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Hergott DEB, Owalla TJ, Staubus WJ, Seilie AM, Chavtur C, Balkus JE, Apio B, Lema J, Cemeri B, Akileng A, Chang M, Egwang TG, Murphy SC. Assessing the daily natural history of asymptomatic Plasmodium infections in adults and older children in Katakwi, Uganda: a longitudinal cohort study. THE LANCET. MICROBE 2024; 5:e72-e80. [PMID: 38185134 PMCID: PMC10790327 DOI: 10.1016/s2666-5247(23)00262-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 08/13/2023] [Accepted: 08/16/2023] [Indexed: 01/09/2024]
Abstract
BACKGROUND Low-density asymptomatic Plasmodium infections are prevalent in endemic areas, but little is known about their natural history. The trajectories of these infections and their propensity to fluctuate to undetectable densities can affect detection in clinical trials and field studies. We aimed to classify the natural history of these infections in a high transmission area over 29 days. METHODS In this longitudinal cohort study, we enrolled healthy, malaria-asymptomatic, afebrile, adults (age 18-59 years) and older children (age 8-17 years) in Katakwi District, Uganda, who were negative for Plasmodium infection on rapid diagnostic tests. Participants were instructed to self-collect one dried blood spot (DBS) per day for a maximum of 29 days. We excluded people if they were pregnant or taking antimalarials. During weekly clinic visits, staff collected a DBS and a 4 mL sample of venous blood. We analysed DBSs by Plasmodium 18S rRNA quantitative RT-PCR (qRT-PCR). We classified DBS by infection type as negative, P falciparum, non-P falciparum, or mixed. We plotted infection type over time for each participant and categorised trajectories as negative, new, cleared, chronic, or indeterminate infections. To estimate the effect of single timepoint sampling, we calculated the daily prevalence for each study day and estimated the number of infections that would have been detected in our population if sampling frequency was reduced. FINDINGS Between April 9 and May 20, 2021, 3577 DBSs were collected by 128 (40 male adults, 60 female adults, 12 male children, and 16 female children) study participants. 2287 (64%) DBSs were categorised as negative, 751 (21%) as positive for P falciparum, 507 (14%) as positive for non-P falciparum, and 32 (1%) as mixed infections. Daily Plasmodium prevalence in the population ranged from 45·3% (95% CI 36·6-54·1) at baseline to 30·3% (21·9-38·6) on day 24. 37 (95%) of 39 P falciparum and 35 (85%) of 41 non-P falciparum infections would have been detected with every other day sampling, whereas, with weekly sampling, 35 (90%) P falciparum infections and 31 (76%) non-P falciparum infections would have been detected. INTERPRETATION Parasite dynamics and species are highly variable among low-density asymptomatic Plasmodium infections. Sampling every other day or every 3 days detected a similar proportion of infections as daily sampling, whereas testing once per week or even less frequently could misclassify up to a third of the infections. Even using highly sensitive diagnostics, single timepoint testing might misclassify the true infection status of an individual. FUNDING US National Institutes of Health and Bill and Melinda Gates Foundation.
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Affiliation(s)
- Dianna E B Hergott
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, USA; Department of Epidemiology, School of Public Health, University of Washington, Seattle, WA, USA
| | - Tonny J Owalla
- Department of Parasitology and Immunology, Med Biotech Laboratories, Kampala, Uganda
| | - Weston J Staubus
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, USA; Center for Emerging and Re-emerging Infectious Diseases, University of Washington, Seattle, WA, USA
| | - Annette M Seilie
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, USA; Center for Emerging and Re-emerging Infectious Diseases, University of Washington, Seattle, WA, USA
| | - Chris Chavtur
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, USA; Center for Emerging and Re-emerging Infectious Diseases, University of Washington, Seattle, WA, USA
| | - Jennifer E Balkus
- Department of Epidemiology, School of Public Health, University of Washington, Seattle, WA, USA
| | - Bernadette Apio
- Department of Parasitology and Immunology, Med Biotech Laboratories, Kampala, Uganda
| | - Jimmy Lema
- Department of Parasitology and Immunology, Med Biotech Laboratories, Kampala, Uganda
| | - Barbara Cemeri
- Department of Parasitology and Immunology, Med Biotech Laboratories, Kampala, Uganda
| | - Andrew Akileng
- Department of Parasitology and Immunology, Med Biotech Laboratories, Kampala, Uganda
| | - Ming Chang
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, USA; Center for Emerging and Re-emerging Infectious Diseases, University of Washington, Seattle, WA, USA
| | - Thomas G Egwang
- Department of Parasitology and Immunology, Med Biotech Laboratories, Kampala, Uganda
| | - Sean C Murphy
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, USA; Center for Emerging and Re-emerging Infectious Diseases, University of Washington, Seattle, WA, USA; Department of Microbiology, University of Washington, Seattle, WA, USA.
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Greischar MA, Childs LM. Extraordinary parasite multiplication rates in human malaria infections. Trends Parasitol 2023; 39:626-637. [PMID: 37336700 DOI: 10.1016/j.pt.2023.05.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Revised: 05/18/2023] [Accepted: 05/19/2023] [Indexed: 06/21/2023]
Abstract
For pathogenic organisms, faster rates of multiplication promote transmission success, the potential to harm hosts, and the evolution of drug resistance. Parasite multiplication rates (PMRs) are often quantified in malaria infections, given the relative ease of sampling. Using modern and historical human infection data, we show that established methods return extraordinarily - and implausibly - large PMRs. We illustrate how inflated PMRs arise from two facets of malaria biology that are far from unique: (i) some developmental ages are easier to sample than others; (ii) the distribution of developmental ages changes over the course of infection. The difficulty of accurately quantifying PMRs demonstrates a need for robust methods and a subsequent re-evaluation of what is known even in the well-studied system of malaria.
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Affiliation(s)
- Megan A Greischar
- Department of Ecology & Evolutionary Biology, Cornell University, Ithaca, NY, USA.
| | - Lauren M Childs
- Department of Mathematics, Virginia Tech, Blacksburg, VA, USA
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Oyibo W, Latham V, Oladipo O, Ntadom G, Uhomoibhi P, Ogbulafor N, Okoronkwo C, Okoh F, Mahmoud A, Shekarau E, Oresanya O, Cherima YJ, Jalingo I, Abba B, Audu M, Conway DJ. Malaria parasite density and detailed qualitative microscopy enhances large-scale profiling of infection endemicity in Nigeria. Sci Rep 2023; 13:1599. [PMID: 36709336 PMCID: PMC9884197 DOI: 10.1038/s41598-023-27535-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Accepted: 01/04/2023] [Indexed: 01/29/2023] Open
Abstract
With global progress towards malaria reduction stalling, further analysis of epidemiology is required, particularly in countries with the highest burden. National surveys have mostly analysed infection prevalence, while large-scale data on parasite density and different developmental forms rarely available. In Nigeria, the country with the largest burden globally, blood slide microscopy of children up to 5 years of age was conducted in the 2018 National Demographic and Health Survey, and parasite prevalence previously reported. In the current study, malaria parasite density measurements are reported and analysed for 7783 of the children sampled across the 36 states within the six geopolitical zones of the country. Asexual and sexual stages, and infections with different malaria parasite species are analysed. Across all states of Nigeria, there was a positive correlation between mean asexual parasite density within infected individuals and prevalence of infection in the community (Spearman's rho = 0.39, P = 0.02). Asexual parasite densities were highest in the northern geopolitical zones (geometric means > 2000 μL-1), extending the evidence of exceptionally high infection burden in many areas. Sexual parasite prevalence in each state was highly correlated with asexual parasite prevalence (Spearman's rho = 0.70, P < 0.001), although sexual parasite densities were low (geometric means < 100 μL-1 in all zones). Infants had lower parasite densities than children above 1 year of age, but there were no differences between male and female children. Most infections were of P. falciparum, which had higher asexual densities but lower sexual parasite densities than P. malariae or P. ovale mono-infections. However, mixed species infections had the highest asexual parasite densities. It is recommended that future large surveys in high burden countries measure parasite densities as well as developmental stages and species, to improve the quality of malaria epidemiology and tracking of future changes.
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Affiliation(s)
- Wellington Oyibo
- ANDI Centre of Excellence for Malaria Diagnosis, College of Medicine, University of Lagos, Lagos, Nigeria.
| | | | - Oladosu Oladipo
- ANDI Centre of Excellence for Malaria Diagnosis, College of Medicine, University of Lagos, Lagos, Nigeria
- Pure and Applied Biology Programme, Bowen University, Iwo, Osun State, Nigeria
| | - Godwin Ntadom
- Epidemiology Unit, Federal Ministry of Health, Abuja, Nigeria
- National Malaria Elimination Programme (NMEP), Federal Ministry of Health, Abuja, Nigeria
| | - Perpetua Uhomoibhi
- National Malaria Elimination Programme (NMEP), Federal Ministry of Health, Abuja, Nigeria
| | - Nnenna Ogbulafor
- National Malaria Elimination Programme (NMEP), Federal Ministry of Health, Abuja, Nigeria
| | - Chukwu Okoronkwo
- National Malaria Elimination Programme (NMEP), Federal Ministry of Health, Abuja, Nigeria
| | - Festus Okoh
- National Malaria Elimination Programme (NMEP), Federal Ministry of Health, Abuja, Nigeria
| | - Aminu Mahmoud
- National Malaria Elimination Programme (NMEP), Federal Ministry of Health, Abuja, Nigeria
| | - Emmanuel Shekarau
- National Malaria Elimination Programme (NMEP), Federal Ministry of Health, Abuja, Nigeria
| | | | | | | | - Bintu Abba
- National Population Commission, Abuja, Nigeria
| | - Mohammed Audu
- National Malaria Elimination Programme (NMEP), Federal Ministry of Health, Abuja, Nigeria
| | - David J Conway
- London School of Hygiene and Tropical Medicine, London, UK.
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Owalla TJ, Hergott DEB, Seilie AM, Staubus W, Chavtur C, Chang M, Kublin JG, Egwang TG, Murphy SC. Rethinking detection of pre-existing and intervening Plasmodium infections in malaria clinical trials. Front Immunol 2022; 13:1003452. [PMID: 36203582 PMCID: PMC9531235 DOI: 10.3389/fimmu.2022.1003452] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Accepted: 08/22/2022] [Indexed: 02/02/2023] Open
Abstract
Pre-existing and intervening low-density Plasmodium infections complicate the conduct of malaria clinical trials. These infections confound infection detection endpoints, and their immunological effects may detract from intended vaccine-induced immune responses. Historically, these infections were often unrecognized since infrequent and often analytically insensitive parasitological testing was performed before and during trials. Molecular diagnostics now permits their detection, but investigators must weigh the cost, complexity, and personnel demands on the study and the laboratory when scheduling such tests. This paper discusses the effect of pre-existing and intervening, low-density Plasmodium infections on malaria vaccine trial endpoints and the current methods employed for their infection detection. We review detection techniques, that until recently, provided a dearth of cost-effective strategies for detecting low density infections. A recently deployed, field-tested, simple, and cost-effective molecular diagnostic strategy for detecting pre-existing and intervening Plasmodium infections from dried blood spots (DBS) in malaria-endemic settings is discussed to inform new clinical trial designs. Strategies that combine sensitive molecular diagnostic techniques with convenient DBS collections and cost-effective pooling strategies may enable more thorough and informative infection monitoring in upcoming malaria clinical trials and epidemiological studies.
