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Kouna LC, Oyegue-Liabagui SL, Voumbo-Matoumona DF, Lekana-Douki JB. Malaria Prevalence in Asymptomatic and Symptomatic Children Living in Rural, Semi-Urban and Urban Areas in Eastern Gabon. Acta Parasitol 2024; 69:471-482. [PMID: 38194048 PMCID: PMC11001662 DOI: 10.1007/s11686-023-00783-x] [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: 01/10/2023] [Accepted: 12/12/2023] [Indexed: 01/10/2024]
Abstract
BACKGROUND Malaria remains a major public health issue in the world despite a decline in the disease burden. However, though symptomatic malaria is diagnosed and treated, asymptomatic infections remain poorly known and support transmission. This study assessed the prevalence of symptomatic and asymptomatic Plasmodium spp. infections in three areas in Gabon to monitor and evaluate the impact of malaria. METHODS AND RESULTS A cross-sectional study was conducted in three areas of Gabon. Febrile and afebrile children aged 6 months to 15 years were included in this study. Malaria prevalence was determined by microscopy of and using rapid diagnostic test (RDT). Plasmodium spp. species were identified by PCR according to the Snounou method. The data were recorded in Excel, and the statistical analyses were performed using the software R version R 64 × 3.5.0. A total of 2381(333 asymptomatic and 107 symptomatic) children were included. The overall prevalence of malaria was 40% (952/2381), with the majority (77% symptomatic and 98% asymptomatic) of infections caused by Plasmodium falciparum. A high prevalence of malaria was found in infected children in rural and semi-rural areas. In these two areas, a higher prevalence of Plasmodium malariae was observed in asymptomatic. Furthermore, mixed infections were more prevalent in asymptomatic children than in symptomatic. CONCLUSION This study showed that the prevalence of Plasmodium spp. infection varied according to the regions. The main species was Plasmodium falciparum, but in asymptomatic children the prevalence of Plasmodium malariae was high in rural areas. To help fight malaria more effectively asymptomatic infections should be taken into account and treated.
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Affiliation(s)
- Lady Charlène Kouna
- Unité d'Evolution, Epidémiologie et Résistances Parasitaires(UNEEREP), Centre international de Recherche Médicales de Franceville, Franceville, Gabon
| | - Sandrine Lydie Oyegue-Liabagui
- Unité d'Evolution, Epidémiologie et Résistances Parasitaires(UNEEREP), Centre international de Recherche Médicales de Franceville, Franceville, Gabon
- Ecole Doctorale Régionale d'Afrique Centrale en Infectiologie Tropicale, Franceville, Gabon
- Département de Biologie, Faculté des Sciences, Université des Sciences et Techniques de Masuku, Franceville, Gabon
| | - Dominique Fatima Voumbo-Matoumona
- Département Masters/Licences, parcours types des sciences Biologiques, faculté des sciences et Techniques, Université Marien Ngouabi, Brazzaville, Congo
| | - Jean Bernard Lekana-Douki
- Unité d'Evolution, Epidémiologie et Résistances Parasitaires(UNEEREP), Centre international de Recherche Médicales de Franceville, Franceville, Gabon.
- Ecole Doctorale Régionale d'Afrique Centrale en Infectiologie Tropicale, Franceville, Gabon.
- Département de Parasitologie Mycologie et de Médecine Tropicale, Université des Science de la Santé, Libreville, Gabon.
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Baiden F, Fleck S, Leigh B, Ayieko P, Tindanbil D, Otieno T, Lawal B, Tehtor M, Rogers M, Odeny L, Hodges MH, Sonnie M, Samai M, Ishola D, Lowe B, Watson-Jones D, Greenwood B. Prevalence of malaria and helminth infections in rural communities in northern Sierra Leone, a baseline study to inform Ebola vaccine study protocols. PLoS One 2022; 17:e0270968. [PMID: 35793331 PMCID: PMC9258822 DOI: 10.1371/journal.pone.0270968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Accepted: 06/21/2022] [Indexed: 11/18/2022] Open
Abstract
Introduction
Recurrent parasitic infections may influence the immune response to vaccines. In the Partnership for Research on Ebola VACcinations extended follow-UP and clinical research capacity build-UP (PREVAC-UP) study being undertaken in Mambolo, northern Sierra Leone, participants are being followed up to assess the potential impact of exposure to malaria and/or helminth infections on long-term immune response to two Ebola vaccines. To support the development of the assays that will be used in this evaluation, a parasitological survey was conducted in Mambolo between November 2019 and February 2020.
Methods
Healthy individuals aged ≥1 year who were resident in Mambolo Chiefdom were selected using a stratified sampling approach and questionnaires were administered to explore their sociodemographic characteristics. Microscopy was used to detect malaria parasites, intestinal helminths and urinary schistosome infections. Rapid blood tests were used to detect infections with Onchocerca volvulus and Wuchereria bancrofti. We estimated the overall prevalence of these infections and used adjusted logistic regression models to explore risk factors for malaria and hookworm infection.
Results
Eight hundred and fifteen (815) residents, 50.9% of whom were female were surveyed. Overall, 309 (39.1%) of 791 persons tested for malaria had a positive blood slide; Plasmodium falciparum was the dominant species. Helminth infection was detected in 122 (15.0%) of 815 stool samples including three mixed infections. The helminth infections comprised 102 (12.5%) cases of hookworm, 11 (1.3%) cases of Trichuris trichiura, 10 (1.2%) cases of Schistosoma mansoni and two (0.2%) cases of Ascaris lumbricoides. Being male (OR = 2.01, 95% CI 1.15–3.50) and residing in a non-riverine community (OR = 4.02, 95%CI 2.32–6.98) were the factors associated with hookworm infection. Onchocerca volvulus and Wuchereria bancrofti infections were found in 3.3% and 0.4% of participants respectively.
Conclusion
Malaria and hookworm are the most prevalent parasite infections and those most likely to influence long-term immune response to Ebola vaccines among the trial participants.
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Affiliation(s)
- Frank Baiden
- London School of Hygiene & Tropical Medicine, London, United Kingdom
- * E-mail:
| | - Suzanne Fleck
- London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Bailah Leigh
- College of Medicine and Allied Health Sciences, University of Sierra Leone, Freetown, Sierra Leone
| | - Philip Ayieko
- London School of Hygiene & Tropical Medicine, London, United Kingdom
- Mwanza Intervention Trials Unit, National Institute for Medical Research, Mwanza, Tanzania
| | - Daniel Tindanbil
- London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Tuda Otieno
- London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Bolarinde Lawal
- London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Mattu Tehtor
- College of Medicine and Allied Health Sciences, University of Sierra Leone, Freetown, Sierra Leone
| | - Maariam Rogers
- College of Medicine and Allied Health Sciences, University of Sierra Leone, Freetown, Sierra Leone
| | - Lazarus Odeny
- Kenya Medical Research Institute, Centre for Respiratory Diseases Research, Nairobi, Kenya
| | | | | | - Mohamed Samai
- College of Medicine and Allied Health Sciences, University of Sierra Leone, Freetown, Sierra Leone
| | - David Ishola
- London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Brett Lowe
- London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Deborah Watson-Jones
- London School of Hygiene & Tropical Medicine, London, United Kingdom
- Mwanza Intervention Trials Unit, National Institute for Medical Research, Mwanza, Tanzania
| | - Brian Greenwood
- London School of Hygiene & Tropical Medicine, London, United Kingdom
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3
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Okebe J, Dabira E, Jaiteh F, Mohammed N, Bradley J, Drammeh NF, Bah A, Masunaga Y, Achan J, Muela Ribera J, Yeung S, Balen J, Peeters Grietens K, D'Alessandro U. Reactive, self-administered malaria treatment against asymptomatic malaria infection: results of a cluster randomized controlled trial in The Gambia. Malar J 2021; 20:253. [PMID: 34098984 PMCID: PMC8186162 DOI: 10.1186/s12936-021-03761-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Accepted: 05/11/2021] [Indexed: 12/05/2022] Open
Abstract
BACKGROUND Selectively targeting and treating malaria-infected individuals may further decrease parasite carriage in low-burden settings. Using a trans-disciplinary approach, a reactive treatment strategy to reduce Plasmodium falciparum prevalence in participating communities was co-developed and tested. METHODS This is a 2-arm, open-label, cluster-randomized trial involving villages in Central Gambia during the 2017 and 2018 malaria transmission season. Villages were randomized in a 1:1 ratio using a minimizing algorithm. In the intervention arm, trained village health workers delivered a full course of pre-packed dihydroartemisinin-piperaquine to all residents of compounds where clinical cases were reported while in the control arm, compound residents were screened for infection at the time of the index case reporting. All index cases were treated following national guidelines. The primary endpoint was malaria prevalence, determined by molecular methods, at the end of the intervention period. RESULTS The trial was carried out in 50 villages: 34 in 2017 and 16 additional villages in 2018. At the end of the 2018 transmission season, malaria prevalence was 0.8% (16/1924, range 0-4%) and 1.1% (20/1814, range 0-17%) in the intervention and control arms, respectively. The odds of malaria infection were 29% lower in the intervention than in the control arm after adjustment for age (OR 0.71, 95% CI 0.27-1.84, p = 0.48). Adherence to treatment was high, with 98% (964/979) of those treated completing the 3-day treatment. Over the course of the study, only 37 villages, 20 in the intervention and 17 in the control arm, reported at least one clinical case. The distribution of clinical cases by month in both transmission seasons was similar and the odds of new clinical malaria cases during the trial period did not vary between arms (OR 1.04, 95% CI 0.57-1.91, p = 0.893). All adverse events were classified as mild to moderate and resolved completely. CONCLUSION The systematic and timely administration of an anti-malarial treatment to residents of compounds with confirmed malaria cases did not significantly decrease malaria prevalence and incidence in communities where malaria prevalence was already low. Treatment coverage and adherence was very high. Results were strongly influenced by the lower-than-expected malaria prevalence, and by no clinical cases in villages with asymptomatic malaria-infected individuals. TRIAL REGISTRATION This study is registered with ClinicalTrials.gov, NCT02878200. Registered 25 August 2016. https://clinicaltrials.gov/ct2/show/NCT02878200 .
