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Search Results: 1 - 10 of 247488 matches for " Chandy C John "
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Malaria hotspot areas in a highland Kenya site are consistent in epidemic and non-epidemic years and are associated with ecological factors
Kacey C Ernst, Samson O Adoka, Dickens O Kowuor, Mark L Wilson, Chandy C John
Malaria Journal , 2006, DOI: 10.1186/1475-2875-5-78
Abstract: To address this issue, spatial distribution of malaria incidence and the relationship of ecological factors to malaria incidence were assessed in the highland area of Kipsamoite, Kenya, from 2001–2004.Clustering of disease in a single geographic "hotspot" area occurred in epidemic and non-epidemic years, with a 2.6 to 3.2-fold increased risk of malaria inside the hotspot, as compared to outside the area (P < 0.001, all 4 years). Altitude and proximity to the forest were independently associated with increased malaria risk in all years, including epidemic and non-epidemic years.In this highland area, areas of high malaria risk are consistent in epidemic and non-epidemic years and are associated with specific ecological risk factors. Ongoing interventions in areas of ecological risk factors could be a cost-effective method of significantly reducing malaria incidence and blunting or preventing epidemics, even in the absence of malaria early warning systems. Further studies should be conducted to see if these findings hold true in varied highland settings.It has been estimated that 34 million individuals in highland areas of East Africa are at risk for malaria [1] and malaria in these highland areas has been responsible for numerous deaths [2]. However, the levels of variation in malaria risk within these highland areas are not well described and only a few studies have investigated risk factors for malaria there [3-5]. Previous studies have demonstrated that malaria cases aggregate from the household to the countrywide level [3,6,7]. The determinants of such clustering are likely due to shared anthropogenic and environmental variables, as well as factors related to contagion such as population density and human interactions [8,9]. Brooker et al demonstrated that there was spatial clustering of malaria cases in children during an epidemic in a single year in highland area of Kenya [3]. However, without data from multiple years, it is difficult to discern if clusters of
Cognition, behaviour and academic skills after cognitive rehabilitation in Ugandan children surviving severe malaria: a randomised trial
Paul Bangirana, Peter Allebeck, Michael J Boivin, Chandy C John, Connie Page, Anna Ehnvall, Seggane Musisi
BMC Neurology , 2011, DOI: 10.1186/1471-2377-11-96
Abstract: This parallel group randomised study was carried out in Kampala City, Uganda between February 2008 and October 2010. Sixty-one Ugandan children aged 5 to 12 years with severe malaria were assessed for cognition (using the Kaufman Assessment Battery for Children, second edition and the Test of Variables of Attention), academic skills (Wide Range Achievement Test, third edition) and psychopathologic behaviour (Child Behaviour Checklist) three months after an episode of severe malaria. Twenty-eight were randomised to sixteen sessions of computerised cognitive rehabilitation training lasting eight weeks and 33 to a non-treatment group. Post-intervention assessments were done a month after conclusion of the intervention. Analysis of covariance was used to detect any differences between the two groups after post-intervention assessment, adjusting for age, sex, weight for age z score, quality of the home environment, time between admission and post-intervention testing and pre-intervention score. The primary outcome was improvement in attention scores for the intervention group. This trial is registered with Current Controlled Trials, number ISRCTN53183087.Significant intervention effects were observed in the intervention group for learning mean score (SE), [93.89 (4.00) vs 106.38 (4.32), P = 0.04] but for working memory the intervention group performed poorly [27.42 (0.66) vs 25.34 (0.73), P = 0.04]. No effect was observed in the other cognitive outcomes or in any of the academic or behavioural measures.In this pilot study, our computerised cognitive training program three months after severe malaria had an immediate effect on cognitive outcomes but did not affect academic skills or behaviour. Larger trials with follow-up after a few years are needed to investigate whether the observed benefits are sustained.ISRCTN: ISRCTN53183087Cognitive deficits are common in children who have suffered from severe malaria having neurological involvement [1]. Severe malaria with neurolo
