Prevalence Of Plasmodium Falciparum Malaria Research Articles

Distribution of Plasmodium falciparum K13 gene polymorphisms across transmission settings in Ghana

Malaria is a significant global health concern, with a majority of cases in Sub-Saharan African nations. Numerous antimalarial drugs have been developed to counter the rampant prevalence of Plasmodium falciparum malaria. Artemisinin-based Combination Therapy (ACT) has served as the primary treatment of uncomplicated malaria in Ghana since 2005. However, a growing concern has emerged due to the escalating reports of ACT resistance, particularly in Southeast Asia, and its encroachment into Africa. Specifically, mutations in the Kelch propeller domain on chromosome 13 (Pfk13) have been linked to ACT resistance. Yet, our understanding of mutation prevalence in Africa remains largely uncharted. In this study, we compared Pfk13 sequences obtained from 172 P. falciparum samples across three ecological and transmission zones in Ghana. We identified 27 non-synonymous mutations among these sequences, of which two of the mutations, C580Y (found in two samples from the central region) and Y493H (found in one sample from the north), had previously been validated for their association with artemisinin resistance, a phenomenon widespread in Southeast Asia. The Pfk13 gene diversity was most pronounced in the northern savannah than the central forest and south coastal regions, where transmission rates are lower. The observed mutations were not significantly associated with geographical regions, suggesting a frequent spread of mutations across the country. The ongoing global surveillance of artemisinin resistance remains pivotal, and our findings provides insights into the potential spread of resistant parasites in West Africa. Furthermore, the identification of novel codon mutations in this study raises their potential association to ACT resistance, warranting further investigation through in vitro assays to ascertain their functional significance.

Factors Affecting the Performance of HRP2-Based Malaria Rapid Diagnostic Tests.

The recent COVID-19 pandemic has profoundly impacted global malaria elimination programs, resulting in a sharp increase in malaria morbidity and mortality. To reduce this impact, unmet needs in malaria diagnostics must be addressed while resuming malaria elimination activities. Rapid diagnostic tests (RDTs), the unsung hero in malaria diagnosis, work to eliminate the prevalence of Plasmodium falciparum malaria through their efficient, cost-effective, and user-friendly qualities in detecting the antigen HRP2 (histidine-rich protein 2), among other proteins. However, the testing mechanism and management of malaria with RDTs presents a variety of limitations. This paper discusses the numerous factors (including parasitic, host, and environmental) that limit the performance of RDTs. Additionally, the paper explores outside factors that can hinder RDT performance. By understanding these factors that affect the performance of HRP2-based RDTs in the field, researchers can work toward creating and implementing more effective and accurate HRP2-based diagnostic tools. Further research is required to understand the extent of these factors, as the rapidly changing interplay between parasite and host directly hinders the effectiveness of the tool.

Spatial analysis of climatic factors and plasmodium falciparum malaria prevalence among children in Ghana

Malaria is a major public health problem especially in Africa where 94% of global malaria cases occur. Malaria prevalence and mortalities are disproportionately higher among children. In 2019, children accounted for 67% of malaria deaths globally. Recently, climatic factors have been acknowledged to influence the number and severity of malaria cases. Plasmodium falciparum—the most deadly malaria parasite, accounts for more than 95% of malaria infections among children in Ghana. Using the 2017 Ghana Demographic Health Survey data, we examined the local variation in the prevalence and climatic determinants of child malaria. The findings showed that climatic factors such as temperature, rainfall aridity and Enhanced Vegetation Index are significantly and positively associated with Plasmodium falciparum malaria prevalence among children in Ghana. However, there are local variations in how these climatic factors affect child malaria prevalence. Plasmodium falciparum malaria prevalence was highest among children in the south western, north western and northern Ghana.

