Prevalence and risk factors related to poor outcome of patients with severe Plasmodium vivax infection: a systematic review, meta-analysis, and analysis of case reports

Albumin levels in malaria patients: a systematic review and meta-analysis of their association with disease severity

Albumin, a key protein in human blood plasma, has been linked to various health conditions. However, its association with malaria, particularly in assessing disease severity, remains inadequately understood. This comprehensive systematic review and meta-analysis aimed to elucidate the relationship between albumin levels and malaria severity. A comprehensive literature search was conducted across multiple databases, including Embase, Scopus, PubMed, MEDLINE, Ovid, and Google Scholar, to identify studies examining albumin levels in malaria patients. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed. Data were pooled using a random-effects model, and heterogeneity was assessed using I2 statistics. Subgroup and meta-regression analyses were performed based on publication year, study location, and Plasmodium species. A total of 37 studies were included in this review. The thematic synthesis indicated that albumin levels in malaria patients varied significantly based on geographical location. A meta-analysis of 28 studies found that albumin levels were significantly lower in malaria patients compared with non-malarial controls (P < 0.001, standardized mean differences [SMD] = -2.23, 95% CI - 3.25 to - 1.20, I2: 98%, random effects model, 28 studies). Additionally, subgroup analysis revealed variations in albumin levels based on geographical location and Plasmodium species. Regarding the association with disease severity, thematic synthesis showed that severe malaria cases generally had decreased albumin levels across various regions. However, one Brazilian study reported higher albumin levels in severe cases. A separate meta-analysis of five studies found significantly lower albumin levels in patients experiencing severe malaria relative to those with less severe forms of the disease (P < 0.001, SMD = -0.66, 95% CI - 1.07 to - 0.25), I2: 73%, random effects model, 5 studies). This study underscores the clinical significance of albumin as a potential biomarker for Plasmodium infection and the severity of malaria. The findings suggest that albumin level monitoring could be crucial in managing malaria patients, especially in assessing disease severity and tailoring treatment approaches. Additional studies are required to investigate the underlying mechanisms driving these associations and validate the clinical utility of albumin levels in malaria patient management.

An imported malaria case with repeated episodes of neurological syndromes resulting from different Plasmodium species

BACKGROUND

Imported cerebral malaria (CM) cases in non-endemic areas are often misdiagnosed, which delays treatment. Post-malaria neurological syndrome (PMNS) after recovery from severe malaria can also complicate diagnosis.

CASE

We report an imported malaria case from West Africa with two sequential episodes with neurological syndromes within about a month. The first episode was diagnosed as CM with microscopy-positive Plasmodium falciparum infection. The second episode, occurring a month after the recovery from the first CM episode, was consistent with PMNS, since malaria parasites were not detected by microscopy in peripheral blood smears. However, this diagnosis was complicated by the detection of Plasmodium vivax in peripheral blood by PCR, suggesting a potential cause of the second episode by P. vivax.

CONCLUSION

This study suggests that PMNS often occurs after severe falciparum malaria. Concurrent P. vivax infection with pathogenic biomass being predominantly extravascular further complicates accurate diagnosis.

A Pvs25 mRNA vaccine induces complete and durable transmission-blocking immunity to Plasmodium vivax

Plasmodium vivax (P. vivax) is the major malaria parasite outside of Africa and no vaccine is available against it. A vaccine that interrupts parasite transmission (transmission-blocking vaccine, TBV) is considered highly desirable to reduce the spread of P. vivax and to accelerate its elimination. However, the development of a TBV against this pathogen has been hampered by the inability to culture the parasite as well as the low immunogenicity of the vaccines developed to date. Pvs25 is the most advanced TBV antigen candidate for P. vivax. However, in previous phase I clinical trials, TBV vaccines based on Pvs25 yielded low antibody responses or had unacceptable safety profiles. As the nucleoside-modified mRNA-lipid nanoparticle (mRNA-LNP) vaccine platform proved to be safe and effective in humans, we generated and tested mRNA-LNP vaccines encoding several versions of Pvs25 in mice. We found that in a prime-boost vaccination schedule, all Pvs25 mRNA-LNP vaccines elicited robust antigen-specific antibody responses. Furthermore, when compared with a Pvs25 recombinant protein vaccine formulated with Montanide ISA-51 adjuvant, the full-length Pvs25 mRNA-LNP vaccine induced a stronger and longer-lasting functional immunity. Seven months after the second vaccination, vaccine-induced antibodies retained the ability to fully block P. vivax transmission in direct membrane feeding assays, whereas the blocking activity induced by the protein/ISA-51 vaccine dropped significantly. Taken together, we report on mRNA vaccines targeting P. vivax and demonstrate that Pvs25 mRNA-LNP outperformed an adjuvanted Pvs25 protein vaccine suggesting that it is a promising candidate for further testing in non-human primates.