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Affiliation(s)
- Joseph Okebe
- Medical Research Council Unit The Gambia At the London School of Hygiene and Tropical Medicine, Fajara, The Gambia
- Department of International Public Health, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Edgard Dabira
- Medical Research Council Unit The Gambia At the London School of Hygiene and Tropical Medicine, Fajara, The Gambia
| | - Fatou Jaiteh
- Medical Anthropology Unit, Institute of Tropical Medicine, Antwerp, Belgium
- Amsterdam Institute of Social Science Research, Amsterdam, The Netherlands
| | - Nuredin Mohammed
- Medical Research Council Unit The Gambia At the London School of Hygiene and Tropical Medicine, Fajara, The Gambia
| | - John Bradley
- MRC International Statistics and Epidemiology Group, London School of Hygiene and Tropical Medicine, London, UK
| | - Ndey-Fatou Drammeh
- Medical Research Council Unit The Gambia At the London School of Hygiene and Tropical Medicine, Fajara, The Gambia
| | - Amadou Bah
- Medical Research Council Unit The Gambia At the London School of Hygiene and Tropical Medicine, Fajara, The Gambia
| | - Yoriko Masunaga
- Medical Anthropology Unit, Institute of Tropical Medicine, Antwerp, Belgium
- Amsterdam Institute of Social Science Research, Amsterdam, The Netherlands
| | - Jane Achan
- Medical Research Council Unit The Gambia At the London School of Hygiene and Tropical Medicine, Fajara, The Gambia
- Malaria Consortium, Cambridge Heath, London, UK
| | | | - Shunmay Yeung
- Clinical Research Department, London School of Hygiene and Tropical Medicine, London, UK
| | - Julie Balen
- School of Health and Related Research, The University of Sheffield, Sheffield, UK
| | | | - Umberto D'Alessandro
- Medical Research Council Unit The Gambia At the London School of Hygiene and Tropical Medicine, Fajara, The Gambia.
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Omonijo AO, Omonijo A, Okoh HI, Ibrahim AO. Relationship between the Usage of Long-Lasting Insecticide-Treated Bed Nets (LLITNs) and Malaria Prevalence among School-Age Children in Southwestern Nigeria. JOURNAL OF ENVIRONMENTAL AND PUBLIC HEALTH 2021; 2021:8821397. [PMID: 33833812 PMCID: PMC8018844 DOI: 10.1155/2021/8821397] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 02/12/2021] [Accepted: 03/03/2021] [Indexed: 11/29/2022]
Abstract
Purpose The usage of LLITNs in malaria vector control has resulted in the reduction in malaria deaths among higher-risk groups (pregnant women and under-fives). However, there exists asymptomatic infection among older children, thereby making them a reservoir of malaria transmission. This study aimed at assessing the impact of LLITN usage on malaria prevalence among school-age children (SAC) in Ekiti, South Western Nigeria. Methods Cross-sectional, two-stage cluster sampling technique was used to collect data from SAC during May and June 2017. A total of 1313 (Oye LGA: 657 and Ikole LGA: 656) SAC in selected public primary schools participated in the study. Sociodemographic information as well as data on LLITN usage the previous night was obtained using pretested, semistructured questionnaires adapted from the standardized Malaria Indicator Survey (MIS) tools. Malaria infection was diagnosed by using the rapid diagnostic test (RDT) on blood samples that were collected by finger prick from each child. Data were analyzed using the Statistical Package for Social Sciences (SPSS) for Windows software version 26 (SPSS Inc., Chicago, IL, USA). Results Usage of LLITNs among SAC was significantly higher in Ikole LGA than in Oye (p < 0.001). Socioeconomic factors (access to electricity, mother's occupation, and household size) showed significant associations with LLITN usage (p < 0.001) in both Oye and Ikole LGAs. Malaria prevalence was significantly low among SAC utilizing LLITNs in both Oye and Ikole LGAs (p < 0.001). There was a significant association between gender and malaria prevalence among SAC with males having higher prevalence than females (p < 0.001). Socioeconomic factors were significantly associated with malaria prevalence in both LGAs (p < 0.001). Conclusion The usage of LLITNs caused a significant reduction in malaria prevalence among the school-age children in the study areas; hence, sensitization on usage should be scaled up towards malaria elimination.
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Affiliation(s)
| | - Adetunji Omonijo
- Department of Family Medicine, Federal Teaching Hospital, Ido Ekiti, Ekiti State, Nigeria
| | - Hillary Iwegbunem Okoh
- Department of Animal and Environmental Biology, Federal University Oye Ekiti State, Oye Ekiti, Nigeria
| | - Azeez Oyemomi Ibrahim
- Department of Family Medicine, Federal Teaching Hospital, Ido Ekiti, Ekiti State, Nigeria
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5
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Abeles J, Conway DJ. The Gini coefficient as a useful measure of malaria inequality among populations. Malar J 2020; 19:444. [PMID: 33267885 PMCID: PMC7709295 DOI: 10.1186/s12936-020-03489-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Accepted: 11/09/2020] [Indexed: 01/28/2023] Open
Abstract
Background Understanding inequality in infectious disease burden requires clear and unbiased indicators. The Gini coefficient, conventionally used as a macroeconomic descriptor of inequality, is potentially useful to quantify epidemiological heterogeneity. With a potential range from 0 (all populations equal) to 1 (populations having maximal differences), this coefficient is used here to show the extent and persistence of inequality of malaria infection burden at a wide variety of population levels. Methods First, the Gini coefficient was applied to quantify variation among World Health Organization world regions for malaria and other major global health problems. Malaria heterogeneity was then measured among countries within the geographical sub-region where burden is greatest, among the major administrative divisions in several of these countries, and among selected local communities. Data were analysed from previous research studies, national surveys, and global reports, and Gini coefficients were calculated together with confidence intervals using bootstrap resampling methods. Results Malaria showed a very high level of inequality among the world regions (Gini coefficient, G = 0.77, 95% CI 0.66–0.81), more extreme than for any of the other major global health problems compared at this level. Within the most highly endemic geographical sub-region, there was substantial inequality in estimated malaria incidence among countries of West Africa, which did not decrease between 2010 (G = 0.28, 95% CI 0.19–0.36) and 2018 (G = 0.31, 0.22–0.39). There was a high level of sub-national variation in prevalence among states within Nigeria (G = 0.30, 95% CI 0.26–0.35), contrasting with more moderate variation within Ghana (G = 0.18, 95% CI 0.12–0.25) and Sierra Leone (G = 0.17, 95% CI 0.12–0.22). There was also significant inequality in prevalence among local village communities, generally more marked during dry seasons when there was lower mean prevalence. The Gini coefficient correlated strongly with the standard coefficient of variation, which has no finite range. Conclusions The Gini coefficient is a useful descriptor of epidemiological inequality at all population levels, with confidence intervals and interpretable bounds. Wider use of the coefficient would give broader understanding of malaria heterogeneity revealed by multiple types of studies, surveys and reports, providing more accessible insight from available data.
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Affiliation(s)
- Jonathan Abeles
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK.
| | - David J Conway
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK.
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6
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Esayas E, Woyessa A, Massebo F. Malaria infection clustered into small residential areas in lowlands of southern Ethiopia. Parasite Epidemiol Control 2020; 10:e00149. [PMID: 32368628 PMCID: PMC7190761 DOI: 10.1016/j.parepi.2020.e00149] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2018] [Revised: 11/25/2019] [Accepted: 04/15/2020] [Indexed: 11/21/2022] Open
Abstract
Malaria is a complex disease and its distribution is not random in endemic areas, and hence areas with low malaria transmission require fine spatial sampling and careful follow-up to identify the hot spots for effective resource utilization to control malaria. The present study is aimed to assess malaria infection in both humans and mosquitoes in a small residential lowland area of southern Ethiopia from July to December 2016. A repeated cross-sectional household survey was conducted in Kolla-Shara Kebele (village) to describe the distribution of malaria and infectious mosquitoes. For the parasitological surveys, a total of 90 households were randomly selected from five sub-villages in equal proportion. About a quarter of the total households included for the surveys were randomly selected for entomological surveys. A P-value of <0.05 was used as a cut-off point for statistical significance. More than a third (35.1%, 46 of 131) febrile cases were microscopically confirmed malaria positive. Above half (58.7%, 27 of 46) of those positive cases were due to P. falciparum and the rest (41.3%, 19 of 46) were due to P. vivax. This study identified two of the five sub-villages as independent clusters with higher risk of malaria infection. Four times higher relative risk (RR) of malaria infection was documented in Abullo sub-village compared to the others (RR = 3.87; P = 0.002). Most of the falciparum malaria cases were aggregated in these sub-villages. About six infectious bites of An. arabiensis per person was recorded during the survey. The infectious bite per person was 17.0 in Abullo and 10.6 in Erze clusters where higher human infections were detected. It is clearly indicated that a smaller portion of the population carry higher malaria cases and infectious bites. Malaria interventions targeting such areas could be effective in the context of malaria elimination strategy in Ethiopia, which consider district as a planning and implementing unit. Future research would preferably be designed to perform long duration of follow-up to identify the appropriate period for interventions and more participants with more heterogeneous villages and districts.
