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Leonard CM, Uhomoibhi P, Abubakar A, Ogunniyi A, Mba N, Greby SM, Okoye MI, Iriemenam NC, Ihekweazu C, Steinhardt L, Rogier E. Dynamics of IgG antibody response against Plasmodium antigens among Nigerian infants and young children. Front Immunol 2023; 14:1208822. [PMID: 37691957 PMCID: PMC10484571 DOI: 10.3389/fimmu.2023.1208822] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Accepted: 07/24/2023] [Indexed: 09/12/2023] Open
Abstract
Background Plasmodium falciparum malaria is a leading cause of child mortality in Nigeria. Neonates are born with maternal antibodies from placental transfer which may protect against malaria infection in the first months of life. The IgG dynamics of the transition from passively transferred antimalarial antibodies to actively acquired IgG from natural exposure have not been well elucidated. Methods Blood samples collected during a 2018 Nigeria nationwide HIV/AIDS household survey were available for 9,443 children under 5 years of age, with a subset of infants under 2 months of age having maternal samples available (n=41). Samples were assayed for the P. falciparum HRP2 antigen and anti-malarial IgG antibodies. LOESS regression examined the dynamics in IgG response in the first 5 years of life. Correlation with maternal IgG levels was assessed for mother/child pairs. Results Consistent decreases were observed in median IgG levels against all Plasmodium spp. antigen targets for the first months of life. At a population level, P. falciparum apical membrane antigen-1 (AMA1) and merozoite surface protein-1 19kD (PfMSP1) IgG decreased during the first 12 months of life before reaching a nadir, whereas IgGs to other targets only declined for the first 4 months of life. Seropositivity showed a similar decline with the lowest seropositivity against AMA1 and PfMSP1 at 10-12 months, though remaining above 50% during the first 2 years of life in higher transmission areas. No protective association was observed between IgG positivity and P. falciparum infection in infants. Maternal antibody levels showed a strong positive correlation with infant antibody levels for all P. falciparum antigens from birth to 2 months of age, but this correlation was lost by 6 months of age. Discussion Maternally transferred anti-malarial IgG antibodies rapidly decline during the first 6 months of life, with variations among specific antigens and malaria transmission intensity. From 3-23 months of age, there was a wide range in IgG levels for the blood-stage antigens indicating high individual variation in antibody production as children are infected with malaria. Non-falciparum species-specific antigens showed similar patterns in waning immunity and correlation with paired mother's IgG levels compared to P. falciparum antigens.
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Affiliation(s)
- Colleen M. Leonard
- Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, GA, United States
- Oak Ridge Institute for Science and Education, U.S. Department of Energy, Oak Ridge, TN, United States
| | - Perpetua Uhomoibhi
- National Malaria Elimination Programme, Federal Ministry of Health, Abuja, Nigeria
| | - Ado Abubakar
- Institute of Human Virology (IHVN), Abuja, Nigeria
| | | | - Nwando Mba
- Nigeria Centre for Disease Control (NCDC), Abuja, Nigeria
| | - Stacie M. Greby
- Division of Global HIV and Tuberculosis, Center for Global Health, Centers for Disease Control and Prevention, Abuja, Nigeria
| | - McPaul I. Okoye
- Division of Global HIV and Tuberculosis, Center for Global Health, Centers for Disease Control and Prevention, Abuja, Nigeria
| | - Nnaemeka C. Iriemenam
- Division of Global HIV and Tuberculosis, Center for Global Health, Centers for Disease Control and Prevention, Abuja, Nigeria
| | | | - Laura Steinhardt
- Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, GA, United States
| | - Eric Rogier
- Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, GA, United States
| | - NMS4 Technical Working Group
- Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, GA, United States
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Tassi Yunga S, Siriwardhana C, Fouda GG, Bobbili N, Sama G, Chen JJ, Leke RFG, Taylor DW. Characterization of the primary antibody response to Plasmodium falciparum antigens in infants living in a malaria-endemic area. Malar J 2022; 21:346. [PMCID: PMC9675181 DOI: 10.1186/s12936-022-04360-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2022] [Accepted: 11/03/2022] [Indexed: 11/21/2022] Open
Abstract
Background The primary antibody (Ab) response to Plasmodium falciparum is a critical step in developing immunity to malaria. Information on the initial Ab responses of babies in malaria-endemic areas is incomplete, in part, because babies receive maternal IgG via transplacental-transfer and usually become infected before maternal IgG wanes. The study aimed to identify the primary IgM and IgG Ab responses to malarial antigens in Cameroonian babies. Methods Infants (n = 70) living in a high malaria transmission area were followed from birth throughout the first year of life (mean 341 ± 42 days, an average of 8.5 time points per infant). Malaria infection was assessed by microscopy and PCR, and IgM and IgG antibodies (Abs) were measured using a multiplex immunoassay to AMA1, EBA-175, MSP1-42, MSP2, MSP3, RESA, LSA1, and CSP. Results The half-life of maternal IgG varied among the antigens, ranging from 0.7 to 2.5 months. The first infection of 41% of the babies was sub-microscopic and only 11 to 44% of the babies produced IgM to the above antigens; however, when the first infection was detected by microscopy, 59–82% of the infants made IgM Abs to the antigens. Infants were able to produce IgM even when maternal IgG was present, suggesting maternal Abs did not suppress the baby’s initial Ab response. Using longitudinal regression models that incorporated time-varying covariates, infants were found to produce IgG Ab to only AMA-1 when the first infection was sub-microscopic, but they produced IgG Abs to MSP1-42 (3D7, FVO), AMA1 (3D7, FVO) MSP2-FC27, MSP3, RESA, and LSA1, but not MSP 2-3D7, EBA-175, and CSP during their first slide-positive infection. Notably, the primary and secondary IgG responses were short-lived with little evidence of boosting. Conclusions The primary Ab response of babies who had maternal IgG was similar to that reported for primary infections in malaria-naïve adults. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-022-04360-x.
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Affiliation(s)
- Samuel Tassi Yunga
- grid.410445.00000 0001 2188 0957Department of Tropical Medicine, Medical Microbiology and Pharmacology, John A. Burns School of Medicine, University of Hawaii at Manoa, 651 Ilalo Street, Bioscience Building Suite 320, Honolulu, HI 96813 USA ,grid.5288.70000 0000 9758 5690Cancer Early Detection Advanced Research Center (CEDAR), School of Medicine, Knight Cancer Institute, Oregon Health & Science University, 2720 S. Moody Avenue, Portland, OR USA
| | - Chathura Siriwardhana
- grid.410445.00000 0001 2188 0957Department of Quantitative Health Sciences, John A. Burns School of Medicine, University of Hawaii at Manoa, 651 Ilalo Street, MEB411, Honolulu, HI 96813 USA
| | - Genevieve G. Fouda
- grid.5386.8000000041936877XDepartment of Pediatrics, Joan & Sanford I. Weill Medical College of Cornell University, New York, NY USA
| | - Naveen Bobbili
- grid.410445.00000 0001 2188 0957Department of Tropical Medicine, Medical Microbiology and Pharmacology, John A. Burns School of Medicine, University of Hawaii at Manoa, 651 Ilalo Street, Bioscience Building Suite 320, Honolulu, HI 96813 USA
| | - Grace Sama
- grid.412661.60000 0001 2173 8504The Biotechnology Center, University of Yaoundé 1, Messa, BP 3851 Yaoundé, Cameroon
| | - John J. Chen
- grid.410445.00000 0001 2188 0957Department of Quantitative Health Sciences, John A. Burns School of Medicine, University of Hawaii at Manoa, 651 Ilalo Street, MEB411, Honolulu, HI 96813 USA
| | - Rose F. G. Leke
- grid.412661.60000 0001 2173 8504The Biotechnology Center, University of Yaoundé 1, Messa, BP 3851 Yaoundé, Cameroon
| | - Diane Wallace Taylor
- grid.410445.00000 0001 2188 0957Department of Tropical Medicine, Medical Microbiology and Pharmacology, John A. Burns School of Medicine, University of Hawaii at Manoa, 651 Ilalo Street, Bioscience Building Suite 320, Honolulu, HI 96813 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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Isebe TI, Bargul JL, Gichuki BM, Njunge JM, Tuju J, Rono MK. Molecular characterization of Plasmodium falciparum PHISTb proteins as potential targets of naturally-acquired immunity against malaria. Wellcome Open Res 2021. [DOI: 10.12688/wellcomeopenres.15919.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Background: Plasmodium falciparum causes the deadliest form of malaria in humans. Upon infection, the host’s infected red blood cells (iRBCs) are remodelled by exported parasite proteins to provide a niche for parasite development and maturation. Methods: Here we analysed the role of three PHISTb proteins Pf3D7_0532400, Pf3D7_1401600, and Pf3D7_1102500 by expressing recombinant proteins and evaluated antibody responses against these proteins using immune sera from malaria-exposed individuals from Kenya and The Gambia in Africa. Results: Children and adults from malaria-endemic regions recognized the three PHISTb proteins. Responses against PHISTb proteins varied with malaria transmission intensity in three different geographical sites in Kenya (Siaya and Takaungu) and The Gambia (Sukuta). Antibody responses against PHISTb antigens Pf3D7_1102500 and Pf3D7_1401600 were higher in Sukuta, a low transmission region in Gambia, compared to Siaya, a high transmission region in western Kenya, unlike Pf3D7_0532400. Anti-PHIST responses indicate negative correlation between antibody levels and malaria transmission intensity for Pf3D7_1102500 and Pf3D7_1401600. We report a correlation in antibody responses between schizont and gametocyte extract, but this is not statistically significant (cor=0.102, p=0.2851, CI=95%) and, Pf3D7_0532400 (cor=0.11, p=0.249, CI=95%) and Pf3D7_1401600 (cor=0.02, p=0.7968, CI=95%). We report a negative correlation in antibody responses between schizont and Pf3D7_1102500 (cor=-0.008, p=0.9348, CI=95%). There is a correlation between gametocyte extract and Pf3D7_1401600 (cor=-0.0402, p=0.6735, CI=95%), Pf3D7_1102500 (cor=0.0758, p=0.4271, CI=95%) and Pf3D7_0532400 (cor=0.155, p=0.1028, CI=95%). Acquisition of anti-PHIST antibodies correlates with exposure to malaria for Pf3D7_0532400 (p=0.009) but not Pf3D7_1102500 and Pf3D7_1401600 (p=0.507 and p=0.15, respectively, CI=95%). Children aged below 2 years had the lowest antibody levels which do not correlate with age differences. Conclusions: Collectively, these findings provide evidence of natural immunity against PHISTb antigens that varies with level of malaria exposure and underscore their potential as possible serological markers to P. falciparum infection aimed at contributing to malaria control through vaccine development.
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Peterson I, Kapito-Tembo A, Bauleni A, Nyirenda O, Pensulo P, Still W, Valim C, Cohee L, Taylor T, Mathanga DP, Laufer M. Overdiagnosis of Malaria Illness in an Endemic Setting: A Facility-Based Surveillance Study in Malawi. Am J Trop Med Hyg 2021; 104:2123-2130. [PMID: 33939628 DOI: 10.4269/ajtmh.20-1209] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Accepted: 03/03/2021] [Indexed: 11/07/2022] Open
Abstract
In endemic settings where asymptomatic malaria infections are common, malaria infection can complicate fever diagnosis. Factors influencing fever misdiagnosis, including accuracy of malaria rapid diagnostic tests (mRDTs) and the malaria-attributable fraction of fevers (MAF), require further investigation. We conducted facility-based surveillance in Malawi, from January 2012 through December 2013 in settings of high perennial (Chikhwawa), high seasonal (Thoylo), and moderate seasonal (Ndirande) malaria transmission. Consecutive patients presenting to outpatient departments were screened; those with suspected malaria illness were tested by mRDT or routine thick-smear microscopy. Test positivity rates (TPRs), positive predictive value (PPVs) of mRDTs, and MAFs were calculated by site, age, and season. Of 41,471 patients, 10,052 (24.2%) tested positive for malaria. The TPR was significantly greater in Chikhwawa (29.9%; 95% CI, 28.6-30.0) compared with Thyolo (13.2%; 95% CI, 12.5-13.7) and Ndirande (13.1%; 95% CI, 12.2-14.4). The overall PPV was 77.8% (95% CI, 76.8-78.7); it was lowest among infants (69.9%; 95% CI, 65.5-74.2) and highest among school-age children (81.9%; 95% CI, 80.3-83.4). Malaria infection accounted for about 50% of fevers in children younger than 5 years old with microscopy-confirmed Plasmodium falciparum infection, and less than 20% of such fevers in school-age children. Outpatient settings in Malawi had a high burden of malaria illness, but also possible overdiagnosis of malaria illness. Interventions to reduce malaria transmission and rapid testing for other common febrile illness may improve diagnostic clarity among outpatients in malaria endemic settings.
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Affiliation(s)
- Ingrid Peterson
- 1Center for Vaccine Development and Global Health, University of Maryland Baltimore, Baltimore, Maryland.,2Blantyre Malaria Project, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Atupele Kapito-Tembo
- 3Malaria Alert Center, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Andrew Bauleni
- 3Malaria Alert Center, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Osward Nyirenda
- 2Blantyre Malaria Project, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Paul Pensulo
- 2Blantyre Malaria Project, College of Medicine, University of Malawi, Blantyre, Malawi
| | - William Still
- 1Center for Vaccine Development and Global Health, University of Maryland Baltimore, Baltimore, Maryland
| | - Clarissa Valim
- 4Department of Global Health, Boston University School of Public Health, Boston, Massachusetts
| | - Lauren Cohee
- 1Center for Vaccine Development and Global Health, University of Maryland Baltimore, Baltimore, Maryland
| | - Terrie Taylor
- 5Department of Osteopathic Medical Specialties, College of Osteopathic Medicine, Michigan State University, East Lansing, Michigan
| | - Don P Mathanga
- 3Malaria Alert Center, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Miriam Laufer
- 1Center for Vaccine Development and Global Health, University of Maryland Baltimore, Baltimore, Maryland
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Parra M, Yang J, Weitner M, Akkoyunlu M. Neonatal mice resist Plasmodium yoelii infection until exposed to para-aminobenzoic acid containing diet after weaning. Sci Rep 2021; 11:90. [PMID: 33420157 PMCID: PMC7794322 DOI: 10.1038/s41598-020-79703-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 12/04/2020] [Indexed: 12/03/2022] Open
Abstract
We developed a newborn (NB) mouse Plasmodium yoelii NL infection model to study malaria in early age. Surprisingly, the onset of parasitemia in P. yoelii challenged NB mice was delayed compared to adults and coincided with the weaning date when weanlings switched from maternal milk to normal chow diet. Also, compared to adult mice, parasitemia resolved much later (48 days vs 20 days post challenge) and the peak parasitemia was twice as high in weanlings. Concurrently, weanlings’ germinal center reaction was delayed and diminished compared to adult mice. Maternal milk is deficient in para-aminobenzoic acid (PABA), which is required for de novo folate synthesis by Plasmodium. Suggesting a possible role for the protection afforded by PABA-deficient maternal milk, mice fed with a PABA-deficient diet after the weaning continued to control parasitemia. Despite the reduced parasitemia, these mice developed robust T follicular helper (Tfh) responses and were protected from a second P. yoelii challenge. The NB malaria model provides mechanistic insight into the human infant malaria manifestations where a diet solely based on breast-feeding reduces the incidence of severe malaria in infants. NB mice experiments also support further studies to investigate dietary PABA restriction in the management of severe malaria in infants.