Malaria treatment-seeking behaviour and recovery from malaria in a highland area of Kenya
Peter O Sumba, S Lindsey Wong, Hemal K Kanzaria, Kelsey A Johnson, Chandy C John
Malaria Journal , 2008, DOI: 10.1186/1475-2875-7-245
Abstract: To assess treatment-seeking behaviour for malaria in these areas, a questionnaire was administered to 117 randomly selected households in the highland area of Kipsamoite, Kenya. Self-reported episodes of malaria occurred in 100 adults and 66 children.The most frequent initial sources of treatment for malaria in adults and children were medical facilities (66.0% and 66.7%) and local shops (19.0% and 30.3%). Adults and children who initially visited a medical facility for treatment were significantly more likely to recover and require no further treatment than those who initially went to a local shop (adults, 84.9% v. 36.8%, P < 0.0001, and children, 79.6% v. 40.0%, P = 0.002, respectively). Individuals who attended medical facilities recalled receiving anti-malarial medication significantly more frequently than those who visited shops (adults, 100% vs. 29.4%, and children, 100% v. 5.0%, respectively, both P < 0.0001).A significant proportion of this highland population chooses local shops for initial malaria treatment and receives inappropriate medication at these localshops, reslting in delay of effective treatment. Shopkeeper education has the potential to be a component of prevention or containment strategies for malaria epidemics in highland areas.Malaria is a leading cause of death in children under the age of five years in sub-Saharan Africa [1]. The Roll-Back Malaria (RBM) initiative is working to improve prevention efforts in affected countries, through insecticide-treated nets (ITNs), indoor residual spraying (IRS) of pesticides, and intermittent preventive treatment (IPT) for pregnant women [2]. RBM also focuses on intervention efforts via effective anti-malarial regimens like artemesinin-based combination therapy (ACT), pre-empting epidemics in epidemic-prone areas, and improving home management of the disease. Rapid, effective treatment response with ACT is currently the most effective treatment option in sub-Saharan Africa, considering the current state
Interferon-gamma responses to Plasmodium falciparum liver-stage antigen-1 and merozoite-surface protein-1 increase with age in children in a malaria holoendemic area of western Kenya
Kiprotich Chelimo, Peter O Sumba, James W Kazura, Ayub V Ofula, Chandy C John
Malaria Journal , 2003, DOI: 10.1186/1475-2875-2-37
Abstract: A cross sectional study was conducted to evaluate T cell cytokine responses to the P. falciparum pre-erythrocytic antigen liver-stage antigen-1 (LSA-1) and the blood-stage antigen merozoite-surface protein-1 (MSP-1) in children under five years of age residing in a malaria holoendemic region of western Kenya. Interferon-γ (IFN-γ) and interleukin-10 (IL-10) responses to the LSA-1 T3 peptide (aa 1813–1835) and the MSP-1 aa20–39 peptide were tested in 48 children.The proportion of children producing IFN-γ to LSA-1 and to MSP-1 increased with age: in the 0–12, 13–24, 25–36 and 37–48 month age groups, zero, 11.1, 36.4 and 40% of children had IFN-γ responses to LSA-1 (p = 0.019), and 10, 10, 27.7 and 40% of children had IFN-γ responses to MSP-1 (p = 0.07), respectively. In contrast, the proportion of children producing IL-10 to LSA-1 and MSP-1 was similar in all age groups.The data suggest that development of IFN-γ responses to LSA-1 and MSP-1 requires increased age and/or repeated exposure, whereas IL-10 responses to these antigens may occur at any age and with limited exposure. The data also demonstrate that by the age of 4 years, children in a malaria holoendemic area develop frequencies of IFN-γ responses to LSA-1 and MSP-1 similar to those seen in adults in the area.In malaria holoendemic areas, where malaria is stable and intense throughout the year, morbidity and mortality from Plasmodium falciparummalaria occur primarily in children aged 6–24 months and decrease significantly after 24 months of age [1]. Age-related protection from P. falciparum infection and disease in these areas is thought to be related to acquisition of cellular and humoral immunity to pre-erythrocytic and blood-stage P. falciparum antigens [2].T lymphocyte cytokine production to P. falciparum pre-erythrocytic and blood-stage antigens, particularly IFN-γ and IL-10 production, appears to be important in induction and maintenance of immunity to P. falciparum in naturally exposed populations [2].
