Pulmonary manifestations of malaria : recognition and management

Acute lung injury is prevented by monocyte locomotion inhibitory factor in an experimental severe malaria mouse model

Acute lung injury caused by severe malaria (SM) is triggered by a dysregulated immune response towards the infection with Plasmodium parasites. Postmortem analysis of human lungs shows diffuse alveolar damage (DAD), the presence of CD8 lymphocytes, neutrophils, and increased expression of Intercellular Adhesion Molecule 1 (ICAM-1). P. berghei ANKA (PbA) infection in C57BL/6 mice reproduces many SM features, including acute lung injury characterized by DAD, CD8+ T lymphocytes and neutrophils in the lung parenchyma, and tissular expression of proinflammatory cytokines and adhesion molecules, such as IFNγ, TNFα, ICAM, and VCAM. Since this is related to a dysregulated immune response, immunomodulatory agents are proposed to reduce the complications of SM. The monocyte locomotion inhibitory factor (MLIF) is an immunomodulatory pentapeptide isolated from axenic cultures of Entamoeba hystolitica. Thus, we evaluated if the MLIF intraperitoneal (i.p.) treatment prevented SM-induced acute lung injury. The peptide prevented SM without a parasiticidal effect, indicating that its protective effect was related to modifications in the immune response. Furthermore, peripheral CD8+ leukocytes and neutrophil proportions were higher in infected treated mice. However, the treatment prevented DAD, CD8+ cell infiltration into the pulmonary tissue and downregulated IFNγ. Moreover, VCAM-1 expression was abrogated. These results indicate that the MLIF treatment downregulated adhesion molecule expression, impeding cell migration and proinflammatory cytokine tissular production, preventing acute lung injury induced by SM. Our findings represent a potential novel strategy to avoid this complication in various events where a dysregulated immune response triggers lung injury.

Parasitic lung diseases

Parasitic lung diseases are caused by a number of parasites as a result of transient passage in the lung or as a result of an immunologic reaction. The clinical presentation may be in the form of focal or cystic lesions, pleural effusion or diffuse pulmonary infiltrates. With increasing globalisation, it is important to consider parasitic infections in the differential diagnosis of lung diseases. This is particularly important since early identification and prompt therapy result in full cure of these conditions. In this review, we summarise the most common parasitic lung diseases.

Exploring the Role of Antioxidants to Combat Oxidative Stress in Malaria Parasites

BACKGROUND

Malaria, a global challenge, is a parasitic disease caused by Plasmodium species. Approximately 229 million cases of malaria were reported in 2019. Major incidences occur in various continents, including African and Eastern Mediterranean Continents and South-East Asia.

INTRODUCTION

Despite the overall decline in global incidence from 2010 to 2018, the rate of decline has been almost constant since 2014. The morbidity and mortality have been accelerated due to reactive oxygen species (ROS) caused by oxidative stress generated by the parasite responsible for the destruction of host metabolism and cell nutrients.

METHODS

The excessive release of free radicals is associated with the infection in the animal or human body by the parasites. This may be related to a reduction in nutrients required for the generation of antioxidants and the destruction of cells by parasite activity. Therefore, an intensive literature search has been carried out to find the natural antioxidants used to neutralize the free radicals generated during malarial infection.

RESULTS

The natural antioxidants may be useful as an adjuvant treatment along with the antimalarial chemotherapeutics to reduce the death rate and enhance the success rate of malaria treatment.

CONCLUSION

In this manuscript, an attempt has been made to provide significant insight into the antioxidant activities of herbal extracts against malaria parasites.

Long-term acrylamide exposure exacerbates brain and lung pathology in a mouse malaria model

The consumption of dietary acrylamide (ACR), a carcinogen, results in the dysfunction of various organs and the immune system. However, the impact of ACR exposure on the progression of infectious diseases is unknown. This study investigated the effect of ACR on the progression of malaria infection using a mouse model of malaria. C57BL/6 mice were continuously treated with ACR at a dose of 20 mg/kg bodyweight/day for six weeks (long-term exposure) or phosphate-buffered saline (PBS). Next, the mice were infected with the rodent malaria parasite, Plasmodium berghei NK65 (PbNK). Parasitemia and survival rate were analyzed in the different treatment groups. Magnetic resonance imaging (MRI) and histopathological analyses were performed to evaluate the effect of ACR exposure on the morphology of various organs. Long-term ACR exposure exacerbated PbNK-induced multiorgan dysfunction. MRI and histopathological analysis revealed signs of encephalomeningitis and acute respiratory distress syndrome in the PbNK-infected long-term ACR exposure mice, which decreased the survival rate of mice, but not in the PbNK-infected long-term PBS exposure group. These findings enhance our understanding of the impact of ACR on the progression of infectious diseases, such as malaria.

Neuropathological Changes in Nakalanga Syndrome-A Case Report

Nakalanga syndrome is a clinical manifestation of onchocerciasis-associated epilepsy characterized by stunting, delayed or absent secondary sexual development and skeletal deformities, and is often accompanied by epileptic seizures. The pathophysiology of Nakalanga syndrome is unknown. Here, we describe the post-mortem findings of a 17-year-old female who died with Nakalanga syndrome in northern Uganda. Macroscopic and histopathological examination of all major organs (liver, lungs, kidney and heart), including the brain and the pituitary gland, was performed. The suspected cause of death was malaria, and all major organs and pituitary gland appeared normal, except the lungs, which were edematous consistent with the malaria. Neuropathological changes include signs of neuro-inflammation (gliosis and activated microglia), which co-localized with tau-reactive neurofibrillary tangles and threads. The pathology was most abundant in the frontal cortex, thalamic and hypothalamic regions, and mesencephalon. The choroid plexus showed psammoma bodies. These findings indicate accelerated aging, probably due to repeated seizures. The neuropathological findings were similar to other persons who died with onchocerciasis-associated epilepsy. Examination of the pituitary gland did not reveal new information concerning the underlying pathophysiological mechanism of Nakalanga syndrome. Therefore, more post-mortem studies should be performed.

Cardiovascular Findings in Severe Malaria: A Review

Background

Severe malaria remains a leading cause of death worldwide. A greater understanding of its impact on multiple organ systems is essential in reducing the burden of disease. In this review we will summarize previously reported cardiovascular parameters of both adults and children with severe malaria.

Method

For this systematic review we searched MEDLINE and PUBMED for all papers published on cardiac function in severe malaria from January 1, 1990 until September 1, 2019. Severe malaria was defined as per World Health Organization. Publications were included if there was data from echocardiography, Pulse Contour Cardiac Output (PiCCO), or Pulmonary Arterial catheters (PAC) reported. Studies were excluded if related to medication induced cardiac dysfunction, malaria in pregnancy, or included subjects with known pre-existing heart disease.

Results

Twenty-four studies met inclusion criteria, the majority of which were studies of adult patients or a mixed cohort. Six solely involved pediatric patients. Significant heterogeneity existed in the cardiac parameters measured and results reported. One pediatric and one adult study suggested a reduced preload state during severe malaria. Cardiac systolic function was reported primarily within, or above, normative numeric ranges established in uninfected pediatric patients without anemia. Extensive variability existed in adult studies with reports of an elevated cardiac index in two studies, normal cardiac function in two studies, and descriptions of decreased function in two studies. Two reports suggest afterload in pediatric severe malaria is reduced. Reports of changes in the systemic vascular resistance of adults with severe malaria are inconsistent, with two trials demonstrating an increase and two suggesting a decrease. Studies demonstrated a mild rise in pulmonary pressure in both pediatric and adult patients that normalized by discharge.