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Affiliation(s)
- Tonny J. Owalla
- Department of Immunology and Parasitology, Med Biotech Laboratories, Kampala, Uganda
| | - Dianna E. B. Hergott
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, United States,Department of Epidemiology, School of Public Health, University of Washington, Seattle, WA, United States
| | - Annette M. Seilie
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, United States,Center for Emerging and Re-emerging Infectious Diseases, University of Washington, Seattle, WA, United States
| | - Weston Staubus
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, United States,Center for Emerging and Re-emerging Infectious Diseases, University of Washington, Seattle, WA, United States
| | - Chris Chavtur
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, United States,Center for Emerging and Re-emerging Infectious Diseases, University of Washington, Seattle, WA, United States
| | - Ming Chang
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, United States,Center for Emerging and Re-emerging Infectious Diseases, University of Washington, Seattle, WA, United States
| | - James G. Kublin
- Department of Global Health, University of Washington, Seattle, WA, United States,Seattle Malaria Clinical Trials Center, Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, WA, United States
| | - Thomas G. Egwang
- Department of Immunology and Parasitology, Med Biotech Laboratories, Kampala, Uganda
| | - Sean C. Murphy
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, United States,Center for Emerging and Re-emerging Infectious Diseases, University of Washington, Seattle, WA, United States,Seattle Malaria Clinical Trials Center, Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, WA, United States,Department of Microbiology, University of Washington, Seattle, WA, United States,*Correspondence: Sean C. Murphy,
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Hergott DEB, Owalla TJ, Balkus JE, Apio B, Lema J, Cemeri B, Akileng A, Seilie AM, Chavtur C, Staubus W, Chang M, Egwang TG, Murphy SC. Feasibility of community at-home dried blood spot collection combined with pooled reverse transcription PCR as a viable and convenient method for malaria epidemiology studies. Malar J 2022; 21:221. [PMID: 35836179 PMCID: PMC9284728 DOI: 10.1186/s12936-022-04239-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 06/26/2022] [Indexed: 01/08/2023] Open
Abstract
Background Many Plasmodium infections in endemic regions exist at densities below the limit of detection of standard diagnostic tools. These infections threaten control efforts and may impact vaccine and therapeutic drug studies. Simple, cost-effective methods are needed to study the natural history of asymptomatic submicroscopic parasitaemia. Self-collected dried blood spots (DBS) analysed using pooled and individual quantitative reverse transcription polymerase chain reaction (qRT-PCR) provide such a solution. Here, the feasibility and acceptability of daily at-home DBS collections for qRT-PCR was studied to better understand low-density infections. Methods Rapid diagnostic test (RDT)-negative individuals in Katakwi District, northeastern Uganda, were recruited between April and May 2021. Venous blood samples and clinic-collected DBS were taken at enrollment and at four weekly clinic visits. Participants were trained in DBS collection and asked to collect six DBS weekly between clinic visits. Opinions about the collection process were solicited using daily Diary Cards and a Likert scale survey at the final study visit. Venous blood and DBS were analysed by Plasmodium 18S rRNA qRT-PCR. The number of participants completing the study, total DBS collected, and opinions of the process were analysed to determine compliance and acceptability. The human internal control mRNA and Plasmodium 18S rRNA were evaluated for at-home vs. clinic-collected DBS and venous blood to assess quality and accuracy of at-home collected samples. Results One-hundred two adults and 29 children were enrolled, and 95 and 26 completed the study, respectively. Three individuals withdrew due to pain or inconvenience of procedures. Overall, 96% of participants collected ≥ 16 of 24 at-home DBS, and 87% of DBS contained ≥ 40 µL of blood. The procedure was well tolerated and viewed favourably by participants. At-home collected DBS were acceptable for qRT-PCR and showed less than a one qRT-PCR cycle threshold shift in the human control mRNA compared to clinic-collected DBS. Correlation between Plasmodium falciparum 18S rRNA from paired whole blood and DBS was high (R = 0.93). Conclusions At-home DBS collection is a feasible, acceptable, and robust method to obtain blood to evaluate the natural history of low-density Plasmodium infections by qRT-PCR. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-022-04239-x.
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Affiliation(s)
- Dianna E B Hergott
- Department of Laboratory Medicine and Pathology, University of Washington, 750 Republican St., F870, Seattle, WA, 98109, USA.,Department of Epidemiology, School of Public Health, University of Washington, Seattle, WA, USA
| | - Tonny J Owalla
- Med Biotech Laboratories, P.O. Box 9364, Kampala, Uganda
| | - Jennifer E Balkus
- Department of Epidemiology, School of Public Health, University of Washington, Seattle, WA, USA
| | | | - Jimmy Lema
- Med Biotech Laboratories, P.O. Box 9364, Kampala, Uganda
| | - Barbara Cemeri
- Med Biotech Laboratories, P.O. Box 9364, Kampala, Uganda
| | - Andrew Akileng
- Med Biotech Laboratories, P.O. Box 9364, Kampala, Uganda
| | - Annette M Seilie
- Department of Laboratory Medicine and Pathology, University of Washington, 750 Republican St., F870, Seattle, WA, 98109, USA.,Center for Emerging and Re-Emerging Infectious Diseases, University of Washington, Seattle, WA, USA
| | - Chris Chavtur
- Department of Laboratory Medicine and Pathology, University of Washington, 750 Republican St., F870, Seattle, WA, 98109, USA.,Center for Emerging and Re-Emerging Infectious Diseases, University of Washington, Seattle, WA, USA
| | - Weston Staubus
- Department of Laboratory Medicine and Pathology, University of Washington, 750 Republican St., F870, Seattle, WA, 98109, USA.,Center for Emerging and Re-Emerging Infectious Diseases, University of Washington, Seattle, WA, USA
| | - Ming Chang
- Department of Laboratory Medicine and Pathology, University of Washington, 750 Republican St., F870, Seattle, WA, 98109, USA.,Center for Emerging and Re-Emerging Infectious Diseases, University of Washington, Seattle, WA, USA
| | | | - Sean C Murphy
- Department of Laboratory Medicine and Pathology, University of Washington, 750 Republican St., F870, Seattle, WA, 98109, USA. .,Center for Emerging and Re-Emerging Infectious Diseases, University of Washington, Seattle, WA, USA. .,Department of Microbiology, University of Washington, Seattle, WA, USA.
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Roe MS, O’Flaherty K, Fowkes FJ. Can malaria parasites be spontaneously cleared? Trends Parasitol 2022; 38:356-364. [DOI: 10.1016/j.pt.2022.02.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Revised: 02/07/2022] [Accepted: 02/08/2022] [Indexed: 12/25/2022]
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Huh HJ, Chung JW, Park SY, Chae SL. Vivax malaria detection using a parasitic red blood cell flag generated by the Sysmex XN-9000 hematology analyzer. Int J Lab Hematol 2021; 43:1403-1407. [PMID: 34374207 DOI: 10.1111/ijlh.13672] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 06/29/2021] [Accepted: 07/13/2021] [Indexed: 11/28/2022]
Abstract
INTRODUCTION A Sysmex XN-series hematology analyzer (Sysmex), the next generation up from the Sysmex XE-series, can provide information regarding malaria infection in the form of a parasitic red blood cell (pRBC) flag. This study aimed to determine the usefulness of the pRBC flag for early detection and follow-up in patients infected with Plasmodium vivax. METHODS A total of 221 patients with fever for whom CBC and malaria microscopy had been requested were analyzed. Sixty-seven individuals were diagnosed with P vivax infection, and 154 were diagnosed with other febrile diseases. The sensitivity and specificity of the pRBC flag for malaria parasite detection and the relationship between parasite density and presence of the pRBC flag were determined. The concordance rate between malaria microscopy and pRBC flag in 147 follow-up cases was calculated. RESULTS The pRBC flag was detected in 56 of 67 malaria patients (sensitivity, 83.6%; specificity, 100%). The patients with the pRBC flag at initial diagnosis revealed significantly higher parasite density than the patients without the pRBC flag (P < .05). The concordance rate between malaria microscopy and pRBC flag in the follow-up cases was 53.1%. CONCLUSION Considering its high sensitivity in malaria-suspicious patients, unexpected vivax malaria cases can be detected with the pRBC flag when CBC is done in a routine laboratory setting. The pRBC flag provided by the Sysmex XN series is a valuable tool for vivax malaria detection.
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Affiliation(s)
- Hee Jin Huh
- Departments of Laboratory Medicine, Dongguk University Ilsan Hospital, Goyang, Korea
| | - Jae-Woo Chung
- Departments of Laboratory Medicine, Dongguk University Ilsan Hospital, Goyang, Korea
| | - Seong Yeon Park
- Department of Internal medicine, Dongguk University Ilsan Hospital, Goyang, Korea
| | - Seok-Lae Chae
- Departments of Laboratory Medicine, Dongguk University Ilsan Hospital, Goyang, Korea
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Monthly Entomological Inoculation Rate Data for Studying the Seasonality of Malaria Transmission in Africa. DATA 2020. [DOI: 10.3390/data5020031] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
A comprehensive literature review was conducted to create a new database of 197 field surveys of monthly malaria Entomological Inoculation Rates (EIR), a metric of malaria transmission intensity. All field studies provide data at a monthly temporal resolution and have a duration of at least one year in order to study the seasonality of the disease. For inclusion, data collection methodologies adhered to a specific standard and the location and timing of the measurements were documented. Auxiliary information on the population and hydrological setting were also included. The database includes measurements that cover West and Central Africa and the period from 1945 to 2011, and hence facilitates analysis of interannual transmission variability over broad regions.
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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: 7] [Impact Index Per Article: 1.4] [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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Björkman A, Cook J, Sturrock H, Msellem M, Ali A, Xu W, Molteni F, Gosling R, Drakeley C, Mårtensson A. Spatial Distribution of Falciparum Malaria Infections in Zanzibar: Implications for Focal Drug Administration Strategies Targeting Asymptomatic Parasite Carriers. Clin Infect Dis 2018; 64:1236-1243. [PMID: 28431115 PMCID: PMC5399945 DOI: 10.1093/cid/cix136] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Indexed: 12/30/2022] Open
Abstract
Background. Optimal use of mass/targeted screen-and-treat or mass or focal drug administration as malaria elimination strategies remains unclear. We therefore studied spatial distribution of Plasmodium falciparum infections to compare simulated effects of these strategies on reducing the parasite reservoir in a pre-elimination setting. Methods. P. falciparum rapid diagnostic tests (RDTs) and molecular (polymerase chain reaction [PCR]) and serological (enzyme-linked immunosorbent assay) analyses were performed on finger-prick blood samples from a population-based survey in 3 adjacent communities. Results. Among 5278 persons screened, 13 (0.2%) were positive by RDT and 123 (2.3%) by PCR. PCR-positive individuals were scattered over the study area, but logistic regression analysis suggested a propensity of these infections to cluster around RDT-positive individuals. The odds ratios for being PCR positive was 7.4 (95% confidence interval, 2.8–19.9) for those living in the household of an RDT-positive individual and 1.64 (1.0–2.8; P = .06) for those living within <300 m, compared with >1000 m. Treating everyone within households of RDT-positive individuals (1% population) would target 13% of those who are PCR positive. Treating all living within a radius of <300 or <1000 m (14% or 58% population) would target 30% or 66% of infections, respectively. Among 4431 serologically screened individuals, 26% were seropositive. Treating everyone within seropositive households (63% population) would target 77% of PCR-positive individuals. Conclusions. Presumptive malaria treatment seemed justified within RDT-positive households and potentially worth considering within, for example, a radius of <300 m. Serology was not discriminative enough in identifying ongoing infections for improving focal interventions in this setting but may rather be useful to detect larger transmission foci.
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Affiliation(s)
- Anders Björkman
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Jackie Cook
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.,MRC Tropical Epidemiology Group, Faculty of Epidemiology and Population Health
| | - Hugh Sturrock
- Global Health Group, University of California, San Francisco, CA, USA
| | - Mwinyi Msellem
- Zanzibar Malaria Elimination Programme, Zanzibar Ministry of Health, Stone Town, Zanzibar, United Republic of Tanzania
| | - Abdullah Ali
- Zanzibar Malaria Elimination Programme, Zanzibar Ministry of Health, Stone Town, Zanzibar, United Republic of Tanzania
| | - Weiping Xu
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Fabrizio Molteni
- Swiss Tropical and Public Health Institute, Dar es Salaam, Tanzania
| | - Roly Gosling
- Global Health Group, University of California, San Francisco, CA, USA
| | - Chris Drakeley
- Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Andreas Mårtensson
- Department of Women's and Children's Health, International Maternal and Child Health, Uppsala University, Sweden
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Kwenti TE, Kwenti TDB, Latz A, Njunda LA, Nkuo-Akenji T. Epidemiological and clinical profile of paediatric malaria: a cross sectional study performed on febrile children in five epidemiological strata of malaria in Cameroon. BMC Infect Dis 2017; 17:499. [PMID: 28716002 PMCID: PMC5513087 DOI: 10.1186/s12879-017-2587-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2017] [Accepted: 07/03/2017] [Indexed: 11/16/2022] Open
Abstract
Background In the wake of a decline in global malaria, it is imperative to describe the epidemiology of malaria in a country to inform control policies. The purpose of this study was to describe the epidemiological and clinical profile of paediatric malaria in five epidemiological strata of malaria in Cameroon including: the Sudano-sahelian (SS) strata, the High inland plateau (HIP) strata, the South Cameroonian Equatorial forest (SCEF) strata, the High western plateau (HWP) strata, and the Coastal (C) strata. Methods This study involved 1609 febrile children (≤15 years) recruited using reference hospitals in the five epidemiological strata. Baseline characteristics were determined; blood glucose level was measured by a glucometer, malaria parasitaemia was assessed by Giemsa microscopy, and complete blood count was performed using an automated hematology analyser. Severe malaria was assessed and categorized based on WHO criteria. Results An overall prevalence of 15.0% (95% CI: 13.3–16.9) for malaria was observed in this study. Malaria prevalence was significantly higher in children between 60 and 119 months (p < 0.001) and in Limbe (C strata) (p < 0.001). The overall rate of severe malaria (SM) attack in this study was 29.3%; SM was significantly higher in children below 60 months (p < 0.046). Although not significant, the rate of SM was highest in Maroua (SS strata) and lowest in Limbe in the C strata. The main clinical phenotypes of SM were hyperparasitaemia, severe malaria anaemia and impaired consciousness. The majority (73.2%) of SM cases were in group 1 of the WHO classification of severe malaria (i.e. the most severe form). The malaria case-fatality rate was 5.8%; this was higher in Ngaoundere (HIP strata) (p = 0.034). Conclusion In this study, malaria prevalence decreased steadily northward, from the C strata in the South to the SS strata in the North of Cameroon, meanwhile the mortality rate associated with malaria increased in the same direction. On the contrary, the rate of severe malaria attack was similar across the different epidemiological strata. Immunoepidemiological studies will be required to shed more light on the observed trends.
