental Medicine, Ministry of Education of China, Chongqing, China
| | - Yuanli Gao
- Department of Pathogenic Biology, Army Medical University (Third Military Medical University), Chongqing, China
- Key Laboratory of Extreme Environmental Medicine, Ministry of Education of China, Chongqing, China
| | - Yongling Fan
- Department of Pathogenic Biology, Army Medical University (Third Military Medical University), Chongqing, China
- Key Laboratory of Extreme Environmental Medicine, Ministry of Education of China, Chongqing, China
| | - Shuai Guo
- Department of Pathogenic Biology, Army Medical University (Third Military Medical University), Chongqing, China
- Key Laboratory of Extreme Environmental Medicine, Ministry of Education of China, Chongqing, China
| | - Jian Zhou
- Institute of Immunology, Army Medical University (Third Military Medical University), Chongqing, China
- *Correspondence: Jian Zhou,
| | - Taiping Liu
- Department of Pathogenic Biology, Army Medical University (Third Military Medical University), Chongqing, China
- Key Laboratory of Extreme Environmental Medicine, Ministry of Education of China, Chongqing, China
- Taiping Liu,
| | - Wenyue Xu
- Department of Pathogenic Biology, Army Medical University (Third Military Medical University), Chongqing, China
- Key Laboratory of Extreme Environmental Medicine, Ministry of Education of China, Chongqing, China
- Wenyue Xu,
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Slater HC, Ding XC, Knudson S, Bridges DJ, Moonga H, Saad NJ, De Smet M, Bennett A, Dittrich S, Slutsker L, Domingo GJ. Performance and utility of more highly sensitive malaria rapid diagnostic tests. BMC Infect Dis 2022; 22:121. [PMID: 35120441 PMCID: PMC8815208 DOI: 10.1186/s12879-021-07023-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 12/30/2021] [Indexed: 12/03/2022] Open
Abstract
Background A new more highly sensitive rapid diagnostic test (HS-RDT) for Plasmodium falciparum malaria (Alere™/Abbott Malaria Ag P.f RDT [05FK140], now called NxTek™ Eliminate Malaria Ag Pf) was launched in 2017. The test has already been used in many research studies in a wide range of geographies and use cases. Methods In this study, we collate all published and available unpublished studies that use the HS-RDT and assess its performance in (i) prevalence surveys, (ii) clinical diagnosis, (iii) screening pregnant women, and (iv) active case detection. Two individual-level data sets from asymptomatic populations are used to fit logistic regression models to estimate the probability of HS-RDT positivity based on histidine-rich protein 2 (HRP2) concentration and parasite density. The performance of the HS-RDT in prevalence surveys is estimated by calculating the sensitivity and positive proportion in comparison to polymerase chain reaction (PCR) and conventional malaria RDTs. Results We find that across 18 studies, in prevalence surveys, the mean sensitivity of the HS-RDT is estimated to be 56.1% (95% confidence interval [CI] 46.9–65.4%) compared to 44.3% (95% CI 32.6–56.0%) for a conventional RDT (co-RDT) when using nucleic acid amplification techniques as the reference standard. In studies where prevalence was estimated using both the HS-RDT and a co-RDT, we found that prevalence was on average 46% higher using a HS-RDT compared to a co-RDT. For use in clinical diagnosis and screening pregnant women, the HS-RDT was not significantly more sensitive than a co-RDT. Conclusions Overall, the evidence presented here suggests that the HS-RDT is more sensitive in asymptomatic populations and could provide a marginal improvement in clinical diagnosis and screening pregnant women. Although the HS-RDT has limited temperature stability and shelf-life claims compared to co-RDTs, there is no evidence to suggest, given this test has the same cost as current RDTs, it would have any negative impacts in terms of malaria misdiagnosis if it were widely used in all four population groups explored here. Supplementary Information The online version contains supplementary material available at 10.1186/s12879-021-07023-5.
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Affiliation(s)
- Hannah C Slater
- Diagnostics Program, PATH, Seattle, WA, USA. .,Malaria and Neglected Tropical Diseases, PATH, Seattle, WA, USA.
