Features and prognosis of severe malaria caused by Plasmodium falciparum, Plasmodium vivax and mixed Plasmodium species in Papua New Guinean children

The biology and pathogenesis of vivax malaria

Plasmodium vivax contributes significantly to global malaria morbidity. Key advances include the discovery of pathways facilitating invasion by P. vivax merozoites of nascent reticulocytes, crucial for vaccine development. Humanized mouse models and hepatocyte culture systems have enhanced understanding of hypnozoite biology. The spleen has emerged as a major reservoir for asexual vivax parasites, replicating in an endosplenic life cycle, and contributing to recurrent and chronic infections, systemic inflammation, and anemia. Splenic accumulation of uninfected red cells is the predominant cause of anemia. Recurring and chronic infections cause progressive anemia, malnutrition, and death in young children in high-transmission regions. Endothelial activation likely contributes to vivax-associated organ dysfunction. The many recent advances in vivax pathobiology should help guide new approaches to prevention and management.

Enhancing Gene Co-Expression Network Inference for the Malaria Parasite Plasmodium falciparum

BACKGROUND

Malaria results in more than 550,000 deaths each year due to drug resistance in the most lethal Plasmodium (P.) species P. falciparum. A full P. falciparum genome was published in 2002, yet 44.6% of its genes have unknown functions. Improving the functional annotation of genes is important for identifying drug targets and understanding the evolution of drug resistance.

RESULTS

Genes function by interacting with one another. So, analyzing gene co-expression networks can enhance functional annotations and prioritize genes for wet lab validation. Earlier efforts to build gene co-expression networks in P. falciparum have been limited to a single network inference method or gaining biological understanding for only a single gene and its interacting partners. Here, we explore multiple inference methods and aim to systematically predict functional annotations for all P. falciparum genes. We evaluate each inferred network based on how well it predicts existing gene-Gene Ontology (GO) term annotations using network clustering and leave-one-out crossvalidation. We assess overlaps of the different networks' edges (gene co-expression relationships), as well as predicted functional knowledge. The networks' edges are overall complementary: 47-85% of all edges are unique to each network. In terms of the accuracy of predicting gene functional annotations, all networks yielded relatively high precision (as high as 87% for the network inferred using mutual information), but the highest recall reached was below 15%. All networks having low recall means that none of them capture a large amount of all existing gene-GO term annotations. In fact, their annotation predictions are highly complementary, with the largest pairwise overlap of only 27%. We provide ranked lists of inferred gene-gene interactions and predicted gene-GO term annotations for future use and wet lab validation by the malaria community.

CONCLUSIONS

The different networks seem to capture different aspects of the P. falciparum biology in terms of both inferred interactions and predicted gene functional annotations. Thus, relying on a single network inference method should be avoided when possible.

SUPPLEMENTARY DATA

Attached.

Vivax malaria: a possible stumbling block for malaria elimination in India

Plasmodium vivax is geographically the most widely dispersed human malaria parasite species. It has shown resilience and a great deal of adaptability. Genomic studies suggest that P. vivax originated from Asia or Africa and moved to the rest of the world. Although P. vivax is evolutionarily an older species than Plasmodium falciparum, its biology, transmission, pathology, and control still require better elucidation. P. vivax poses problems for malaria elimination because of the ability of a single primary infection to produce multiple relapses over months and years. P. vivax malaria elimination program needs early diagnosis, and prompt and complete radical treatment, which is challenging, to simultaneously exterminate the circulating parasites and dormant hypnozoites lodged in the hepatocytes of the host liver. As prompt surveillance and effective treatments are rolled out, preventing primaquine toxicity in the patients having glucose-6-phosphate dehydrogenase (G6PD) deficiency should be a priority for the vivax elimination program. This review sheds light on the burden of P. vivax, changing epidemiological patterns, the hurdles in elimination efforts, and the essential tools needed not just in India but globally. These tools encompass innovative treatments for eliminating dormant parasites, coping with evolving drug resistance, and the development of potential vaccines against the parasite.

Nanotechnology-Based Strategies in Parasitic Disease Management: From Prevention to Diagnosis and Treatment

Parasitic infections are a major global health issue causing significant mortality and morbidity. Despite substantial advances in the diagnostics and treatment of these diseases, the currently available options fall far short of expectations. From diagnosis and treatment to prevention and control, nanotechnology-based techniques show promise as an alternative approach. Nanoparticles can be designed with specific properties to target parasites and deliver antiparasitic medications and vaccines. Nanoparticles such as liposomes, nanosuspensions, polymer-based nanoparticles, and solid lipid nanoparticles have been shown to overcome limitations such as limited bioavailability, poor cellular permeability, nonspecific distribution, and rapid drug elimination from the body. These nanoparticles also serve as nanobiosensors for the early detection and treatment of these diseases. This review aims to summarize the potential applications of nanoparticles in the prevention, diagnosis, and treatment of parasitic diseases such as leishmaniasis, malaria, and trypanosomiasis. It also discusses the advantages and disadvantages of these applications and their market values and highlights the need for further research in this field.

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.

Antibody to Plasmodium falciparum Variant Surface Antigens, var Gene Transcription, and ABO Blood Group in Children With Severe or Uncomplicated Malaria

BACKGROUND

Antibodies to variant surface antigens (VSAs) such as Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) may vary with malaria severity. The influence of ABO blood group on antibody development is not understood.

METHODS

Immunoglobulin G antibodies to VSAs in Papua New Guinean children with severe (n = 41) or uncomplicated (n = 30) malaria were measured by flow cytometry using homologous P falciparum isolates. Isolates were incubated with ABO-matched homologous and heterologous acute and convalescent plasma. RNA was used to assess var gene transcription.

RESULTS

Antibodies to homologous, but not heterologous, isolates were boosted in convalescence. The relationship between antibody and severity varied by blood group. Antibodies to VSAs were similar in severe and uncomplicated malaria at presentation, higher in severe than uncomplicated malaria in convalescence, and higher in children with blood group O than other children. Six var gene transcripts best distinguished severe from uncomplicated malaria, including UpsA and 2 CIDRα1 domains.

CONCLUSIONS

ABO blood group may influence antibody acquisition to VSAs and susceptibility to severe malaria. Children in Papua New Guinea showed little evidence of acquisition of cross-reactive antibodies following malaria. Var gene transcripts in Papua New Guinean children with severe malaria were similar to those reported from Africa.

Short-course, high-dose primaquine regimens for the treatment of liver-stage vivax malaria in children

OBJECTIVES

To assess the pharmacokinetics, safety, and tolerability of two high-dose, short-course primaquine (PQ) regimens compared with standard care in children with Plasmodium vivax infections.

METHODS

We performed an open-label pediatric dose-escalation study in Madang, Papua New Guinea (Clinicaltrials.gov NCT02364583). Children aged 5-10 years with confirmed blood-stage vivax malaria and normal glucose-6-phosphate dehydrogenase activity were allocated to one of three PQ treatment regimens in a stepwise design (group A: 0.5 mg/kg once daily for 14 days, group B: 1 mg/kg once daily for 7 days, and group C: 1 mg/kg twice daily for 3.5-days). The study assessments were completed at each treatment time point and fortnightly for 2 months after PQ administration.

RESULTS

Between August 2013 and May 2018, 707 children were screened and 73 met the eligibility criteria (15, 40, and 16 allocated to groups A, B, and C, respectively). All children completed the study procedures. The three regimens were safe and generally well tolerated. The pharmacokinetic analysis indicated that an additional weight adjustment of the conventionally recommended milligram per kilogram PQ doses is not necessary to ensure the therapeutic plasma concentrations in pediatric patients.

CONCLUSIONS

A novel, ultra-short 3.5-day PQ regimen has potential benefits for improving the treatment outcomes in children with vivax malaria that warrants further investigation in a large-scale clinical trial.