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Affiliation(s)
- Tebit Emmanuel Kwenti
- Department of Medical Laboratory Sciences, University of Buea, P.B, 63, Buea, Cameroon. .,Department of Microbiology and Parasitology, University of Buea, P.B, 63, Buea, Cameroon. .,Diagnostic laboratory, Regional Hospital of Buea, P.B, 32, Buea, Cameroon.
| | | | - Andreas Latz
- Research and Development Department, NovaTec Immundiagnostica GmbH, Dietzenbach, Germany
| | - Longdoh Anna Njunda
- Department of Medical Laboratory Sciences, University of Buea, P.B, 63, Buea, Cameroon
| | - Theresa Nkuo-Akenji
- Department of Microbiology and Parasitology, University of Buea, P.B, 63, Buea, Cameroon
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Manguin S, Foumane V, Besnard P, Fortes F, Carnevale P. Malaria overdiagnosis and subsequent overconsumption of antimalarial drugs in Angola: Consequences and effects on human health. Acta Trop 2017; 171:58-63. [PMID: 28356231 DOI: 10.1016/j.actatropica.2017.03.022] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 03/24/2017] [Accepted: 03/24/2017] [Indexed: 10/19/2022]
Abstract
Microscopic blood smear examinations done in health centers of Angola demonstrated a large overdiagnosis of malaria cases with an average rate of errors as high as 85%. Overall 83% of patients who received Coartem® had an inappropriate treatment. Overestimated malaria diagnosis was noticed even when specific symptoms were part of the clinical observation, antimalarial treatments being subsequently given. Then, malaria overdiagnosis has three main consequences, (i) the lack of data reliability is of great concern, impeding epidemiological records and evaluation of the actual influence of operations as scheduled by the National Malaria Control Programme; (ii) the large misuse of antimalarial drug can increase the selective pressure for resistant strain and can make a false consideration of drug resistant P. falciparum crisis; and (iii) the need of strengthening national health centers in term of human, with training in microscopy, and equipment resources to improve malaria diagnosis with a large scale use of rapid diagnostic tests associated with thick blood smears, backed up by a "quality control" developed by the national health authorities. Monitoring of malaria cases was done in three Angolan health centers of Alto Liro (Lobito town) and neighbor villages of Cambambi and Asseque (Benguéla Province) to evaluate the real burden of malaria. Carriers of Plasmodium among patients of newly-borne to 14 years old, with or without fever, were analyzed and compared to presumptive malaria cases diagnosed in these health centers. Presumptive malaria cases were diagnosed six times more than the positive thick blood smears done on the same children. In Alto Liro health center, the percentage of diagnosis error reached 98%, while in Cambambi and Asseque it was of 79% and 78% respectively. The percentage of confirmed malaria cases was significantly higher during the dry (20.2%) than the rainy (13.2%) season. These observations in three peripheral health centers confirmed what has already been noticed in other malaria endemic regions, and highlight the need for an accurate evaluation of the Malaria control programme implemented in Angola.
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Otte im Kampe E, Müller O, Sie A, Becher H. Seasonal and temporal trends in all-cause and malaria mortality in rural Burkina Faso, 1998-2007. Malar J 2015; 14:300. [PMID: 26243295 PMCID: PMC4524173 DOI: 10.1186/s12936-015-0818-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 07/22/2015] [Indexed: 11/11/2022] Open
Abstract
BACKGROUND High mortality levels in sub-Saharan Africa are still a major public health problem. Children are the most affected group with malaria as one of the major causes of death in this region. To plan health interventions, reliable empirical information on cause-specific mortality patterns is essential, yet such data are often not available in developing countries. Health and Demographic Surveillance Systems (HDSS) implementing the verbal autopsy (VA) method provide such data on a longitudinal basis. Physician Coded VA is usually used to determine cause of death, but recently a computerized method, Interpreting VA (InterVA) was alternatively introduced. This study investigates the effect of season on all-cause and malaria mortality analysing cause of death data from 1998 to 2007 obtained by the Nouna HDSS in rural Burkina Faso and derived by InterVA. METHODS Monthly mortality rates were calculated for different age groups (infants, children, adolescents, adults, elderly). Seasonal and temporal trends were modelled with parametric Poisson regression adjusted for sex, area of residence and year of death. RESULTS Overall, 7,378 deaths occurred corresponding to a mortality rate of 11.9/1,000 with highest rates in infants (56.8/1,000) and children (22.0/1,000). Young children were most affected by malaria. Malaria mortality patterns in children showed significantly higher rates during the rainy season and a stagnant long-term trend. The seasonal trend is well described parametrically with a sinusoidal function. InterVA assigned about half as many deaths to malaria than physicians. CONCLUSIONS Malaria mortality remains highly seasonal in rural Burkina Faso. The InterVA method appears to determine reasonably well seasonal mortality patterns, which should be considered for the planning of health resources and activities.
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Affiliation(s)
- Eveline Otte im Kampe
- Institute of Public Health, University of Heidelberg, Heidelberg, Germany.
- London School of Hygiene and Tropical Medicine, London, UK.
| | - Olaf Müller
- Institute of Public Health, University of Heidelberg, Heidelberg, Germany.
| | - Ali Sie
- Centre de Recherche en Santé de Nouna, Nouna, Burkina Faso.
| | - Heiko Becher
- Institute of Public Health, University of Heidelberg, Heidelberg, Germany.
- Institute for Medical Biometry, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
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Cook J, Xu W, Msellem M, Vonk M, Bergström B, Gosling R, Al-Mafazy AW, McElroy P, Molteni F, Abass AK, Garimo I, Ramsan M, Ali A, Mårtensson A, Björkman A. Mass screening and treatment on the basis of results of a Plasmodium falciparum-specific rapid diagnostic test did not reduce malaria incidence in Zanzibar. J Infect Dis 2015; 211:1476-83. [PMID: 25429102 PMCID: PMC10881232 DOI: 10.1093/infdis/jiu655] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Accepted: 11/10/2014] [Indexed: 02/23/2024] Open
Abstract
BACKGROUND Seasonal increases in malaria continue in hot spots in Zanzibar. Mass screening and treatment (MSAT) may help reduce the reservoir of infection; however, it is unclear whether rapid diagnostic tests (RDTs) detect a sufficient proportion of low-density infections to influence subsequent transmission. METHODS Two rounds of MSAT using Plasmodium falciparum-specific RDT were conducted in 5 hot spots (population, 12 000) in Zanzibar in 2012. In parallel, blood samples were collected on filter paper for polymerase chain reaction (PCR) analyses. Data on confirmed malarial parasite infections from health facilities in intervention and hot spot control areas were monitored as proxy for malaria transmission. RESULTS Approximately 64% of the population (7859) were screened at least once. P. falciparum prevalence, as measured by RDT, was 0.2% (95% confidence interval [CI], .1%-.3%) in both rounds, compared with PCR measured prevalences (for all species) of 2.5% (95% CI, 2.1%-2.9%) and 3.8% (95% CI, 3.2%-4.4%) in rounds 1 and 2, respectively. Two fifths (40%) of infections detected by PCR included non-falciparum species. Treatment of RDT-positive individuals (4% of the PCR-detected parasite carriers) did not reduce subsequent malaria incidence, compared with control areas. CONCLUSIONS Highly sensitive point-of-care diagnostic tools for detection of all human malaria species are needed to make MSAT an effective strategy in settings where malaria elimination programs are in the pre-elimination phase.
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Affiliation(s)
- Jackie Cook
- Department of Microbiology and Tumor and Cell Biology, Uppsala University, Sweden
| | - Weiping Xu
- Department of Microbiology and Tumor and Cell Biology, Uppsala University, Sweden
| | - Mwinyi Msellem
- Zanzibar Malaria Elimination Programme, Ministry of Health, University of California–San Francisco
| | - Marlotte Vonk
- Department of Microbiology and Tumor and Cell Biology, Uppsala University, Sweden
| | - Beatrice Bergström
- Department of Microbiology and Tumor and Cell Biology, Uppsala University, Sweden
| | - Roly Gosling
- Global Health Group, University of California–San Francisco
| | - Abdul-Wahid Al-Mafazy
- Zanzibar Malaria Elimination Programme, Ministry of Health, University of California–San Francisco
| | - Peter McElroy
- US President’s Malaria Initiative and Centers for Disease Control and Prevention Tanzania, University of California–San Francisco
- Malaria Branch, Centers for Disease Control and Prevention, Atlanta, Georgia
| | - Fabrizio Molteni
- Swiss Tropical and Public Health Institute, University of California–San Francisco
- University of Basel, Switzerland
| | - Ali K. Abass
- Zanzibar Malaria Elimination Programme, Ministry of Health, University of California–San Francisco
| | - Issa Garimo
- RTI International, Dar es Salaam, Tanzania, University of California–San Francisco
| | - Mahdi Ramsan
- RTI International, Dar es Salaam, Tanzania, University of California–San Francisco
| | - Abdullah Ali
- Zanzibar Malaria Elimination Programme, Ministry of Health, University of California–San Francisco
| | - Andreas Mårtensson
- Department of Microbiology and Tumor and Cell Biology, Uppsala University, Sweden
- Global Health, Department of Public Health Sciences, Karolinska Institutet, Stockholm, Uppsala University, Sweden
- Centre for Clinical Research Sörmland, Uppsala University, Sweden
| | - Anders Björkman
- Department of Microbiology and Tumor and Cell Biology, Uppsala University, Sweden
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15
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Sondén K, Doumbo S, Hammar U, Vafa Homann M, Ongoiba A, Traoré B, Bottai M, Crompton PD, Färnert A. Asymptomatic Multiclonal Plasmodium falciparum Infections Carried Through the Dry Season Predict Protection Against Subsequent Clinical Malaria. J Infect Dis 2015; 212:608-16. [PMID: 25712968 DOI: 10.1093/infdis/jiv088] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 02/06/2015] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Immunity to the antigenically diverse parasite Plasmodium falciparum is acquired gradually after repeated exposure. Studies in areas of high malaria transmission have shown that asymptomatic individuals infected with multiclonal infections are at reduced risk of febrile malaria during follow-up. METHODS We assessed the relationship between the genetic diversity of clones in P. falciparum infections that persist through the dry season and the subsequent risk of febrile malaria in 225 individuals aged 2-25 years in Mali, where the 6-month malaria and dry seasons are sharply demarcated. Polymerase chain reaction-based genotyping of the highly polymorphic merozoite surface protein 2 gene was performed on blood samples collected at 5 cross-sectional surveys. RESULTS In an age-adjusted analysis, individuals with multiclonal P. falciparum infections before the rainy season were at reduced risk of febrile malaria, compared with individuals who were uninfected (hazard ratio [HR], 0.28; 95% confidence interval [CI], .11-.69). In contrast, there was no significant association between risk of malaria and having 1 clone at baseline (HR, 0.71; 95% CI, .36-1.40). CONCLUSIONS The results suggest that persistent multiclonal infections carried through the dry season contribute to protection against subsequent febrile malaria, possibly by maintaining protective immune responses that depend on ongoing parasite infection.