| | - Xavier C Ding
- Foundation for Innovative New Diagnostics, Geneva, Switzerland
| | | | - Daniel J Bridges
- PATH Malaria Control and Elimination Partnership in Africa (MACEPA), Lusaka, Zambia
| | - Hawela Moonga
- National Malaria Elimination Centre, Zambia Ministry of Health, Lusaka, Zambia
| | - Neil J Saad
- Médecins Sans Frontières, Phnom Penh, Preah Vihear, Cambodia
| | | | - Adam Bennett
- Malaria and Neglected Tropical Diseases, PATH, Seattle, WA, USA.,Malaria Elimination Initiative, Global Health Group, University of California San Francisco, San Francisco, CA, USA
| | - Sabine Dittrich
- Foundation for Innovative New Diagnostics, Geneva, Switzerland
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Enriquez GF, Bua J, Orozco MM, Macchiaverna NP, Otegui JAA, Argibay HD, Fernández MDP, Gürtler RE, Cardinal MV. Over-dispersed Trypanosoma cruzi parasite load in sylvatic and domestic mammals and humans from northeastern Argentina. Parasit Vectors 2022; 15:37. [PMID: 35073983 PMCID: PMC8785451 DOI: 10.1186/s13071-022-05152-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 01/03/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The distribution of parasite load across hosts may modify the transmission dynamics of infectious diseases. Chagas disease is caused by a multi-host protozoan, Trypanosoma cruzi, but the association between host parasitemia and infectiousness to the vector has not been studied in sylvatic mammalian hosts. We quantified T. cruzi parasite load in sylvatic mammals, modeled the association of the parasite load with infectiousness to the vector and compared these results with previous ones for local domestic hosts. METHODS The bloodstream parasite load in each of 28 naturally infected sylvatic mammals from six species captured in northern Argentina was assessed by quantitative PCR, and its association with infectiousness to the triatomine Triatoma infestans was evaluated, as determined by natural or artificial xenodiagnosis. These results were compared with our previous results for 88 humans, 70 dogs and 13 cats, and the degree of parasite over-dispersion was quantified and non-linear models fitted to data on host infectiousness and bloodstream parasite load. RESULTS The parasite loads of Didelphis albiventris (white-eared opossum) and Dasypus novemcinctus (nine-banded armadillo) were directly and significantly associated with infectiousness of the host and were up to 190-fold higher than those in domestic hosts. Parasite load was aggregated across host species, as measured by the negative binomial parameter, k, and found to be substantially higher in white-eared opossums, cats, dogs and nine-banded armadillos (range: k = 0.3-0.5) than in humans (k = 5.1). The distribution of bloodstream parasite load closely followed the "80-20 rule" in every host species examined. However, the 20% of human hosts, domestic mammals or sylvatic mammals exhibiting the highest parasite load accounted for 49, 25 and 33% of the infected triatomines, respectively. CONCLUSIONS Our results support the use of bloodstream parasite load as a proxy of reservoir host competence and individual transmissibility. The over-dispersed distribution of T. cruzi bloodstream load implies the existence of a fraction of highly infectious hosts that could be targeted to improve vector-borne transmission control efforts toward interruption transmission. Combined strategies that decrease the parasitemia and/or host-vector contact with these hosts would disproportionally contribute to T. cruzi transmission control.
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Affiliation(s)
- Gustavo Fabián Enriquez
- Laboratorio de Eco-Epidemiología, Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Intendente Güiraldes 2160, Piso 2, Ciudad Universitaria, Buenos Aires, Argentina.
- Instituto de Ecología, Genética y Evolución (IEGEBA), CONICET-Universidad de Buenos Aires, Buenos Aires, Argentina.
| | - Jacqueline Bua
- Instituto Nacional de Parasitología Dr. M. Fatala Chabén, Administración Nacional de Laboratorios e Institutos de Salud Dr. C.G. Malbrán, Buenos Aires, Argentina
| | - María Marcela Orozco
- Instituto de Ecología, Genética y Evolución (IEGEBA), CONICET-Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Natalia Paula Macchiaverna
- Laboratorio de Eco-Epidemiología, Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Intendente Güiraldes 2160, Piso 2, Ciudad Universitaria, Buenos Aires, Argentina
- Instituto de Ecología, Genética y Evolución (IEGEBA), CONICET-Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Julián Antonio Alvarado Otegui
- Laboratorio de Eco-Epidemiología, Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Intendente Güiraldes 2160, Piso 2, Ciudad Universitaria, Buenos Aires, Argentina
- Instituto de Ecología, Genética y Evolución (IEGEBA), CONICET-Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Hernán Darío Argibay
- Laboratorio de Patologia e Biologia Molecular, Instituto Gonçalo Moniz/Fiocruz Bahia, Salvador, Brazil
| | | | - Ricardo Esteban Gürtler
- Laboratorio de Eco-Epidemiología, Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Intendente Güiraldes 2160, Piso 2, Ciudad Universitaria, Buenos Aires, Argentina
- Instituto de Ecología, Genética y Evolución (IEGEBA), CONICET-Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Marta Victoria Cardinal
- Laboratorio de Eco-Epidemiología, Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Intendente Güiraldes 2160, Piso 2, Ciudad Universitaria, Buenos Aires, Argentina
- Instituto de Ecología, Genética y Evolución (IEGEBA), CONICET-Universidad de Buenos Aires, Buenos Aires, Argentina
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Ferreira MU, Corder RM, Johansen IC, Kattenberg JH, Moreno M, Rosas-Aguirre A, Ladeia-Andrade S, Conn JE, Llanos-Cuentas A, Gamboa D, Rosanas-Urgell A, Vinetz JM. Relative contribution of low-density and asymptomatic infections to Plasmodium vivax transmission in the Amazon: pooled analysis of individual participant data from population-based cross-sectional surveys. LANCET REGIONAL HEALTH. AMERICAS 2022; 9:100169. [PMID: 35663000 PMCID: PMC9161731 DOI: 10.1016/j.lana.2021.100169] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Background Low-density and asymptomatic Plasmodium vivax infections remain largely undetected and untreated and may contribute significantly to malaria transmission in the Amazon. Methods We analysed individual participant data from population-based surveys that measured P vivax prevalence by microscopy and polymerase chain reaction (PCR) between 2002 and 2015 and modelled the relationship between parasite density and infectiousness to vectors using membrane feeding assay data. We estimated the proportion of sub-patent (i.e., missed by microscopy) and asymptomatic P vivax infections and examined how parasite density relates to clinical manifestations and mosquito infection in Amazonian settings. Findings We pooled 24,986 observations from six sites in Brazil and Peru. P vivax was detected in 6·8% and 2·1% of them by PCR and microscopy, respectively. 58·5% to 92·6% of P vivax infections were asymptomatic and 61·2% to 96·3% were sub-patent across study sites. P vivax density thresholds associated with clinical symptoms were one order of magnitude higher in children than in adults. We estimate that sub-patent parasite carriers are minimally infectious and contribute 12·7% to 24·9% of the community-wide P vivax transmission, while asymptomatic carriers are the source of 28·2% to 79·2% of mosquito infections. Interpretation Asymptomatic P vivax carriers constitute a vast infectious reservoir that, if targeted by malaria elimination strategies, could substantially reduce malaria transmission in the Amazon. Infected children may remain asymptomatic despite high parasite densities that elicit clinical manifestations in adults. Funding US National Institutes of Health, Fundação de Amparo à Pesquisa do Estado de São Paulo, and Belgium Development Cooperation.