Conclusion

Based on limited data, the cardiovascular effects of severe malaria appear to be heterogeneous and vary depending on age. Further detailed studies are required to explore and understand the overall hemodynamic effects of this high burden disease.

Associations Between Restrictive Fluid Management and Renal Function and Tissue Perfusion in Adults With Severe Falciparum Malaria: A Prospective Observational Study

Background

Liberal fluid resuscitation has proved harmful in adults with severe malaria, but the level of restriction has not been defined.

Methods

In a prospective observational study in adults with severe falciparum malaria, restrictive fluid management was provided at the discretion of the treating physician. The relationships between the volume of fluid and changes in renal function or tissue perfusion were evaluated.

Results

A total of 154 patients were studied, 41 (26.6%) of whom died. Median total fluid intake during the first 6 and 24 hours from enrollment was 3.3 (interquartile range [IQR], 1.8–5.1) mL/kg per hour and 2.2 (IQR, 1.6–3.2) mL/kg per hour, respectively. Total fluid intake at 6 hours was not correlated with changes in plasma creatinine at 24 hours (n = 116; r_s = 0.16; P = .089) or lactate at 6 hours (n = 94; r_s = −0.05; P = .660). Development of hypotensive shock or pulmonary edema within 24 hours after enrollment were not related to the volume of fluid administration.

Conclusions

Restrictive fluid management did not worsen kidney function and tissue perfusion in adult patients with severe falciparum malaria. We suggest crystalloid administration of 2–3 mL/kg per hour during the first 24 hours without bolus therapy, unless the patient is hypotensive.

Overexpression of Sphingosine Kinase-1 and Sphingosine-1-Phosphate Receptor-3 in Severe Plasmodium falciparum Malaria with Pulmonary Edema

Pulmonary edema (PE) is a major cause of pulmonary manifestations of severe Plasmodium falciparum malaria and is usually associated with acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). The sphingosine kinase-1 (SphK-1)/sphingosine-1-phosphate receptor-3 (S1PR-3) pathway has recently been reported to affect the pathogenesis of lung injury, but the expression of these proteins in the lungs of severe P. falciparum malaria patients has not been investigated. The cellular expression of SphK-1 and S1PR-3 in lung tissues from autopsied patients with P. falciparum malaria was investigated using immunohistochemistry (IHC). Lung tissues from patients who died of severe P. falciparum malaria were classified into two groups based on histopathological findings: those with PE (18 patients) and those without PE (non-PE, 19 patients). Ten samples of normal lung tissues were used as the control group. The protein expression levels of SphK-1 and S1PR-3 were significantly upregulated in endothelial cells (ECs), alveolar epithelial cells, and alveolar macrophages (AMs) in the lungs of severe P. falciparum malaria patients with PE compared to those in the non-PE and control groups (all p < 0.001). In addition, the SphK-1 and S1PR-3 expression levels were significantly positively correlated in pulmonary ECs (r_s = 0.922, p < 0.001), alveolar epithelial cells (r_s = 0.995, p < 0.001), and AMs (r_s = 0.969, p < 0.001). In conclusion, both the SphK-1 and S1PR-3 proteins were overexpressed in the lung tissues of severe P. falciparum malaria patients with PE, suggesting that SphK-1 and S1PR-3 mediate the pathogenesis of PE in severe malaria. Targeting the regulation of SphK-1 and/or S1PR-3 may be an approach to treat pulmonary complications in severe P. falciparum patients.

Lung endothelial cell antigen cross-presentation to CD8+T cells drives malaria-associated lung injury

Malaria-associated acute respiratory distress syndrome (ARDS) and acute lung injury (ALI) are life-threatening manifestations of severe malaria infections. The pathogenic mechanisms that lead to respiratory complications, such as vascular leakage, remain unclear. Here, we confirm that depleting CD8+T cells with anti-CD8β antibodies in C57BL/6 mice infected with P. berghei ANKA (PbA) prevent pulmonary vascular leakage. When we transfer activated parasite-specific CD8+T cells into PbA-infected TCRβ-/- mice (devoid of all T-cell populations), pulmonary vascular leakage recapitulates. Additionally, we demonstrate that PbA-infected erythrocyte accumulation leads to lung endothelial cell cross-presentation of parasite antigen to CD8+T cells in an IFNγ-dependent manner. In conclusion, pulmonary vascular damage in ALI is a consequence of IFNγ-activated lung endothelial cells capturing, processing, and cross-presenting malaria parasite antigen to specific CD8+T cells induced during infection. The mechanistic understanding of the immunopathogenesis in malaria-associated ARDS and ALI provide the basis for development of adjunct treatments.

The angiotensin II/AT1 receptor pathway mediates malaria-induced acute kidney injury

Malaria-induced acute kidney injury (MAKI) is a life-threatening complication of severe malaria. Here, we investigated the potential role of the angiotensin II (Ang II)/AT1 receptor pathway in the development of MAKI. We used C57BL/6 mice infected by Plasmodium berghei ANKA (PbA-infected mice), a well-known murine model of severe malaria. The animals were treated with 20 mg/kg/day losartan, an antagonist of AT1 receptor, or captopril, an angiotensin-converting enzyme inhibitor. We observed an increase in the levels of plasma creatinine and blood urea nitrogen associated with a significant decrease in creatinine clearance, a marker of glomerular flow rate, and glomerular hypercellularity, indicating glomerular injury. PbA-infected mice also presented proteinuria and a high level of urinary γ-glutamyltransferase activity associated with an increase in collagen deposition and interstitial space, showing tubule-interstitial injury. PbA-infected mice were also found to have increased fractional excretion of sodium (FENa+) coupled with decreased cortical (Na++K+)ATPase activity. These injuries were associated with an increase in pro-inflammatory cytokines, such as tumor necrosis factor alpha, interleukin-6, interleukin-17, and interferon gamma, in the renal cortex of PbA-infected mice. All modifications of these structural, biochemical, and functional parameters observed in PbA-infected mice were avoided with simultaneous treatment with losartan or captopril. Our data allow us to postulate that the Ang II/AT1 receptor pathway mediates an increase in renal pro-inflammatory cytokines, which in turn leads to the glomerular and tubular injuries observed in MAKI.

Could Heme Oxygenase-1 Be a New Target for Therapeutic Intervention in Malaria-Associated Acute Lung Injury/Acute Respiratory Distress Syndrome?