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Affiliation(s)
- Klara Sondén
- Unit of Infectious Diseases, Department of Medicine Solna
| | - Safiatou Doumbo
- Mali International Center of Excellence in Research, University of Sciences, Technique, and Technology of Bamako
| | - Ulf Hammar
- Unit of Biostatistics, Department of Epidemiology, Institute for Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
| | | | - Aissata Ongoiba
- Unit of Biostatistics, Department of Epidemiology, Institute for Environmental Medicine, Karolinska Institutet, Stockholm, Sweden Mali International Center of Excellence in Research, University of Sciences, Technique, and Technology of Bamako
| | - Boubacar Traoré
- Mali International Center of Excellence in Research, University of Sciences, Technique, and Technology of Bamako
| | - Matteo Bottai
- Unit of Biostatistics, Department of Epidemiology, Institute for Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Peter D Crompton
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland
| | - Anna Färnert
- Unit of Infectious Diseases, Department of Medicine Solna
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Ardiet DL, Graz B, Szeless T, Mauris A, Falquet J, Doumbo OK, Dolo A, Guindo O, Sissoko MS, Konaré M, Motamed S, Rougemont AC. Patterns of malaria indices across three consecutive seasons in children in a highly endemic area of West Africa: a three times-repeated cross-sectional study. Malar J 2014; 13:199. [PMID: 24885107 PMCID: PMC4082285 DOI: 10.1186/1475-2875-13-199] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Accepted: 05/21/2014] [Indexed: 11/10/2022] Open
Abstract
OBJECTIVES To study the manifestations of Plasmodium infection, and its relations with the malaria disease, especially when comparing dry and rainy seasons in a hyperendemic area of West Africa. METHODS The study was carried out in an area where malaria transmission is high, showing important seasonal variations. One thousand children, representing the total child population (1-12 year old), were observed transversally at the end of three consecutive seasons (dry/rainy/dry). The usual indicators, such as parasite density, splenomegaly, anaemia, or febrile disease were recorded and analysed. RESULTS The prevalence of Plasmodium falciparum was high in all age groups and seasons, constantly around 60%. The high transmission season (rainy) showed higher rates of anaemia and spleen enlargement and, in the youngest children only, higher parasite densities. There were also differences between the two dry seasons: in the first one, there was a higher rate of fever than in the second one (p < 0.001). Low parasite density (<2,000 p/μl) was never associated with fever during any season, raising some concern with regard to the usefulness of parasite detection. The possible origins of fever are discussed, together with the potential usefulness of analyzing these indices on a population sample, at a time when fever incidence rises and malaria is one potential cause among others. The distinction to be made between the Plasmodium infection and the malaria disease is highlighted. CONCLUSIONS These data confirm previous hypotheses of a strong difference in malaria infection and disease between dry and rainy seasons. The most relevant seasonal indicator was not mainly parasite rate and density but anaemia, spleen enlargement, prevalence and possible origin of fever. RECOMMENDATIONS In any situation (i.e. fever or not) and especially during the dry season, one must consider that detection of parasites in the blood is only evidence of a Plasmodium infection and not necessarily of a malaria disease. In such a situation, it seems suitable to obtain, through national malaria teams, a well-defined situation of transmission and prevalence of Plasmodium infection following zones and seasons, in order to adapt control strategies. For researchers, a systematic management of data separately for dry and rainy season appears mandatory.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | - André C Rougemont
- IMSP: Institut de Médecine Sociale et Préventive (currently Institut de santé globale), CMU, rue Michel Servet 1, Genève 4 CH-1211, Switzerland.
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Tietje K, Hawkins K, Clerk C, Ebels K, McGray S, Crudder C, Okell L, LaBarre P. The essential role of infection-detection technologies for malaria elimination and eradication. Trends Parasitol 2014; 30:259-66. [DOI: 10.1016/j.pt.2014.03.003] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Revised: 03/11/2014] [Accepted: 03/12/2014] [Indexed: 11/26/2022]
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Dolo A, Maïga B, Dara V, Tapily A, Tolo Y, Arama C, Daou M, Doumbo O. [Place of malaria among febrile illnesses in two ethnic tribes living in sympatry in Mali from 1998 to 2008]. ACTA ACUST UNITED AC 2012; 105:377-83. [PMID: 22932999 DOI: 10.1007/s13149-012-0249-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Accepted: 05/05/2012] [Indexed: 11/30/2022]
Abstract
In Africa, malaria is responsible for 25-40% of all outpatient visits and 20-50% of all hospitalizations. In malaria-endemic areas, individuals do not behave the same toward the outcome of clinical malaria. The aim of this study is to determine the prevalence of malaria in the locality among the different ethnic groups, evaluate the place of malaria among febrile illnesses, and assess the relationship between fever and parasite density of Plasmodium falciparum. Studies on susceptibility to malaria between the Fulani and Dogon groups in Mali were conducted in Mantéourou and the surrounding villages from 1998 to 2008. We carried out six cross-sectional studies during the malaria transmission and longitudinal surveys (July to December depending on the year) during the 10-year duration. In longitudinal studies, clinical data on malaria and other diseases frequently observed in the population were recorded. It appears from this work that malaria is the leading cause of febrile syndromes. We observed a significant reduction in malaria morbidity in the study population from 1998 to 2008. The pyrogenic threshold of parasitaemia was 1,000 parasites/mm(3) of blood in the Dogon and 5,000 parasites/mm(3) of blood in the Fulani.We have also found that high parasitical densities were not always associated with fever. Malaria morbidity was higher among the Dogon than in Fulani. The immunogenetic factors might account for this difference in susceptibility to malaria between Fulani and Dogon in the area under study. With regard to this study, it is important to take into account the ethnic origin of subjects when interpreting data of clinical and malarial vaccine trials.
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Affiliation(s)
- A Dolo
- Malaria Research and Training Center (MRTC), département d'épidémiologie des affections parasitaires, de pharmacie et d'odontostomatologie (DEAP/FMPOS), université de Bamako, Bamako, République du Mali.
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19
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Ramroth H, Lorenz E, Rankin JC, Fottrell E, Yé M, Neuhann F, Ssennono M, Sié A, Byass P, Becher H. Cause of death distribution with InterVA and physician coding in a rural area of Burkina Faso. Trop Med Int Health 2012; 17:904-13. [PMID: 22574916 DOI: 10.1111/j.1365-3156.2012.02998.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
OBJECTIVES To compare the cause of death distribution using the Physician Coded Verbal Autopsy approach versus the Interpreting Verbal Autopsy model, based on information from a French verbal autopsy questionnaire, in rural north-western Burkina Faso. METHODS Data from 5649 verbal autopsy questionnaires reviewed by local physicians at the Nouna Health and Demographic Surveillance Site between 1998 and 2007 were considered for analyses. Information from VA interviews was extracted to create a set of standard indicators needed to run the Interpreting Verbal Autopsy model. Cause-specific mortality fractions were used to compare Physician Coded Verbal Autopsy and Interpreting Verbal Autopsy results. RESULTS At the population level, 62.5% of causes of death using the Interpreting Verbal Autopsy model corresponded with those determined by two or three physicians. Although seven of the 10 main causes of death were present in both approaches, the comparison of percentages of single causes of death shows discrepancies, dominated by higher malaria rates found in the Physician Coded Verbal Autopsy approach. CONCLUSION Our results confirm that national mortality statistics, which are partly based on verbal autopsies, must be carefully interpreted. Difficulties in determining malaria as cause of death in holoendemic malaria regions might result in higher discrepancies than those in non-endemic areas. As neither Physician Coded Verbal Autopsy nor Interpreting Verbal Autopsy results represent a gold standard, uncertainty levels with either procedure are high.
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Affiliation(s)
- Heribert Ramroth
- Institute of Public Health, University Hospital of Heidelberg, Heidelberg, Germany.
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20
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Effect of seasonality and ecological factors on the prevalence of the four malaria parasite species in northern mali. J Trop Med 2012; 2012:367160. [PMID: 22529864 PMCID: PMC3316987 DOI: 10.1155/2012/367160] [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: 04/25/2011] [Accepted: 12/29/2011] [Indexed: 11/21/2022] Open
Abstract
Background. We performed 2 cross-sectional studies in Ménaka in the Northeastern Mali across 9 sites in different ecological settings: 4 sites have permanent ponds, 4 without ponds, and one (City of Ménaka) has a semipermanent pond. We enrolled 1328 subjects in May 2004 (hot dry season) and 1422 in February 2005 (cold dry season) after the rainy season. Objective. To examine the seasonality of malaria parasite prevalence in this dry northern part of Mali at the edge of the Sahara desert. Results. Slide prevalence was lower in hot dry than cold dry season (4.94 versus 6.85%, P = 0.025). Gametocyte rate increased to 0.91% in February. Four species were identified. Plasmodium falciparum was most prevalent (74.13 and 63.72%). P. malariae increased from 9.38% to 22.54% in February. In contrast, prevalence of P. vivax was higher (10.31%) without seasonal variation. Smear positivity was associated with splenomegaly (P = 0.007). Malaria remained stable in the villages with ponds (P = 0.221); in contrast, prevalence varied between the 2 seasons in the villages without ponds (P = 0.004). Conclusion. Malaria was mesoendemic; 4 species circulates with a seasonal fluctuation for Plasmodium falciparum.
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21
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Rankin JC, Lorenz E, Neuhann F, Yé M, Sié A, Becher H, Ramroth H. Exploring the role narrative free-text plays in discrepancies between physician coding and the InterVA regarding determination of malaria as cause of death, in a malaria holo-endemic region. Malar J 2012; 11:51. [PMID: 22353802 PMCID: PMC3359180 DOI: 10.1186/1475-2875-11-51] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2011] [Accepted: 02/21/2012] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND In countries where tracking mortality and clinical cause of death are not routinely undertaken, gathering verbal autopsies (VA) is the principal method of estimating cause of death. The most common method for determining probable cause of death from the VA interview is Physician-Certified Verbal Autopsy (PCVA). A recent alternative method to interpret Verbal Autopsy (InterVA) is a computer model using a Bayesian approach to derive posterior probabilities for causes of death, given an a priori distribution at population level and a set of interview-based indicators. The model uses the same input information as PCVA, with the exception of narrative text information, which physicians can consult but which were not inputted into the model. Comparing the results of physician coding with the model, large differences could be due to difficulties in diagnosing malaria, especially in holo-endemic regions. Thus, the aim of the study was to explore whether physicians' access to electronically unavailable narrative text helps to explain the large discrepancy in malaria cause-specific mortality fractions (CSMFs) in physician coding versus the model. METHODS Free-texts of electronically available records (N = 5,649) were summarised and incorporated into the InterVA version 3 (InterVA-3) for three sub-groups: (i) a 10%-representative subsample (N = 493) (ii) records diagnosed as malaria by physicians and not by the model (N = 1035), and (iii) records diagnosed by the model as malaria, but not by physicians (N = 332). CSMF results before and after free-text incorporation were compared. RESULTS There were changes of between 5.5-10.2% between models before and after free-text incorporation. No impact on malaria CSMFs was seen in the representative sub-sample, but the proportion of malaria as cause of death increased in the physician sub-sample (2.7%) and saw a large decrease in the InterVA subsample (9.9%). Information on 13/106 indicators appeared at least once in the free-texts that had not been matched to any item in the structured, electronically available portion of the Nouna questionnaire. DISCUSSION Free-texts are helpful in gathering information not adequately captured in VA questionnaires, though access to free-text does not explain differences in physician and model determination of malaria as cause of death.