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Affiliation(s)
- Endashaw Esayas
- Arba Minch University, Department of Biology, Arba Minch, Ethiopia.,Ethiopian Federal Ministry of Health, Harari Regional Health Bureau, Malaria Control and Elimination Program, Harar, Ethiopia
| | - Adugna Woyessa
- Ethiopian Public Health Institute, Addis Ababa, Ethiopia
| | - Fekadu Massebo
- Arba Minch University, Department of Biology, Arba Minch, Ethiopia
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7
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Oyegue-Liabagui SL, Imboumy-Limoukou RK, Kouna CL, Bangueboussa F, Schmitt M, Florent I, Lekana-Douki JB. IgG antibody response against Plasmodium falciparum aminopeptidase 1 antigen in Gabonese children living in Makokou and Franceville. Clin Exp Immunol 2020; 200:287-298. [PMID: 32027020 DOI: 10.1111/cei.13425] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/15/2020] [Indexed: 11/28/2022] Open
Abstract
The search for novel chemical classes of anti-malarial compounds to cope with the current state of chemoresistance of malaria parasites has led to the identification of Plasmodium falciparum aminopeptidase 1 (PfA-M1) as a new therapeutic target. PfA-M1, known to be involved in the hemoglobin digestion cascade which helps to provide most of the amino acids necessary to the parasite's metabolism, is currently considered as a promising target for anti-malarial chemotherapy. However, its immunogenic properties have not yet been tested in the Gabonese population. In Gabon, the prevalence of malaria remains three times higher in semi-urban areas (60·12%) than in urban areas (17·06%). We show that malaria-specific PfA-M1 antibodies are present in children and increase with the level of infection. Children living in semi-urban areas have higher anti-PfA-M1 antibody titers (0·14 ± 0·02 AU) than those living in urban areas (0·08 ± 0·02 AU, P = 0·03), and their antibody titers increase with age (P < 0·0001). Moreover, anti-PfA-M1 antibody titers decrease in children with hyperparasitemia (0·027 ± 0·055 AU) but they remain high in children with low parasite density (0·21 ± 0·034 AU, P = 0·034). In conclusion, our results suggest that malaria-specific PfA-M1 antibodies may play an important role in the immune response of the host against P. falciparum in Gabonese children. Further studies on the role of PfA-M1 during anemia are needed.
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Affiliation(s)
- S L Oyegue-Liabagui
- Laboratoire de Recherches en Immunologie, Parasitologie et Microbiologie, Ecole Doctorale Régionale d'Afrique Centrale en Infectiologie Tropicale (ECODRAC), Université des Sciences et Techniques de Masuku, Franceville, Gabon
| | - R-K Imboumy-Limoukou
- Unité d'Evolution Epidémiologie et Résistances Parasitaires (UNEEREP), Centre International de Recherches Médicales de Franceville (CIRMF), Franceville, Gabon
| | - C L Kouna
- Unité d'Evolution Epidémiologie et Résistances Parasitaires (UNEEREP), Centre International de Recherches Médicales de Franceville (CIRMF), Franceville, Gabon
| | - F Bangueboussa
- Laboratoire de Recherches en Immunologie, Parasitologie et Microbiologie, Ecole Doctorale Régionale d'Afrique Centrale en Infectiologie Tropicale (ECODRAC), Université des Sciences et Techniques de Masuku, Franceville, Gabon.,Unité d'Evolution Epidémiologie et Résistances Parasitaires (UNEEREP), Centre International de Recherches Médicales de Franceville (CIRMF), Franceville, Gabon
| | - M Schmitt
- Université de Haute-Alsace, Université de Strasbourg, Mulhouse, France
| | - I Florent
- Molécules de Communication et Adaptation des Microorganismes (MCAM, UMR 7245), Muséum National d'Histoire Naturelle, Paris, France
| | - J B Lekana-Douki
- Unité d'Evolution Epidémiologie et Résistances Parasitaires (UNEEREP), Centre International de Recherches Médicales de Franceville (CIRMF), Franceville, Gabon.,Département de Parasitologie-Mycologie, Université des Sciences de la Santé, Libreville, Gabon
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8
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Otto TD, Assefa SA, Böhme U, Sanders MJ, Kwiatkowski D, Berriman M, Newbold C. Evolutionary analysis of the most polymorphic gene family in falciparum malaria. Wellcome Open Res 2019; 4:193. [PMID: 32055709 PMCID: PMC7001760 DOI: 10.12688/wellcomeopenres.15590.1] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/26/2019] [Indexed: 12/22/2022] Open
Abstract
The var gene family of the human malaria parasite Plasmodium falciparum encode proteins that are crucial determinants of both pathogenesis and immune evasion and are highly polymorphic. Here we have assembled nearly complete var gene repertoires from 2398 field isolates and analysed a normalised set of 714 from across 12 countries. This therefore represents the first large scale attempt to catalogue the worldwide distribution of var gene sequences We confirm the extreme polymorphism of this gene family but also demonstrate an unexpected level of sequence sharing both within and between continents. We show that this is likely due to both the remnants of selective sweeps as well as a worrying degree of recent gene flow across continents with implications for the spread of drug resistance. We also address the evolution of the var repertoire with respect to the ancestral genes within the Laverania and show that diversity generated by recombination is concentrated in a number of hotspots. An analysis of the subdomain structure indicates that some existing definitions may need to be revised From the analysis of this data, we can now understand the way in which the family has evolved and how the diversity is continuously being generated. Finally, we demonstrate that because the genes are distributed across the genome, sequence sharing between genotypes acts as a useful population genetic marker.
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Affiliation(s)
- Thomas D. Otto
- Parasite Genetics, Wellcome Trust Sanger Institute, Hinxton, UK
- Institute of Infection, Immunity & Inflammation, MVLS, University of Glasgow, Glasgow, UK
| | - Sammy A. Assefa
- Parasite Genetics, Wellcome Trust Sanger Institute, Hinxton, UK
| | - Ulrike Böhme
- Parasite Genetics, Wellcome Trust Sanger Institute, Hinxton, UK
| | | | - Dominic Kwiatkowski
- Parasite Genetics, Wellcome Trust Sanger Institute, Hinxton, UK
- The Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Pf3k consortium
- Parasite Genetics, Wellcome Trust Sanger Institute, Hinxton, UK
- Institute of Infection, Immunity & Inflammation, MVLS, University of Glasgow, Glasgow, UK
- The Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
- Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK
| | - Matt Berriman
- Parasite Genetics, Wellcome Trust Sanger Institute, Hinxton, UK
| | - Chris Newbold
- Parasite Genetics, Wellcome Trust Sanger Institute, Hinxton, UK
- Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK
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9
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Biannual versus annual mass azithromycin distribution and malaria seroepidemiology among preschool children in Niger: a sub-study of a cluster randomized trial. Malar J 2019; 18:389. [PMID: 31796025 PMCID: PMC6889587 DOI: 10.1186/s12936-019-3033-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Accepted: 11/24/2019] [Indexed: 12/02/2022] Open
Abstract
Background Biannual mass azithromycin administration to preschool children reduces all-cause mortality, but the mechanism for the effect is not understood. Azithromycin has activity against malaria parasites, and malaria is a leading cause of child mortality in the Sahel. The effect of biannual versus annual azithromycin distribution for trachoma control on serological response to merozoite surface protein 1 (MSP-119), a surrogate for malaria incidence, was evaluated among children in Niger. Methods Markers of malaria exposure were measured in two arms of a factorial randomized controlled trial designed to evaluate targeted biannual azithromycin distribution to children under 12 years of age compared to annual azithromycin to the entire community for trachoma control (N = 12 communities per arm). Communities were treated for 36 months (6 versus 3 distributions). Dried blood spots were collected at 36 months among children ages 1–5 years, and MSP-119 antibody levels were assessed using a bead-based multiplex assay to measure malaria seroprevalence. Results Antibody results were available for 991 children. MSP-119 seropositivity was 62.7% in the biannual distribution arm compared to 68.7% in the annual arm (prevalence ratio 0.91, 95% CI 0.83 to 1.00). Mean semi-quantitative antibody levels were lower in the biannual distribution arm compared to the annual arm (mean difference − 0.39, 95% CI − 0.05 to − 0.72). Conclusions Targeted biannual azithromycin distribution was associated with lower malaria seroprevalence compared to that in a population that received annual distribution. Trial Registration Clinicaltrials.gov NCT00792922
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10
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Omedo I, Mogeni P, Bousema T, Rockett K, Amambua-Ngwa A, Oyier I, C Stevenson J, Y Baidjoe A, de Villiers EP, Fegan G, Ross A, Hubbart C, Jeffreys A, N Williams T, Kwiatkowski D, Bejon P. Micro-epidemiological structuring of Plasmodium falciparum parasite populations in regions with varying transmission intensities in Africa. Wellcome Open Res 2017; 2:10. [PMID: 28612053 PMCID: PMC5445974 DOI: 10.12688/wellcomeopenres.10784.2] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/11/2017] [Indexed: 01/10/2023] Open
Abstract
Background: The first models of malaria transmission assumed a completely mixed and homogeneous population of parasites. Recent models include spatial heterogeneity and variably mixed populations. However, there are few empiric estimates of parasite mixing with which to parametize such models. Methods: Here we genotype 276 single nucleotide polymorphisms (SNPs) in 5199
P. falciparum isolates from two Kenyan sites (Kilifi county and Rachuonyo South district) and one Gambian site (Kombo coastal districts) to determine the spatio-temporal extent of parasite mixing, and use Principal Component Analysis (PCA) and linear regression to examine the relationship between genetic relatedness and distance in space and time for parasite pairs. Results: Using 107, 177 and 82 SNPs that were successfully genotyped in 133, 1602, and 1034 parasite isolates from The Gambia, Kilifi and Rachuonyo South district, respectively, we show that there are no discrete geographically restricted parasite sub-populations, but instead we see a diffuse spatio-temporal structure to parasite genotypes. Genetic relatedness of sample pairs is predicted by relatedness in space and time. Conclusions: Our findings suggest that targeted malaria control will benefit the surrounding community, but unfortunately also that emerging drug resistance will spread rapidly through the population.