Association between ovalocytosis and Plasmodium infection: a systematic review and meta-analysis

Reports of an association between ovalocytosis and protection against Plasmodium infection are inconsistent. Therefore, we aimed to synthesise the overall evidence of the association between ovalocytosis and malaria infection using a meta-analysis approach. The systematic review protocol was registered with PROSPERO (CRD42023393778). A systematic literature search of the MEDLINE, Embase, Scopus, PubMed, Ovid, and ProQuest databases, from inception to 30 December 2022, was performed to retrieve studies documenting the association between ovalocytosis and Plasmodium infection. The quality of the included studies was assessed using the Newcastle-Ottawa Scale. Data synthesis included a narrative synthesis and a meta-analysis to calculate the pooled effect estimate (log odds ratios [ORs]) and 95% confidence intervals (CIs) using the random-effects model. Our database search retrieved 905 articles, 16 of which were included for data synthesis. Qualitative synthesis revealed that over half of the studies showed no association between ovalocytosis and malaria infections or severity. Furthermore, our meta-analysis demonstrated no association between ovalocytosis and Plasmodium infection (P = 0.81, log OR = 0.06, 95% CI - 0.44 to 0.19, I²: 86.20%; 11 studies). In conclusion, the meta-analysis results demonstrated no association between ovalocytosis and Plasmodium infection. Hence, the role of ovalocytosis in relation to protection against Plasmodium infection or disease severity should be further investigated in larger prospective studies.

Alteration of Platelet Count in Patients with Severe Non-Plasmodium falciparum Malaria: A Systematic Review and Meta-Analysis

The understanding of platelet biology under physiological and pathological conditions like malaria infection is critical importance in the context of the disease outcome or model systems used. The importance of severe thrombocytopenia (platelet count < 50,000 cells (µL) and profound thrombocytopenia (platelet count < 20,000 cells/µL) in malaria patients remains unclear. This study aimed to synthesize evidence regarding the risks of severe and profound thrombocytopenia in patients with severe non-Plasmodium falciparum malaria. Our overall aim was to identify potential indicators of severe non-P. falciparum malaria and the Plasmodium species that cause severe outcomes. This systematic review was registered at the International Prospective Register of Systematic Reviews (PROSPERO) under registration ID CRD42020196541. Studies were identified from previous systematic reviews (n = 5) and the MEDLINE, Scopus, and Web of Science databases from 9 June 2019 to 9 June 2020. Studies were included if they reported the outcome of severe non-Plasmodium species infection, as defined by the World Health Organization (WHO) criteria, in patients with known platelet counts and/or severe and profound thrombocytopenia. The risk of bias was assessed using the Newcastle–Ottawa Scale (NOS). Data were pooled, and pooled prevalence (PP) and pooled odds ratios (ORs) were calculated using random effects models. Of the 118 studies identified from previous meta-nalyses, 21 met the inclusion criteria. Of the 4807 studies identified from the databases, three met the inclusion criteria. Nine studies identified from reference lists and other sources also met the inclusion criteria. The results of 33 studies reporting the outcomes of patients with severe P. vivax and P. knowlesi infection were pooled for meta-analysis. The PP of severe thrombocytopenia (reported in 21 studies) was estimated at 47% (95% confidence interval (CI): 33–61%, I2: 96.5%), while that of profound thrombocytopenia (reported in 13 studies) was estimated at 20% (95% CI: 14–27%, 85.2%). The pooled weighted mean difference (WMD) in platelet counts between severe uncomplicated Plasmodium infections (reported in 11 studies) was estimated at −28.51% (95% CI: −40.35–61%, I2: 97.7%), while the pooled WMD in platelet counts between severe non-Plasmodium and severe P. falciparum infections (reported in eight studies) was estimated at −3.83% (95% CI: −13.90–6.25%, I2: 85.2%). The pooled OR for severe/profound thrombocytopenia comparing severe to uncomplicated Plasmodium infection was 2.92 (95% CI: 2.24–3.81, I2: 39.9%). The PP of death from severe and profound thrombocytopenia was estimated at 11% (95% CI: 0–22%). These results suggest that individuals with severe non-P. falciparum infection (particularly P. vivax and P. knowlesi) who exhibit severe or profound thrombocytopenia should be regarded as high risk, and should be treated for severe malaria according to current WHO guidelines. In addition, severe or profound thrombocytopenia coupled with other clinical and microscopic parameters can significantly improve malaria diagnosis, enhance the timely treatment of malaria infections, and reduce the morbidity and mortality of severe non-P. falciparum malaria.

Antimalarials for children with Plasmodium vivax infection: Current status, challenges, and research priorities

The aim of this narrative review is to summarise efficacy and pharmacokinetic data for Plasmodium vivax in children. The burden of P. vivax malaria in children continues to remain a significant public health issue, and the need for improved treatment regimens for this vulnerable population is critical. Relapse after re-activation of dormant liver-stage hypnozoites poses additional challenges for treatment, elimination, and control strategies for P. vivax. Whilst it is recognised that paediatric pharmacology may be significantly influenced by anatomical and physiological changes of childhood, dosing regimens often continue to be extrapolated from adult data, highlighting the need for antimalarial dosing in children to be evaluated in early phase clinical trials. This will ensure that globally recommended treatment regimens do not result in suboptimal dosing in children. Furthermore, the development of affordable paediatric formulations to enhance treatment acceptability and widespread G6PD testing to facilitate use of anti-hypnozoite treatment such as primaquine and tafenoquine, should be further prioritised. As the world prepares for malaria elimination, a renewed focus on P. vivax malaria provides an ideal opportunity to harness momentum and ensure that all populations, including children have access to safe, efficacious, and correctly dosed antimalarial therapies.

Etiology of lactic acidosis in malaria

Lactic acidosis and hyperlactatemia are common metabolic disturbances in patients with severe malaria. Lactic acidosis causes physiological adverse effects, which can aggravate the outcome of malaria. Despite its clear association with mortality in malaria patients, the etiology of lactic acidosis is not completely understood. In this review, the possible contributors to lactic acidosis and hyperlactatemia in patients with malaria are discussed. Both increased lactate production and impaired lactate clearance may play a role in the pathogenesis of lactic acidosis. The increased lactate production is caused by several factors, including the metabolism of intraerythrocytic Plasmodium parasites, aerobic glycolysis by activated immune cells, and an increase in anaerobic glycolysis in hypoxic cells and tissues as a consequence of parasite sequestration and anemia. Impaired hepatic and renal lactate clearance, caused by underlying liver and kidney disease, might further aggravate hyperlactatemia. Multiple factors thus participate in the etiology of lactic acidosis in malaria, and further investigations are required to fully understand their relative contributions and the consequences of this major metabolic disturbance.

Therapeutically-rational exchange (T-REX) of Gerbich-negative red blood cells can be evaluated in Papua New Guinea as "a rescue adjunct" for patients with Plasmodium falciparum malaria

"Conventional exchange transfusion"-that delivers nondescript "standard issue" units of red blood cells (RBCs)-is used worldwide to rescue dying Plasmodium falciparum (Pf) malaria patients. Recently, exchanging special malaria-resistant RBCs (T-REX) has been recommended to prevent random delivery of malaria-susceptible RBCs that promote Pf infection. Fortunately, Papua New Guinea (PNG) is well positioned to help optimize exchange as "a rescue adjunct" because (a) Gerbich-negative (GN) RBCs that resist Pf invasion are prevalent in PNG; (b) with international support, PNG has conducted outstanding malaria research; (c) PNG's scientists feel studies of GN RBCs can advance malaria therapeutics; and (d) with blood-bank support, evaluating exchange of GN RBCs is feasible in PNG. An exchange-transfusion study of GN RBCs might attract international sponsorship given the threat of expanding drug-resistance as well as growing recognition that advancing transfusion medicine and expanding blood donation could especially help Pf-infected children-immediately.

Neurological complications in patients with Plasmodium vivax malaria from Karachi, Pakistan

BACKGROUND

Malaria remains an endemic disease in Pakistan with an estimated healthcare burden of 1.6 million cases annually, with Plasmodium vivax accounting for 67% of reported cases. P. vivax is the most common species causing malaria outside of Africa, with approximately 13.8 million reported cases worldwide.

METHOD

We report a series of P. vivax cases with cerebral involvement that presented at Aga Khan University Hospital, Karachi, Pakistan.

RESULTS

The majority of the patients presented with high-grade fever accompanied by projectile vomiting and abnormal behaviour, seizures, shock and unconsciousness. Seven of 801 patients with P. vivax monoinfection presented or developed cerebral complications. P. vivax infections were diagnosed based on peripheral smears and rapid diagnostic testing.

CONCLUSION

P. vivax infection can lead to severe complications, although not with the frequency of Plasmodium falciparum infection. Current cases highlight an increasing trend of cerebral complications caused by P. vivax.

