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Gonçalves BP, Pérez-Caballero R, Barry A, Gaoussou S, Lewin A, Issiaka D, Keita S, Diarra BS, Mahamar A, Attaher O, Narum DL, Kurtis JD, Dicko A, Duffy PE, Fried M. Natural History of Malaria Infections During Early Childhood in Twins. J Infect Dis 2023; 227:171-178. [PMID: 35849702 DOI: 10.1093/infdis/jiac294] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 06/06/2022] [Accepted: 07/15/2022] [Indexed: 01/19/2023] Open
Abstract
BACKGROUND The frequency and clinical presentation of malaria infections show marked heterogeneity in epidemiological studies. However, deeper understanding of this variability is hampered by the difficulty in quantifying all relevant factors. Here, we report the history of malaria infections in twins, who are exposed to the same in utero milieu, share genetic factors, and are similarly exposed to vectors. METHODS Data were obtained from a Malian longitudinal birth cohort. Samples from 25 twin pairs were examined for malaria infection and antibody responses. Bayesian models were developed for the number of infections during follow-up. RESULTS In 16 of 25 pairs, both children were infected and often developed symptoms. In 8 of 25 pairs, only 1 twin was infected, but usually only once or twice. Statistical models suggest that this pattern is not inconsistent with twin siblings having the same underlying infection rate. In a pair with discordant hemoglobin genotype, parasite densities were consistently lower in the child with hemoglobin AS, but antibody levels were similar. CONCLUSIONS By using a novel design, we describe residual variation in malaria phenotypes in naturally matched children and confirm the important role of environmental factors, as suggested by the between-twin pair heterogeneity in malaria history.
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Affiliation(s)
- Bronner P Gonçalves
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Raúl Pérez-Caballero
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Amadou Barry
- Malaria Research and Training Center, University of Sciences, Techniques and Technologies of Bamako, Bamako, Mali
| | - Santara Gaoussou
- Malaria Research and Training Center, University of Sciences, Techniques and Technologies of Bamako, Bamako, Mali
| | - Alexandra Lewin
- Department of Medical Statistics, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Djibrilla Issiaka
- Malaria Research and Training Center, University of Sciences, Techniques and Technologies of Bamako, Bamako, Mali
| | - Sekouba Keita
- Malaria Research and Training Center, University of Sciences, Techniques and Technologies of Bamako, Bamako, Mali
| | - Bacary S Diarra
- Malaria Research and Training Center, University of Sciences, Techniques and Technologies of Bamako, Bamako, Mali
| | - Almahamoudou Mahamar
- Malaria Research and Training Center, University of Sciences, Techniques and Technologies of Bamako, Bamako, Mali
| | - Oumar Attaher
- Malaria Research and Training Center, University of Sciences, Techniques and Technologies of Bamako, Bamako, Mali
| | - David L Narum
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Jonathan D Kurtis
- Center for International Health Research, Rhode Island Hospital, and Department of Pathology and Laboratory Medicine, Brown University Medical School, Providence, Rhode Island, USA
| | - Alassane Dicko
- Malaria Research and Training Center, University of Sciences, Techniques and Technologies of Bamako, Bamako, Mali
| | - Patrick E Duffy
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Michal Fried
- Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
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Zeleke MT, Gelaye KA, Yenesew MA. Spatiotemporal variation of malaria incidence in parasite clearance interventions and non-intervention areas in the Amhara Regional State, Ethiopia. PLoS One 2022; 17:e0274500. [PMID: 36121809 PMCID: PMC9484658 DOI: 10.1371/journal.pone.0274500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Accepted: 08/29/2022] [Indexed: 11/19/2022] Open
Abstract
Background In Ethiopia, malaria remains a major public health problem. To eliminate malaria, parasite clearance interventions were implemented in six kebeles (the lowest administrative unit) in the Amhara region. Understanding the spatiotemporal distribution of malaria is essential for targeting appropriate parasite clearance interventions to achieve the elimination goal. However, little is known about the spatiotemporal distribution of malaria incidence in the intervention and non-intervention areas. This study aimed to investigate the spatiotemporal distribution of community-based malaria in the intervention and non-intervention kebeles between 2013 and 2018 in the Amhara Regional State, Ethiopia. Methods Malaria data from 212 kebeles in eight districts were downloaded from the District Health Information System2 (DHIS2) database. We used Autoregressive integrated moving average (ARIMA) model to investigate seasonal variations; Anselin Local Moran’s I statistical analysis to detect hotspot and cold spot clusters of malaria cases; and a discrete Poisson model using Kulldorff scan statistics to identify statistically significant clusters of malaria cases. Results The result showed that the reduction in the trend of malaria incidence was higher in the intervention areas compared to the non-intervention areas during the study period with a slope of -0.044 (-0.064, -0.023) and -0.038 (-0.051, -0.024), respectively. However, the difference was not statistically significant. The Global Moran’s I statistics detected the presence of malaria clusters (z-score = 12.05; p<0.001); the Anselin Local Moran’s I statistics identified hotspot malaria clusters at 21 locations in Gendawuha and Metema districts. A statistically significant spatial, temporal, and space-time cluster of malaria cases were detected. Most likely type of spatial clusters of malaria cases (LLR = 195501.5; p <0.001) were detected in all kebeles of Gendawuha and Metema districts. The temporal scan statistic identified three peak periods between September 2013 and November 2015 (LLR = 8727.5; p<0.001). Statistically significant most-likely type of space-time clusters of malaria cases (LLR = 97494.3; p<0.001) were detected at 22 locations from June 2014 to November 2016 in Metema district. Conclusion There was a significant decline in malaria incidence in the intervention areas. There were statistically significant spatiotemporal variations of malaria in the study areas. Applying appropriate parasite clearance interventions is highly recommended for the better achievement of the elimination goal. A more rigorous evaluation of the impact of parasite clearance interventions is recommended.
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Affiliation(s)
- Melkamu Tiruneh Zeleke
- School of Public Health, College of Medicine and Health Sciences, Bahir Dar University, Bahir Dar, Ethiopia
- * E-mail:
| | | | - Muluken Azage Yenesew
- School of Public Health, College of Medicine and Health Sciences, Bahir Dar University, Bahir Dar, Ethiopia
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Abstract
Malaria has been the pre-eminent cause of early mortality in many parts of the world throughout much of the last five thousand years and, as a result, it is the strongest force for selective pressure on the human genome yet described. Around one third of the variability in the risk of severe and complicated malaria is now explained by additive host genetic effects. Many individual variants have been identified that are associated with malaria protection, but the most important all relate to the structure or function of red blood cells. They include the classical polymorphisms that cause sickle cell trait, α-thalassaemia, G6PD deficiency, and the major red cell blood group variants. More recently however, with improving technology and experimental design, others have been identified that include the Dantu blood group variant, polymorphisms in the red cell membrane protein ATP2B4, and several variants related to the immune response. Characterising how these genes confer their effects could eventually inform novel therapeutic approaches to combat malaria. Nevertheless, all together, only a small proportion of the heritable component of malaria resistance can be explained by the variants described so far, underscoring its complex genetic architecture and the need for continued research.
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Affiliation(s)
- Silvia N Kariuki
- Department of Epidemiology, KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya.
| | - Thomas N Williams
- Department of Epidemiology, KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya.
- Department of Medicine, Imperial College of Science and Technology, London, UK.
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Maier CL, Gross PJ, Dean CL, Chonat S, Ip A, McLemore M, El Rassi F, Stowell SR, Josephson CD, Fasano RM. Transfusion-transmitted malaria masquerading as sickle cell crisis with multisystem organ failure. Transfusion 2018. [PMID: 29524230 DOI: 10.1111/trf.14566] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
BACKGROUND Fever accompanying vaso-occlusive crisis is a common presentation in patients with sickle cell disease (SCD) and carries a broad differential diagnosis. Here, we report a case of transfusion-transmitted malaria in a patient with SCD presenting with acute vaso-occlusive crisis and rapidly decompensating to multisystem organ failure (MSOF). CASE REPORT An 18-year-old African American male with SCD was admitted after multiple days of fever and severe generalized body pain. He received monthly blood transfusions as stroke prophylaxis. A source of infection was not readily identified, but treatment was initiated with continuous intravenous fluids and empiric antibiotics. The patient developed acute renal failure, acute hypoxic respiratory failure, and shock. He underwent red blood cell (RBC) exchange transfusion followed by therapeutic plasma exchange and continuous veno-venous hemodialysis. A manual peripheral blood smear revealed intraerythrocytic inclusions suggestive of Plasmodium, and molecular studies confirmed Plasmodium falciparum infection. Intravenous artesunate was given daily for 1 week. A look-back investigation involving two hospitals, multiple blood suppliers, and state and federal public health departments identified the source of malaria as a unit of RBCs transfused 2 weeks prior to admission. CONCLUSIONS Clinical suspicion for transfusion-related adverse events, including hemolytic transfusion reactions and transfusion-transmitted infections, should be high in typically and atypically immunocompromised patient populations (like SCD), especially those on chronic transfusion protocols. Manual blood smear review aids in the evaluation of patients with SCD presenting with severe vaso-occlusive crisis and MSOF and can alert clinicians to the need for initiating aggressive therapy like RBC exchange and artesunate therapy.