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Affiliation(s)
- Irene Omedo
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
| | - Polycarp Mogeni
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
| | - Teun Bousema
- London School of Hygiene and Tropical Medicine, London, UK.,Department of Medical Microbiology, Radboud University Nijmegen Medical Centre, Radboud Institute for Molecular Life Sciences, Nijmegen, Netherlands
| | - Kirk Rockett
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
| | | | - Isabella Oyier
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
| | - Jennifer C Stevenson
- London School of Hygiene and Tropical Medicine, London, UK.,Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Amrish Y Baidjoe
- Department of Medical Microbiology, Radboud University Nijmegen Medical Centre, Radboud Institute for Molecular Life Sciences, Nijmegen, Netherlands
| | - Etienne P de Villiers
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya.,Department of Public Health, Pwani University, Kilifi, Kenya.,Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine Research Building, University of Oxford, Oxford, UK
| | - Greg Fegan
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
| | - Amanda Ross
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland
| | - Christina Hubbart
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Anne Jeffreys
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Thomas N Williams
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya.,Department of Medicine, South Kensington Campus, Imperial College London, London, UK
| | - Dominic Kwiatkowski
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK.,Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, UK
| | - Philip Bejon
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya.,Centre for Clinical Vaccinology and Tropical Medicine, University of Oxford, Oxford, UK
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11
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Omedo I, Mogeni P, Bousema T, Rockett K, Amambua-Ngwa A, Oyier I, Stevenson JC, Baidjoe AY, de Villiers EP, Fegan G, Ross A, Hubbart C, Jeffreys A, Williams TN, Kwiatkowski D, Bejon P. Micro-epidemiological structuring of Plasmodium falciparum parasite populations in regions with varying transmission intensities in Africa. Wellcome Open Res 2017; 2:10. [PMID: 28612053 PMCID: PMC5445974 DOI: 10.12688/wellcomeopenres.10784.1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/11/2017] [Indexed: 12/07/2023] Open
Abstract
Background: The first models of malaria transmission assumed a completely mixed and homogeneous population of parasites. Recent models include spatial heterogeneity and variably mixed populations. However, there are few empiric estimates of parasite mixing with which to parametize such models. Methods: Here we genotype 276 single nucleotide polymorphisms (SNPs) in 5199 P. falciparum isolates from two Kenyan sites (Kilifi county and Rachuonyo South district) and one Gambian site (Kombo coastal districts) to determine the spatio-temporal extent of parasite mixing, and use Principal Component Analysis (PCA) and linear regression to examine the relationship between genetic relatedness and distance in space and time for parasite pairs. Results: Using 107, 177 and 82 SNPs that were successfully genotyped in 133, 1602, and 1034 parasite isolates from The Gambia, Kilifi and Rachuonyo South district, respectively, we show that there are no discrete geographically restricted parasite sub-populations, but instead we see a diffuse spatio-temporal structure to parasite genotypes. Genetic relatedness of sample pairs is predicted by relatedness in space and time. Conclusions: Our findings suggest that targeted malaria control will benefit the surrounding community, but unfortunately also that emerging drug resistance will spread rapidly through the population.
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Affiliation(s)
- Irene Omedo
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
| | - Polycarp Mogeni
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
| | - Teun Bousema
- Department of Medical Microbiology, Radboud University Nijmegen Medical Centre, Radboud Institute for Molecular Life Sciences, Nijmegen, Netherlands
- London School of Hygiene and Tropical Medicine, London, UK
| | - Kirk Rockett
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
| | | | - Isabella Oyier
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
| | - Jennifer C. Stevenson
- London School of Hygiene and Tropical Medicine, London, UK
- Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Amrish Y. Baidjoe
- Department of Medical Microbiology, Radboud University Nijmegen Medical Centre, Radboud Institute for Molecular Life Sciences, Nijmegen, Netherlands
| | - Etienne P. de Villiers
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine Research Building, University of Oxford, Oxford, UK
- Department of Public Health, Pwani University, Kilifi, Kenya
| | - Greg Fegan
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
| | - Amanda Ross
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland
| | - Christina Hubbart
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Anne Jeffreys
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Thomas N. Williams
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
- Department of Medicine, South Kensington Campus, Imperial College London, London, UK
| | - Dominic Kwiatkowski
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
- Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge, UK
| | - Philip Bejon
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
- Centre for Clinical Vaccinology and Tropical Medicine, University of Oxford, Oxford, UK
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12
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Omedo I, Mogeni P, Rockett K, Kamau A, Hubbart C, Jeffreys A, Ochola-Oyier LI, de Villiers EP, Gitonga CW, Noor AM, Snow RW, Kwiatkowski D, Bejon P. Geographic-genetic analysis of Plasmodium falciparum parasite populations from surveys of primary school children in Western Kenya. Wellcome Open Res 2017; 2:29. [PMID: 28944299 PMCID: PMC5527688 DOI: 10.12688/wellcomeopenres.11228.2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/07/2017] [Indexed: 12/30/2022] Open
Abstract
Background. Malaria control, and finally malaria elimination, requires the identification and targeting of residual foci or hotspots of transmission. However, the level of parasite mixing within and between geographical locations is likely to impact the effectiveness and durability of control interventions and thus should be taken into consideration when developing control programs. Methods. In order to determine the geographic-genetic patterns of
Plasmodium falciparum parasite populations at a sub-national level in Kenya, we used the Sequenom platform to genotype 111 genome-wide distributed single nucleotide polymorphic (SNP) positions in 2486 isolates collected from children in 95 primary schools in western Kenya. We analysed these parasite genotypes for genetic structure using principal component analysis and assessed local and global clustering using statistical measures of spatial autocorrelation. We further examined the region for spatial barriers to parasite movement as well as directionality in the patterns of parasite movement. Results. We found no evidence of population structure and little evidence of spatial autocorrelation of parasite genotypes (correlation coefficients <0.03 among parasite pairs in distance classes of 1km, 2km and 5km; p value<0.01). An analysis of the geographical distribution of allele frequencies showed weak evidence of variation in distribution of alleles, with clusters representing a higher than expected number of samples with the major allele being identified for 5 SNPs. Furthermore, we found no evidence of the existence of spatial barriers to parasite movement within the region, but observed directional movement of parasites among schools in two separate sections of the region studied. Conclusions. Our findings illustrate a pattern of high parasite mixing within the study region. If this mixing is due to rapid gene flow, then “one-off” targeted interventions may not be currently effective at the sub-national scale in Western Kenya, due to the high parasite movement that is likely to lead to re-introduction of infection from surrounding regions. However repeated targeted interventions may reduce transmission in the surrounding regions.
