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Zeno EE, Obala AA, Pence B, Freedman E, Mangeni JN, Lin JT, Abel L, Edwards JK, Gower EW, Taylor SM. Risk of Malaria Following Untreated Subpatent Plasmodium falciparum Infections: Results Over 4 Years From a Cohort in a High-Transmission Area in Western Kenya. J Infect Dis 2024; 229:969-978. [PMID: 37713614 PMCID: PMC11011184 DOI: 10.1093/infdis/jiad398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Revised: 08/30/2023] [Accepted: 09/11/2023] [Indexed: 09/17/2023] Open
Abstract
BACKGROUND People with suspected malaria may harbor Plasmodium falciparum undetected by rapid diagnostic test (RDT). The impact of these subpatent infections on the risk of developing clinical malaria is not fully understood. METHODS We analyzed subpatent P. falciparum infections using a longitudinal cohort in a high-transmission site in Kenya. Weighted Kaplan-Meier models estimated the risk difference (RD) for clinical malaria during the 60 days following a symptomatic subpatent infection. Stratum-specific estimates by age and transmission season assessed modification. RESULTS Over 54 months, we observed 1128 symptomatic RDT-negative suspected malaria episodes, of which 400 (35.5%) harbored subpatent P. falciparum. Overall, the 60-day risk of developing clinical malaria was low following all episodes (8.6% [95% confidence interval, 6.7%-10.4%]). In the low-transmission season, the risk of clinical malaria was slightly higher in those with subpatent infection, whereas the opposite was true in the high-transmission season (low-transmission season RD, 2.3% [95% confidence interval, .4%-4.2%]; high-transmission season RD, -4.8% [-9.5% to -.05%]). CONCLUSIONS The risk of developing clinical malaria among people with undetected subpatent infections is low. A slightly elevated risk in the low-transmission season may merit alternate management, but RDTs identify clinically relevant infections in the high-transmission season.
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Affiliation(s)
- Erica E Zeno
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, USA
- Division of Infectious Diseases, School of Medicine, Duke University, Durham, North Carolina, USA
| | - Andrew A Obala
- School of Medicine, College of Health Sciences, Moi University, Eldoret, Kenya
| | - Brian Pence
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, USA
| | - Elizabeth Freedman
- Division of Infectious Diseases, School of Medicine, Duke University, Durham, North Carolina, USA
| | - Judith N Mangeni
- School of Public Health, College of Health Sciences, Moi University, Eldoret, Kenya
| | - Jessica T Lin
- Division of Infectious Diseases, School of Medicine, University of North Carolina at Chapel Hill, USA
| | - Lucy Abel
- Academic Model Providing Access to Healthcare, Moi Teaching and Referral Hospital, Eldoret, Kenya
| | - Jessie K Edwards
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, USA
| | - Emily W Gower
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, USA
| | - Steve M Taylor
- Division of Infectious Diseases, School of Medicine, Duke University, Durham, North Carolina, USA
- Duke Global Health Institute, Duke University, Durham, North Carolina, USA
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Markwalter CF, Petersen JEV, Zeno EE, Sumner KM, Freedman E, Mangeni JN, Abel L, Obala AA, Prudhomme-O’Meara W, Taylor SM. Symptomatic malaria enhances protection from reinfection with homologous Plasmodium falciparum parasites. PLoS Pathog 2023; 19:e1011442. [PMID: 37307293 PMCID: PMC10289385 DOI: 10.1371/journal.ppat.1011442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 06/23/2023] [Accepted: 05/24/2023] [Indexed: 06/14/2023] Open
Abstract
A signature remains elusive of naturally-acquired immunity against Plasmodium falciparum. We identified P. falciparum in a 14-month cohort of 239 people in Kenya, genotyped at immunogenic parasite targets expressed in the pre-erythrocytic (circumsporozoite protein, CSP) and blood (apical membrane antigen 1, AMA-1) stages, and classified into epitope type based on variants in the DV10, Th2R, and Th3R epitopes in CSP and the c1L region of AMA-1. Compared to asymptomatic index infections, symptomatic malaria was associated with reduced reinfection by parasites bearing homologous CSP-Th2R (adjusted hazard ratio [aHR]:0.63; 95% CI:0.45-0.89; p = 0.008) CSP-Th3R (aHR:0.71; 95% CI:0.52-0.97; p = 0.033), and AMA-1 c1L (aHR:0.63; 95% CI:0.43-0.94; p = 0.022) epitope types. The association of symptomatic malaria with reduced hazard of homologous reinfection was strongest for rare epitope types. Symptomatic malaria provides more durable protection against reinfection with parasites bearing homologous epitope types. The phenotype represents a legible molecular epidemiologic signature of naturally-acquired immunity by which to identify new antigen targets.