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Affiliation(s)
- Cheryl L Maier
- Department of Pathology and Laboratory Medicine, Center for Transfusion and Cellular Therapies, Emory University School of Medicine, Atlanta, Georgia
| | - Phillip J Gross
- Department of Hematology and Oncology, Emory University School of Medicine, Atlanta, Georgia
| | - Christina L Dean
- Department of Pathology and Laboratory Medicine, Center for Transfusion and Cellular Therapies, Emory University School of Medicine, Atlanta, Georgia
| | - Satheesh Chonat
- AFLAC Cancer Center and Blood Disorders Services, Department of Pediatrics, Division of Hematology and Oncology, Emory University School of Medicine, Atlanta, Georgia
| | - Andrew Ip
- Department of Hematology and Oncology, Emory University School of Medicine, Atlanta, Georgia
| | - Morgan McLemore
- Department of Hematology and Oncology, Emory University School of Medicine, Atlanta, Georgia
| | - Fuad El Rassi
- Department of Hematology and Oncology, Emory University School of Medicine, Atlanta, Georgia
| | - Sean R Stowell
- Department of Pathology and Laboratory Medicine, Center for Transfusion and Cellular Therapies, Emory University School of Medicine, Atlanta, Georgia
| | - Cassandra D Josephson
- Department of Pathology and Laboratory Medicine, Center for Transfusion and Cellular Therapies, Emory University School of Medicine, Atlanta, Georgia.,AFLAC Cancer Center and Blood Disorders Services, Department of Pediatrics, Division of Hematology and Oncology, Emory University School of Medicine, Atlanta, Georgia
| | - Ross M Fasano
- Department of Pathology and Laboratory Medicine, Center for Transfusion and Cellular Therapies, Emory University School of Medicine, Atlanta, Georgia
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Kumar A, Singh KP, Bali P, Anwar S, Kaul A, Singh OP, Gupta BK, Kumari N, Noor Alam M, Raziuddin M, Sinha MP, Gourinath S, Sharma AK, Sohail M. iNOS polymorphism modulates iNOS/NO expression via impaired antioxidant and ROS content in P. vivax and P. falciparum infection. Redox Biol 2017; 15:192-206. [PMID: 29268202 PMCID: PMC5738204 DOI: 10.1016/j.redox.2017.12.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 11/30/2017] [Accepted: 12/12/2017] [Indexed: 01/09/2023] Open
Abstract
Nitric oxide (NO) has dicotomic influence on modulating host-parasite interplay, synchronizing physiological orchestrations and diagnostic potential; instigated us to investigate the plausible association and genetic regulation among NO level, components of oxidative stress, iNOS polymorphisms and risk of malaria. Here, we experimentally elucidate that iNOS promoter polymorphisms are associated with risk of malaria; employing mutation specific genotyping, functional interplay using western blot and RT-PCR, quantitative estimation of NO, total antioxidant content (TAC) and reactive oxygen species (ROS). Genotyping revealed significantly associated risk of P. vivax (adjusted OR = 1.92 and 1.72) and P. falciparum (adjusted OR = 1.68 and 1.75) infection with SNP at iNOS-954G/C and iNOS-1173C/T positions, respectively; though vivax showed higher risk of infection. Intriguingly, mutation and infection specific differential upregulation of iNOS expression/NO level was observed and found to be significantly associated with mutant genotypes. Moreover, P. vivax showed pronounced iNOS protein (2.4 fold) and mRNA (2.5 fold) expression relative to healthy subjects. Furthermore, TAC and ROS were significantly decreased in infection; and differentially decreased in mutant genotypes. Our findings endorse polymorphic regulation of iNOS expression, altered oxidant-antioxidant components and evidences of risk association as the hallmark of malaria pathogenesis. iNOS/NO may serve as potential diagnostic marker in assessing clinical malaria. Polymorphism of iNOS revealed significantly associated risk of P. vivax and P. falciparum malaria and vivax showed higher risk of infection. We observed mutation and infection specific differential expression of iNOS/NO cascade. We investigated mutation specific antioxidant and ROS orchestration and observed lower TAC and ROS content in infection. Evaluated the clinical correlation among stratified axillary temperature, NO and haemoglobin content during infection.
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Affiliation(s)
- Amod Kumar
- University Department of Zoology, Vinoba Bhave University, Hazaribag, Jharkhand, India
| | - Krishn Pratap Singh
- University Department of Zoology, Vinoba Bhave University, Hazaribag, Jharkhand, India
| | - Prerna Bali
- National Institute of Malaria Research, Dawarka, Delhi, India
| | - Shadab Anwar
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Asha Kaul
- National Institute of Malaria Research, Dawarka, Delhi, India
| | - Om P Singh
- National Institute of Malaria Research, Dawarka, Delhi, India
| | - Birendra Kumar Gupta
- University Department of Zoology, Vinoba Bhave University, Hazaribag, Jharkhand, India
| | - Nutan Kumari
- Department of Physiology, Patna Medical College and Hospital, Patna, India
| | - Md Noor Alam
- University Department of Zoology, Vinoba Bhave University, Hazaribag, Jharkhand, India
| | - Mohammad Raziuddin
- University Department of Zoology, Vinoba Bhave University, Hazaribag, Jharkhand, India
| | | | | | - Ajay Kumar Sharma
- University Department of Zoology, Vinoba Bhave University, Hazaribag, Jharkhand, India.
| | - Mohammad Sohail
- University Department of Zoology, Vinoba Bhave University, Hazaribag, Jharkhand, India.
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McCann RS, Messina JP, MacFarlane DW, Bayoh MN, Gimnig JE, Giorgi E, Walker ED. Explaining variation in adult Anopheles indoor resting abundance: the relative effects of larval habitat proximity and insecticide-treated bed net use. Malar J 2017; 16:288. [PMID: 28716087 PMCID: PMC5514485 DOI: 10.1186/s12936-017-1938-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Accepted: 07/13/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Spatial determinants of malaria risk within communities are associated with heterogeneity of exposure to vector mosquitoes. The abundance of adult malaria vectors inside people's houses, where most transmission takes place, should be associated with several factors: proximity of houses to larval habitats, structural characteristics of houses, indoor use of vector control tools containing insecticides, and human behavioural and environmental factors in and near houses. While most previous studies have assessed the association of larval habitat proximity in landscapes with relatively low densities of larval habitats, in this study these relationships were analysed in a region of rural, lowland western Kenya with high larval habitat density. METHODS 525 houses were sampled for indoor-resting mosquitoes across an 8 by 8 km study area using the pyrethrum spray catch method. A predictive model of larval habitat location in this landscape, previously verified, provided derivations of indices of larval habitat proximity to houses. Using geostatistical regression models, the association of larval habitat proximity, long-lasting insecticidal nets (LLIN) use, house structural characteristics (wall type, roof type), and peridomestic variables (cooking in the house, cattle near the house, number of people sleeping in the house) with mosquito abundance in houses was quantified. RESULTS Vector abundance was low (mean, 1.1 adult Anopheles per house). Proximity of larval habitats was a strong predictor of Anopheles abundance. Houses without an LLIN had more female Anopheles gambiae s.s., Anopheles arabiensis and Anopheles funestus than houses where some people used an LLIN (rate ratios, 95% CI 0.87, 0.85-0.89; 0.84, 0.82-0.86; 0.38, 0.37-0.40) and houses where everyone used an LLIN (RR, 95% CI 0.49, 0.48-0.50; 0.39, 0.39-0.40; 0.60, 0.58-0.61). Cooking in the house also reduced Anopheles abundance across all species. The number of people sleeping in the house, presence of cattle near the house, and house structure modulated Anopheles abundance, but the effect varied with Anopheles species and sex. CONCLUSIONS Variation in the abundance of indoor-resting Anopheles in rural houses of western Kenya varies with clearly identifiable factors. Results suggest that LLIN use continues to function in reducing vector abundance, and that larval source management in this region could lead to further reductions in malaria risk by reducing the amount of an obligatory resource for mosquitoes near people's homes.