The Association between Cognition and Academic Performance in Ugandan Children Surviving Malaria with Neurological Involvement
Paul Bangirana, Jeremiah Menk, Chandy C. John, Michael J. Boivin, James S. Hodges
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0055653
Abstract: Background The contribution of different cognitive abilities to academic performance in children surviving cerebral insult can guide the choice of interventions to improve cognitive and academic outcomes. This study's objective was to identify which cognitive abilities are associated with academic performance in children after malaria with neurological involvement. Methods 62 Ugandan children with a history of malaria with neurological involvement were assessed for cognitive ability (working memory, reasoning, learning, visual spatial skills, attention) and academic performance (reading, spelling, arithmetic) three months after the illness. Linear regressions were fit for each academic score with the five cognitive outcomes entered as predictors. Adjusters in the analysis were age, sex, education, nutrition, and home environment. Exploratory factor analysis (EFA) and structural equation models (SEM) were used to determine the nature of the association between cognition and academic performance. Predictive residual sum of squares was used to determine which combination of cognitive scores was needed to predict academic performance. Results In regressions of a single academic score on all five cognitive outcomes and adjusters, only Working Memory was associated with Reading (coefficient estimate = 0.36, 95% confidence interval = 0.10 to 0.63, p<0.01) and Spelling (0.46, 0.13 to 0.78, p<0.01), Visual Spatial Skills was associated with Arithmetic (0.15, 0.03 to 0.26, p<0.05), and Learning was associated with Reading (0.06, 0.00 to 0.11, p<0.05). One latent cognitive factor was identified using EFA. The SEM found a strong association between this latent cognitive ability and each academic performance measure (P<0.0001). Working memory, visual spatial ability and learning were the best predictors of academic performance. Conclusion Academic performance is strongly associated with the latent variable labelled “cognitive ability” which captures most of the variation in the individual specific cognitive outcome measures. Working memory, visual spatial skills, and learning together stood out as the best combination to predict academic performance.
Local topographic wetness indices predict household malaria risk better than land-use and land-cover in the western Kenya highlands
Justin M Cohen, Kacey C Ernst, Kim A Lindblade, John M Vulule, Chandy C John, Mark L Wilson
Malaria Journal , 2010, DOI: 10.1186/1475-2875-9-328
Abstract: The topographic wetness index, an estimate of predicted water accumulation in a defined area, was generated from a digital terrain model of the landscape surrounding households in two neighbouring western Kenyan highland communities. Variables determined to best encompass the variance in this topographic wetness surface were calculated at a household level. Land-cover/land-use information was extracted from a high-resolution satellite image using an object-based classification method. Topographic and land-cover variables were used individually and in combination to predict household-level malaria in the communities through an iterative split-sample model fitting and testing procedure. Models with only topographic variables were compared to those with additional predictive factors related to land-cover/land-use to investigate whether these environmental factors improved prediction of malaria based on the shape of the land alone.Variables related to topographic wetness proved most useful in predicting the households of individuals contracting malaria in this region of rugged terrain. Other variables related to human modification of the environment also demonstrated clear associations with household malaria. However, these land-cover/land-use variables failed to produce unambiguous improvements in statistical predictive models controlling for important topographic factors, with none improving prediction of household-level malaria more than 75% of the time.Topographic wetness values in this region of highly varied terrain more accurately predicted houses at greater risk of malaria than did consideration of land-cover/land-use characteristics. As such, those planning control or local elimination strategies in similar highland regions may use topographic and geographic characteristics to effectively identify high-receptivity regions that may require enhanced vigilance.Local elimination of malaria requires identification of residual transmission foci [1], while optimal tar
Topography-derived wetness indices are associated with household-level malaria risk in two communities in the western Kenyan highlands
Justin M Cohen, Kacey C Ernst, Kim A Lindblade, John M Vulule, Chandy C John, Mark L Wilson
Malaria Journal , 2008, DOI: 10.1186/1475-2875-7-40
Abstract: Hydrologic modelling techniques were adapted to predict the flow of water across the landscape surrounding households in two communities in the western Kenyan highlands. These surface analyses were used to generate indices describing predicted water accumulation in regions surrounding the study area. Households with and without malaria were compared for their proximity to regions of high and low predicted wetness. Predicted wetness and elevation variables were entered into bivariate and multivariate regression models to examine whether significant associations with malaria were observable at small spatial scales.On average, malaria case households (n = 423) were located 280 m closer to regions with very high wetness indices than non-malaria "control" households (n = 895) (t = 10.35, p < 0.0001). Distance to high wetness indices remained an independent predictor of risk after controlling for household elevation in multivariate regression (OR = 0.93 [95% confidence interval = 0.89–0.96] for a 100 m increase in distance). For every 10 m increase in household elevation, there was a 12% decrease in the odds of the house having a malaria case (OR = 0.88 [0.85–0.90]). However, after controlling for distance to regions of high predicted wetness and the community in which the house was located, this reduction in malaria risk was not statistically significant (OR = 0.98 [0.94–1.03]).Proximity to terrain with high predicted water accumulation was significantly and consistently associated with increased household-level malaria incidence, even at small spatial scales with little variation in elevation variables. These results suggest that high wetness indices are not merely proxies for valley bottoms, and hydrologic flow models may prove valuable for predicting areas of high malaria risk in highland regions. Application in areas where malaria surveillance is limited could identify households at higher risk and help focus interventions.Elevation has long been recognized to be ass