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Affiliation(s)
- Marcelo U. Ferreira
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil,Global Health and Tropical Medicine, Institute of Hygiene and Tropical Medicine, Nova University of Lisbon, Lisbon, Portugal,Corresponding author: Prof Marcelo U. Ferreira, Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, 05508-900 São Paulo, SP, Brazil.
| | - Rodrigo M. Corder
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Igor C. Johansen
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | | | - Marta Moreno
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, UK
| | - Angel Rosas-Aguirre
- Institute of Health and Society, Université catholique de Louvain, Brussels, Belgium
| | - Simone Ladeia-Andrade
- Laboratory of Parasitic Diseases, Oswaldo Cruz Institute, Fiocruz, Rio de Janeiro, Brazil
| | - Jan E. Conn
- Department of Biomedical Sciences, School of Public Health, University at Albany, State University of New York, Albany, NY, USA,Wadsworth Center, New York State Department of Health, Albany, NY, USA
| | - Alejandro Llanos-Cuentas
- Instituto de Medicina Tropical "Alexander von Humboldt", Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Dionicia Gamboa
- Instituto de Medicina Tropical "Alexander von Humboldt", Universidad Peruana Cayetano Heredia, Lima, Peru,Laboratorio ICEMR-Amazonia, Laboratorios de Investigación y Desarrollo, Departamento de Ciencias Celulares y Moleculares, Facultad de Ciencias y Filosofia, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Anna Rosanas-Urgell
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Joseph M. Vinetz
- Laboratorio ICEMR-Amazonia, Laboratorios de Investigación y Desarrollo, Departamento de Ciencias Celulares y Moleculares, Facultad de Ciencias y Filosofia, Universidad Peruana Cayetano Heredia, Lima, Peru,Section of Infectious Diseases, Department of Internal Medicine, Yale School of Medicine, New Haven, CT, USA
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Mooney JP, DonVito SM, Jahateh M, Bittaye H, Keith M, Galloway LJ, Ndow M, Cunnington AJ, D'Alessandro U, Bottomley C, Riley EM. 'Bouncing Back' From Subclinical Malaria: Inflammation and Erythrocytosis After Resolution of P. falciparum Infection in Gambian Children. Front Immunol 2022; 13:780525. [PMID: 35154104 PMCID: PMC8831762 DOI: 10.3389/fimmu.2022.780525] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Accepted: 01/03/2022] [Indexed: 11/13/2022] Open
Abstract
Recent malaria is associated with an increased risk of systemic bacterial infection. The aetiology of this association is unclear but malaria-related haemolysis may be one contributory factor. To characterise the physiological consequences of persistent and recently resolved malaria infections and associated haemolysis, 1650 healthy Gambian children aged 8-15 years were screened for P. falciparum infection (by 18sRNA PCR) and/or anaemia (by haematocrit) at the end of the annual malaria transmission season (t1). P. falciparum-infected children and children with moderate or severe anaemia (haemoglobin concentration < 11g/dl) were age matched to healthy, uninfected, non-anaemic controls and screened again 2 months later (t2). Persistently infected children (PCR positive at t1 and t2) had stable parasite burdens and did not differ significantly haematologically or in terms of proinflammatory markers from healthy, uninfected children. However, among persistently infected children, IL-10 concentrations were positively correlated with parasite density suggesting a tolerogenic response to persistent infection. By contrast, children who naturally resolved their infections (positive at t1 and negative at t2) exhibited mild erythrocytosis and concentrations of pro-inflammatory markers were raised compared to other groups of children. These findings shed light on a 'resetting' and potential overshoot of the homeostatic haematological response following resolution of malaria infection. Interestingly, the majority of parameters tested were highly heterogeneous in uninfected children, suggesting that some may be harbouring cryptic malaria or other infections.