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Affiliation(s)
- Marcela Parra
- Center for Biologics Evaluation and Research, Division of Bacterial Allergenic and Parasitic Diseases, US Food and Drug Administration, Silver Spring, MD, USA
| | - Jiyeon Yang
- Center for Biologics Evaluation and Research, Division of Bacterial Allergenic and Parasitic Diseases, US Food and Drug Administration, Silver Spring, MD, USA
| | - Megan Weitner
- Center for Biologics Evaluation and Research, Division of Bacterial Allergenic and Parasitic Diseases, US Food and Drug Administration, Silver Spring, MD, USA.,Viral & Rickettsial Diseases Department (NMRC VRDD), Naval Medical Research Center, Silver Spring, MD, USA
| | - Mustafa Akkoyunlu
- Center for Biologics Evaluation and Research, Division of Bacterial Allergenic and Parasitic Diseases, US Food and Drug Administration, Silver Spring, MD, USA. .,DBPAP, US FDA, CBER, 10903 New Hampshire Ave., Building 52/72, Room, 5214, Silver Spring, MD, 209903, USA.
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Profiles of Plasmodium falciparum infections detected by microscopy through the first year of life in Kintampo a high transmission area of Ghana. PLoS One 2020; 15:e0240814. [PMID: 33075074 PMCID: PMC7571695 DOI: 10.1371/journal.pone.0240814] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Accepted: 10/02/2020] [Indexed: 11/24/2022] Open
Abstract
Although malaria mortality among children under five years of age is high, the characteristics of their infection patterns are not well described. The aim of this study was to examine the longitudinal sequence pattern of Plasmodium falciparum infections in the first year of life within a birth cohort in Kintampo, Ghana (N = 1855). Infants were monitored at home with monthly sampling and also at the clinic for any febrile illness between 2008 and 2011. Light microscopy was performed on monthly scheduled visits and febrile ill visits over twelve months of follow-ups (n = 19231). Microscopy-positive visits accompanied with or without symptoms were rare during the first five months of life but were common from six to twelve months of age. Among 1264 infants with microscopy data over a minimum of eight monthly visits and also throughout in sick visits, some were microscopy negative (36%), and others positive: only-symptomatic (35%), alternating (22%) and only-asymptomatic (7%). The median age of microscopic infection was seven months for the alternating group and eight months for both the only-symptomatic and only-asymptomatic groups. The alternating group had the highest cumulative incidence of microscopic infections, the lowest age at first infection and 87 different infection patterns. Parasite densities detected by microscopy were significantly higher for symptomatic versus asymptomatic infection. We conclude that infants in malaria endemic areas experience diverse infection profiles throughout their first year of life. Further investigations should include submicroscopic reservoir and may shed more light on the factors that determine susceptibility to malaria during infancy.
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Danwang C, Bigna JJ, Nzalie RNT, Robert A. Epidemiology of clinical congenital and neonatal malaria in endemic settings: a systematic review and meta-analysis. Malar J 2020; 19:312. [PMID: 32859209 PMCID: PMC7456021 DOI: 10.1186/s12936-020-03373-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 08/12/2020] [Indexed: 01/23/2023] Open
Abstract
Background In order to attain the objectives set out in the global technical strategy against malaria 2016–2030, it is important to have accurate epidemiological data on malaria in all age categories, including those which are often neglected because of an apparent low burden of disease. The current systematic review with meta-analysis synthesizes the epidemiology of clinical congenital and neonatal malaria in endemic areas. Methods PubMed, EMBASE, Global Index Medicus, and Web of Science were searched up to 30th October 2019, to identify observational studies reporting on congenital (0–7 days) and neonatal (0–28 days) malaria. No restriction related to language was applied. Study selection, data extraction, and methodological quality assessment were performed independently by two investigators. A random-effects meta-analysis was used to pool prevalence data. Prevalence were adjusted taking into account the variance due to diagnostic method and regional distribution. Subgroup analyses were performed to identify sources of heterogeneity in case of substantial heterogeneity. This review was registered in PROSPERO with number CRD42020150124. Results The bibliographical search identified 1,961 studies, of which 22 were finally retained with a total population of 28,083 neonates. The overall crude prevalence of clinical congenital malaria was 40.4‰ (95%CI 19.6–67.7; 17 studies). The adjusted prevalence considering the variance due to difference in region/country (hierarchical model) was 33.7‰ (95%CI 6.9–77.2). There was no difference between the prevalence of clinical congenital malaria in Africa 39.5‰ (95%CI 17.2–59.5; 15 studies) and outside Africa 56.3‰ (95%CI 0.0–406.1), p = 0.867. The overall crude prevalence of clinical neonatal malaria was 12.0‰ (95%CI 1.4–30.3; 12 studies), and the adjusted one (considering the variance due to diagnostic method and the region/country) was 12.9‰ (95%CI 0.1–39.7). There was no difference between the prevalence of clinical neonatal malaria in Africa 12.1‰ (95%CI 1.3–31.2; 11 studies) and outside Africa 12.5‰ (95%CI 0.0–52.9), p = 0.802. Conclusion This study suggests a high prevalence of clinical congenital and neonatal malaria. It calls for an intensification of preventive measures against malaria during pregnancy and in the neonatal period, and to consider neonates as a distinct age category in the elaboration of malaria treatment and prevention guidelines.
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Affiliation(s)
- Celestin Danwang
- Epidemiology and Biostatistics Unit, Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain, Brussels, Belgium.
| | - Jean Joel Bigna
- Department of Epidemiology and Public Health, Centre Pasteur of Cameroon, Yaoundé, Cameroon
| | | | - Annie Robert
- Epidemiology and Biostatistics Unit, Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain, Brussels, Belgium
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Park S, Nixon CE, Pond-Tor S, Kabyemela ER, Fried M, Duffy PE, Kurtis JD, Friedman JF. Impact of maternally derived antibodies to Plasmodium falciparum Schizont Egress Antigen-1 on the endogenous production of anti-PfSEA-1 in offspring. Vaccine 2019; 37:5044-5050. [PMID: 31288996 PMCID: PMC6677924 DOI: 10.1016/j.vaccine.2019.06.084] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Revised: 06/07/2019] [Accepted: 06/27/2019] [Indexed: 02/03/2023]
Abstract
Background We evaluated whether maternally-derived antibodies to a malarial vaccine candidate, Plasmodium falciparum Schizont Egress Antigen-1 (PfSEA-1), in cord blood interfered with the development of infant anti-PfSEA-1 antibodies in response to natural exposure. Methods We followed 630 Tanzanian infants who were measured their antibodies against PfSEA-1 (aa 810-1023; PfSEA-1A) at birth and 6, 12, 18, and 24 months of age, and examined the changes in anti-PfSEA-1A antibody levels in response to parasitemia, and evaluated whether maternally-derived anti-PfSEA-1A antibodies in cord blood modified infant anti-PfSEA-1A immune responses. Results Infants who experienced parasitemia during the first 6 months of life had significantly higher anti-PfSEA-1A antibodies at 6 and 12 months of age compared to uninfected infants. Maternally-derived anti-PfSEA-1A antibodies in cord blood significantly modified this effect during the first 6 months. During this period, infant anti-PfSEA-1A antibody levels were significantly associated with their P. falciparum exposure when they were born with low, but not higher, maternally-derived anti-PfSEA-1A antibody levels in cord blood. Nevertheless, during the first 6 months of life, maternally-derived anti-PfSEA-1A antibodies in cord blood did not abrogate the parasitemia driven development of infant anti-PfSEA-1A: parasitemia were significantly correlated with anti-PfSEA-1A antibody levels at 6 months of age in the infants born with low maternally-derived anti-PfSEA-1A antibody levels in cord blood and borderline significantly correlated in those infants born with middle and high levels. Conclusions Maternal vaccination with PfSEA-1A is unlikely to interfere with the development of naturally acquired anti-PfSEA-1A immune responses following exposure during infancy.
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Affiliation(s)
- Sangshin Park
- Center for International Health Research, Rhode Island Hospital, The Warren Alpert Medical School of Brown University, Providence, RI 02903, United States; Department of Pediatrics, The Warren Alpert Medical School of Brown University, Providence, RI 02903, United States; Graduate School of Urban Public Health, University of Seoul, Seoul 02504, Republic of Korea.
| | - Christina E Nixon
- Center for International Health Research, Rhode Island Hospital, The Warren Alpert Medical School of Brown University, Providence, RI 02903, United States; Department of Pathology and Laboratory Medicine, The Warren Alpert Medical School of Brown University, Providence, RI 02903, United States
| | - Sunthorn Pond-Tor
- Center for International Health Research, Rhode Island Hospital, The Warren Alpert Medical School of Brown University, Providence, RI 02903, United States; Department of Pathology and Laboratory Medicine, The Warren Alpert Medical School of Brown University, Providence, RI 02903, United States
| | - Edward R Kabyemela
- Mother Offspring Malaria Studies (MOMS) Project, Seattle Biomedical Research Institute, Seattle, WA 98109, United States; Muheza Designated District Hospital, Muheza, Tanzania; Tumaini University, Moshi, Tanzania
| | - Michal Fried
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, NIH, Rockville, MD 20892, United States
| | - Patrick E Duffy
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, NIH, Rockville, MD 20892, United States
| | - Jonathan D Kurtis
- Center for International Health Research, Rhode Island Hospital, The Warren Alpert Medical School of Brown University, Providence, RI 02903, United States; Department of Pathology and Laboratory Medicine, The Warren Alpert Medical School of Brown University, Providence, RI 02903, United States
| | - Jennifer F Friedman
- Center for International Health Research, Rhode Island Hospital, The Warren Alpert Medical School of Brown University, Providence, RI 02903, United States; Department of Pediatrics, The Warren Alpert Medical School of Brown University, Providence, RI 02903, United States
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Dollat M, Talla C, Sokhna C, Diene Sarr F, Trape JF, Richard V. Measuring malaria morbidity in an area of seasonal transmission: Pyrogenic parasitemia thresholds based on a 20-year follow-up study. PLoS One 2019; 14:e0217903. [PMID: 31246965 PMCID: PMC6597048 DOI: 10.1371/journal.pone.0217903] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Accepted: 05/22/2019] [Indexed: 01/12/2023] Open
Abstract
Introduction Asymptomatic carriage of P. falciparum is frequent in areas endemic for malaria and individual diagnosis of clinical malaria attacks is still difficult. We investigated the impact of changes in malaria endemicity on the diagnostic criteria for malaria attacks in an area of seasonal malaria transmission. Methods We analyzed the longitudinal data collected over 20 years from a daily survey of all inhabitants of Ndiop, a rural community in central Senegal, in a logistic regression model to investigate the relationship between the level of Plasmodium falciparum parasitemia and the risk of fever, with the aim of determining the best parasitemia thresholds for attributing to malaria a fever episode. Results A total of 34,136 observations recorded from July 1993 to December 2013 from 850 individuals aged from 1 day to 87 years were included. P. falciparum asymptomatic carriage declined from 36% to 1% between 1993 and 2013. A total of 9,819 fever episodes were associated with a positive blood film for P. falciparum. Using age-dependent parasitemia thresholds for attributing to malaria a fever episode, we recorded 6,006 malaria attacks during the study period. Parasitemia thresholds seemed to be lower during the low-to-zero transmission season and tended to decrease with changes in control policies. The number of clinical malaria attacks was overestimated for all age groups throughout the study when all fever episodes associated with P. falciparum parasitemia were defined as malaria attacks. Conclusion Pyrogenic thresholds are particularly sensitive to changes in malaria epidemiology and are therefore an interesting tool to accurately assess the burden of malaria in the context of declining transmission.
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Affiliation(s)
- Marion Dollat
- Unité d'Epidémiologie des Maladies Infectieuses, Institut Pasteur de Dakar, Dakar, Sénégal
- Service de Maladies Infectieuses et Tropicales, Hôpital Avicenne, Assistance Publique-Hôpitaux de Paris (AP-HP), Paris, France
- * E-mail:
| | - Cheikh Talla
- Unité d'Epidémiologie des Maladies Infectieuses, Institut Pasteur de Dakar, Dakar, Sénégal
| | - Cheikh Sokhna
- Laboratoire de Paludologie, Institut de Recherche pour le Développement, Dakar, Sénégal
| | - Fatoumata Diene Sarr
- Unité d'Epidémiologie des Maladies Infectieuses, Institut Pasteur de Dakar, Dakar, Sénégal
| | - Jean-François Trape
- Laboratoire de Paludologie, Institut de Recherche pour le Développement, Dakar, Sénégal
| | - Vincent Richard
- Unité d'Epidémiologie des Maladies Infectieuses, Institut Pasteur de Dakar, Dakar, Sénégal
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11
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Good MF, Miller LH. Interpreting challenge data from early phase malaria blood stage vaccine trials. Expert Rev Vaccines 2018; 17:189-196. [PMID: 29382292 DOI: 10.1080/14760584.2018.1435278] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
INTRODUCTION As the quest for an effective blood stage malaria vaccine continues, there is increasing reliance on the use of controlled human malaria infections (CHMI) in non-endemic settings to test vaccine efficacy at the earliest possible time. This is seen as a way to accelerate vaccine research and quickly eliminate candidates with poor efficacy. Areas covered: The data from these studies need to be carefully examined and interpreted in light of the very different roles that antibody and cellular immunity play in protection and within the context of the distinct clinical sensitivities of volunteers living in malaria-non-endemic countries compared to those living in endemic countries. With current strategies, it is likely that vaccines with protective immunological 'signatures' will be missed and potentially good candidates discarded. Expert commentary: Efficacy data from early phase vaccine trials in non-endemic countries should not be used to decide whether or not to proceed to vaccine trials in endemic countries.