Prevalence of Plasmodium falciparum Malaria among Children Residing in Urban and Peri-urban Settlements in Rivers State

Urban and peri-urban areas are considered to be at lower risk of malaria compared to rural areas because of improved housing, higher socioeconomic status, improved environmental sanitation, and a limited number of breeding sites for mosquitoes. Reports have shown that there is an increased prevalence of malaria in urban and peri-urban areas but it has not been established which of these areas is at risk. The aim of this study, therefore, is to determine the prevalence rate of Plasmodium falciparum malaria infection among children in urban and peri-urban areas of Rivers State. A total of 601 and 500 blood samples were collected from urban and peri-urban areas respectively and examined using standard microscopy technique for detection of malaria parasites in blood samples. From the urban area, 282 tested positive out of 601 blood samples that were examined, giving the prevalence rate of 47% while in the peri-urban settlement, a total of 210 out of 500 tested positive to Plasmodium falciparum giving the prevalence rate of 42%. When the age was considered, the highest prevalence was recorded in children between 1-3 years and 7-12 years in urban settlement while in peri-urban, the highest prevalence was recorded in children between the age of 4-6 years with a prevalence of 45% and 46% respectively. Although the prevalence rates are relatively high. There is no significant difference between the prevalence rate in urban areas and that of peri-urban areas. Conclusively, intensive efforts should be made in controlling malaria parasites not only in rural areas but also in urban and peri-urban areas in Rivers State.

Performance evaluation of RDT, light microscopy, and PET-PCR for detecting Plasmodium falciparum malaria infections in the 2018 Zambia National Malaria Indicator Survey

BackgroundZambia continues to advance on the path to elimination with significant reductions in malaria morbidity and mortality. Crucial components that have contributed to progress thus far and are necessary for achieving the national malaria elimination goals include properly identifying and treating all malaria cases through accurate diagnosis. This study sought to compare and assess the diagnostic performance of Rapid Diagnostic Tests (RDT) and Light Microscopy (LM) with photo-induced electron transfer polymerase chain reaction (PET-PCR) as the gold standard using 2018 Malaria Indicator Survey (MIS) data across Zambia to better understand diagnostic accuracy metrics and how these vary across a transmission gradient.MethodsCross-sectional samples collected in a nationally representative survey from 7 provinces in Zambia were tested for the presence of malaria parasites by light microscopy (LM), rapid diagnostic test (RDT) and the gold standard PET-PCR. Diagnostic performance was assessed including sensitivity, specificity, negative- and positive-predictive values across a wide malaria transmission spectrum. Diagnostic accuracy metrics were measured, and statistically significant differences were calculated between test methods for different outcome variables.ResultsFrom the individuals included in the MIS, the overall prevalence of Plasmodium falciparum malaria was 32.9% by RDT, 19.4% by LM, and 23.2% by PET-PCR. Herein, RDT and LM diagnostic performance was compared against gold standard PET-PCR with LM displaying a higher diagnostic accuracy than RDTs (91.3% vs. 84.6% respectively) across the transmission spectrum in Zambia. However, the performance of both diagnostics was significantly reduced in low parasitaemia samples. Consistent with previous studies, RDT diagnostic accuracy was predominantly affected by a high rate of false positives.ConclusionsRDTs and LM both perform well across a range of transmission intensities within their respective target applications, i.e., in the community, for the former, where ease of use and speed of result is critical, and at the health facility, for the latter, where accuracy is prioritized. However, the performance of both diagnostic methods is adversely affected by low parasitaemia infections. As Zambia moves towards elimination more sensitive tools may be required to identify the last cases.

Estimating the potential impact of Attractive Targeted Sugar Baits (ATSBs) as a new vector control tool for Plasmodium falciparum malaria

BackgroundAttractive targeted sugar baits (ATSBs) are a promising new tool for malaria control as they can target outdoor-feeding mosquito populations, in contrast to current vector control tools which predominantly target indoor-feeding mosquitoes.MethodsIt was sought to estimate the potential impact of these new tools on Plasmodium falciparum malaria prevalence in African settings by combining data from a recent entomological field trial of ATSBs undertaken in Mali with mathematical models of malaria transmission. The key parameter determining impact on the mosquito population is the excess mortality due to ATSBs, which is estimated from the observed reduction in mosquito catch numbers. A mathematical model capturing the life cycle of P. falciparum malaria in mosquitoes and humans and incorporating the excess mortality was used to estimate the potential epidemiological effect of ATSBs.ResultsThe entomological study showed a significant reduction of ~ 57% (95% CI 33–72%) in mosquito catch numbers, and a larger reduction of ~ 89% (95% CI 75–100%) in the entomological inoculation rate due to the fact that, in the presence of ATSBs, most mosquitoes do not live long enough to transmit malaria. The excess mortality due to ATSBs was estimated to be lower (mean 0.09 per mosquito per day, seasonal range 0.07–0.11 per day) than the bait feeding rate obtained from one-day staining tests (mean 0.34 per mosquito per day, seasonal range 0.28–0.38 per day).ConclusionsFrom epidemiological modelling, it was predicted that ATSBs could result in large reductions (> 30% annually) in prevalence and clinical incidence of malaria, even in regions with an existing high malaria burden. These results suggest that this new tool could provide a promising addition to existing vector control tools and result in significant reductions in malaria burden across a range of malaria-endemic settings.