Trends in clinical features and severity of Plasmodium vivax malaria among children at tertiary care center in North India

BACKGROUND

Malaria is a significant cause of morbidity and mortality in adults and children. Plasmodium falciparum is the primary cause of severe malaria, but recently Plasmodium vivax is also recognized to cause severe malaria-associated morbidity and mortality. The study focuses on determining the mortality related to severity parameters in individuals under 12 years and their critical presentation in P.vivax malaria-infected children.

METHODS

A prospective cross-sectional hospital-based study was conducted at Safdarjung Hospital, New Delhi, and ICMR-NIMR, New Delhi. All clinically suspected cases were admitted for screening. Exclusion criteria (rapid malaria antigen test, microscopy and medication history) were applied to all the admitted patients (n = 221) to obtain P.vivax patients only. Patients aged ≤ 12 years were included in the study. DNA was extracted from dried blood spots and amplified by nested PCR, followed by visualization on gel electrophoresis.

RESULT

A total of 221 clinically suspected cases of malaria were screened for P.vivax. After implementing various exclusion criteria, 45/221 cases were enrolled for the study, among which 44.4% (20/45) of children had the symptoms of severe malaria in terms of cerebral malaria, thrombocytopenia, anemia, pancytopenia, acute respiratory distress syndrome and hemophagocytic lymphohistiocytosis.

CONCLUSION

Plasmodium vivax mono-infection can cause severe manifestation and must be treated as P.falciparum without any delay because it may lead to increased morbidity and mortality. A changing trend in clinical symptoms has shown in P.vivax which was an earlier phenomenon of P.falciparum.

Interleukin-5 levels in relation to malaria severity: a systematic review

BACKGROUND

The role of cytokines such as interleukin-5 (IL-5) in the pathogenesis of malaria remains unclear. This systematic review sought to synthesize variations in IL-5 levels between severe and uncomplicated malaria, as well as between malaria and controls not afflicted with the disease.

METHODS

This systematic review was registered at the International Prospective Register of Systematic Reviews (PROSPERO; CRD42022368773). Searches for studies that reported IL-5 levels in patients with malaria (any severity) and/or uninfected individuals were performed in Web of Science, PubMed, EMBASE, Scopus, CENTRAL, and MEDLINE, between 1st and 10th October, 2022. The risk of bias among all included studies was minimized using the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines for reporting observational studies. The differences in IL-5 levels between malaria and uninfected controls, and between severe and uncomplicated malaria were synthesized by narrative synthesis.

RESULTS

Among 1177 articles identified in the databases, 23 matched the eligibility criteria and were included in this systematic review. Qualitative syntheses showed the heterogeneity of IL-5 levels between different severities of clinical malaria and uninfected controls. The majority of the included studies (12/15 studies, 80%) found no change in IL-5 levels between malaria cases and uninfected controls. Similarly, most studies found no difference in IL-5 levels between severe (regardless of complications) and uncomplicated malaria (4/8 studies, 50%). The qualitative syntheses revealed that most studies found no difference in IL-5 levels between severe and non-severe malaria.

CONCLUSIONS

The comprehensive review suggests that IL-5 levels are unchanged in patients with different levels of clinical severity of malaria and uninfected controls. Given the limited number of published studies on IL-5 levels in malaria, there is a need for additional research to determine the function of this cytokine in the pathogenesis of malaria.

Increased interferon-γ levels and risk of severe malaria: a meta-analysis

Interferon (IFN)-γ contributes to the pathogenesis of severe malaria; however, its mechanism remains unclear. Herein, differences in IFN-γ levels between patients with severe and uncomplicated malaria were evaluated using qualitative and quantitative (meta-analysis) approaches. The systematic review protocol was registered at PROSPERO (ID: CRD42022315213). The searches for relevant studies were performed in five databases, including PubMed, Scopus, Embase, MEDLINE and Web of Science, between 1 January and 10 July 2022. A meta-analysis was conducted to pool the mean difference (MD) of IFN-γ levels between patients with severe malaria and those with uncomplicated malaria using a random-effects model (DerSimonian and Laird method). Overall, qualitative synthesis indicated that most studies (14, 58.3%) reported no statistically significant difference in IFN-γ levels between patients with severe malaria and those with uncomplicated malaria. Meanwhile, remaining studies (9, 37.5%) reported that IFN-γ levels were significantly higher in patients with severe malaria than those in patients with uncomplicated malaria. Only one study (4.17%) reported that IFN-γ levels were significantly lower in patients with severe malaria than those in patients with uncomplicated malaria. The meta-analysis results indicated that patients with severe malaria had higher mean IFN-γ levels than those with uncomplicated malaria (p < 0.001, MD: 13.63 pg/mL, 95% confidence interval: 6.98-20.29 pg/mL, I²: 99.02%, 14 studies/15 study sites, 652 severe cases/1096 uncomplicated cases). In summary, patients with severe malaria exhibited higher IFN-γ levels than those with uncomplicated malaria, although the heterogeneity of the outcomes is yet to be elucidated. To confirm whether alteration in IFN-γ levels of patients with malaria may indicate disease severity and/or poor prognosis, further studies are warranted.