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Affiliation(s)
- Michael F Good
- a Institute for Glycomics , Griffith University , Queensland , Australia.,b Department of Medical Microbiology and Immunology, University of Alberta , Edmonton , Canada
| | - Louis H Miller
- c Malaria Cell Biology Section, National Institute of Allergy and Infectious Diseases , National Institutes of Health , Bethesda , MD , USA
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12
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McLean ARD, Stanisic D, McGready R, Chotivanich K, Clapham C, Baiwog F, Pimanpanarak M, Siba P, Mueller I, King CL, Nosten F, Beeson JG, Rogerson S, Simpson JA, Fowkes FJI. P. falciparum infection and maternofetal antibody transfer in malaria-endemic settings of varying transmission. PLoS One 2017; 12:e0186577. [PMID: 29028827 PMCID: PMC5640245 DOI: 10.1371/journal.pone.0186577] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 10/03/2017] [Indexed: 01/16/2023] Open
Abstract
Introduction During pregnancy, immunoglobulin G (IgG) is transferred from the mother to the fetus, providing protection from disease in early infancy. Plasmodium falciparum infections may reduce maternofetal antibody transfer efficiency, but mechanisms remain unclear. Methods Mother-cord paired serum samples collected at delivery from Papua New Guinea (PNG) and the Thailand-Myanmar Border Area (TMBA) were tested for IgG1 and IgG3 to four P. falciparum antigens and measles antigen, as well as total serum IgG. Multivariable linear regression was conducted to assess the association of peripheral P. falciparum infection during pregnancy or placental P. falciparum infection assessed at delivery with maternofetal antibody transfer efficiency. Path analysis assessed the extent to which associations between P. falciparum infection and antibody transfer were mediated by gestational age at delivery or levels of maternal total serum IgG. Results Maternofetal antibody transfer efficiency of IgG1 and IgG3 was lower in PNG compared to TMBA (mean difference in cord antibody levels (controlling for maternal antibody levels) ranged from -0.88 to 0.09, median of -0.20 log2 units). Placental P. falciparum infections were associated with substantially lower maternofetal antibody transfer efficiency in PNG primigravid women (mean difference in cord antibody levels (controlling for maternal antibody levels) ranged from -0.62 to -0.10, median of -0.36 log2 units), but not multigravid women. The lower antibody transfer efficiency amongst primigravid women with placental infection was only partially mediated by gestational age at delivery (proportion indirect effect ranged from 0% to 18%), whereas no mediation effects of maternal total serum IgG were observed. Discussion Primigravid women may be at risk of impaired maternofetal antibody transport with placental P. falciparum infection. Direct effects of P. falciparum on the placenta, rather than earlier gestational age and elevated serum IgG, are likely responsible for the majority of the reduction in maternofetal antibody transfer efficiency with placental infection.
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Affiliation(s)
- Alistair R. D. McLean
- Burnet Institute, Melbourne, Victoria, Australia
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia
- Myanmar Oxford Clinical Research Unit, Yangon, Myanmar
| | - Danielle Stanisic
- Institute for Glycomics, Griffith University, Gold Coast Campus, Southport, Queensland, Australia
| | - Rose McGready
- Shoklo Malaria Research Unit (SMRU), Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Kesinee Chotivanich
- Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Caroline Clapham
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - Francesca Baiwog
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - Mupawjay Pimanpanarak
- Shoklo Malaria Research Unit (SMRU), Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
| | - Peter Siba
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - Ivo Mueller
- Population Health & Immunity Division, WEHI, Parkville, Victoria, Australia
- Malaria: Parasites & Hosts Unit, Institut Pasteur, Paris, France
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, Australia
| | - Christopher L. King
- Center for Global Health and Diseases, Case Western Reserve University, and Veterans Affairs Medical Center, Cleveland, OH, United States of America
| | - François Nosten
- Shoklo Malaria Research Unit (SMRU), Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - James G. Beeson
- Burnet Institute, Melbourne, Victoria, Australia
- Department of Medicine, University of Melbourne, Melbourne, Australia
- Department of Microbiology and Central Clinical School, Monash University, Melbourne, Victoria, Australia
| | - Stephen Rogerson
- Department of Medicine, University of Melbourne, Melbourne, Australia
| | - Julie A. Simpson
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia
| | - Freya J. I. Fowkes
- Burnet Institute, Melbourne, Victoria, Australia
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Australia
- Department of Epidemiology and Preventative Medicine, Monash University, Melbourne, Victoria, Australia
- * E-mail:
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Mechanism of splenic cell death and host mortality in a Plasmodium yoelii malaria model. Sci Rep 2017; 7:10438. [PMID: 28874800 PMCID: PMC5585408 DOI: 10.1038/s41598-017-10776-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Accepted: 08/14/2017] [Indexed: 12/14/2022] Open
Abstract
Malaria is a fatal disease that displays a spectrum of symptoms and severity, which are determined by complex host-parasite interactions. It has been difficult to study the effects of parasite strains on disease severity in human infections, but the mechanisms leading to specific disease phenotypes can be investigated using strains of rodent malaria parasites that cause different disease symptoms in inbred mice. Using a unique mouse malaria model, here we investigated the mechanisms of splenic cell death and their relationship to control of parasitemia and host mortality. C57BL/6 mice infected with Plasmodium yoelii nigeriensis N67C display high levels of pro-inflammatory cytokines and chemokines (IL-6, IFN-γ, TNF-α, CXCL1, and CCL2) and extensive splenic damage with dramatic reduction of splenic cell populations. These disease phenotypes were rescued in RAG2−/−, IFN-γ−/−, or T cell depleted mice, suggesting IFN-γ and T cell mediated disease mechanisms. Additionally, apoptosis was one of the major pathways involved in splenic cell death, which coincides with the peaks of pro-inflammatory cytokines. Our results demonstrate the critical roles of T cells and IFN-γ in mediating splenic cell apoptosis, parasitemia control, and host lethality and thus may provide important insights for preventing/reducing morbidity associated with severe malaria in humans.
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Ndyomugyenyi R, Magnussen P, Lal S, Hansen K, Clarke SE. Appropriate targeting of artemisinin-based combination therapy by community health workers using malaria rapid diagnostic tests: findings from randomized trials in two contrasting areas of high and low malaria transmission in south-western Uganda. Trop Med Int Health 2016; 21:1157-70. [PMID: 27383558 PMCID: PMC5031222 DOI: 10.1111/tmi.12748] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Objective To compare the impact of malaria rapid diagnostic tests (mRDTs), used by community health workers (CHWs), on the proportion of children <5 years of age receiving appropriately targeted treatment with artemisinin‐based combination therapy (ACT), vs. presumptive treatment. Methods Cluster‐randomized trials were conducted in two contrasting areas of moderate‐to‐high and low malaria transmission in rural Uganda. Each trial examined the effectiveness of mRDTs in the management of malaria and targeting of ACTs by CHWs comparing two diagnostic approaches: (i) presumptive clinical diagnosis of malaria [control arm] and (ii) confirmatory diagnosis with mRDTs followed by ACT treatment for positive patients [intervention arm], with village as the unit of randomisation. Treatment decisions by CHWs were validated by microscopy on a reference blood slide collected at the time of consultation, to compare the proportion of children <5 years receiving appropriately targeted ACT treatment, defined as patients with microscopically‐confirmed presence of parasites in a peripheral blood smear receiving artemether‐lumefantrine or rectal artesunate, and patients with no malaria parasites not given ACT. Results In the moderate‐to‐high transmission area, ACT treatment was appropriately targeted in 79.3% (520/656) of children seen by CHWs using mRDTs to diagnose malaria, vs. 30.8% (215/699) of children seen by CHWs using presumptive diagnosis (P < 0.001). In the low transmission area, 90.1% (363/403) children seen by CHWs using mRDTs received appropriately targeted ACT treatment vs. 7.8% (64/817) seen by CHWs using presumptive diagnosis (P < 0.001). Low mRDT sensitivity in children with low‐density parasitaemia (<200 parasites/μl) was identified as a potential concern. Conclusion When equipped with mRDTs, ACT treatments delivered by CHWs are more accurately targeted to children with malaria parasites. mRDT use could play an important role in reducing overdiagnosis of malaria and improving fever case management within iCCM, in both moderate‐to‐high and low transmission areas. Nonetheless, missed treatments due to the low sensitivity of current mRDTs in patients with low parasite density are a concern. For community‐based treatment in areas of low transmission and/or non‐immune populations, presumptive treatment of all fevers as malaria may be advisable, until more sensitive diagnostic assays, suitable for routine use by CHWs in remote settings, become available.
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Affiliation(s)
| | - Pascal Magnussen
- Centre for Medical Parasitology, Department for Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Sham Lal
- Department of Disease Control, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK
| | - Kristian Hansen
- Department of Global Health and Development, Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine, London, UK
| | - Siân E Clarke
- Department of Disease Control, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK
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15
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Sylvester B, Gasarasi DB, Aboud S, Tarimo D, Massawe S, Mpembeni R, Swedberg G. Prenatal exposure to Plasmodium falciparum increases frequency and shortens time from birth to first clinical malaria episodes during the first two years of life: prospective birth cohort study. Malar J 2016; 15:379. [PMID: 27448394 PMCID: PMC4957302 DOI: 10.1186/s12936-016-1417-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2016] [Accepted: 07/04/2016] [Indexed: 11/23/2022] Open
Abstract
Background Prenatal exposure to Plasmodium falciparum affects development of protective immunity and susceptibility to subsequent natural challenges with similar parasite antigens. However, the nature of these effects has not been fully elucidated. The aim of this study was to determine the effect of prenatal exposure to P. falciparum on susceptibility to natural malaria infection, with a focus on median time from birth to first clinical malaria episode and frequency of clinical malaria episodes in the first 2 years of life. Methods A prospective birth cohort study was conducted in Rufiji district in Tanzania, between January 2013 and December 2015. Infants born to mothers with P. falciparum in the placenta at time of delivery were defined as exposed, and infants born to mothers without P. falciparum parasites in placenta were defined as unexposed. Placental infection was established by histological techniques. Out of 206 infants recruited, 41 were in utero exposed to P. falciparum and 165 infants were unexposed. All infants were monitored for onset of clinical malaria episodes in the first 2 years of life. The outcome measure was time from birth to first clinical malaria episode, defined by fever (≥37 °C) and microscopically determined parasitaemia. Median time to first clinical malaria episode between exposed and unexposed infants was assessed using Kaplan–Meier survival analysis and comparison was done by log rank. Association of clinical malaria episodes with prenatal exposure to P. falciparum was assessed by multivariate binary logistic regression. Comparative analysis of mean number of clinical malaria episodes between exposed and unexposed infants was done using independent sample t test. Results The effect of prenatal exposure to P. falciparum infection on clinical malaria episodes was statistically significant (Odds Ratio of 4.79, 95 % CI 2.21–10.38, p < 0.01) when compared to other confounding factors. Median time from birth to first clinical malaria episode for exposed and unexposed infants was 32 weeks (95 % CI 30.88–33.12) and 37 weeks (95 % CI 35.25–38.75), respectively, and the difference was statistically significant (p = 0.003). The mean number of clinical malaria episodes in exposed and unexposed infants was 0.51 and 0.30 episodes/infant, respectively, and the difference was statistically significant (p = 0.038). Conclusions Prenatal exposure to P. falciparum shortens time from birth to first clinical malaria episode and increases frequency of clinical malaria episodes in the first 2 years of life.
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Affiliation(s)
- Boniphace Sylvester
- Department of Parasitology and Medical Entomology, School of Public Health and Social Sciences, Muhimbili University of Health and Allied Sciences, P.O.BOX 65001, Dar es Salaam, Tanzania.
| | - Dinah B Gasarasi
- Department of Parasitology and Medical Entomology, School of Public Health and Social Sciences, Muhimbili University of Health and Allied Sciences, P.O.BOX 65001, Dar es Salaam, Tanzania
| | - Said Aboud
- Department of Microbiology and Immunology, School of Medicine, Muhimbili University of Health and Allied Sciences, P.O.BOX 65001, Dar es Salaam, Tanzania
| | - Donath Tarimo
- Department of Parasitology and Medical Entomology, School of Public Health and Social Sciences, Muhimbili University of Health and Allied Sciences, P.O.BOX 65001, Dar es Salaam, Tanzania
| | - Siriel Massawe
- Department of Obstetrics and Gynaecology, School of Medicine, Muhimbili University of Health and Allied Sciences, P.O.BOX 65001, Dar es Salaam, Tanzania
| | - Rose Mpembeni
- Department of Community Medicine, School of Public Health and Social Sciences, Muhimbili University of Health and Allied Sciences, P.O.BOX 65001, Dar es Salaam, Tanzania
| | - Gote Swedberg
- Department of Medical Biochemistry, Biomedical Centre, Uppsala University, Uppsala, Sweden
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16
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Gonçalves D, Hunziker P. Transmission-blocking strategies: the roadmap from laboratory bench to the community. Malar J 2016; 15:95. [PMID: 26888537 PMCID: PMC4758146 DOI: 10.1186/s12936-016-1163-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2015] [Accepted: 02/11/2016] [Indexed: 11/10/2022] Open
Abstract
Malaria remains one of the most prevalent tropical and infectious diseases in the world, with an estimated more than 200 million clinical cases every year. In recent years, the mosquito stages of the parasite life cycle have received renewed attention with some progress being made in the development of transmission-blocking strategies. From gametocytes to late ookinetes, some attractive antigenic targets have been found and tested in order to develop a transmission blocking vaccine, and drugs are being currently screened for gametocytocidal activity, and also some new and less conventional approaches are drawing increased attention, such as genetically modified and fungus-infected mosquitoes that become refractory to Plasmodium infection. In this review some of those strategies focusing on the progress made so far will be summarized, but also, the challenges that come from the translation of early promising benchwork resulting in successful applications in the field. To do this, the available literature will be screened and all the pieces of the puzzle must be combined: from molecular biology to epidemiologic and clinical data.
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Affiliation(s)
- Daniel Gonçalves
- CLINAM Foundation for Nanomedicine, University of Basel, Basel, Switzerland.
| | - Patrick Hunziker
- CLINAM Foundation for Nanomedicine, University of Basel, Basel, Switzerland.