Asymptomatic Plasmodium falciparum malaria prevalence among adolescents and adults in Malawi, 2015\u20132016

Malaria remains a significant cause of morbidity and mortality in Malawi, with an estimated 18–19% prevalence of Plasmodium falciparum in children 2–10 years in 2015–2016. While children report the highest rates of clinical disease, adults are thought to be an important reservoir to sustained transmission due to persistent asymptomatic infection. The 2015–2016 Malawi Demographic and Health Survey was a nationally representative household survey which collected dried blood spots from 15,125 asymptomatic individuals ages 15–54 between October 2015 and February 2016. We performed quantitative polymerase chain reaction on 7,393 samples, detecting an overall P. falciparum prevalence of 31.1% (SE = 1.1). Most infections (55.6%) had parasitemias ≤ 10 parasites/µL. While 66.2% of individuals lived in a household that owned a bed net, only 36.6% reported sleeping under a long-lasting insecticide-treated net (LLIN) the previous night. Protective factors included urbanicity, greater wealth, higher education, and lower environmental temperatures. Living in a household with a bed net (prevalence difference 0.02, 95% CI − 0.02 to 0.05) and sleeping under an LLIN (0.01; − 0.02 to 0.04) were not protective against infection. Our findings demonstrate a higher parasite prevalence in adults than published estimates among children. Understanding the prevalence and distribution of asymptomatic infection is essential for targeted interventions.

Plasma cytokine profiles associated with rhodesiense sleeping sickness and falciparum malaria co-infection in North Eastern Uganda

BackgroundImmunological Human African Trypanosomiasis (HAT) studies often exclude malaria, although both infections overlap in specific endemic areas. During this co-infection, it is not known whether this parasitic interaction induces synergistic or antagonistic cytokine response among humans. This study determined prevalence of Plasmodium falciparum malaria among Trypanosoma brucei rhodesiense HAT and plasma cytokine profile levels associated with HAT and/or malaria infections.MethodsParticipants were recruited at Lwala hospital in north eastern Uganda: healthy controls (30), malaria (28), HAT (17), HAT and malaria (15) diagnosed by microscopy and PCR was carried out for parasite species identification. Plasma cytokine levels of Interferon-gamma (IFN-γ), Tumour Necrosis Factor-alpha (TNF-α), Interleukin (IL)-6, IL-10 and Transforming Growth Factor-beta (TGF-β) were measured by sandwich Enzyme-Linked Immuno Sorbent Assay and data statistically analysed using Graphpad Prism 6.0.ResultsThe prevalence of P. falciparum malaria among T. rhodesiense HAT cases was high (46.8%). Malaria and/or HAT cases presented significant higher plasma cytokine levels of IFN-γ, TNF-α, IL-6, IL-10 and TGF-β than healthy controls (P < 0.05). Levels of IFN-γ, IL-6 and IL-10 were significantly elevated in HAT over malaria (P < 0.05) but no significant difference in TNF-α and TGF-β between HAT and malaria (P > 0.05). Co-infection expressed significantly higher plasma IFN-γ, IL-6, and IL-10 levels than malaria (P < 0.05) but no significant difference with HAT mono-infection (P > 0.05). The TNF-α level was significantly elevated in co-infection over HAT or malaria mono-infections (P < 0.05) unlike TGF-β level. Significant positive correlations were identified between IFN-γ verses TNF-α and IL-6 verses IL-10 in co-infection (Spearman’s P < 0.05).ConclusionsThe T. b. rhodesiense significantly induced the cytokine response more than P. falciparum infections. Co-infection led to synergistic stimulation of pro-inflammatory (IFN-γ, TNF-α), and anti-inflammatory (IL-6, and IL-10) cytokine responses relative to malaria mono-infection. Level of TNF-α partially indicates the effect induced by T. b. rhodesiense and P. falciparum mono-infections or a synergistic interaction of co-infections which may have adverse effects on pathogenesis, prognosis and resolution of the infections.Trial registration VCD-IRC/021, 26/08/2011; HS 1089, 16/01/2012