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Affiliation(s)
- Johanna C Rankin
- Institute of Public Health, University Hospital of Heidelberg, Heidelberg, Germany
| | - Eva Lorenz
- Institute of Public Health, University Hospital of Heidelberg, Heidelberg, Germany
| | - Florian Neuhann
- Institute of Public Health, University Hospital of Heidelberg, Heidelberg, Germany
| | - Maurice Yé
- Centre de Recherche en Santé de Nouna, Nouna, Burkina Faso
| | - Ali Sié
- Centre de Recherche en Santé de Nouna, Nouna, Burkina Faso
| | - Heiko Becher
- Institute of Public Health, University Hospital of Heidelberg, Heidelberg, Germany
| | - Heribert Ramroth
- Institute of Public Health, University Hospital of Heidelberg, Heidelberg, Germany
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Veenemans J, Milligan P, Prentice AM, Schouten LRA, Inja N, van der Heijden AC, de Boer LCC, Jansen EJS, Koopmans AE, Enthoven WTM, Kraaijenhagen RJ, Demir AY, Uges DRA, Mbugi EV, Savelkoul HFJ, Verhoef H. Effect of supplementation with zinc and other micronutrients on malaria in Tanzanian children: a randomised trial. PLoS Med 2011; 8:e1001125. [PMID: 22131908 PMCID: PMC3222646 DOI: 10.1371/journal.pmed.1001125] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Accepted: 10/14/2011] [Indexed: 01/31/2023] Open
Abstract
BACKGROUND It is uncertain to what extent oral supplementation with zinc can reduce episodes of malaria in endemic areas. Protection may depend on other nutrients. We measured the effect of supplementation with zinc and other nutrients on malaria rates. METHODS AND FINDINGS In a 2×2 factorial trial, 612 rural Tanzanian children aged 6-60 months in an area with intense malaria transmission and with height-for-age z-score≤-1.5 SD were randomized to receive daily oral supplementation with either zinc alone (10 mg), multi-nutrients without zinc, multi-nutrients with zinc, or placebo. Intervention group was indicated by colour code, but neither participants, researchers, nor field staff knew who received what intervention. Those with Plasmodium infection at baseline were treated with artemether-lumefantrine. The primary outcome, an episode of malaria, was assessed among children reported sick at a primary care clinic, and pre-defined as current Plasmodium infection with an inflammatory response, shown by axillary temperature ≥37.5°C or whole blood C-reactive protein concentration ≥ 8 mg/L. Nutritional indicators were assessed at baseline and at 251 days (median; 95% reference range: 191-296 days). In the primary intention-to-treat analysis, we adjusted for pre-specified baseline factors, using Cox regression models that accounted for multiple episodes per child. 592 children completed the study. The primary analysis included 1,572 malaria episodes during 526 child-years of observation (median follow-up: 331 days). Malaria incidence in groups receiving zinc, multi-nutrients without zinc, multi-nutrients with zinc and placebo was 2.89/child-year, 2.95/child-year, 3.26/child-year, and 2.87/child-year, respectively. There was no evidence that multi-nutrients influenced the effect of zinc (or vice versa). Neither zinc nor multi-nutrients influenced malaria rates (marginal analysis; adjusted HR, 95% CI: 1.04, 0.93-1.18 and 1.10, 0.97-1.24 respectively). The prevalence of zinc deficiency (plasma zinc concentration <9.9 µmol/L) was high at baseline (67% overall; 60% in those without inflammation) and strongly reduced by zinc supplementation. CONCLUSIONS We found no evidence from this trial that zinc supplementation protected against malaria. TRIAL REGISTRATION ClinicalTrials.gov NCT00623857
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Affiliation(s)
- Jacobien Veenemans
- Wageningen University, Cell Biology and Immunology Group, Wageningen, The Netherlands
- Laboratory for Microbiology and Infection Control, Amphia Hospital, Breda, The Netherlands
| | - Paul Milligan
- Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Andrew M. Prentice
- MRC International Nutrition Group, London School of Hygiene and Tropical Medicine, London, United Kingdom
- MRC Keneba, The Gambia
| | - Laura R. A. Schouten
- Wageningen University, Cell Biology and Immunology Group, Wageningen, The Netherlands
| | - Nienke Inja
- Wageningen University, Cell Biology and Immunology Group, Wageningen, The Netherlands
| | | | - Linsey C. C. de Boer
- Wageningen University, Cell Biology and Immunology Group, Wageningen, The Netherlands
| | - Esther J. S. Jansen
- Wageningen University, Cell Biology and Immunology Group, Wageningen, The Netherlands
| | - Anna E. Koopmans
- Wageningen University, Cell Biology and Immunology Group, Wageningen, The Netherlands
| | - Wendy T. M. Enthoven
- Wageningen University, Cell Biology and Immunology Group, Wageningen, The Netherlands
| | - Rob J. Kraaijenhagen
- Meander Medical Centre, Laboratory for Clinical Chemistry and Haematology, Amersfoort, The Netherlands
| | - Ayse Y. Demir
- Meander Medical Centre, Laboratory for Clinical Chemistry and Haematology, Amersfoort, The Netherlands
| | - Donald R. A. Uges
- University of Groningen, University Medical Center, Department of Pharmacy, Laboratory for Clinical and Forensic Toxicology and Drug Analysis, Groningen, The Netherlands
| | - Erasto V. Mbugi
- Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
| | - Huub F. J. Savelkoul
- Wageningen University, Cell Biology and Immunology Group, Wageningen, The Netherlands
| | - Hans Verhoef
- Wageningen University, Cell Biology and Immunology Group, Wageningen, The Netherlands
- MRC International Nutrition Group, London School of Hygiene and Tropical Medicine, London, United Kingdom
- * E-mail:
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Veenemans J, Jansen EJS, Baidjoe AY, Mbugi EV, Demir AY, Kraaijenhagen RJ, Savelkoul HFJ, Verhoef H. Effect of α(+)-thalassaemia on episodes of fever due to malaria and other causes: a community-based cohort study in Tanzania. Malar J 2011; 10:280. [PMID: 21939508 PMCID: PMC3195205 DOI: 10.1186/1475-2875-10-280] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2011] [Accepted: 09/22/2011] [Indexed: 11/10/2022] Open
Abstract
Background It is controversial to what degree α+-thalassaemia protects against episodes of uncomplicated malaria and febrile disease due to infections other than Plasmodium. Methods In Tanzania, in children aged 6-60 months and height-for-age z-score < -1.5 SD (n = 612), rates of fevers due to malaria and other causes were compared between those with heterozygous or homozygotes α+-thalassaemia and those with a normal genotype, using Cox regression models that accounted for multiple events per child. Results The overall incidence of malaria was 3.0/child-year (1, 572/526 child-years); no differences were found in malaria rates between genotypes (hazard ratios, 95% CI: 0.93, 0.82-1.06 and 0.91, 0.73-1.14 for heterozygotes and homozygotes respectively, adjusted for baseline factors that were predictive for outcome). However, this association strongly depended on age: among children aged 6-17 months, those with α+-thalassaemia experienced episodes more frequently than those with a normal genotype (1.30, 1.02-1.65 and 1.15, 0.80-1.65 for heterozygotes and homozygotes respectively), whereas among their peers aged 18-60 months, α+-thalassaemia protected against malaria (0.80, 0.68-0.95 and 0.78, 0.60-1.03; p-value for interaction 0.001 and 0.10 for hetero- and homozygotes respectively). No effect was observed on non-malarial febrile episodes. Conclusions In this population, the association between α+-thalassaemia and malaria depends on age. Our data suggest that protection by α+-thalassaemia is conferred by more efficient acquisition of malaria-specific immunity.
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Affiliation(s)
- Jacobien Veenemans
- Wageningen University, Cell Biology and Immunology Group, Wageningen, The Netherlands.
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Hirji KF, Premji ZG. Pre-referral rectal artesunate in severe malaria: flawed trial. Trials 2011; 12:188. [PMID: 21824389 PMCID: PMC3171715 DOI: 10.1186/1745-6215-12-188] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Accepted: 08/08/2011] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Immediate injectable treatment is essential for severe malaria. Otherwise, the afflicted risk lifelong impairment or death. In rural areas of Africa and Asia, appropriate care is often miles away. In 2009, Melba Gomes and her colleagues published the findings of a randomized, placebo-controlled trial of rectal artesunate for suspected severe malaria in such remote areas. Enrolling nearly 18,000 cases, the aim was to evaluate whether, as patients were in transit to a health facility, a pre-referral artesunate suppository blocked disease progression sufficiently to reduce these risks. The affirmative findings of this, the only trial on the issue thus far, have led the WHO to endorse rectal artesunate as a pre-referral treatment for severe malaria. In the light of its public health importance and because its scientific quality has not been assessed for a systematic review, our paper provides a detailed evaluation of the design, conduct, analysis, reporting, and practical features of this trial. RESULTS We performed a checklist-based and an in-depth evaluation of the trial. The evaluation criteria were based on the CONSORT statement for reporting clinical trials, the clinical trial methodology literature, and practice in malaria research. Our main findings are: The inclusion and exclusion criteria and the sample size justification are not stated. Many clearly ineligible subjects were enrolled. The training of the recruiters does not appear to have been satisfactory. There was excessive between center heterogeneity in design and conduct. Outcome evaluation schedule was not defined, and in practice, became too wide. Large gaps in the collection of key data were evident. Primary endpoints were inconsistently utilized and reported; an overall analysis of the outcomes was not done; analyses of time to event data had major flaws; the stated intent-to-treat analysis excluded a third of the randomized subjects; the design-indicated stratified or multi-variate analysis was not done; many improper subgroups were analyzed in a post-hoc fashion; the analysis and reporting metric was deficient. There are concerns relating to patient welfare at some centers. Exclusion of many cases from data analysis compromised external validity. A bias-controlled reanalysis of available data does not lend support to the conclusions drawn by the authors. CONCLUSIONS This trial has numerous serious deficiencies in design, implementation, and methods of data analysis. Interpretation and manner of reporting are wanting, and the applicability of the findings is unclear. The trial conduct could have been improved to better protect patient welfare. The totality of these problems make it a flawed study whose conclusions remain subject to appreciable doubt.
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Affiliation(s)
- Karim F Hirji
- Department of Epidemiology and Biostatistics, Muhimbili University of Health and Allied Sciences, United Nations Road, Dar es Salaam, Tanzania
| | - Zulfiqarali G Premji
- Department of Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, United Nations Road, Da res Salaam, Tanzania
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Proietti C, Pettinato DD, Kanoi BN, Ntege E, Crisanti A, Riley EM, Egwang TG, Drakeley C, Bousema T. Continuing intense malaria transmission in northern Uganda. Am J Trop Med Hyg 2011; 84:830-7. [PMID: 21540398 DOI: 10.4269/ajtmh.2011.10-0498] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Recent reports of reductions in malaria transmission in several African countries have resulted in optimism that malaria can be eliminated in parts of Africa where it is currently endemic. It is not known whether these trends are global or whether they are also present in areas where political instability has hindered effective malaria control. We determined malaria parasite carriage and age-dependent antibody responses to Plasmodium falciparum antigens in cross-sectional surveys in Apac, northern Uganda that was affected by political unrest. Under-five parasite prevalence was 55.8% (115/206) by microscopy and 71.9% (41/57) by polymerase chain reaction. Plasmodium ovale alone, or as a co-infection, was detected in 8.6% (12/139) and Plasmodium malariae in 4.3% (6/139) of the infections. Age seroprevalence curves gave no indication of recent changes in malaria transmission intensity. Malaria control remains a tremendous challenge in areas that have not benefited from large-scale interventions, illustrated here by the district of Apac.
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Affiliation(s)
- Carla Proietti
- Department of Immunology and Infection, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London, United Kingdom.
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26
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Graz B, Willcox M, Szeless T, Rougemont A. "Test and treat" or presumptive treatment for malaria in high transmission situations? A reflection on the latest WHO guidelines. Malar J 2011; 10:136. [PMID: 21599880 PMCID: PMC3123602 DOI: 10.1186/1475-2875-10-136] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2011] [Accepted: 05/20/2011] [Indexed: 11/25/2022] Open
Abstract
Recent WHO guidelines recommend a universal "test and treat" strategy for malaria, mainly by use of rapid diagnostic test (RDT) in all areas. The evidence for this approach is questioned here as there is a risk of over-reliance on parasitological diagnosis in high transmission situations, which still exist. In such areas, when a patient has fever or other malaria symptoms, the presence of Plasmodium spp neither reliably confirms malaria as the cause of the fever, nor excludes the possibility of other diseases. This is because the patient may be an asymptomatic carrier of malaria parasites and suffer from another disease. To allow clinicians to perform their work adequately, local epidemiologic data are necessary. One size does not fit all. If parasite prevalence in the population is low, a diagnostic test is relevant; if the prevalence is high, the test does not provide information of any clinical usefulness, as happens with any test in medicine when the prevalence of the tested characteristic is high in the healthy population. It should also be remembered that, if in some cases anti-malarials are prescribed to parasite-negative patients, this will not increase selection pressure for drug resistance, because the parasite is not there. In high transmission situations at least, other diagnoses should be sought in all patients, irrespective of the presence of malaria parasites. For this, clinical skills (but not necessarily physicians) are irreplaceable, in order to differentiate malaria from other causes of acute fever, such as benign viral infection or potentially dangerous conditions, which can all be present with the parasite co-existing only as a "commensal" or silent undesirable guest.
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Affiliation(s)
- Bertrand Graz
- Institute of Social and Preventive Medicine, University of Geneva, Switzerland.
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27
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Pullan RL, Bukirwa H, Snow RW, Brooker S. Heritability of Plasmodium parasite density in a rural Ugandan community. Am J Trop Med Hyg 2010; 83:990-5. [PMID: 21036825 PMCID: PMC2963957 DOI: 10.4269/ajtmh.2010.10-0049] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Many factors influence variation in Plasmodium infection levels, including parasite/host genetics, immunity, and exposure. Here, we examine the roles of host genetics and exposure in determining parasite density, and test whether effects differ with age. Data for 1,711 residents of an eastern Ugandan community were used in pedigree-based variance component analysis. Heritability of parasite density was 13% (P < 0.001) but was not significant after controlling for shared household. Allowing variance components to vary between children (< 16 years) and adults (≥ 16 years) revealed striking age differences; 26% of variation could be explained by additively acting genes in children (P < 0.001), but there was no genetic involvement in adults. Domestic environment did not explain variation in children and explained 5% in adults (P = 0.09). Genetic effects are an important determinant of parasite density in children in this population, consistent with previous quantitative genetic studies of Plasmodium parasitaemia, although differences in environmental exposure play a lesser role.
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Affiliation(s)
- Rachel L Pullan
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom.