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Enyuma COA, Ekanem EE, Udo JJ, Asindi AA. Hematological indices in febrile neonates with malaria parasitaemia in Calabar. Niger Med J 2016; 56:323-6. [PMID: 26778882 PMCID: PMC4698846 DOI: 10.4103/0300-1652.170383] [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] [Indexed: 11/13/2022] Open
Abstract
Background: Normal hematological indices has been determined in Nigerian newborns and found to be lower compared to their Caucasian counterparts. This was attributed to genetic factors. Malaria is endemic in Nigeria and is one of the major causes of ill health and death. Anemia is an important manifestation of malaria. Resistance by malaria parasites to antimalarial drug exacerbates the situation by continuous hemolysis. Aim: To determine the hematological indices in febrile newborn with malaria parasitemia. Materials and Methods: One-hundred fifty neonates (0-28 days) with fever admitted into the Newborn Unit of University of Calabar Teaching Hospital, over a 6 months period, were recruited consecutively. Blood film for malaria parasites and samples for full blood count were obtained and sent to the laboratory before commencement of the treatment. Data analysis was with SPSS version 14. Results: One-hundred fifty babies were recruited into the study. Most (85.3%) of the babies were aged ≤7 days. Six babies (4%) had malaria parasitemia. Plasmodium falciparum was the only species identified. All the babies that had parasitemia were anemic (mean hemoglobin [Hb] concentration of 12.6 g/dl) even when parasite count was low (average of 30.6/µl) though this could not be attributed solely to malaria. None of these neonates was transfused. All the other hematological indices were within the normal range of healthy newborn population irrespective of parasitization. Conclusion: Neonatal malaria does occur in our environment. While it does not affect the white blood indices, it lowers neonatal Hb. It is recommended that Hb concentration be estimated in newborns with malaria to reduce infant morbidity and mortality in our environment.
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Affiliation(s)
- Callistus O A Enyuma
- Department of Paediatrics, University of Calabar, Calabar and University of Calabar Teaching Hospital, Calabar, Cross River State, Nigeria
| | - Emmanuel E Ekanem
- Department of Paediatrics, University of Calabar, Calabar and University of Calabar Teaching Hospital, Calabar, Cross River State, Nigeria
| | - Jacob J Udo
- Department of Paediatrics, University of Calabar, Calabar and University of Calabar Teaching Hospital, Calabar, Cross River State, Nigeria
| | - Asindi A Asindi
- Department of Paediatrics, University of Calabar, Calabar and University of Calabar Teaching Hospital, Calabar, Cross River State, Nigeria
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Abstract
Malaria is one of the most serious infectious diseases with most of the severe disease
caused by Plasmodium falciparum (Pf). Naturally acquired immunity
develops over time after repeated infections and the development of antimalarial
antibodies is thought to play a crucial role. Neonates and young infants are relatively
protected from symptomatic malaria through mechanisms that are poorly understood. The
prevailing paradigm is that maternal antimalarial antibodies transferred to the fetus in
the last trimester of pregnancy protect the infant from early infections. These
antimalarial antibodies wane by approximately 6 months of age leaving the infant
vulnerable to malaria, however direct evidence supporting this epidemiologically based
paradigm is lacking. As infants are the target population for future malaria vaccines,
understanding how they begin to develop immunity to malaria and the gaps in their
responses is key. This review summarizes the antimalarial antibody responses detected in
infants and how they change over time. We focus primarily on Pf antibody responses and
will briefly mention Plasmodium vivax responses in infants.
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Kangoye DT, Mensah VA, Murungi LM, Nkumama I, Nebie I, Marsh K, Cisse B, Bejon P, Osier FHA, Sirima SB. Dynamics and role of antibodies to Plasmodium falciparum merozoite antigens in children living in two settings with differing malaria transmission intensity. Vaccine 2015; 34:160-6. [PMID: 26541134 PMCID: PMC4683095 DOI: 10.1016/j.vaccine.2015.10.058] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Revised: 09/26/2015] [Accepted: 10/12/2015] [Indexed: 11/17/2022]
Abstract
BACKGROUND Young infants have reduced susceptibility to febrile malaria compared with older children, but the mechanism for this remains unclear. There are conflicting data on the role of passively acquired antibodies. Here, we examine antibody titres to merozoite surface antigens in the protection of children in their first two years of life in two settings with differing malaria transmission intensity and compare these titres to previously established protective thresholds. METHODS Two cohorts of children aged four to six weeks were recruited in Banfora, Burkina and Keur Soce, Senegal and followed up for two years. Malaria infections were detected by light microscopic examination of blood smears collected at active and passive case detection visits. The titres of antibodies to the Plasmodium falciparum recombinant merozoite proteins (AMA1-3D7, MSP1-19, MSP2-Dd2, and MSP3-3D7) were measured by enzyme-linked immunosorbent assay at 1-6, 9, 12, 15 and 18 months of age and compared with the protective thresholds established in Kenyan children. RESULTS Antibody titres were below the protective thresholds throughout the study period and we did not find any association with protection against febrile malaria. Antibodies to AMA1 and MSP1-19 appeared to be markers of exposure in the univariate analysis (and so associated with increasing risk) and adjusting for exposure reduced the strength and significance of this association. CONCLUSION The antibody levels we measured are unlikely to be responsible for the apparent protection against febrile malaria seen in young infants. Further work to identify protective antibody responses might include functional assays and a wider range of antigens.
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Affiliation(s)
- David Tiga Kangoye
- Centre National de Recherche et de Formation sur le Paludisme (CNRFP), 01 BP 2208, Ouagadougou 01, Burkina Faso; Kenya Medical Research Institute, Centre for Geographic Medicine Research Coast (KEMRI-CGMRC), P.O. Box 230, Kilifi 80108, Kenya.
| | | | - Linda Muthoni Murungi
- Kenya Medical Research Institute, Centre for Geographic Medicine Research Coast (KEMRI-CGMRC), P.O. Box 230, Kilifi 80108, Kenya
| | - Irene Nkumama
- Kenya Medical Research Institute, Centre for Geographic Medicine Research Coast (KEMRI-CGMRC), P.O. Box 230, Kilifi 80108, Kenya
| | - Issa Nebie
- Centre National de Recherche et de Formation sur le Paludisme (CNRFP), 01 BP 2208, Ouagadougou 01, Burkina Faso
| | - Kevin Marsh
- Kenya Medical Research Institute, Centre for Geographic Medicine Research Coast (KEMRI-CGMRC), P.O. Box 230, Kilifi 80108, Kenya; Nuffield Department of Medicine, Centre for Clinical Vaccinology and Tropical Medicine, University of Oxford, Churchill Hospital, Oxford, United Kingdom
| | - Badara Cisse
- Service de Parasitologie, Université Cheikh Anta Diop (UCAD), BP 5005 UCAD, Dakar, Senegal
| | - Philip Bejon
- Kenya Medical Research Institute, Centre for Geographic Medicine Research Coast (KEMRI-CGMRC), P.O. Box 230, Kilifi 80108, Kenya; Nuffield Department of Medicine, Centre for Clinical Vaccinology and Tropical Medicine, University of Oxford, Churchill Hospital, Oxford, United Kingdom
| | - Faith Hope Among'in Osier
- Kenya Medical Research Institute, Centre for Geographic Medicine Research Coast (KEMRI-CGMRC), P.O. Box 230, Kilifi 80108, Kenya
| | - Sodiomon Bienvenu Sirima
- Centre National de Recherche et de Formation sur le Paludisme (CNRFP), 01 BP 2208, Ouagadougou 01, Burkina Faso
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Elechi HA, Rabasa AI, Bashir MF, Gofama MM, Ibrahim HA, Askira UM. Uncomplicated malaria in children: The place of rapid diagnostic test. Niger Med J 2015; 56:85-90. [PMID: 25838621 PMCID: PMC4382610 DOI: 10.4103/0300-1652.150686] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Background: Malaria has remained a major cause of morbidity and mortality among the under-five children in Nigeria. Prompt and accurate diagnosis of malaria is necessary in controlling this high burden and preventing unnecessary use of anti-malarial drugs. Malaria rapid diagnostic test (MRDT) offers the hope of achieving this goal. However, the performance of these kits among the most vulnerable age group to malaria is inadequate. Materials and Methods: In this cross-sectional study, 433 out-patients, aged <5 years with fever or history of fever were enrolled. Each candidate was tested for malaria parasitaemia using ACON; malaria pf. Thick and thin films were also prepared from the same finger prick blood for each candidate. Result: Malaria rapid diagnostic test had sensitivity of 8.3%, specificity of 100%, positive predictive value (PPV) of 100% and negative predictive value (NPV) of 74%. The sensitivity of MRDT increased with increasing age. This effect of age on sensitivity was statistically significant (P = 0.007). Similarly parasite density had significant effect on the sensitivity of MRDT (P = <0.001). Conclusion: Histidine-rich protein-2 based MRDT is not a reliable mean of diagnosing malaria in the under-five age children with acute uncomplicated malaria.
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Affiliation(s)
| | - Adamu Ibrahim Rabasa
- Department of Paediatrics, Abubakar Tafawa Balewa University Teaching Hospital, Bauchi, Nigeria
| | - Muhammad Faruk Bashir
- Department of Paediatrics, Abubakar Tafawa Balewa University Teaching Hospital, Bauchi, Nigeria
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Kipanga PN, Omondi D, Mireji PO, Sawa P, Masiga DK, Villinger J. High-resolution melting analysis reveals low Plasmodium parasitaemia infections among microscopically negative febrile patients in western Kenya. Malar J 2014; 13:429. [PMID: 25399409 PMCID: PMC4246433 DOI: 10.1186/1475-2875-13-429] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Accepted: 11/05/2014] [Indexed: 01/28/2023] Open
Abstract
Background Microscopy and rapid diagnostic tests (RDTs) are common tools for diagnosing malaria, but are deficient in detecting low Plasmodium parasitaemia. A novel molecular diagnostic tool (nPCR-HRM) that combines the sensitivity and specificity of nested PCR (nPCR) and direct PCR-high resolution melting analysis (dPCR-HRM) was developed. To evaluate patterns of anti-malarial drug administration when no parasites are detected, nPCR-HRM was employed to screen blood samples for low parasitaemia from febrile patients without microscopically detectable Plasmodium infections in a rural malaria-endemic setting. Methods Blood samples (n = 197) were collected in two islands of Lake Victoria, Kenya, from febrile patients without Plasmodium detectable by microscopy or RDTs. 18S rRNA gene sequences were amplified from extracted DNA by nPCR-HRM, nPCR, and dPCR-HRM to detect and differentiate Plasmodium parasites. The limits of detection (LoD) were compared using serial dilutions of the WHO International Standard for P. falciparum DNA. Data on administration of anti-malarials were collected to estimate prescription of anti-malarial drugs to patients with and without low parasitaemia Plasmodium infections. Results The coupled nPCR-HRM assay detected Plasmodium parasites with greater sensitivity (LoD = 236 parasites/mL) than either nPCR (LoD = 4,700 parasites/mL) or dPCR-HRM (LoD = 1,490 parasites/mL). Moreover, nPCR-HRM detected and differentiated low-parasitaemia infections in significantly greater proportions of patients than did either nPCR or dPCR-HRM (p-value <0.001). Among these low-parasitaemia infections, 67.7% of patients were treated with anti-malarials, whereas 81.5% of patients not infected with Plasmodium parasites were treated with anti-malarials. Conclusions The enhanced sensitivity of nPCR-HRM demonstrates limitations of differential febrile illness diagnostics in rural malaria endemic settings that confound epidemiological estimates of malaria, and lead to inadvertent misadministration of anti-malarial drugs. This is the first study that employs low-parasitaemia Plasmodium diagnostics to quantify the prescription of anti-malarial drugs to both non-malaria febrile patients and patients with low-parasitaemia Plasmodium infections. nPCR-HRM enhances low-parasitaemia malaria diagnosis and can potentially surmount the deficiencies of microscopy and RDT-based results in determining low-parasitaemia Plasmodium infection rates for evaluating malaria elimination efforts. The findings highlight the need for improved differential diagnostics of febrile illness in remote malaria endemic regions.
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Affiliation(s)
| | | | | | | | | | - Jandouwe Villinger
- Martin Lüscher Emerging Infectious Diseases (ML-EID) Laboratory, Molecular Biology and Bioinformatics Unit, International Centre of Insect Physiology and Ecology (icipe), P,O, Box 30772, Nairobi 00100, Kenya.
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Afrane YA, Zhou G, Githeko AK, Yan G. Clinical malaria case definition and malaria attributable fraction in the highlands of western Kenya. Malar J 2014; 13:405. [PMID: 25318705 PMCID: PMC4209040 DOI: 10.1186/1475-2875-13-405] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Accepted: 09/27/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In African highland areas where endemicity of malaria varies greatly according to altitude and topography, parasitaemia accompanied by fever may not be sufficient to define an episode of clinical malaria in endemic areas. To evaluate the effectiveness of malaria interventions, age-specific case definitions of clinical malaria needs to be determined. Cases of clinical malaria through active case surveillance were quantified in a highland area in Kenya and defined clinical malaria for different age groups. METHODS A cohort of over 1,800 participants from all age groups was selected randomly from over 350 houses in 10 villages stratified by topography and followed for two-and-a-half years. Participants were visited every two weeks and screened for clinical malaria, defined as an individual with malaria-related symptoms (fever [axillary temperature≥37.5°C], chills, severe malaise, headache or vomiting) at the time of examination or 1-2 days prior to the examination in the presence of a Plasmodium falciparum positive blood smear. Individuals in the same cohort were screened for asymptomatic malaria infection during the low and high malaria transmission seasons. Parasite densities and temperature were used to define clinical malaria by age in the population. The proportion of fevers attributable to malaria was calculated using logistic regression models. RESULTS Incidence of clinical malaria was highest in valley bottom population (5.0% cases per 1,000 population per year) compared to mid-hill (2.2% cases per 1,000 population per year) and up-hill (1.1% cases per 1,000 population per year) populations. The optimum cut-off parasite densities through the determination of the sensitivity and specificity showed that in children less than five years of age, 500 parasites per μl of blood could be used to define the malaria attributable fever cases for this age group. In children between the ages of 5-14, a parasite density of 1,000 parasites per μl of blood could be used to define the malaria attributable fever cases. For individuals older than 14 years, the cut-off parasite density was 3,000 parasites per μl of blood. CONCLUSION Clinical malaria case definitions are affected by age and endemicity, which needs to be taken into consideration during evaluation of interventions.
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Affiliation(s)
- Yaw A Afrane
- Climate and Human Health Research Unit, Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya.