Acquisition of Antibodies Against Endothelial Protein C Receptor-Binding Domains of Plasmodium falciparum Erythrocyte Membrane Protein 1 in Children with Severe Malaria

BACKGROUND

Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) mediates parasite sequestration in postcapillary venules in P. falciparum malaria. PfEMP1 types can be classified based on their cysteine-rich interdomain region (CIDR) domains. Antibodies to different PfEMP1 types develop gradually after repeated infections as children age, and antibodies to specific CIDR types may confer protection.

METHODS

Levels of immunoglobulin G to 35 recombinant CIDR domains were measured by means of Luminex assay in acute-stage (baseline) and convalescent-stage plasma samples from Papua New Guinean children with severe or uncomplicated malaria and in healthy age-matched community controls.

RESULTS

At baseline, antibody levels were similar across the 3 groups. After infection, children with severe malaria had higher antibody levels than those with uncomplicated malaria against the endothelial protein C receptor (EPCR) binding CIDRα1 domains, and this difference was largely confined to older children. Antibodies to EPCR-binding domains increased from presentation to follow-up in severe malaria, but not in uncomplicated malaria.

CONCLUSIONS

The acquisition of antibodies against EPCR-binding CIDRα1 domains of PfEMP1 after a severe malaria episode suggest that EPCR-binding PfEMP1 may have a role in the pathogenesis of severe malaria in Papua New Guinea.

Contribution of Malaria to Inhospital Mortality in Papua New Guinean Children from a Malaria-Endemic Area: A Prospective Observational Study

We aimed to identify clinical and laboratory predictors of mortality in children from a malaria-endemic area of Papua New Guinea hospitalized for severe illness. Children aged 0.5-10 years presenting with any WHO-defined feature of severe malarial illness were eligible for recruitment. Each child was assessed with a detailed clinical examination, blood film microscopy, malaria rapid diagnostic testing (RDT), a full blood examination, and blood glucose and lactate concentrations. Clinical care was coordinated by local medical staff in accordance with national guidelines. Daily study assessments were conducted until death or discharge. Other biochemical tests and malaria polymerase chain reaction (PCR) tests were performed subsequently. Logistic regression identified independent predictors of death. Of 787 evaluable children with severe illness, 336 had confirmed severe malaria (microscopy and PCR positive) and 58 (6.6%) died during hospitalization. The independent predictors of mortality were hyperlactatemia (adjusted odds ratio [95% CI]: 2.85 [1.24-6.41], P = 0.01), malnutrition (2.92 [1.36-6.23], P = 0.005), renal impairment (3.85 [1.53-9.24], P = 0.002), plasma albumin (0.93 [0.88-0.98] for a 1 g/L increase, P = 0.004), and Blantyre coma score (BCS) ≤ 2 (10.3 [4.77-23.0] versus a normal BCS, P < 0.0001). Confirmed severe malaria (0.11 [0.03-0.30] versus non-malarial severe illness, P < 0.0001) was independently associated with lower mortality. Although established risk factors were evident, malaria was inversely associated with mortality. This highlights the importance of accurate diagnosis through blood film microscopy, RDTs, and, if available, PCR to both guide management and provide valid epidemiological data.

Antibody Targets on the Surface of Plasmodium falciparum-Infected Erythrocytes That Are Associated With Immunity to Severe Malaria in Young Children

BACKGROUND

Sequestration of Plasmodium falciparum-infected erythrocytes (IEs) in the microvasculature contributes to pathogenesis of severe malaria in children. This mechanism is mediated by antigens expressed on the IE surface. However, knowledge of specific targets and functions of antibodies to IE surface antigens that protect against severe malaria is limited.

METHODS

Antibodies to IE surface antigens were examined in a case-control study of young children in Papua New Guinea presenting with severe or uncomplicated malaria (n = 448), using isolates with a virulent phenotype associated with severe malaria, and functional opsonic phagocytosis assays. We used genetically modified isolates and recombinant P. falciparum erythrocyte membrane protein 1 (PfEMP1) domains to quantify PfEMP1 as a target of antibodies associated with disease severity.

RESULTS

Antibodies to the IE surface and recombinant PfEMP1 domains were significantly higher in uncomplicated vs severe malaria and were boosted following infection. The use of genetically modified P. falciparum revealed that PfEMP1 was a major target of antibodies and that PfEMP1-specific antibodies were associated with reduced odds of severe malaria. Furthermore, antibodies promoting the opsonic phagocytosis of IEs by monocytes were lower in those with severe malaria.

CONCLUSIONS

Findings suggest that PfEMP1 is a dominant target of antibodies associated with reduced risk of severe malaria, and function in part by promoting opsonic phagocytosis.

Severe thrombocytopaenia in patients with vivax malaria compared to falciparum malaria: a systematic review and meta-analysis

Background

Plasmodium vivax is the most geographically widespread species among human malaria parasites. Immunopathological studies have shown that platelets are an important component of the host innate immune response against malaria infections. The objectives of this study were to quantify thrombocytopaenia in P. vivax malaria patients and to determine the associated risks of severe thrombocytopaenia in patients with vivax malaria compared to patients with P. falciparum malaria.

Main body

A systematic review and meta-analysis of the available literature on thrombocytopaenia in P. vivax malaria patients was undertaken. Relevant studies in health-related electronic databases were identified and reviewed. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. Fifty-eight observational studies (n = 29 664) were included in the current review. Severe thrombocytopaenia (< 50 000/mm³) to very severe thrombocytopaenia (< 20 000/mm³) was observed in 10.1% of patients with P. vivax infection. A meta-analysis of 11 observational studies showed an equal risk of developing severe/very severe thrombocytopaenia between the patients with P. vivax malaria and those with P. falciparum malaria (OR: 1.98, 95% CI: 0.92–4.25). This indicates that thrombocytopaenia is as equally a common manifestation in P. vivax and P. falciparum malaria patients. One study showed a higher risk of developing very severe thrombocytopaenia in children with severe P. vivax malaria than with severe P. falciparum malaria (OR: 2.80, 95% CI: 1.48–5.29). However, a pooled analysis of two studies showed an equal risk among adult severe cases (OR: 1.19, 95% CI: 0.51–2.77). This indicates that the risk of developing thrombocytopaenia in P. vivax malaria can vary with immune status in both children and adults. One study reported higher levels of urea and serum bilirubin in patients with P. vivax malaria and severe thrombocytopaenia compared with patients mild thrombocytopaenia or no thrombocytopaenia, (P < 0.001 in all comparisons). A pooled analysis of two other studies showed a similar proportion of bleeding episodes with thrombocytopaenia in severe P. vivax patients and severe P. falciparum patients (P = 0.09). This implied that both P. vivax and P. falciparum infections could present with bleeding episodes, if there had been a change in platelet counts in the infected patients. A pooled analysis of another two studies showed an equal risk of mortality with severe thrombocytopaenia in both P. vivax and P. falciparum malaria patients (OR: 1.16, 95% CI: 0.30–4.60). However, due to the low number of studies with small sample sizes within the subset of studies that provided clinically relevant information, our confidence in the estimates is limited.

Conclusion

The current review has provided some evidence of the clinical relevance of severe thrombocytopaenia in P. vivax malaria. To substantiate these findings, there is a need for well designed, large-scale, prospective studies among patients infected with P. vivax. These should include patients from different countries and epidemiological settings with various age and gender groups represented.

Electronic supplementary material

The online version of this article (10.1186/s40249-018-0392-9) contains supplementary material, which is available to authorized users.

Are respiratory complications of Plasmodium vivax malaria an underestimated problem?

BACKGROUND

Respiratory complications are uncommon, but often life-threatening features of Plasmodium vivax malaria. This study aimed to estimate the prevalence and lethality associated with such complications among P. vivax malaria patients in a tertiary hospital in the Western Brazilian Amazon, and to identify variables associated with severe respiratory complications, intensive care need and death. Medical records from 2009 to 2016 were reviewed aiming to identify all patients diagnosed with P. vivax malaria and respiratory complications. Prevalence, lethality and risk factors associated with WHO defined respiratory complications, intensive care need and death were assessed.