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Affiliation(s)
- Jason P Mooney
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Sophia M DonVito
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Maimuna Jahateh
- Medical Research Council Unit in The Gambia at the London School of Hygiene and Tropical Medicine, Fajara, Gambia
| | - Haddy Bittaye
- Medical Research Council Unit in The Gambia at the London School of Hygiene and Tropical Medicine, Fajara, Gambia
| | - Marianne Keith
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Lauren J Galloway
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Mortala Ndow
- Medical Research Council Unit in The Gambia at the London School of Hygiene and Tropical Medicine, Fajara, Gambia
| | - Aubrey J Cunnington
- Section of Paediatric Infectious Disease, Department of Infectious Disease, Imperial College London, London, United Kingdom
| | - Umberto D'Alessandro
- Medical Research Council Unit in The Gambia at the London School of Hygiene and Tropical Medicine, Fajara, Gambia
| | - Christian Bottomley
- Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Eleanor M Riley
- Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
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Fogang B, Biabi MF, Megnekou R, Maloba FM, Essangui E, Donkeu C, Cheteug G, Kapen M, Keumoe R, Kemleu S, Nsango S, Eboumbou C, Lamb TJ, Ayong L. High Prevalence of Asymptomatic Malarial Anemia and Association with Early Conversion from Asymptomatic to Symptomatic Infection in a Plasmodium falciparum Hyperendemic Setting in Cameroon. Am J Trop Med Hyg 2022; 106:293-302. [PMID: 34724628 PMCID: PMC8733519 DOI: 10.4269/ajtmh.21-0316] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 05/30/2021] [Indexed: 01/03/2023] Open
Abstract
Asymptomatic malarial parasitemia is highly prevalent in Plasmodium falciparum endemic areas and often associated with increased prevalence of mild to moderate anemia. The aim of this study was to assess the prevalence of anemia during asymptomatic malaria parasitemia and its interplay with persistent infection in highly exposed individuals. A household-based longitudinal survey was undertaken in a malaria hyperendemic area in Cameroon using multiplex nested polymerase chain reaction to detect plasmodial infections. Residents with P. falciparum asymptomatic parasitemia were monitored over a 3-week period with the aid of structured questionnaires and weekly measurements of axillary temperatures. Of the 353 individuals included (median age: 26 years, range 2-86 years, male/female sex ratio 0.9), 328 (92.9%) were positive for malaria parasitemia of whom 266 (81.1%) were asymptomatic carriers. The prevalence of anemia in the study population was 38.6%, of which 69.2% were asymptomatic. Multivariate analyses identified high parasitemia (> 327 parasites/µL) and female gender as associated risk factors of asymptomatic malarial anemia in the population. Furthermore, risk analyses revealed female gender and anemia at the time of enrolment as key predictors of early development of febrile illness (< 3 weeks post enrolment) among the asymptomatic individuals. Together, the data reveal an extremely high prevalence of asymptomatic malaria parasitemia and anemia in the study area, unveiling for the first time the association of asymptomatic malarial anemia with early clinical conversion from asymptomatic to symptomatic infection. Furthermore, these findings underscore the negative impact of asymptomatic malaria parasitemia on individual health, necessitating the development of appropriate control and preventive measures.
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Affiliation(s)
- Balotin Fogang
- Molecular Parasitology Laboratory, Centre Pasteur du Cameroun, Yaounde, Cameroon;,Department of Animal Biology and Physiology of the University of Yaoundé I, Yaounde, Cameroon
| | - Marie Florence Biabi
- Molecular Parasitology Laboratory, Centre Pasteur du Cameroun, Yaounde, Cameroon;,Department of Biochemistry, University of Douala, Douala, Cameroon
| | - Rosette Megnekou
- Department of Animal Biology and Physiology of the University of Yaoundé I, Yaounde, Cameroon
| | - Franklin M. Maloba
- Molecular Parasitology Laboratory, Centre Pasteur du Cameroun, Yaounde, Cameroon;,Department of Pathology, University of Utah, Salt Lake City, Utah
| | - Estelle Essangui
- Molecular Parasitology Laboratory, Centre Pasteur du Cameroun, Yaounde, Cameroon
| | - Christiane Donkeu
- Molecular Parasitology Laboratory, Centre Pasteur du Cameroun, Yaounde, Cameroon;,Department of Animal Biology and Physiology of the University of Yaoundé I, Yaounde, Cameroon
| | - Glwadys Cheteug
- Molecular Parasitology Laboratory, Centre Pasteur du Cameroun, Yaounde, Cameroon;,Department of Medical Laboratory Sciences, University of Buea, Buea, Cameroon
| | - Marie Kapen
- Molecular Parasitology Laboratory, Centre Pasteur du Cameroun, Yaounde, Cameroon
| | - Rodrigue Keumoe
- Molecular Parasitology Laboratory, Centre Pasteur du Cameroun, Yaounde, Cameroon
| | - Sylvie Kemleu
- Molecular Parasitology Laboratory, Centre Pasteur du Cameroun, Yaounde, Cameroon;,Department of Medical Laboratory Sciences, University of Buea, Buea, Cameroon
| | - Sandrine Nsango
- Molecular Parasitology Laboratory, Centre Pasteur du Cameroun, Yaounde, Cameroon
| | - Carole Eboumbou
- Molecular Parasitology Laboratory, Centre Pasteur du Cameroun, Yaounde, Cameroon
| | - Tracey J. Lamb
- Department of Pathology, University of Utah, Salt Lake City, Utah
| | - Lawrence Ayong
- Molecular Parasitology Laboratory, Centre Pasteur du Cameroun, Yaounde, Cameroon;,Address correspondence to Lawrence Ayong, Molecular Parasitology Laboratory, Centre Pasteur du Cameroun, BP 1274 Yaounde, Cameroon. E-mail:
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Bridges DJ, Miller JM, Chalwe V, Moonga H, Hamainza B, Steketee RW, Mambwe B, Mulube C, Wu L, Tetteh KKA, Drakeley C, Chishimba S, Mwenda M, Silumbe K, Larsen DA. Reactive focal drug administration associated with decreased malaria transmission in an elimination setting: Serological evidence from the cluster-randomized CoRE study. PLOS GLOBAL PUBLIC HEALTH 2022; 2:e0001295. [PMID: 36962857 PMCID: PMC10021141 DOI: 10.1371/journal.pgph.0001295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Accepted: 10/26/2022] [Indexed: 12/12/2022]
Abstract
Efforts to eliminate malaria transmission need evidence-based strategies. However, accurately assessing end-game malaria elimination strategies is challenging due to the low level of transmission and the rarity of infections. We hypothesised that presumptively treating individuals during reactive case detection (RCD) would reduce transmission and that serology would more sensitively detect this change over standard approaches. We conducted a cluster randomised control trial (NCT02654912) of presumptive reactive focal drug administration (RFDA-intervention) compared to the standard of care, reactive focal test and treat (RFTAT-control) in Southern Province, Zambia-an area of low seasonal transmission (overall incidence of ~3 per 1,000). We measured routine malaria incidence from health facilities as well as PCR parasite prevalence / antimalarial seroprevalence in an endline cross-sectional population survey. No significant difference was identified from routine incidence data and endline prevalence by polymerase chain reaction (PCR) had insufficient numbers of malaria infections (i.e., 16 infections among 6,276 children) to assess the intervention. Comparing long-term serological markers, we found a 19% (95% CI = 4-32%) reduction in seropositivity for the RFDA intervention using a difference in differences approach incorporating serological positivity and age. We also found a 37% (95% CI = 2-59%) reduction in seropositivity to short-term serological markers in a post-only comparison. These serological analyses provide compelling evidence that RFDA both has an impact on malaria transmission and is an appropriate end-game malaria elimination strategy. Furthermore, serology provides a more sensitive approach to measure changes in transmission that other approaches miss, particularly in very low transmission settings. Trial Registration: Registered at www.clinicaltrials.gov (NCT02654912, 13/1/2016).
