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

Experimental Models to Study the Pathogenesis of Malaria-Associated Acute Respiratory Distress Syndrome

Malaria-associated acute respiratory distress syndrome (MA-ARDS) is increasingly gaining recognition as a severe malaria complication because of poor prognostic outcomes, high lethality rate, and limited therapeutic interventions. Unfortunately, invasive clinical studies are challenging to conduct and yields insufficient mechanistic insights. These limitations have led to the development of suitable MA-ARDS experimental mouse models. In patients and mice, MA-ARDS is characterized by edematous lung, along with marked infiltration of inflammatory cells and damage of the alveolar-capillary barriers. Although, the pathogenic pathways have yet to be fully understood, the use of different experimental mouse models is fundamental in the identification of mediators of pulmonary vascular damage. In this review, we discuss the current knowledge on endothelial activation, leukocyte recruitment, leukocyte induced-endothelial dysfunction, and other important findings, to better understand the pathogenesis pathways leading to endothelial pulmonary barrier lesions and increased vascular permeability. We also discuss how the advances in imaging techniques can contribute to a better understanding of the lung lesions induced during MA-ARDS, and how it could aid to monitor MA-ARDS severity.

Skeleton binding protein-1-mediated parasite sequestration inhibits spontaneous resolution of malaria-associated acute respiratory distress syndrome

Malaria is a hazardous disease caused by Plasmodium parasites and often results in lethal complications, including malaria-associated acute respiratory distress syndrome (MA-ARDS). Parasite sequestration in the microvasculature is often observed, but its role in malaria pathogenesis and complications is still incompletely understood. We used skeleton binding protein-1 (SBP-1) KO parasites to study the role of sequestration in experimental MA-ARDS. The sequestration-deficiency of these SBP-1 KO parasites was confirmed with bioluminescence imaging and by measuring parasite accumulation in the lungs with RT-qPCR. The SBP-1 KO parasites induced similar lung pathology in the early stage of experimental MA-ARDS compared to wildtype (WT) parasites. Strikingly, the lung pathology resolved subsequently in more than 60% of the SBP-1 KO infected mice, resulting in prolonged survival despite the continuous presence of the parasite. This spontaneous disease resolution was associated with decreased inflammatory cytokine expression measured by RT-qPCR and lower expression of cytotoxic markers in pathogenic CD8⁺ T cells in the lungs of SBP-1 KO infected mice. These data suggest that SBP-1-mediated parasite sequestration and subsequent high parasite load are not essential for the development of experimental MA-ARDS but inhibit the resolution of the disease.

Malaria is still a severe global disease with more than 200 million cases and 400 000 deaths each year. Plasmodium falciparum is the species responsible for most malaria deaths globally. The propensity of these parasites to sequester in peripheral vascular beds is assumed to play an important role in disease severity and mortality. Although sequestration has been observed in lungs of malaria patients, its role in the pathogenesis of MA-ARDS, a severe lung complication in malaria, was previously unknown. Therefore, we used sequestration-deficient SBP-1 KO Plasmodium berghei NK65 parasites to study the role of sequestration in experimental MA-ARDS. We observed that MA-ARDS developed similarly in WT and SBP-1 KO infected mice, but the majority of SBP-1 KO-infected mice were able to resolve the lung pathology despite the continuous presence of the parasite. This coincided with a prolonged survival, a decrease in inflammatory cytokine expression and lower expression of cytotoxicity markers in pathogenic CD8⁺ T cells. These results give important new insights in the role of parasite sequestration in malaria pathology.

COULD COVID-19 BE A HEMOGLOBINOPATHY?

The world is struggling to deal with the corona pandemic. Effective therapies are still awaited due to the lack of understanding of the pathophysiological mechanism of the disease. Bearing recent research and clinical observations in mind, the authors propose a novel physiological mechanism of COVID-19 and explain development of COVID-19 related acute respiratory distress syndrome (ARDS) secondary to COVID-19 related hemoglobinopathy. It is a consistent observation that the radiological picture of COVID-19 related ARDS bears more resemblance to high altitude pulmonary edema (HAPE) than typical ARDS. There has been great controversy regarding this proposed similarity. The main argument from those objecting to this comparison is that the etiology is hypoxia in case of HAPE and inflammation in COVID-19 related ARDS. We propose that considering the recent bioinformatics prediction models, COVID-19 might first infect red blood cells via CD147 and cause hemoglobin damage. The resulting hypoxemia may cause pulmonary hypoxic vasoconstriction leading to HAPE-like lung lesions. The now introduced alveolar hypoxia further exaggerates hemoglobinopathy hypoxemia leading to a vicious cycle. In this review, the authors recommend laboratory experiments to prove these hypotheses. The proposed physiological mechanism has significant therapeutic implications. If proven, the authors suggest the use of exchange transfusion as adjunct therapy and development of anti-CD147 drugs.