RESULTS

A total of 587 vivax malaria patients were hospitalized during the study period. Thirty (5.1%) developed respiratory complications. Thirteen (43.3%) developed severe respiratory complications, intensive care was required for 12 (40%) patients and 5 (16.6%) died. On admission, anaemia and thrombocytopaenia were common findings, whereas fever was unusual. Patients presented different classes of parasitaemia and six were aparasitaemic on admission. Time to respiratory complications occurred after anti-malarials administration in 18 (60%) patients and progressed very rapidly. Seventeen patients (56.7%) had comorbidities and/or concomitant conditions, which were significantly associated to higher odds of developing severe respiratory complications, need for intensive care and death (p < 0.05).

CONCLUSION

Respiratory complications were shown to be associated with significant mortality in this population. Patients with comorbidities and/or concomitant conditions require special attention to avoid this potential life-threatening complication.

Cost-effectiveness of artemisinin-naphthoquine versus artemether-lumefantrine for the treatment of uncomplicated malaria in Papua New Guinean children

BACKGROUND

A recent randomized trial showed that artemisinin-naphthoquine (AN) was non-inferior to artemether-lumefantrine (AL) for falciparum malaria and superior for vivax malaria in young Papua New Guinean children. The aim of this study was to compare the cost-effectiveness of these two regimens.

METHODS

An incremental cost-effectiveness analysis was performed using data from 231 children with Plasmodium falciparum and/or Plasmodium vivax infections in an open-label, randomized, parallel-group trial. Recruited children were randomized 1:1 to receive once daily AN for 3 days with water or twice daily AL for 3 days given with fat. World Health Organisation (WHO) definitions were used to determine clinical/parasitological outcomes. The cost of transport between the home and clinic, plus direct health-care costs, served as a basis for determining each regimen's incremental cost per incremental treatment success relative to AL by Day 42 and its cost per life year saved.

RESULTS

In the usual care setting, AN was more effective for the treatment of uncomplicated malaria in children aged 0.5-5.9 years. AL and AN were equally efficacious for the treatment of falciparum malaria, however AN had increased anti-malarial treatment costs per patient of $10.46, compared with AL. AN was the most effective regimen for treatment of vivax malaria, but had increased treatment costs of $14.83 per treatment success compared with AL.

CONCLUSIONS

Whilst AN has superior overall efficacy for the treatment of uncomplicated malaria in PNG children, AL was the less costly regimen. An indicative extrapolation estimated the cost per life year saved by using AN instead of AL to treat uncomplicated malaria to be $12,165 for girls and $12,469 for boys (discounted), which means AN may not be cost-effective and affordable for PNG at current cost. However, AN may become acceptable should it become WHO prequalified and/or should donated/subsidized drug supply become available.

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.

Pattern of malaria in hospitalized children in Khartoum state

Malaria remains a major health problem in Sudan with significant morbidity and mortality particularly in children. We prospectively studied children with malaria admitted to an Emergency Department in Khartoum (August-November 2014). Malaria diagnosis was based on a positive blood smear and rapid diagnostic test. The aim was to study the clinical and laboratory features and short-term outcome of malaria among hospitalized children. Data collected from 112 children (males; 56.3%) who fulfilled the criteria for diagnosis of malaria of whom 72.3% had severe malaria and 27.7% uncomplicated malaria (UM). The mean age was 69.2 ± 54.5 months. Hyperparasitemia was detected in 53% of positive blood smears. Plasmodium falciparum was detected in 69.4%, P. vivax in 26.5%, and mixed species in 4.1%. The risk of severe malaria was significantly higher in patients with hyperparasitemia and P. vivax infection (P = 0.001 and P = 0.014 respectively). Severe malaria cases had significantly higher prevalence of thrombocytopenia and lower mean platelet count than those with UM, P = 0.001 each. Serious complications of severe malaria were cerebral malaria, severe malaria anaemia and acute kidney injury (AKI). The overall case fatality rate was 5.3% and that from severe disease was 4.9%. All deaths were among <60 months-olds and were due to P. falciparum infection with AKI being the only significant risk factor for death (P = 0.045). In Khartoum state, UM is still an important cause of morbidity in children. P. vivax has emerged as a causative species of severe malaria. The lower mortality rate of malaria probably reflects improvement in health care.

Demographic and clinical profiles of Plasmodium falciparum and Plasmodium vivax patients at a tertiary care centre in southwestern India

Background

Malaria remains an important cause of morbidity and mortality in India. Though many comprehensive studies have been carried out in Africa and Southeast Asia to characterize and examine determinants of Plasmodium falciparum and Plasmodium vivax malaria pathogenesis, fewer have been conducted in India.

Methods

A prospective study of malaria-positive individuals was conducted at Goa Medical College and Hospital (GMC) from 2012 to 2015 to identify demographic, diagnostic and clinical indicators associated with P. falciparum and P. vivax infection on univariate analysis.

Results

Between 2012 and 2015, 74,571 febrile individuals, 6287 (8.4%) of whom were malaria positive, presented to GMC. The total number of malaria cases at GMC increased more than two-fold over four years, with both P. vivax and P. falciparum cases present year-round. Some 1116 malaria-positive individuals (mean age = 27, 91% male), 88.2% of whom were born outside of Goa and 51% of whom were construction workers, were enroled in the study. Of 1088 confirmed malaria-positive patients, 77.0% had P. vivax, 21.0% had P. falciparum and 2.0% had mixed malaria. Patients over 40 years of age and with P. falciparum infection were significantly (p < 0.001) more likely to be hospitalised than younger and P. vivax patients, respectively. While approximately equal percentages of hospitalised P. falciparum (76.6%) and P. vivax (78.9%) cases presented with at least one WHO severity indicator, a greater percentage of P. falciparum inpatients presented with at least two (43.9%, p < 0.05) and at least three (29.9%, p < 0.01) severity features. There were six deaths among the 182 hospitalised malaria positive patients, all of whom had P. falciparum.

Conclusion

During the four year study period at GMC, the number of malaria cases increased substantially and the greatest burden of severe disease was contributed by P. falciparum.

The Burden of Child Maltreatment Leading to Hospitalization in a Provincial Setting in Papua New Guinea

INTRODUCTION

Child maltreatment is prevalent globally. In Papua New Guinea (PNG), child maltreatment remains an under-reported problem.

METHODS

As part of a 10 month prospective observational study conducted at Modilon Hospital in PNG, we investigated the burden of child maltreatment in the form of sexual abuse, physical abuse and neglect, leading to hospitalization in children ≤14 years.

RESULTS

Of 1061 screened admissions, 107 (10%) fulfilled the definition of child maltreatment. The in-hospital admission prevalence of sexual abuse was 5.7% [60 of 1061; 95% confidence interval (CI): 4.4-7.3]. Neglect accounted for 3.4% (36 of 1061; 95% CI: 2.4-4.7) of admissions, while physical abuse accounted for 1.0% (11 of 1061; 95% CI: 0.6-1.9). Mortality was highest in the neglected group, with severe acute malnutrition accounting for 89% of deaths.

CONCLUSION

Improved awareness, establishment of appropriate channels for addressing child maltreatment and enforcement of child protection laws in PNG and other epidemiologically similar settings are urgently needed.

Plasmodium vivax infection: a major determinant of severe anaemia in infancy

BACKGROUND

Most malarious countries outside of Africa are co-endemic for Plasmodium falciparum and Plasmodium vivax. The comparative burden of anaemia in the community caused by these two species is incompletely characterized.

METHODS

A three-stage, cross-sectional, community survey was used to determine the proportion of moderate or severe anaemia (haemoglobin <7 g/dL) attributable to patent P. vivax, P. falciparum and mixed parasitaemia in Papua, Indonesia. Adjusted population-attributable fractions were calculated from multivariable logistic regression models. Eight hundred and twenty-five households were surveyed with a total of 5255 occupants, 3890 (74 %) of whom were present and provided a blood sample. Plasmodium falciparum parasitaemia was present in 8.1 % (n = 315) of participants, P. vivax in 6.4 % (n = 250) and mixed infections in 1.9 % (n = 72). Overall, P. falciparum was associated with a mean reduction in haemoglobin of 1.16 g/dL compared to those without patent parasitaemia [95 % confidence interval (95 % CI) 0.91, 1.41 g/dL]. The corresponding values for P. vivax and mixed infections were 0.66 g/dL (95 % CI 0.35, 0.96) and 1.25 g/dL (0.71, 1.80), respectively. Overall, 16.7 % (95 % CI 8.52, 24.2 %) of haemoglobin concentrations <7 g/dL in the community were estimated to be attributable to patent parasitaemia. The fractions for infants and 1-5 years old were 34.4 % (95 % CI -3.30, 58.3 %) and 23.2 % (95 % CI 3.34, 39.0 %), respectively. Plasmodium vivax was associated with a greater than threefold higher attributable fraction of anaemia in infants compared with P. falciparum [27.6 % (95 % CI -3.20, 49.2 %) versus 7.94 % (-5.87, 20.0 %)].

