Bacteraemia complicating severe malaria in children

The association of intraleucocytic malaria pigment and disease severity in Papua New Guinean children with severe P. falciparum malaria

BACKGROUND

Plasmodium falciparum pigment-containing leucocytes (PCLs) are associated with adverse clinical manifestations of severe malaria in African children. However, limited data exist on the association of PCLs in settings outside of Africa.

METHODS

Thin films on peripheral blood slides obtained from children ages 6 months-10 y with severe malaria were examined for PCLs. The intraleucocytic pigment data were correlated with clinical phenotypic data such as severe anaemia, metabolic acidosis and coma to determine the association of PCLs with clinical phenotypes of severe malaria and outcome.

RESULTS

Of the 169 children with severe P. falciparum malaria confirmed by microscopy, 76% (129/169) had PCLs. Compared with children without PCLs, the presence (adjusted odds ratio [AOR] 3.2 [95% confidence interval {CI} 1.5 to 6.9], p≤0.01) and quantity (AOR 1.0 [95% CI 1.0 to 1.1], p=0.04) of pigment-containing monocytes (PCMs) was significantly associated with severe anaemia, while the quantity of both PCMs (AOR 1.0 [95% CI 1.0 to 1.1], p≤0.01) and pigment-containing neutrophils (AOR 1.0 [95% CI 1.0 to 1.1], p=0.01) was significantly associated with metabolic acidosis. Plasma P. falciparum histidine-rich protein-2 level negatively correlated with the platelet count (r=-0.5, p≤0.01) in patients with PCLs and no PCLs.

CONCLUSIONS

In Papua New Guinean children with severe P. falciparum malaria, the presence and quantity of PCLs are predictors of disease severity, severe anaemia and metabolic acidosis.

Malaria in Refugee Children Resettled to a Holoendemic Area of Sub-Saharan Africa

BACKGROUND

Malaria is a leading cause of morbidity and mortality in refugee children in high-transmission parts of Africa. Characterizing the clinical features of malaria in refugees can inform approaches to reduce its burden.

METHODS

The study was conducted in a high-transmission region of northern Zambia hosting Congolese refugees. We analyzed surveillance data and hospital records of children with severe malaria from refugee and local sites using multivariable regression models and geospatial visualization.

RESULTS

Malaria prevalence in the refugee settlement was similar to the highest burden areas in the district, consistent with the local ecology and leading to frequent rapid diagnostic test stockouts. We identified 2197 children hospitalized for severe malaria during the refugee crisis in 2017 and 2018. Refugee children referred from a refugee transit center (n = 63) experienced similar in-hospital mortality to local children and presented with less advanced infection. However, refugee children from a permanent refugee settlement (n = 110) had more than double the mortality of local children (P < .001), had lower referral rates, and presented more frequently with advanced infection and malnutrition. Distance from the hospital was an important mediator of the association between refugee status and mortality but did not account for all of the increased risk.

CONCLUSIONS

Malaria outcomes were more favorable in refugee children referred from a highly outfitted refugee transit center than those referred later from a permanent refugee settlement. Refugee children experienced higher in-hospital malaria mortality due in part to delayed presentation and higher rates of malnutrition. Interventions tailored to the refugee context are required to ensure capacity for rapid diagnosis and referral to reduce malaria mortality.

Intestinal Injury in Ugandan Children Hospitalized With Malaria

BACKGROUND

Severe malaria is associated with multiple organ dysfunction syndrome (MODS), which may involve the gastrointestinal tract.

METHODS

In a prospective cohort study in Uganda, we measured markers of intestinal injury (intestinal fatty-acid binding protein [I-FABP] and zonula occludens-1 [ZO-1]) and microbial translocation (lipopolysaccharide binding protein [LBP] and soluble complement of differentiation 14 [sCD14]) among children admitted with malaria. We examined their association with biomarkers of inflammation, endothelial activation, clinical signs of hypoperfusion, organ injury, and mortality.

RESULTS

We enrolled 523 children (median age 1.5 years, 46% female, 7.5% mortality). Intestinal FABP was above the normal range (≥400 pg/mL) in 415 of 523 patients (79%). Intestinal FABP correlated with ZO-1 (ρ = 0.11, P = .014), sCD14 (ρ = 0.12, P = .0046) as well as markers of inflammation and endothelial activation. Higher I-FABP levels were associated with lower systolic blood pressure (ρ = -0.14, P = .0015), delayed capillary refill time (ρ = 0.17, P = .00011), higher lactate level (ρ = 0.40, P < .0001), increasing stage of acute kidney injury (ρ = 0.20, P = .0034), and coma (P < .0001). Admission I-FABP levels ≥5.6 ng/mL were associated with a 7.4-fold higher relative risk of in-hospital death (95% confidence interval, 1.4-11, P = .0016).

CONCLUSIONS

Intestinal injury occurs commonly in children hospitalized with malaria and is associated with microbial translocation, systemic inflammation, tissue hypoperfusion, MODS, and fatal outcome.

Severe malaria

Severe malaria is a medical emergency. It is a major cause of preventable childhood death in tropical countries. Severe malaria justifies considerable global investment in malaria control and elimination yet, increasingly, international agencies, funders and policy makers are unfamiliar with it, and so it is overlooked. In sub-Saharan Africa, severe malaria is overdiagnosed in clinical practice. Approximately one third of children diagnosed with severe malaria have another condition, usually sepsis, as the cause of their severe illness. But these children have a high mortality, contributing substantially to the number of deaths attributed to ‘severe malaria’. Simple well-established tests, such as examination of the thin blood smear and the full blood count, improve the specificity of diagnosis and provide prognostic information in severe malaria. They should be performed more widely. Early administration of artesunate and broad-spectrum antibiotics to all children with suspected severe malaria would reduce global malaria mortality.

The Prevalence of Malaria and Bacteremia Co-Infections among Febrile Patients: A Systematic Review and Meta-Analysis

Comprehensive data on the relative contribution of bacteremia to malaria outcomes in a large number of participants are lacking. Therefore, we collated data on the co-existence of malaria and bacteremia in the literature to provide evidence-based information for future studies investigating the clinical significance of this co-infection. The study protocol was registered at PROSPERO (ID: CRD42021287971). Relevant studies were identified from PubMed, Web of Science, and Scopus. The pooled prevalence of (1) co-existent malaria and bacteremia among febrile patients, (2) the pooled prevalence of bacteremia among patients with malaria, (3) the probability of co-infection, and (4) the pooled prevalence of deaths were estimated by the random-effects model. Fifty-one studies involving 1583 cases of co-infection were included in the analyses. Typhoidal Salmonella spp. and Staphylococcus aureus were the most common Gram-negative and Gram-positive bacteria, respectively. The prevalence of co-existent malaria and bacteremia among febrile patients was 1.9% (95% confidence interval (CI) = 1.5–2.2%, I² = 96.64%, 31 studies). The prevalence of bacteremia among patients with malaria was 7.6% (95% CI = 6.7–8.7%, and I² = 96.68%, 43 studies). Co-infection by malaria and bacteremia did not occur by chance (p = 0.024, odds ratio = 0.64, 95% CI = 0.43–0.94, and I² = 95.7%, 29 studies). The pooled prevalence of deaths among patients with co-infection was 15.0% (95% CI = 8.0–23.0%, I² = 75.23%, 8 studies). On the basis of this study, we conclude that although the prevalence of co-infection was low, patients with malaria appear at greater risk of bacteremia and death.

Malaria-induced bacteremia as a consequence of multiple parasite survival strategies

Globally, malaria continues to be an enormous public health burden, with concomitant parasite-induced damage to the gastrointestinal (GI) barrier resulting in bacteremia-associated morbidity and mortality in both adults and children. Infected red blood cells sequester in and can occlude the GI microvasculature, ultimately leading to disruption of the tight and adherens junctions that would normally serve as a physical barrier to translocating enteric bacteria. Mast cell (MC) activation and translocation to the GI during malaria intensifies damage to the physical barrier and weakens the immunological barrier through the release of enzymes and factors that alter the host response to escaped enteric bacteria. In this context, activated MCs release Th2 cytokines, promoting a balanced Th1/Th2 response that increases local and systemic allergic inflammation while protecting the host from overwhelming Th1-mediated immunopathology. Beyond the mammalian host, recent studies in both the lab and field have revealed an association between a Th2-skewed host response and success of parasite transmission to mosquitoes, biology that is evocative of parasite manipulation of the mammalian host. Collectively, these observations suggest that malaria-induced bacteremia may be, in part, an unintended consequence of a Th2-shifted host response that promotes parasite survival and transmission. Future directions of this work include defining the factors and mechanisms that precede the development of bacteremia, which will enable the development of biomarkers to simplify diagnostics, the identification of therapeutic targets to improve patient outcomes and better understanding of the consequences of clinical interventions to transmission blocking strategies.