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Affiliation(s)
- Christine F. Markwalter
- Duke Global Health Institute, Duke University, Durham, North Carolina, United States of America
| | - Jens E. V. Petersen
- Division of Infectious Diseases, School of Medicine, Duke University, Durham, North Carolina, United States of America
| | - Erica E. Zeno
- Division of Infectious Diseases, School of Medicine, Duke University, Durham, North Carolina, United States of America
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Kelsey M. Sumner
- Division of Infectious Diseases, School of Medicine, Duke University, Durham, North Carolina, United States of America
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Elizabeth Freedman
- Division of Infectious Diseases, School of Medicine, Duke University, Durham, North Carolina, United States of America
| | - Judith N. Mangeni
- School of Public Health, College of Health Sciences, Moi University, Eldoret, Kenya
| | - Lucy Abel
- Academic Model Providing Access to Healthcare, Moi Teaching and Referral Hospital, Eldoret, Kenya
| | - Andrew A. Obala
- School of Medicine, College of Health Sciences, Moi University, Eldoret, Kenya
| | - Wendy Prudhomme-O’Meara
- Duke Global Health Institute, Duke University, Durham, North Carolina, United States of America
- Division of Infectious Diseases, School of Medicine, Duke University, Durham, North Carolina, United States of America
- School of Public Health, College of Health Sciences, Moi University, Eldoret, Kenya
| | - Steve M. Taylor
- Duke Global Health Institute, Duke University, Durham, North Carolina, United States of America
- Division of Infectious Diseases, School of Medicine, Duke University, Durham, North Carolina, United States of America
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, North Carolina, United States of America
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Markwalter CF, Petersen JEV, Zeno EE, Sumner KM, Freedman E, Mangeni JN, Abel L, Obala AA, Prudhomme-O’Meara W, Taylor SM. Symptomatic malaria enhances protection from reinfection with homologous Plasmodium falciparum parasites. medRxiv 2023:2023.01.04.23284198. [PMID: 36711685 PMCID: PMC9882554 DOI: 10.1101/2023.01.04.23284198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
A signature remains elusive of naturally-acquired immunity against Plasmodium falciparum . We identified P. falciparum in a 14-month cohort of 239 people in Kenya, genotyped at immunogenic parasite targets expressed in the pre-erythrocytic (circumsporozoite protein, CSP) and blood (apical membrane antigen 1, AMA-1) stages, and classified into epitope type based on variants in the DV10, Th2R, and Th3R epitopes in CSP and the c1L region of AMA-1. Compared to asymptomatic index infections, symptomatic malaria was associated with a reduced reinfection by parasites bearing homologous CSP-Th2R (adjusted hazard ratio [aHR]:0.63; 95% CI:0.45-0.89; p=0.008) CSP-Th3R (aHR:0.71; 95% CI:0.52-0.97; p=0.033), and AMA-1 c1L (aHR:0.63; 95% CI:0.43-0.94; p=0.022) epitope types. The association of symptomatic malaria with reduced risk of homologous reinfection was strongest for rare epitope types. Symptomatic malaria more effectively promotes functional immune responses. The phenotype represents a legible molecular epidemiologic signature of naturally-acquired immunity by which to identify new antigen targets.