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Affiliation(s)
- Irene Omedo
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
| | - Polycarp Mogeni
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
| | - Kirk Rockett
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK
| | - Alice Kamau
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
| | - Christina Hubbart
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK
| | - Anna Jeffreys
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK
| | | | - Etienne P de Villiers
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya.,Department of Public Health, Pwani University, Kilifi, Kenya.,Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, OX3 7LJ, UK
| | - Caroline W Gitonga
- Spatial Health Metrics Group, Kenya Medical Research Institute-Wellcome Trust Research Programme, Nairobi, Kenya
| | - Abdisalan M Noor
- Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, OX3 7LJ, UK.,Spatial Health Metrics Group, Kenya Medical Research Institute-Wellcome Trust Research Programme, Nairobi, Kenya
| | - Robert W Snow
- Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, OX3 7LJ, UK.,Spatial Health Metrics Group, Kenya Medical Research Institute-Wellcome Trust Research Programme, Nairobi, Kenya
| | - Dominic Kwiatkowski
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, UK.,Wellcome Trust Sanger Institute, Cambridge, CB10 1SA, UK
| | - Philip Bejon
- KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya.,Centre for Clinical Vaccinology and Tropical Medicine, Oxford, OX3 7LJ, UK
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13
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Omedo I, Mogeni P, Rockett K, Kamau A, Hubbart C, Jeffreys A, Ochola-Oyier LI, de Villiers EP, Gitonga CW, Noor AM, Snow RW, Kwiatkowski D, Bejon P. Geographic-genetic analysis of Plasmodium falciparum parasite populations from surveys of primary school children in Western Kenya. Wellcome Open Res 2017. [DOI: 10.12688/wellcomeopenres.11228.1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Background. Malaria control, and finally malaria elimination, requires the identification and targeting of residual foci or hotspots of transmission. However, the level of parasite mixing within and between geographical locations is likely to impact the effectiveness and durability of control interventions and thus should be taken into consideration when developing control programs. Methods. In order to determine the geographic-genetic patterns of Plasmodium falciparum parasite populations at a sub-national level in Kenya, we used the Sequenom platform to genotype 111 genome-wide distributed single nucleotide polymorphic (SNP) positions in 2486 isolates collected from children in 95 primary schools in western Kenya. We analysed these parasite genotypes for genetic structure using principal component analysis and assessed local and global clustering using statistical measures of spatial autocorrelation. We further examined the region for spatial barriers to parasite movement as well as directionality in the patterns of parasite movement. Results. We found no evidence of population structure and little evidence of spatial autocorrelation of parasite genotypes (correlation coefficients <0.03 among parasite pairs in distance classes of 1km, 2km and 5km; p value<0.01). An analysis of the geographical distribution of allele frequencies showed weak evidence of variation in distribution of alleles, with clusters representing a higher than expected number of samples with the major allele being identified for 5 SNPs. Furthermore, we found no evidence of the existence of spatial barriers to parasite movement within the region, but observed directional movement of parasites among schools in two separate sections of the region studied. Conclusions. Our findings illustrate a pattern of high parasite mixing within the study region. If this mixing is due to rapid gene flow, then “one-off” targeted interventions may not be currently effective at the sub-national scale in Western Kenya, due to the high parasite movement that is likely to lead to re-introduction of infection from surrounding regions. However repeated targeted interventions may reduce transmission in the surrounding regions.
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14
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Biggs J, Raman J, Cook J, Hlongwana K, Drakeley C, Morris N, Serocharan I, Agubuzo E, Kruger P, Mabuza A, Zitha A, Machaba E, Coetzee M, Kleinschmidt I. Serology reveals heterogeneity of Plasmodium falciparum transmission in northeastern South Africa: implications for malaria elimination. Malar J 2017; 16:48. [PMID: 28126001 PMCID: PMC5270351 DOI: 10.1186/s12936-017-1701-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Accepted: 01/18/2017] [Indexed: 12/22/2022] Open
Abstract
Background It is widely acknowledged that modifications to existing control interventions are required if South Africa is to achieve malaria elimination. Targeting indoor residual spraying (IRS) to areas where cases have been detected is one strategy currently under investigation in northeastern South Africa. This seroprevalence baseline study, nested within a targeted IRS trial, was undertaken to provide insights into malaria transmission dynamics in South Africa and evaluate whether sero-epidemiological practices have the potential to be routinely incorporated into elimination programmes. Methods Filter-paper blood spots, demographic and household survey data were collected from 2710 randomly selected households in 56 study wards located in the municipalities of Ba-Phalaborwa and Bushbuckridge. Blood spots were assayed for Plasmodium falciparum apical membrane antigen-1 and merozoite surface protein-119 blood-stage antigens using an enzyme linked immunosorbent assay. Seroprevalence data were analysed using a reverse catalytic model to determine malaria seroconversion rates (SCR). Geospatial cluster analysis was used to investigate transmission heterogeneity while random effects logistic regression identified risk factors associated with malaria exposure. Results The overall SCR across the entire study site was 0.012 (95% CI 0.008–0.017) per year. Contrasting SCRs, corresponding to distinct geographical regions across the study site, ranging from <0.001 (95% CI <0.001–0.005) to 0.022 (95% CI 0.008–0.062) per annum revealed prominent transmission heterogeneity. Geospatial cluster analysis of household seroprevalence and age-adjusted antibody responses detected statistically significant (p < 0.05) spatial clusters of P. falciparum exposure. Formal secondary education was associated with lower malaria exposure in the sampled population (AOR 0.72, 95% CI 0.56–0.95, p = 0.018). Conclusions Although overall transmission intensity and exposure to malaria was low across both study sites, malaria transmission intensity was highly heterogeneous and associated with low socio-economic status in the region. Findings suggest focal targeting of interventions has the potential to be an appropriate strategy to deploy in South Africa. Furthermore, routinely incorporating sero-epidemiological practices into elimination programmes may prove useful in monitoring malaria transmission intensity in South Africa, and other countries striving for malaria elimination. Electronic supplementary material The online version of this article (doi:10.1186/s12936-017-1701-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Joseph Biggs
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK
| | - Jaishree Raman
- Centre for Opportunistic Tropical and Hospital Infections, National Institute for Communicable Diseases, Johannesburg, South Africa. .,Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa. .,Institute for Sustainable Malaria Control, University of Pretoria, Pretoria, South Africa.
| | - Jackie Cook
- Tropical Epidemiology Group, Department of Infectious Diseases Epidemiology, London School of Hygiene and Tropical Medicine, London, UK
| | - Khumbulani Hlongwana
- School of Nursing and Public Health, University of KwaZulu-Natal, Durban, South Africa
| | - Chris Drakeley
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK
| | - Natashia Morris
- Health GIS Centre, South Africa Medical Research Council, Durban, South Africa
| | - Ishen Serocharan
- Health GIS Centre, South Africa Medical Research Council, Durban, South Africa
| | - Eunice Agubuzo
- Centre for Opportunistic Tropical and Hospital Infections, National Institute for Communicable Diseases, Johannesburg, South Africa.,Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Philip Kruger
- Limpopo Provincial Malaria Control Programme, Polokwane, South Africa
| | - Aaron Mabuza
- Mpumalanga Provincial Malaria Control Programme, Nelspruit, South Africa
| | - Alpheus Zitha
- Mpumalanga Provincial Malaria Control Programme, Nelspruit, South Africa
| | - Elliot Machaba
- Limpopo Provincial Malaria Control Programme, Polokwane, South Africa
| | - Maureen Coetzee
- Centre for Opportunistic Tropical and Hospital Infections, National Institute for Communicable Diseases, Johannesburg, South Africa.,Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Immo Kleinschmidt
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.,Tropical Epidemiology Group, Department of Infectious Diseases Epidemiology, London School of Hygiene and Tropical Medicine, London, UK
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15
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Githinji S, Noor AM, Malinga J, Macharia PM, Kiptui R, Omar A, Njagi K, Waqo E, Snow RW. A national health facility survey of malaria infection among febrile patients in Kenya, 2014. Malar J 2016; 15:591. [PMID: 27931229 PMCID: PMC5146872 DOI: 10.1186/s12936-016-1638-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Accepted: 11/24/2016] [Indexed: 12/03/2022] Open
Abstract
BACKGROUND The use of malaria infection prevalence among febrile patients at clinics has a potential to be a valuable epidemiological surveillance tool. However, routine data are incomplete and not all fevers are tested. This study was designed to screen all fevers for malaria infection in Kenya to explore the epidemiology of fever test positivity rates. METHODS Random sampling was used within five malaria epidemiological zones of Kenya (i.e., high lake endemic, moderate coast endemic, highland epidemic, seasonal low transmission and low risk zones). The selected sample was representative of the number of hospitals, health centres and dispensaries within each zone. Fifty patients with fever presenting to each sampled health facility during the short rainy season were screened for malaria infection using a rapid diagnostic test (RDT). Details of age, pregnancy status and basic demographics were recorded for each patient screened. RESULTS 10,557 febrile patients presenting to out-patient clinics at 234 health facilities were screened for malaria infection. 1633 (15.5%) of the patients surveyed were RDT positive for malaria at 124 (53.0%) facilities. Infection prevalence among non-pregnant patients varied between malaria risk zones, ranging from 0.6% in the low risk zone to 41.6% in the high lake endemic zone. Test positivity rates (TPR) by age group reflected the differences in the intensity of transmission between epidemiological zones. In the lake endemic zone, 6% of all infections were among children aged less than 1 year, compared to 3% in the coast endemic, 1% in the highland epidemic zone, less than 1% in the seasonal low transmission zone and 0% in the low risk zone. Test positivity rate was 31% among febrile pregnant women in the high lake endemic zone compared to 9% in the coast endemic and highland epidemic zones, 3.2% in the seasonal low transmission zone and zero in the low risk zone. CONCLUSION Malaria infection rates among febrile patients, with supporting data on age and pregnancy status presenting to clinics in Kenya can provide invaluable epidemiological data on spatial heterogeneity of malaria and serve as replacements to more expensive community-based infection rates to plan and monitor malaria control.