Malaria is a serious disease and was responsible for 429,000 deaths in 2015. Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) is one of the main clinical complications of severe malaria; it is characterized by a high mortality rate and can even occur after antimalarial treatment when parasitemia is not detected. Rodent models of ALI/ARDS show similar clinical signs as in humans when the rodents are infected with murine Plasmodium. In these models, it was shown that the induction of the enzyme heme oxygenase 1 (HO-1) is protective against severe malaria complications, including cerebral malaria and ALI/ARDS. Increased lung endothelial permeability and upregulation of VEGF and other pro-inflammatory cytokines were found to be associated with malaria-associated ALI/ARDS (MA-ALI/ARDS), and both were reduced after HO-1 induction. Additionally, mice were protected against MA-ALI/ARDS after treatment with carbon monoxide- releasing molecules or with carbon monoxide, which is also released by the HO-1 activity. However, high HO-1 levels in inflammatory cells were associated with the respiratory burst of neutrophils and with an intensification of inflammation during episodes of severe malaria in humans. Here, we review the main aspects of HO-1 in malaria and ALI/ARDS, presenting the dual role of HO-1 and possibilities for therapeutic intervention by modulating this important enzyme.

What is the cause of this fever? Malaria with concomitant pneumonia

A 43-year-old Hispanic woman presented to the clinic complaining of fever, chills and cough for 14 days. The patient reported a recent trip to Asia 12 days prior to presenting symptoms. Given her physical examination findings, she was treated empirically for community acquired pneumonia. Since her symptoms worsened despite the antibiotic, she was referred to the Emergency Department for further evaluation. The patient was ultimately diagnosed with pneumonia and malaria. When evaluating patients with history of recent travel, it is important to consider communicable diseases that are endemic to the areas visited, as well as multiple disease aetiologies for complicated and refractory cases.

Respiratory Complications of Plasmodium vivax Malaria: Systematic Review and Meta-Analysis

Malaria, a major global public health problem, is mainly caused by Plasmodium falciparum and Plasmodium vivax, and is responsible for nearly half a million deaths annually. Although P. vivax malaria was not believed to cause severe disease, recent robust studies have proved otherwise. However, the clinical spectrum and pathogenesis of severe vivax malaria and, especially, its respiratory complications remain poorly understood. A systematic search for articles reporting respiratory complications associated with vivax malaria was performed in Lilacs, Cochrane, Scielo, Web of Science, and Medline databases irrespective of publication date. Prevalence of acute respiratory distress syndrome (ARDS) and associated mortality among vivax patients were calculated from cross-sectional and longitudinal studies, whereas factors associated with mortality were calculated from data pooled from case reports and series of cases. A total of 101 studies were included (49 cross-sectional or longitudinal and 52 case reports or series of cases). Prevalence of ARDS was 2.8% and 2.2% in children and adults, respectively, with nearly 50% mortality. Moreover, female sex (P = 0.013), having any comorbidity (P = 0.036), lower body temperature (P = 0.032), lower hemoglobin (P = 0.043), and oxygen saturation (P = 0.053) values were significantly associated with mortality. Plasmodium vivax malaria respiratory complications included ARDS and were associated with high mortality. Demographics and clinical characteristics upon presentation to hospital were associated with mortality among patients with respiratory complications in vivax malaria. This study reaffirms the evidence of severe and fatal complications of P. vivax malaria and its associated respiratory complications.

Pulmonary manifestation of Plasmodium falciparum malaria: Case reports and review of the literature

Pulmonary complications, including acute respiratory distress syndrome (ARDS), are well described in P. falciparum (PF) and to a lesser extent in other malaria species. In non-endemic areas, malaria diagnosis may be overlooked; if a thorough travel history is not obtained on all patients with acute febrile illness. Three patients with malaria associated respiratory distress were admitted to our intensive care unit. The diagnosis was delayed; however, all patients received artesunate and intensive therapy with a satisfactory outcome. One patient presented with respiratory disease while the others developed ARDS during or following appropriate therapy. Similarly, level of parasitemia was variable ranging from undetectable to over 5%. Variability in timing and severity of illness is exciting and gives emphasis to the different pathological processes contemplated in this complication.

Upregulated Tim-3/galectin-9 expressions in acute lung injury in a murine malarial model

Malaria is the most relevant parasitic disease worldwide, and severe malaria is characterized by cerebral edema, acute lung injury (ALI), and multiple organ dysfunctions; however, the mechanisms of lung damage need to be better clarified. In this study, we used Kunming outbred mice infected with Plasmodium berghei ANKA (PbANKA) to elucidate the profiles of T cell immunoglobulin and mucin domain-3 (Tim-3) and its ligand galecin-9 (Gal-9) in the development of ALI. Mice were injected intraperitoneally with 10⁶PbANKA-infected red blood cells. The lungs and mediastinal lymph nodes (MLNs) were harvested at days 5, 10, 15, and 20 post infections (p.i.). The grade of lung injury was histopathologically evaluated. Tim-3- and Gal-9-positive cells in the lungs and MLNs were stained by immunohistochemistry, and the messenger RNA (mRNA) expressions of Tim-3, Gal-9, and related cytokines were assessed using quantitative real-time polymerase chain reaction (qRT-PCR). Bronchoalveolar lavage fluid (BALF) analyses were performed from days 18 to 20 p.i. The results showed that the pathological severities in the lungs were increased with times and the total protein level in the BALFs was significantly elevated in PbANKA-infected mice. The numbers of Gal-9⁺ and Tim-3⁺ cells in the lungs were significantly increased, and the mRNA levels of both Gal-9 and Tim-3 in the lungs and MLNs were over-expressed in PbANKA-infected mice. In conclusion, our data suggested that Tim-3/Gal-9 may play a role in PbANKA-induced ALI.

Integrin αDβ2 (CD11d/CD18) mediates experimental malaria-associated acute respiratory distress syndrome (MA-ARDS)

BACKGROUND

Malaria-associated acute respiratory distress syndrome (MA-ARDS) is a potentially lethal complication of clinical malaria. Acute lung injury in MA-ARDS shares features with ARDS triggered by other causes, including alveolar inflammation and increased alveolar-capillary permeability, leading to leak of protein-rich pulmonary oedema fluid. Mechanisms and physiologic alterations in MA-ARDS can be examined in murine models of this syndrome. Integrin αDβ2 is a member of the leukocyte, or β2 (CD18), sub-family of integrins, and emerging observations indicate that it has important activities in leukocyte adhesion, accumulation and signalling. The goal was to perform analysis of the lungs of mice wild type C57Bl/6 (a D (+/+) ) and Knockout C57Bl/6 (a D (-/-) ) with malaria-associated acute lung injury to better determine the relevancy of the murine models and investigate the mechanism of disease.

METHODS

C57BL/6 wild type (a D (+/+) ) and deficient for CD11d sub-unit (a D (-/-) ) mice were monitored after infection with 10(5) Plasmodium berghei ANKA. CD11d subunit expression RNA was measured by real-time polymerase chain reaction, vascular barrier integrity by Evans blue dye (EBD) exclusion and cytokines by ELISA. Protein and leukocytes were measured in bronchoalveolar lavage fluid (BALF) samples. Tissue cellularity was measured by the point-counting technique, F4/80 and VCAM-1 expression by immunohistochemistry. Respiratory function was analysed by non-invasive BUXCO and mechanical ventilation.

RESULTS

Alveolar inflammation, vascular and interstitial accumulation of monocytes and macrophages, and disrupted alveolar-capillary barrier function with exudation of protein-rich pulmonary oedema fluid were present in P. berghei-infected wild type mice and were improved in αDβ2-deficient animals. Key pro-inflammatory cytokines were also decreased in lung tissue from α D (-/-) mice, providing a mechanistic explanation for reduced alveolar-capillary inflammation and leak.