Prevalence, probability, and outcomes of typhoidal/non-typhoidal Salmonella and malaria co-infection among febrile patients: a systematic review and meta-analysis

The geographical overlaps of malaria parasites and Salmonella spp. can lead to co-infection of these two pathogens, especially in the tropics where malaria is endemic. Moreover, few literatures suggested that malaria infection was associated with Salmonella bacteremia. Therefore, this study quantified pooled prevalence of typhoidal/non-typhoidal Salmonella (NTS) and probability of typhoidal/NTS and malaria co-infection among febrile patients. The systematic review protocol was registered at PROSPERO (CRD42021252322). Studies on co-infection of typhoidal/NTS and malaria were searched in PubMed, Scopus, and Web of Science. The risk of bias of the included studies was assessed using the checklist for analytical cross-sectional studies developed by the Joanna Briggs Institute. Meta-analyses on the following criteria were performed: (1) pooled prevalence of typhoidal/NTS and malaria co-infection among febrile patients, (2) pooled prevalence of typhoidal/NTS among malaria patients, (3) pooled prevalence of malaria infections among patients with Salmonella spp. infection, and (4) probability of typhoidal/NTS and malaria co-infection among febrile patients. Additionally, the case fatality rate and mean difference of malarial parasitemia between typhoidal/NTS and malaria co-infection and Plasmodium monoinfection were also determined. The subgroup analyses of typhoidal/NTS, regions (Africa and Asia), countries, time (publication year), characteristics of participants, and diagnostic tests for identifying Salmonella spp. were also conducted. A sensitivity test was performed to determine the robustness of the study outcomes. Publication bias among the included studies was evaluated using the funnel plot and Egger’s test. All analyses were performed using Stata version 15 (StataCorp LLC, Texas, USA) with a p-value < 0.05 indicating statistical significance. Eighty-one studies that met the eligibility criteria were included in the analyses. Of the 73,775 study participants, 4523 had typhoidal/NTS and malaria co-infections. The pooled prevalence rates of typhoidal/NTS and malaria co-infection among febrile patients were 14% (95% confidence interval [CI], 9–19%; I², 99.4%; 2971/17,720 cases) and 1% (95% CI 1–1%; I², 89.9%; 252/29,081 cases) using the Widal test and culture methods for identifying Salmonella spp., respectively. The pooled prevalence rates of typhoidal/NTS infection among patients with malaria were 31% (95% CI 23–39%; I², 99.5%; 3202/19,208 cases) and 3% (95% CI 2–3%; I², 86.8%; 407/40,426 cases) using the Widal test and culture methods for identifying Salmonella spp., respectively. The pooled prevalence rates of malaria infection among patients with typhoidal/NTS were 17% (95% CI 6–29%; I², 33.3%; 13/75 cases) and 43% (95% CI 32–53%; I², 89.1%; 287/736 cases), respectively. Malaria infection was associated with typhoidal/NTS in children aged < 15 years (p < 0.0001; odds ratio, 0.36; 95% CI 0.23–0.58; I², 73.9%; 3188/43,212 cases). The case fatality rate in patients with malaria and NTS co-infections was 16% (95% CI 9–24%; I², 89.1%; 18/103 cases). From the view of the present study, the inappropriate use of the Widal test for Salmonella spp. diagnosis can overestimate the prevalence of typhoidal/NTS and malaria co-infections. Malaria infection associated with typhoidal/NTS in children and the high case fatality rates among few patients with co-infections were highlighted. Future prospective longitudinal studies using the appropriate and confirmatory dsiagnosis for Salmonella spp. infections are highly recommended to ensure the real prevalence of co-infection and highlight the outcome of co-infection for providing adequate treatment in febrile patients who live in areas where malaria is endemic, such as tropical Africa and India.

Concomitant Bacteremia in Adults With Severe Falciparum Malaria

Background

Approximately 6% of children hospitalized with severe falciparum malaria in Africa are also bacteremic. It is therefore recommended that all children with severe malaria should receive broad-spectrum antibiotics in addition to parenteral artesunate. Empirical antibiotics are not recommended currently for adults with severe malaria.

Methods

Blood cultures were performed on sequential prospectively studied adult patients with strictly defined severe falciparum malaria admitted to a single referral center in Vietnam between 1991 and 2003.

Results

In 845 Vietnamese adults with severe falciparum malaria admission blood cultures were positive in 9 (1.07%: 95% confidence interval [CI], .37–1.76%); Staphylococcus aureus in 2, Streptococcus pyogenes in 1, Salmonella Typhi in 3, Non-typhoid Salmonella in 1, Klebsiella pneumoniae in 1, and Haemophilus influenzae type b in 1. Bacteremic patients presented usually with a combination of jaundice, acute renal failure, and high malaria parasitemia. Four bacteremic patients died compared with 108 (12.9%) of 836 nonbacteremic severe malaria patients (risk ratio, 3.44; 95% CI, 1.62–7.29). In patients with >20% parasitemia the prevalence of concomitant bacteremia was 5.2% (4/76; 95% CI, .2–10.3%) compared with 0.65% (5/769; 0.08–1.2%) in patients with <20% parasitemia, a risk ratio of 8.1 (2.2–29.5).

Conclusions

In contrast to children, the prevalence of concomitant bacteremia in adults with severe malaria is low. Administration of empirical antibiotics, in addition to artesunate, is warranted in the small subgroup of patients with very high parasitemias, emphasizing the importance of quantitative blood smear microscopy assessment, but it is not indicated in most adults with severe falciparum malaria.

Disrupted Iron Metabolism and Mortality during Co-infection with Malaria and an Intestinal Gram-Negative Extracellular Pathogen

Individuals with malaria exhibit increased morbidity and mortality when infected with Gram-negative (Gr−) bacteria. To explore this experimentally, we performed co-infection of mice with Plasmodium chabaudi and Citrobacter rodentium, an extracellular Gr− bacterial pathogen that infects the large intestine. While single infections are controlled effectively, co-infection results in enhanced virulence that is characterized by prolonged systemic bacterial persistence and high mortality. Mortality in co-infected mice is associated with disrupted iron metabolism, elevated levels of plasma heme, and increased mitochondrial reactive oxygen species (ROS) production by phagocytes. In addition, iron acquisition by the bacterium plays a key role in pathogenesis because co-infection with a mutant C. rodentium strain lacking a critical iron acquisition pathway does not cause mortality. These results indicate that disrupted iron metabolism may drive mortality during co-infection with C. rodentium and P. chabaudi by both altering host immune responses and facilitating bacterial persistence.

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Co-infection with malaria and a Gram-negative bacterial pathogen leads to high mortality

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Co-infection leads to elevated plasma heme and systemic bacterial persistence

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Iron acquisition is critical for bacterial persistence and mortality

Predictors of outcome in childhood Plasmodium falciparum malaria

Plasmodium falciparum malaria is classified as either uncomplicated or severe, determining clinical management and providing a framework for understanding pathogenesis. Severe malaria in children is defined by the presence of one or more features associated with adverse outcome, but there is wide variation in the predictive value of these features. Here we review the evidence for the usefulness of these features, alone and in combination, to predict death and other adverse outcomes, and we consider the role that molecular biomarkers may play in augmenting this prediction. We also examine whether a more personalized approach to predicting outcome for specific presenting syndromes of severe malaria, particularly cerebral malaria, has the potential to be more accurate. We note a general need for better external validation in studies of outcome predictors and for the demonstration that predictors can be used to guide clinical management in a way that improves survival and long-term health.

Malaria Case Fatality Rate among Children under Five in Burkina Faso: An Assessment of the Spatiotemporal Trends Following the Implementation of Control Programs

Reducing the 2015 level of malaria mortality by 90% by 2030 is a goal set by the World Health Organization (WHO). In Burkina Faso, several malaria control programs proven to be effective were implemented over the last decade. In parallel, the progressive strengthening of the health surveillance system is generating valuable data, which represents a great opportunity for analyzing the trends in malaria burden and assessing the effect of these control programs. Complementary programs were rolled out at different time points and paces, and the present work aims at investigating both the spatial and temporal pattern of malaria case fatality rate (mCFR) by considering the effect of combining specific and unspecific malaria control programs. To this end, data on severe malaria cases and malaria deaths, aggregated at health district level between January 2013 and December 2018, were extracted from the national health data repository (ENDOS-BF). A Bayesian spatiotemporal zero-inflated Poisson model was fitted to quantify the strength of the association of malaria control programs with monthly mCFR trends at health district level. The model was adjusted for contextual variables. We found that monthly mCFR decreased from 2.0 (95% IC 1.9-2.1%) to 0.9 (95% IC 0.8-1.0%) deaths for 100 severe malaria cases in 2013 and 2018, respectively. Health districts with high mCFR were identified in the northern, northwestern and southwestern parts of the country. The availability of malaria rapid diagnosis tests (IRR: 0.54; CrI: 0.47, 0.62) and treatment (IRR: 0.50; CrI: 0.41, 0.61) were significantly associated with a reduction in the mCFR. The risk of dying from malaria was lower in the period after the free healthcare policy compared with the period before (IRR: 0.47; CrI: 0.38, 0.58). Our findings highlighted locations that are most in need of targeted interventions and the necessity to sustain and strengthen the launched health programs to further reduce the malaria deaths in Burkina Faso.