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Affiliation(s)
- Robert S. McCann
- Department of Entomology, Michigan State University, East Lansing, MI USA
| | - Joseph P. Messina
- Department of Geography, Environment, and Spatial Sciences, Michigan State University, East Lansing, MI USA
| | | | - M. Nabie Bayoh
- Centre for Global Health Research, Kenya Medical Research Institute/Centers for Disease Control and Prevention, Kisumu, Kenya
| | - John E. Gimnig
- Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, GA USA
| | - Emanuele Giorgi
- Lancaster Medical School, Lancaster University, Lancaster, UK
| | - Edward D. Walker
- Department of Microbiology and Molecular Genetics, Michigan State University, 567 Wilson Road, 2215 Biomedical Physical Sciences Building, East Lansing, MI 48824-4320 USA
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Signatures of malaria-associated pathology revealed by high-resolution whole-blood transcriptomics in a rodent model of malaria. Sci Rep 2017; 7:41722. [PMID: 28155887 PMCID: PMC5290525 DOI: 10.1038/srep41722] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Accepted: 12/28/2016] [Indexed: 11/09/2022] Open
Abstract
The influence of parasite genetic factors on immune responses and development of severe pathology of malaria is largely unknown. In this study, we performed genome-wide transcriptomic profiling of mouse whole blood during blood-stage infections of two strains of the rodent malaria parasite Plasmodium chabaudi that differ in virulence. We identified several transcriptomic signatures associated with the virulent infection, including signatures for platelet aggregation, stronger and prolonged anemia and lung inflammation. The first two signatures were detected prior to pathology. The anemia signature indicated deregulation of host erythropoiesis, and the lung inflammation signature was linked to increased neutrophil infiltration, more cell death and greater parasite sequestration in the lungs. This comparative whole-blood transcriptomics profiling of virulent and avirulent malaria shows the validity of this approach to inform severity of the infection and provide insight into pathogenic mechanisms.
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Donnelly B, Berrang-Ford L, Labbé J, Twesigomwe S, Lwasa S, Namanya DB, Harper SL, Kulkarni M, Ross NA, Michel P. Plasmodium falciparum malaria parasitaemia among indigenous Batwa and non-indigenous communities of Kanungu district, Uganda. Malar J 2016; 15:254. [PMID: 27146298 PMCID: PMC4855715 DOI: 10.1186/s12936-016-1299-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Accepted: 04/18/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The indigenous Batwa of southwestern Uganda are among the most highly impoverished populations in Uganda, yet there is negligible research on the prevalence of malaria in this population. Plasmodium falciparum malaria parasitaemia prevalence was estimated in an indigenous Batwa and a non-indigenous neighbouring population, and an exploration of modifiable risk factors was carried out to identify potential entry points for intervention. Additionally, evidence of zooprophylaxis was assessed, hypothesizing that livestock ownership may play a role in malaria risk. METHODS Two cross-sectional surveys of Batwa and non-Batwa communities were carried out in Kanungu District, Uganda in July 2013 and April 2014 based on a census of adult Batwa and a two-stage systematic random sample of adult non-Batwa in ten Local Councils where Batwa settlements are located. A community-based questionnaire and antigen rapid diagnostic test for P. falciparum were carried out in the cross-sectional health surveys. A multivariable logistic regression model was built to identify risk factors associated with positive malaria diagnostic test. A subset analysis of livestock owners tested for zooprophylaxis. RESULTS Batwa experienced higher prevalence of malaria parasitaemia than non-Batwa (9.35 versus 4.45 %, respectively) with over twice the odds of infection (OR 2.21, 95 % CI 1.23-3.98). Extreme poverty (OR 1.96, 95 % CI 0.98-3.94) and having an iron sheet roof (OR 2.54, 95 % CI 0.96-6.72) increased the odds of infection in both Batwa and non-Batwa. Controlling for ethnicity, wealth, and bed net ownership, keeping animals inside the home at night decreased the odds of parasitaemia among livestock owners (OR 0.29, 95 % CI 0.09-0.94). CONCLUSION A health disparity exists between indigenous Batwa and non-indigenous community members with Batwa having higher prevalence of malaria relative to non-Batwa. Poverty was associated with increased odds of malaria infection for both groups. Findings suggest that open eaves and gaps in housing materials associated with iron sheet roofing represent a modifiable risk factor for malaria, and may facilitate mosquito house entry; larger sample sizes will be required to confirm this finding. Evidence for possible zooprophylaxis was observed among livestock owners in this population for those who sheltered animals inside the home at night.
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Affiliation(s)
- Blánaid Donnelly
- />Department of Geography, McGill University, Burnside Hall Building, 805 Sherbrooke St West, Montreal, QC H3A 0B9 Canada
| | - Lea Berrang-Ford
- />Department of Geography, McGill University, Burnside Hall Building, 805 Sherbrooke St West, Montreal, QC H3A 0B9 Canada
| | - Jolène Labbé
- />Department of Geography, McGill University, Burnside Hall Building, 805 Sherbrooke St West, Montreal, QC H3A 0B9 Canada
| | | | - Shuaib Lwasa
- />Department of Geography, Geoinformatics and Climatic Sciences, School of Forestry, Environmental and Geographical Sciences, CAES, Makerere University, P.O Box 7062, Kampala, Uganda
| | | | - Sherilee L. Harper
- />Department of Population Medicine, Ontario Veterinary College, University of Guelph, Guelph, ON N1G 2W1 Canada
| | - Manisha Kulkarni
- />School of Epidemiology, Public Health and Preventive Medicine, University of Ottawa, 600 Peter Morand Cres., 301E, Ottawa, ON K1H 8M5 Canada
| | - Nancy A. Ross
- />Department of Geography, McGill University, Burnside Hall Building, 805 Sherbrooke St West, Montreal, QC H3A 0B9 Canada
| | - IHACC Research Team
- />Department of Geography, McGill University, Burnside Hall Building, 805 Sherbrooke St West, Montreal, QC H3A 0B9 Canada
- />Batwa Development Program, Buhoma, Kanungu District, Uganda
- />Department of Geography, Geoinformatics and Climatic Sciences, School of Forestry, Environmental and Geographical Sciences, CAES, Makerere University, P.O Box 7062, Kampala, Uganda
- />Ministry of Health, Plot 6 Lourdel Rd, P.O Box 7272, Kampala, Uganda
- />Department of Population Medicine, Ontario Veterinary College, University of Guelph, Guelph, ON N1G 2W1 Canada
- />School of Epidemiology, Public Health and Preventive Medicine, University of Ottawa, 600 Peter Morand Cres., 301E, Ottawa, ON K1H 8M5 Canada
- />Office of the Chief Science Officer, Public Health Agency of Canada, 130 Colonnade Road, Ottawa, ON K1A 0K9 Canada
| | - Pascal Michel
- />Office of the Chief Science Officer, Public Health Agency of Canada, 130 Colonnade Road, Ottawa, ON K1A 0K9 Canada
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Dewasurendra RL, Rockett KA, Fernando SD, Carter R, Kwiatkowski DP, Karunaweera ND. G6PD gene variants and its association with malaria in a Sri Lankan population. Malar J 2015; 14:93. [PMID: 25885177 PMCID: PMC4343272 DOI: 10.1186/s12936-015-0603-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Accepted: 02/02/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Glucose-6-phosphate dehydrogenase (G6PD) is an enzyme that plays an important role in many cellular functions. Deficiency of this enzyme results from point mutations in the coding region of the G6PD gene. G6PD-deficiency is important in malaria, as certain anti-malarial drugs could induce haemolysis in such patients and mutations in this gene may influence the susceptibility or resistance to the disease. Detailed information on genetic variations in the G6PD gene for Sri Lankan populations is yet to be revealed. This study describes a set of G6PD mutations present in a Sri Lankan population and their association with uncomplicated malaria. METHODS DNA was extracted from 1,051 individuals. Sixty-eight SNPs in the region of the G6PD gene were genotyped. A database created during the 1992-1993 malaria epidemic for the same individuals was used to assess the associations between the G6PD SNPs and parasite density or disease severity of uncomplicated malaria infections. Linkage disequilibrium for SNPs and haplotype structures were identified. RESULTS Seventeen genetic variants were polymorphic in this population. The mutant allele was the major allele in 9 SNPs. Common G6PD variants already described in Asians or South-Asians seemed to be absent or rare in this population. Both the severity of disease in uncomplicated malaria infections and parasitaemia were significantly lower in males infected with Plasmodium falciparum carrying the ancestral allele of rs915942 compared to those carrying the mutant allele. The parasite density of males infected with P. falciparum was significantly lower also in those who possessed the mutant alleles of rs5986877, rs7879049 and rs7053878. Two haplotype blocks were identified, where the recombination rates were higher in males with no history of malaria when compared to those who have experienced the disease in the past. CONCLUSIONS This is the most detailed survey of G6PD SNPs in a Sri Lankan population undertaken so far that enabled novel description of single nucleotide polymorphisms within the G6PD gene. A few of these genetic variations identified, demonstrated a tendency to be associated with either disease severity or parasite density in uncomplicated disease in males. Known G6PD gene polymorphisms already described from elsewhere were either absent or rare in the local study population.
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Affiliation(s)
- Rajika L Dewasurendra
- Department of Parasitology, Faculty of Medicine, University of Colombo, 25, Kynsey Road, Colombo 08, Sri Lanka.
| | - Kirk A Rockett
- TheWellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford, OX3, 7BN, UK.
| | - S Deepika Fernando
- Department of Parasitology, Faculty of Medicine, University of Colombo, 25, Kynsey Road, Colombo 08, Sri Lanka.
| | - Richard Carter
- Division of Biological Sciences, Ashworth Laboratories, University of Edinburgh, West Mains Rd, Edinburgh, EH9 3JT, UK.
| | - Dominic P Kwiatkowski
- TheWellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford, OX3, 7BN, UK. .,Wellcome Trust Sanger Institute, Cambridge, UK.
| | - Nadira D Karunaweera
- Department of Parasitology, Faculty of Medicine, University of Colombo, 25, Kynsey Road, Colombo 08, Sri Lanka.