Characterization of immunoglobulin G antibodies to Plasmodium falciparum sporozoite surface antigen MB2 in malaria exposed individuals
Thanh V Nguyen, John B Sacci, Patricia de la Vega, Chandy C John, Anthony A James, Angray S Kang
Malaria Journal , 2009, DOI: 10.1186/1475-2875-8-235
Abstract: Fragments of polypeptide regions of MB2 were constructed as recombinant fusions sandwiched between glutathione S-transferase and a hexa histidine tag for bacterial expression. The hexa histidine tag affinity purified proteins were used to immunize rabbits and the polyclonal sera evaluated in an in vitro inhibition of sporozoite invasion assay. The proteins were also used in immunoblots with sera from a limited number of donors immunized via the bites of P. falciparum infected irradiated mosquitoes and plasma and serum obtained from naturally exposed individuals in Kenya.Rabbit polyclonal antibodies targeting the non-repeat region of the basic domain of MB2 inhibited sporozoites entry into HepG2-A16 cells in vitro. Analysis of serum from five human volunteers that were immunized via the bites of P. falciparum infected irradiated mosquitoes that developed immunity and were completely protected against subsequent challenge with non-irradiated parasite also had detectable levels of antibody against MB2 basic domain. In contrast, in three volunteers not protected, anti-MB2 antibodies were below the level of detection. Sera from protected volunteers preferentially recognized a non-repeat region of the basic domain of MB2, whereas plasma from naturally-infected individuals also had antibodies that recognize regions of MB2 that contain a repeat motif in immunoblots. Sequence analysis of eleven field isolates and four laboratory strains showed that these antigenic regions of the basic domain of the MB2 gene are highly conserved in parasites obtained from different parts of the world. Moreover, anti-MB2 antibodies also were detected in the plasma of 83% of the individuals living in a malaria endemic area of Kenya (n = 41).A preliminary analysis of the human humoral response against MB2 indicates that it may be an additional highly conserved target for immune intervention at the pre-erythrocytic stage of P. falciparum life cycle.Parasites of the Plasmodium species that are tra
Changes in B Cell Populations and Merozoite Surface Protein-1-Specific Memory B Cell Responses after Prolonged Absence of Detectable P. falciparum Infection
Cyrus Ayieko, Alexander C. Maue, Walter G. Z. O. Jura, Gregory S. Noland, George Ayodo, Rosemary Rochford, Chandy C. John
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0067230
Abstract: Clinical immunity to malaria declines in the absence of repeated parasite exposure. However, little is known about how B cell populations and antigen-specific memory B cells change in the absence of P. falciparum infection. A successful indoor residual insecticide spraying campaign in a highland area of western Kenya, led to an absence of blood-stage P. falciparum infection between March 2007 and April 2008. We assessed memory B cell responses in 45 adults at the beginning (April 2008) and end (April 2009) of a subsequent 12-month period during which none of the adults had evidence of asymptomatic parasitemia or clinical disease. Antibodies and memory B cells to the 42-kDa portion of the merozoite surface protein-1 (MSP-142) were measured using ELISA and ELISPOT assays, respectively. B cell populations were characterized by flow cytometry. From 2008 to 2009, the prevalence of MSP-142-specific memory B cells (45% vs. 55%, respectively, P = 0.32) or antibodies (91% vs. 82%, respectively, P = 0.32) did not differ significantly, although specific individuals did change from positive to negative and vice versa, particularly for memory B cells, suggesting possible low-level undetected parasitemia may have occurred in some individuals. The magnitude of MSP-142-specific memory B cells and levels of antibodies to MSP-142 also did not differ from 2008 to 2009 (P>0.10 for both). However, from 2008 to 2009 the proportions of both class-switched atypical (CD19+IgD-CD27-CD21-IgM-) and class-switched activated (CD19+IgD-CD27+CD21-IgM-) memory B cells decreased (both P<0.001). In contrast, class-switched resting classical memory B cells (CD19+IgD-CD27+CD21+IgM-) increased (P<0.001). In this area of seasonal malaria transmission, a one- year absence of detectable P. falciparum infection was not associated with changes in the prevalence or level of MSP-142 specific memory B cells, but was associated with major changes in overall memory B cell subsets.
Socioeconomic Predictors of Cognition in Ugandan Children: Implications for Community Interventions
Paul Bangirana,Chandy C. John,Richard Idro,Robert O. Opoka,Justus Byarugaba,Anne M. Jurek,Michael J. Boivin
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0007898
Abstract: Several interventions to improve cognition in at risk children have been suggested. Identification of key variables predicting cognition is necessary to guide these interventions. This study was conducted to identify these variables in Ugandan children and guide such interventions.
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