A geostatistical framework for combining spatially referenced disease prevalence data from multiple diagnostics.

Multiple diagnostic tests are often used due to limited resources or because they provide complementary information on the epidemiology of a disease under investigation. Existing statistical methods to combine prevalence data from multiple diagnostics ignore the potential overdispersion induced by the spatial correlations in the data. To address this issue, we develop a geostatistical framework that allows for joint modelling of data from multiple diagnostics by considering two main classes of inferential problems: (a) to predict prevalence for a gold-standard diagnostic using low-cost and potentially biased alternative tests; (b) to carry out joint prediction of prevalence from multiple tests. We apply the proposed framework to two case studies: mapping Loa loa prevalence in Central and West Africa, using miscroscopy, and a questionnaire-based test called RAPLOA; mapping Plasmodium falciparum malaria prevalence in the highlands of Western Kenya using polymerase chain reaction and a rapid diagnostic test. We also develop a Monte Carlo procedure based on the variogram in order to identify parsimonious geostatistical models that are compatible with the data. Our study highlights (a) the importance of accounting for diagnostic-specific residual spatial variation and (b) the benefits accrued from joint geostatistical modelling so as to deliver more reliable and precise inferences on disease prevalence.

A population-based study of the prevalence and risk factors of low-grade Plasmodium falciparum malaria infection in children aged 0-15years old in northern Tanzania.

Northern Tanzania experiences significant malaria-related morbidity and mortality, but accurate data are scarce. We update the data on patterns of low-grade Plasmodium falciparum malaria infection among children in northern Tanzania. Plasmodium falciparum malaria prevalence (pfPR) was assessed in a representative sample of 819 children enrolled in 94 villages in northern Tanzania between October 2015 and August 2016, using a complex survey design. Individual- and household-level risk factors for pfPR were elicited using structured questionnaires. pfPR was assessed using rapid diagnostic tests (RDTs) and thick film microscopy (TFM). Associations with pfPR, based on RDT, were assessed using adjusted odds ratios (aOR) and confidence intervals (CI) from weighted survey logistic regression models. Plasmodium falciparum malaria prevalence (pfPR) was 39.5% (95% CI: 31.5, 47.5) by RDT and 33.4% (26.0, 40.6) by TFM. pfPR by RDT was inversely associated with higher-education parents, especially mothers (5-7years of education: aOR 0.55; 95% CI: 0.31, 0.96, senior secondary education: aOR 0.10; 95% CI: 0.02, 0.55), living in a house near the main road (aOR 0.34; 95% CI: 0.15, 0.76), in a larger household (two rooms: aOR 0.40; 95% CI: 0.21, 0.79, more than two rooms OR 0.35; 95% CI: 0.20, 0.62). Keeping a dog near or inside the house was positively associated with pfPR (aOR 2.01; 95% CI: 1.26, 3.21). pfPR was not associated with bed-net use or indoor residual spraying. Nearly 40% of children in northern Tanzania had low-grade malaria antigenaemia. Higher parental education and household metrics but not mosquito bed-net use were inversely associated with pfPR.

A Cross-Sectional Population Study of Geographic, Age-Specific, and Household Risk Factors for Asymptomatic Plasmodium falciparum Malaria Infection in Western Kenya.