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No asymptomatic malaria parasitaemia found among 108 young children at one health facility in Dar es Salaam, Tanzania. Malar J 2013; 12:417. [PMID: 24228811 PMCID: PMC3830543 DOI: 10.1186/1475-2875-12-417] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Accepted: 11/12/2013] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND Asymptomatic malaria parasitaemia has been reported in areas with high malaria transmission. It may serve as a reservoir for continued transmission, and furthermore complicates diagnostics, as not all individuals with a positive malaria test are necessarily ill due to malaria, although they may present with malaria-like symptoms. Asymptomatic malaria increases with age as immunity to malaria gradually develops. As mortality and morbidity of malaria is higher among younger children it is important to know the prevalence of asymptomatic malaria parasitaemia in this population in order to interpret laboratory results for malaria correctly. METHODS A total of 108 children that had neither been treated for malaria nor had a fever the previous four weeks were recruited consecutively at a maternal and child health clinic (MCHC) in Dar es Salaam, Tanzania. A rapid diagnostic test (RDT) for malaria and dried blood spot (DBS) on filter paper were taken from each child. Social and clinical data were recorded. DNA was extracted from the DBS of study participants by a method using InstaGene™ matrix. PCR targeting the Plasmodium mitochondrial genome was performed on all samples. RESULTS Median age was 4.6 months (range 0.5-38). All the RDTs were negative. PCR was negative for all study subjects. CONCLUSION The study suggests that asymptomatic malaria may not be present in apparently healthy children up to the age of three years in Dar es Salaam, Tanzania. However, because of the small sample size and low median age of the study population, the findings cannot be generalized. Larger studies, including higher age groups, need to be done to clarify whether asymptomatic malaria parasitaemia is present in the general population in the Dar es Salaam area.
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Wilson PT, Malhotra I, Mungai P, King CL, Dent AE. Transplacentally transferred functional antibodies against Plasmodium falciparum decrease with age. Acta Trop 2013; 128:149-53. [PMID: 23911334 DOI: 10.1016/j.actatropica.2013.07.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2013] [Revised: 07/17/2013] [Accepted: 07/21/2013] [Indexed: 11/16/2022]
Abstract
Transplacental transfer of antibodies from clinically malaria immune pregnant women to their fetuses is thought to provide passive protection against malaria during infancy. However, the presences and duration of functional antibodies against Plasmodium falciparum (Pf) in newborns has not been described. We used growth inhibition assays (GIA) to measure total anti-malaria functional antibodies present at birth and over the following year. Samples were drawn from cord blood (n=86) and in infants at six and 12 months of life (n=86 and 65 respectively). Three laboratory Pf strains (D10, W2mef, 3D7) and a field isolate (Msambweni 2006) were used in the assays. Median (ranges) GIA levels for cord plasma differed between laboratory parasite strains: D10, 0% (0-81); W2mef, 6% (0-80); 3D7, 18% (0-88); Msambweni 2006, 6% (0-43) (P<0.001, Wilcoxon signed-rank test). GIA levels against all Pf strains were found to decline in infants from birth to six months (P<0.01, Wilcoxon, signed-rank test). Functional antibodies as measured by GIA are transferred to the fetus and wane in the infants over time. Infant protection from clinical malaria disease may in part be mediated by these functional anti-malaria antibodies.
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Affiliation(s)
- Patrick T Wilson
- Center for Global Health and Diseases, Case Western Reserve University, Cleveland, OH, USA.
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Alao MJ, Gbadoé AD, Meremikwu M, Tshefu A, Tiono AB, Cousin M, Hamed K. Plasmodium falciparum malaria in infants under 5 kg: retrospective surveillance of hospital records in five sub-saharan African countries. J Trop Pediatr 2013; 59:154-9. [PMID: 23243081 DOI: 10.1093/tropej/fms069] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE To investigate the disease burden, clinical features, treatment and outcomes of Plasmodium falciparum malaria in neonates and infants weighing <5 kg in five sub-Saharan African countries. METHODS Pediatric hospital records were retrospectively reviewed for relevant cases. Details of clinical features, treatment and clinical outcomes were collected, and a descriptive analysis of data was carried out. RESULTS The annual number of malaria cases ranged from 12 to 120 cases across hospitals and calendar years. The most frequent reason for seeking care was fever. Parasite density was low. Quinine was the most common treatment, followed by artemisinin-based combination therapy. The majority of patients recovered from their illness following treatment. CONCLUSION Plasmodium falciparum malaria exists in this subpopulation. Further epidemiological data are needed to estimate malaria morbidity and mortality in young infants. Moreover, clinical evidence on the efficacy and safety of artemisinin-based combination therapies in this subpopulation is warranted.
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Affiliation(s)
- Maroufou J Alao
- Service de Pédiatrie, Hôpital de la Mère et de l'Enfant Lagune, Cotonou 01 BP 107, Bénin
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Hendriksen ICE, White LJ, Veenemans J, Mtove G, Woodrow C, Amos B, Saiwaew S, Gesase S, Nadjm B, Silamut K, Joseph S, Chotivanich K, Day NPJ, von Seidlein L, Verhoef H, Reyburn H, White NJ, Dondorp AM. Defining falciparum-malaria-attributable severe febrile illness in moderate-to-high transmission settings on the basis of plasma PfHRP2 concentration. J Infect Dis 2013; 207:351-61. [PMID: 23136222 PMCID: PMC3532834 DOI: 10.1093/infdis/jis675] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Accepted: 08/23/2012] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND In malaria-endemic settings, asymptomatic parasitemia complicates the diagnosis of malaria. Histidine-rich protein 2 (HRP2) is produced by Plasmodium falciparum, and its plasma concentration reflects the total body parasite burden. We aimed to define the malaria-attributable fraction of severe febrile illness, using the distributions of plasma P. falciparum HRP2 (PfHRP2) concentrations from parasitemic children with different clinical presentations. METHODS Plasma samples were collected from and peripheral blood slides prepared for 1435 children aged 6-60 months in communities and a nearby hospital in northeastern Tanzania. The study population included children with severe or uncomplicated malaria, asymptomatic carriers, and healthy control subjects who had negative results of rapid diagnostic tests. The distributions of plasma PfHRP2 concentrations among the different groups were used to model severe malaria-attributable disease. RESULTS The plasma PfHRP2 concentration showed a close correlation with the severity of infection. PfHRP2 concentrations of >1000 ng/mL denoted a malaria-attributable fraction of severe disease of 99% (95% credible interval [CI], 96%-100%), with a sensitivity of 74% (95% CI, 72%-77%), whereas a concentration of <200 ng/mL denoted severe febrile illness of an alternative diagnosis in >10% (95% CI, 3%-27%) of patients. Bacteremia was more common among patients in the lowest and highest PfHRP2 concentration quintiles. CONCLUSIONS The plasma PfHRP2 concentration defines malaria-attributable disease and distinguishes severe malaria from coincidental parasitemia in African children in a moderate-to-high transmission setting.
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Affiliation(s)
- Ilse C E Hendriksen
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
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Kyu HH, Georgiades K, Shannon HS, Boyle MH. Evaluation of the association between long-lasting insecticidal nets mass distribution campaigns and child malaria in Nigeria. Malar J 2013; 12:14. [PMID: 23297758 PMCID: PMC3545742 DOI: 10.1186/1475-2875-12-14] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2012] [Accepted: 01/04/2013] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Nigeria carries the greatest malaria burden among countries in the world. As part of the National Malaria Control Strategic Plan, free long-lasting insecticidal nets (LLINs) were distributed in 14 states of Nigeria through mass campaigns led by different organizations (the World Bank, UNICEF, or the Global Fund) between May 2009 and August 2010. The objective of this study was to evaluate the association between LLIN distribution campaigns and child malaria in Nigeria. METHODS Data were from the Nigeria Malaria Indicator Survey which was carried out from October to December 2010 on a nationally representative sample of households. Participants were women aged 15-49 years and their children aged less than five years (N = 4082). The main outcome measure was the presence or absence of malaria parasites in blood samples of children (6-59 months). RESULTS Compared with children living in communities with no campaigns, those in the campaign areas were less likely to test positive for malaria after adjusting for geographic locations, community- and individual-level characteristics including child-level use of insecticide-treated nets (ITNs). The protective effects were statistically significant for the World Bank Booster Project areas (OR = 0.18, 95% CI = 0.04-0.73) but did not reach statistical significance for other campaign areas. Results also showed that community-level wealth (OR = 0.51, 95% CI = 0.34-0.76), community-level maternal knowledge regarding malaria prevention (OR = 0.70, 95% CI = 0.50-0.97), and child-level use of ITNs (OR = 0.79, 95% CI = 0.63-0.99) were negatively associated with child malaria. CONCLUSIONS The observed protective effects on child malaria of these campaigns (statistically significant in the World Bank Booster Project areas and non-significant in the other areas) need to be corroborated by future effectiveness studies. Results also show that improving community-level maternal knowledge through appropriate channels might be helpful in preventing child malaria in Nigeria.
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Affiliation(s)
- Hmwe Hmwe Kyu
- Department of Psychiatry and Behavioural Neurosciences, McMaster University and Offord Centre for Child Studies, Hamilton, ON, L8S 4K1, Canada
- Department of Clinical Epidemiology & Biostatistics, Faculty of Health Sciences, McMaster University, Hamilton, ON, L8S 4K1, Canada
| | - Katholiki Georgiades
- Department of Psychiatry and Behavioural Neurosciences, McMaster University and Offord Centre for Child Studies, Hamilton, ON, L8S 4K1, Canada
- Department of Clinical Epidemiology & Biostatistics, Faculty of Health Sciences, McMaster University, Hamilton, ON, L8S 4K1, Canada
| | - Harry S Shannon
- Department of Clinical Epidemiology & Biostatistics, Faculty of Health Sciences, McMaster University, Hamilton, ON, L8S 4K1, Canada
| | - Michael H Boyle
- Department of Psychiatry and Behavioural Neurosciences, McMaster University and Offord Centre for Child Studies, Hamilton, ON, L8S 4K1, Canada
- Department of Clinical Epidemiology & Biostatistics, Faculty of Health Sciences, McMaster University, Hamilton, ON, L8S 4K1, Canada
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Antonio-Nkondjio C, Defo-Talom B, Tagne-Fotso R, Tene-Fossog B, Ndo C, Lehman LG, Tchuinkam T, Kengne P, Awono-Ambene P. High mosquito burden and malaria transmission in a district of the city of Douala, Cameroon. BMC Infect Dis 2012; 12:275. [PMID: 23106909 PMCID: PMC3532071 DOI: 10.1186/1471-2334-12-275] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Accepted: 10/29/2012] [Indexed: 11/24/2022] Open
Abstract
Background Rapid demographic growth in Douala city, Cameroon, has resulted in profound ecological and environmental changes. Although demographic changes can affect anopheline mosquito breeding sites, there is a lack of understanding about the epidemiological impact that such changes might have on vector ecology and malaria transmission. Methods A 12-month entomological study was conducted in a highly populated district of Douala called Ndogpassi. Adult mosquitoes were collected using two methods: 1) human landing catches (HLC); and 2) Centers for Disease Control and Prevention (CDC) light traps; these methods were used twice monthly from January to December 2011. Mosquito genus and species were identified with morphological and molecular diagnostic tools. The sampling efficiency of the CDC light trap and HLC were compared. Anopheles gambiae infection with Plasmodium falciparum was detected using ELISA. Susceptibility to DDT, permethrin, and deltamethrin insecticides were also determined. Results A total of 6923 mosquitoes were collected by HLC (5198) and CDC light traps (1725). There was no equivalence in the sampling efficiency between light traps and human landing catches (P > 0.01). With 51% of the total, Culex was the most common, followed by Anopheles (26.14%), Mansonia (22.7%) and Aedes (0.1%). An. gambiae ss (M form) comprised ~98% of the total anophelines collected. An. gambiae had a biting rate of 0.25 to 49.25 bites per human per night, and was the only species found to be infected with P. falciparum. A P. falciparum infection rate of 0.5% was calculated (based on enzyme-linked immunosorbent assays using the circumsporozoite surface protein). The entomological inoculation rate was estimated at 31 infective bites per annum. Insecticide susceptibility tests on An. gambiae females revealed a mortality rate of 33%, 76% and 98% for DDT, permethrin and deltamethrin, respectively. The West African kdr allele (L1014F) was detected in 38 of the 61 An. gambiae analyzed (62.3%). Conclusions The present study revealed seasonal malaria transmission in Douala. High levels of An. gambiae were detected along with a high prevalence of insecticide resistance in this vector population. These findings highlight the need to promote use of insecticide-impregnated bed nets in Douala.
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Affiliation(s)
- Christophe Antonio-Nkondjio
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroun.
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Changing malaria epidemiology and diagnostic criteria for Plasmodium falciparum clinical malaria. PLoS One 2012; 7:e46188. [PMID: 23029433 PMCID: PMC3460864 DOI: 10.1371/journal.pone.0046188] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Accepted: 08/30/2012] [Indexed: 11/21/2022] Open
Abstract
Background In tropical Africa, where malaria is highly endemic, low grade infections are asymptomatic and the diagnosis of clinical malaria is usually based on parasite density. Here we investigate how changes in malaria control and endemicity modify diagnostic criteria of Plasmodium falciparum attacks. Methods and Findings Parasitological and clinical data from the population of Dielmo, Senegal, monitored during 20 years, are analyzed in a random-effect logistic regression model to investigate the relationship between the level of parasitemia and risk of fever. Between 1990 and 2010, P. falciparum prevalence in asymptomatic persons declined from 85% to 1% in children 0–3 years and from 34% to 2% in adults ≥50 years. Thresholds levels of parasitemia for attributing fever episodes to malaria decreased by steps in relation to control policies. Using baseline threshold during following periods underestimated P. falciparum attacks by 9.8–20.2% in children and 18.9–40.2% in adults. Considering all fever episodes associated with malaria parasites as clinical attacks overestimated P. falciparum attacks by 42.2–68.5% in children and 45.9–211.7% in adults. Conclusions Malaria control modifies in all age-groups the threshold levels of parasitemia to be used for the assessment of malaria morbidity and to guide therapeutic decisions. Even under declining levels of malaria endemicity, the parasite density method must remain the reference method for distinguishing malaria from other causes of fever and assessing trends in the burden of malaria.