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Affiliation(s)
- Sophie Githinji
- KEMRI-Wellcome Trust Collaborative Programme, Nairobi, Kenya
| | - Abdisalan M. Noor
- KEMRI-Wellcome Trust Collaborative Programme, Nairobi, Kenya
- Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | | | | | - Rebecca Kiptui
- National Malaria Control Programme, Ministry of Health, Nairobi, Kenya
| | - Ahmeddin Omar
- National Malaria Control Programme, Ministry of Health, Nairobi, Kenya
| | - Kiambo Njagi
- National Malaria Control Programme, Ministry of Health, Nairobi, Kenya
| | - Ejersa Waqo
- National Malaria Control Programme, Ministry of Health, Nairobi, Kenya
| | - Robert W. Snow
- KEMRI-Wellcome Trust Collaborative Programme, Nairobi, Kenya
- Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
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16
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Odongo DO, Wakhungu WJ, Stanley O. Causes of variability in prevalence rates of communicable diseases among secondary school Students in Kisumu County, Kenya. JOURNAL OF PUBLIC HEALTH-HEIDELBERG 2016; 25:161-166. [PMID: 28357195 PMCID: PMC5350242 DOI: 10.1007/s10389-016-0777-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 11/17/2016] [Indexed: 11/28/2022]
Abstract
PURPOSE To determine causes of variability in communicable disease prevalence rates among students in secondary schools to inform policy formulation in the public health sector. METHODS A representative cluster sample size for students was estimated using Fisher et al.'s formula while schools, sub-counties and education zones were clustered and sample size was calculated based on coefficient of variation by school type. Data were collected by questionnaire, medical examination using standard procedures, and focus group discussion, and descriptive analysis was performed on the completed questions. Comparisons between risk factors were made by chi-square and ANOVA analysis using SPSS for Windows (version 15.2; Chicago, IL) software. A p value of < 0.05 was considered statistically significant. RESULTS There was significant variation between communicable disease prevalence rates and age (X24, 0.05 = 2.458), school size (X212, 0.05 = 18.636), gender (X24, 0.05 = 5.723) and class of students (X212, 0.05 = 15.202), and bed and desk spacing (p < 0.05 at 95% CI). However, there was no significant association in prevalence rates between both locality and type of school. There was strong evidence that student age has an effect on prevalence rates. The prevalence rate of malaria was higher in male (14.02%) than female students (6.68%) compared to prevalence of diarrhea, which was higher in female (7.96%) than male students. CONCLUSION This study has revealed that the prevalences of diarrhea, tuberculosis, pneumonia and other respiratory tract infections are lower among female secondary school students than males and that the prevalence of malaria is higher in males than females. Age of secondary school students is a significant vulnerability factor for malaria, diarrhea, tuberculosis and pneumonia, which were the important communicable diseases most prevalent among secondary school students in Kisumu County, Kenya.
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Affiliation(s)
- David Otieno Odongo
- Center for Disaster Management and Humanitarian Assistance, Masinde Muliro University of Science and Technology, Kakamega, Kenya
| | - W J Wakhungu
- Center for Disaster Management and Humanitarian Assistance, Masinde Muliro University of Science and Technology, Kakamega, Kenya
| | - Omuterema Stanley
- Center for Disaster Management and Humanitarian Assistance, Masinde Muliro University of Science and Technology, Kakamega, Kenya
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17
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Bowman NM, Juliano JJ, Snider CJ, Kharabora O, Meshnick SR, Vulule J, John CC, Moormann AM. Longevity of Genotype-Specific Immune Responses to Plasmodium falciparum Merozoite Surface Protein 1 in Kenyan Children from Regions of Different Malaria Transmission Intensity. Am J Trop Med Hyg 2016; 95:580-7. [PMID: 27481054 DOI: 10.4269/ajtmh.15-0710] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 06/02/2016] [Indexed: 01/06/2023] Open
Abstract
Naturally acquired immunity to Plasmodium falciparum presents a changing landscape as malaria control programs and vaccine initiatives are implemented. Determining which immunologic indicators remain surrogates of past infection, as opposed to mediators of protection, led us to compare stability of immune responses across regions with divergent malaria transmission intensities. A repeat cross-sectional study of Kenyan children from a malaria-holoendemic area and an epidemic-prone area was used to examine longitudinal antibody and interferon-gamma (IFN-γ) responses to the 3D7 and FVO variants of merozoite surface protein 1 (MSP1). Antibodies to MSP1 were common in both study populations and did not significantly wane over a 21-month time period. IFN-γ responses were less frequent and rapidly disappeared in children after a prolonged period of no malaria transmission. Antibody and IFN-γ responses rarely correlated with each other; however, MSP1-specific IFN-γ response correlated with lack of concurrent P. falciparum parasitemia of the same genotype, though only statistically significantly in the malaria-holoendemic region (odds ratio = 0.31, 95% confidence interval = 0.12-0.84). This study affirms that antimalarial antibodies are informative for evaluation of history of malaria exposure within individuals, whereas cell-mediated immunity, though short lived under natural exposure conditions, might provide an assessment of recent infection and protection from parasitemia.
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Affiliation(s)
- Natalie M Bowman
- Division of Infectious Diseases, University of North Carolina, School of Medicine, Chapel Hill, North Carolina
| | - Jonathan J Juliano
- Division of Infectious Diseases, University of North Carolina, School of Medicine, Chapel Hill, North Carolina. Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina. Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina.
| | - Cynthia J Snider
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Oksana Kharabora
- Division of Infectious Diseases, University of North Carolina, School of Medicine, Chapel Hill, North Carolina
| | - Steven R Meshnick
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - John Vulule
- Center for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya
| | - Chandy C John
- Ryan White Center for Pediatric Infectious Disease and Global Health, Indiana University, Indianapolis, Indiana
| | - Ann M Moormann
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts
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Oduro AR, Maya ET, Akazili J, Baiden F, Koram K, Bojang K. Monitoring malaria using health facility based surveys: challenges and limitations. BMC Public Health 2016; 16:354. [PMID: 27102913 PMCID: PMC4840858 DOI: 10.1186/s12889-016-2858-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2014] [Accepted: 02/11/2016] [Indexed: 11/30/2022] Open
Abstract
Background Health facility data are more readily accessible for operational planning and evaluation of disease control programmes. The importance, potential challenges and limitations of using facility based survey as an alternative tool for monitoring changes in local malaria epidemiology were examined. Methods The study involved six areas within the administrative divisions of The Gambia. The areas were selected to reflect socioeconomic and malaria transmission intensities across the country. The study design involved an age stratified cross sectional surveys that were conducted during the wet season in 2008 and in the 2009 during the dry season. Participants were patients attending clinics in six health centres and the representative populations from the catchment communities of the health centres. Results Overall participants’ characteristics were mostly not comparable in the two methodological approaches in the different seasons and settings. More females than males were enrolled (55.8 vs. 44.2 %) in all the surveys. Malaria infection was higher in the surveys in health centres than in the communities (p < 0.0001) and also in males than in females (OR = 1.3; p < 0.001). Males were less likely than females to sleep under an insecticide treated net in the communities (OR = 1.6; 95 % CI 1.3, 1.9) and in the health centres (OR = 1.3; 95 % CI 1.1, 1.5). Representativeness of the ethnic groups was better in the health centre surveys than in the community surveys when compared to the 2003 national population census in The Gambia. Conclusion Health facility based survey though a potential tool for monitoring changes in the local epidemiology of malaria will require continuous validation of the facility and participants sociodemograhic characteristics as these may change over time. The effects of health seeking practices on service utilization and health facility surveys as an approach will also need continuous review.
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Affiliation(s)
- Abraham Rexford Oduro
- Navrongo Health Research Centre, P.O. Box 114, Navrongo, Ghana. .,School of Public Health, University of Ghana, P. O. Box LG 13, Legon, Ghana. .,Research and Development Division, Ghana Health Service, PMB, Accra, Ghana.
| | - Ernest Tei Maya
- School of Public Health, University of Ghana, P. O. Box LG 13, Legon, Ghana
| | - James Akazili
- Navrongo Health Research Centre, P.O. Box 114, Navrongo, Ghana
| | - Frank Baiden
- Research and Development Division, Ghana Health Service, PMB, Accra, Ghana
| | - Kwadwo Koram
- Noguchi Memorial Institute of Medical Research, P. O. Box LG 581, Legon, Ghana
| | - Kalifa Bojang
- Medical Research Council Unit, P. O. Box 273, Banjul, The Gambia
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19
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Pothin E, Ferguson NM, Drakeley CJ, Ghani AC. Estimating malaria transmission intensity from Plasmodium falciparum serological data using antibody density models. Malar J 2016; 15:79. [PMID: 26861862 PMCID: PMC4748547 DOI: 10.1186/s12936-016-1121-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Accepted: 01/22/2016] [Indexed: 12/21/2022] Open
Abstract
Background Serological data are increasingly being used to monitor malaria transmission intensity and have been demonstrated to be particularly useful in areas of low transmission where traditional measures such as EIR and parasite prevalence are limited. The seroconversion rate (SCR) is usually estimated using catalytic models in which the measured antibody levels are used to categorize individuals as seropositive or seronegative. One limitation of this approach is the requirement to impose a fixed cut-off to distinguish seropositive and negative individuals. Furthermore, the continuous variation in antibody levels is ignored thereby potentially reducing the precision of the estimate. Methods An age-specific density model which mimics antibody acquisition and loss was developed to make full use of the information provided by serological measures of antibody levels. This was fitted to blood-stage antibody density data from 12 villages at varying transmission intensity in Northern Tanzania to estimate the exposure rate as an alternative measure of transmission intensity. Results The results show a high correlation between the exposure rate estimates obtained and the estimated SCR obtained from a catalytic model (r = 0.95) and with two derived measures of EIR (r = 0.74 and r = 0.81). Estimates of exposure rate obtained with the density model were also more precise than those derived from catalytic models. Conclusion This approach, if validated across different epidemiological settings, could be a useful alternative framework for quantifying transmission intensity, which makes more complete use of serological data.