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Affiliation(s)
| | - Jens E. V. Petersen
- Division of Infectious Diseases, School of Medicine, Duke University, Durham NC USA
| | - Erica E. Zeno
- Division of Infectious Diseases, School of Medicine, Duke University, Durham NC USA,Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill NC USA
| | - Kelsey M. Sumner
- Division of Infectious Diseases, School of Medicine, Duke University, Durham NC USA,Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill NC USA
| | - Elizabeth Freedman
- Division of Infectious Diseases, School of Medicine, Duke University, Durham NC USA
| | - Judith N. Mangeni
- School of Public Health, College of Health Sciences, Moi University, Eldoret, Kenya
| | - Lucy Abel
- Academic Model Providing Access to Healthcare, Moi Teaching and Referral Hospital, Eldoret Kenya
| | - Andrew A. Obala
- School of Medicine, College of Health Sciences, Moi University, Eldoret Kenya
| | - Wendy Prudhomme-O’Meara
- Duke Global Health Institute, Duke University, Durham NC USA,Division of Infectious Diseases, School of Medicine, Duke University, Durham NC USA,School of Public Health, College of Health Sciences, Moi University, Eldoret, Kenya
| | - Steve M. Taylor
- Duke Global Health Institute, Duke University, Durham NC USA,Division of Infectious Diseases, School of Medicine, Duke University, Durham NC USA,Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill NC USA,Corresponding author: Steve M Taylor ,
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Mangeni JN, Abel L, Taylor SM, Obala A, O'Meara WP, Saran I. Experience and confidence in health technologies: evidence from malaria testing and treatment in Western Kenya. BMC Public Health 2022; 22:1689. [PMID: 36068516 PMCID: PMC9446607 DOI: 10.1186/s12889-022-14102-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Accepted: 08/29/2022] [Indexed: 11/10/2022] Open
Abstract
Background Low adoption of effective health technologies increases illness morbidity and mortality worldwide. In the case of malaria, effective tools such as malaria rapid diagnostic tests (RDTs) and artemisinin-combination therapies (ACTs) are both under-used and used inappropriately. Individuals’ confidence in RDTs and ACTs likely affects the uptake of these tools. Methods In a cohort of 36 households (280 individuals) in Western Kenya observed for 30 months starting in June 2017, we examined if experience with RDTs and ACTs changes people’s beliefs about these technologies and how those beliefs affect treatment behavior. Household members requested a free RDT from the study team any time they suspected a malaria illness, and positive RDT results were treated with a free ACT. We conducted annual, monthly, and sick visit surveys to elicit beliefs about the accuracy of malaria RDT results and the effectiveness of ACTs. Beliefs were elicited on a 5-point Likert scale from “very unlikely” to “very likely.” Results Over the study period, the percentage of survey respondents that said a hypothetical negative RDT result was “very likely” to be correct increased from approximately 55% to 75%. Controlling for initial beliefs, people who had been tested at least once with an RDT in the past year had 3.6 times higher odds (95% CI [1 1.718 7.679], P = 0.001) of saying a negative RDT was “very likely” to be correct. Confidence in testing was associated with treatment behavior: those who believed a negative RDT was “very likely” to be correct had 1.78 times higher odds (95% CI [1.079 2.934], P = 0.024) of adhering to a negative RDT result (by not taking ACTs) than those who were less certain about the accuracy of negative RDTs. Adherence to a negative test also affected subsequent beliefs: controlling for prior beliefs, those who had adhered to their previous test result had approximately twice the odds (OR = 2.19, 95% CI [1.661 2.904], P < 0.001) of saying that a hypothetical negative RDT was “very likely” to be correct compared to those who had not adhered. Conclusions Our results suggest that greater experience with RDTs can not only increase people’s confidence in their accuracy but also improve adherence to the test result. Supplementary Information The online version contains supplementary material available at 10.1186/s12889-022-14102-y.