CONCLUSIONS

The results indicate that αDβ2 is an important inflammatory effector molecule in P. berghei-induced MA-ARDS, and that leukocyte integrins regulate critical inflammatory and pathophysiologic events in this model of complicated malaria. Genetic deletion of integrin subunit αD in mice, leading to deficiency of integrin αDβ2, alters lung inflammation and acute lung injury in a mouse model of MA-ARDS caused by P. berghei.

Tissue-Resident CD169(+) Macrophages Form a Crucial Front Line against Plasmodium Infection

Tissue macrophages exhibit diverse functions, ranging from the maintenance of tissue homeostasis, including clearance of senescent erythrocytes and cell debris, to modulation of inflammation and immunity. Their contribution to the control of blood-stage malaria remains unclear. Here, we show that in the absence of tissue-resident CD169(+) macrophages, Plasmodium berghei ANKA (PbA) infection results in significantly increased parasite sequestration, leading to vascular occlusion and leakage and augmented tissue deposition of the malarial pigment hemozoin. This leads to widespread tissue damage culminating in multiple organ inflammation. Thus, the capacity of CD169(+) macrophages to contain the parasite burden and its sequestration into different tissues and to limit infection-induced inflammation is crucial to mitigating Plasmodium infection and pathogenesis.

[Pulmonary complications of malaria: An update]

Malaria is the most important parasitic disease worldwide, being a public health challenge in more than 90 countries. The incidence of pulmonary manifestations has increased in recent years. Acute respiratory distress syndrome is the most severe form within the pulmonary complications of malaria, with high mortality despite proper management. This syndrome manifests with sudden dyspnoea, cough and refractory hypoxaemia. Patients should be admitted to intensive care units and treated with parenteral antimalarial drug treatment and ventilatory and haemodynamic support without delay. Therefore, dyspnoea in patients with malaria should alert clinicians, as the development of respiratory distress is a poor prognostic factor.

Recruited monocytes modulate malaria-induced lung injury through CD36-mediated clearance of sequestered infected erythrocytes

Pulmonary complications occur in a significant percentage of adults and children during the course of severe malaria. The cellular and molecular innate immune mechanisms that limit the extent of pulmonary inflammation and preserve lung function during severe Plasmodium infections remain unclear. In particular, the contributions to pulmonary complications by parasitized erythrocyte sequestration and subsequent clearance from the lung microvasculature by immune cells have not been clearly defined. We used the Plasmodium berghei ANKA-C57BL/6 mouse model of severe malaria to investigate the mechanisms governing the nature and extent of malaria-associated lung injury. We have demonstrated that sequestration of infected erythrocytes on postcapillary endothelial surfaces results in acute lung injury and the rapid recruitment of CCR2(+)CD11b(+)Ly6C(hi) monocytes from the circulation. These recruited cells remain in the lungs as monocyte-derived macrophages and are instrumental in the phagocytic clearance of adherent Plasmodium berghei-infected erythrocytes. In contrast, alveolar macrophages do not play a significant role in the clearance of malaria-infected cells. Furthermore, the results obtained from Ccr2(-/-), Cd36(-/-), and CD36 bone marrow chimeric mice showed that sequestration in the absence of CD36-mediated phagocytic clearance by monocytes leads to exaggerated lung pathologic features. In summary, our data indicate that the intensity of malaria-induced lung pathologic features is proportional to the steady-state levels of Plasmodium-infected erythrocytes adhering to the pulmonary vasculature. Moreover, the present work has defined a major role of recruited monocytes in clearing infected erythrocytes from the pulmonary interstitium, thus minimizing lung damage.

N-acetyl cysteine and mushroom Agaricus sylvaticus supplementation decreased parasitaemia and pulmonary oxidative stress in a mice model of malaria

Background

Malaria infection can cause high oxidative stress, which could lead to the development of severe forms of malaria, such as pulmonary malaria. In recent years, the role of reactive oxygen species in the pathogenesis of the disease has been discussed, as well as the potential benefit of antioxidants supplementation. The aim of this study was to investigate the effects of N-acetyl cysteine (NAC) or mushroom Agaricus sylvaticus supplementation on the pulmonary oxidative changes in an experimental model of malaria caused by Plasmodium berghei strain ANKA.

Methods

Swiss male mice were infected with P. berghei and treated with NAC or AS. Samples of lung tissue and whole blood were collected after one, three, five, seven or ten days of infection for the assessment of thiobarbituric acid reactive substances (TBARS), trolox equivalent antioxidant capacity (TEAC), nitrites and nitrates (NN) and to assess the degree of parasitaemia.

Results

Although parasitaemia increased progressively with the evolution of the disease in all infected groups, there was a significant decrease from the seventh to the tenth day of infection in both antioxidant-supplemented groups. Results showed significant higher levels of TEAC in both supplemented groups, the highest occurring in the group supplemented with A. sylvaticus. In parallel, TBARS showed similar levels among all groups, while levels of NN were higher in animals supplemented with NAC in relation to the positive control groups and A. sylvaticus, whose levels were similar to the negative control group.

Conclusion

Oxidative stress arising from plasmodial infection was attenuated by supplementation of both antioxidants, but A. sylvaticus proved to be more effective and has the potential to become an important tool in the adjuvant therapy of malaria.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-015-0717-0) contains supplementary material, which is available to authorized users.

Effect of chronic khat (Catha edulis, Forsk) use on outcome of Plasmodium berghei ANKA infection in Swiss albino mice

Background

The objective of this study was to explore effects of khat (Catha edulis) on outcome of rodent malaria infection and its anti-plasmodial activities on Plasmodium berghei ANKA (PbA).

Methods

Female Swiss albino mice were orally treated with crude khat (Catha edulis) extracts (100, 200 and 300 mg/kg) on a daily basis for 4 weeks prior to PbA infection. Physical, clinical, hematological, biochemical and histo-pathological features of the mice were assessed. In addition, in vivo anti-plasmodial activities of khat were evaluated.

Results

The finding of this study showed that khat use was strongly associated with increment of levels of liver and kidney biomarkers, leucopenia, severe anemia, rise in level of inflammation biomarkers: C-reactive protein (CRP), uric acid (UA), increased monocyte-lymphocyte count ratio (MLCR), manifestation of cerebral malaria symptoms such as ataxia, paralysis and deviation of the head but with no pulmonary edema. Significantly lower level of parasitemia (P < 0.05), rectal temperature, but, high level of hemoglobin were observed at the early stage of the PbA infection in khat treated mice than the control. With extension of the treatment period, however, drastic increments were observed in parasite load and rectal temperature although there was reduction in hemoglobin (Hb) level. Moreover, khat showed poor anti-plasmodial activity with <10% parasite suppression activity and lack protection against major malaria symptoms. The significant reduction (P < 0.01) of hematological parameters during PbA infection strengthen the notion that hematological parameters could be good predictors of severe malaria complications in human.

Conclusions

In mice model treated with khat prior to infection with the rodent malaria parasite, khat was found to worsen manifestation of most malaria complications. Furthermore, the same plant showed poor in vivo anti-plasmodial activity and protection against major malaria symptoms.