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Diagnosis of Malaria Infection with or without Disease. Mediterr J Hematol Infect Dis 2012; 4:e2012036. [PMID: 22708051 PMCID: PMC3375766 DOI: 10.4084/mjhid.2012.036] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Accepted: 03/28/2012] [Indexed: 11/18/2022] Open
Abstract
The revised W.H.O. guidelines for malaria management in endemic countries recommend that treatment should be reserved to laboratory confirmed cases, both for adults and children. Currently the most widely used tools are rapid diagnostic tests (RDTs), that are accurate and reliable in diagnosing malaria infection. However, an infection is not necessarily a clinical malaria, and RDTs may give positive results in febrile patients who have another cause of fever. Excessive reliance on RDTs may cause overlooking potentially severe non malarial febrile illnesses (NMFI) in these cases. In countries or areas where transmission intensity remains very high, fever management in children (especially in the rainy season) should probably remain presumptive, as a test-based management may not be safe, nor cost effective. In contrast, in countries with low transmission, including those targeted for malaria elimination, RDTs are a key resource to limit unnecessary antimalarial prescription and to identify pockets of infected individuals. Research should focus on very sensitive tools for infection on one side, and on improved tools for clinical management on the other, including biomarkers of clinical malaria and/or of alternative causes of fever.
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Mannan I, Choi Y, Coutinho AJ, Chowdhury AI, Rahman SM, Seraji HR, Bari S, Shah R, Winch PJ, El Arifeen S, Darmstadt GL, Baqui AH. Vulnerability of newborns to environmental factors: findings from community based surveillance data in Bangladesh. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2011; 8:3437-52. [PMID: 21909316 PMCID: PMC3166752 DOI: 10.3390/ijerph8083437] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Revised: 08/12/2011] [Accepted: 08/16/2011] [Indexed: 11/17/2022]
Abstract
Infection is the major cause of neonatal deaths. Home born newborns in rural Bangladeshi communities are exposed to environmental factors increasing their vulnerability to a number of disease agents that may compromise their health. The current analysis was conducted to assess the association of very severe disease (VSD) in newborns in rural communities with temperature, rainfall, and humidity. A total of 12,836 newborns from rural Sylhet and Mirzapur communities were assessed by trained community health workers using a sign based algorithm. Records of temperature, humidity, and rainfall were collected from the nearest meteorological stations. Associations between VSD and environmental factors were estimated. Incidence of VSD was found to be associated with higher temperatures (odds ratios: 1.14, 95% CI: 1.08 to 1.21 in Sylhet and 1.06, 95% CI: 1.04 to 1.07 in Mirzapur) and heat humidity index (odds ratios: 1.06, 95% CI: 1.04 to 1.08 in Sylhet and, 1.03, 95% CI: 1.01 to 1.04 in Mirzapur). Four months (June–September) in Sylhet, and six months in Mirzapur (April–September) had higher odds ratios of incidence of VSD as compared to the remainder of the year (odds ratios: 1.72, 95% CI: 1.32 to 2.23 in Sylhet and, 1.62, 95% CI: 1.33 to 1.96 in Mirzapur). Prevention of VSD in neonates can be enhanced if these interactions are considered in health intervention strategies.
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Affiliation(s)
- Ishtiaq Mannan
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe Street, Suite E8138, Baltimore, MD 21205, USA; E-Mails: (Y.C.); (A.J.C.); (R.S.); (P.J.W.); (G.L.D.); (A.H.B.)
- Save the Children, H 1(A) 2, Road 91, Dhaka 1212, Bangladesh
- Author to whom correspondence should be addressed: E-Mail: ; Tel.: +88-01730327515
| | - Yoonjoung Choi
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe Street, Suite E8138, Baltimore, MD 21205, USA; E-Mails: (Y.C.); (A.J.C.); (R.S.); (P.J.W.); (G.L.D.); (A.H.B.)
| | - Anastasia J. Coutinho
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe Street, Suite E8138, Baltimore, MD 21205, USA; E-Mails: (Y.C.); (A.J.C.); (R.S.); (P.J.W.); (G.L.D.); (A.H.B.)
| | - Atique I. Chowdhury
- International Center for Diarrhoeal Disease Research, Bangladesh, Mohakhali, Dhaka 1212, Bangladesh; E-Mails: (A.I.C.); (S.M.R.); (H.R.S.); (S.B.); (S.E.A.)
| | - Syed Moshfiqur Rahman
- International Center for Diarrhoeal Disease Research, Bangladesh, Mohakhali, Dhaka 1212, Bangladesh; E-Mails: (A.I.C.); (S.M.R.); (H.R.S.); (S.B.); (S.E.A.)
| | - Habib R. Seraji
- International Center for Diarrhoeal Disease Research, Bangladesh, Mohakhali, Dhaka 1212, Bangladesh; E-Mails: (A.I.C.); (S.M.R.); (H.R.S.); (S.B.); (S.E.A.)
| | - Sanwarul Bari
- International Center for Diarrhoeal Disease Research, Bangladesh, Mohakhali, Dhaka 1212, Bangladesh; E-Mails: (A.I.C.); (S.M.R.); (H.R.S.); (S.B.); (S.E.A.)
| | - Rasheduzzaman Shah
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe Street, Suite E8138, Baltimore, MD 21205, USA; E-Mails: (Y.C.); (A.J.C.); (R.S.); (P.J.W.); (G.L.D.); (A.H.B.)
- International Center for Diarrhoeal Disease Research, Bangladesh, Mohakhali, Dhaka 1212, Bangladesh; E-Mails: (A.I.C.); (S.M.R.); (H.R.S.); (S.B.); (S.E.A.)
| | - Peter J. Winch
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe Street, Suite E8138, Baltimore, MD 21205, USA; E-Mails: (Y.C.); (A.J.C.); (R.S.); (P.J.W.); (G.L.D.); (A.H.B.)
| | - Shams El Arifeen
- International Center for Diarrhoeal Disease Research, Bangladesh, Mohakhali, Dhaka 1212, Bangladesh; E-Mails: (A.I.C.); (S.M.R.); (H.R.S.); (S.B.); (S.E.A.)
| | - Gary L. Darmstadt
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe Street, Suite E8138, Baltimore, MD 21205, USA; E-Mails: (Y.C.); (A.J.C.); (R.S.); (P.J.W.); (G.L.D.); (A.H.B.)
| | - Abdullah H. Baqui
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe Street, Suite E8138, Baltimore, MD 21205, USA; E-Mails: (Y.C.); (A.J.C.); (R.S.); (P.J.W.); (G.L.D.); (A.H.B.)
- International Center for Diarrhoeal Disease Research, Bangladesh, Mohakhali, Dhaka 1212, Bangladesh; E-Mails: (A.I.C.); (S.M.R.); (H.R.S.); (S.B.); (S.E.A.)
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Leach A, Vekemans J, Lievens M, Ofori-Anyinam O, Cahill C, Owusu-Agyei S, Abdulla S, Macete E, Njuguna P, Savarese B, Loucq C, Ballou WR. Design of a phase III multicenter trial to evaluate the efficacy of the RTS,S/AS01 malaria vaccine in children across diverse transmission settings in Africa. Malar J 2011; 10:224. [PMID: 21816029 PMCID: PMC3199907 DOI: 10.1186/1475-2875-10-224] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2011] [Accepted: 08/04/2011] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND GlaxoSmithKline Biologicals and the PATH Malaria Vaccine Initiative are working in partnership to develop a malaria vaccine to protect infants and children living in malaria endemic regions of sub-Saharan Africa, which can be delivered through the Expanded Programme on Immunization. The RTS,S/AS candidate vaccine has been evaluated in multiple phase I/II studies and shown to have a favourable safety profile and to be well-tolerated in both adults and children. This paper details the design of the phase III multicentre efficacy trial of the RTS,S/AS01 malaria vaccine candidate, which is pivotal for licensure and policy decision-making. METHODS The phase III trial is a randomized, controlled, multicentre, participant- and observer-blind study on-going in 11 centres associated with different malaria transmission settings in seven countries in sub-Saharan Africa. A minimum of 6,000 children in each of two age categories (6-12 weeks, 5-17 months) have been enrolled. Children were randomized 1:1:1 to one of three study groups: (1) primary vaccination with RTS,S/AS01 and booster dose of RTS,S/AS01; (2) primary vaccination with RTS,S/AS01 and a control vaccine at time of booster; (3) primary vaccination with control vaccine and a control vaccine at time of booster. Primary vaccination comprises three doses at monthly intervals; the booster dose is administered at 18 months post-primary course. Subjects will be followed to study month 32. The co-primary objectives are the evaluation of efficacy over one year post-dose 3 against clinical malaria when primary immunization is delivered at: (1) 6-12 weeks of age, with co-administration of DTPwHepB/Hib antigens and OPV; (2) 5-17 months of age. Secondary objectives include evaluation of vaccine efficacy against severe malaria, anaemia, malaria hospitalization, fatal malaria, all-cause mortality and other serious illnesses including sepsis and pneumonia. Efficacy of the vaccine against clinical malaria under different transmission settings, the evolution of efficacy over time and the potential benefit of a booster will be evaluated. In addition, the effect of RTS,S/AS01 vaccination on growth, and the safety and immunogenicity in HIV-infected and malnourished children will be assessed. Safety of the primary course of immunization and the booster dose will be documented in both age categories. CONCLUSIONS This pivotal phase III study of the RTS,S/AS01 candidate malaria vaccine in African children was designed and implemented by the Clinical Trials Partnership Committee. The study will provide efficacy and safety data to fulfil regulatory requirements, together with data on a broad range of endpoints that will facilitate the evaluation of the public health impact of the vaccine and will aid policy and implementation decisions. TRIAL REGISTRATION Clinicaltrials.gov NCT00866619.
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Affiliation(s)
| | | | | | | | | | - Seth Owusu-Agyei
- Kintampo Health Research Centre, Ghana Health Service, Kintampo, Ghana
| | | | - Eusebio Macete
- Centro de Investigação em Saude de Manhiça, Manhiça, Mozambique
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Abstract
BACKGROUND Each year, malaria threatens 125 million pregnancies, and gestational malaria is responsible for up to 200,000 infant deaths in sub-Saharan Africa. With advancing knowledge of malaria in pregnancy and its impact on newborns, improved preventive and therapeutic interventions are possible. METHODS We reviewed and, by consensus, evaluated published literature relevant to malaria and newborns. Important findings are summarised. RESULTS Pregnant women are more likely than others to be inoculated with and infected by malaria parasites. Poor outcomes are particularly common in primigravid women and their offspring. The placenta is affected through cellular adhesion, cytokine production and mononuclear cell infiltrates. As a result, newborns may have low birthweight owing to intrauterine growth retardation or prematurity. Recent evidence suggests that a subset of these infants is also at higher risk of malaria infections later in life. Preventive strategies to improve maternal and fetal outcomes include intermittent preventive treatment and insecticide-treated bed nets. Asymptomatic malaria infection is not uncommon in newborns, and symptomatic disease occurs. Fever and death are possible during the early days of life, and presentation with a sepsis-like illness can occur during the 1st 2 months of life. Malaria-affected infants face higher than usual risks of infantile anaemia, subsequent malaria infection and death during the 1st year of life. CONCLUSIONS Malaria is common during pregnancy and can have serious consequences for neonatal health. Neonatal morbidity and mortality can be significantly reduced by proper implementation of insecticide-treated nets and intermittent preventive treatment.
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Affiliation(s)
- T K Hartman
- Floating Hospital for Children at Tufts Medical Center, Boston, MA, USA
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Efficacy and safety of mefloquine, artesunate, mefloquine–artesunate, tribendimidine, and praziquantel in patients with Opisthorchis viverrini: a randomised, exploratory, open-label, phase 2 trial. THE LANCET. INFECTIOUS DISEASES 2011; 11:110-8. [DOI: 10.1016/s1473-3099(10)70250-4] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Damien GB, Djènontin A, Rogier C, Corbel V, Bangana SB, Chandre F, Akogbéto M, Kindé-Gazard D, Massougbodji A, Henry MC. Malaria infection and disease in an area with pyrethroid-resistant vectors in southern Benin. Malar J 2010; 9:380. [PMID: 21194470 PMCID: PMC3224346 DOI: 10.1186/1475-2875-9-380] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2010] [Accepted: 12/31/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND This study aimed to investigate baseline data on malaria before the evaluation of new vector control strategies in an area of pyrethroid-resistance of vectors. The burden of malaria was estimated in terms of infection (prevalence and parasite density) and of clinical episodes. METHODS Between December 2007 and December 2008 in the health district of Ouidah-Kpomassè-Tori Bossito (southern Benin), a descriptive epidemiological survey of malaria was conducted. From 28 selected villages, seven were randomized from which a total of 440 children aged 0 to 5 years were randomly selected. Clinical and parasitological information was obtained by active case detection of malaria episodes carried out during eight periods of six consecutive days scheduled at six weekly intervals and by cross-sectional surveys of asymptomatic infection. Entomological information was also collected. The ownership, the use and the correct use of long-lasting insecticide-treated nets (LLINs) were checked over weekly-survey by unannounced visits at home in the late evening. RESULTS Mean parasite density in asymptomatic children was 586 P. falciparum asexual forms per μL of blood (95%CI 504-680). Pyrogenic parasite cut-off was estimated 2,000 P. falciparum asexual blood forms per μL. The clinical incidence of malaria was 1.5 episodes per child per year (95%CI 1.2-1.9). Parasitological and clinical variables did not vary with season. Anopheles gambiae s.l. was the principal vector closely followed by Anopheles funestus. Entomological inoculation rate was 5.3 (95%CI 1.1-25.9) infective bites per human per year. Frequency of the L1014F kdr (West) allele was around 50%. Annual prevalence rate of Plasmodium falciparum asymptomatic infection was 21.8% (95%CI 19.1-24.4) and increased according to age. Mean rates of ownership and use of LLINs were 92% and 70% respectively. The only correct use of LLINs (63%) conferred 26% individual protection against only infection (OR = 0.74 (95%IC 0.62-0.87), p = 0.005). CONCLUSION The health district of Ouidah-Kpomassè-Tori Bossito is a mesoendemic area with a moderate level of pyrethroid-resistance of vectors. The used LLINs rate was high and only the correct use of LLINs was found to reduce malaria infection without influencing malaria morbidity.
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Affiliation(s)
- Georgia B Damien
- Centre de Recherche Entomologique de Cotonou (CREC), 06 BP 2604 Cotonou, Bénin.