Malaria

Malaria is a significant cause of morbidity and mortality throughout the world, and environmental changes are likely to increase its importance in the coming years. Diagnosing this disease is difficult and requires a high index of suspicion, especially in non-endemic countries. Critical care providers play a major role in treating severe malaria and its complications, which has management particularities that might not be readily apparent. Fluid resuscitation should be carefully tailored to avoid complications, and dysperfusion seems more related to degree of parasitemia than hypovolemia. Antimalarial agents are effective, but resistance is growing. Complications can be found in nearly every organ, including cerebral malaria, acute respiratory distress syndrome, and acute kidney injury. As such, a critical care unit is frequently required for organ support when they appear. Superimposed infections are not infrequent. Despite all of this, mortality is encouragingly low with a timely diagnosis and access to appropriate treatment.

A randomised controlled trial of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDITOF-MS) versus conventional microbiological methods for identifying pathogens: Impact on optimal antimicrobial therapy of invasive bacterial and fungal infections in Vietnam

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MALDITOF MS provided more rapid identification of invasive bacterial and fungal pathogens than conventional microbiology.

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MALDITOF MS did not increase the proportion of patients on optimal therapy at 24 or 48 hours after positive culture.

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MALDITOF MS did not increase the proportion of patients receiving adequate therapy at 24 hours after positive culture.

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The most common reason for therapy being sub-optimal was use of overly broad spectrum or unnecessary multiple antibiotics.

Objectives

We assessed the impact of MALDITOF-MS on the timeliness of optimal antimicrobial therapy through a parallel-arm randomised controlled trial in two hospitals in Vietnam.

Methods

We recruited patients with a pathogen (bacterial or fungal) cultured from a normally sterile sample. Samples were randomly assigned (1:1) to identification by MALDITOF-MS or conventional diagnostics. The primary outcome was the proportion on optimal antimicrobial therapy within 24 h of positive culture, determined by a blinded independent review committee. Trial registered at ClinicalTrials.gov (NCT02306330).

Results

Among 1005 randomised patients, pathogens were isolated from 628 (326 intervention, 302 control), with 377 excluded as likely contaminants or discharged/died before positive culture. Most isolates were cultured from blood (421/628, 67.0%). The proportion receiving optimal antimicrobial therapy within 24 h (the primary outcome) or 48 h of growth was not significantly different between MALDITOF-MS and control arms (135/326, 41.4% vs 120/302, 39.7%; Adjusted Odds ration (AOR) 1.17, p = 0.40 and 151/326, 46.3% vs 141/302, 46.7%; AOR 1.05 p = 0.79, respectively).

Conclusions

MALDITOF-MS, in the absence of an antimicrobial stewardship programme, did not improve the proportion on optimal antimicrobial therapy at 24 or 48 h after first growth in a lower-middle income setting with high rates of antibiotic resistance.

A biomarker approach to syndrome-based treatment of severe childhood illness in malaria-endemic areas

This opinion article deals with the diagnostic clinical challenges faced by clinicians or health care workers in malaria-endemic areas when a severely sick child presents to the clinic with fever, coma or respiratory distress. Indeed, the coexistence of malaria with other severe infections like meningitis, invasive bacterial infection or pneumonia makes appropriate treatment allocation a matter of life and death. The use of biomarkers has been proposed as a potential solution to this problem. The arrival of high-throughput technologies allowed thousands of molecules (transcripts, proteins and metabolites) to be been screened in clinical samples from large cohorts of well/characterised patients. The major aim of these studies was to identify biomarkers that inform important decisions: should this child be referred to hospital? Should antibiotics, anti-malarials, or both, be administered? There is a large discrepancy between the number of biomarker discovery studies published and the number of biomarkers that have been clinically validated, let alone implemented. This article reflects on the many opportunities and obstacles encountered in biomarker research in malaria-endemic areas.

Antibiotic Therapy in Adults with Malaria (ANTHEM): High Rate of Clinically Significant Bacteremia in Hospitalized Adults Diagnosed with Falciparum Malaria

It has been believed that concomitant bacteremia is uncommon in adults hospitalized with falciparum malaria. Accordingly, the World Health Organization treatment guidelines presently only recommended additional antibacterial therapy in these patients if they have a clinical syndrome compatible with serious bacterial infection. Admission blood cultures were collected from 20 consecutive adults in Myanmar, hospitalized with a positive immunochromatographic test and blood film, suggesting a diagnosis of falciparum malaria; four (20%) had bacteremia with a clinically significant pathogen. These case series' data were pooled with a previously published multicenter study from Myanmar which had also collected blood cultures in adults hospitalized with a diagnosis of falciparum malaria. Among 87 patients in the two studies, 13 (15%) had clinically significant bacteremia on admission, with Gram-negative organisms in 10 (77%) and Staphylococcus aureus in the remaining three (23%). Bacteremic patients had more severe disease than non-bacteremic patients (median [interquartile range] respiratory coma acidosis malaria score 2 [1-4] versus 1 [1-2], P = 0.02) and were more likely to die (2/13 [15%] versus 1/74 [1%], P = 0.01). However, bacterial coinfection was suspected clinically in a minority of bacteremic patients (5/13 [38%] compared with 13/70 [19%] of non-bacteremic patients, P = 0.11). Concomitant bacteremia in adults diagnosed with falciparum malaria may be more common than previously believed and is difficult to identify clinically in resource-poor settings. Death is more common in these patients, suggesting that clinicians should have a lower threshold for commencing empirical antibacterial therapy in adults diagnosed with falciparum malaria in these locations than is presently recommended.

Monocyte dysregulation and systemic inflammation during pediatric falciparum malaria

BACKGROUND

Inflammation and monocytes are thought to be important to human malaria pathogenesis. However, the relationship of inflammation and various monocyte functions to acute malaria, recovery from acute malaria, and asymptomatic parasitemia in endemic populations is poorly understood.

METHODS

We evaluated plasma cytokine levels, monocyte subsets, monocyte functional responses, and monocyte inflammatory transcriptional profiles of 1- to 10-year-old Kenyan children at the time of presentation with acute uncomplicated malaria and at recovery 6 weeks later; these results were compared with analogous data from asymptomatic children and adults in the same community.

RESULTS

Acute malaria was marked by elevated levels of proinflammatory and regulatory cytokines and expansion of the inflammatory "intermediate" monocyte subset that returned to levels of healthy asymptomatic children 6 weeks later. Monocytes displayed activated phenotypes during acute malaria, with changes in surface expression of markers important to innate and adaptive immunity. Functionally, acute malaria monocytes and monocytes from asymptomatic infected children had impaired phagocytosis of P. falciparum-infected erythrocytes relative to asymptomatic children with no blood-stage infection. Monocytes from both acute malaria and recovery time points displayed strong and equivalent cytokine responsiveness to innate immune agonists that were independent of infection status. Monocyte transcriptional profiles revealed regulated and balanced proinflammatory and antiinflammatory and altered phagocytosis gene expression patterns distinct from malaria-naive monocytes.

CONCLUSION

These observations provide insights into monocyte functions and the innate immune response during uncomplicated malaria and suggest that asymptomatic parasitemia in children is not clinically benign.

FUNDING

Support for this work was provided by NIH/National Institute of Allergy and Infectious Diseases (R01AI095192-05), the Burroughs Wellcome Fund/American Society of Tropical Medicine and Hygiene, and the Rainbow Babies & Children's Foundation.

Turf wars: exploring splenomegaly in sickle cell disease in malaria-endemic regions

Sickle cell disease (SCD) is a group of recessively inherited disorders of erythrocyte function that presents an ongoing threat to reducing childhood and adult morbidity and mortality around the world. While decades of research have led to improved survival for SCD patients in wealthy countries, survival remains dismal in low- and middle-income countries. Much of the early mortality associated with SCD is attributed to increased risk of infections due to early loss of splenic function. In the West, bacterial infections with encapsulated organisms are a primary concern. In sub-Saharan Africa, where the majority of infants with SCD are born, the same is true. However malaria presents an additional threat to survival. The search for factors that define variability in sickle cell phenotypes should include environmental modifiers, such as malaria. Further exploration of this relationship could lead to novel strategies to reduce morbidity and mortality attributable to infections. In this review, we explore the interactions between SCD, malaria and the spleen to better understand how splenomegaly and splenic (dys)function may co-exist in patients with SCD living in malaria-endemic areas.