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Affiliation(s)
- Daniel J Bridges
- PATH-Malaria Control and Elimination Partnership in Africa (MACEPA), National Malaria Elimination Centre, Chainama Hospital College Grounds, Lusaka, Zambia
| | - John M Miller
- PATH-Malaria Control and Elimination Partnership in Africa (MACEPA), National Malaria Elimination Centre, Chainama Hospital College Grounds, Lusaka, Zambia
| | - Victor Chalwe
- National Health Research Authority, Paediatric Centre of Excellence, University Teaching Hospital, Lusaka, Zambia
| | - Hawela Moonga
- National Malaria Elimination Centre, Zambia Ministry of Health, Chainama Hospital, Lusaka, Zambia
| | - Busiku Hamainza
- National Malaria Elimination Centre, Zambia Ministry of Health, Chainama Hospital, Lusaka, Zambia
| | - Richard W Steketee
- PATH-Malaria Control and Elimination Partnership in Africa (MACEPA), Seattle, Washington, United States of America
| | - Brenda Mambwe
- PATH-Malaria Control and Elimination Partnership in Africa (MACEPA), National Malaria Elimination Centre, Chainama Hospital College Grounds, Lusaka, Zambia
| | - Conceptor Mulube
- PATH-Malaria Control and Elimination Partnership in Africa (MACEPA), National Malaria Elimination Centre, Chainama Hospital College Grounds, Lusaka, Zambia
| | - Lindsey Wu
- London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Kevin K A Tetteh
- London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Chris Drakeley
- London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Sandra Chishimba
- PATH-Malaria Control and Elimination Partnership in Africa (MACEPA), National Malaria Elimination Centre, Chainama Hospital College Grounds, Lusaka, Zambia
| | - Mulenga Mwenda
- PATH-Malaria Control and Elimination Partnership in Africa (MACEPA), National Malaria Elimination Centre, Chainama Hospital College Grounds, Lusaka, Zambia
| | - Kafula Silumbe
- PATH-Malaria Control and Elimination Partnership in Africa (MACEPA), National Malaria Elimination Centre, Chainama Hospital College Grounds, Lusaka, Zambia
| | - David A Larsen
- Syracuse University Department of Public Health, Syracuse, New York, United States of America
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Ochwedo KO, Omondi CJ, Magomere EO, Olumeh JO, Debrah I, Onyango SA, Orondo PW, Ondeto BM, Atieli HE, Ogolla SO, Githure J, Otieno ACA, Githeko AK, Kazura JW, Mukabana WR, Guiyan Y. Hyper-prevalence of submicroscopic Plasmodium falciparum infections in a rural area of western Kenya with declining malaria cases. Malar J 2021; 20:472. [PMID: 34930283 PMCID: PMC8685826 DOI: 10.1186/s12936-021-04012-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2021] [Accepted: 12/07/2021] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND The gold standard for diagnosing Plasmodium falciparum infection is microscopic examination of Giemsa-stained peripheral blood smears. The effectiveness of this procedure for infection surveillance and malaria control may be limited by a relatively high parasitaemia detection threshold. Persons with microscopically undetectable infections may go untreated, contributing to ongoing transmission to mosquito vectors. The purpose of this study was to determine the magnitude and determinants of undiagnosed submicroscopic P. falciparum infections in a rural area of western Kenya. METHODS A health facility-based survey was conducted, and 367 patients seeking treatment for symptoms consistent with uncomplicated malaria in Homa Bay County were enrolled. The frequency of submicroscopic P. falciparum infection was measured by comparing the prevalence of infection based on light microscopic inspection of thick blood smears versus real-time polymerase chain reaction (RT-PCR) targeting P. falciparum 18S rRNA gene. Long-lasting insecticidal net (LLIN) use, participation in nocturnal outdoor activities, and gender were considered as potential determinants of submicroscopic infections. RESULTS Microscopic inspection of blood smears was positive for asexual P. falciparum parasites in 14.7% (54/367) of cases. All of these samples were confirmed by RT-PCR. 35.8% (112/313) of blood smear negative cases were positive by RT-PCR, i.e., submicroscopic infection, resulting in an overall prevalence by RT-PCR alone of 45.2% compared to 14.7% for blood smear alone. Females had a higher prevalence of submicroscopic infections (35.6% or 72 out of 202 individuals, 95% CI 28.9-42.3) compared to males (24.2%, 40 of 165 individuals, 95% CI 17.6-30.8). The risk of submicroscopic infections in LLIN users was about half that of non-LLIN users (OR = 0.59). There was no difference in the prevalence of submicroscopic infections of study participants who were active in nocturnal outdoor activities versus those who were not active (OR = 0.91). Patients who participated in nocturnal outdoor activities and use LLINs while indoors had a slightly higher risk of submicroscopic infection than those who did not use LLINs (OR = 1.48). CONCLUSION Microscopic inspection of blood smears from persons with malaria symptoms for asexual stage P. falciparum should be supplemented by more sensitive diagnostic tests in order to reduce ongoing transmission of P. falciparum parasites to local mosquito vectors.