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Affiliation(s)
- Emilie Pothin
- Department of Infectious Disease Epidemiology, MRC Centre for Outbreak Analysis and Modelling, Imperial College London, London, UK. .,Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland. .,University of Basel, Basel, Switzerland.
| | - Neil M Ferguson
- Department of Infectious Disease Epidemiology, MRC Centre for Outbreak Analysis and Modelling, Imperial College London, London, UK.
| | - Chris J Drakeley
- Department of Immunology, London School of Hygiene and Tropical Medicine, London, UK.
| | - Azra C Ghani
- Department of Infectious Disease Epidemiology, MRC Centre for Outbreak Analysis and Modelling, Imperial College London, London, UK.
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20
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Serology describes a profile of declining malaria transmission in Farafenni, The Gambia. Malar J 2015; 14:416. [PMID: 26492873 PMCID: PMC4618886 DOI: 10.1186/s12936-015-0939-1] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 10/09/2015] [Indexed: 11/23/2022] Open
Abstract
Background Malaria morbidity and mortality has declined in recent years in a number of settings. The ability to describe changes in malaria transmission associated with these declines is important in terms of assessing the potential effects of control interventions, and for monitoring and evaluation purposes. Methods Data from five cross-sectional surveys conducted in Farafenni and surrounding villages on the north bank of River Gambia between 1988 and 2011 were compiled. Antibody responses to MSP-119 were measured in samples from all surveys, data were normalized and expressed as seroprevalence and seroconversion rates (SCR) using different mathematical models. Results Results showed declines in serological metrics with seroprevalence in children aged one to 5 years dropping from 19 % (95 % CI 15–23 %) in 1988 to 1 % (0–2 %) in 2011 (p value for trend in proportions < 0.001) and the SCR dropping from 0.069 year−1 (0.059–0.080) to 0.022 year−1 (0.017–0.028; p = 0.004). The serological data were consistent with previously described drops in both parasite prevalence in children aged 1–5 years (62 %, 57–66 %, in 1988 to 2 %, 0–4 %, in 2011; p < 0.001), and all-cause under five mortality rates (37 per 1000 person-years, 34–41, in 1990 to 17, 15–19, in 2006; p = 0.059). Conclusions This analysis shows accurate reconstruction of historical malaria transmission patterns in the Farafenni area using anti-malarial antibody responses. Demonstrating congruence between serological measures, and conventional clinical and parasitological measures suggests broader utility for serology in monitoring and evaluation of malaria transmission. Electronic supplementary material The online version of this article (doi:10.1186/s12936-015-0939-1) contains supplementary material, which is available to authorized users.
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21
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Mwesigwa J, Okebe J, Affara M, Di Tanna GL, Nwakanma D, Janha O, Opondo K, Grietens KP, Achan J, D'Alessandro U. On-going malaria transmission in The Gambia despite high coverage of control interventions: a nationwide cross-sectional survey. Malar J 2015; 14:314. [PMID: 26268225 PMCID: PMC4535679 DOI: 10.1186/s12936-015-0829-6] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 08/03/2015] [Indexed: 11/13/2022] Open
Abstract
Background As indicators of burden of malaria have substantially decreased in The Gambia, reaching a pre-elimination status may be attainable. Achieving this goal requires in-depth understanding of the current burden of Plasmodium falciparum infection. Methods A nationwide cross-sectional survey was conducted in 2012 to determine the prevalence of P.falciparum infection, and to describe its heterogeneity and associated risk factors. Finger-prick blood samples were collected for microscopy, species-specific PCR and haemoglobin measurement. Results A total of 9,094 participants were included and median
age was 11.9 years (IQR 5, 28). Overall prevalence of P. falciparum was 16.01 % with marked heterogeneity between sites (4.32–36.75 %) and within villages in each site (1.63–49.13 %). Across all sites, 51.17 % (745/1,456) of infections were asymptomatic and 35.61 % (448/1,258) were sub-microscopic. The odds of P. falciparum infection were higher in older children; 5–15 years (OR = 1.90; 95 % CI 1.60–2.26), adults (OR = 1.48; 95 % CI 1.24–1.78) and participants with moderate anaemia (OR = 1.62; 95 % CI 1.32–1.99). Conclusions The current malaria control interventions are not sufficient to interrupt transmission in The Gambia as malaria prevalence is still relatively high in the eastern part of the country. New interventions aiming at interrupting transmission are needed and should be urgently evaluated.
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Affiliation(s)
- Julia Mwesigwa
- Medical Research Council Unit, PO Box 273, Banjul, The Gambia.
| | - Joseph Okebe
- Medical Research Council Unit, PO Box 273, Banjul, The Gambia.
| | - Muna Affara
- Medical Research Council Unit, PO Box 273, Banjul, The Gambia.
| | | | - Davis Nwakanma
- Medical Research Council Unit, PO Box 273, Banjul, The Gambia.
| | - Omar Janha
- Medical Research Council Unit, PO Box 273, Banjul, The Gambia.
| | - Kevin Opondo
- Medical Research Council Unit, PO Box 273, Banjul, The Gambia.
| | - Koen Peeters Grietens
- Institute of Tropical Medicine, Antwerp, Belgium. .,School of International Health Development, Nagasaki University, Nagasaki, Japan. .,Partners for Applied Social Sciences (PASS) International, Tessenderlo, Belgium.
| | - Jane Achan
- Medical Research Council Unit, PO Box 273, Banjul, The Gambia.
| | - Umberto D'Alessandro
- Medical Research Council Unit, PO Box 273, Banjul, The Gambia. .,London School of Hygiene and Tropical Medicine, London, UK. .,Institute of Tropical Medicine, Antwerp, Belgium.
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Helb DA, Tetteh KKA, Felgner PL, Skinner J, Hubbard A, Arinaitwe E, Mayanja-Kizza H, Ssewanyana I, Kamya MR, Beeson JG, Tappero J, Smith DL, Crompton PD, Rosenthal PJ, Dorsey G, Drakeley CJ, Greenhouse B. Novel serologic biomarkers provide accurate estimates of recent Plasmodium falciparum exposure for individuals and communities. Proc Natl Acad Sci U S A 2015; 112:E4438-47. [PMID: 26216993 PMCID: PMC4538641 DOI: 10.1073/pnas.1501705112] [Citation(s) in RCA: 144] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Tools to reliably measure Plasmodium falciparum (Pf) exposure in individuals and communities are needed to guide and evaluate malaria control interventions. Serologic assays can potentially produce precise exposure estimates at low cost; however, current approaches based on responses to a few characterized antigens are not designed to estimate exposure in individuals. Pf-specific antibody responses differ by antigen, suggesting that selection of antigens with defined kinetic profiles will improve estimates of Pf exposure. To identify novel serologic biomarkers of malaria exposure, we evaluated responses to 856 Pf antigens by protein microarray in 186 Ugandan children, for whom detailed Pf exposure data were available. Using data-adaptive statistical methods, we identified combinations of antibody responses that maximized information on an individual's recent exposure. Responses to three novel Pf antigens accurately classified whether an individual had been infected within the last 30, 90, or 365 d (cross-validated area under the curve = 0.86-0.93), whereas responses to six antigens accurately estimated an individual's malaria incidence in the prior year. Cross-validated incidence predictions for individuals in different communities provided accurate stratification of exposure between populations and suggest that precise estimates of community exposure can be obtained from sampling a small subset of that community. In addition, serologic incidence predictions from cross-sectional samples characterized heterogeneity within a community similarly to 1 y of continuous passive surveillance. Development of simple ELISA-based assays derived from the successful selection strategy outlined here offers the potential to generate rich epidemiologic surveillance data that will be widely accessible to malaria control programs.