CONCLUSION

Despite comparatively low-level endemicity, malaria is associated with a significant proportion of all cases of community anaemia in southern Papua. Contrary to its benign reputation, P. vivax is an important and preventable risk factor for anaemia during infancy-a probable consequence of relapsing disease prior to the development of immunity.

Severe Malaria Associated with Plasmodium falciparum and P. vivax among Children in Pawe Hospital, Northwest Ethiopia

Despite rigorous effort made to control malaria for more than a century, it is still among the main public health problems in least developed regions of the world. Majority of deaths associated with malaria occur in sub-Sahara Africa among biologically risked groups. Thus, this study was designed to assess the incidence of severe malaria syndromes among children in Pawe Hospital, Northwest Ethiopia. Children seeking medication for malaria infection in Pawe Hospital during the study period were recruited. Sociodemographic characteristics, physical, hematological, and clinical features of complicated malaria were assessed following standard parasitological and clinical procedures. A total of 263 children were found malaria positive. Among these, 200 were infected with Plasmodium falciparum. Most of the severe malaria symptoms were observed among children infected with P. falciparum and P. vivax. The study showed that significant number of the children developed severe life threatening malaria complications. This calls for prompt early diagnosis and effective treatment of patients to reduce mortality and complications associated with malaria in the study site.

A Toll-like receptor-1 variant and its characteristic cellular phenotype is associated with severe malaria in Papua New Guinean children

Genetic factors are likely to contribute to low severe malaria case fatality rates in Melanesian populations, but association studies can be underpowered and may not provide plausible mechanistic explanations if significant associations are detected. In preparation for a genome-wide association study, 29 candidate single-nucleotide polymorphisms (SNPs) with minor allele frequencies >5% were examined in a case-control study of 504 Papua New Guinean children with severe malaria. In parallel, an immunological substudy was performed on convalescent peripheral blood mononuclear cells (PBMCs) from cases and controls. Following stimulation with a Toll-like receptor (TLR) 1/2 agonist, effector cytokines and chemokines were assayed. The only significant genetic association observed involved a nonsynonymous SNP (TLR1rs4833095) in the TLR1 gene. A recessive (TT) genotype was associated with reduced odds of severe malaria of 0.52 (95% confidence interval (0.29-0.90), P=0.006). Concentrations of pro-inflammatory cytokines interleukin-1β and tumour necrosis factor α were significantly higher in severe malaria cases compared with healthy controls, but lower in children with the protective recessive (TT) genotype. A genetic variant in TLR1 may contribute to the low severe malaria case fatality rates in this region through a reduced pro-inflammatory cellular phenotype.

Ultrasonographic assessment of splenic volume at presentation and after anti-malarial therapy in children with malarial anaemia

Background

Splenic enlargement is a component of the host response to malaria and may also influence the genesis and progression of malarial anaemia. Few cross-sectional and no longitudinal studies have assessed the relationship between splenic volume measured ultrasonographically and haemoglobin concentrations in children with malaria.

Methods

Fifteen Papua New Guinean children with severe malarial anaemia (SMA; haemoglobin <50 g/L) and ten with moderate malarial anaemia (MMA; 51–99 g/L) were recruited. The SMA patients were given intramuscular artemether followed by oral artemisinin combination therapy (ACT), and were transfused one unit of packed cells 0.3-4.0 days post-admission. The MMA patients were treated with ACT. Splenic enlargement (Hackett’s grade, subcostal distance and ultrasonographically determined volume) and haemoglobin concentrations were measured on days 0, 1, 2, 3, 7, 14, 28, and 42.

Results

Associations between Hackett’s grade, subcostal distance and splenic volume were modest (r_s ≤ 0.62, P <0.001). Baseline splenic volume was not associated with age or haemoglobin (P ≥0.90). Mean splenic volume had fallen by approximately 50 % at day 14 in children with MMA (P ≤0.011 vs days 0, 1 and 2), but there was no change in the SMA group (P ≥0.30). There was no change in haemoglobin in the MMA group during follow-up but a rise in the SMA group to day 7 (P ≤0.05 vs days 0, 1, 2, and 3) which paralleled the packed cell volume transfused.

Conclusions

Clinical assessment of splenomegaly is imprecise compared with ultrasonography. Serial splenic volumes and haemoglobin concentrations suggest that the spleen does not influence post-treatment haemoglobin, including after transfusion.

Burden of complicated malaria in a densely forested Bastar region of Chhattisgarh State (Central India)

BACKGROUND

A prospective study on severe and complicated malaria was undertaken in the tribal dominated area of Bastar division, Chhattisgarh (CG), Central India, with an objective to understand the clinical epidemiology of complicated malaria in patients attending at a referral hospital.

METHODS

Blood smears, collected from the general medicine and pediatric wards of a government tertiary health care facility located in Jagdalpur, CG, were microscopically examined for malaria parasite from July 2010 to December 2013. The Plasmodium falciparum positive malaria cases who met enrollment criteria and provided written informed consent were enrolled under different malaria categories following WHO guidelines. PCR was performed to reconfirm the presence of P.falciparum mono infection among enrolled cases. Univariate and multivariate logistic regression analysis was done to identify different risk factors using STATA 11.0.

RESULTS

A total of 40,924 cases were screened for malaria. The prevalence of malaria and P.falciparum associated complicated malaria (severe and cerebral both) in the hospital was 6% and 0.81%, respectively. P.falciparum malaria prevalence, severity and associated mortality in this region peaked at the age of > 4-5 years and declined with increasing age. P.falciparum malaria was significantly more prevalent in children than adults (P < 0.00001). Among adults, males had significantly more P.falciparum malaria than females (P < 0.00001). Case fatality rate due to cerebral malaria and severe malaria was, respectively, 32% and 9% among PCR confirmed mono P.falciparum cases. Coma was the only independent predictor of mortality in multivariate regression analysis. Mortality was significantly associated with multi-organ complication score (P = 0.0003).

CONCLUSION

This study has revealed that the pattern of morbidity and mortality in this part of India is very different from earlier reported studies from India. We find that the peak morbidity and mortality in younger children regardless of seasonality. This suggests that this age group needs special care for control and clinical management.

The clinical and public health problem of relapse despite primaquine therapy: case review of repeated relapses of Plasmodium vivax acquired in Papua New Guinea

BACKGROUND

Primaquine is the only drug available for preventing relapse following a primary attack by Plasmodium vivax malaria. This drug imposes several important problems: daily dosing over two weeks; toxicity in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency; partner blood schizontocides possibly impacting primaquine safety and efficacy; cytochrome P-450 abnormalities impairing metabolism and therapeutic activity; and some strains of parasite may be tolerant or resistant to primaquine. There are many possible causes of repeated relapses in a patient treated with primaquine.

CASE DESCRIPTION

A 56-year-old Caucasian woman from New Zealand traveled to New Ireland, Papua New Guinea for two months in 2012. One month after returning home she stopped daily doxycycline prophylaxis against malaria, and one week later she became acutely ill and hospitalized with a diagnosis of Plasmodium vivax malaria. Over the ensuing year she suffered four more attacks of vivax malaria at approximately two-months intervals despite consuming primaquine daily for 14 days after each of those attacks, except the last. Genotype of the patient's cytochrome P-450 2D6 alleles (*5/*41) corresponded with an intermediate metabolizer phenotype of predicted low activity.

DISCUSSION

Multiple relapses in patients taking primaquine as prescribed present a serious clinical problem, and understanding the basis of repeated therapeutic failure is a challenging technical problem. This case highlights these issues in a single traveler, but these problems will also arise as endemic nations approach elimination of malaria transmission.