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Olotu A, Fegan G, Williams TN, Sasi P, Ogada E, Bauni E, Wambua J, Marsh K, Borrmann S, Bejon P. Defining clinical malaria: the specificity and incidence of endpoints from active and passive surveillance of children in rural Kenya. PLoS One 2010; 5:e15569. [PMID: 21179571 PMCID: PMC3002959 DOI: 10.1371/journal.pone.0015569] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2010] [Accepted: 11/14/2010] [Indexed: 11/21/2022] Open
Abstract
Background Febrile malaria is the most common clinical manifestation of P. falciparum infection, and is often the primary endpoint in clinical trials and epidemiological studies. Subjective and objective fevers are both used to define the endpoint, but have not been carefully compared, and the relative incidence of clinical malaria by active and passive case detection is unknown. Methods We analyzed data from cohorts under active and passive surveillance, including 19,462 presentations with fever and 5,551 blood tests for asymptomatic parasitaemia. A logistic regression model was used to calculate Malaria Attributable Fractions (MAFs) for various case definitions. Incidences of febrile malaria by active and passive surveillance were compared in a subset of children matched for age and location. Results Active surveillance identified three times the incidence of clinical malaria as passive surveillance in a subset of children matched for age and location. Objective fever (temperature≥37.5°C) gave consistently higher MAFs than case definitions based on subjective fever. Conclusion The endpoints from active and passive surveillance have high specificity, but the incidence of endpoints is lower on passive surveillance. Subjective fever had low specificity and should not be used in primary endpoint. Passive surveillance will reduce the power of clinical trials but may cost-effectively deliver acceptable sensitivity in studies of large populations.
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Affiliation(s)
- Ally Olotu
- Kenya Medical Research Institute/Wellcome Trust Research Programme, Centre for Geographic Medicine Research, Kilifi, Kenya.
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Bisoffi Z, Sirima SB, Menten J, Pattaro C, Angheben A, Gobbi F, Tinto H, Lodesani C, Neya B, Gobbo M, Van den Ende J. Accuracy of a rapid diagnostic test on the diagnosis of malaria infection and of malaria-attributable fever during low and high transmission season in Burkina Faso. Malar J 2010; 9:192. [PMID: 20609211 PMCID: PMC2914059 DOI: 10.1186/1475-2875-9-192] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2010] [Accepted: 07/07/2010] [Indexed: 11/10/2022] Open
Abstract
Background Malaria management policies currently recommend that the treatment should only be administered after laboratory confirmation. Where microscopy is not available, rapid diagnostic tests (RDTs) are the usual alternative. Conclusive evidence is still lacking on the safety of a test-based strategy for children. Moreover, no formal attempt has been made to estimate RDTs accuracy on malaria-attributable fever. This study aims at estimating the accuracy of a RDT for the diagnosis of both malaria infection and malaria - attributable fever, in a region of Burkina Faso with a typically seasonal malaria transmission pattern. Methods Cross-sectional study. Subjects: all patients aged > 6 months consulting during the study periods. Gold standard for the diagnosis of malaria infection was microscopy. Gold standard for malaria-attributable fever was the number of fevers attributable to malaria, estimated by comparing parasite densities of febrile versus non-febrile subjects. Exclusion criteria: severe clinical condition needing urgent care. Results In the dry season, 186/852 patients with fever (22%) and 213/1,382 patients without fever (15%) had a Plasmodium falciparum infection. In the rainy season, this proportion was 841/1,317 (64%) and 623/1,669 (37%), respectively. The attributable fraction of fever to malaria was 11% and 69%, respectively. The RDT was positive in 113/400 (28.3%) fever cases in the dry season, and in 443/650 (68.2%) in the rainy season. In the dry season, the RDT sensitivity and specificity for malaria infection were 86% and 90% respectively. In the rainy season they were 94% and 78% respectively. In the dry season, the RDT sensitivity and specificity for malaria-attributable fever were 94% and 75%, the positive predictive value (PPV) was 9% and the negative predictive value (NPV) was 99.8%. In the rainy season the test sensitivity for malaria-attributable fever was 97% and specificity was 55%. The PPV ranged from 38% for adults to 82% for infants, while the NPV ranged from 84% for infants to over 99% for adults. Conclusions In the dry season the RDT has a low positive predictive value, but a very high negative predictive value for malaria-attributable fever. In the rainy season the negative test safely excludes malaria in adults but not in children.
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Affiliation(s)
- Zeno Bisoffi
- Centre for Tropical Diseases, S, Cuore Hospital, 37024 Negrar, Verona, Italy.
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Okiro EA, Snow RW. The relationship between reported fever and Plasmodium falciparum infection in African children. Malar J 2010; 9:99. [PMID: 20398428 PMCID: PMC2867992 DOI: 10.1186/1475-2875-9-99] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2010] [Accepted: 04/19/2010] [Indexed: 11/15/2022] Open
Abstract
Background Fever has traditionally served as the entry point for presumptive treatment of malaria in African children. However, recent changes in the epidemiology of malaria across many places in Africa would suggest that the predictive accuracy of a fever history as a marker of disease has changed prompting calls for the change to diagnosis-based treatment strategies. Methods Using data from six national malaria indicator surveys undertaken between 2007 and 2009, the relationship between childhood (6-59 months) reported fever on the day of survey and the likelihood of coincidental Plasmodium falciparum infection recorded using a rapid diagnostic test was evaluated across a range of endemicities characteristic of Africa today. Results Of 16,903 children surveyed, 3% were febrile and infected, 9% were febrile without infection, 12% were infected but were not febrile and 76% were uninfected and not febrile. Children with fever on the day of the survey had a 1.98 times greater chance of being infected with P. falciparum compared to children without a history of fever on the day of the survey after adjusting for age and location (OR 1.98; 95% CI 1.74-2.34). There was a strong linear relationship between the percentage of febrile children with infection and infection prevalence (R2 = 0.9147). The prevalence of infection in reported fevers was consistently greater than would be expected solely by chance and this increased with increasing transmission intensity. The data suggest that in areas where community-based infection prevalence in childhood is above 34-37%, 50% or more of fevers are likely to be associated with infection. Conclusion The potential benefits of diagnosis will depend on the prevalence of infection among children who report fever. The study has demonstrated a predictable relationship between parasite prevalence in the community and risks of infection among febrile children suggesting that current maps of parasite prevalence could be used to guide diagnostic strategies in Africa.
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Affiliation(s)
- Emelda A Okiro
- Malaria Public Health & Epidemiology Group, Centre for Geographic Medicine Research - Coast, Kenya Medical Research Institute/Wellcome Trust Research Programme, PO Box 43640, 00100 GPO, Nairobi, Kenya.
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Carneiro I, Roca-Feltrer A, Griffin JT, Smith L, Tanner M, Schellenberg JA, Greenwood B, Schellenberg D. Age-patterns of malaria vary with severity, transmission intensity and seasonality in sub-Saharan Africa: a systematic review and pooled analysis. PLoS One 2010; 5:e8988. [PMID: 20126547 PMCID: PMC2813874 DOI: 10.1371/journal.pone.0008988] [Citation(s) in RCA: 203] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2009] [Accepted: 01/06/2010] [Indexed: 11/19/2022] Open
Abstract
Background There is evidence that the age-pattern of Plasmodium falciparum malaria varies with transmission intensity. A better understanding of how this varies with the severity of outcome and across a range of transmission settings could enable locally appropriate targeting of interventions to those most at risk. We have, therefore, undertaken a pooled analysis of existing data from multiple sites to enable a comprehensive overview of the age-patterns of malaria outcomes under different epidemiological conditions in sub-Saharan Africa. Methodology/Principal Findings A systematic review using PubMed and CAB Abstracts (1980–2005), contacts with experts and searching bibliographies identified epidemiological studies with data on the age distribution of children with P. falciparum clinical malaria, hospital admissions with malaria and malaria-diagnosed mortality. Studies were allocated to a 3×2 matrix of intensity and seasonality of malaria transmission. Maximum likelihood methods were used to fit five continuous probability distributions to the percentage of each outcome by age for each of the six transmission scenarios. The best-fitting distributions are presented graphically, together with the estimated median age for each outcome. Clinical malaria incidence was relatively evenly distributed across the first 10 years of life for all transmission scenarios. Hospital admissions with malaria were more concentrated in younger children, with this effect being even more pronounced for malaria-diagnosed deaths. For all outcomes, the burden of malaria shifted towards younger ages with increasing transmission intensity, although marked seasonality moderated this effect. Conclusions The most severe consequences of P. falciparum malaria were concentrated in the youngest age groups across all settings. Despite recently observed declines in malaria transmission in several countries, which will shift the burden of malaria cases towards older children, it is still appropriate to target strategies for preventing malaria mortality and severe morbidity at very young children who will continue to bear the brunt of malaria deaths in Sub-Saharan Africa.
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Affiliation(s)
- Ilona Carneiro
- Disease Control and Vector Biology Unit, Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom.
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Mmbando BP, Lusingu JP, Vestergaard LS, Lemnge MM, Theander TG, Scheike TH. Parasite threshold associated with clinical malaria in areas of different transmission intensities in north eastern Tanzania. BMC Med Res Methodol 2009; 9:75. [PMID: 19909523 PMCID: PMC2781814 DOI: 10.1186/1471-2288-9-75] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2009] [Accepted: 11/12/2009] [Indexed: 11/21/2022] Open
Abstract
Background In Sub-Sahara Africa, malaria due to Plasmodium falciparum is the main cause of ill health. Evaluation of malaria interventions, such as drugs and vaccines depends on clinical definition of the disease, which is still a challenge due to lack of distinct malaria specific clinical features. Parasite threshold is used in definition of clinical malaria in evaluation of interventions. This however, is likely to be influenced by other factors such as transmission intensity as well as individual level of immunity against malaria. Methods This paper describes step function and dose response model with threshold parameter as a tool for estimation of parasite threshold for onset of malaria fever in highlands (low transmission) and lowlands (high transmission intensity) strata. These models were fitted using logistic regression stratified by strata and age groups (0-1, 2-3, 4-5, 6-9, and 10-19 years). Dose response model was further extended to fit all age groups combined in each stratum. Sub-sampling bootstrap was used to compute confidence intervals. Cross-sectional and passive case detection data from Korogwe district, north eastern Tanzania were used. Results Dose response model was better in the estimation of parasite thresholds. Parasite thresholds (scale = log parasite/μL) were high in lowlands than in highlands. In the lowlands, children in age group 4-5 years had the highest parasite threshold (8.73) while individuals aged 10-19 years had the lowest (6.81). In the highlands, children aged 0-1 years had the highest threshold (7.12) and those aged 10-19 years had the lowest (4.62). Regression analysis with all ages combined showed similar pattern of thresholds in both strata, whereby, in the lowlands the threshold was highest in age group 2-5 years and lowest in older individuals, while in the highlands was highest in age group 0-1 and decreased with increased age. The sensitivity of parasite threshold by age group ranged from 64%-74% in the lowlands and 67%-97% in the highlands; while specificity ranged between 67%-90% in the lowlands and 37%-73% in the highlands. Conclusion Dose response model with threshold parameter can be used to estimate parasite threshold associated with malaria fever onset. Parasite threshold were lower in older individuals and in low malaria transmission area.
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Affiliation(s)
- Bruno P Mmbando
- Department of Biostatistics, University of Copenhagen, Copenhagen, Denmark.
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O'Meara WP, Lang T. Malaria vaccine trial endpoints - bridging the gaps between trial design, public health and the next generation of vaccines. Parasite Immunol 2009; 31:574-81. [PMID: 19691560 DOI: 10.1111/j.1365-3024.2009.01144.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A recent working group convened by the World Health Organization recommended that time to first or only episode of clinical malaria should be used to evaluate vaccine efficacy in phase III trials. However, calculating vaccine efficacy based on this endpoint misses important aspects of malaria disease and transmission. Here, we discuss the gaps that this approach leaves in predicting the potential public health impact of a vaccine and the challenges faced by vaccine trial designers. We examine the implications of current vaccine trial design on effectiveness studies and the next generation of malaria vaccines.
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Affiliation(s)
- W P O'Meara
- Fogarty International Center, National Institutes of Health, Bethesda, MD, USA.
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Okafor UH, Oguonu T, Onah HE. Risk factors associated with congenital malaria in Enugu, South Eastern Nigeria. J OBSTET GYNAECOL 2009; 26:612-6. [PMID: 17071423 DOI: 10.1080/09638280600902893] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
There is paucity of data on the risk factors associated with congenital malaria in Nigeria. This study assessed the risk factors for congenital malaria in a population of neonates delivered at the University of Nigeria Teaching Hospital, Enugu, South Eastern Nigeria. It was a prospective cross-sectional study of neonates who were delivered in the institution from 2 April 2003 to 15 April 2004 as well as their mothers. Thick and thin blood films were made from maternal, baby and cord blood as well as the placenta for each mother/baby pair to determine malaria parasite density counts and for species identification. The maternal samples were obtained as soon as labour was confirmed while the cord and baby's blood as well as placental smears were taken within 1 h of delivery. Data analysis was by means of descriptive and inferential statistics as well as univariate and multivariate logistic regression at the 95% confidence level using the statistical software SPSS for Windows Version 10. A total of 658 mother/baby pairs were recruited into the study within the 13-month period. Out of this number, 625 mother/baby pairs completed the study and their data were subsequently analysed. A total of 356 (56.96%) mothers and 203 (32.48%) babies were smear positive for Plasmodium falciparum. On univariate logistic regression with presence or absence of the congenital malaria as the dependent variable, six out of the 13 putative risk factors tested were statistically significant. These were low compared with higher socioeconomic classes (OR = 1.41, 95% CI = 1.18 - 1.69, p = 0.00); low compared with normal birth weight (OR = 2.14, 95% CI = 1.39 - 3.30, p = 0.001); positive placental malaria parasitaemia (OR = 6.29, 95% CI, 4.73 - 8.37, p = 0.000), positive maternal blood malaria parasitaemia (OR = 5.04, 95% CI = 3.74 - 6.78, p = 0.000), positive cord blood malaria parasitaemia (OR = 26.87, 95% = 15.79 - 45.74, p = 0.000) and parity of 0 - 1 compared with other parities (OR = 1.31, 95% CI = 1.11 - 1.55, p = 0.002). On multivariate logistic regression, three of the six factors that were significant on univariate logistic regression remained significant. These were: positive placental malaria parasitaemia (OR = 2.55, 95% CI = 1.45 - 4.47, p = 0.001); positive cord malaria parasitaemia (OR = 18.90, 95% CI = 10.68 - 33.46, p = 0.000 and parity of 0 - 1 compared with other parities (OR = 1.66, 95% CI = 1.09 - 2.52, p = 0.02). It was concluded that the risk factors for congenital malaria identified in this study emphasise the need for effective preventive and curative treatment of malaria not only during pregnancy but also during delivery in malaria endemic areas. Additionally, congenital malaria should now rank high among the list of differential diagnosis of fever in the newborn in such endemic areas.