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Amoako N, Asante KP, Adjei G, Awandare GA, Bimi L, Owusu-Agyei S. Associations between red cell polymorphisms and Plasmodium falciparum infection in the middle belt of Ghana. PLoS One 2014; 9:e112868. [PMID: 25470251 PMCID: PMC4254276 DOI: 10.1371/journal.pone.0112868] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Accepted: 10/20/2014] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND Red blood cell (RBC) polymorphisms are common in malaria endemic regions and are known to protect against severe forms of the disease. Therefore, it is important to screen for these polymorphisms in drugs or vaccines efficacy trials. This study was undertaken to evaluate associations between clinical malaria and RBC polymorphisms to assess biological interactions that may be necessary for consideration when designing clinical trials. METHOD In a cross-sectional study of 341 febrile children less than five years of age, associations between clinical malaria and common RBC polymorphisms including the sickle cell gene and G6PD deficiency was evaluated between November 2008 and June 2009 in the middle belt of Ghana, Kintampo. G6PD deficiency was determined by quantitative methods whiles haemoglobin variants were determined by haemoglobin titan gel electrophoresis. Blood smears were stained with Giemsa and parasite densities were determined microscopically. RESULTS The prevalence of clinical malarial among the enrolled children was 31.9%. The frequency of G6PD deficiency was 19.0% and that for the haemoglobin variants were 74.7%, 14.7%, 9.1%, 0.9% respectively for HbAA, HbAC, HbAS and HbSS. In Multivariate regression analysis, children with the HbAS genotype had 79% lower risk of malaria infection compared to those with the HbAA genotypes (OR = 0.21, 95% CI: 0.06-0.73, p = 0.01). HbAC genotype was not significantly associated with malaria infection relative to the HbAA genotype (OR = 0.70, 95% CI: 0.35-1.42, p = 0.33). G6PD deficient subgroup had a marginally increased risk of malaria infection compared to the G6PD normal subgroup (OR = 1.76, 95% CI: 0.98-3.16, p = 0.06). CONCLUSION These results confirm previous findings showing a protective effect of sickle cell trait on clinical malaria infection. However, G6PD deficiency was associated with a marginal increase in susceptibility to clinical malaria compared to children without G6PD deficiency.
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Affiliation(s)
- Nicholas Amoako
- Kintampo Health Research Centre, Kintampo, Brong Ahafo Region, Ghana
| | - Kwaku Poku Asante
- Kintampo Health Research Centre, Kintampo, Brong Ahafo Region, Ghana
| | - George Adjei
- Kintampo Health Research Centre, Kintampo, Brong Ahafo Region, Ghana
| | - Gordon A Awandare
- Infectious Diseases Research Laboratory, Department of Biochemistry, Cell and Molecular Biology. University of Ghana, Legon, Ghana
| | - Langbong Bimi
- Department of Animal Biology and Conservation Science, University of Ghana, Legon, Ghana
| | - Seth Owusu-Agyei
- Kintampo Health Research Centre, Kintampo, Brong Ahafo Region, Ghana
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11
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Hernandez-Valladares M, Rihet P, Iraqi FA. Host susceptibility to malaria in human and mice: compatible approaches to identify potential resistant genes. Physiol Genomics 2014; 46:1-16. [DOI: 10.1152/physiolgenomics.00044.2013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
There is growing evidence for human genetic factors controlling the outcome of malaria infection, while molecular basis of this genetic control is still poorly understood. Case-control and family-based studies have been carried out to identify genes underlying host susceptibility to malarial infection. Parasitemia and mild malaria have been genetically linked to human chromosomes 5q31-q33 and 6p21.3, and several immune genes located within those regions have been associated with malaria-related phenotypes. Association and linkage studies of resistance to malaria are not easy to carry out in human populations, because of the difficulty in surveying a significant number of families. Murine models have proven to be an excellent genetic tool for studying host response to malaria; their use allowed mapping 14 resistance loci, eight of them controlling parasitic levels and six controlling cerebral malaria. Once quantitative trait loci or genes have been identified, the human ortholog may then be identified. Comparative mapping studies showed that a couple of human and mouse might share similar genetically controlled mechanisms of resistance. In this way, char8, which controls parasitemia, was mapped on chromosome 11; char8 corresponds to human chromosome 5q31-q33 and contains immune genes, such as Il3, Il4, Il5, Il12b, Il13, Irf1, and Csf2. Nevertheless, part of the genetic factors controlling malaria traits might differ in both hosts because of specific host-pathogen interactions. Finally, novel genetic tools including animal models were recently developed and will offer new opportunities for identifying genetic factors underlying host phenotypic response to malaria, which will help in better therapeutic strategies including vaccine and drug development.
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Affiliation(s)
| | - Pascal Rihet
- UMR1090 TAGC, INSERM, Marseille, France
- Aix-Marseille University, Marseille, France; and
| | - Fuad A. Iraqi
- Department of Clinical Microbiology and Immunology, Sackler Faculty of Medicine, Tel Aviv University, Ramat Aviv, Tel Aviv, Israel
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12
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Dewasurendra RL, Suriyaphol P, Fernando SD, Carter R, Rockett K, Corran P, Kwiatkowski D, Karunaweera ND. Genetic polymorphisms associated with anti-malarial antibody levels in a low and unstable malaria transmission area in southern Sri Lanka. Malar J 2012; 11:281. [PMID: 22905743 PMCID: PMC3459805 DOI: 10.1186/1475-2875-11-281] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 07/21/2012] [Indexed: 01/08/2023] Open
Abstract
Background The incidence of malaria in Sri Lanka has significantly declined in recent years. Similar trends were seen in Kataragama, a known malaria endemic location within the southern province of the country, over the past five years. This is a descriptive study of anti-malarial antibody levels and selected host genetic mutations in residents of Kataragama, under low malaria transmission conditions. Methods Sera were collected from 1,011 individuals residing in Kataragama and anti-malarial antibodies and total IgE levels were measured by a standardized ELISA technique. Host DNA was extracted and used for genotyping of selected SNPs in known genes associated with malaria. The antibody levels were analysed in relation to the past history of malaria (during past 10 years), age, sex, the location of residence within Kataragama and selected host genetic markers. Results A significant increase in antibodies against Plasmodium falciparum antigens AMA1, MSP2, NANP and Plasmodium vivax antigen MSP1 in individuals with past history of malaria were observed when compared to those who did not. A marked increase of anti-MSP1(Pf) and anti-AMA1(Pv) was also evident in individuals between 45–59 years (when compared to other age groups). Allele frequencies for two SNPs in genes that code for IL-13 and TRIM-5 were found to be significantly different between those who have experienced one or more malaria attacks within past 10 years and those who did not. When antibody levels were classified into a low-high binary trait, significant associations were found with four SNPs for anti-AMA1(Pf); two SNPs for anti-MSP1(Pf); eight SNPs for anti-NANP(Pf); three SNPs for anti-AMA1(Pv); seven SNPs for anti-MSP1(Pv); and nine SNPs for total IgE. Eleven of these SNPs with significant associations with anti-malarial antibody levels were found to be non–synonymous. Conclusions Evidence is suggestive of an age–acquired immunity in this study population in spite of low malaria transmission levels. Several SNPs were in linkage disequilibrium and had a significant association with elevated antibody levels, suggesting that these host genetic mutations might have an individual or collective effect on inducing or/and maintaining high anti–malarial antibody levels.
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Affiliation(s)
- Rajika L Dewasurendra
- Department of Parasitology, Faculty of Medicine, University of Colombo, Colombo, Sri Lanka
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13
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Laishram DD, Sutton PL, Nanda N, Sharma VL, Sobti RC, Carlton JM, Joshi H. The complexities of malaria disease manifestations with a focus on asymptomatic malaria. Malar J 2012; 11:29. [PMID: 22289302 PMCID: PMC3342920 DOI: 10.1186/1475-2875-11-29] [Citation(s) in RCA: 186] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Accepted: 01/31/2012] [Indexed: 12/02/2022] Open
Abstract
Malaria is a serious parasitic disease in the developing world, causing high morbidity and mortality. The pathogenesis of malaria is complex, and the clinical presentation of disease ranges from severe and complicated, to mild and uncomplicated, to asymptomatic malaria. Despite a wealth of studies on the clinical severity of disease, asymptomatic malaria infections are still poorly understood. Asymptomatic malaria remains a challenge for malaria control programs as it significantly influences transmission dynamics. A thorough understanding of the interaction between hosts and parasites in the development of different clinical outcomes is required. In this review, the problems and obstacles to the study and control of asymptomatic malaria are discussed. The human and parasite factors associated with differential clinical outcomes are described and the management and treatment strategies for the control of the disease are outlined. Further, the crucial gaps in the knowledge of asymptomatic malaria that should be the focus of future research towards development of more effective malaria control strategies are highlighted.