Plasmodium vivax infection impersonating Plasmodium falciparum malaria

A 73-year-old woman came to the casualty ward with symptoms of syncopal attacks, weakness, fever with chills and rigors. A provisional diagnosis of Plasmodium vivax malaria was made after the blood investigations. She had deranged renal function tests, altered sensorium and low platelet count. Repeated tests for P. falciparum (Card test) were negative. Glucose-6-Phosphate dehydrogenise (G6PD) levels were within normal limits. Treatment for P. vivax was started with intravenous quinine initially followed by oral quinine for a period of seven days and patient responded to the treatment and was discharged within 2 weeks of admission. Most of the cases of P. vivax present with typical and predictable features, although atypical cases with characteristics of P. falciparum can occur, especially in the elderly.

Etiopathogenesis and Pathophysiology of Malaria

Malaria is a parasitic disease caused by Plasmodium protozoan parasites and transmitted by Anopheles mosquitoes. The disease is diffused in tropical areas, where it is associated with high morbidity and mortality. P. falciparum is the most dangerous species, mainly affecting young children. The parasite cycle occurs both in humans (asexual stages) and in mosquitoes (sexual stages). In humans, Plasmodium grows and multiplies within red blood cells using hemoglobin as essential source of nutrients and energy. However, this process generates toxic heme that the parasite aggregates into an insoluble inert biocrystal called hemozoin. This molecule sequesters in various organs (liver, spleen, and brain), potentially contributing to the development of malaria immunopathogenesis. Uncomplicated falciparum malaria clinical frame ranges from asymptomatic infection to classic symptoms such as fever, chills, sweating, headache, and muscle aches. However, malaria can also evolve into severe life-threatening complications, including cerebral malaria, severe anemia, respiratory distress, and acute renal failure.

The systemic pathology of cerebral malaria in African children

Pediatric cerebral malaria carries a high mortality rate in sub-Saharan Africa. We present our systematic analysis of the descriptive and quantitative histopathology of all organs sampled from a series of 103 autopsies performed between 1996 and 2010 in Blantyre, Malawi on pediatric cerebral malaria patients and control patients (without coma, or without malaria infection) who were clinically well characterized prior to death. We found brain swelling in all cerebral malaria patients and the majority of controls. The histopathology in patients with sequestration of parasites in the brain demonstrated two patterns: (a) the “classic” appearance (i.e., ring hemorrhages, dense sequestration, and extra-erythrocytic pigment) which was associated with evidence of systemic activation of coagulation and (b) the “sequestration only” appearance associated with shorter duration of illness and higher total burden of parasites in all organs including the spleen. Sequestration of parasites was most intense in the gastrointestinal tract in all parasitemic patients (those with cerebral malarial and those without).

Tumor necrosis factor -α, interleukin-10, intercellular and vascular adhesion molecules are possible biomarkers of disease severity in complicated Plasmodium vivax isolates from Pakistan

BACKGROUND

Cytokine-mediated endothelial activation pathway is a known mechanism of pathogenesis employed by Plasmodium falciparum to induce severe disease symptoms in human host. Though considered benign, complicated cases of Plasmodium vivax are being reported worldwide and from Pakistan. It has been hypothesized that P.vivax utilizes similar mechanism of pathogenesis, as that of P.falciparum for manifestations of severe malaria. Therefore, the main objective of this study was to characterize the role of cytokines and endothelial activation markers in complicated Plasmodium vivax isolates from Pakistan.

METHODS AND PRINCIPLE FINDINGS

A case control study using plasma samples from well-characterized groups suffering from P.vivax infection including uncomplicated cases (n=100), complicated cases (n=82) and healthy controls (n=100) were investigated. Base line levels of Tumor necrosis factor-α (TNF-α), Interleukin-6 (IL-6), Interleukin-10 (IL-10), Intercellular adhesion molecule-1 (ICAM-1), Vascular adhesion molecule-1(VCAM-1) and E-selectin were measured by ELISA. Correlation of cytokines and endothelial activation markers was done using Spearman's correlation analysis. Furthermore, significance of these biomarkers as indicators of disease severity was also analyzed. The results showed that TNF-α, IL-10, ICAM-1and VCAM-1 were 3-fold, 3.7 fold and 2 fold increased between uncomplicated and complicated cases. Comparison of healthy controls with uncomplicated cases showed no significant difference in TNF-α concentrations while IL-6, IL-10, ICAM-1, VCAM-1 and E-selectin were found to be elevated respectively. In addition, significant positive correlation was observed between TNF-α and IL-10/ ICAM-1, IL-6 and IL-10, ICAM-1 and VCAM-1.A Receiver operating curve (ROC) was generated which showed that TNF-α, IL-10, ICAM-1 and VCAM-1 were the best individual predictors of complicated P.vivax malaria.

CONCLUSION

The results suggest that though endothelial adhesion molecules are inducible by pro-inflammatory cytokine TNF-α, however, cytokine-mediated endothelial activation pathway is not clearly demonstrated as a mechanism of pathogenesis in complicated P.vivax malaria cases from Pakistan.

Acute respiratory distress syndrome and acute renal failure from Plasmodium ovale infection with fatal outcome

BACKGROUND

Plasmodium ovale is one of the causative agents of human malaria. Plasmodium ovale infection has long been thought to be non-fatal. Due to its lower morbidity, P. ovale receives little attention in malaria research.

METHODS

Two Malaysians went to Nigeria for two weeks. After returning to Malaysia, they fell sick and were admitted to different hospitals. Plasmodium ovale parasites were identified from blood smears of these patients. The species identification was further confirmed with nested PCR. One of them was successfully treated with no incident of relapse within 12-month medical follow-up. The other patient came down with malaria-induced respiratory complication during the course of treatment. Although parasites were cleared off the circulation, the patient's condition worsened. He succumbed to multiple complications including acute respiratory distress syndrome and acute renal failure.

RESULTS

Sequencing of the malaria parasite DNA from both cases, followed by multiple sequence alignment and phylogenetic tree construction suggested that the causative agent for both malaria cases was P. ovale curtisi.

DISCUSSION

In this report, the differences between both cases were discussed, and the potential capability of P. ovale in causing severe complications and death as seen in this case report was highlighted.

CONCLUSION

Plasmodium ovale is potentially capable of causing severe complications, if not death. Complete travel and clinical history of malaria patient are vital for successful diagnoses and treatment. Monitoring of respiratory and renal function of malaria patients, regardless of the species of malaria parasites involved is crucial during the course of hospital admission.

Pulmonary pathology in pediatric cerebral malaria

Respiratory signs are common in African children where malaria is highly endemic, and thus, parsing the role of pulmonary pathology in illness is challenging. We examined the lungs of 100 children from an autopsy series in Blantyre, Malawi, many of whom death was attributed to Plasmodium falciparum malaria. Our aim was to describe the pathologic manifestations of fatal malaria; to understand the role of parasites, pigment, and macrophages; and to catalog comorbidities. From available patients, which included 55 patients with cerebral malaria and 45 controls, we obtained 4 cores of lung tissue for immunohistochemistry and morphological evaluation. We found that, in patients with cerebral malaria, large numbers of malaria parasites were present in pulmonary alveolar capillaries, together with extensive deposits of malaria pigment (hemozoin). The number of pulmonary macrophages in this vascular bed did not differ between patients with cerebral malaria, noncerebral malaria, and nonmalarial diagnoses. Comorbidities found in some cerebral malaria patients included pneumonia, pulmonary edema, hemorrhage, and systemic activation of coagulation. We conclude that the respiratory distress seen in patients with cerebral malaria does not appear to be anatomic in origin but that increasing malaria pigment is strongly associated with cerebral malaria at autopsy.