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Affiliation(s)
- Judith N Mangeni
- School of Public Health, College of Health Sciences, Moi University, P.O BOX 512-30100, Eldoret, Kenya.
| | - Lucy Abel
- Academic Model Providing Access to Healthcare, Moi Teaching and Referral Hospital, Eldoret, Kenya
| | - Steve M Taylor
- Division of Infectious Diseases, School of Medicine, Duke University, Durham, NC, USA
| | - Andrew Obala
- School of Medicine, College of Health Sciences, Moi University, Eldoret, Kenya
| | | | - Indrani Saran
- Boston College of Social Work, McGuinn Hall 305, Newton, MA, USA
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5
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Sumner KM, Mangeni JN, Obala AA, Freedman E, Abel L, Meshnick SR, Edwards JK, Pence BW, Prudhomme-O'Meara W, Taylor SM. Impact of asymptomatic Plasmodium falciparum infection on the risk of subsequent symptomatic malaria in a longitudinal cohort in Kenya. eLife 2021; 10:e68812. [PMID: 34296998 PMCID: PMC8337072 DOI: 10.7554/elife.68812] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 07/20/2021] [Indexed: 11/13/2022] Open
Abstract
Background Asymptomatic Plasmodium falciparum infections are common in sub-Saharan Africa, but their effect on subsequent symptomaticity is incompletely understood. Methods In a 29-month cohort of 268 people in Western Kenya, we investigated the association between asymptomatic P. falciparum and subsequent symptomatic malaria with frailty Cox models. Results Compared to being uninfected, asymptomatic infections were associated with an increased 1 month likelihood of symptomatic malaria (adjusted hazard ratio [aHR]: 2.61, 95% CI: 2.05 to 3.33), and this association was modified by sex, with females (aHR: 3.71, 95% CI: 2.62 to 5.24) at higher risk for symptomaticity than males (aHR: 1.76, 95% CI: 1.24 to 2.50). This increased symptomatic malaria risk was observed for asymptomatic infections of all densities and in people of all ages. Long-term risk was attenuated but still present in children under age 5 (29-month aHR: 1.38, 95% CI: 1.05 to 1.81). Conclusions In this high-transmission setting, asymptomatic P. falciparum can be quickly followed by symptoms and may be targeted to reduce the incidence of symptomatic illness. Funding This work was supported by the National Institute of Allergy and Infectious Diseases (R21AI126024 to WPO, R01AI146849 to WPO and SMT).
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Affiliation(s)
- Kelsey M Sumner
- Department of Epidemiology, Gillings School of Global Public Health, University of North CarolinaChapel HillUnited States
- Division of Infectious Diseases, School of Medicine, Duke UniversityDurhamUnited States
| | - Judith N Mangeni
- School of Public Health, College of Health Sciences, Moi UniversityEldoretKenya
| | - Andrew A Obala
- School of Medicine, College of Health Sciences, Moi UniversityEldoretKenya
| | - Elizabeth Freedman
- Division of Infectious Diseases, School of Medicine, Duke UniversityDurhamUnited States
| | - Lucy Abel
- Academic Model Providing Access to Healthcare, Moi Teaching and Referral HospitalEldoretKenya
| | - Steven R Meshnick
- Department of Epidemiology, Gillings School of Global Public Health, University of North CarolinaChapel HillUnited States
| | - Jessie K Edwards
- Department of Epidemiology, Gillings School of Global Public Health, University of North CarolinaChapel HillUnited States
| | - Brian W Pence
- Department of Epidemiology, Gillings School of Global Public Health, University of North CarolinaChapel HillUnited States
| | - Wendy Prudhomme-O'Meara
- Division of Infectious Diseases, School of Medicine, Duke UniversityDurhamUnited States
- School of Public Health, College of Health Sciences, Moi UniversityEldoretKenya
- Duke Global Health Institute, Duke UniversityDurhamUnited States
| | - Steve M Taylor
- Department of Epidemiology, Gillings School of Global Public Health, University of North CarolinaChapel HillUnited States
- Division of Infectious Diseases, School of Medicine, Duke UniversityDurhamUnited States
- Duke Global Health Institute, Duke UniversityDurhamUnited States
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6
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Sumner KM, Freedman E, Mangeni JN, Obala AA, Abel L, Edwards JK, Emch M, Meshnick SR, Pence BW, Prudhomme-O'Meara W, Taylor SM. Exposure to diverse Plasmodium falciparum genotypes shapes the risk of symptomatic malaria in incident and persistent infections: A longitudinal molecular epidemiologic study in Kenya. Clin Infect Dis 2021; 73:1176-1184. [PMID: 33904907 DOI: 10.1093/cid/ciab357] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Indexed: 01/04/2023] Open
Abstract