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Affiliation(s)
- Dolie D Laishram
- Department of Biology, New York University, New York, NY 10003, USA
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14
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Mideo N, Savill NJ, Chadwick W, Schneider P, Read AF, Day T, Reece SE. Causes of variation in malaria infection dynamics: insights from theory and data. Am Nat 2011; 178:E174-E188. [PMID: 22089879 PMCID: PMC3937740 DOI: 10.1086/662670] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Parasite strategies for exploiting host resources are key determinants of disease severity (i.e., virulence) and infectiousness (i.e., transmission between hosts). By iterating the development of theory and empirical tests, we investigated whether variation in parasite traits across two genetically distinct clones of the rodent malaria parasite, Plasmodium chabaudi, explains differences in within-host infection dynamics and virulence. First, we experimentally tested key predictions of our earlier modeling work. As predicted, the more virulent genotype produced more progeny parasites per infected cell (burst size), but in contrast to predictions, invasion rates of red blood cells (RBCs) did not differ between the genotypes studied. Second, we further developed theory by confronting our earlier model with these new data, testing a new set of models that incorporate more biological realism, and developing novel theoretical tools for identifying differences between parasite genotypes. Overall, we found robust evidence that differences in burst sizes contribute to variation in dynamics and that differential interactions between parasites and host immune responses also play a role. In contrast to previous work, our model predicts that RBC age structure is not important for explaining dynamics. Integrating theory and empirical tests is a potentially powerful way of progressing understanding of disease biology.
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Affiliation(s)
- Nicole Mideo
- Centre for Immunity, Infection and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom
| | - Nicholas J. Savill
- Centre for Immunity, Infection and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom
- Institute of Immunity and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom
| | - William Chadwick
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom
| | - Petra Schneider
- Centre for Immunity, Infection and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom
| | - Andrew F. Read
- Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, University Park, Pennsylvania 16802; and Fogarty International Center, National Institutes of Health, Bethesda, Maryland 20892
| | - Troy Day
- Departments of Biology and Mathematics and Statistics, Queen’s University, Kingston, Ontario K7L 3N6, Canada
| | - Sarah E. Reece
- Centre for Immunity, Infection and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom
- Institute of Immunity and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, United Kingdom
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15
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Meyer CG, Calixto Fernandes MH, Intemann CD, Kreuels B, Kobbe R, Kreuzberg C, Ayim M, Ruether A, Loag W, Ehmen C, Adjei S, Adjei O, Horstmann RD, May J. IL3 variant on chromosomal region 5q31–33 and protection from recurrent malaria attacks. Hum Mol Genet 2011; 20:1173-81. [DOI: 10.1093/hmg/ddq562] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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16
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Pullan RL, Bukirwa H, Snow RW, Brooker S. Heritability of Plasmodium parasite density in a rural Ugandan community. Am J Trop Med Hyg 2010; 83:990-5. [PMID: 21036825 PMCID: PMC2963957 DOI: 10.4269/ajtmh.2010.10-0049] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Many factors influence variation in Plasmodium infection levels, including parasite/host genetics, immunity, and exposure. Here, we examine the roles of host genetics and exposure in determining parasite density, and test whether effects differ with age. Data for 1,711 residents of an eastern Ugandan community were used in pedigree-based variance component analysis. Heritability of parasite density was 13% (P < 0.001) but was not significant after controlling for shared household. Allowing variance components to vary between children (< 16 years) and adults (≥ 16 years) revealed striking age differences; 26% of variation could be explained by additively acting genes in children (P < 0.001), but there was no genetic involvement in adults. Domestic environment did not explain variation in children and explained 5% in adults (P = 0.09). Genetic effects are an important determinant of parasite density in children in this population, consistent with previous quantitative genetic studies of Plasmodium parasitaemia, although differences in environmental exposure play a lesser role.
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Affiliation(s)
- Rachel L Pullan
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom.
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17
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Bejon P, Williams TN, Liljander A, Noor AM, Wambua J, Ogada E, Olotu A, Osier FHA, Hay SI, Färnert A, Marsh K. Stable and unstable malaria hotspots in longitudinal cohort studies in Kenya. PLoS Med 2010; 7:e1000304. [PMID: 20625549 PMCID: PMC2897769 DOI: 10.1371/journal.pmed.1000304] [Citation(s) in RCA: 197] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2010] [Accepted: 05/27/2010] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND Infectious diseases often demonstrate heterogeneity of transmission among host populations. This heterogeneity reduces the efficacy of control strategies, but also implies that focusing control strategies on "hotspots" of transmission could be highly effective. METHODS AND FINDINGS In order to identify hotspots of malaria transmission, we analysed longitudinal data on febrile malaria episodes, asymptomatic parasitaemia, and antibody titres over 12 y from 256 homesteads in three study areas in Kilifi District on the Kenyan coast. We examined heterogeneity by homestead, and identified groups of homesteads that formed hotspots using a spatial scan statistic. Two types of statistically significant hotspots were detected; stable hotspots of asymptomatic parasitaemia and unstable hotspots of febrile malaria. The stable hotspots were associated with higher average AMA-1 antibody titres than the unstable clusters (optical density [OD] = 1.24, 95% confidence interval [CI] 1.02-1.47 versus OD = 1.1, 95% CI 0.88-1.33) and lower mean ages of febrile malaria episodes (5.8 y, 95% CI 5.6-6.0 versus 5.91 y, 95% CI 5.7-6.1). A falling gradient of febrile malaria incidence was identified in the penumbrae of both hotspots. Hotspots were associated with AMA-1 titres, but not seroconversion rates. In order to target control measures, homesteads at risk of febrile malaria could be predicted by identifying the 20% of homesteads that experienced an episode of febrile malaria during one month in the dry season. That 20% subsequently experienced 65% of all febrile malaria episodes during the following year. A definition based on remote sensing data was 81% sensitive and 63% specific for the stable hotspots of asymptomatic malaria. CONCLUSIONS Hotspots of asymptomatic parasitaemia are stable over time, but hotspots of febrile malaria are unstable. This finding may be because immunity offsets the high rate of febrile malaria that might otherwise result in stable hotspots, whereas unstable hotspots necessarily affect a population with less prior exposure to malaria.
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Affiliation(s)
- Philip Bejon
- Kilifi KEMRI-Wellcome Trust Collaborative Research Programme, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya.
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18
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Lawaly YR, Sakuntabhai A, Marrama L, Konate L, Phimpraphi W, Sokhna C, Tall A, Diène Sarr F, Peerapittayamongkol C, Louicharoen C, Schneider BS, Levescot A, Talman A, Casademont I, Menard D, Trape JF, Rogier C, Kaewkunwal J, Sura T, Nuchprayoon I, Ariey F, Baril L, Singhasivanon P, Mercereau-Puijalon O, Paul R. Heritability of the human infectious reservoir of malaria parasites. PLoS One 2010; 5:e11358. [PMID: 20613877 PMCID: PMC2894056 DOI: 10.1371/journal.pone.0011358] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2009] [Accepted: 05/28/2010] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Studies on human genetic factors associated with malaria have hitherto concentrated on their role in susceptibility to and protection from disease. In contrast, virtually no attention has been paid to the role of human genetics in eliciting the production of parasite transmission stages, the gametocytes, and thus enhancing the spread of disease. METHODS AND FINDINGS We analysed four longitudinal family-based cohort studies from Senegal and Thailand followed for 2-8 years and evaluated the relative impact of the human genetic and non-genetic factors on gametocyte production in infections of Plasmodium falciparum or P. vivax. Prevalence and density of gametocyte carriage were evaluated in asymptomatic and symptomatic infections by examination of Giemsa-stained blood smears and/or RT-PCR (for falciparum in one site). A significant human genetic contribution was found to be associated with gametocyte prevalence in asymptomatic P. falciparum infections. By contrast, there was no heritability associated with the production of gametocytes for P. falciparum or P. vivax symptomatic infections. Sickle cell mutation, HbS, was associated with increased gametocyte prevalence but its contribution was small. CONCLUSIONS The existence of a significant human genetic contribution to gametocyte prevalence in asymptomatic infections suggests that candidate gene and genome wide association approaches may be usefully applied to explore the underlying human genetics. Prospective epidemiological studies will provide an opportunity to generate novel and perhaps more epidemiologically pertinent gametocyte data with which similar analyses can be performed and the role of human genetics in parasite transmission ascertained.