CD36 and Fyn kinase mediate malaria-induced lung endothelial barrier dysfunction in mice infected with Plasmodium berghei

Severe malaria can trigger acute lung injury characterized by pulmonary edema resulting from increased endothelial permeability. However, the mechanism through which lung fluid conductance is altered during malaria remains unclear. To define the role that the scavenger receptor CD36 may play in mediating this response, C57BL/6J (WT) and CD36−/− mice were infected with P. berghei ANKA and monitored for changes in pulmonary endothelial barrier function employing an isolated perfused lung system. WT lungs demonstrated a >10-fold increase in two measures of paracellular fluid conductance and a decrease in the albumin reflection coefficient (σ_alb) compared to control lungs indicating a loss of barrier function. In contrast, malaria-infected CD36−/− mice had near normal fluid conductance but a similar reduction in σ_alb. In WT mice, lung sequestered iRBCs demonstrated production of reactive oxygen species (ROS). To determine whether knockout of CD36 could protect against ROS-induced endothelial barrier dysfunction, mouse lung microvascular endothelial monolayers (MLMVEC) from WT and CD36−/− mice were exposed to H₂O₂. Unlike WT monolayers, which showed dose-dependent decreases in transendothelial electrical resistance (TER) from H₂O₂ indicating loss of barrier function, CD36−/− MLMVEC demonstrated dose-dependent increases in TER. The differences between responses in WT and CD36−/− endothelial cells correlated with important differences in the intracellular compartmentalization of the CD36-associated Fyn kinase. Malaria infection increased total lung Fyn levels in CD36−/− lungs compared to WT, but this increase was due to elevated production of the inactive form of Fyn further suggesting a dysregulation of Fyn-mediated signaling. The importance of Fyn in CD36-dependent endothelial signaling was confirmed using in vitro Fyn knockdown as well as Fyn−/− mice, which were also protected from H₂O₂- and malaria-induced lung endothelial leak, respectively. Our results demonstrate that CD36 and Fyn kinase are critical mediators of the increased lung endothelial fluid conductance caused by malaria infection.

Pathogenesis of malaria-associated acute respiratory distress syndrome

Malaria-associated acute respiratory distress syndrome (MA-ARDS) is an increasingly reported, often lethal, and incompletely understood complication of malaria. We discuss and compare the pathogenesis of MA-ARDS in patients and in different murine models, including recent models without cerebral involvement, and summarize the roles of different leukocyte subclasses, adhesion molecules, cytokines, and chemokines. In patients as well as in mice, severe edema and impaired gas exchange are associated with abundant inflammatory infiltrates consisting of mainly mononuclear cells and parasite sequestration, and the pathogenesis appears different from cerebral malaria (CM). Experimental anti-inflammatory interventions are successful in mice and remain to be validated in patients.

Fluid resuscitation of adults with severe falciparum malaria: effects on Acid-base status, renal function, and extravascular lung water

OBJECTIVE

To evaluate the efficacy and safety of liberal fluid resuscitation of adults with severe malaria. DESIGN, SETTING, PATIENTS, AND METHODS: Twenty-eight Bangladeshi and Indian adults with severe falciparum malaria received crystalloid resuscitation guided by transpulmonary thermodilution (PiCCO) in an intensive care setting. Systemic hemodynamics, microvascular indices and measures of acidosis, renal function, and pulmonary edema were followed prospectively.

RESULTS

All patients were hypovolemic (global end-diastolic volume index<680 mL/m) on enrollment. Patients received a median (range) 3230 mL (390-7300) of isotonic saline in the first 6 hours and 5450 mL (710-13,720) in the first 24 hours. With resuscitation, acid-base status deteriorated in 19 of 28 (68%), and there was no significant improvement in renal function. Extravascular lung water increased in 17 of 22 liberally resuscitated patients (77%); eight of these patients developed pulmonary edema, five of whom died. All other patients survived. All patients with pulmonary edema during the study were hypovolemic or euvolemic at the time pulmonary edema developed. Plasma lactate was lower in hypovolemic patients before (rs=0.38; p=0.05) and after (rs=0.49; p=0.01) resuscitation but was the strongest predictor of mortality before (chi-square=9.9; p=0.002) and after resuscitation (chi-square=11.1; p<0.001) and correlated with the degree of visualized microvascular sequestration of parasitized erythrocytes at both time points (rs=0.55; p=0.003 and rs=0.43; p=0.03, respectively). Persisting sequestration was evident in 7 of 15 patients (47%) 48 hours after enrollment.

CONCLUSIONS

Lactic acidosis--the strongest prognostic indicator in adults with severe falciparum malaria--results from sequestration of parasitized erythrocytes in the microcirculation, not from hypovolemia. Liberal fluid resuscitation has little effect on this sequestration and does not improve acid-base status or renal function. Pulmonary edema--secondary to increased pulmonary vascular permeability--is common, unpredictable, and exacerbated by fluid loading. Liberal fluid replacement of adults with severe malaria should be avoided.

Respiratory manifestations of malaria

Respiratory distress develops in up to 25% of adults and 40% of children with severe falciparum malaria. Its diverse causes include respiratory compensation of metabolic acidosis, noncardiogenic pulmonary edema, concomitant pneumonia, and severe anemia. Patients with severe falciparum, vivax, and knowlesi malaria may develop acute lung injury (ALI) and ARDS, often several days after antimalarial drug treatment. ARDS rates, best characterized for severe Plasmodium falciparum, are 5% to 25% in adults and up to 29% in pregnant women; ARDS is rare in young children. ARDS pathophysiology centers on inflammatory-mediated increased capillary permeability or endothelial damage leading to diffuse alveolar damage that can continue after parasite clearance. The role of parasite sequestration in the pulmonary microvasculature is unclear, because sequestration occurs intensely in P falciparum, less so in P knowlesi, and has not been shown convincingly in P vivax. Because early markers of ALI/ARDS are lacking, fluid resuscitation in severe malaria should follow the old adage to "keep them dry." Bacteremia and hospital-acquired pneumonia can complicate severe malaria and may contribute to ALI/ARDS. Mechanical ventilation can save life in ALI/ARDS. Basic critical care facilities are increasingly available in tropical countries. The use of lung-protective ventilation has helped to reduce mortality from malaria-induced ALI/ARDS, but permissive hypercapnia in unconscious patients is not recommended because increased intracranial pressure and cerebral swelling may occur in cerebral malaria. The best antimalarial treatment of severe malaria is IV artesunate.

Infection and acute respiratory distress syndrome during pregnancy: a case series of preventable maternal deaths from southern India

INTRODUCTION

Acute respiratory distress syndrome (ARDS) is common among women admitted to obstetric intensive care units, and it contributes significantly, both directly and indirectly, to maternal deaths.