Artemisinin-naphthoquine versus artemether-lumefantrine for uncomplicated malaria in Papua New Guinean children: an open-label randomized trial

BACKGROUND

Artemisinin combination therapies (ACTs) with broad efficacy are needed where multiple Plasmodium species are transmitted, especially in children, who bear the brunt of infection in endemic areas. In Papua New Guinea (PNG), artemether-lumefantrine is the first-line treatment for uncomplicated malaria, but it has limited efficacy against P. vivax. Artemisinin-naphthoquine should have greater activity in vivax malaria because the elimination of naphthoquine is slower than that of lumefantrine. In this study, the efficacy, tolerability, and safety of these ACTs were assessed in PNG children aged 0.5-5 y.

METHODS AND FINDINGS

An open-label, randomized, parallel-group trial of artemether-lumefantrine (six doses over 3 d) and artemisinin-naphthoquine (three daily doses) was conducted between 28 March 2011 and 22 April 2013. Parasitologic outcomes were assessed without knowledge of treatment allocation. Primary endpoints were the 42-d P. falciparum PCR-corrected adequate clinical and parasitologic response (ACPR) and the P. vivax PCR-uncorrected 42-d ACPR. Non-inferiority and superiority designs were used for falciparum and vivax malaria, respectively. Because the artemisinin-naphthoquine regimen involved three doses rather than the manufacturer-specified single dose, the first 188 children underwent detailed safety monitoring. Of 2,542 febrile children screened, 267 were randomized, and 186 with falciparum and 47 with vivax malaria completed the 42-d follow-up. Both ACTs were safe and well tolerated. P. falciparum ACPRs were 97.8% and 100.0% in artemether-lumefantrine and artemisinin-naphthoquine-treated patients, respectively (difference 2.2% [95% CI -3.0% to 8.4%] versus -5.0% non-inferiority margin, p = 0.24), and P. vivax ACPRs were 30.0% and 100.0%, respectively (difference 70.0% [95% CI 40.9%-87.2%], p<0.001). Limitations included the exclusion of 11% of randomized patients with sub-threshold parasitemias on confirmatory microscopy and direct observation of only morning artemether-lumefantrine dosing.

CONCLUSIONS

Artemisinin-naphthoquine is non-inferior to artemether-lumefantrine in PNG children with falciparum malaria but has greater efficacy against vivax malaria, findings with implications in similar geo-epidemiologic settings within and beyond Oceania.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry ACTRN12610000913077. Please see later in the article for the Editors' Summary.

Prevalence of patients with acute febrile illnesses and positive dengue NS1 tests in a tertiary hospital in Papua New Guinea

Because the prevalence of dengue fever in urban settings in Papua New Guinea is unknown, we investigated the presence of dengue using the NS1 antigen test in an outpatient-based prospective observational study at Port Moresby General Hospital. Of 140 patients with acute febrile illnesses, dengue fever was diagnosed in 14.9% (20 of 134; 95% confidence interval [95% CI] = 9.6-22.4). Malaria (2 of 137; 1.5%; 95% CI = 0.3-5.7), chikungunya (3 of 140; 2.1%; 95% CI = 0.6-6.6), and bacterial bloodstream infections (0 of 80; 0%; 95% CI = 0-5.7) were uncommon. Dengue fever should no longer be considered rare in Papua New Guinea.

Plasmodium falciparum, but not P. vivax, can induce erythrocytic apoptosis

Background

Apoptosis can occur in red blood cells (RBC) and seems to be involved in hematologic disorders related to many diseases. In malaria it is known that parasitized RBC (pRBC) is involved in the development of anemia and thrombosis; however, non-parasitized RBC (nRBC) apoptosis could amplify these malaria-associated hematologic events. In fact, in experimental malaria, increased levels of apoptosis were observed in nRBC during lethal Plasmodium yoelii 17XL infection, but in human malaria erythrocytic apoptosis has never been studied. The present study was performed to investigate if nRBC apoptosis also occurs in P. vivax and P. falciparum infections.

Findings

Apoptosis of nRBC was evaluated in blood samples of P. vivax malaria patients and clinically healthly individuals living in Manaus, Brazil, both ex vivo and after incubation of RBC for 24 h. Additionally, the capacity of plasma from P. vivax or P. falciparum patients was tested for induction of in vitro apoptosis of normal RBC from a clinically healthy individual living in a non-endemic malaria region. Apoptosis was detected by flow cytometry using annexin V staining. In contrast to experimental malaria that significantly increased the levels of apoptotic nRBC both ex-vivo and after 24 h of incubation, no significant alteration on apoptotic nRBC rates was detected in P. vivax infected patients when compared with non-infected control individuals. Similar results were observed when plasma of these P. vivax patients was incubated with normal RBC. Conversely, plasma from P. falciparum-infected subjects induced significant apoptosis of these cells.

Conclusions

Apoptosis of normal RBC can be induced by plasma from individuals with P. falciparum (but not with P. vivax) malaria. This finding could reflect the existence of erythrocytic apoptosis during infection that could contribute to the pathogenesis of hematological and vascular complications associated with falciparum malaria.

Is Plasmodium vivax malaria a severe malaria?: a systematic review and meta-analysis

Background

Plasmodium vivax is one of the major species of malaria infecting humans. Although emphasis on P. falciparum is appropriate, the burden of vivax malaria should be given due attention. This study aimed to synthesize the evidence on severe malaria in P. vivax infection compared with that in P. falciparum infection.

Methods/Principal Findings

We searched relevant studies in electronic databases. The main outcomes required for inclusion in the review were mortality, severe malaria (SM) and severe anaemia (SA). The methodological quality of the included studies was assessed using the Newcastle-Ottawa Scale. Overall, 26 studies were included. The main meta-analysis was restricted to the high quality studies. Eight studies (n = 27490) compared the incidence of SM between P. vivax infection and P. falciparum mono-infection; a comparable incidence was found in infants (OR: 0.45, 95% CI:0.04–5.68, I²:98%), under 5 year age group (OR: 2.06, 95% CI: 0.83–5.1, I²:83%), the 5–15 year-age group (OR: 0.6, 95% CI: 0.31–1.16, I²:81%) and adults (OR: 0.83, 95% CI: 0.67–1.03, I²:25%). Six studies reported the incidences of SA in P. vivax infection and P. falciparum mono-infection; a comparable incidence of SA was found among infants (OR: 3.47, 95%:0.64–18.94, I²: 92%), the 5–15 year-age group (OR:0.71, 95% CI: 0.06–8.57, I²:82%). This was significantly lower in adults (OR:0.75, 95% CI: 0.62–0.92, I²:0%). Five studies (n = 71079) compared the mortality rate between vivax malaria and falciparum malaria. A lower rate of mortality was found in infants with vivax malaria (OR:0.61, 95% CI:0.5–0.76, I²:0%), while this was comparable in the 5–15 year- age group (OR: 0.43, 95% CI:0.06–2.91, I²:84%) and the children of unspecified-age group (OR: 0.77, 95% CI:0.59–1.01, I²:0%).

Conclusion

Overall, the present analysis identified that the incidence of SM in patients infected with P. vivax was considerable, indicating that P. vivax is a major cause of SM. Awareness of the clinical manifestations of vivax malaria should prompt early detection. Subsequent treatment and monitoring of complications can be life-saving.

Until recently, vivax malaria has received less attention than falciparum malaria and was deemed neglected. There has been a surge in studies that documented the contribution of Plasmodium vivax to severe malaria in some endemic countries such as Thailand, Brazil, Indonesia, Papua New Guinea and India. We aimed to synthesize the evidence on severe malaria in P. vivax infection compared with that in P. falciparum infection. We searched relevant studies in electronic databases. The combined results of the eight relatively high quality studies showed a comparable incidence between vivax malaria and falciparum malaria in infants, under 5 year age group, the 5–15 year age group and adults. The combined results of the six relatively high quality studies revealed a comparable incidence of severe anaemia between P. vivax infection and P. falciparum mono-infection in both the infants and the 5–15 year age group. Considering that severe malaria and deaths attributable to P. vivax is not a rare event, raised clinical awareness of the manifestations of vivax malaria in patients of any age should prompt early detection of malaria. It is likely that early detection, appropriate treatment commenced in a timely manner and close monitoring of any complications could be life-saving and contribute to the attainment of the global vision of no malaria deaths.