Parasitic diseases as a cause of acute abdominal pain: imaging findings

Acute abdominal pain can be seen in cases with parasitic diseases delivered to emergency departments. The diagnosis of the parasitic disease can be delayed because of the similar clinical signs encountered in other frequently seen causes of acute abdomen. Nevertheless, the features detected in imaging scans can be helpful in the diagnosis. The present study aims to raise awareness about abdominal parasitosis in emergency conditions and also to underline the association between imaging findings and the life cycle of parasites with illustrative cases.

Descriptive Acute Respiratory Distress Syndrome (ARDS) in adults with imported severe Plasmodium falciparum malaria: A 10 year-study in a Portuguese tertiary care hospital

BACKGROUND

Acute respiratory distress syndrome (ARDS) is a severe complication of malaria that remains largely unstudied. We aim to describe the development of ARDS associated with severe P. falciparum malaria, its management and impact on clinical outcome.

METHODS

Retrospective observational study of adult patients admitted with severe P. falciparum malaria in an Intensive Care Unit (ICU) of a tertiary care hospital from Portugal from 2008 to 2018. A multivariate logistic regression analysis was used to identify factors associated with the development of ARDS, defined according to Berlin Criteria. Prognosis was assessed by case-fatality ratio, nosocomial infection and length of stay.

RESULTS

98 patients were enrolled, of which 32 (33%) developed ARDS, a median of 2 days after starting antimalarial medication (IQR 0-4, range 0-6). Length of stay in ICU and in hospital were significantly longer in patients who developed ARDS: 13 days (IQR 10-18) vs 3 days (IQR 2-5) and 21 days (IQR 15-30.5) vs 7 days (IQR 6-10), respectively. Overall case-fatality ratio in ICU was 4.1% and did not differ between groups. The risk of ARDS development is difficult to establish.

CONCLUSION

ARDS is a hard to predict late complication of severe malaria. A low threshold for ICU admission and monitoring should be used. Ideally patients should be managed in a centre with experience and access to advanced techniques.

Diagnosis of pneumonia and malaria in Nigerian hospitals: A prospective cohort study

BACKGROUND

Pneumonia and malaria are the leading causes of global childhood mortality. We describe the clinical presentation of children diagnosed with pneumonia and/or malaria, and identify possible missed cases and diagnostic predictors.

METHODS

Prospective cohort study involving children (aged 28 days to 15 years) admitted to 12 secondary-level hospitals in south-west Nigeria, from November 2015 to October 2017. We described children diagnosed with malaria and/or pneumonia on admission and identified potential missed cases using WHO criteria. We used logistic regression models to identify associations between clinical features and severe pneumonia and malaria diagnoses.

RESULTS

Of 16 432 admitted children, 16 184 (98.5%) had adequate data for analysis. Two-thirds (10 561, 65.4%) of children were diagnosed with malaria and/or pneumonia by the admitting doctor; 31.5% (567/1799) of those with pneumonia were also diagnosed with malaria. Of 1345 (8.3%) children who met WHO severe pneumonia criteria, 557 (41.4%) lacked a pneumonia diagnosis. Compared with "potential missed" diagnoses of severe pneumonia, children with "detected" severe pneumonia were more likely to receive antibiotics (odds ratio [OR], 4.03; 2.63-6.16, P < .001), and less likely to die (OR, 0.72; 0.51-1.02, P = .067). Of 2299 (14.2%) children who met WHO severe malaria criteria, 365 (15.9%) lacked a malaria diagnosis. Compared with "potential missed" diagnoses of severe malaria, children with "detected" severe malaria were less likely to die (OR, 0.59; 0.38-0.91, P = 0.017), with no observed difference in antimalarial administration (OR, 0.29; 0.87-1.93, P = .374). We identified predictors of severe pneumonia and malaria diagnosis.

CONCLUSION

Pneumonia should be considered in all severely unwell children with respiratory signs, regardless of treatment for malaria or other conditions.

Lung aeration in experimental malaria-associated acute respiratory distress syndrome by SPECT/CT analysis

Malaria-associated acute respiratory distress syndrome (ARDS) is an inflammatory disease causing alveolar-pulmonary barrier lesion and increased vascular permeability characterized by severe hypoxemia. Computed tomography (CT), among other imaging techniques, allows the morphological and quantitative identification of lung lesions during ARDS. This study aims to identify the onset of malaria-associated ARDS development in an experimental model by imaging diagnosis. Our results demonstrated that ARDS-developing mice presented decreased gaseous exchange and pulmonary insufficiency, as shown by the SPECT/CT technique. The pulmonary aeration disturbance in ARDS-developing mice on the 5th day post infection was characterized by aerated tissues decrease and nonaerated tissue accumulation, demonstrating increased vascular permeability and pleural effusion. The SPECT/CT technique allowed the early diagnosis in the experimental model, as well as the identification of the pulmonary aeration. Notwithstanding, despite the fact that this study contributes to better understand lung lesions during malaria-associated ARDS, further imaging studies are needed.