CASE SERIES

We present a case series of ARDS in pregnant women caused by non-obstetric causes. The women were treated at a tertiary hospital in southern India. The striking features were delayed referral from the primary care unit and the lack of a primary diagnosis or treatment. Undiagnosed rheumatic heart disease, anemia, and malaria and H1N1 epidemics contributed to these cases of ARDS and maternal death.

CONCLUSION

It is necessary to increase the awareness of evidence-based uniform protocols to tackle common medical complaints during pregnancy.

Clinical profile of severe malaria: study from a tertiary care center in north India

One hundred and sixty patients having clinical features of severe malaria reported during monsoon season-August-October 2010 at this tertiary care center of north India. Of these 110 (68.75 %) had Plasmodium vivax infection, 30 (18.75 %) were infected with P. falciparum and 20 (12.5 %) had co-infection due to P. vivax and P. falciparum. The diagnosis was made using Rapid Card Test and was confirmed by peripheral smear examination of thick and thin films. Several complications such as acute kidney injury, jaundice, severe anemia, metabolic acidosis, shock, hyperpyrexia, hypoglycemia, generalized tonic-clonic convulsions etc. were found to be more prevalent in patients with P. vivax infection. These symptoms were until recently known to be associated with falciparum malaria.

Infectious diseases causing diffuse alveolar hemorrhage in immunocompetent patients: a state-of-the-art review

Diffuse alveolar hemorrhage (DAH) represents a syndrome that can complicate many clinical conditions and may be life-threatening, requiring prompt treatment. It is recognized by the signs of acute- or subacute-onset cough, hemoptysis, diffuse radiographic pulmonary infiltrates, anemia, and hypoxemic respiratory distress. DAH is characterized by the accumulation of intra-alveolar red blood cells originating most frequently from the alveolar capillaries. It must be distinguished from localized pulmonary hemorrhage, which is most commonly due to chronic bronchitis, bronchiectasis, tumor, or localized infection. Hemoptysis, the major sign of DAH, may develop suddenly or over a period of days to weeks; this sign may also be initially absent, in which case diagnostic suspicion is established after sequential bronchoalveolar lavage reveals worsening red blood cell counts. The causes of DAH can be divided into infectious and noninfectious, the latter of which may affect immunocompetent or immunodeficient patients. Pulmonary infections are rarely reported in association with DAH, but they should be considered in the diagnostic workup because of the obvious therapeutic implications. In immunocompromised patients, the main infectious diseases that cause DAH are cytomegalovirus, adenovirus, invasive aspergillosis, Mycoplasma, Legionella, and Strongyloides. In immunocompetent patients, the infectious diseases that most frequently cause DAH are influenza A (H1N1), dengue, leptospirosis, malaria, and Staphylococcus aureus infection. Based on a search of the PubMed and Scopus databases, we review the infectious diseases that may cause DAH in immunocompetent patients.

Predicting the clinical outcome of severe falciparum malaria in african children: findings from a large randomized trial

Four predictors were independently associated with an increased risk of death: acidosis, cerebral manifestations of malaria, elevated blood urea nitrogen, or signs of chronic illness. The standard base deficit was found to be the single most relevant predictor of death.

Background. Data from the largest randomized, controlled trial for the treatment of children hospitalized with severe malaria were used to identify such predictors of a poor outcome from severe malaria.

Methods. African children (<15 years) with severe malaria participated in a randomized comparison of parenteral artesunate and parenteral quinine in 9 African countries. Detailed clinical assessment was performed on admission. Parasite densities were assessed in a reference laboratory. Predictors of death were examined using a multivariate logistic regression model.

Results. Twenty indicators of disease severity were assessed, out of which 5 (base deficit, impaired consciousness, convulsions, elevated blood urea, and underlying chronic illness) were associated independently with death. Tachypnea, respiratory distress, deep breathing, shock, prostration, low pH, hyperparasitemia, severe anemia, and jaundice were statistically significant indicators of death in the univariate analysis but not in the multivariate model. Age, glucose levels, axillary temperature, parasite density, heart rate, blood pressure, and blackwater fever were not related to death in univariate models.

Conclusions. Acidosis, cerebral involvement, renal impairment, and chronic illness are key independent predictors for a poor outcome in African children with severe malaria. Mortality is markedly increased in cerebral malaria combined with acidosis.

Clinical Trial Registration. ISRCTN50258054.

Central venous catheter use in severe malaria: time to reconsider the World Health Organization guidelines?

BACKGROUND

To optimize the fluid status of adult patients with severe malaria, World Health Organization (WHO) guidelines recommend the insertion of a central venous catheter (CVC) and a target central venous pressure (CVP) of 0-5 cmH2O. However there are few data from clinical trials to support this recommendation.

METHODS

Twenty-eight adult Indian and Bangladeshi patients admitted to the intensive care unit with severe falciparum malaria were enrolled in the study. All patients had a CVC inserted and had regular CVP measurements recorded. The CVP measurements were compared with markers of disease severity, clinical endpoints and volumetric measures derived from transpulmonary thermodilution.

RESULTS

There was no correlation between the admission CVP and patient outcome (p = 0.67) or disease severity (p = 0.33). There was no correlation between the baseline CVP and the concomitant extravascular lung water (p = 0.62), global end diastolic volume (p = 0.88) or cardiac index (p = 0.44). There was no correlation between the baseline CVP and the likelihood of a patient being fluid responsive (p = 0.37). On the occasions when the CVP was in the WHO target range patients were usually hypovolaemic and often had pulmonary oedema by volumetric measures. Seven of 28 patients suffered a complication of the CVC insertion, although none were fatal.

CONCLUSION

The WHO recommendation for the routine insertion of a CVC, and the maintenance of a CVP of 0-5 cmH2O in adults with severe malaria, should be reconsidered.

A retrospective analysis of the haemodynamic and metabolic effects of fluid resuscitation in Vietnamese adults with severe falciparum malaria

Background

Optimising the fluid resuscitation of patients with severe malaria is a simple and potentially cost-effective intervention. Current WHO guidelines recommend central venous pressure (CVP) guided, crystalloid based, resuscitation in adults.

Methods

Prospectively collected haemodynamic data from intervention trials in Vietnamese adults with severe malaria were analysed retrospectively to assess the responses to fluid resuscitation.

Results

43 patients were studied of whom 24 received a fluid load. The fluid load resulted in an increase in cardiac index (mean increase: 0.75 L/min/m² (95% Confidence interval (CI): 0.41 to 1.1)), but no significant change in acid-base status post resuscitation (mean increase base deficit 0.6 mmol/L (95% CI: −0.1 to 1.3). The CVP and PAoP (pulmonary artery occlusion pressure) were highly inter-correlated (r_s = 0.7, p<0.0001), but neither were correlated with acid-base status (arterial pH, serum bicarbonate, base deficit) or respiratory status (PaO₂/FiO₂ ratio). There was no correlation between the oxygen delivery (DO₂) and base deficit at the 63 time-points where they were assessed simultaneously (r_s = −0.09, p = 0.46).

Conclusions

In adults with severe falciparum malaria there was no observed improvement in patient outcomes or acid-base status with fluid loading. Neither CVP nor PAoP correlated with markers of end-organ perfusion or respiratory status, suggesting these measures are poor predictors of their fluid resuscitation needs.