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Affiliation(s)
- Kevin O. Ochwedo
- Department of Biology, Faculty of Science and Technology, University of Nairobi, Nairobi, Kenya
- Sub-Saharan Africa International Centre for Excellence in Malaria Research, Homa Bay, Kenya
| | - Collince J. Omondi
- Department of Biology, Faculty of Science and Technology, University of Nairobi, Nairobi, Kenya
- Sub-Saharan Africa International Centre for Excellence in Malaria Research, Homa Bay, Kenya
| | - Edwin O. Magomere
- Department of Biochemistry and Molecular Biology, Egerton University, Njoro, Kenya
| | - Julius O. Olumeh
- Department of Biology, Faculty of Science and Technology, University of Nairobi, Nairobi, Kenya
- Sub-Saharan Africa International Centre for Excellence in Malaria Research, Homa Bay, Kenya
| | - Isaiah Debrah
- West Africa Centre for Cell Biology of Infectious Pathogen, Department of Biochemistry, Cell and Molecular Biology, University of Ghana, Accra, Ghana
| | - Shirley A. Onyango
- Sub-Saharan Africa International Centre for Excellence in Malaria Research, Homa Bay, Kenya
| | - Pauline W. Orondo
- Sub-Saharan Africa International Centre for Excellence in Malaria Research, Homa Bay, Kenya
| | - Benyl M. Ondeto
- Department of Biology, Faculty of Science and Technology, University of Nairobi, Nairobi, Kenya
- Sub-Saharan Africa International Centre for Excellence in Malaria Research, Homa Bay, Kenya
| | - Harrysone E. Atieli
- Sub-Saharan Africa International Centre for Excellence in Malaria Research, Homa Bay, Kenya
| | - Sidney O. Ogolla
- Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya
| | - John Githure
- Sub-Saharan Africa International Centre for Excellence in Malaria Research, Homa Bay, Kenya
| | - Antony C. A. Otieno
- Department of Biology, Faculty of Science and Technology, University of Nairobi, Nairobi, Kenya
| | - Andrew K. Githeko
- Sub-Saharan Africa International Centre for Excellence in Malaria Research, Homa Bay, Kenya
- Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya
| | - James W. Kazura
- Centre for Global Health and Diseases, Case Western Reserve University, Cleveland, OH USA
| | - Wolfgang R. Mukabana
- Department of Biology, Faculty of Science and Technology, University of Nairobi, Nairobi, Kenya
- Sub-Saharan Africa International Centre for Excellence in Malaria Research, Homa Bay, Kenya
| | - Yan Guiyan
- Program in Public Health, College of Health Sciences, University of California, Irvine, USA
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46
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Ayanful-Torgby R, Sarpong E, Abagna HB, Donu D, Obboh E, Mensah BA, Adjah J, Williamson KC, Amoah LE. Persistent Plasmodium falciparum infections enhance transmission-reducing immunity development. Sci Rep 2021; 11:21380. [PMID: 34725428 PMCID: PMC8560775 DOI: 10.1038/s41598-021-00973-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Accepted: 10/21/2021] [Indexed: 11/09/2022] Open
Abstract
Subclinical infections that serve as reservoir populations to drive transmission remain a hurdle to malaria control. Data on infection dynamics in a geographical area is required to strategically design and implement malaria interventions. In a longitudinal cohort, we monitored Plasmodium falciparum infection prevalence and persistence, and anti-parasite immunity to gametocyte and asexual antigens for 10 weeks. Of the 100 participants, only 11 were never infected, whilst 16 had persistent infections detected by reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR), and one participant had microscopic parasites at all visits. Over 70% of the participants were infected three or more times, and submicroscopic gametocyte prevalence was high, ≥ 48% of the parasite carriers. Naturally induced responses against recombinant Pfs48/45.6C, Pfs230proC, and EBA175RIII-V antigens were not associated with either infection status or gametocyte carriage, but the antigen-specific IgG titers inversely correlated with parasite and gametocyte densities consistent with partial immunity. Longitudinal analysis of gametocyte diversity indicated at least four distinct clones circulated throughout the study period. The high prevalence of children infected with distinct gametocyte clones coupled with marked variation in infection status at the individual level suggests ongoing transmission and should be targeted in malaria control programs.
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Affiliation(s)
- Ruth Ayanful-Torgby
- Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana.
| | | | - Hamza B Abagna
- Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana
| | - Dickson Donu
- Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana
| | | | - Benedicta A Mensah
- Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana
| | - Joshua Adjah
- Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana
| | - Kim C Williamson
- Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - Linda E Amoah
- Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana.