CD4 T-cell expression of IFN-γ and IL-17 in pediatric malarial anemia

In Plasmodium falciparum holoendemic transmission regions of western Kenya, life-threatening pediatric malaria manifests primarily as severe malarial anemia (SMA, Hb≤6.0 g/dL with any density parasitemia). To determine the role that CD4+ T-cell-driven inflammatory responses have in the pathogenesis of SMA, peripheral CD4+ T-cell populations and their intracellular production of pro-inflammatory cytokines (IFN-γ and IL-17) were characterized in children aged 12–36 months of age stratified into two groups: non-severe malarial anemia (non-SMA, Hb≥6.0 g/dL, n = 50) and SMA (n = 39). In addition, circulating IFN-γ and IL-17 were measured as part of a Cytokine 25-plex Antibody Bead Kit, Human (BioSource™ International). Children with SMA had higher overall proportions of circulating lymphocytes (P = 0.003) and elevated proportions of lymphocytes expressing IFN-γ (P = 0.014) and comparable IL-17 (P = 0.101). In addition, SMA was characterized by decreased memory-like T-cells (CD4+CD45RA-) expressing IL-17 (P = 0.009) and lower mean fluorescence intensity in memory-like CD4+ T-cells for both IFN-γ (P = 0.063) and IL-17 (P = 0.006). Circulating concentrations of IFN-γ were higher in children with SMA (P = 0.009), while IL-17 levels were comparable between the groups (P = 0.164). Furthermore, circulating levels of IFN-γ were negatively correlated with IL-17 levels in both groups of children (SMA: r = -0.610, P = 0.007; and non-SMA: r = -0.516, P = 0.001), while production of both cytokines by lymphocytes were positively correlated (SMA: r = 0.349, P = 0.037; and non-SMA: r = 0.475, P = 0.001). In addition, this correlation was only maintained by the memory-like CD4+ T cells (r = 0.365, P = 0.002) but not the naïve-like CD4+ T cells. However, circulating levels of IFN-γ were only associated with naïve-like CD4+ T cells producing IFN-γ (r = 0.547, P = 0.028), while circulating levels of IL-17 were not associated with any of the cell populations. Taken together, these results suggest that enhanced severity of malarial anemia is associated with higher overall levels of circulating lymphocytes, enhanced intracellular production of IFN-γ by peripheral lymphocytes and high circulating IFN-γ levels. In addition, the observed inverse relationship between the circulating levels of IFN-γ and IL-17 together with the reduction in the levels of memory-like CD4+ T cells expressing IL-17 in children with SMA may suggest possible relocation of these cells in the deeper tissues for their pathological effect.

Perspectives on aetiology, pathophysiology and management of shock in African children

Paediatric shock is still a common emergency of public health importance with an estimated 400,000–500,000 reported cases annually. Mortality due to paediatric shock has varied over the years. Data in 1980s show that mortality rates due to septic shock in children were over 50%; but by the end of the year 2000 data indicated that though a marked decline in mortality rates had been achieved, it had stagnated at about 20%. Descriptions of paediatric shock reveal the lack of a common definition and there are important gaps in evidence-based management in different settings. In well-resourced healthcare systems with well-functioning intensive care facilities, the widespread implementation of shock management guidelines based on the Paediatric Advanced Life Support and European Paediatric Advanced Life Support courses have reduced mortality. In resource limited settings with diverse infectious causative agents, the Emergency Triage Assessment and Treatment (ETAT) approach is more pragmatic, but its impact remains circumscribed to centres where ETAT has been implemented and sustained. Advocacy for common management pathways irrespective of underlying cause have been suggested. However, in sub Saharan Africa, the diversity of underlying causative organisms and patient phenotypes may limit a single approach to shock management.

Data from a large fluid trial (the FEAST trial) in East Africa have provided vital insight to shock management. In this trial febrile children with clinical features of impaired perfusion were studied. Rapid infusion of fluid boluses, irrespective of whether the fluid was colloid or crystalloid, when compared to maintenance fluids alone had an increased risk of mortality at 48 h. All study participants were promptly managed for underlying conditions and comorbidity such as malaria, bacteraemia, severe anaemia, meningitis, pneumonia, convulsions, hypoglycaemia and others. The overall low mortality in the trial suggests the potential contribution of ETAT, the improved standard of care and supportive treatment across the subgroups in the trial. Strengthening systems that enable rapid identification of shock, prompt treatment of children with correct antimicrobials and supportive care such as oxygen administration and blood transfusion may contribute to better survival outcomes in resources limited settings.

Hematologic Changes Associated with Specific Infections in the Tropics

Anemia frequently accompanies and plays a minor role in the presentation and course of infection, whether parasitic, bacterial, or viral. However, a variety of infections, many of which are common in Africa and Asia, cause specific hematologic syndromes. The pathophysiology of these syndromes is complex, and to some extent, reduced red cell production may form part of an innate protective host response to infection. Across the world and in endemic areas, malaria is the most important among this group of infections and forms a major part of everyday practice.

Low Bacteremia Prevalence Among Febrile Children in Areas of Differing Malaria Transmission in Rural Kenya: A Cross-Sectional Study

BACKGROUND

With malaria declining, other causes of fever may account for a substantial portion of severe childhood illness in sub-Saharan Africa. We determined prevalence, etiologies, and correlates of bacteremia among children in Western Kenya.

METHODS

In a cross-sectional study, febrile children aged 6 months to 15 years presenting to Kisii (low malaria endemicity) and Homabay (high malaria endemicity) Hospitals were enrolled and screened for malaria, human immunodeficiency virus (HIV) infection and bacteremia. Correlates of bacteremia were evaluated using logistic regression.

RESULTS

Among 1476 children enrolled, 48 (3.3%) had bacteremia (23 of 734, 3.1% in Kisii and 25 of 734, 3.4% in Homabay). Salmonella spp (19 typhi and 21 nontyphoidal salmonella) accounted for 83% (40 of 48) of isolates. The distribution of Salmonella spp was similar between sites. Bacteremia was associated with incomplete vaccination (adjusted odds ratio [aOR] = 2.1; 95% confidence interval [CI], 1.1-4.1), before treatment with antimalarials (aOR = 2.7; 95% CI, 1.4-4.1), having sought care elsewhere (aOR = 2.2; 95% CI, 1.2-4.0) and lower education of caregiver (aOR = 2.5; 95% CI, 1.1-4.8). Nontyphoidal salmonella bacteremia was associated with HIV (aOR = 6.8; 95% CI, 1.1-35.1) and anemia (hemoglobin <8 g/dL) (aOR = 5.2; 95% CI, 1.4-18.9).

CONCLUSIONS

Bacteremia was relatively uncommon, but children with HIV, anemia, incomplete vaccination, and/or persistent fever despite malaria treatment may have higher risk and may benefit from targeted bacterial culture and/or empiric antibiotic therapy.

Evaluating the impact of two training interventions to improve diagnosis and case-management of malaria and pneumonia in Uganda

We present an age-structured mathematical model of malaria and pneumonia to study the effect of two capacity-building interventions: Integrated Management of Infectious Diseases (IMID) and On-site Support Services (OSS). IMID leads to a reduction in malaria prevalence by more than 2·4% across the [0,5), [5,14) and [14,50) age groups. IMID + OSS reduces it by more than 16·0% across all age groups. IMID decreases pneumonia prevalence by more than 3·0% across all age groups while IMID + OSS decreases it by more than 1·0% across all age groups. The number of malaria and pneumonia deaths is reduced by 7·8% by IMID across all age groups and IMID + OSS decreases this number by 30·5% across all age groups, which translates to saving a life of a child per month. Prevalence of malaria-pneumonia for the [0,5) age group is 0·52% at baseline, and IMID and IMID + OSS reduce it by 6·6% and 23·6%, respectively. There is no change in incidence of malaria or pneumonia disease episodes. The results also indicate that triaging of children contributes more than 50% to the effect of the interventions in reduction of deaths and a range of 14-91% in reduction of disease cases.

Pulmonary manifestations of malaria : recognition and management

Lung involvement in malaria has been recognized for more than 200 hundred years, yet our knowledge of its pathogenesis and management is limited. Pulmonary edema is the most severe form of lung involvement. Increased alveolar capillary permeability leading to intravascular fluid loss into the lungs is the main pathophysiologic mechanism. This defines malaria as another cause of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS).Pulmonary edema has been described most often in non-immune individuals with Plasmodium falciparum infections as part of a severe systemic illness or as the main feature of acute malaria. P.vivax and P.ovale have also rarely caused pulmonary edema.Clinically, patients usually present with acute breathlessness that can rapidly progress to respiratory failure either at disease presentation or, interestingly, after treatment when clinical improvement is taking place and the parasitemia is falling. Pregnant women are particularly prone to developing pulmonary edema. Optimal management of malaria-induced ALI/ARDS includes early recognition and diagnosis. Malaria must always be suspected in a returning traveler or a visitor from a malaria-endemic country with an acute febrile illness. Slide microscopy and/or the use of rapid antigen tests are standard diagnostic tools. Malaria must be treated with effective drugs, but current choices are few: e.g. parenteral artemisinins, intravenous quinine or quinidine (in the US only). A recent trial in adults has shown that intravenous artesunate reduces severe malaria mortality by a third compared with adults treated with intravenous quinine. Respiratory compromise should be managed on its merits and may require mechanical ventilation.Patients should be managed in an intensive care unit and particular attention should be paid to the energetic management of other severe malaria complications, notably coma and acute renal failure. ALI/ARDS may also be related to a coincidental bacterial sepsis that may not be clinically obvious. Clinicians should employ a low threshold for starting broad spectrum antibacterials in such patients, after taking pertinent microbiologic specimens. Despite optimal management, the prognosis of severe malaria with ARDS is poor.ALI/ARDS in pediatric malaria appears to be rare. However, falciparum malaria with severe metabolic acidosis or acute pulmonary edema may present with a clinical picture of pneumonia, i.e. with tachypnea, intercostal recession, wheeze or inspiratory crepitations. This results in diagnostic confusion and suboptimal treatment. Whilst this is increasingly being recognized in malaria-endemic countries, clinicians in temperate zones should be aware that malaria may be a possible cause of 'pneumonia' in a visiting or returning child.