Nitric oxide for the adjunctive treatment of severe malaria: hypothesis and rationale

We hypothesize that supplemental inhaled nitric oxide (iNO) will improve outcomes in children with severe malaria receiving standard antimalarial therapy. The rationale for the hypothesized efficacy of iNO rests on: (1) biological plausibility, based on known actions of NO in modulating endothelial activation; (2) pre-clinical efficacy data from animal models of experimental cerebral malaria; and (3) a human trial of the NO precursor l-arginine, which improved endothelial function in adults with severe malaria. iNO is an attractive new candidate for the adjunctive treatment of severe malaria, given its proven therapeutic efficacy in animal studies, track record of safety in clinical practice and numerous clinical trials, inexpensive manufacturing costs, and ease of administration in settings with limited healthcare infrastructure. We plan to test this hypothesis in a randomized controlled trial (ClinicalTrials.gov Identifier: NCT01255215).

A case of successfully treated acute respiratory distress syndrome complicating Plasmodium falciparum malaria

While endemic malaria has been eliminated in the United States, approximately 1200 mostly imported cases are reported annually in the country, with fewer than 20 recorded deaths. Because of the rarity of this disease in the United States, clinicians are often unfamiliar with its diagnosis and presentation. In a review of all malaria deaths in the United States from 1963 to 2001, failure to diagnose malaria on initial presentation, promptly initiate treatment, and/or prescribe appropriate antimalarial drugs were identified as contributing factors to death. Plasmodium falciparum can lead to a particularly severe type of malaria complicated by acute respiratory distress syndrome (ARDS), and physicians must be alert to the possibility of this diagnosis in immigrants and returning travelers. We report a case of successfully treated acute respiratory distress syndrome complicating imported P falciparum malaria at a large teaching hospital in Washington, DC.

Atypical manifestations of malaria

Malaria remains a major cause of morbidity and mortality worldwide. The classic presentation of malaria with paroxysms of fever is seen only in 50%-70% of patients. Development of immunity, increasing resistance to antimalarial drugs, and indiscriminate use of antimalarial drugs have led to malaria presenting with unusual features. This review compiles a description of the various atypical manifestations of malaria.

Malaria in pregnancy: update on emergency management

BACKGROUND

Pregnancy complicates the diagnosis, treatment, and clinical course of malaria. This clinical problem may be encountered in emergency department patients due to international travel.

CASE REPORT

A primigravida woman at 20 weeks gestation presented to the Emergency Department with episodic fever, chills, headache, and nausea after travel to India and Asia. She had not taken malaria prophylaxis. After hospitalization, she developed acute respiratory distress syndrome and required intensive care management. Although she ultimately recovered from severe infection with Plasmodium vivax, she was not able to sustain her pregnancy and suffered a miscarriage.

CONCLUSION

This case illustrates the serious nature of malaria in the pregnant patient. For this high-risk group, there is an increased incidence of severe anemia, as well as acute respiratory distress syndrome and pulmonary edema. A guideline is presented for the initial choice of anti-malarial drug treatment for the pregnant patient.

VEGF promotes malaria-associated acute lung injury in mice

The spectrum of the clinical presentation and severity of malaria infections is broad, ranging from uncomplicated febrile illness to severe forms of disease such as cerebral malaria (CM), acute lung injury (ALI), acute respiratory distress syndrome (ARDS), pregnancy-associated malaria (PAM) or severe anemia (SA). Rodent models that mimic human CM, PAM and SA syndromes have been established. Here, we show that DBA/2 mice infected with P. berghei ANKA constitute a new model for malaria-associated ALI. Up to 60% of the mice showed dyspnea, airway obstruction and hypoxemia and died between days 7 and 12 post-infection. The most common pathological findings were pleural effusion, pulmonary hemorrhage and edema, consistent with increased lung vessel permeability, while the blood-brain barrier was intact. Malaria-associated ALI correlated with high levels of circulating VEGF, produced de novo in the spleen, and its blockage led to protection of mice from this syndrome. In addition, either splenectomization or administration of the anti-inflammatory molecule carbon monoxide led to a significant reduction in the levels of sera VEGF and to protection from ALI. The similarities between the physiopathological lesions described here and the ones occurring in humans, as well as the demonstration that VEGF is a critical host factor in the onset of malaria-associated ALI in mice, not only offers important mechanistic insights into the processes underlying the pathology related with malaria but may also pave the way for interventional studies.

Avian influenza--a review for doctors in travel medicine

First identified in humans in Hong Kong, influenza A/H5N1, known commonly as avian influenza, has caused human disease in 15 countries around the world. Although the current number of confirmed patients is tiny compared to seasonal and the recently emerged H1N1 'swine' influenza, H5N1 remains a candidate for the next highly pathogenic influenza pandemic. Currently, H5N1 has very limited ability to spread from person-to-person but this may change because of mutation or reassortment with other influenza viruses leading to an influenza pandemic with high mortality. If this occurs travellers are likely to be affected and travel medicine doctors will need to consider avian influenza in returning febrile travellers. The early clinical features may be dismissed easily as 'the flu' resulting in delayed treatment. Treatment options are limited. Oral oseltamivir alone has been the most commonly used drug but mortality remains substantial, up to 80% in Indonesia. Intravenous peramivir has been filed for registration and IV zanamivir is being developed. This review will focus on the epidemiological and clinical features of influenza A/H5N1 avian influenza and will highlight aspects relevant to travel medicine doctors.

Clinical and laboratory features of human Plasmodium knowlesi infection

BACKGROUND

Plasmodium knowlesi is increasingly recognized as a cause of human malaria in Southeast Asia but there are no detailed prospective clinical studies of naturally acquired infections.

METHODS

In a systematic study of the presentation and course of patients with acute P. knowlesi infection, clinical and laboratory data were collected from previously untreated, nonpregnant adults admitted to the hospital with polymerase chain reaction-confirmed acute malaria at Kapit Hospital (Sarawak, Malaysia) from July 2006 through February 2008.

RESULTS

Of 152 patients recruited, 107 (70%) had P. knowlesi infection, 24 (16%) had Plasmodium falciparum infection, and 21 (14%) had Plasmodium vivax. Patients with P. knowlesi infection presented with a nonspecific febrile illness, had a baseline median parasitemia value at hospital admission of 1387 parasites/microL (interquartile range, 6-222,570 parasites/microL), and all were thrombocytopenic at hospital admission or on the following day. Most (93.5%) of the patients with P. knowlesi infection had uncomplicated malaria that responded to chloroquine and primaquine treatment. Based on World Health Organization criteria for falciparum malaria, 7 patients with P. knowlesi infection (6.5%) had severe infections at hospital admission. The most frequent complication was respiratory distress, which was present at hospital admission in 4 patients and developed after admission in an additional 3 patients. P. knowlesi parasitemia at hospital admission was an independent determinant of respiratory distress, as were serum creatinine level, serum bilirubin, and platelet count at admission (p < .002 for each). Two patients with knowlesi malaria died, representing a case fatality rate of 1.8% (95% confidence interval, 0.2%-6.6%).

CONCLUSIONS

Knowlesi malaria causes a wide spectrum of disease. Most cases are uncomplicated and respond promptly to treatment, but approximately 1 in 10 patients develop potentially fatal complications.