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47
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Asymptomatic Plasmodium vivax malaria in the Brazilian Amazon: Submicroscopic parasitemic blood infects Nyssorhynchus darlingi. PLoS Negl Trop Dis 2021; 15:e0009077. [PMID: 34714821 PMCID: PMC8555776 DOI: 10.1371/journal.pntd.0009077] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 08/30/2021] [Indexed: 11/19/2022] Open
Abstract
Individuals with asymptomatic infection due to Plasmodium vivax are posited to be important reservoirs of malaria transmission in endemic regions. Here we studied a cohort of P. vivax malaria patients in a suburban area in the Brazilian Amazon. Overall 1,120 individuals were screened for P. vivax infection and 108 (9.6%) had parasitemia detected by qPCR but not by microscopy. Asymptomatic individuals had higher levels of antibodies against P. vivax and similar hematological and biochemical parameters compared to uninfected controls. Blood from asymptomatic individuals with very low parasitemia transmitted P. vivax to the main local vector, Nyssorhynchus darlingi. Lower mosquito infectivity rates were observed when blood from asymptomatic individuals was used in the membrane feeding assay. While blood from symptomatic patients infected 43.4% (199/458) of the mosquitoes, blood from asymptomatic infected 2.5% (43/1,719). However, several asymptomatic individuals maintained parasitemia for several weeks indicating their potential role as an infectious reservoir. These results suggest that asymptomatic individuals are an important source of malaria parasites and Science and Technology for Vaccines granted by Conselho Nacional de may contribute to the transmission of P. vivax in low-endemicity areas of malaria.
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48
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Quang HH, Chavchich M, Trinh NTM, Manh ND, Edstein MD, Martin NJ, Edgel KA. Cross-sectional survey of asymptomatic malaria in Dak Nong province in the Central Highlands of Vietnam for the malaria elimination roadmap. PLoS One 2021; 16:e0258580. [PMID: 34669697 PMCID: PMC8528296 DOI: 10.1371/journal.pone.0258580] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Accepted: 09/30/2021] [Indexed: 12/25/2022] Open
Abstract
Asymptomatic parasite carriers represent a “silent” infective reservoir for malaria transmission and contributes to malaria persistence. However, limited data are available on asymptomatic malaria in Vietnam. Between November 2018 and March 2019, we conducted a malaria epidemiological survey of asymptomatic people (children ≥ 10 years old and adults ≥18 years old, n = 2,809) residing in three communes in Tuy Duc district, Dak Nong province in the Central Highlands of Vietnam. Based on the national stratification of malaria risk, Dak Buk So, Dak Ngo and Quang Truc communes were classified by the National Malaria Control Programme as low, moderate and high malaria endemic areas, respectively. Using participants’ finger prick blood samples, malaria parasites were detected by one-step reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The median age (Interquartile Range) for adults and children were 35 years (26–50) and 12 years (11–14), respectively. The prevalence of asymptomatic malaria was 1.7% (22/1,328), 3.5% (31/890) and 12.2% (72/591) for participants from Dak Buk So, Dak Ngo and Quang Truc, respectively. The prevalence of asymptomatic malaria was lower in children compared to adults: 2.6% (9/352) versus 4.7% (116/2,457) (Odds Ratio 0.53, 95% Confidence Interval 0.28 to1.02). Ownership of long-lasting insecticide-treated bed nets and hammocks was 97.1%, 99.0% and 94.7% for participants in Dak Buk So, Dak Ngo and Quang Truc, respectively, however, only 66.0%, 57.3% and 42.8% of the participants reported using bed nets every night. Of the several risk factors examined, going to the forest two weeks prior to enrolment into the study and sleeping in the forest had a significant association with participants being infected with asymptomatic malaria in Quang Truc, but not in the other two communes. Knowledge of the prevalence and distribution of asymptomatic malaria will help design and evaluate future intervention strategies for malaria elimination in Vietnam.
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Affiliation(s)
- Huynh Hong Quang
- Institute of Malariology, Parasitology and Entomology, Quy Nhon, Vietnam
| | - Marina Chavchich
- Australian Defence Force Malaria and Infectious Disease Institute, Brisbane, Australia
- * E-mail:
| | | | | | - Michael D. Edstein
- Australian Defence Force Malaria and Infectious Disease Institute, Brisbane, Australia
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49
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Amoah B, McCann RS, Kabaghe AN, Mburu M, Chipeta MG, Moraga P, Gowelo S, Tizifa T, van den Berg H, Mzilahowa T, Takken W, van Vugt M, Phiri KS, Diggle PJ, Terlouw DJ, Giorgi E. Identifying Plasmodium falciparum transmission patterns through parasite prevalence and entomological inoculation rate. eLife 2021; 10:65682. [PMID: 34672946 PMCID: PMC8530514 DOI: 10.7554/elife.65682] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Accepted: 09/30/2021] [Indexed: 11/13/2022] Open
Abstract
Background Monitoring malaria transmission is a critical component of efforts to achieve targets for elimination and eradication. Two commonly monitored metrics of transmission intensity are parasite prevalence (PR) and the entomological inoculation rate (EIR). Comparing the spatial and temporal variations in the PR and EIR of a given geographical region and modelling the relationship between the two metrics may provide a fuller picture of the malaria epidemiology of the region to inform control activities. Methods Using geostatistical methods, we compare the spatial and temporal patterns of Plasmodium falciparum EIR and PR using data collected over 38 months in a rural area of Malawi. We then quantify the relationship between EIR and PR by using empirical and mechanistic statistical models. Results Hotspots identified through the EIR and PR partly overlapped during high transmission seasons but not during low transmission seasons. The estimated relationship showed a 1-month delayed effect of EIR on PR such that at lower levels of EIR, increases in EIR are associated with rapid rise in PR, whereas at higher levels of EIR, changes in EIR do not translate into notable changes in PR. Conclusions Our study emphasises the need for integrated malaria control strategies that combine vector and human host managements monitored by both entomological and parasitaemia indices. Funding This work was supported by Stichting Dioraphte grant number 13050800.