Exploring health practitioners' acceptability of a prospective semi-quantitative pfHRP2 device to define severe malaria in the Democratic Republic of Congo

BACKGROUND

A rapid diagnostic tool is being developed to discern severely ill children with severe malaria from children who are ill with alternative febrile diseases but have coincidental peripheral blood parasitaemia. The device semi-quantitatively measures plasma pfHRP2 and has the potential to reduce mortality in children with severe febrile illnesses by improving diagnosis. The aim of this study is to identify contributing and inhibiting factors that affect healthcare practitioners' acceptability of this prospective diagnostic device in a high malaria transmission setting in the Democratic Republic of Congo.

METHODS

Data were collected qualitatively by conducting semi-structured interviews with a purposeful sample of health professionals in Kinshasa, capital of Democratic Republic of Congo. In total, 11 interviews were held with professionals at four different institutes.

RESULTS

Four key findings emerged: (1) Congolese practitioners perceive the semi-quantitative pfHRP2 device as a welcome intervention as they recognize the limited reliability of their current diagnostic and therapeutic approaches to severe febrile illnesses; (2) compatibility of the semi-quantitative pfHRP2 device with clinical equipment and competences of Congolese health practitioners is considered to be limited, especially in rural settings; (3) a formal training programme is crucial for correct understanding and application of the semi-quantitative pfHRP2 device; and, (4) provision of evidence to practitioners, and support from health authorities would be important to establish confidence in the semi-quantitative pfHRP2 device.

CONCLUSIONS

Congolese practitioners perceive the prospective semi-quantitative pfHRP2 device as a welcome addition to their clinical equipment. The device could improve current diagnostic work-up of severe febrile illness, which might consequently improve treatment choices. However, despite this recognized potential, several hurdles and drivers need to be taken into account when implementing this device in DR Congo.

Clinical Profile and Prognostic Indicators in Adults Hospitalized with Severe Malaria Caused by Different Plasmodium Species

INTRODUCTION

Severe malaria remains a major cause of death and morbidity among adults in the Asiatic tropics. This study was planned to evaluate clinical profile and prognostic indicators of severe malaria in adults so as to improve insight into this highly prevalent disease.

MATERIALS AND METHODS

This prospective observational study was conducted on 60 confirmed cases of malaria. Cases were divided into two groups: (a) study group: suffering from severe malaria and (b) control group: no severe manifestations. All cases were thoroughly studied for clinical features, laboratory evaluation, and outcome. Prognostic evaluation was also done by different score systems.

RESULTS

In all, 40 cases suffer from severe malaria (study group), while 20 cases belong to the control group. The majority of our cases were males of age 21-40 years. The most common species of malaria in the study group was vivax (52.5%), followed by falciparum (25%) and mixed malaria species (22.5%). The clinical predictors for severe malaria were rural habitat, longer duration of fever, marked chills, tiredness, giddiness, nausea, vomiting, decreased urine output, jaundice, and altered sensorium. Extreme weakness (80%), jaundice (55%), renal failure (50%), and severe anemia (27.5%) were the most common presenting features in severe malaria. Two patients died of severe mixed malaria. The mortality rate was significantly associated with lower hemoglobin level (P = 0.002); higher total leukocyte count (P = 0.006), blood urea (P < 0.001), serum creatinine (P < 0.001), SGOT (P = 0.001), SGPT (P < 0.007), serum bilirubin (P = 0.003), and parasite density (P = 0.033); lower platelet count (P = 0.043); and those who had more APACHE II score (P = 0.003), SOFA score (P = 0.04), and Multiple Organ Dysfunction Score (P < 0.001) and lower Glasgow Coma Scale (P < 0.001).

CONCLUSIONS

Manifestations of severe malaria is becoming increasingly more prevalent specifically in vivax and mixed malaria cases. Our study proposes that there are certain clinical predictors and prognostic indicators that should be kept in mind for better management of severe malaria.

Malaria Diagnosis Using Automated Analysers: A Boon for Hematopathologists in Endemic Areas

BACKGROUND

Haematological abnormalities are common in acute febrile tropical illnesses. Malaria is a major health problem in tropics. In endemic areas especially in the post monsoon season, it is not practical to manually screen all peripheral blood films (PBF) for malarial parasite. Automated analysers offer rapid, sensitive and cost effective screening of all samples.

AIM

The study was done to evaluate the usefulness of automated cell counters analysing their histograms, scatter-grams and the flaggings generated in malaria positive and negative cases. The comparison of other haematological parameters were also studied which could help to identify malaria parasite in peripheral blood smear.

MATERIALS AND METHODS

The blood samples were analysed using Beckman coulter LH-750. The abnormal scatter grams and additional peaks in WBC histograms were observed diligently & compared with normal controls. Haematological abnormalities were also evaluated.

STATISTICAL ANALYSIS

Statistical analysis was done by using software Epi-Info version 7.1.4 freely available from CDC website. Fisher exact test was applied to calculate the p-value and value < 0.05 was considered as significant. Final identification of malarial parasite species was done independently by peripheral blood smear examination by two pathologists.

RESULTS

Of all the 200 cases evaluated abnormal scatter grams were observed in all the cases of malaria while abnormal WBC histogram peaks were noted in 96% cases demonstrating a peak at the threshold of the histogram. The difference between number of slides positive for abnormal WBC scatter gram and abnormal WBC histogram peaks were statistically highly significant (p=0.007). So abnormal WBC scatter gram can better give idea of malarial parasite presence. Of the haematological parameters thrombocytopenia (92% cases) emerged as the strongest predictor of malaria.

CONCLUSION

It is recommended for haematopathologists to review the haematological data and the scatter plots on the analyser along with peripheral blood smear examination.

The malaria co-infection challenge: An investigation into the antimicrobial activity of selected Guinean medicinal plants

ETHNOPHARMACOLOGICAL RELEVANCE

In sub-Saharan Africa, concomitant occurrence of malaria and invasive infections with micro-organisms such as Gram-positive Staphylococcus aureus, Gram-negative Escherichia coli and yeasts or fungi such as Candida albicans and Aspergillus fumigatus is common. Non-tuberculous mycobacteriosis caused by Mycobacterium chelonae has been recognized as a pulmonary pathogen with increasing frequency without effective therapy. Although less important, the high incidence of Trichophyton rubrum infections along with its ability to evade host defense mechanisms, accounts for the high prevalence of infections with this dermatophyte. Considering the treatment cost of both malaria and microbial infections, along with the level of poverty, most affected African countries are unable to cope with the burden of these diseases. In sub-Saharan Africa, many plant species are widely used in the treatment of these diseases which are traditionally diagnosed through the common symptom of fever. Therefore it is of interest to evaluate the antimicrobial activities of medicinal plants reported for their use against malaria/fever.

MATERIALS AND METHODS

Based on an ethnobotanical survey, 34 Guinean plant species widely used in the traditional treatment of fever and/or malaria have been collected and evaluated for their antimicrobial activities. Plants extracts were tested against Candida albicans, Trichophyton rubrum, Aspergillus fumigatus, Mycobacterium chelonae, Staphylococcus aureus and Escherichia coli.

RESULTS

The most interesting activities against Candida albicans were obtained for the polar extracts of Pseudospondias microcarpa and Ximenia americana with IC50 values of 6.99 and 8.12 µg/ml, respectively. The most pronounced activity against Trichophyton rubrum was obtained for the ethanol extract of Terminalia macroptera (IC50 5.59 µg/ml). Only 7 of the 51 tested extracts were active against Staphylococcus aureus. From these, the methanolic extracts of the leaves and stem bark of Alchornea cordifolia were the most active with IC50 values of 2.81 and 7.47 µg/ml, respectively. Only Terminalia albida and Lawsonia inermis showed activity against Mycobacterium chelonae. None of the tested extracts was active against Escherichia coli.

CONCLUSION

A number of traditional Guinean plant species used against malaria/fever showed, in addition to their antiplasmodial properties and antimicrobial activity. The fact that some plant species are involved in the traditional treatment of malaria/fever without any antiplasmodial evidence may be justified by their antimicrobial activities.

A case of an avoidable admission to an Ebola treatment unit with malaria and an associated heat illness

We present a 27-year old British nurse admitted to the Kerry Town Ebola Treatment Unit, Sierra Leone, with symptoms fitting suspect-Ebola virus disease (EVD) case criteria. A diagnosis of Plasmodium falciparum malaria and heat illness was ultimately made, both of which could have been prevented through employing simple measures not utilised in this case. The dual pathology of her presentation was atypical for either disease meaning EVD could not be immediately excluded. She remained isolated in the red zone until 72 h from symptom onset. This case highlights why force protection measures are important to reduce the incidence of both malaria and heat illness in deployed military and civilian populations. These prevention measures are particularly pertinent during the current EVD epidemic where presenting with these pathologies requires clinical assessment in the 'red zone' of an Ebola treatment unit.