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Affiliation(s)
| | - Anavaj Sakuntabhai
- Institut Pasteur, Laboratoire de la Génétique de la réponse aux infections chez l'homme, Paris, France
- Institut Pasteur, Unité de Pathogénie Virale, Paris, France
| | - Laurence Marrama
- Institut Pasteur de Dakar, Unité d'Epidémiologie, Dakar, Senegal
| | - Lassana Konate
- Faculté des Sciences et Techniques, UCAD, Dakar, Senegal
| | - Waraphon Phimpraphi
- Institut Pasteur, Laboratoire de la Génétique de la réponse aux infections chez l'homme, Paris, France
- Department of Tropical Hygiene, Faculty of Tropical Medicine, Mahidol University, Bangkok Thailand
| | - Cheikh Sokhna
- Institut de Recherche pour le Développement, Laboratoire de Paludologie, Dakar, Senegal
| | - Adama Tall
- Institut Pasteur de Dakar, Unité d'Epidémiologie, Dakar, Senegal
| | | | | | - Chalisa Louicharoen
- Institut Pasteur, Laboratoire de la Génétique de la réponse aux infections chez l'homme, Paris, France
- Inter-Department Program of Biomedical Science, Faculty of Graduate School, Chulalongkorn University, Bangkok, Thailand
| | | | - Anaïs Levescot
- Institut Pasteur, Laboratoire de la Génétique de la réponse aux infections chez l'homme, Paris, France
| | - Arthur Talman
- Unité d'Epidémiologie Moléculaire, Institut Pasteur, Phnom Penh, Cambodia
| | - Isabelle Casademont
- Institut Pasteur, Laboratoire de la Génétique de la réponse aux infections chez l'homme, Paris, France
- Institut Pasteur, Unité de Pathogénie Virale, Paris, France
| | - Didier Menard
- Unité d'Epidémiologie Moléculaire, Institut Pasteur, Phnom Penh, Cambodia
| | - Jean-François Trape
- Institut de Recherche pour le Développement, Laboratoire de Paludologie, Dakar, Senegal
| | - Christophe Rogier
- Institut de Médecine Tropicale du Service de Santé des Armées, Unité de Recherche en Biologie et épidémiologie parasitaires, IFR48, Le Pharo, Marseille, France
| | - Jaranit Kaewkunwal
- Department of Tropical Hygiene, Faculty of Tropical Medicine, Mahidol University, Bangkok Thailand
| | - Thanyachai Sura
- Department of Medicine, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok, Thailand
| | - Issarang Nuchprayoon
- Department of Pediatrics, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Frederic Ariey
- Unité d'Epidémiologie Moléculaire, Institut Pasteur, Phnom Penh, Cambodia
| | - Laurence Baril
- Institut Pasteur de Dakar, Unité d'Epidémiologie, Dakar, Senegal
| | - Pratap Singhasivanon
- Department of Tropical Hygiene, Faculty of Tropical Medicine, Mahidol University, Bangkok Thailand
| | | | - Rick Paul
- Institut Pasteur de Dakar, Laboratoire d'Entomologie Médicale, Dakar, Senegal
- Institut Pasteur, Laboratoire de la Génétique de la réponse aux infections chez l'homme, Paris, France
- Institut Pasteur, Unité de Pathogénie Virale, Paris, France
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Interaction of malaria with a common form of severe thalassemia in an Asian population. Proc Natl Acad Sci U S A 2009; 106:18716-21. [PMID: 19841268 DOI: 10.1073/pnas.0910142106] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In many Asian populations, the commonest form of severe thalassemia results from the coinheritance of HbE and beta thalassemia. The management of this disease is particularly difficult because of its extreme clinical diversity; although some genetic and adaptive factors have been identified as phenotypic modifiers, the reasons remain unclear. Because the role of the environment in the course of severe thalassemia has been neglected completely and because malaria due to both Plasmodium falciparum and Plasmodium vivax has been prevalent in Sri Lanka, we carried out a pilot study of patients with HbE beta thalassemia that showed high frequencies of antibodies to both parasite species and that 28.6% of the children had DNA-based evidence of current infection with P. vivax. Malarial antibodies then were assessed in patients with HbE beta thalassemia compared with those in age-matched controls. There was a significant increase in the frequency of antibodies in the thalassemic patients, particularly against P. vivax and in young children. There was also a higher frequency in those who had been splenectomized compared with those with intact spleens, although in the latter it was still higher than that in the controls. The thalassemic patients showed significant correlations between malaria antibody status and phenotype. Patients with HbE beta thalassemia may be more prone to malaria, particularly P. vivax, which is reflected in their clinical severity. Because P. vivax malaria is widespread in Asia, further studies of its interaction with HbE beta thalassemia and related diseases are required urgently as a part of ongoing thalassemia control programs.
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20
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Faik I, de Carvalho EG, Kun JF. Parasite-host interaction in malaria: genetic clues and copy number variation. Genome Med 2009; 1:82. [PMID: 19725943 PMCID: PMC2768989 DOI: 10.1186/gm82] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
In humans, infections contribute highly to mortality and morbidity rates worldwide. Malaria tropica is one of the major infectious diseases globally and is caused by the protozoan parasite Plasmodium falciparum. Plasmodia have accompanied human beings since the emergence of humankind. Due to its pathogenicity, malaria is a powerful selective force on the human genome. Genetic epidemiology approaches such as family and twin studies, candidate gene studies, and disease-association studies have identified a number of genes that mediate relative protection against the severest forms of the disease. New molecular approaches, including genome-wide association studies, have recently been performed to expand our knowledge on the functional effect of human variation in malaria. For the future, a systematic determination of gene-dosage effects and expression profiles of protective genes might unveil the functional impact of structural alterations in these genes on either side of the host-parasite interaction.
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Affiliation(s)
- Imad Faik
- Institute for Tropical Medicine, University Tübingen, Wilhelmstr, 27, 72074 Tübingen, Germany
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21
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Verra F, Mangano VD, Modiano D. Genetics of susceptibility to Plasmodium falciparum: from classical malaria resistance genes towards genome-wide association studies. Parasite Immunol 2009; 31:234-53. [PMID: 19388945 DOI: 10.1111/j.1365-3024.2009.01106.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Plasmodium falciparum represents one of the strongest selective forces on the human genome. This stable and perennial pressure has contributed to the progressive accumulation in the exposed populations of genetic adaptations to malaria. Descriptive genetic epidemiology provides the initial step of a logical procedure of consequential phases spanning from the identification of genes involved in the resistance/susceptibility to diseases, to the determination of the underlying mechanisms and finally to the possible translation of the acquired knowledge in new control tools. In malaria, the rational development of this strategy is traditionally based on complementary interactions of heterogeneous disciplines going from epidemiology to vaccinology passing through genetics, pathogenesis and immunology. New tools including expression profile analysis and genome-wide association studies are recently available to explore the complex interactions of host-parasite co-evolution. Particularly, the combination of genome-wide association studies with large multi-centre initiatives can overcome the limits of previous results due to local population dynamics. Thus, we anticipate substantial advances in the interpretation and validation of the effects of genetic variation on malaria susceptibility, and thereby on molecular mechanisms of protective immune responses and pathogenesis.
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Affiliation(s)
- F Verra
- Department of Public Health, University of Rome La Sapienza, Rome, Italy.
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22
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Phimpraphi W, Paul R, Witoonpanich B, Turbpaiboon C, Peerapittayamongkol C, Louicharoen C, Casademont I, Tungpradabkul S, Krudsood S, Kaewkunwal J, Sura T, Looareesuwan S, Singhasivanon P, Sakuntabhai A. Heritability of P. falciparum and P. vivax malaria in a Karen population in Thailand. PLoS One 2008; 3:e3887. [PMID: 19060954 PMCID: PMC2588340 DOI: 10.1371/journal.pone.0003887] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2008] [Accepted: 11/12/2008] [Indexed: 11/18/2022] Open
Abstract
The majority of studies concerning malaria host genetics have focused on individual genes that confer protection against rather than susceptibility to malaria. Establishing the relative impact of genetic versus non-genetic factors on malaria infection and disease is essential to focus effort on key determinant factors. This relative contribution has rarely been evaluated for Plasmodium falciparum and almost never for Plasmodium vivax. We conducted a longitudinal cohort study in a Karen population of 3,484 individuals in a region of mesoendemic malaria, Thailand from 1998 to 2005. The number of P. falciparum and P. vivax clinical cases and the parasite density per person were determined. Statistical analyses were performed to account for the influence of environmental factors and the genetic heritability of the phenotypes was calculated using the pedigree-based variance components model. The genetic contribution to the number of clinical episodes resulting from P. falciparum and P. vivax were 10% and 19% respectively. There was also moderate genetic contribution to the maximum and overall parasite trophozoite density phenotypes for both P. falciparum (16%&16%) and P. vivax (15%&13%). These values, for P. falciparum, were similar to those previously observed in a region of much higher transmission intensity in Senegal, West Africa. Although environmental factors play an important role in acquiring an infection, genetics plays a determinant role in the outcome of an infection with either malaria parasite species prior to the development of immunity.