Accuracy of initial clinical diagnosis of acute bacterial meningitis in children from a malaria-endemic area of Papua New Guinea

BACKGROUND

The diagnosis of acute bacterial meningitis (ABM) is challenging in resource-limited settings where cerebral malaria and viral encephalitis are also common.

METHODS

To assess the accuracy of an initial clinical diagnosis of ABM in a malaria-endemic area of Papua New Guinea (PNG), a retrospective chart review of hospitalized children aged 2 months to 10 years was conducted.

RESULTS

Of the 481 eligible children, 240 had an initial clinical diagnosis of ABM that was confirmed independently by trained research staff under standardized conditions, with laboratory support in only 84 (17.5%; 84/481). When compared with the final laboratory-confirmed diagnosis, an initial diagnosis of ABM had a sensitivity, specificity, positive predictive value and negative predictive value of 76% (95% CI 66-85%), 56% (95% CI 51-61%), 27% (95% CI 21-33) and 92% (95% CI 87-95%), respectively. There was discordance between initial and final diagnosis of ABM in 196 children; 176 initially considered to have ABM had an alternative diagnosis, while 20 without an initial diagnosis of ABM were confirmed to have ABM.

CONCLUSION

These data show that initial misdiagnosis of ABM is common in a malaria-endemic area of PNG. A diagnostic algorithm using standardized assessment for meningeal irritation, coma and malaria parasitological testing needs further evaluation in this setting.

Immunobiology of Plasmodium in liver and brain

Malaria remains one of the most serious health problems globally, but our understanding of the biology of the parasite and the pathogenesis of severe disease is still limited. Multiple cellular effector mechanisms that mediate parasite elimination from the liver have been described, but how effector cells use classical granule-mediated cytotoxicity to attack infected hepatocytes and how cytokines and chemokines spread via the unique fluid pathways of the liver to reach the parasites over considerable distances remains unknown. Similarly, a wealth of information on cerebral malaria (CM), one of the most severe manifestations of the disease, was gained from post-mortem analyses of human brain and murine disease models, but the cellular processes that ultimately cause disease are not fully understood. Here, we discuss how imaging of the local dynamics of parasite infection and host response as well as consideration of anatomical and physiological features of liver and brain can provide a better understanding of the initial asymptomatic hepatic phase of the infection and the cascade of events leading to CM. Given the increasing drug resistance of both parasite and vector and the unavailability of a protective vaccine, the urgency to reduce the tremendous morbidity and mortality associated with severe malaria is obvious.

Severe morbidity and mortality risk from malaria in the United States, 1985-2011

BACKGROUND

Recent reports of Plasmodium vivax associated with severe syndromes and mortality from malaria endemic areas questions the "benign" course of non-falciparum malarias.

METHODS

We retrospectively analyzed data from patients reported to the US Centers for Disease Control and Prevention with a diagnosis of malaria parasite single-species infection between 1985 and 2011. Patients classified as having severe illness were further classified according to outcome (survival versus death) and clinical syndrome.

RESULTS

Among all cases, .9% of Plasmodium falciparum cases resulted in death and 9.3% were classified as severe, whereas .09% of P. vivax cases resulted in death and 1.3% were classified as severe. The odds ratios for severe illness among 15 272 diagnoses of P. falciparum relative to patients diagnosed with P. vivax (n = 12 152), Plasmodium malariae (n = 1254), or Plasmodium ovale (n = 903) was 7.5, 5.7, and 5.0, respectively (P < .0001 for all); in contrast, the corresponding odds ratios for death among those severely ill was 1.6, 1.1, and .8 (P > .1 for all), respectively. Compared with P. vivax (n = 163), the odds of P. falciparum cases classified as severely ill (n = 1416) were 1.9 (P = .0006), .5 (P = .001), and 1.3 times (P = .1) as likely to present as cerebral, acute respiratory distress, and renal syndromes, respectively.

CONCLUSIONS

Although less common, patients presenting with non-falciparum even in the United States can develop severe illness, and severe illness in patients having malaria of any species threatens life.

Malaria

Although global morbidity and mortality have decreased substantially, malaria, a parasite infection of red blood cells, still kills roughly 2000 people per day, most of whom are children in Africa. Two factors largely account for these decreases; increased deployment of insecticide-treated bednets and increased availability of highly effective artemisinin combination treatments. In large trials, parenteral artesunate (an artemisinin derivative) reduced severe malaria mortality by 22·5% in Africa and 34·7% in Asia compared with quinine, whereas adjunctive interventions have been uniformly unsuccessful. Rapid tests have been an important addition to microscopy for malaria diagnosis. Chemopreventive strategies have been increasingly deployed in Africa, notably intermittent sulfadoxine-pyrimethamine treatment in pregnancy, and monthly amodiaquine-sulfadoxine-pyrimethamine during the rainy season months in children aged between 3 months and 5 years across the sub-Sahel. Enthusiasm for malaria elimination has resurfaced. This ambitious but laudable goal faces many challenges, including the worldwide economic downturn, difficulties in elimination of vivax malaria, development of pyrethroid resistance in some anopheline mosquitoes, and the emergence of artemisinin resistance in Plasmodium falciparum in southeast Asia. We review the epidemiology, clinical features, pathology, prevention, and treatment of malaria.

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.

γδ T cells and CD14+ monocytes are predominant cellular sources of cytokines and chemokines associated with severe malaria

BACKGROUND

Severe malaria (SM) is associated with high levels of cytokines such as tumor necrosis factor (TNF), interleukin 1 (IL-1), and interleukin 6 (IL-6). The role of chemokines is less clear, as is their cellular source.

METHODS

In a case-control study of children with SM (n = 200), uncomplicated malaria (UM) (n = 153) and healthy community controls (HC) (n = 162) in Papua, New Guinea, we measured cytokine/chemokine production by peripheral blood mononuclear cells (PBMCs) stimulated with live Plasmodium falciparum parasitized red blood cells (pRBC). Cellular sources were determined. Associations between immunological endpoints and clinical/parasitological variables were tested.

RESULTS

Compared to HC and UM, children with SM produced significantly higher IL-10, IP-10, MIP-1βm and MCP-2. TNF and MIP-1α were significantly higher in the SM compared to the UM group. IL-10, IL-6, MIP-1α, MIP-1β, and MCP-2 were associated with increased odds of SM. SM syndromes were associated with distinct cytokine/chemokine response profiles compared to UM cases. TNF, MIP-1β, and MIP-1α were produced predominantly by monocytes and γδ T cells, and IL-10 by CD4(+) T cells.

CONCLUSIONS

Early/innate PBMC responses to pRBC in vitro are informative as to cytokines/chemokines associated with SM. Predominant cellular sources are monocytes and γδ T cells. Monocyte-derived chemokines support a role for monocyte infiltrates in the etiology of SM.

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.

Clinical spectrum and treatment outcome of severe malaria caused by Plasmodium vivax in 18 children from northern India

OBJECTIVE

The study was intended to document the clinical profile and treatment outcome of severe malaria caused by Plasmodium vivax (P.vivax) in children hospitalized in a tertiary care centre of northern India.

METHODS

This prospective observational study was performed among children admitted with severe malaria at a tertiary care referral hospital of northern India from January 2012 to December 2012. Information was recorded pertaining to clinical symptoms at presentation, examination findings, biochemical and hematological investigation, and treatment outcome. Presence of malarial parasite on thick and thin smears and/or positive parasite lactate dehydrogenase (p-LDH) based rapid malaria antigen test was considered diagnostic of 'malaria'. Based on the etiology, children were categorized into three groups: P.vivax, Plasmodium falciparum (P. falciparum) and mixed infection. Children diagnosed with 'severe malaria' (World Health Organization, 2000), were started on intravenous artesunate followed by artemether-lumefantrine combination.

RESULTS

Thirty-five children with a diagnosis of severe malaria were enrolled [18 (51·4%) P. vivax, nine (25·7%) mixed infection, eight (22·8%) P. falciparum]. Clinical features of severe vivax malaria (n = 18) were abnormal sensorium [9 (50%)], multiple seizures [8 (44·4%)], jaundice [5 (27·8%)], severe anaemia [5 (27·8%)], and shock [3 (16·7%)]. Two children [2/18 (11·1%)] infected with P. vivax had died of cerebral malaria, acute respiratory distress syndrome, shock, and metabolic acidosis. The clinical presentation and outcome of severe vivax malaria was found to be similar to severe malaria caused by P. falciparum and mixed infection, except for higher chances of severe anaemia among the children infected with P. falciparum (P = 0·04).