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Affiliation(s)
- U H Okafor
- Department of Paediatrics, University of Nigeria Teaching Hospital, Enugu, Nigeria.
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Mabunda S, Aponte JJ, Tiago A, Alonso P. A country-wide malaria survey in Mozambique. II. Malaria attributable proportion of fever and establishment of malaria case definition in children across different epidemiological settings. Malar J 2009; 8:74. [PMID: 19383126 PMCID: PMC2678146 DOI: 10.1186/1475-2875-8-74] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Accepted: 04/21/2009] [Indexed: 11/20/2022] Open
Abstract
Background Protection against clinical malaria episodes is acquired slowly after frequent exposure to malaria parasites. This is reflected by a decrease with increasing age in both parasite density and incidence of clinical episodes. In many settings of stable malaria transmission, the presence of asymptomatic malaria parasite carriers is common and the definition of clinical malaria remains uncertain. Methods Between February 2002 and April 2003, a country-wide malaria survey was conducted in 24 districts of Mozambique, aiming to characterize the malaria transmission intensities and to estimate the proportion of fever cases attributable to malaria infections in order to establish the malaria case definition. A total of 8,816 children less than ten years of age were selected for the study. Axillary temperature was measured in all participating subjects and finger prick blood collections were taken to prepare thick and thin films for identification of parasite species and determination of parasite density. The proportion of fever cases attributable to malaria infection was estimated using a logistic regression of the fever on a monotonic function of the parasite density and, using bootstrap facilities, bootstrapped estimated confidence intervals, as well as the sensitivity and specificity for different parasite density cut-offs were produced. Results Overall, the prevalence of Plasmodium falciparum was 52.4% (4,616/8,816). The prevalence of fever (axillary temperature ≥ 37.5°C) was 9.4% (766/8,816). Fever episodes peaked among children below 12 months of life [15.1% (206/1,517)]. The lowest fever prevalence of 5.9% (67/1,224) was recorded amongst children between five and seven years of age. Among 4,098 parasitized children, 498/4,098 (13.02%) had fever. The prevalence of malaria infections associated with fever peaked among children in the less than twelve months age group and thereafter decreased rapidly with increasing age (p < 0.001). High parasite densities were significantly associated with fever (p < 0.04). The proportion of fever attributed to malaria was 37.8% (95% CI 32.9% – 42.7%). An age-specific pattern was observed with significant variations across different regions in the country. In general, among children less than 12 months of life, the proportion of fever attributed to malaria infection was 43.5% (95% CI 25.8% – 61.2%), in children aged between 12 and 59 months of age was 39.6% (95% CI 30.3% – 48.9%), and among children aged between 5 and 10 years old was 21.5% (95% CI 11.6% – 31.4%). Conclusion This study confirms that malaria remains a major cause of febrile illness during childhood. It also defines the relation between parasite density and fever and how this varies with age and region. This may help guide case definition for clinical trials of preventive tools, as well as provide definitions that may improve the precision of measurement of the burden of disease.
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Ndounga M, Casimiro PN, Miakassissa-Mpassi V, Loumouamou D, Ntoumi F, Basco LK. [Malaria in health centres in the southern districts of Brazzaville, Congo]. ACTA ACUST UNITED AC 2008; 101:329-35. [PMID: 18956816 DOI: 10.3185/pathexo3111] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
During the surveys on antimalarial drug efficacy carried out from 2003 to 2006, we systematically checked the presence of Plasmodium falciparum in patients consulting in two health centres located in the south of Brazzaville. The first centre is situated in the urban zone; the second, in the semi rural area. The objective of this survey was to determine the prevalence of malaria-infected patients among the consulting patients and the prevalence of symptomatic patients with acute malaria attacks based on the parasitic density. Patients with parasites were assigned to one of the 5 following classifications: <2000, > or =2000, <5000, > or =5000 and > or =10,000 asexual parasites/microl of blood. Based on the threshold of parasite density 10,000 asexual parasites/microl, 10% and 24% of febrile patients in Tenrikyo and Madibou health centres were diagnosed as cases of malaria, respectively; 13.6% and 26.8% of patients under 5 years old consulting in these two health centres had malaria attacks. If the threshold of parasite density is lowered to 2000 asexual parasites/microl for patients > or =15 years old, 8% and 14% of adults in Tenrikyo and Madibou had malaria attacks, respectively The malaria burden was higher in the periphery of the city of Brazzaville than in the urbanized central districts. The Madibou health centre located in semi rural zone receives twice as many malaria cases for consultation than Tenrikyo located in the urban zone.
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Affiliation(s)
- M Ndounga
- Centre d'études sur les ressources végétales, BP 1249, Brazzaville, Congo.
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Le Port A, Cot M, Etard JF, Gaye O, Migot-Nabias F, Garcia A. Relation between Plasmodium falciparum asymptomatic infection and malaria attacks in a cohort of Senegalese children. Malar J 2008; 7:193. [PMID: 18823542 PMCID: PMC2567330 DOI: 10.1186/1475-2875-7-193] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2008] [Accepted: 09/29/2008] [Indexed: 11/25/2022] Open
Abstract
Background It is important to establish whether or not the presence of malaria parasites in peripheral blood of asymptomatic individuals is a predictor of future clinical mild malaria attacks (MMA). The aim of this study was to determine how an asymptomatic positive thick blood smear could be related to the occurrence of a MMA during the nine following days. Methods The study was conducted in a cohort of 569 Senegalese children, who were investigated for Plasmodium falciparum asymptomatic carriage at two different times of the transmission season, the beginning (September) and the end (November). The occurrence of MMA was investigated in asymptomatic carriers and non-carriers, every three days for nine consecutive days. Survival analysis was performed and risk estimates were calculated by Cox proportional hazards model. Results At the beginning of the transmission season, 27.8% (147/529) of the children were asymptomatic carriers (ACs) and 5.4% (8/147) of MMA occurred among these, versus 1% (4/382) among non-carriers (RR = 5.32; IC = [1.56–18.15], p = 0.008). At the end of the transmission season, the frequency of asymptomatic carriers was similar to that observed at the beginning of the season (31.9%, p = 0.15), but no MMA was detected during this period. Conclusion A significant association between P. falciparum asymptomatic carriage and the occurrence of MMA at the beginning of the transmission season was demonstrated, with a five-fold increase in the risk of developing a MMA in ACs. In the context of a possible distribution of IPTc in the future, drug strategies may have dramatic consequences due to the existence of ACs (both long term and short term), as they seem to play an important role in the individual protection to malaria, in the most exposed age groups.
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Affiliation(s)
- Agnès Le Port
- Institut de Recherche pour le Développement (IRD), Unité de Recherche 010: Santé de la mère et de l'enfant en milieu tropical, Laboratoire de Parasitologie, Faculté de Pharmacie, 4 avenue de l'Observatoire, 75006 Paris, France.
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Roca-Feltrer A, Carneiro I, Armstrong Schellenberg JRM. Estimates of the burden of malaria morbidity in Africa in children under the age of 5 years. Trop Med Int Health 2008; 13:771-83. [PMID: 18363586 DOI: 10.1111/j.1365-3156.2008.02076.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVE To estimate the direct burden of malaria among children younger than 5 years in sub-Saharan Africa (SSA) for the year 2000, as part of a wider initiative on burden estimates. METHODS A systematic literature review was undertaken in June 2003. Severe malaria outcomes (cerebral malaria, severe malarial anaemia and respiratory distress) and non-severe malaria data were abstracted separately, together with information on the characteristics of each study and its population. Population characteristics were also collated at a national level. A meta-regression model was used to predict the incidence of malaria fevers at a national level. For severe outcomes, results were presented as median rates as data were too sparse for modelling. RESULTS For the year 2000, an estimated 545,000 (uncertainty interval: 105,000-1,750,000) children under the age of 5 in SSA experienced an episode of severe malaria for which they were admitted to hospital. A total of 24,000 (interquartile range: 12,000-37,000) suffered from persistent neurological deficits as a result of cerebral malaria. The number of malaria fevers associated with high parasite density in under-5s in SSA in 2000 was estimated as 115,750,000 (uncertainty interval: 91,243,000-257,957,000). CONCLUSION Our study predicts a lower burden than previous estimates of under-5 malaria morbidity in SSA. As there is a lack of suitable data to enable comprehensive estimates of annual malaria incidence, we describe the information needed to improve the validity of future estimates.
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Affiliation(s)
- Arantxa Roca-Feltrer
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK.
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Koram KA, Molyneux ME. When Is “Malaria” Malaria? The Different Burdens of Malaria Infection, Malaria Disease, and Malaria-Like Illnesses. Am J Trop Med Hyg 2007. [DOI: 10.4269/ajtmh.77.6.suppl.1] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Affiliation(s)
- K. A. Koram
- Department of Epidemiology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Lego; Malawi-Liverpool-Wellcome Trust Clinical Research Programme, College of Medicine, University of Malawi; School of Tropical Medicine, University of Liverpool, United Kingdom
| | - M. E. Molyneux
- Department of Epidemiology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Lego; Malawi-Liverpool-Wellcome Trust Clinical Research Programme, College of Medicine, University of Malawi; School of Tropical Medicine, University of Liverpool, United Kingdom
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Long-term clinical protection from falciparum malaria is strongly associated with IgG3 antibodies to merozoite surface protein 3. PLoS Med 2007; 4:e320. [PMID: 18001147 PMCID: PMC2071934 DOI: 10.1371/journal.pmed.0040320] [Citation(s) in RCA: 186] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2007] [Accepted: 09/20/2007] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Surrogate markers of protective immunity to malaria in humans are needed to rationalize malaria vaccine discovery and development. In an effort to identify such markers, and thereby provide a clue to the complex equation malaria vaccine development is facing, we investigated the relationship between protection acquired through exposure in the field with naturally occurring immune responses (i.e., induced by the parasite) to molecules that are considered as valuable vaccine candidates. METHODS AND FINDINGS We analyzed, under comparative conditions, the antibody responses of each of six isotypes to five leading malaria vaccine candidates in relation to protection acquired by exposure to natural challenges in 217 of the 247 inhabitants of the African village of Dielmo, Senegal (96 children and 121 older adolescents and adults). The status of susceptibility or resistance to malaria was determined by active case detection performed daily by medical doctors over 6 y from a unique follow-up study of this village. Of the 30 immune responses measured, only one, antibodies of the IgG3 isotype directed to merozoite surface protein 3 (MSP3), was strongly associated with clinical protection against malaria in all age groups, i.e., independently of age. This immunological parameter had a higher statistical significance than the sickle cell trait, the strongest factor of protection known against Plasmodium falciparum. A single determination of antibody was significantly associated with the clinical outcome over six consecutive years in children submitted to massive natural parasite challenges by mosquitoes (over three parasite inoculations per week). Finally, the target epitopes of these antibodies were found to be fully conserved. CONCLUSIONS Since anti-MSP3 IgG3 antibodies can naturally develop along with protection against P. falciparum infection in young children, our results provide the encouraging indication that these antibodies should be possible to elicit by vaccination early in life. Since these antibodies have been found to achieve parasite killing under in vitro and in vivo conditions, and since they can be readily elicited by immunisation in naïve volunteers, our immunoepidemiological findings support the further development of MSP3-based vaccine formulations.
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Dent A, Malhotra I, Mungai P, Muchiri E, Crabb BS, Kazura JW, King CL. Prenatal malaria immune experience affects acquisition of Plasmodium falciparum merozoite surface protein-1 invasion inhibitory antibodies during infancy. THE JOURNAL OF IMMUNOLOGY 2007; 177:7139-45. [PMID: 17082631 DOI: 10.4049/jimmunol.177.10.7139] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
African infants are often born of mothers infected with malaria during pregnancy. This can result in fetal exposure to malaria-infected erythrocytes or their soluble products with subsequent fetal immune priming or tolerance in utero. We performed a cohort study of 30 newborns from a malaria holoendemic area of Kenya to determine whether T cell sensitization to Plasmodium falciparum merozoite surface protein-1 (MSP-1) at birth correlates with infant development of anti-MSP-1 Abs acquired as a consequence of natural malaria infection. Abs to the 42- and 19-kDa C-terminal processed fragments of MSP-1 were determined by serology and by a functional assay that quantifies invasion inhibition Abs against the MSP-1(19) merozoite ligand (MSP-1(19) IIA). Infants had detectable IgG and IgM Abs to MSP-1(42) and MSP-1(19) at 6 mo of age with no significant change by age 24-30 mo. In contrast, MSP-1(19) IIA levels increased from 6 to 24-30 mo of age (16-29%, p < 0.01). Infants with evidence of prenatal exposure to malaria (defined by P. falciparum detection in maternal, placental, and/or cord blood compartments) and T cell sensitization at birth (defined by cord blood lymphocyte cytokine responses to MSP-1) showed the greatest age-related increase in MSP-1(19) IIA compared with infants with prenatal exposure to malaria but who lacked detectable T cell MSP-1 sensitization. These data suggest that fetal sensitization or tolerance to MSP-1, associated with maternal malaria infection during pregnancy, affects the development of functional Ab responses to MSP-1 during infancy.
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Affiliation(s)
- Arlene Dent
- Center for Global Health and Diseases, Case Western Reserve University, Cleveland, OH 44106, USA
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Smith T, Ross A, Maire N, Rogier C, Trape JF, Molineaux L. An epidemiologic model of the incidence of acute illness in Plasmodium falciparum malaria. Am J Trop Med Hyg 2006; 75:56-62. [PMID: 16931816 DOI: 10.4269/ajtmh.2006.75.56] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
We propose a stochastic model for simulating malaria tolerance. The model relates the probability of a clinical attack of malaria to the peripheral parasite densities via a pyrogenic threshold that itself responds dynamically to the parasite load. The parameters of the model have been estimated by fitting it to the relationship between incidence of clinical episodes and the entomologic inoculation rate, using age-specific incidence data from two villages in Senegal and one village in Tanzania. The model reproduces the shifts in age distribution of clinical episodes associated with variation in transmission intensity, and in keeping with the data, predicts a slightly higher lifetime number of episodes in the mesoendemic village of Ndiop than in the holoendemic village of Dielmo. This model provides a parsimonious explanation of counter-intuitive relationships between the overall incidence of clinical malaria and transmission intensity. In contrast to the theory of endemic stability, recently proposed to apply to P. falciparum, it does not assume any intrinsic age dependence in the outcome of infection. This model can be used to explore the consequences for predictions of the effects of different anti-malarial interventions on the incidence of clinical malaria.
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