Acute respiratory infection and bacteraemia as causes of non-malarial febrile illness in African children: a narrative review

The replacement of "presumptive treatment for malaria" by "test before treat" strategies for the management of febrile illness is raising awareness of the importance of knowing more about the causes of illness in children who are suspected to have malaria but return a negative parasitological test. The most common cause of non-malarial febrile illness (NMFI) in African children is respiratory tract infection. Whilst the bacterial causes of NMFI are well known, the increasing use of sensitive techniques such as polymerase chain reaction (PCR) tests is revealing large numbers of viruses that are potential respiratory pathogens. However, many of these organisms are commonly present in the respiratory tract of healthy children so causality and risk factors for pneumonia remain poorly understood. Infection with a combination of viral and bacterial pathogens is increasingly recognised as important in the pathogenesis of pneumonia. Similarly, blood stream infections with organisms typically grown by aerobic culture are well known but a growing number of organisms that can be identified only by PCR, viral culture, or serology are now recognised to be common pathogens in African children. The high mortality of hospitalised children on the first or second day of admission suggests that, unless results are rapidly available, diagnostic tests to identify specific causes of illness will still be of limited use in guiding the potentially life saving decisions relating to initial treatment of children admitted to district hospitals in Africa with severe febrile illness and a negative test for malaria. Malaria control and the introduction of vaccines against Haemophilus influenzae type b and pneumococcal disease are contributing to improved child survival in Africa. However, increased parasitological testing for malaria is associated with increased use of antibiotics to which resistance is already high.

Antimalarial activity of tulathromycin in a murine model of malaria

There is an urgent need for new antimalarial agents and strategies to treat and control malaria. This study shows an antiplasmodium effect of tulathromycin in mice infected with Plasmodium yoelii. The administration of tulathromycin around the time of infection prevented the progression of disease in 100% of the animals. In addition, highly parasitized mice treated with tulathromycin showed a decreased parasite burden and cleared the parasite faster than did untreated infected mice.

The pathogenesis of pediatric cerebral malaria: eye exams, autopsies, and neuroimaging

Several advances in our understanding of pediatric cerebral malaria (CM) have been made over the past 25 years. Accurate clinical diagnosis is enhanced by the identification of a characteristic retinopathy, visible by direct or indirect ophthalmoscopy, the retinal changes (retinal whitening, vessel color changes, white-centered hemorrhages) being consistently associated with intracerebral sequestration of parasites in autopsy studies. Autopsies have yielded information at tissue levels in fatal CM, but new insights into critical pathogenetic processes have emerged from neuroimaging studies, which, unlike autopsy-based studies, permit serial observations over time and allow comparisons between fatal cases and survivors. Brain swelling has emerged as the major risk factor for death, and, among survivors, brain volume diminishes spontaneously over 24-48 hours. Studies of life-threatening and fatal malaria are suggesting new approaches to identifying and caring for those at highest risk; potential adjuvants should be evaluated and implemented where they are most needed.

Parasite biomass-related inflammation, endothelial activation, microvascular dysfunction and disease severity in vivax malaria

Plasmodium vivax can cause severe malaria, however its pathogenesis is poorly understood. In contrast to P. falciparum, circulating vivax parasitemia is low, with minimal apparent sequestration in endothelium-lined microvasculature, and pathogenesis thought unrelated to parasite biomass. However, the relationships between vivax disease-severity and total parasite biomass, endothelial autocrine activation and microvascular dysfunction are unknown. We measured circulating parasitemia and markers of total parasite biomass (plasma parasite lactate dehydrogenase [pLDH] and PvLDH) in adults with severe (n = 9) and non-severe (n = 53) vivax malaria, and examined relationships with disease-severity, endothelial activation, and microvascular function. Healthy controls and adults with non-severe and severe falciparum malaria were enrolled for comparison. Median peripheral parasitemia, PvLDH and pLDH were 2.4-fold, 3.7-fold and 6.9-fold higher in severe compared to non-severe vivax malaria (p = 0.02, p = 0.02 and p = 0.015, respectively), suggesting that, as in falciparum malaria, peripheral P. vivax parasitemia underestimates total parasite biomass, particularly in severe disease. P. vivax schizonts were under-represented in peripheral blood. Severe vivax malaria was associated with increased angiopoietin-2 and impaired microvascular reactivity. Peripheral vivax parasitemia correlated with endothelial activation (angiopoietin-2, von-Willebrand-Factor [VWF], E-selectin), whereas markers of total vivax biomass correlated only with systemic inflammation (IL-6, IL-10). Activity of the VWF-cleaving-protease, ADAMTS13, was deficient in proportion to endothelial activation, IL-6, thrombocytopenia and vivax disease-severity, and associated with impaired microvascular reactivity in severe disease. Impaired microvascular reactivity correlated with lactate in severe vivax malaria. Findings suggest that tissue accumulation of P. vivax may occur, with the hidden biomass greatest in severe disease and capable of mediating systemic inflammatory pathology. The lack of association between total parasite biomass and endothelial activation is consistent with accumulation in parts of the circulation devoid of endothelium. Endothelial activation, associated with circulating parasites, and systemic inflammation may contribute to pathology in vivax malaria, with microvascular dysfunction likely contributing to impaired tissue perfusion.

Plasmodium suppresses expansion of T cell responses to heterologous infections

Plasmodium remains a major pathogen causing malaria and impairing defense against other infections. Defining how Plasmodium increases susceptibility to heterologous pathogens may lead to interventions that mitigate the severity of coinfections. Previous studies proposed that reduced T cell responses during coinfections are due to diminished recruitment of naive T cells through infection-induced decreases in chemokine CCL21. We found that, although Listeria infections reduced expression of CCL21 in murine spleens, lymphocytic choriomeningitis virus (LCMV)-specific T cell responses were not impaired during Listeria + LCMV coinfection, arguing against a major role for this chemokine in coinfection-induced T cell suppression. In our experiments, Plasmodium yoelii infection led to a reduced CD8(+) T cell response to a subsequent Listeria infection. We propose an alternative mechanism whereby P. yoelii suppresses Listeria-specific T cell responses. We found that Listeria-specific T cells expanded more slowly and resulted in lower numbers in response to coinfection with P. yoelii. Mathematical modeling and experimentation revealed greater apoptosis of Listeria-specific effector T cells as the main mechanism, because P. yoelii infections did not suppress the recruitment or proliferation rates of Listeria-specific T cells. Our results suggest that P. yoelii infections suppress immunity to Listeria by causing increased apoptosis in Listeria-specific T cells, resulting in a slower expansion rate of T cell responses.

Innate sensing of malaria parasites

Innate immune receptors have a key role in immune surveillance by sensing microorganisms and initiating protective immune responses. However, the innate immune system is a classic 'double-edged sword' that can overreact to pathogens, which can have deleterious effects and lead to clinical manifestations. Recent studies have unveiled the complexity of innate immune receptors that function as sensors of Plasmodium spp. in the vertebrate host. This Review highlights the cellular and molecular mechanisms by which Plasmodium infection is sensed by different families of innate immune receptors. We also discuss how these events mediate both host resistance to infection and the pathogenesis of malaria.

The association between malaria and non-typhoid Salmonella bacteraemia in children in sub-Saharan Africa: a literature review

Plasmodium falciparum malaria and non-typhoid Salmonella (NTS) bacteraemia are both major causes of morbidity and mortality in children in sub-Saharan Africa. Co-infections are expected to occur because of their overlapping geographical distribution, but accumulating evidence indicates that malaria is a risk factor for NTS bacteraemia. A literature review was undertaken to provide an overview of the evidence available for this association, the epidemiology of malaria-NTS co-infection (including the highest risk groups), the underlying mechanisms, and the clinical consequences of this association, in children in sub-Saharan Africa. The burden of malaria-NTS co-infection is highest in young children (especially those less than three years old). Malaria is one of the risk factors for NTS bacteraemia in children, and the risk is higher with severe malaria, especially severe malarial anaemia. There is insufficient evidence to determine whether asymptomatic parasitaemia is a risk factor for NTS bacteraemia. Many mechanisms have been proposed to explain how malaria causes susceptibility to NTS, ranging from macrophage dysfunction to increased gut permeability, but the most consistent evidence is that malarial haemolysis creates conditions which favour bacterial growth, by increasing iron availability and by impairing neutrophil function. Few discriminatory clinical features have been described for those with malaria and NTS co-infection, except for a higher risk of anaemia compared to those with either infection alone. Children with malaria and NTS bacteraemia co-infection have higher case fatality rates compared to those with malaria alone, and similar to those with bacteraemia alone. Antimicrobial resistance is becoming widespread in invasive NTS serotypes, making empirical treatment problematic, and increasing the need for prevention measures. Observational studies indicate that interventions to reduce malaria transmission might also have a substantial impact on decreasing the incidence of NTS bacteraemia.

Managing malaria in the intensive care unit

The number of people travelling to malaria-endemic countries continues to increase, and malaria remains the commonest cause of serious imported infection in non-endemic areas. Severe malaria, mostly caused by Plasmodium falciparum, often requires intensive care unit (ICU) admission and can be complicated by cerebral malaria, respiratory distress, acute kidney injury, bleeding complications, and co-infection. The mortality from imported malaria remains significant. This article reviews the manifestations, complications and principles of management of severe malaria as relevant to critical care clinicians, incorporating recent studies of anti-malarial and adjunctive treatment. Effective management of severe malaria includes prompt diagnosis and early institution of effective anti-malarial therapy, recognition of complications, and appropriate supportive management in an ICU. All cases should be discussed with a specialist unit and transfer of the patient considered.