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Affiliation(s)
- Waraphon Phimpraphi
- Institut Pasteur, Laboratoire de la Génétique de la réponse aux infections chez l'homme, Paris, France
- Department of Tropical Hygiene, Faculty of Tropical Medicine, Mahidol University, Bangkok Thailand
| | - Richard Paul
- Institut Pasteur, Laboratoire de la Génétique de la réponse aux infections chez l'homme, Paris, France
| | - Bhee Witoonpanich
- Institut Pasteur, Laboratoire de la Génétique de la réponse aux infections chez l'homme, Paris, France
- Department of Biochemistry, Faculty of Science, Mahidol University, Bangkok, Thailand
| | - Chairat Turbpaiboon
- Institut Pasteur, Laboratoire de la Génétique de la réponse aux infections chez l'homme, Paris, France
- Department of Biochemistry, Faculty of Science, Mahidol University, Bangkok, Thailand
| | | | - Chalisa Louicharoen
- Institut Pasteur, Laboratoire de la Génétique de la réponse aux infections chez l'homme, Paris, France
| | - Isabelle Casademont
- Institut Pasteur, Laboratoire de la Génétique de la réponse aux infections chez l'homme, Paris, France
| | - Sumalee Tungpradabkul
- Department of Biochemistry, Faculty of Science, Mahidol University, Bangkok, Thailand
| | - Srivicha Krudsood
- Department of Tropical Hygiene, Faculty of Tropical Medicine, Mahidol University, Bangkok Thailand
| | - Jaranit Kaewkunwal
- Department of Tropical Hygiene, Faculty of Tropical Medicine, Mahidol University, Bangkok Thailand
| | - Thanyachai Sura
- Department of Medicine, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok, Thailand
| | - Sornchai Looareesuwan
- Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Pratap Singhasivanon
- Department of Tropical Hygiene, Faculty of Tropical Medicine, Mahidol University, Bangkok Thailand
| | - Anavaj Sakuntabhai
- Institut Pasteur, Laboratoire de la Génétique de la réponse aux infections chez l'homme, Paris, France
- Department of Medicine, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok, Thailand
- * E-mail:
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Ishak HD, Dumbacher JP, Anderson NL, Keane JJ, Valkiūnas G, Haig SM, Tell LA, Sehgal RNM. Blood parasites in owls with conservation implications for the Spotted Owl (Strix occidentalis). PLoS One 2008; 3:e2304. [PMID: 18509541 PMCID: PMC2387065 DOI: 10.1371/journal.pone.0002304] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2008] [Accepted: 04/20/2008] [Indexed: 11/19/2022] Open
Abstract
The three subspecies of Spotted Owl (Northern, Strix occidentalis caurina; California, S. o. occidentalis; and Mexican, S. o. lucida) are all threatened by habitat loss and range expansion of the Barred Owl (S. varia). An unaddressed threat is whether Barred Owls could be a source of novel strains of disease such as avian malaria (Plasmodium spp.) or other blood parasites potentially harmful for Spotted Owls. Although Barred Owls commonly harbor Plasmodium infections, these parasites have not been documented in the Spotted Owl. We screened 111 Spotted Owls, 44 Barred Owls, and 387 owls of nine other species for haemosporidian parasites (Leucocytozoon, Plasmodium, and Haemoproteus spp.). California Spotted Owls had the greatest number of simultaneous multi-species infections (44%). Additionally, sequencing results revealed that the Northern and California Spotted Owl subspecies together had the highest number of Leucocytozoon parasite lineages (n = 17) and unique lineages (n = 12). This high level of sequence diversity is significant because only one Leucocytozoon species (L. danilewskyi) has been accepted as valid among all owls, suggesting that L. danilewskyi is a cryptic species. Furthermore, a Plasmodium parasite was documented in a Northern Spotted Owl for the first time. West Coast Barred Owls had a lower prevalence of infection (15%) when compared to sympatric Spotted Owls (S. o. caurina 52%, S. o. occidentalis 79%) and Barred Owls from the historic range (61%). Consequently, Barred Owls on the West Coast may have a competitive advantage over the potentially immune compromised Spotted Owls.
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Affiliation(s)
- Heather D Ishak
- Department of Biology, San Francisco State University, San Francisco, California, United States of America.
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24
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Sumathipala A, Siribaddana S, Hewege S, Lekamwattage M, Athukorale M, Siriwardhana C, Murray J, Prince M. Ethics Review Committee approval and informed consent: an analysis of biomedical publications originating from Sri Lanka. BMC Med Ethics 2008; 9:3. [PMID: 18267015 PMCID: PMC2270278 DOI: 10.1186/1472-6939-9-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2007] [Accepted: 02/11/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND International guidelines on research have focused on protecting research participants. Ethical Research Committee (ERC) approval and informed consent are the cornerstones. Externally sponsored research requires approval through ethical review in both the host and the sponsoring country. This study aimed to determine to what extent ERC approval and informed consent procedures are documented in locally and internationally published human subject research carried out in Sri Lanka. METHODS We obtained ERC approval in Sri Lanka and the United Kingdom. Theses from 1985 to 2005 available at the Postgraduate Institute of Medicine (PGIM) library affiliated to the University of Colombo were scrutinised using checklists agreed in consultation with senior research collaborators. A Medline search was carried out with MeSH major and minor heading 'Sri Lanka' as the search term for international publications originating in Sri Lanka during 1999 to 2004. All research publications from CMJ during 1999 to 2005 were also scrutinized. RESULTS Of 291 theses, 34% documented ERC approvals and 61% documented obtaining consent. From the international journal survey, 250 publications originated from Sri Lanka of which only 79 full text original research publications could be accessed electronically. Of these 38% documented ERC approval and 39% documented obtaining consent. In the Ceylon Medical Journal 36% documented ERC approval and 37% documented obtaining consent. CONCLUSION Only one third of the publications scrutinized recorded ERC approval and procurement of informed consent. However, there is a positive trend in documenting these ethical requirements in local postgraduate research and in the local medical journal.
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Affiliation(s)
- Athula Sumathipala
- Kings College; Institute of Psychiatry, Health Services and Population Research Department, De Crespigny Park, London SE5 8AF, UK
- Institutes of Research and Development, 762/4B Pannipitiya Rd, Battaramulla 10120, Sri Lanka
| | - Sisira Siribaddana
- Institutes of Research and Development, 762/4B Pannipitiya Rd, Battaramulla 10120, Sri Lanka
| | - Suwin Hewege
- Institutes of Research and Development, 762/4B Pannipitiya Rd, Battaramulla 10120, Sri Lanka
| | - Manura Lekamwattage
- Institutes of Research and Development, 762/4B Pannipitiya Rd, Battaramulla 10120, Sri Lanka
| | - Manjula Athukorale
- Institutes of Research and Development, 762/4B Pannipitiya Rd, Battaramulla 10120, Sri Lanka
| | - Chesmal Siriwardhana
- Institutes of Research and Development, 762/4B Pannipitiya Rd, Battaramulla 10120, Sri Lanka
| | - Joanna Murray
- Kings College; Institute of Psychiatry, Health Services and Population Research Department, De Crespigny Park, London SE5 8AF, UK
| | - Martin Prince
- Kings College; Institute of Psychiatry, Health Services and Population Research Department, De Crespigny Park, London SE5 8AF, UK
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25
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Wedekind C, Walker M, Little TJ. The separate and combined effects of MHC genotype, parasite clone, and host gender on the course of malaria in mice. BMC Genet 2006; 7:55. [PMID: 17118203 PMCID: PMC1664581 DOI: 10.1186/1471-2156-7-55] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2006] [Accepted: 11/21/2006] [Indexed: 11/25/2022] Open
Abstract
Background The link between host MHC (major histocompatibility complex) genotype and malaria is largely based on correlative data with little or no experimental control of potential confounding factors. We used an experimental mouse model to test for main effects of MHC-haplotypes, MHC heterozygosity, and MHC × parasite clone interactions. We experimentally infected MHC-congenic mice (F2 segregants, homo- and heterozygotes, males and females) with one of two clones of Plasmodium chabaudi and recorded disease progression. Results We found that MHC haplotype and parasite clone each have a significant influence on the course of the disease, but there was no significant host genotype by parasite genotype interaction. We found no evidence for overdominance nor any other sort of heterozygote advantage or disadvantage. Conclusion When tested under experimental conditions, variation in the MHC can significantly influence the course of malaria. However, MHC heterozygote advantage through overdominance or dominance of resistance cannot be assumed in the case of single-strain infections. Future studies might focus on the interaction between MHC heterozygosity and multiple-clone infections.