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28
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Raso G, Silué KD, Vounatsou P, Singer BH, Yapi A, Tanner M, Utzinger J, N'Goran EK. Spatial risk profiling of Plasmodium falciparum parasitaemia in a high endemicity area in Côte d'Ivoire. Malar J 2009; 8:252. [PMID: 19906295 PMCID: PMC2783037 DOI: 10.1186/1475-2875-8-252] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2009] [Accepted: 11/11/2009] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The objective of this study was to identify demographic, environmental and socioeconomic risk factors and spatial patterns of Plasmodium falciparum parasitaemia in a high endemicity area of Africa, and to specify how this information can facilitate improved malaria control at the district level. METHODS A questionnaire was administered to about 4,000 schoolchildren in 55 schools in western Côte d'Ivoire to determine children's socioeconomic status and their habit of sleeping under bed nets. Environmental data were obtained from satellite images, digitized ground maps and a second questionnaire addressed to school directors. Finger prick blood samples were collected and P. falciparum parasitaemia determined under a microscope using standardized, quality-controlled methods. Bayesian variogram models were utilized for spatial risk modelling and mapping of P. falciparum parasitaemia at non-sampled locations, assuming stationary and non-stationary underlying spatial dependence. RESULTS Two-thirds of the schoolchildren were infected with P. falciparum and the mean parasitaemia among infected children was 959 parasites/microl of blood. Age, socioeconomic status, not sleeping under a bed net, coverage rate with bed nets and environmental factors (e.g., normalized difference vegetation index, rainfall, land surface temperature and living in close proximity to standing water) were significantly associated with the risk of P. falciparum parasitaemia. After accounting for spatial correlation, age, bed net coverage, rainfall during the main malaria transmission season and distance to rivers remained significant covariates. CONCLUSION It is argued that a massive increase in bed net coverage, particularly in villages in close proximity to rivers, in concert with other control measures, is necessary to bring malaria endemicity down to intermediate or low levels.
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Affiliation(s)
- Giovanna Raso
- Département Environnement et Santé, Centre Suisse de Recherches Scientifiques, Abidjan, Côte d'Ivoire.
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Willcox ML, Sanogo F, Graz B, Forster M, Dakouo F, Sidibe O, Falquet J, Giani S, Diakite C, Diallo D. Rapid diagnostic tests for the home-based management of malaria, in a high-transmission area. ANNALS OF TROPICAL MEDICINE AND PARASITOLOGY 2009; 103:3-16. [PMID: 19173772 DOI: 10.1179/136485909x384983] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Rapid diagnostic tests (RDT) are sometimes recommended to improve the home-based management of malaria. The accuracy of an RDT for the detection of clinical malaria and the presence of malarial parasites has recently been evaluated in a high-transmission area of southern Mali. During the same study, the cost-effectiveness of a 'test-and-treat' strategy for the home-based management of malaria (based on an artemisinin-combination therapy) was compared with that of a 'treat-all' strategy. Overall, 301 patients, of all ages, each of whom had been considered a presumptive case of uncomplicated malaria by a village healthworker, were checked with a commercial RDT (Paracheck-Pf). The sensitivity, specificity, and positive and negative predictive values of this test, compared with the results of microscopy and two different definitions of clinical malaria, were then determined. The RDT was found to be 82.9% sensitive (with a 95% confidence interval of 78.0%-87.1%) and 78.9% (63.9%-89.7%) specific compared with the detection of parasites by microscopy. In the detection of clinical malaria, it was 95.2% (91.3%-97.6%) sensitive and 57.4% (48.2%-66.2%) specific compared with a general practitioner's diagnosis of the disease, and 100.0% (94.5%-100.0%) sensitive but only 30.2% (24.8%-36.2%) specific when compared against the fulfillment of the World Health Organization's (2003) research criteria for uncomplicated malaria. Among children aged 0-5 years, the cost of the 'test-and-treat' strategy, per episode, was about twice that of the 'treat-all' (U.S.$1.0. v. U.S.$0.5). In older subjects, however, the two strategies were equally costly (approximately U.S.$2/episode). In conclusion, for children aged 0-5 years in a high-transmission area of sub-Saharan Africa, use of the RDT was not cost-effective compared with the presumptive treatment of malaria with an ACT. In older patients, use of the RDT did not reduce costs. The question remains whether either of the strategies investigated can be made affordable for the affected population.
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Affiliation(s)
- M L Willcox
- Antenna Technologies, Rue de Neuchâtel 29, 1201 Geneva, Switzerland.
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Crompton PD, Traore B, Kayentao K, Doumbo S, Ongoiba A, Diakite SAS, Krause MA, Doumtabe D, Kone Y, Weiss G, Huang CY, Doumbia S, Guindo A, Fairhurst RM, Miller LH, Pierce SK, Doumbo OK. Sickle cell trait is associated with a delayed onset of malaria: implications for time-to-event analysis in clinical studies of malaria. J Infect Dis 2008; 198:1265-75. [PMID: 18752444 DOI: 10.1086/592224] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
BACKGROUND The World Health Organization (WHO) recently recommended that the time to first malaria episode serve as the primary end point in phase III malaria vaccine trials--the first of which will be held in Africa. Although common red blood cell (RBC) polymorphisms such as sickle hemoglobin (HbS) are known to protect against malaria in Africa, their impact on this end point has not been investigated. METHODS A longitudinal study of 225 individuals aged 2-25 years was conducted in Mali. The association between common RBC polymorphisms and the time to first malaria episode was evaluated. RESULTS Among children aged 2-10 years, sickle cell trait (HbAS) was associated with a 34-day delay in the median time to first malaria episode (P= .017) Cox regression analysis showed that greater age (hazard ratio [HR], 0.87 [95% CI, 0.80-0.94]; (P= .001), HbAS (HR, 0.48 [95% CI, 0.26-0.91]; (P= .024), and asymptomatic parasitemia at enrollment (HR, 0.35 [95% CI, 0.14-0.85]; (P= .021) were associated with decreased malaria risk. CONCLUSION Given the delay in the time to first malaria episode associated with HbAS, it would be advisable for clinical trials and observational studies that use this end point to include Hb typing in the design of studies conducted in areas where HbAS is prevalent.
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Affiliation(s)
- Peter D Crompton
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20852, USA.
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Färnert A, Lebbad M, Faraja L, Rooth I. Extensive dynamics of Plasmodium falciparum densities, stages and genotyping profiles. Malar J 2008; 7:241. [PMID: 19025582 PMCID: PMC2605469 DOI: 10.1186/1475-2875-7-241] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2008] [Accepted: 11/21/2008] [Indexed: 02/17/2024] Open
Abstract
Background Individuals living in areas of high malaria transmission often have different Plasmodium falciparum clones detected in the peripheral blood over time. The aim of this study was to assess the dynamics of asymptomatic P. falciparum infections in a few hours intervals. Methods Capillary blood samples were collected 6-hourly during five days from asymptomatic children in a highly endemic area in Tanzania. Parasite densities and maturation stages were investigated by light microscopy. Types and number of clones were analysed by PCR based genotyping of the polymorphic merozoite surface proteins 1 and 2 genes. Results: Parasite densities and maturation stages fluctuated 48-hourly with a gradual shift into more mature forms. Various genotyping patterns were observed in repeated samples over five days with only few samples with identical profiles. Up to six alleles differed in samples collected six hours apart in the same individual. Conclusion This detailed assessment highlights the extensive within-host dynamics of P. falciparum populations and the limitations of single blood samples to determine parasite densities, stages and genotyping profiles in a malaria infected individual.
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Affiliation(s)
- Anna Färnert
- Unit of Infectious Diseases, Department of Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
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Plasmodium falciparum population dynamics: only snapshots in time? Trends Parasitol 2008; 24:340-4. [PMID: 18617441 DOI: 10.1016/j.pt.2008.04.008] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2008] [Revised: 04/09/2008] [Accepted: 04/24/2008] [Indexed: 11/22/2022]
Abstract
Infections caused by the malaria parasite Plasmodium falciparum often comprise multiple genetically distinct clones. Individuals in endemic areas can have different clones detected in their peripheral blood over a few days or even hours. This reveals interesting within-host dynamics of multiclonal infections, which seem to differ in asymptomatic and symptomatic infections. As well as being an intriguing biological phenomenon that merits further understanding, the extensive dynamics of P. falciparum infections have practical implications on the design and interpretation of malaria studies. Most assessments will, indeed, only provide snapshots of the parasite population dynamics.
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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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O'Meara WP, Hall BF, McKenzie FE. Malaria vaccine efficacy: the difficulty of detecting and diagnosing malaria. Malar J 2007; 6:36. [PMID: 17386083 PMCID: PMC1852320 DOI: 10.1186/1475-2875-6-36] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2007] [Accepted: 03/26/2007] [Indexed: 11/12/2022] Open
Abstract
New sources of funding have revitalized efforts to control malaria. An effective vaccine would be a tremendous asset in the fight against this devastating disease and increasing financial and scientific resources are being invested to develop one. A few candidates have been tested in Phase I and II clinical trials, and several others are poised to begin trials soon. Some studies have been promising, and others disappointing. It is difficult to compare the results of these clinical trials; even independent trials of the same vaccine give highly discrepant results. One major obstacle in evaluating malaria vaccines is the difficulty of diagnosing clinical malaria. This analysis evaluates the impact of diagnostic error, particularly that introduced by microscopy, on the outcome of efficacy trials of malaria vaccines and make recommendations for improving future trials.
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Affiliation(s)
- Wendy Prudhomme O'Meara
- Fogarty International Center, tel 301-496-0426, fax 301-496-8496, NIH, Bethesda, Maryland, USA
| | - B Fenton Hall
- National Institute of Allergy and Infectious Diseases, NIH, Rockville, Maryland, USA
| | - F Ellis McKenzie
- Fogarty International Center, tel 301-496-0426, fax 301-496-8496, NIH, Bethesda, Maryland, USA
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Timmann C, Evans JA, König IR, Kleensang A, Rüschendorf F, Lenzen J, Sievertsen J, Becker C, Enuameh Y, Kwakye KO, Opoku E, Browne ENL, Ziegler A, Nürnberg P, Horstmann RD. Genome-wide linkage analysis of malaria infection intensity and mild disease. PLoS Genet 2007; 3:e48. [PMID: 17381244 PMCID: PMC1829404 DOI: 10.1371/journal.pgen.0030048] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2006] [Accepted: 02/16/2007] [Indexed: 11/22/2022] Open
Abstract
Although balancing selection with the sickle-cell trait and other red blood cell disorders has emphasized the interaction between malaria and human genetics, no systematic approach has so far been undertaken towards a comprehensive search for human genome variants influencing malaria. By screening 2,551 families in rural Ghana, West Africa, 108 nuclear families were identified who were exposed to hyperendemic malaria transmission and were homozygous wild-type for the established malaria resistance factors of hemoglobin (Hb)S, HbC, alpha(+) thalassemia, and glucose-6-phosphate-dehydrogenase deficiency. Of these families, 392 siblings aged 0.5-11 y were characterized for malaria susceptibility by closely monitoring parasite counts, malaria fever episodes, and anemia over 8 mo. An autosome-wide linkage analysis based on 10,000 single-nucleotide polymorphisms was conducted in 68 selected families including 241 siblings forming 330 sib pairs. Several regions were identified which showed evidence for linkage to the parasitological and clinical phenotypes studied, among them a prominent signal on Chromosome 10p15 obtained with malaria fever episodes (asymptotic z score = 4.37, empirical p-value = 4.0 x 10(-5), locus-specific heritability of 37.7%; 95% confidence interval, 15.7%-59.7%). The identification of genetic variants underlying the linkage signals may reveal as yet unrecognized pathways influencing human resistance to malaria.
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Affiliation(s)
- Christian Timmann
- Department of Molecular Medicine, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany.
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36
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Clark IA, Budd AC, Alleva LM, Cowden WB. Human malarial disease: a consequence of inflammatory cytokine release. Malar J 2006; 5:85. [PMID: 17029647 PMCID: PMC1629020 DOI: 10.1186/1475-2875-5-85] [Citation(s) in RCA: 196] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2006] [Accepted: 10/10/2006] [Indexed: 12/24/2022] Open
Abstract
Malaria causes an acute systemic human disease that bears many similarities, both clinically and mechanistically, to those caused by bacteria, rickettsia, and viruses. Over the past few decades, a literature has emerged that argues for most of the pathology seen in all of these infectious diseases being explained by activation of the inflammatory system, with the balance between the pro and anti-inflammatory cytokines being tipped towards the onset of systemic inflammation. Although not often expressed in energy terms, there is, when reduced to biochemical essentials, wide agreement that infection with falciparum malaria is often fatal because mitochondria are unable to generate enough ATP to maintain normal cellular function. Most, however, would contend that this largely occurs because sequestered parasitized red cells prevent sufficient oxygen getting to where it is needed. This review considers the evidence that an equally or more important way ATP deficiency arises in malaria, as well as these other infectious diseases, is an inability of mitochondria, through the effects of inflammatory cytokines on their function, to utilise available oxygen. This activity of these cytokines, plus their capacity to control the pathways through which oxygen supply to mitochondria are restricted (particularly through directing sequestration and driving anaemia), combine to make falciparum malaria primarily an inflammatory cytokine-driven disease.