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Affiliation(s)
- Danica A Helb
- Department of Medicine, University of California, San Francisco, CA 94110; Division of Infectious Diseases, School of Public Health, University of California, Berkeley, CA 94720; Global Health Group, University of California, San Francisco, CA 94158
| | - Kevin K A Tetteh
- Department Immunology and Infection, London School of Hygiene and Tropical Medicine, London WC1E 7HT, United Kingdom
| | - Philip L Felgner
- Division of Infectious Diseases, Department of Medicine, University of California, Irvine, CA 92697
| | - Jeff Skinner
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20852
| | - Alan Hubbard
- Division of Biostatistics, School of Public Health, University of California, Berkeley, CA 94720
| | | | - Harriet Mayanja-Kizza
- Department of Medicine, Makerere University College of Health Sciences, Kampala, Uganda
| | | | - Moses R Kamya
- Department of Medicine, Makerere University College of Health Sciences, Kampala, Uganda
| | - James G Beeson
- Center for Biomedical Research, Burnet Institute for Medical Research and Public Health, Melbourne, VIC, Canada 3004
| | - Jordan Tappero
- Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA 30333
| | - David L Smith
- Spatial Ecology and Epidemiology Group, Department of Zoology, University of Oxford, Oxford OX1 3PS, United Kingdom; Sanaria Institute for Global Health and Tropical Medicine, Rockville, MD 20850
| | - Peter D Crompton
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20852
| | - Philip J Rosenthal
- Department of Medicine, University of California, San Francisco, CA 94110
| | - Grant Dorsey
- Department of Medicine, University of California, San Francisco, CA 94110
| | - Christopher J Drakeley
- Department Immunology and Infection, London School of Hygiene and Tropical Medicine, London WC1E 7HT, United Kingdom
| | - Bryan Greenhouse
- Department of Medicine, University of California, San Francisco, CA 94110;
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Sero-epidemiological evaluation of Plasmodium falciparum malaria in Senegal. Malar J 2015; 14:275. [PMID: 26173958 PMCID: PMC4502940 DOI: 10.1186/s12936-015-0789-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Accepted: 07/01/2015] [Indexed: 11/13/2022] Open
Abstract
Background In Senegal, a significant decrease of malaria transmission intensity has been noted the last years. Parasitaemia has become lower and, therefore, more difficult to detect by microscopy. In the context of submicroscopic parasitaemia, it has become relevant to rely on relevant malaria surveillance tools to better document malaria epidemiology in such settings. Serological markers have been proposed as an essential tool for malaria surveillance. This study aimed to evaluate the sero-epidemiological situation of Plasmodium falciparum malaria in two sentinel sites in Senegal. Methods Cross-sectional surveys were carried out in Velingara (south Senegal) and Keur Soce (central Senegal) between September and October 2010. Children under 10 years old, living in these areas, were enrolled using two-level, random sampling methods. P. falciparum infection was diagnosed using microscopy. P. falciparum antibodies against circumsporozoite protein (CSP), apical membrane protein (AMA1) and merozoite surface protein 1_42 (MSP1_42) were measured by ELISA method. A stepwise logistic regression analysis was done to assess factors associated with P. falciparum antibodies carriage. Results A total of 1,865 children under 10 years old were enrolled. The overall falciparum malaria prevalence was 4.99% with high prevalence in Velingara of 10.03% compared to Keur Soce of 0.3%. Symptomatic malaria cases (fever associated with parasitaemia) represented 17.37%. Seroprevalence of anti-AMA1, anti-MSP1_42 and anti-CSP antibody was 38.12, 41.55 and 40.38%, respectively. The seroprevalence was more important in Velingara and increased with age, active malaria infection and area of residence. Conclusion The use of serological markers can contribute to improved malaria surveillance in areas with declining malaria transmission. This study provided useful baseline information about the sero-epidemiological situation of malaria in Senegal and can contribute to the identification of malaria hot spots in order to concentrate intervention efforts. Trial registration number: PACTR201305000551876 (http://www.pactr.org).
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Ashton RA, Kefyalew T, Rand A, Sime H, Assefa A, Mekasha A, Edosa W, Tesfaye G, Cano J, Teka H, Reithinger R, Pullan RL, Drakeley CJ, Brooker SJ. Geostatistical modeling of malaria endemicity using serological indicators of exposure collected through school surveys. Am J Trop Med Hyg 2015; 93:168-177. [PMID: 25962770 PMCID: PMC4497890 DOI: 10.4269/ajtmh.14-0620] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2014] [Accepted: 02/25/2015] [Indexed: 11/23/2022] Open
Abstract
Ethiopia has a diverse ecology and geography resulting in spatial and temporal variation in malaria transmission. Evidence-based strategies are thus needed to monitor transmission intensity and target interventions. A purposive selection of dried blood spots collected during cross-sectional school-based surveys in Oromia Regional State, Ethiopia, were tested for presence of antibodies against Plasmodium falciparum and P. vivax antigens. Spatially explicit binomial models of seroprevalence were created for each species using a Bayesian framework, and used to predict seroprevalence at 5 km resolution across Oromia. School seroprevalence showed a wider prevalence range than microscopy for both P. falciparum (0–50% versus 0–12.7%) and P. vivax (0–53.7% versus 0–4.5%), respectively. The P. falciparum model incorporated environmental predictors and spatial random effects, while P. vivax seroprevalence first-order trends were not adequately explained by environmental variables, and a spatial smoothing model was developed. This is the first demonstration of serological indicators being used to detect large-scale heterogeneity in malaria transmission using samples from cross-sectional school-based surveys. The findings support the incorporation of serological indicators into periodic large-scale surveillance such as Malaria Indicator Surveys, and with particular utility for low transmission and elimination settings.
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Affiliation(s)
- Ruth A. Ashton
- *Address correspondence to Ruth A. Ashton, Malaria Consortium, Development House, 56-64 Leonard Street, London. E-mail:
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Nankabirwa J, Brooker SJ, Clarke SE, Fernando D, Gitonga CW, Schellenberg D, Greenwood B. Malaria in school-age children in Africa: an increasingly important challenge. Trop Med Int Health 2014; 19:1294-309. [PMID: 25145389 PMCID: PMC4285305 DOI: 10.1111/tmi.12374] [Citation(s) in RCA: 117] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
School-age children have attracted relatively little attention as a group in need of special measures to protect them against malaria. However, increasing success in lowering the level of malaria transmission in many previously highly endemic areas will result in children acquiring immunity to malaria later in life than has been the case in the past. Thus, it can be anticipated that in the coming years there will be an increase in the incidence of both uncomplicated and severe malaria in school-age children in many previously highly endemic areas. In this review, which focuses primarily on Africa, recent data on the prevalence of malaria parasitaemia and on the incidence of clinical malaria in African school-age children are presented and evidence that malaria adversely effects school performance is reviewed. Long-lasting insecticide treated bednets (LLIN) are an effective method of malaria control but several studies have shown that school-age children use LLINs less frequently than other population groups. Antimalarial drugs are being used in different ways to control malaria in school-age children including screening and treatment and intermittent preventive treatment. Some studies of chemoprevention in school-age children have shown reductions in anaemia and improved school performance but this has not been the case in all trials and more research is needed to identify the situations in which chemoprevention is likely to be most effective and, in these situations, which type of intervention should be used. In the longer term, malaria vaccines may have an important role in protecting this important section of the community from malaria. Regardless of the control approach selected, it is important this is incorporated into the overall programme of measures being undertaken to enhance the health of African school-age children.
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Doderer-Lang C, Atchade PS, Meckert L, Haar E, Perrotey S, Filisetti D, Aboubacar A, Pfaff AW, Brunet J, Chabi NW, Akpovi CD, Anani L, Bigot A, Sanni A, Candolfi E. The ears of the African elephant: unexpected high seroprevalence of Plasmodium ovale and Plasmodium malariae in healthy populations in Western Africa. Malar J 2014; 13:240. [PMID: 24946685 PMCID: PMC4071337 DOI: 10.1186/1475-2875-13-240] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Accepted: 05/29/2014] [Indexed: 11/25/2022] Open
Abstract
Background Malaria Is A Life-Threatening Pathology In Africa. Plasmodium Falciparum And Plasmodium Vivax Attract The Most Focus Because Of Their High Prevalence And Mortality. Knowledge About The Prevalence Of The Cryptic Pathogens Plasmodium Ovale And Plasmodium Malariae Is Limited. Thanks To Recombinant Tools, Their Seroprevalence Was Measured For The First Time, As Well As The Prevalence Of Mixed Infections In A Malaria-Asymptomatic Population In Benin, A Malaria-Endemic Country. Methods A Panel Of 1,235 Blood Donations Collected Over Ten Months In Benin Was Used For Validation Of The Recombinant Tools. Recombinant P. Falciparum, P. Malariae, P. Ovale MSP1, And P. Falciparum AMA1 Were Engineered And Validated On A Biobank With Malaria-Infected Patients (N = 144) Using A Species-Speific ELISA Test (Recelisa). Results Were Compared To An ELISA Using A Native P. Falciparum Antigen (NatELISA). Results Among Microscopically Negative African Blood Donors, 85% (1,050/1,235) Present Antibodies Directed To Native P. Falciparum, 94.4% (1,166/1,235) To rPfMSP1 And rPfAMA1, 56.8% (702/1,235) To rPoMSP1, 67.5% (834/1235) To rPmMSP1 And 45.3% Of The Malaria Seropositive Population Had Antibodies Recognizing The Three Species. Conclusion A High Rate Of Antibodies Against P. Ovale And P. Malariae Was Found In Asymptomatic Blood Donors. The Proportion Of Mixed Infections Involving Three Species Was Also Unexpected. These Data Suggest That Determining Seroprevalence For These Cryptic Species Is An Appropriate Tool To Estimate Their Incidence, At The Eve Of Upcoming Anti-P. Falciparum Vaccination Campaigns.
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Affiliation(s)
- Cécile Doderer-Lang
- Institut de Parasitologie et de Pathologie Tropicale Université de Strasbourg, 3, Rue Koeberlé, F67000 Strasbourg, France.
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