CONCLUSION

The present study highlights P. vivax as an increasingly recognized causative agent for severe malaria in children from Rohtak, with similar clinical presentation and outcome to that caused by P. falciparum.

Naturally acquired immune responses to P. vivax merozoite surface protein 3α and merozoite surface protein 9 are associated with reduced risk of P. vivax malaria in young Papua New Guinean children

Background

Plasmodium vivax is the most geographically widespread human malaria parasite. Cohort studies in Papua New Guinea have identified a rapid onset of immunity against vivax-malaria in children living in highly endemic areas. Although numerous P. vivax merozoite antigens are targets of naturally acquired antibodies, the role of many of these antibodies in protective immunity is yet unknown.

Methodology/Principal Findings

In a cohort of children aged 1–3 years, antibodies to different regions of Merozoite Surface Protein 3α (PvMSP3α) and Merozoite Surface Protein 9 (PvMSP9) were measured and related to prospective risk of P. vivax malaria during 16 months of active follow-up. Overall, there was a low prevalence of antibodies to PvMSP3α and PvMSP9 proteins (9–65%). Antibodies to the PvMSP3α N-terminal, Block I and Block II regions increased significantly with age while antibodies to the PvMSP3α Block I and PvMSP9 N-terminal regions were positively associated with concurrent P. vivax infection. Independent of exposure (defined as the number of genetically distinct blood-stage infection acquired over time (_molFOB)) and age, antibodies specific to both PvMSP3α Block II (adjusted incidence ratio (aIRR) = 0.59, p = 0.011) and PvMSP9 N-terminus (aIRR = 0.68, p = 0.035) were associated with protection against clinical P. vivax malaria. This protection was most pronounced against high-density infections. For PvMSP3α Block II, the effect was stronger with higher levels of antibodies.

Conclusions

These results indicate that PvMSP3α Block II and PvMSP9 N-terminus should be further investigated for their potential as P. vivax vaccine antigens. Controlling for _molFOB assures that the observed associations are not confounded by individual differences in exposure.

Plasmodium vivax is the most geographically widespread human malaria parasite. In highly endemic areas such as Papua New Guinea, a very rapid onset of immunity against vivax-malaria is observed. Although it is known that numerous P. vivax merozoite antigens are targets of naturally acquired antibodies, the role of many of these antibodies in protective immunity is yet unknown. In a cohort of 183 children aged 1–3 years, we now show that the presence of antibodies to Merozoite Surface Protein 3α (PvMSP3α) and Merozoite Surface Protein 9 (PvMSP9) are associated with a significant reduction in the burden P. vivax malaria. Antibodies increased with age and in the presence of concurrent P. vivax infections. After adjusting for both age and individual differences in exposure, the strongest reductions in risk were seen in children with antibodies to PvMSP3α Block II (41% reduction, p = 0.001) and PvMSP9 N-terminal region. (32% reduction, p = 0.035). These results indicate that PvMSP3α Block II and PvMSP9 N-terminus should be further investigated for their potential as P. vivax vaccine antigens.

Pharmacokinetic properties of single-dose primaquine in Papua New Guinean children: feasibility of abbreviated high-dose regimens for radical cure of vivax malaria

Since conventional 14-day primaquine (PMQ) radical cure of vivax malaria is associated with poor compliance, and as total dose, not therapy duration, determines efficacy, a preliminary pharmacokinetic study of two doses (0.5 and 1.0 mg/kg of body weight) was conducted in 28 healthy glucose-6-phosphate dehydrogenase-normal Papua New Guinean children, aged 5 to 12 years, to facilitate development of abbreviated high-dose regimens. Dosing was with food and was directly observed, and venous blood samples were drawn during a 168-h postdose period. Detailed safety monitoring was performed for hepatorenal function and hemoglobin and methemoglobin concentrations. Plasma concentrations of PMQ and its metabolite carboxyprimaquine (CPMQ) were determined by liquid chromatography-mass spectrometry and analyzed using population pharmacokinetic methods. The derived models were used in simulations. Both single-dose regimens were well tolerated with no changes in safety parameters. The mean PMQ central volume of distribution and clearance relative to bioavailability (200 liters/70 kg and 24.6 liters/h/70 kg) were within published ranges for adults. The median predicted maximal concentrations (Cmax) for both PMQ and CPMQ after the last dose of a 1.0 mg/kg 7-day PMQ regimen were approximately double those at the end of 14 days of 0.5 mg/kg daily, while a regimen of 1.0 mg/kg twice daily resulted in a 2.38 and 3.33 times higher Cmax for PMQ and CPMQ, respectively. All predicted median Cmax concentrations were within ranges for adult high-dose studies that also showed acceptable safety and tolerability. The present pharmacokinetic data, the first for PMQ in children, show that further studies of abbreviated high-dose regimens are feasible in this age group.

Cellular and humoral immune responses against the Plasmodium vivax MSP-1₁₉ malaria vaccine candidate in individuals living in an endemic area in north-eastern Amazon region of Brazil

BACKGROUND

Plasmodium vivax merozoite surface protein-1 (MSP-1) is an antigen considered to be one of the leading malaria vaccine candidates. PvMSP-1 is highly immunogenic and evidences suggest that it is target for protective immunity against asexual blood stages of malaria parasites. Thus, this study aims to evaluate the acquired cellular and antibody immune responses against PvMSP-1 in individuals naturally exposed to malaria infections in a malaria-endemic area in the north-eastern Amazon region of Brazil.

METHODS

The study was carried out in Paragominas, Pará State, in the Brazilian Amazon. Blood samples were collected from 35 individuals with uncomplicated malaria. Peripheral blood mononuclear cells were isolated and the cellular proliferation and activation was analysed in presence of 19 kDa fragment of MSP-1 (PvMSP-1₁₉) and Plasmodium falciparum PSS1 crude antigen. Antibodies IgE, IgM, IgG and IgG subclass and the levels of TNF, IFN-γ and IL-10 were measured by enzyme-linked immunosorbent assay.

RESULTS

The prevalence of activated CD4+ was greater than CD8+ T cells, in both ex-vivo and in 96 h culture in presence of PvMSP-1₁₉ and PSS1 antigen. A low proliferative response against PvMSP-1₁₉ and PSS1 crude antigen after 96 h culture was observed. High plasmatic levels of IFN-γ and IL-10 as well as lower TNF levels were also detected in malaria patients. However, in the 96 h supernatant culture, the dynamics of cytokine responses differed from those depicted on plasma assays; in presence of PvMSP-1₁₉ stimulus, higher levels of TNF were noted in supernatant 96 h culture of malaria patient's cells while low levels of IFN-γ and IL-10 were verified. High frequency of malaria patients presenting antibodies against PvMSP-1₁₉ was evidenced, regardless class or IgG subclass.PvMSP-119-induced antibodies were predominantly on non-cytophilic subclasses.

CONCLUSIONS

The results presented here shows that PvMSP-1₁₉ was able to induce a high cellular activation, leading to production of TNF and emphasizes the high immunogenicity of PvMSP-1₁₉ in naturally exposed individuals and, therefore, its potential as a malaria vaccine candidate.

Prevalence and implications of cerebrospinal fluid leukocytosis in Papua New Guinean children hospitalized with severe malaria

Cerebrospinal fluid (CSF) leukocytosis in severe malaria was assessed in 87 children in Papua New Guinea participating in a detailed longitudinal observational study who had undergone lumbar puncture for further investigation of altered consciousness and/or convulsions. After rigorous exclusion of non-malarial infection, 16 (20.5%) of 78 children with Plasmodium falciparum monoinfection but 0 of 9 with P. vivax/mixed-species malaria had a detectable CSF leukocytosis, which was unrelated to prior, including complex, seizures. There were eight children with a CSF leukocyte density > 10 cells/μL (9.2% of the total sample), half of whom had cerebral malaria (4 of 22, 18.1%). Cerebrospinal fluid leukocytosis is infrequent in severe pediatric malaria, especially in children with P. vivax infections, and it is generally mild. Its presence in a blood slide-positive child should prompt consideration of alternative diagnoses and empiric antibiotic therapy.