BACKGROUND Repeated exposure to malaria infections could protect against symptomatic progression, as people develop adaptive immunity to infections acquired over time. METHODS We investigated how new, recurrent, and persistent Plasmodium falciparum infections were associated with the odds of developing symptomatic compared to asymptomatic malaria. Using a 14-month longitudinal cohort in Western Kenya, we used amplicon deep sequencing of two polymorphic genes (pfama1 and pfcsp) to assess overlap of parasite genotypes (represented by haplotypes) acquired within an individual's successive infections. We hypothesized infections with novel haplotypes would increase the odds of symptomatic malaria. RESULTS After excluding initial infections, we observed 534 asymptomatic and 88 symptomatic infections across 186 people. We detected 109 pfcsp haplotypes, and each infection was classified as harboring novel, recurrent or persistent haplotypes. Incident infections with only new haplotypes had higher odds of symptomatic malaria when compared to infections with only recurrent haplotypes [odds ratio (OR): 3.24, 95% confidence interval (CI): 1.20 to 8.78], but infections with both new and recurrent haplotypes [OR: 0.64, 95% CI: 0.15 to 2.65] did not. Assessing persistent infections, those with mixed (persistent with new or recurrent) haplotypes [OR: 0.77, 95% CI: 0.21 to 2.75] had no association with symptomatic malaria compared to infections with only persistent haplotypes. Results were similar for pfama1. CONCLUSIONS These results confirm that incident infections with only novel haplotypes were associated with increased odds of symptomatic malaria compared to infections with only recurrent haplotypes but this relationship was not seen when haplotypes persisted over time in consecutive infections.
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Affiliation(s)
- Kelsey M Sumner
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill NC, USA.,Division of Infectious Diseases, School of Medicine, Duke University, Durham NC, USA
| | - Elizabeth Freedman
- Division of Infectious Diseases, School of Medicine, Duke University, Durham NC, USA
| | - Judith N Mangeni
- School of Public Health, College of Health Sciences, Moi University, Eldoret, Kenya
| | - Andrew A Obala
- School of Medicine, College of Health Sciences, Moi University, Eldoret, Kenya
| | - Lucy Abel
- Academic Model Providing Access to Healthcare, Moi Teaching and Referral Hospital, Eldoret, Kenya
| | - Jessie K Edwards
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill NC, USA
| | - Michael Emch
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill NC, USA.,Department of Geography, University of North Carolina, Chapel Hill NC, USA
| | - Steven R Meshnick
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill NC, USA
| | - Brian W Pence
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill NC, USA
| | - Wendy Prudhomme-O'Meara
- Division of Infectious Diseases, School of Medicine, Duke University, Durham NC, USA.,School of Public Health, College of Health Sciences, Moi University, Eldoret, Kenya.,Duke Global Health Institute, Duke University, Durham NC, USA
| | - Steve M Taylor
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill NC, USA.,Division of Infectious Diseases, School of Medicine, Duke University, Durham NC, USA.,Duke Global Health Institute, Duke University, Durham NC, USA
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Taylor SM, Sumner KM, Freedman B, Mangeni JN, Obala AA, Prudhomme O'Meara W. Direct Estimation of Sensitivity of Plasmodium falciparum Rapid Diagnostic Test for Active Case Detection in a High-Transmission Community Setting. Am J Trop Med Hyg 2020; 101:1416-1423. [PMID: 31674301 DOI: 10.4269/ajtmh.19-0558] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Community-based active case detection of malaria parasites with conventional rapid diagnostic tests (cRDTs) is a strategy used most commonly in low-transmission settings. We estimated the sensitivity of this approach in a high-transmission setting in Western Kenya. We tested 3,547 members of 912 households identified in 2013-2014 by index children with (case) and without (control) cRDT-positive malaria. All were tested for Plasmodium falciparum with both a cRDT targeting histidine-rich protein 2 and with an ultrasensitive real-time polymerase chain reaction (PCR). We computed cRDT sensitivity against PCR as the referent, compared prevalence between participant types, and estimated cRDT detectability as a function of PCR-estimated parasite density. Parasite prevalence was 22.9% by cRDTs and 61.5% by PCR. Compared with children aged < 5 years or adults aged > 15 years, geometric mean parasite densities (95% CI) were highest in school-age children aged 5-15 years (8.4 p/uL; 6.6-10.6). The overall sensitivity of cRDT was 36%; among asymptomatic household members, cRDT sensitivity was 25.5% and lowest in adults aged > 15 years (15.8%). When modeled as a function of parasite density, relative to school-age children, the probability of cRDT positivity was reduced in both children aged < 5 years (odds ratio [OR] 0.48; 95% CI: 0.34-0.69) and in adults aged > 15 years (OR: 0.35; 95% CI: 0.27-0.47). An HRP2-detecting cRDT had poor sensitivity for active P. falciparum case detection in asymptomatic community members, and sensitivity was lowest in highly prevalent low-density infections and in adults. Future studies can model the incremental effects of high-sensitivity rapid diagnostic tests and the impacts on transmission.