The burden of Plasmodium falciparum (Pf) malaria in Kenya is decreasing; however, it is still one of the top 10 causes of morbidity, particularly in regions of western Kenya. Between April 2015 and June 2016, we enrolled 965 apparently healthy children aged 0-15 years in former Nyanza and Western Provinces in Kenya to characterize the demographic, geographic, and household risk factors of asymptomatic malaria as part of an epidemiologic study to investigate the risk factors for endemic Burkitt lymphoma. The children were sampled using a stratified, multistage cluster sampling survey design. Malaria was assessed by rapid diagnostic test (RDT) and thick-film microscopy (TFM). Primary analyses of Pf malaria prevalence (pfPR) are based on RDT. Associations between weighted pfPR and potential risk factors were evaluated using logistic regression, accounting for the survey design. Plasmodium falciparum malaria prevalence was 36.0% (27.5%, 44.5%) by RDT and 22.3% (16.0%, 28.6%) by TFM. Plasmodium falciparum malaria prevalence was positively associated with living in the lake-endemic area (adjusted odds ratio [aOR] 3.46; 95% confidence interval [95% CI] 1.63, 7.37), paternal occupation as peasant farmer (aOR 1.87; 1.08, 3.26) or manual laborer (aOR 1.83; 1.00, 3.37), and keeping dogs (aOR 1.62; 0.98-2.69) or cows (aOR 1.52; 0.96-2.40) inside or near the household. Plasmodium falciparum malaria prevalence was inversely associated with indoor residual insecticide spraying (IRS) (aOR 0.44; 0.19, 1.01), having a household connected to electricity (aOR 0.47; 0.22, 0.98), and a household with two (aOR 0.45; 0.22, 0.93) or ≥ three rooms (aOR 0.41; 0.18, 0.93). We report high but geographically heterogeneous pfPR in children in western Kenya and significant associations with IRS and household-level socioeconomic factors.

Prevalence of Plasmodium Falciparum Malaria and the Antenatal Health Care Utilization for Prevention Among Pregnant Women in a Secondary Health Facility in Enugu State, Nigeria

Pregnant women in endemic areas are highly susceptible to malaria, and both the frequency and severity of the disease are higher in pregnant women than non- pregnant women.[1] In pregnancy, there is a transient depression of cell mediated immunity that allows foetal allograft retention but also interferes with resistance to various infectious diseases. Malaria infection during pregnancy is a major public health problem in the tropics and subtropics. It affects approximately 24 million pregnant women.[2] In the area of Africa with stable malaria transmission, plasmodium falciparum infection during pregnancy is estimated to cause as many as 10,000 maternal death each year, 8-14% of all low birth weight babies and 75,000-200,000 of all infant death.[3] In Nigeria, there is an estimated 25-30% of mortality in children under the age of five and 300,000 death each year due to malaria.[3] Studies have shown that 40% of pregnant African women start attending antenatal clinics in the first and second trimester of their pregnancy. [3] In addition, pregnant women are at immense risk of malaria due to natural immune depression in pregnancy. [4] The symptoms and complications of malaria during pregnancy differ with the intensity of malaria transmission and thus with the level of immunity the pregnant woman acquired. [5] Malaria cases and death have been increasing in the country mainly due to injudicious use of anti-malaria drugs, delayed health seeking and reliance on clinical judgment without laboratory confirmation in most of the peripheral health facilities. [6] There have been considerable numbers of reports about knowledge, attitude and practices relating to malaria and its control from different parts of Africa. Misconceptions concerning malaria still exist and the practices for the control of malaria have been unsatisfactory. [7] The promising news is that during the past decade, potentially more effective strategies for control of malaria in pregnancy have been developed and demonstrated to have a remarkable impact on improving the health of mothers and their new born. However, less than 5% of pregnant women have access to effective plasmodium specie prevention during pregnancy. [8] Malaria in pregnancy increases the chances of maternal anemia, miscarriages, stillbirths, low birth weight, abortion, growth retardation and death. It therefore becomes pertinent to study the prevalence of Plasmodium falciparum malaria among pregnant women attending antenatal clinic in Bishop Shanahan Hospital Nsukka as well as to ascertain their use of some of the antenatal health care services for prevention during pregnancy.