Transfusion of stored blood impairs host defenses against Gram-negative pathogens in mice

BACKGROUND

Although human red blood cell (RBC) units may be refrigerator stored for up to 42 days, transfusion of older RBCs acutely delivers a large bolus of iron to mononuclear phagocytes. Similarly, iron dextran circulates in plasma for hours to days and is progressively cleared by mononuclear phagocytes, which return iron to plasma. Finally, malaria infection continuously delivers iron to macrophages by intra- and extravascular hemolysis. Studies suggest that iron administration increases infectious risk.

STUDY DESIGN AND METHODS

To assess the effects of increased iron availability on susceptibility to infection, we infected mice with model Gram-negative intracellular or extracellular pathogens (Salmonella typhimurium or Escherichia coli, respectively), accompanied by RBC transfusion, iron dextran administration, or malarial coinfection.

RESULTS

In our mouse models, transfusion of older RBCs exacerbates infection with both Gram-negative pathogens. Although iron dextran exacerbates E. coli infection to a similar extent as transfusion of corresponding amounts of iron, higher iron doses are required to produce comparable effects with S. typhimurium. Coinfection of mice with Plasmodium yoelii and S. typhimurium produces overwhelming Salmonella sepsis. Finally, treating mice with antibiotics abrogates the enhancing effect on E. coli infection of both older RBC transfusion and iron dextran administration.

CONCLUSIONS

Transfusion of older RBCs exacerbates Gram-negative infection to a similar extent as malaria coinfection or iron dextran administration. Appropriate antibiotic therapy abrogates the effect of older RBC transfusions on infection with E. coli. Iron delivery to macrophages may be an underappreciated mechanism mediating, at least some, adverse effects of RBC transfusions.

Comparison of an assumed versus measured leucocyte count in parasite density calculations in Papua New Guinean children with uncomplicated malaria

BACKGROUND

The accuracy of the World Health Organization method of estimating malaria parasite density from thick blood smears by assuming a white blood cell (WBC) count of 8,000/μL has been questioned in several studies. Since epidemiological investigations, anti-malarial efficacy trials and routine laboratory reporting in Papua New Guinea (PNG) have all relied on this approach, its validity was assessed as part of a trial of artemisinin-based combination therapy, which included blood smear microscopy and automated measurement of leucocyte densities on Days 0, 3 and 7.

RESULTS

168 children with uncomplicated malaria (median (inter-quartile range) age 44 (39-47) months) were enrolled, 80.3% with Plasmodium falciparum monoinfection, 14.9% with Plasmodium vivax monoinfection, and 4.8% with mixed P. falciparum/P. vivax infection. All responded to allocated therapy and none had a malaria-positive slide on Day 3. Consistent with a median baseline WBC density of 7.3 (6.5-7.8) × 10(9)/L, there was no significant difference in baseline parasite density between the two methods regardless of Plasmodium species. Bland Altman plots showed that, for both species, the mean difference between paired parasite densities calculated from assumed and measured WBC densities was close to zero. At parasite densities <10,000/μL by measured WBC, almost all between-method differences were within the 95% limits of agreement. Above this range, there was increasing scatter but no systematic bias.

CONCLUSIONS

Diagnostic thresholds and parasite clearance assessment in most PNG children with uncomplicated malaria are relatively robust, but accurate estimates of a higher parasitaemia, as a prognostic index, requires formal WBC measurement.

Discovery and validation of biomarkers to guide clinical management of pneumonia in African children

Lipocalin 2 distinguishes severe and bacterial pneumonia from nonsevere and nonbacterial pneumonia with a high level of precision. The clinical impact of this biomarker requires large-scale clinical evaluation.

Background. Pneumonia is the leading cause of death in children globally. Clinical algorithms remain suboptimal for distinguishing severe pneumonia from other causes of respiratory distress such as malaria or distinguishing bacterial pneumonia and pneumonia from others causes, such as viruses. Molecular tools could improve diagnosis and management.

Methods. We conducted a mass spectrometry–based proteomic study to identify and validate markers of severity in 390 Gambian children with pneumonia (n = 204) and age-, sex-, and neighborhood-matched controls (n = 186). Independent validation was conducted in 293 Kenyan children with respiratory distress (238 with pneumonia, 41 with Plasmodium falciparum malaria, and 14 with both). Predictive value was estimated by the area under the receiver operating characteristic curve (AUC).

Results. Lipocalin 2 (Lpc-2) was the best protein biomarker of severe pneumonia (AUC, 0.71 [95% confidence interval, .64–.79]) and highly predictive of bacteremia (78% [64%–92%]), pneumococcal bacteremia (84% [71%–98%]), and “probable bacterial etiology” (91% [84%–98%]). These results were validated in Kenyan children with severe malaria and respiratory distress who also met the World Health Organization definition of pneumonia. The combination of Lpc-2 and haptoglobin distinguished bacterial versus malaria origin of respiratory distress with high sensitivity and specificity in Gambian children (AUC, 99% [95% confidence interval, 99%–100%]) and Kenyan children (82% [74%–91%]).

Conclusions. Lpc-2 and haptoglobin can help discriminate the etiology of clinically defined pneumonia and could be used to improve clinical management. These biomarkers should be further evaluated in prospective clinical studies.

Imported falciparum malaria among adults requiring intensive care: analysis of the literature

Background

Malaria is the most important imported tropical disease. Infection with Plasmodium falciparum is responsible for most of the morbidity and mortality. There are differences in both the epidemiology of imported malaria and in the facilities available to treat travellers with severe malaria between different parts of the world. There are limited data to guide clinicians caring for adults with imported malaria in an intensive care unit (ICU). Available data from the English-speaking literature concerning such patients was reviewed.

Methods

PubMed was searched for studies on adults with imported malaria treated in an ICU. Data were extracted on the epidemiology, management, rates of concomitant community-acquired bacterial infection and outcomes.

Results

Thirteen studies were identified, which between them included 1,001 patients over more than 40 years. Forty-one per cent were born and often still resident in an endemic country and were assumed to have at least partial immunity to the disease. Acute kidney injury (AKI) (36%), acute respiratory distress syndrome (ARDS) (31%) and impaired consciousness (25%) were common. Hyperparasitaemia (more than 2%) was seen in 57%. Thirty-four per cent required mechanical ventilation and 22% required renal replacement therapy. Community-acquired bacterial co-infection was seen in 8%; 2% had gram-negative bacteraemia at admission. Overall the case fatality rate was 9%.

Conclusions

Many patients who require admission to ICU were originally from malaria-endemic countries and many did not have hyperparasitaemia. Gram-negative bacteraemia was uncommon among adults with severe malaria. The case fatality rate remains high; however, improvements in ICU care and increasing use of artemisinins may reduce this in the future.

Correlates of inappropriate prescribing of antibiotics to patients with malaria in Uganda

Background

In many rural areas of Uganda, febrile patients presenting to health facilities are prescribed both antimalarials and antibiotics, contributing to the overuse of antibiotics. We identified the prevalence and correlates of inappropriate antibiotic management of patients with confirmed malaria.

Methods

We utilized individual outpatient data from 36 health centers from January to September 2011. We identified patients who were prescribed antibiotics without an appropriate clinical indication, as well as patients who were not prescribed antibiotics when treatment was clinically indicated. Multivariate logistic regression models were used to identify clinical and operational factors associated with inappropriate case management.

Findings

Of the 45,591 patients with parasitological diagnosis of malaria, 40,870 (90%) did not have a clinical indication for antibiotic treatment. Within this group, 17,152 (42%) were inappropriately prescribed antibiotics. The odds of inappropriate prescribing were higher if the patient was less than five years old (aOR 1.96, 95% CI 1.75–2.19) and if the health provider had the fewest years of training (aOR 1.86, 95% CI 1.05–3.29). The odds of inappropriate prescribing were lower if patients had emergency triage status (aOR 0.75, 95% CI 0.59–0.96) or were HIV positive (aOR 0.31, 95% CI 0.20–0.45). Of the 4,721 (10%) patients with clinical indications for antibiotic treatment, 521 (11%) were inappropriately not prescribed antibiotics. Clinical officers were less likely than medical officers to inappropriately withhold antibiotics (aOR 0.54, 95% CI 0.29–0.98).

Conclusion

Over 40% of the antibiotic treatment in malaria positive patients is prescribed despite a lack of documented clinical indication. In addition, over 10% of patients with malaria and a clinical indication for antibiotics do not receive them. These findings should inform facility-level trainings and interventions to optimize patient care and slow trends of rising antibiotic resistance.

Invasive bacterial co-infection in African children with Plasmodium falciparum malaria: a systematic review

BACKGROUND

Severe malaria remains a major cause of pediatric hospital admission across Africa. Invasive bacterial infection (IBI) is a recognized complication of Plasmodium falciparum malaria, resulting in a substantially worse outcome. Whether a biological relationship exists between malaria infection and IBI susceptibility remains unclear. We, therefore, examined the extent, nature and evidence of this association.

METHODS

We conducted a systematic search in August 2012 of three major scientific databases, PubMed, Embase and Africa Wide Information, for articles describing bacterial infection among children with P. falciparum malaria using the search string '(malaria OR plasmodium) AND (bacteria OR bacterial OR bacteremia OR bacteraemia OR sepsis OR septicaemia OR septicemia).' Eligiblity criteria also included studies of children hospitalized with malaria or outpatient attendances in sub-Saharan Africa.