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Affiliation(s)
- Steve M Taylor
- Division of Infectious Diseases, Duke University Medical Center, Durham, North Carolina.,Department of Epidemiology, University of North Carolina Gillings School of Global Public Health, Chapel Hill, North Carolina.,Duke Global Health Institute, Durham, North Carolina
| | - Kelsey M Sumner
- Department of Epidemiology, University of North Carolina Gillings School of Global Public Health, Chapel Hill, North Carolina.,Division of Infectious Diseases, Duke University Medical Center, Durham, North Carolina
| | - Betsy Freedman
- Division of Infectious Diseases, Duke University Medical Center, Durham, North Carolina
| | | | - Andrew A Obala
- College of Health Sciences, Moi University, Eldoret, Kenya
| | - Wendy Prudhomme O'Meara
- College of Health Sciences, Moi University, Eldoret, Kenya.,Duke Global Health Institute, Durham, North Carolina.,Division of Infectious Diseases, Duke University Medical Center, Durham, North Carolina
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8
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Nelson CS, Sumner KM, Freedman E, Saelens JW, Obala AA, Mangeni JN, Taylor SM, O'Meara WP. High-resolution micro-epidemiology of parasite spatial and temporal dynamics in a high malaria transmission setting in Kenya. Nat Commun 2019; 10:5615. [PMID: 31819062 PMCID: PMC6901486 DOI: 10.1038/s41467-019-13578-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Accepted: 11/14/2019] [Indexed: 01/03/2023] Open
Abstract
Novel interventions that leverage the heterogeneity of parasite transmission are needed to achieve malaria elimination. To better understand spatial and temporal dynamics of transmission, we applied amplicon next-generation sequencing of two polymorphic gene regions (csp and ama1) to a cohort identified via reactive case detection in a high-transmission setting in western Kenya. From April 2013 to July 2014, we enrolled 442 symptomatic children with malaria, 442 matched controls, and all household members of both groups. Here, we evaluate genetic similarity between infected individuals using three indices: sharing of parasite haplotypes on binary and proportional scales and the L1 norm. Symptomatic children more commonly share haplotypes with their own household members. Furthermore, we observe robust temporal structuring of parasite genetic similarity and identify the unique molecular signature of an outbreak. These findings of both micro- and macro-scale organization of parasite populations might be harnessed to inform next-generation malaria control measures. Here, Nelson et al. use amplicon next-generation sequencing of two P. falciparum polymorphic gene regions to investigate the genetic similarity of parasite populations across time and space in a pediatric cohort in Kenya. They identify both micro- and macro-scale structuring of malaria parasites in this high-transmission setting, which could inform future intervention strategies.