Cytokine profiles among patients co-infected with Plasmodium falciparum malaria and soil borne helminths attending Kampala International University Teaching Hospital, in Uganda

BackgroundMalaria and helminths share the same geographical distribution in tropical Africa. Studies of the interaction of helminth and malaria co-infection in humans have been few and are mainly epidemiological, with little information on cellular immune responses. This study aimed to determine Cytokine profiles among patients co-infected with Plasmodium falciparum malaria and soil borne helminth attending Kampala International University Teaching Hospital (KIU).MethodsA case control study of 240 patients were recruited at KIU teaching hospital. Patients with Plasmodium falciparum malaria were 55 (22.9%) and those with soil-borne helminths were 63 (26.3%). The controls were 89 (37.1%), while those co-infected with Plasmodium falciparum malaria and soil-borne helminths were 33 (13.8%). Cases were defined as having a positive blood smear for P. falciparum malaria, those with helminths or co-infections of the two. Negative controls were those with a negative blood smear for P. falciparum malaria and those with no stool parasitic infections. Patients presenting with signs and symptoms of malaria or those suspected of having helminths were recruited for the study. A panel of five cytokines (IFN-γ, TNF-α, IL-6, TGF-β and IL-10) were assayed from plasma samples in patients with and without Plasmodium falciparum malaria, patients with and without helminth, and then those co-infected with the two diseases diagnosis was done using thick blood smears stained with 10% Giemsa and stool examination was done following the Kato Katz technique following standard procedures.ResultsThe prevalence of Plasmodium falciparum malaria by sex was 28 (11.7%) and 27 (11.3%) in male and female respectively. The overall prevalence of soil borne helminth was 26.3%, and among those harbouring helminths, 13.8% were co-infected with Plasmodium falciparum. Cytokine levels significantly differed across Plasmodium falciparum malaria, soil borne helminth infected patients and health controls for IFN-γ (P = 0.023), IL-10 (P = 0.008) and TGF-β (P = 0.0001). Cytokine levels significantly differed across Plasmodium falciparum malaria, soil borne helminth infected patients and patients co-infected with Plasmodium falciparum malaria and soil borne helminth for IL-10 (P = 0.004), IL-6 (P = 0.011) and TGF-β (P = 0.003).ConclusionAn up-regulation of IFN-γ during Plasmodium falciparum malaria and an up-regulation of IL-10 and TGF-β in soil borne helminth infections was demonstrated. We demonstrate that co-infections of Plasmodium falciparum and soil borne helminth lead to an up-regulation of IL-10 and IL-6 and a down-regulation of TGF-β.Trial registration No17/10-16

The HLA-B landscape of Africa: Signatures of pathogen-driven selection and molecular identification of candidate alleles to malaria protection.

Human leukocyte antigen (HLA) genes play a key role in the immune response to infectious diseases, some of which are highly prevalent in specific environments, like malaria in sub-Saharan Africa. Former case-control studies showed that one particular HLA-B allele, B*53, was associated with malaria protection in Gambia, but this hypothesis was not tested so far within a population genetics framework. In this study, our objective was to assess whether pathogen-driven selection associated with malaria contributed to shape the HLA-B genetic landscape of Africa. To that aim, we first typed the HLA-A and -B loci in 484 individuals from 11 populations living in different environments across the Sahel, and we analysed these data together with those available for 29 other populations using several approaches including linear modelling on various genetic, geographic and environmental parameters. In addition to relevant signatures of populations' demography and migrations history in the genetic differentiation patterns of both HLA-A and -B loci, we found that the frequencies of three HLA alleles, B*53, B*78 and A*74, were significantly associated with Plasmodium falciparum malaria prevalence, suggesting their increase through pathogen-driven selection in malaria-endemic environments. The two HLA-B alleles were further identified, by high-throughput sequencing, as B*53:01:01 (in putative linkage disequilibrium with one HLA-C allele, C*04:01:01:01) and B*78:01 in all but one individuals tested, making them appropriate candidates to malaria protection. These results highlight the role of environmental factors in the evolution of the HLA polymorphism and open key perspectives for functional studies focusing on HLA peptide-binding properties.