RESULTS

A total of 25 studies across 11 African countries fulfilled our criteria. They comprised twenty cohort analyses, two randomized controlled trials and three prospective epidemiological studies. In the meta-analysis of 7,208 children with severe malaria the mean prevalence of IBI was 6.4% (95% confidence interval (CI) 5.81 to 6.98%). In a further meta-analysis of 20,889 children hospitalised with all-severity malaria and 27,641 children with non-malarial febrile illness the mean prevalence of IBI was 5.58 (95% CI 5.5 to 5.66%) in children with malaria and 7.77% (95% CI 7.72 to 7.83%) in non-malaria illness. Ten studies reported mortality stratified by IBI. Case fatality was higher at 81 of 336, 24.1% (95% CI 18.9 to 29.4) in children with malaria/IBI co-infection compared to 585 of 5,760, 10.2% (95% CI 9.3 to 10.98) with malaria alone. Enteric gram-negative organisms were over-represented in malaria cases, non-typhoidal Salmonellae being the most commonest isolate. There was weak evidence indicating IBI was more common in the severe anemia manifestation of severe malaria.

CONCLUSIONS

The accumulated evidence suggests that children with recent or acute malaria are at risk of bacterial infection, which results in an increased risk of mortality. Characterising the exact nature of this association is challenging due to the paucity of appropriate severity-matched controls and the heterogeneous data. Further research to define those at greatest risk is necessary to target antimicrobial treatment.

Hemozoin inhibition and control of clinical malaria

Malaria has a negative impact on health and social and economic life of residents of endemic countries. The ultimate goals of designing new treatment for malaria are to prevent clinical infection, reduce morbidity, and decrease mortality. There are great advances in the understanding of the parasite-host interaction through studies by various scientists. In some of these studies, attempts were made to evaluate the roles of malaria pigment or toxins in the pathogenesis of malaria. Hemozoin is a key metabolite associated with severe malaria anemia (SMA), immunosuppression, and cytokine dysfunction. Targeting of this pigment may be necessary in the design of new therapeutic products against malaria. In this review, the roles of hemozoin in the morbidity and mortality of malaria are highlighted as an essential target in the quest for effective control of clinical malaria.

Clinical features and outcome in children with severe Plasmodium falciparum malaria: a meta-analysis

Background

Although global malaria mortality is declining, estimates may not reflect better inpatient management of severe malaria (SM) where reported case fatality rates (CFRs) vary from 1–25%.

Methods

A meta-analysis of prospective studies of SM was conducted to examine i) whether hypothesized differences between clinical features and outcome in Melanesian compared with African or Asian children really exist, and ii) to explore temporal changes in overall and complication-specific CFRs. The proportions of different SM complications and, overall and complication-specific CFRs were incorporated into the meta-analysis. Adjustments were made for study-level covariates including geographic region, SM definition, artemisinin treatment, median age of participants and time period.

Findings

Sixty-five studies were included. Substantial heterogeneity (I²>80%) was demonstrated for most outcomes. SM definition contributed to between-study heterogeneity in proportions of cerebral malaria (CM), metabolic acidosis (MA), severe anemia and overall CFR, whilst geographic region was a significant moderator in for CM and hypoglycemia (HG) rates. Compared with their African counterparts, Melanesian children had lower rates of HG (10% [CI95 7–13%] versus 1% [0–3%], P<0.05), lower overall CFR (2% [0–4%] versus 7% [6–9%], P<0.05) and lower CM-specific CFR (8% [0–17%] versus 19% [16–21%], P<0.05). There was no temporal trend for overall CFR and CM-specific CFR but declining HG- and MA- specific CFRs were observed.

Interpretation

These data highlight that recent estimates of declining global malaria mortality are not replicated by improved outcomes for children hospitalized with SM. Significant geographic differences in the complication rates and subsequent CFRs exist and provide the first robust confirmation of lower CFRs in Melanesian children, perhaps due to less frequent HG.

Invasive Salmonella infections in areas of high and low malaria transmission intensity in Tanzania

BACKGROUND

 The epidemiology of Salmonella Typhi and invasive nontyphoidal Salmonella (NTS) differs, and prevalence of these pathogens among children in sub-Saharan Africa may vary in relation to malaria transmission intensity.

METHODS

 We compared the prevalence of bacteremia among febrile pediatric inpatients aged 2 months to 13 years recruited at sites of high and low malaria endemicity in Tanzania. Enrollment at Teule Hospital, the high malaria transmission site, was from June 2006 through May 2007, and at Kilimanjaro Christian Medical Centre (KCMC), the low malaria transmission site, from September 2007 through August 2008. Automated blood culture, malaria microscopy with Giemsa-stained blood films, and human immunodeficiency virus testing were performed.

RESULTS

 At Teule, 3639 children were enrolled compared to 467 at KCMC. Smear-positive malaria was detected in 2195 of 3639 (60.3%) children at Teule and 11 of 460 (2.4%) at KCMC (P < .001). Bacteremia was present in 336 of 3639 (9.2%) children at Teule and 20 of 463 (4.3%) at KCMC (P < .001). NTS was isolated in 162 of 3639 (4.5%) children at Teule and 1 of 463 (0.2%) at KCMC (P < .001). Salmonella Typhi was isolated from 11 (0.3%) children at Teule and 6 (1.3%) at KCMC (P = .008). With NTS excluded, the prevalence of bacteremia at Teule was 5.0% and at KCMC 4.1% (P = .391).

CONCLUSIONS

 Where malaria transmission was intense, invasive NTS was common and Salmonella Typhi was uncommon, whereas the inverse was observed at a low malaria transmission site. The relationship between these pathogens, the environment, and the host is a compelling area for further research.

Severe malaria in Battambang Referral Hospital, an area of multidrug resistance in Western-Cambodia: a retrospective analysis of cases from 2006-2009

BACKGROUND

Despite recent malaria containment and control efforts leading to reduced incidence, Cambodia remains endemic for both Plasmodium vivax and multidrug-resistant Plasmodium falciparum malaria. Little has been reported in the peer-reviewed literature regarding the burden of severe malaria (SM) in Cambodia.

METHODS

Medical records for all patients admitted to the Battambang Referral Hospital (BRH) with an admitting or discharge diagnosis of SM from 2006 to 2009 (suspected SM cases) were reviewed. Those meeting the case definition of SM according to retrospective chart review and investigator assessment of probable cases, based on published national guidelines available at the time, were analysed for trends in demographics, mortality and referral patterns.

RESULTS

Of the 537 suspected SM cases at BRH during the study period, 393 (73%) met published WHO criteria for SM infection. Despite limited diagnostic and treatment facilities, overall mortality was 14%, with 7% mortality in children 14 and under, but 19% in adults (60% of cases). Cerebral malaria with coma was relatively rare (17%), but mortality was disproportionately high at 35%. Mean time to hospital presentation was five days (range one to 30 days) after onset of symptoms. While patients with delays in presentation had worse outcomes, there was no excess mortality based on treatment referral times, distance travelled or residence in artemisinin-resistance containment (ARC) Zone 1 compared to Zone 2.

CONCLUSIONS

Despite limitations in diagnosis and treatment, and multiple confounding co-morbidities, mortality rates at BRH were similar to reports from other countries in the region. Interventions to improve access to early diagnosis and effective treatment, combined with modest improvements in intensive care, are likely to reduce mortality further. Patients referred from Zone 1 did not have excess mortality compared to Zone 2 ARC areas. A steep decrease in SM cases and deaths observed in the first half of 2009 has since continued, indicating some success from containment efforts despite the emergence of artemisinin resistance in this area.

Vivax malaria and bacteraemia: a prospective study in Kolkata, India

BACKGROUND

Falciparum malaria increases the risk for bacteraemia, whereas the relationship between vivax malaria and bacteraemia is not clear. Data from a prospective fever surveillance study in Kolkata, India were reanalysed for the potential association between Plasmodium vivax malaria and bacteraemia.

METHODS

Patients of all ages presenting with fever of three days or more to a project health outpost were invited to participate. A blood film and blood culture was performed on presentation. Treatment and referral were provided according to national guidelines. The case fraction and incidence of malaria, bacteraemia, and co-infection were calculated.

RESULTS

3,371 participants were enrolled during a one-year study period, of whom 93/3,371 (2.8%) had malaria (89/93 [95.7%] Plasmodium vivax) and 256 (7.6%) bacteraemia. There were 154 malaria, 423 bacteraemia and 10 P. vivax-bacteremia coinfection episodes per 100,000/year. Among the malaria-bacteraemia co-infections, all were vivax malaria and 5/6 (83%) bacteria isolated were Gram-negative (one S. Typhi, one S. Paratyphi A, three other Gram-negative). Bacteraemia occurred in 6/89 (6.7% [95%CI: 3.1-13.9%]) of P. vivax cases versus 250/3,278 (7.6% [95% CI: 6.7-8.6%]) without Plasmodium infection (p=0.76).

CONCLUSIONS

While an increased risk was not demonstrated, concomitant bacteraemia occurs frequently in vivax malaria in an area with a high background incidence of bacteraemia, and should be considered in cases of vivax malaria with severe manifestations.