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Affiliation(s)
- Ian A Clark
- School of Biochemistry and Molecular Biology, Australian National University, Canberra, ACT 0200, Australia
| | - Alison C Budd
- School of Biochemistry and Molecular Biology, Australian National University, Canberra, ACT 0200, Australia
| | - Lisa M Alleva
- School of Biochemistry and Molecular Biology, Australian National University, Canberra, ACT 0200, Australia
| | - William B Cowden
- John Curtin School of Medical Research, Australian National University, Canberra, ACT 0200, Australia
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Diallo D, Graz B, Falquet J, Traoré AK, Giani S, Mounkoro PP, Berthé A, Sacko M, Diakité C. Malaria treatment in remote areas of Mali: use of modern and traditional medicines, patient outcome. Trans R Soc Trop Med Hyg 2006; 100:515-20. [PMID: 16233907 DOI: 10.1016/j.trstmh.2005.08.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2005] [Revised: 08/17/2005] [Accepted: 08/17/2005] [Indexed: 11/20/2022] Open
Abstract
Use of official health services often remains low despite great efforts to improve quality of care. Are informal treatments responsible for keeping a number of patients away from standard care, and if so, why? Through a questionnaire survey with proportional cluster samples, we studied the case histories of 952 children in Bandiagara and Sikasso areas of Mali. Most children with reported uncomplicated malaria were first treated at home (87%) with modern medicines alone (40%), a mixture of modern and traditional treatments (33%), or traditional treatment alone (27%). For severe episodes (224 cases), a traditional treatment alone was used in 50% of the cases. Clinical recovery after uncomplicated malaria was above 98% with any type of treatment. For presumed severe malaria, the global mortality rate was 17%; it was not correlated with the type of treatment used (traditional or modern, at home or elsewhere). In the study areas, informal treatments divert a high proportion of patients away from official health services. Patients' experience that outcome after standard therapeutic itineraries is not better than after alternative care may help to explain low use of official health services. We need to study whether some traditional treatments available in remote villages should be considered real, recommendable first aid.
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Affiliation(s)
- Drissa Diallo
- Département de Médecine Traditionnelle (DMT), Bamako, Mali
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38
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Perneger TV, Szeless T, Rougemont A. Utility of the detection of Plasmodium parasites for the diagnosis of malaria in endemic areas. BMC Infect Dis 2006; 6:81. [PMID: 16670024 PMCID: PMC1475866 DOI: 10.1186/1471-2334-6-81] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2006] [Accepted: 05/02/2006] [Indexed: 11/23/2022] Open
Abstract
Background In populations where the prevalence of infection with Plasmodium parasites is high, blood tests that identify Plasmodium parasites in patients with fever may lead to false positive diagnosis of malaria-disease. We characterised the diminishing value of the parasite detection test as a function of the prevalence of infection. Methods We computed the ability of the parasite detection test to identify malaria at various levels of prevalence (0% to 90%), assuming plausible estimates of sensitivity (95% and 85%) and specificity (99% and 95%) for the detection of parasites. In each situation, we computed likelihood ratios of malaria (or absence of malaria) for positive and negative parasite detection tests. Likelihood ratios were classified as clinically useful (≥ 10), intermediate (5–10), or unhelpful (<5). Results Likelihood ratios of positive tests were strongly related to the prevalence of infection in the general population: a positive test was unhelpful when the prevalence was 20% or more, and useful only when prevalence was 5% or less. The sensitivity and specificity of the test had little influence on these results. Likelihood ratios of negative tests were clinically useful when prevalence was 70% or less, but only for high levels of sensitivity (95%). If sensitivity was low (85%), the negative test was at best of intermediate utility, and was unhelpful if the prevalence of asymptomatic infection exceeded 30%. Conclusion Identification of Plasmodium parasites supports a diagnosis of malaria only in areas where the prevalence of Plasmodium infection is low. Wherever this prevalence exceeds about 20%, a positive test is clinically unhelpful.
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Affiliation(s)
- Thomas V Perneger
- Institute of Social and Preventive Medicine, University of Geneva, CH-1211 Geneva, Switzerland
- Quality of Care Service, University Hospitals of Geneva, CH-1211 Geneva, Switzerland
| | - Thomas Szeless
- Institute of Social and Preventive Medicine, University of Geneva, CH-1211 Geneva, Switzerland
| | - André Rougemont
- Institute of Social and Preventive Medicine, University of Geneva, CH-1211 Geneva, Switzerland
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Jafari-Guemouri S, Boudin C, Fievet N, Ndiaye P, Deloron P. Plasmodium falciparum genotype population dynamics in asymptomatic children from Senegal. Microbes Infect 2006; 8:1663-70. [PMID: 16730211 DOI: 10.1016/j.micinf.2006.01.023] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2005] [Revised: 01/25/2006] [Accepted: 01/25/2006] [Indexed: 10/24/2022]
Abstract
In areas where malaria is endemic, infected individuals generally harbor a mixture of genetically distinct Plasmodium falciparum parasite populations. For the first time, we studied temporal variations of blood parasite densities and circulating genotypes in asymptomatic Senegalese children, at time intervals as short as 4-12 h. Twenty-one Senegalese children, presenting with an asymptomatic P. falciparum infection, were sampled eight times within three days. Parasite density was assessed by thick blood smears, and all infecting genotypes were quantified by the fragment-analysis method. Parasite densities showed dramatic fluctuations up to a 1 to 1,000 ratio, with at least one peak of parasite density. Polyclonal infections were detected in all children, with a multiplicity of infection of 5.2-6.8 genotypes per child. A single sample never reflected the full complexity of the parasite populations hosted by a given individual. Genotypes with different behaviors were detected in all children, some genotypes undergoing major fluctuations, while others were highly stable during the follow-up. A single peripheral blood sampling does not reflect the total parasite load. Repeated sampling is needed to have a more detailed scheme of parasite population dynamics and a better knowledge of the true complexity of an infection.
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Affiliation(s)
- Sayeh Jafari-Guemouri
- UR 010, Mother and Child Health in the Tropics, Institut de Recherche pour le Développement (IRD), Faculté de Pharmacie, 4, Avenue de l'Observatoire, Paris, France
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40
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Rogier C, Fusaï T, Pradines B, Trape JF. Comment évaluer la morbidité attribuable au paludisme en zone d’endémie ? Rev Epidemiol Sante Publique 2005; 53:299-309. [PMID: 16227917 DOI: 10.1016/s0398-7620(05)84607-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
There are no specific clinical signs or symptoms of malaria. Fever attacks, anemia, or signs of severity like coma or respiratory distress cannot easily be attributed to malaria in people who are infected most of the time. Ascribing clinical manifestations to malaria is problematic in populations that are regularly exposed to the transmission of human plasmodia. The more transmission is intense and regular, the higher the prevalence of asymptomatic infections. In areas of intense and perennial malaria transmission, more than 90% of the population may be infected and the simple detection of a plasmodial infection is not enough to attribute clinical manifestations to malaria. Naturally acquired anti-malaria immunity permitting asymptomatic infections is incomplete and temporary. It is an obstacle to the estimation of the malaria burden in endemic areas. The positive association between parasite density and fever allows the attribution of clinical attacks to malaria. The relationship between parasitaemia and the risk of fever is not continuous. An age- and endemicity-dependent threshold effect of parasite density has been demonstrated and can be used to distinguish clinical attacks due to malaria from others. Clinical diagnosis and evaluation of malaria are problematic in three situations: in public health to estimate the malaria burden for health services, in clinical research to evaluate treatments or prophylactic measures (drug, vaccine, anti-vectorial devices), and in basic research on pathophysiology, immunology or genetic susceptibility to clinical malaria. No one diagnostic definition nor procedure for detecting cases is adequate for all three purposes. Case detection may be passive (in health structures for example) or active (in population). The choice of methods for diagnosis and recruitment depends on the objectives and whether a "pragmatic" or "explicative" approach is used. The radical differences between these approaches are often unsuspected or ignored.
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MESH Headings
- Adult
- Africa/epidemiology
- Age Factors
- Algorithms
- Biomedical Research
- Child
- Clinical Trials as Topic
- Data Interpretation, Statistical
- Diagnosis, Differential
- Endemic Diseases
- Female
- Humans
- Immunity, Innate
- Infant
- Infant, Newborn
- Malaria Vaccines/administration & dosage
- Malaria, Falciparum/diagnosis
- Malaria, Falciparum/epidemiology
- Malaria, Falciparum/immunology
- Malaria, Falciparum/parasitology
- Malaria, Falciparum/prevention & control
- Malaria, Falciparum/therapy
- Malaria, Falciparum/transmission
- Male
- Parasitemia/diagnosis
- Pregnancy
- Prevalence
- Regression Analysis
- Research
- Risk
- Risk Factors
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Affiliation(s)
- C Rogier
- Unité de Recherche en Biologie et Epidémiologie Parasitaire, IMTSSA-IFR 48, Parc du Pharo, BP46, 13998 Marseille-Armées.
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41
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Garcia A, Dieng AB, Rouget F, Migot-Nabias F, Le Hesran JY, Gaye O. Role of environment and behaviour in familial resemblances of Plasmodium falciparum infection in a population of Senegalese children. Microbes Infect 2005; 6:68-75. [PMID: 14738895 DOI: 10.1016/j.micinf.2003.09.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Despite the importance of both environment and behaviour in vector-borne disease epidemiology, these factors are unable to explain alone the distribution of cases in a community and the diversity of clinical presentations, suggesting the involvement of more individual factors such as age, sex, immunity or genetic background. The existence of a genetic factor involved in the susceptibility/resistance to a disease can be suspected by the demonstration of a familial aggregation of cases or by the stability over time of infectious status (infected vs. uninfected; mean level of parasite density (PD), etc.). These familial resemblances can be explained by shared environment, family habits and behaviours (use of bed nets, field activities, etc.). In this preliminary study, we essentially investigated the influence of environment and behaviour on Plasmodium falciparum infection levels and reported the effects of these factors on the existence of familial resemblances. Our results are consistent with the existence of familial resemblances for both the level of P. falciparum infection and the qualitative infection status (QIS) (infected vs. uninfected) that seem to be more related to shared behaviour and environment than to a genetic factor. However, although familial resemblances decreased significantly when adjusted for shared behaviour and environment, this decrease is around 12% for the variability between families, against only 4.5% of that within families. Furthermore, we also demonstrated that the QIS is remarkably stable over time. Both these results are consistent with the hypothesis of the existence of a strong and complex individual factor involved in the control of infection status.
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Affiliation(s)
- André Garcia
- Institut de Recherche pour le Développement (IRD), Unité de Recherche 010: Santé de la mère et de l'enfant en milieu tropical, BP 1386, Dakar, Senegal.
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42
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Rougemont M, Van Saanen M, Sahli R, Hinrikson HP, Bille J, Jaton K. Detection of four Plasmodium species in blood from humans by 18S rRNA gene subunit-based and species-specific real-time PCR assays. J Clin Microbiol 2005; 42:5636-43. [PMID: 15583293 PMCID: PMC535226 DOI: 10.1128/jcm.42.12.5636-5643.2004] [Citation(s) in RCA: 309] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
There have been reports of increasing numbers of cases of malaria among migrants and travelers. Although microscopic examination of blood smears remains the "gold standard" in diagnosis, this method suffers from insufficient sensitivity and requires considerable expertise. To improve diagnosis, a multiplex real-time PCR was developed. One set of generic primers targeting a highly conserved region of the 18S rRNA gene of the genus Plasmodium was designed; the primer set was polymorphic enough internally to design four species-specific probes for P. falciparum, P. vivax, P. malarie, and P. ovale. Real-time PCR with species-specific probes detected one plasmid copy of P. falciparum, P. vivax, P. malariae, and P. ovale specifically. The same sensitivity was achieved for all species with real-time PCR with the 18S screening probe. Ninety-seven blood samples were investigated. For 66 of them (60 patients), microscopy and real-time PCR results were compared and had a crude agreement of 86% for the detection of plasmodia. Discordant results were reevaluated with clinical, molecular, and sequencing data to resolve them. All nine discordances between 18S screening PCR and microscopy were resolved in favor of the molecular method, as were eight of nine discordances at the species level for the species-specific PCR among the 31 samples positive by both methods. The other 31 blood samples were tested to monitor the antimalaria treatment in seven patients. The number of parasites measured by real-time PCR fell rapidly for six out of seven patients in parallel to parasitemia determined microscopically. This suggests a role of quantitative PCR for the monitoring of patients receiving antimalaria therapy.