Comparative prevalence of Plasmodium falciparum malaria in patients attending Okelele Health Centre, Okelele, Ilorin, Nigeria

Background: In Okelele, Ilorin, Kwara State, Nigeria, malaria remains an important public health concern with a little information about its prevalence. Objective: To determine the prevalence of malaria infection at Okelele Health Centre, Okelele, Ilorin. Methodology: A cross-sectional descriptive study in which patients were diagnosed clinically with severe or uncomplicated malaria at the study site was conducted. Rapid diagnostic testing (RDT) for malaria and microscopy using Giemsa staining by thick and thin blood smears were done for study patients. Results: In this study, 200 malaria patients attending Okelele Health Centre, Okelele, Ilorin, were tested for malaria infection, with females having the highest prevalence rates and parasitemia density. The highest positivity rates were found in children <6 years while adolescents had the lowest prevalence rates. Socioeconomic factors of patients such as occupation and education played a major role in malaria prevalence. Conclusion: Although RDT is quick and easy to use, negative malaria cases gotten by RDT should be confirmed by expert microscopy to prevent misdiagnosis of malaria.

Influence of protected areas on malaria prevalence in Sub-Saharan Africa

IntroductionDespite exponential growth in the number and extent of protected areas globally, their role within disease dynamics remains unclear. Protected areas shape many biophysical and social factors related to malaria prevalence such as land use-land cover, biodiversity, socioeconomic conditions, and human behavior. This work examines the extent to which protected areas influence Plasmodium falciparum malaria prevalence within surrounding human populations throughout Sub-Saharan Africa.. MethodsUsing malaria prevalence data from 2008 to 2012, we tested for differences in mean malaria prevalence at survey locations according to the IUCN classification of the nearest protected area. We also used dual logistic regression and Random Forest approaches to model malaria burdens at survey locations using a variety of known biophysical determinants of malaria in addition to protected area related covariates. ResultsWe found that malaria prevalence differed by IUCN class, with survey locations near IUCN classes Ia and III exhibiting significantly higher prevalence values than all other classes. Additionally, distance to the nearest protected area emerged as an important predictor of malaria prevalence in the logistic regression model, with lower malaria prevalence at locations closer to protected areas (OR: 1.14; 95% CI: 1.10–1.17). Distance was of moderate importance in the Random Forest models; however, the relationship between distance and prevalence was nonlinear.. ConclusionsWe show that, at a continental scale, malaria prevalence was lower for populations closer to protected areas in Africa, compared to farther away. However, we also found evidence of spatially complex relationships, both around individual protected areas, and across protected areas at this geographic extent, reinforcing the need for additional, small-scale case studies. Ultimately, by showing a link between protected areas and disease presence, this work helps improve understanding of the complex, multiscalar drivers of malaria..

A household randomized, controlled trial of the efficacy of 0.03% transfluthrin coils alone and in combination with long-lasting insecticidal nets on the incidence of Plasmodium falciparum and Plasmodium vivax malaria in Western Yunnan Province, China.

BackgroundMosquito coils are the most commonly used household insecticidal product in the world with sales exceeding 50 billion coils, used by two billion people worldwide annually. Despite strong evidence that coils prevent mosquito bites a systematic review concluded that there is no evidence that burning mosquito coils prevents malaria acquisition. Therefore, the current trial was designed to measure and compare prevention of malaria infection by mosquito coils or long-lasting insecticidal net (LLIN) or a combination of the two in Yunnan, China in the Greater Mekong sub-region.MethodsA four-arm single blind household-randomized design was chosen as coils emanate insecticide throughout the household. Households enrolled at baseline were randomly allocated by the lottery method to one of the four intervention arms: (i) nothing, (ii) 0.03% transfluthrin coils alone, (iii) deltamethrin long-lasting insecticide treated nets, (LLINs) alone or (iv) a combination of transfluthrin coils and deltamethrin LLINs. All household members were recruited to the study, with only those households excluded with pregnant or breastfeeding mothers, members with chest complaints or allergies or members that regularly slept away from home. The main outcome of interest was Plasmodium falciparum malaria prevalence detected by rapid diagnostic tests (RDTs) during six repeated monthly cross-sectional surveys. The secondary outcome of interest was the effect on Plasmodium vivax prevalence detected in the same way.ResultsA total of 2,052 households were recruited into the study, comprising 7,341 individuals The odds ratios of testing positive by RDT with P. falciparum or P. vivax were >75% lower for all intervention arms compared with the control arm. Coils alone provided 77% protection (95% CI: 50%-89%), LLINs provided 91% protection (95% CI: 72%-97%) and the combination of coils and LLINs provided 94% protection (95% CI: 77%-99%) against P. falciparum compared with the control arm. There was no statistically significant difference between the protective efficacies of the different interventions.ConclusionsThis is the first robust clinical evaluation of transfluthrin mosquito coils as a means to reduce malaria and the high degree of infection prevented would indicate they represent a potentially highly effective tool, which could be integrated into larger vector control programmes.Trial registrationClinicalTrials.gov Identifier: NCT00442442, March 2007.