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Affiliation(s)
- Claus Wedekind
- Department of Ecology and Evolution, University of Lausanne, Biophore, 1015 Lausanne, Switzerland
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, Scotland, UK
| | - Mirjam Walker
- Institute of Zoo and Wildlife Biology, 10252 Berlin, Germany
- Natural History Museum Bern, 3005 Bern, Switzerland
- ZLB Behring AG, Wankdorfstr. 10, 3022 Bern, Switzerland
| | - Tom J Little
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, Scotland, UK
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Mockenhaupt FP, Cramer JP, Hamann L, Stegemann MS, Eckert J, Oh NR, Otchwemah RN, Dietz E, Ehrhardt S, Schröder NWJ, Bienzle U, Schumann RR. Toll-like receptor (TLR) polymorphisms in African children: Common TLR-4 variants predispose to severe malaria. Proc Natl Acad Sci U S A 2005; 103:177-82. [PMID: 16371473 PMCID: PMC1324982 DOI: 10.1073/pnas.0506803102] [Citation(s) in RCA: 205] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Genetic host factors play a substantial role in susceptibility to and severity of malaria, which continues to cause at least one million deaths per year. Recently, members of the toll-like receptor (TLR) family have been shown to be involved in recognition of the etiologic organism Plasmodium falciparum: The glycosylphosphatidylinositol anchor induces signaling in host cells via TLR-2 and -4, whereas hemozoin-induced immune activation involves TLR-9. Binding of microbial ligands to the respective TLRs triggers the release of proinflammatory cytokines via the TLR/IL-1 receptor (TIR) domain and may contribute to the host response in malaria, including cytokine induction and fever. In a case-control study among 870 Ghanaian children, we examined the influence of TLR-2, -4, and -9 polymorphisms in susceptibility to severe malaria. TLR-2 variants common in Caucasians and Asians were completely absent. However, we found a rare previously undescribed mutation (Leu658Pro), which impairs signaling via TLR-2. We failed to detect any polymorphisms within the TLR-9 Toll/IL-1 receptor domain. Two frequent TLR-9 promoter polymorphisms did not show a clear association with malaria severity. In contrast, the TLR-4-Asp299Gly variant occurred at a high rate of 17.6% in healthy controls and was even more frequent in severe malaria patients (24.1%, P < 0.05). Likewise, TLR-4-Thr399Ile was seen in 2.4% of healthy children and in 6.2% of patients (P = 0.02). TLR-4-Asp299Gly and TLR-4-Thr399Ile conferred 1.5- and 2.6-fold increased risks of severe malaria, respectively. These findings suggest TLR4-mediated responses to malaria in vivo and TLR-4 polymorphisms to be associated with disease manifestation.
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Affiliation(s)
- Frank P Mockenhaupt
- Institute of Tropical Medicine Berlin, Charité-Universitätsmedizin Berlin, Spandauer Damm 130, 14050 Berlin, Germany
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27
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Abstract
BACKGROUND While many individual genes have been identified that confer protection against malaria, the overall impact of host genetics on malarial risk remains unknown. METHODS AND FINDINGS We have used pedigree-based genetic variance component analysis to determine the relative contributions of genetic and other factors to the variability in incidence of malaria and other infectious diseases in two cohorts of children living on the coast of Kenya. In the first, we monitored the incidence of mild clinical malaria and other febrile diseases through active surveillance of 640 children 10 y old or younger, living in 77 different households for an average of 2.7 y. In the second, we recorded hospital admissions with malaria and other infectious diseases in a birth cohort of 2,914 children for an average of 4.1 y. Mean annual incidence rates for mild and hospital-admitted malaria were 1.6 and 0.054 episodes per person per year, respectively. Twenty-four percent and 25% of the total variation in these outcomes was explained by additively acting host genes, and household explained a further 29% and 14%, respectively. The haemoglobin S gene explained only 2% of the total variation. For nonmalarial infections, additive genetics explained 39% and 13% of the variability in fevers and hospital-admitted infections, while household explained a further 9% and 30%, respectively. CONCLUSION Genetic and unidentified household factors each accounted for around one quarter of the total variability in malaria incidence in our study population. The genetic effect was well beyond that explained by the anticipated effects of the haemoglobinopathies alone, suggesting the existence of many protective genes, each individually resulting in small population effects. While studying these genes may well provide insights into pathogenesis and resistance in human malaria, identifying and tackling the household effects must be the more efficient route to reducing the burden of disease in malaria-endemic areas.
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Affiliation(s)
- Margaret J Mackinnon
- School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom.
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28
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Kwiatkowski DP. How malaria has affected the human genome and what human genetics can teach us about malaria. Am J Hum Genet 2005; 77:171-92. [PMID: 16001361 PMCID: PMC1224522 DOI: 10.1086/432519] [Citation(s) in RCA: 660] [Impact Index Per Article: 34.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2005] [Accepted: 06/03/2005] [Indexed: 12/22/2022] Open
Abstract
Malaria is a major killer of children worldwide and the strongest known force for evolutionary selection in the recent history of the human genome. The past decade has seen growing evidence of ethnic differences in susceptibility to malaria and of the diverse genetic adaptations to malaria that have arisen in different populations: epidemiological confirmation of the hypotheses that G6PD deficiency, alpha+ thalassemia, and hemoglobin C protect against malaria mortality; the application of novel haplotype-based techniques demonstrating that malaria-protective genes have been subject to recent positive selection; the first genetic linkage maps of resistance to malaria in experimental murine models; and a growing number of reported associations with resistance and susceptibility to human malaria, particularly in genes involved in immunity, inflammation, and cell adhesion. The challenge for the next decade is to build the global epidemiological infrastructure required for statistically robust genomewide association analysis, as a way of discovering novel mechanisms of protective immunity that can be used in the development of an effective malaria vaccine.
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Affiliation(s)
- Dominic P Kwiatkowski
- Wellcome Trust Centre for Human Genetics and University Department of Paediatrics, Oxford, United Kingdom.
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29
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Mackinnon MJ, Read AF. Virulence in malaria: an evolutionary viewpoint. Philos Trans R Soc Lond B Biol Sci 2004; 359:965-86. [PMID: 15306410 PMCID: PMC1693375 DOI: 10.1098/rstb.2003.1414] [Citation(s) in RCA: 171] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Malaria parasites cause much morbidity and mortality to their human hosts. From our evolutionary perspective, this is because virulence is positively associated with parasite transmission rate. Natural selection therefore drives virulence upwards, but only to the point where the cost to transmission caused by host death begins to outweigh the transmission benefits. In this review, we summarize data from the laboratory rodent malaria model, Plasmodium chabaudi, and field data on the human malaria parasite, P. falciparum, in relation to this virulence trade-off hypothesis. The data from both species show strong positive correlations between asexual multiplication, transmission rate, infection length, morbidity and mortality, and therefore support the underlying assumptions of the hypothesis. Moreover, the P. falciparum data show that expected total lifetime transmission of the parasite is maximized in young children in whom the fitness cost of host mortality balances the fitness benefits of higher transmission rates and slower clearance rates, thus exhibiting the hypothesized virulence trade-off. This evolutionary explanation of virulence appears to accord well with the clinical and molecular explanations of pathogenesis that involve cytoadherence, red cell invasion and immune evasion, although direct evidence of the fitness advantages of these mechanisms is scarce. One implication of this evolutionary view of virulence is that parasite populations are expected to evolve new levels of virulence in response to medical interventions such as vaccines and drugs.
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Affiliation(s)
- Margaret J Mackinnon
- School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, Scotland, UK.
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31
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Ebert D, Bull JJ. Challenging the trade-off model for the evolution of virulence: is virulence management feasible? Trends Microbiol 2003; 11:15-20. [PMID: 12526850 DOI: 10.1016/s0966-842x(02)00003-3] [Citation(s) in RCA: 213] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Progress in understanding the evolution of infectious diseases has inspired proposals to manage the evolution of pathogen (including parasite) virulence. A common view is that social interventions that lower pathogen transmission will indirectly select lower virulence because of a trade-off between transmission and virulence. Here, we argue that there is little theoretical justification and no empirical evidence for this plan. Although a trade-off model might apply to some pathogens, the mechanism appears too weak for rapid selection of substantial changes in virulence. Direct selection against virulence itself might be a more rewarding approach to managing the evolution of virulence.
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Affiliation(s)
- Dieter Ebert
- Ecologie et évolution, Département de biologie, Université de Fribourg, Chemin du Musée 10, Switzerland
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Ferreira MU, Nair S, Hyunh TV, Kawamoto F, Anderson TJC. Microsatellite characterization of Plasmodium falciparum from cerebral and uncomplicated malaria patients in southern Vietnam. J Clin Microbiol 2002; 40:1854-7. [PMID: 11980977 PMCID: PMC130917 DOI: 10.1128/jcm.40.5.1854-1857.2002] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2001] [Revised: 11/12/2001] [Accepted: 12/04/2001] [Indexed: 11/20/2022] Open
Abstract
If parasite genotype influences the clinical course of malaria, we expect that isolates from patients with similar pathology would be more closely related than would be expected by chance. To explore this prediction, we typed nine microsatellite markers in sympatric Plasmodium falciparum isolates from cerebral and uncomplicated malaria patients from Vietnam. Temporal structure and linkage disequilibrium were also examined in this data set.
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Affiliation(s)
- Marcelo U Ferreira
- Department of Parasitology, Institute for Biomedical Sciences, University of São Paulo, Av. Prof. lineu Prestes 1374, 05508-900 São Paulo (SP), Brazil.
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