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Affiliation(s)
- Mathieu Rougemont
- Institute of Microbiology, University Hospital of Lausanne, Switzerland
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43
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Kublin JG, Patnaik P, Jere CS, Miller WC, Hoffman IF, Chimbiya N, Pendame R, Taylor TE, Molyneux ME. Effect of Plasmodium falciparum malaria on concentration of HIV-1-RNA in the blood of adults in rural Malawi: a prospective cohort study. Lancet 2005; 365:233-40. [PMID: 15652606 DOI: 10.1016/s0140-6736(05)17743-5] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
BACKGROUND Raised HIV viral load in blood has been associated with accelerated disease progression and increased transmission of infection. To assess the effect of Plasmodium falciparum malaria on concentrations of HIV in blood, we did a prospective cohort study in Malawi. METHODS We recruited 367 HIV-1-infected adults. Among 334 people aparasitaemic at baseline, 148 had at least one malaria episode during follow-up and received antimalarial treatment. Of these, 77 had HIV-1-RNA measurements at baseline, during malaria, and post-malaria. We used linear regression with generalised estimating equations to assess effect of four definitions of malaria (any parasitaemia, parasite density > or =2000/microL, febrile parasitaemia, and febrile parasitaemia with parasite density > or =2000/microl) on changes in log HIV-1 RNA, overall and by baseline CD4 count. FINDINGS With malaria defined as any parasitaemia, HIV-1-RNA concentration almost doubled between baseline (median 96215 copies per mL) and malaria (168901 copies per mL), a 0.25 (95% CI 0.11-0.39) log increase in mean RNA concentration. HIV-1-RNA concentration fell to median 82058 copies per mL by about 8-9 weeks post-malaria. Increases in HIV-1-RNA were greatest for people with fever, parasite density 2000/microL or greater, and CD4 count more than 300 cells per muL, in whom concentrations rose from median 38483 copies per mL at baseline to 196098 copies per mL during malaria, a mean log increase of 0.82 (95% CI 0.55-1.10, p<0.0001), and fell to median 75331 copies per mL post-malaria. People who remained aparasitaemic showed no changes in HIV-1-RNA concentration. INTERPRETATION HIV-infected individuals with malaria have a significantly increased viral load, which might enhance HIV transmission and accelerate disease progression.
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Affiliation(s)
- James G Kublin
- Department of Community Health, University of Malawi College of Medicine, Blantyre, Malawi.
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44
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Bereczky S, Montgomery SM, Troye-Blomberg M, Rooth I, Shaw MA, Färnert A. Elevated anti-malarial IgE in asymptomatic individuals is associated with reduced risk for subsequent clinical malaria. Int J Parasitol 2004; 34:935-42. [PMID: 15217732 DOI: 10.1016/j.ijpara.2004.04.007] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2004] [Revised: 04/07/2004] [Accepted: 04/18/2004] [Indexed: 11/23/2022]
Abstract
Immunological characteristics were assessed for prospective risk of clinical malaria in a longitudinally followed population in a holoendemic area of Tanzania. Baseline characteristics including crude Plasmodium falciparum extract-specific IgE and IgG; total IgE; and parasitological indices, e.g. number of P. falciparum clones, were investigated among 700 asymptomatic individuals. Cox regression analysis estimated the risk of succumbing to a new clinical episode during a 40 weeks follow up. High anti-P. falciparum IgE levels were associated with reduced risk of acute malaria in all age groups independently of total IgE levels. Statistically significant reduced odds ratio of 0.26 (95% CI, 0.09-0.72, P=0.010) and 0.44 (95% CI, 0.19-0.99, P=0.047) for the two highest fifths, respectively was observed after adjustment for age, sex, total IgE, numbers of parasite clones per infection and HIV-1 seropositivity. In contrast, high levels of malaria specific IgG or total IgE were not associated with reduced risk to succumb to a new clinical episode. A protective effect of asymptomatic multiclonal P. falciparum infections was also confirmed. For the first time, anti-malarial IgE levels in asymptomatic individuals in endemic area are found to be associated with reduced risk for subsequent malaria disease. Specific IgE antibodies may play role in maintaining anti-malarial immunity, or indicate other aspects of immune function relevant for protection against malaria.
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Affiliation(s)
- Sándor Bereczky
- Infectious Diseases Unit, Karolinska University Hospital, Karolinska Institutet, S-171 76 Stockholm, Sweden.
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45
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Winch PJ, Bagayoko A, Diawara A, Kané M, Thiéro F, Gilroy K, Daou Z, Berthé Z, Swedberg E. Increases in correct administration of chloroquine in the home and referral of sick children to health facilities through a community-based intervention in Bougouni District, Mali. Trans R Soc Trop Med Hyg 2004; 97:481-90. [PMID: 15307407 DOI: 10.1016/s0035-9203(03)80001-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Save the Children/USA in collaboration with the Ministry of Health of Mali has established over 300 village drug kits in southern Mali since 1996. A cluster-randomized trial was conducted between November 2001 and February 2002 in 10 health zones of Bougouni District to evaluate an intervention to (i) improve the skills of the village drug kit managers to counsel parents on correct home administration of chloroquine (CQ), and (ii) increase the referral of sick children to community health centres (CHC). Children's carers were interviewed 5 d after the sale of CQ about knowledge of danger signs requiring referral, quality of counselling, administration of CQ, and referral. The intervention was associated with significant increases in knowledge of danger signs requiring referral, reported quality of counselling by the manger of the drug kit, and correct administration of CQ in the home. Parents reported that 42.1% of children in the intervention group were referred to the CHC by the drug kit manager compared with 11.2% in the comparison group (odds ratio = 7.12, 95% CI 2.62-19.38). CHC registers indicated that 87.0% of referrals recorded in drug kit referral notebooks arrived at the health centre. Further research is needed to increase the effectiveness of the counselling and the community referral mechanism tested in this study.
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Affiliation(s)
- P J Winch
- Department of International Health, Social and Behavioral Interventions Program, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA.
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46
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Mebrahtu T, Stoltzfus RJ, Chwaya HM, Jape JK, Savioli L, Montresor A, Albonico M, Tielsch JM. Low-dose daily iron supplementation for 12 months does not increase the prevalence of malarial infection or density of parasites in young Zanzibari children. J Nutr 2004; 134:3037-41. [PMID: 15514272 DOI: 10.1093/jn/134.11.3037] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Conflicting evidence exists on the possible role of iron supplementation in the predisposition to malaria infection or the enhancement of its clinical severity. Where anemia prevalence is >40%, current guidelines are to provide low-dose daily iron to young children for up to 18 mo. Earlier studies used doses higher than the current guidelines, intermittent doses, or have supplemented for durations < or = 4 mo. We aimed to assess the effect of low-dose, long-term iron supplementation on malaria infection using a double-blind, placebo-controlled, randomized design, and to examine possible subgroup effects by season and child age. The study was conducted in Pemba Island, Zanzibar, where Plasmodium falciparum malaria has year-round high transmission. A community-based sample of 614 children 4-71 mo old was randomly allocated to 10 mg/d iron or placebo for 12 mo. Outcome measures were the prevalence and density of malaria infection, which was assessed by blood films at monthly intervals. At baseline, 94.4% were anemic (hemoglobin < 110 g/L), 48.1% were stunted (height-for-age Z-score less than -2) and >80% had malaria-positive blood films. No significant differences in malariometric indices were observed between children in the iron-supplemented and placebo groups. Parasite density was higher in certain months and in younger children, but iron supplementation was not associated with any malarial infection outcome in any season or age subgroup. We conclude that in this environment of high malaria transmission, daily oral low-dose supplementation of iron for 12 mo did not affect the prevalence of malaria infection or parasite density.
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Affiliation(s)
- Tsedal Mebrahtu
- Department of International Health, The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
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47
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Clark IA, Alleva LM, Mills AC, Cowden WB. Pathogenesis of malaria and clinically similar conditions. Clin Microbiol Rev 2004; 17:509-39, table of contents. [PMID: 15258091 PMCID: PMC452556 DOI: 10.1128/cmr.17.3.509-539.2004] [Citation(s) in RCA: 136] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
There is now wide acceptance of the concept that the similarity between many acute infectious diseases, be they viral, bacterial, or parasitic in origin, is caused by the overproduction of inflammatory cytokines initiated when the organism interacts with the innate immune system. This is also true of certain noninfectious states, such as the tissue injury syndromes. This review discusses the historical origins of these ideas, which began with tumor necrosis factor (TNF) and spread from their origins in malaria research to other fields. As well the more established proinflammatory mediators, such as TNF, interleukin-1, and lymphotoxin, the roles of nitric oxide and carbon monoxide, which are chiefly inhibitory, are discussed. The established and potential roles of two more recently recognized contributors, overactivity of the enzyme poly(ADP-ribose) polymerase 1 (PARP-1) and the escape of high-mobility-group box 1 (HMGB1) protein from its normal location into the circulation, are also put in context. The pathogenesis of the disease caused by falciparum malaria is then considered in the light of what has been learned about the roles of these mediators in these other diseases, as well as in malaria itself.
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Affiliation(s)
- Ian A Clark
- School of Biochemistry and Molecular Biology, Australian National University, Canberra, ACT 0200, Australia.
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48
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Snounou G. Cross-species regulation of Plasmodium parasitaemia cross-examined. Trends Parasitol 2004; 20:262-5; discussion 266-7. [PMID: 15147675 DOI: 10.1016/j.pt.2004.03.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Georges Snounou
- Unité de Parasitologie Biomédicale et Centre National de la Recherche Scientifique URA2581, Institut Pasteur, 25 Rue du Dr Roux, 75724 Paris Cedex 15, France.
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49
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Abstract
Falciparum malaria is a complex disease with no simple explanation, affecting organs where the parasite is rare as well as those organs where it is more common. We continue to argue that it can best be understood in terms of excessive stimulation of normally useful pathways mediated by inflammatory cytokines, the prototype being tumor necrosis factor (TNF). These pathways involve downstream mediators, such as nitric oxide (NO) that the host normally uses to control parasites, but which, when uncontrolled, have bioenergetic failure of patient tissues as their predictable end point. Falciparum malaria is no different from many other infectious diseases that are clinically confused with it. The sequestration of parasitized red blood cells, prominent in some tissues but absent in others with equal functional loss, exacerbates, but does not change, these overriding principles. Recent opportunities to stain a wide range of tissues from African pediatric cases of falciparum malaria and sepsis for the inducible NO synthase (iNOS) and migration inhibitory factor (MIF) have strengthened these arguments considerably. The recent demonstration of bioenergetic failure in tissue removed from sepsis patients being able to predict a fatal outcome fulfils a prediction of these principles, and it is plausible that this will be demonstrable in severe falciparum malaria. Understanding the disease caused by falciparum malaria at a molecular level requires an appreciation of the universality of poly(ADP-ribose) polymerase-1 (PARP-1) and Na(+)/K(+)-ATPase and the protean effects of activation by inflammation of the former that include inactivation of the latter.
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Affiliation(s)
- Ian A Clark
- School of Biochemistry and Molecular Biology, Australian National University, ACT 0200, Canberra, Australia.
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Boutlis CS, Tjitra E, Maniboey H, Misukonis MA, Saunders JR, Suprianto S, Weinberg JB, Anstey NM. Nitric oxide production and mononuclear cell nitric oxide synthase activity in malaria-tolerant Papuan adults. Infect Immun 2003; 71:3682-9. [PMID: 12819048 PMCID: PMC161965 DOI: 10.1128/iai.71.7.3682-3689.2003] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2003] [Revised: 02/21/2003] [Accepted: 03/11/2003] [Indexed: 01/17/2023] Open
Abstract
Individuals living in regions of intense malaria transmission exhibit natural immunity that allows them to be without fever and other symptoms for most of the time despite frequent parasitization. Although this tolerance of parasitemia appears to be more effective in children than in adults (as evidenced by lower parasitemia fever thresholds with age), adults do exhibit a degree of tolerance but the mechanism(s) underlying this are unclear. Asymptomatic malaria-exposed children have higher levels of nitric oxide (NO) than children with severe disease, and NO has been proposed as a mediator of malarial tolerance. However, the ability of highly malaria-exposed asymptomatic adults to generate high-level basal NO is unknown, as is the relationship between NO and malaria tolerance in adults. The relationship between NO and malaria parasitemia was therefore determined in asymptomatic adults from Papua, Indonesia. Adults with Plasmodium falciparum parasitemia had markedly increased basal systemic NO production relative to aparasitemic Papuan controls, who in turn produced more NO than healthy controls from a region without malaria. Immunoglobulin E levels were universally elevated in malaria-exposed Papuan subjects, suggesting that the prevalence of intestinal parasitosis may be high and that nonmalarial infection may also contribute to high basal NO production. Basal peripheral blood mononuclear cell (PBMC) NO synthase activity was elevated in Papuans but poorly correlated with systemic NO production, suggesting that NO production in this setting arises not only from PBMCs but also from other tissue and cellular sources. NO production was associated with and may contribute to malaria tolerance in Papuan adults.
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Affiliation(s)
- Craig S Boutlis
- International Health Program, Division of Infectious Diseases, Menzies School of Health Research, Northern Territory University, Casuarina, Australia
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