Relationship between Plasmodium falciparum malaria prevalence, genetic diversity and endemic Burkitt lymphoma in Malawi

Endemic Burkitt lymphoma (eBL) has been linked to Plasmodium falciparum (Pf) malaria infection, but the contribution of infection with multiple Pf genotypes is uncertain. We studied 303 eBL (cases) and 274 non eBL-related cancers (controls) in Malawi using a sensitive and specific molecular-barcode array of 24 independently segregating Pf single nucleotide polymorphisms. Cases had a higher Pf malaria prevalence than controls (64.7% versus 45.3%; odds ratio [OR] 2.1, 95% confidence interval (CI): 1.5 to 3.1). Cases and controls were similar in terms of Pf density (4.9 versus 4.5 log copies, p = 0.28) and having ≥3 non-clonal calls (OR 2.7, 95% CI: 0.7-9.9, P = 0.14). However, cases were more likely to have a higher Pf genetic diversity score (153.9 versus 133.1, p = 0.036), which measures a combination of clonal and non-clonal calls, than controls. Further work is needed to evaluate the possible role of Pf genetic diversity in the pathogenesis of endemic BL.

Travel risk, malaria importation and malaria transmission in Zanzibar

The prevalence of Plasmodium falciparum malaria in Zanzibar has reached historic lows. Improving control requires quantifying malaria importation rates, identifying high-risk travelers, and assessing onwards transmission.Estimates of Zanzibar's importation rate were calculated through two independent methodologies. First, mobile phone usage data and ferry traffic between Zanzibar and mainland Tanzania were re-analyzed using a model of heterogeneous travel risk. Second, a dynamic mathematical model of importation and transmission rates was used.Zanzibar residents traveling to malaria endemic regions were estimated to contribute 1–15 times more imported cases than infected visitors. The malaria importation rate was estimated to be 1.6 incoming infections per 1,000 inhabitants per year. Local transmission was estimated too low to sustain transmission in most places.Malaria infections in Zanzibar largely result from imported malaria and subsequent transmission. Plasmodium falciparum malaria elimination appears feasible by implementing control measures based on detecting imported malaria cases and controlling onward transmission.

Prevalence of maternal and placental malaria and of neonatal low birth weight in a semi-urban area of Bamako (Mali)

In 2006, the Malian government established a program for free insecticide-treated net (ITNs) distribution during antenatal care visit (ANC) and intermittent preventive treatment during pregnancy with sulfadoxine-pyrimethamine (IPTp-SP) for pregnant women. In March to November of 2009, we conducted a cross-sectional study in peri-urban areas of Bamako, Mali to determine the malaria prevalence among pregnant women and their newborn children in the context of this policy. We included 379 pregnant women aged 15 to 45 years. At delivery, malaria was diagnosed using peripheral thick smears in mothers and newborns, as well as umbilical cord blood and placental blood. The prevalence of Plasmodium falciparum malaria was 2.4, 1.6 and 0.5% respectively in mother, placenta and cord samples; we observed a low birth weight rate of 12.1%. Approximately 77% of our parturient were housewives. The illiteracy rate among this group was 72.3%. Of the 379 women, 73% had at least three prenatal visits, 83% had received at least one free ITNs and 72% had received IPTp-SP during antenatal visit. Among them, 81% claimed to have complied with IPTp-SP. No congenital malaria was found. The prevalence of malaria in both mother and newborn has show a significant decrease in Bamako, compared with previous studies before the implementation of IPTp-SP policy in Mali. A high rate of coverage and use of IPTp-SP and ITNs correlate with lower malaria prevalence in pregnant women.