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Affiliation(s)
- Cody S Nelson
- Duke Global Health Institute, Duke University, Durham, North Carolina, USA.
| | - Kelsey M Sumner
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, North Carolina, USA.,Division of Infectious Diseases, Duke University School of Medicine, Durham, North Carolina, USA
| | - Elizabeth Freedman
- Division of Infectious Diseases, Duke University School of Medicine, Durham, North Carolina, USA
| | - Joseph W Saelens
- Division of Infectious Diseases, Duke University School of Medicine, Durham, North Carolina, USA
| | - Andrew A Obala
- School of Medicine, Moi University College of Health Sciences, Eldoret, Kenya
| | - Judith N Mangeni
- School of Nursing, Moi University College of Health Sciences, Eldoret, Kenya
| | - Steve M Taylor
- Duke Global Health Institute, Duke University, Durham, North Carolina, USA.,Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, North Carolina, USA.,Division of Infectious Diseases, Duke University School of Medicine, Durham, North Carolina, USA
| | - Wendy P O'Meara
- Duke Global Health Institute, Duke University, Durham, North Carolina, USA.,Division of Infectious Diseases, Duke University School of Medicine, Durham, North Carolina, USA
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9
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Mangeni JN, Mwangi A, Mbugua S, Mukthar VK. MALE INVOLVEMENT IN MATERNAL HEALTHCARE AS A DETERMINANT OF UTILISATION OF SKILLED BIRTH ATTENDANTS IN KENYA. East Afr Med J 2012; 89:372-383. [PMID: 26852449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
OBJECTIVE To determine whether there is a relationship between male involvement in maternal health and utilisation of skilled birth attendants (SBAs) after controlling for socio-demographic and maternal characteristics. DESIGN Data from the Kenya Demographic and Health Survey (KDHS) conducted in 2008-09 were analysed. SETTING Nationally representative survey in Kenya. SUBJECTS The unit of analysis was couples who met the inclusion criteria of being married and having had a child in the three years before the survey. RESULTS The adjusted odds ratio after controlling for other factors indicates that women whose husbands attended at least one ANC visit were more likely to have skilled birth attendance than those whose husbands did not attend any ANC visits [AOR, 1.9; 95 percent CI, 1.09-3.32]. Maternal characteristics that had a statistically significant association with delivery by an SBA included educational level, employment, number of ANC visits, and parity. The province where the couple resided also was statistically significant. CONCLUSION In Kenya a male partner's participation, through attending ANC visits, is associated with a woman's use of an SBA during delivery.
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Affiliation(s)
- J N Mangeni
- Department of Community Health, Moi University, P. o. Box 4606, Eldoret, Kenya
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Mangeni JN, Ballidawa JB, Ndege S. Factors associated with willingness to accept a routine offer of HIV test in a large referral hospital in Western Kenya. East Afr J Public Health 2012; 9:44-49. [PMID: 23120949] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
OBJECTIVE Although Voluntary Counseling and Testing (VCT) has existed for more than 10 years, majority of Kenyans still do not know their HIV status, thus necessitating the introduction of other testing strategies to increase the number of people taking the test. The routine offer of an HIV test to all patients in health-care settings has been proposed to increase access to care. The main objective of this study was to identify factors associated with willingness to accept a routine offer of an HIV test. METHODS This was a cross sectional study. The Setting was in the Outpatient department at a large Referral Hospital in Western Kenya. A total of 384 adult patients (both males and females) were recruited using systematic random sampling. Information was collected on basic socio demographic characteristics, knowledge about the routine offer of an HIV test, attitudes towards the testing and HIV testing practise. RESULTS Of the 384 respondents, 64.3% were unaware about the routine offer of HIV testing in Health facilities. Multivariate analysis identified the main predictors of willingness to accept an HIV test offered in hospital as the age (OR 3.7, C.I 0.068-1.075), level of education (OR 3.4, C.I 0.186-62.602), Knowledge about the routine HIV testing (OR 4.6,C.I 2.118-9.847), self-perception of HIV risk (OR 8.4,C.I 3.424-20.496) and attitude towards routine offer of HIV testing (OR 9.2, C.I 0.042-0.284). CONCLUSION There is a need to come up with tailored training on the routine offer of an HIV test and devising strategies to address the main factors that influence the decision for patients to test as identified above.
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Affiliation(s)
- J N Mangeni
- Global Network, Moi Teaching and Referral Hospital Eldoret, Kenya.
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