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Affiliation(s)
- Benjamin Amoah
- Centre for Health Informatics, Computing, and Statistics (CHICAS), Lancaster Medical School, Lancaster University, Lancaster, United Kingdom
| | - Robert S McCann
- Laboratory of Entomology, Wageningen University and Research, Wageningen, Netherlands.,Department of Public Health, College of Medicine, University of Malawi, Blantyre, Malawi.,Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, United States
| | - Alinune N Kabaghe
- Department of Public Health, College of Medicine, University of Malawi, Blantyre, Malawi.,Academic Medical Centre, University of Amsterdam, Amsterdam, Netherlands
| | - Monicah Mburu
- Laboratory of Entomology, Wageningen University and Research, Wageningen, Netherlands.,Department of Public Health, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Michael G Chipeta
- Department of Public Health, College of Medicine, University of Malawi, Blantyre, Malawi.,Malawi-Liverpool Wellcome Trust Research Programme, Blantyre, Malawi.,Big Data Institute, University of Oxford, Oxford, United Kingdom
| | - Paula Moraga
- Centre for Health Informatics, Computing, and Statistics (CHICAS), Lancaster Medical School, Lancaster University, Lancaster, United Kingdom.,Computer, Electrical and Mathematical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
| | - Steven Gowelo
- Laboratory of Entomology, Wageningen University and Research, Wageningen, Netherlands.,Department of Public Health, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Tinashe Tizifa
- Department of Public Health, College of Medicine, University of Malawi, Blantyre, Malawi.,Academic Medical Centre, University of Amsterdam, Amsterdam, Netherlands
| | - Henk van den Berg
- Laboratory of Entomology, Wageningen University and Research, Wageningen, Netherlands
| | - Themba Mzilahowa
- Department of Public Health, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Willem Takken
- Laboratory of Entomology, Wageningen University and Research, Wageningen, Netherlands
| | - Michele van Vugt
- Academic Medical Centre, University of Amsterdam, Amsterdam, Netherlands
| | - Kamija S Phiri
- Department of Public Health, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Peter J Diggle
- Centre for Health Informatics, Computing, and Statistics (CHICAS), Lancaster Medical School, Lancaster University, Lancaster, United Kingdom
| | - Dianne J Terlouw
- Department of Public Health, College of Medicine, University of Malawi, Blantyre, Malawi.,Malawi-Liverpool Wellcome Trust Research Programme, Blantyre, Malawi.,Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Emanuele Giorgi
- Centre for Health Informatics, Computing, and Statistics (CHICAS), Lancaster Medical School, Lancaster University, Lancaster, United Kingdom
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50
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Application of dried blood spot sample pooling strategies for Plasmodium 18S rRNA biomarker testing to facilitate identification of infected persons in large-scale epidemiological studies. Malar J 2021; 20:391. [PMID: 34620192 PMCID: PMC8499573 DOI: 10.1186/s12936-021-03907-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Accepted: 09/06/2021] [Indexed: 11/10/2022] Open
Abstract
Background Plasmodium 18S rRNA is a sensitive biomarker for detecting Plasmodium infection in human blood. Dried blood spots (DBS) are a practical sample type for malaria field studies to collect, store, and transport large quantities of blood samples for diagnostic testing. Pooled testing is a common way to reduce reagent costs and labour. This study examined performance of the Plasmodium 18S rRNA biomarker assay for DBS, improved assay sensitivity for pooled samples, and created graphical user interface (GUI) programmes for facilitating optimal pooling. Methods DBS samples of varied parasite densities from clinical specimens, Plasmodium falciparum in vitro culture, and P. falciparum Armored RNA® were tested using the Plasmodium 18S rRNA quantitative triplex reverse transcription polymerase chain reaction (qRT-PCR) assay and a simplified duplex assay. DBS sample precision, linearity, limit of detection (LoD) and stability at varied storage temperatures were evaluated. Novel GUIs were created to model two-stage hierarchy, square matrix, and three-stage hierarchy pooling strategies with samples of varying positivity rates and estimated test counts. Seventy-eight DBS samples from persons residing in endemic regions with sub-patent infections were tested in pools and deconvoluted to identify positive cases. Results Assay performance showed linearity for DBS from 4 × 107 to 5 × 102 parasites/mL with strong correlation to liquid blood samples (r2 > 0.96). There was a minor quantitative reduction in DBS rRNA copies/mL compared to liquid blood samples. Analytical sensitivity for DBS was estimated 5.3 log copies 18S rRNA/mL blood (28 estimated parasites/mL). Properly preserved DBS demonstrated minimal degradation of 18S rRNA when stored at ambient temperatures for one month. A simplified duplex qRT-PCR assay omitting the human mRNA target showed improved analytical sensitivity, 1 parasite/mL blood, and was optimized for pooling. Optimal pooling sizes varied depending on prevalence. A pilot DBS study of the two-stage hierarchy pooling scheme corroborated results previously determined by testing individual DBS. Conclusions The Plasmodium 18S rRNA biomarker assay can be applied to DBS collected in field studies. The simplified Plasmodium qRT-PCR assay and GUIs have been established to provide efficient means to test large quantities of DBS samples. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-021-03907-8.
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