Transforming Growth Factor-β Concerning Malarial Infection and Severity: A Systematic Review and Meta-Analysis

Transforming growth factor-β (TGF-β) is important in the pathophysiology of malaria, but its role in acute and severe malaria is largely unknown. As a result, this study used a meta-analysis approach to investigate the difference in TGF-β levels between several groups of malaria patients and healthy controls. The systematic review protocol was registered at PROSPERO (ID: CRD42022318864). From inception to 7 March 2022, studies that reported TGF-β levels in patients with uncomplicated and healthy controls and patients with severe and uncomplicated malaria were searched in PubMed, Scopus and Embase. The assessment of the quality of the included studies was conducted according to the Strengthening the Reporting of Observational Studies in Epidemiology guidelines. Qualitative and quantitative syntheses were performed to narratively describe and quantitatively pool the mean difference (MD) in TGF-β levels between uncomplicated malaria and healthy controls, and between severe and uncomplicated malaria, using a random-effects model. A total of 1027 relevant articles were identified, and 13 studies were included for syntheses. The meta-analysis results show 233 patients with uncomplicated malaria and 239 healthy controls. Patients with uncomplicated malaria (233 cases) had lower mean TGF-β levels than healthy controls (239 cases; p < 0.01, pooled MD = −14.72 pg/mL, 95% confidence interval (95% CI) = −20.46 to 8.99 pg/mL, I2 = 98.82%, seven studies). The meta-analysis found no difference in mean TGF-β levels between patients with severe malaria (367 cases) and patients with uncomplicated malaria (180 cases; p = 0.11, pooled MD = −6.07 pg/mL, 95% CI = −13.48 to 1.35 pg/mL, I2 = 97.73%, six studies). The meta-analysis demonstrated decreased TGF-β levels in patients with uncomplicated malaria compared to healthy controls. In addition, no difference in TGF-β levels was found between patients with severe and uncomplicated malaria. More research is needed to determine whether TGF-β levels could be a candidate marker for malarial infection or disease severity.

Procalcitonin as a Candidate Biomarker for Malarial Infection and Severe Malaria: A Meta-Analysis

Procalcitonin (PCT), as a marker of malaria severity, remains to be investigated. The present study collated and compared the levels of PCT between patients with severe malaria, uncomplicated malaria, and control participants to assess their role in predicting malaria infection and disease severity. The systematic review was registered at PROSPERO with registration number CRD42021297243. The search for relevant studies that reported PCT in patients with malaria was performed in PubMed, Scopus, and Web of Science. The following meta-analyses were conducted; (1) the pooled mean PCT levels in patients with severe and uncomplicated malaria, and (2) the pooled mean difference in PCT levels between patients with severe and uncomplicated malaria. Fifteen studies were included for qualitative and quantitative syntheses. The meta-analysis results show that the pooled mean PCT levels in patients with uncomplicated malaria were 3.92 ng/mL (95% CI: 2.26-5.58 ng/mL, I²: 96.5, five studies), whereas the pooled mean PCT levels in patients with severe malaria were 14.13 ng/mL (95% CI: 8.75-19.5 ng/mL, I²: 92.6, six studies). The meta-analysis showed that patients with severe malaria had an equal mean of PCT compared to those with uncomplicated malaria when the random-effects model was used (p: 0.055, weighted mean difference: 6.93, 95% CI: -0.16-14.02, I²: 84.6%, four studies). There were probable correlations between the level of parasitemia, immunity level, and possibly bacterial or other parasitic co-infection that could affect the PCT level among different clinical severities of malaria. Therefore, the PCT level alone does not seem to be a suitable biomarker to discriminate the severe/uncomplicated or infected/uninfected cases. Further studies should investigate the increased PCT levels in combination with other markers in association with malaria infection and severity.

Prevalence, anti-malarial chemoprophylaxis and causes of deaths for severe imported malaria: A systematic review and meta-analysis

BACKGROUND

There are limited data regarding prevalence, anti-malarial chemoprophylaxis, and causes of death for severe imported malaria. Thus, we conducted a systematic review and meta-analysis to characterise these variables.

METHODS

We searched studies reporting deaths attributable to severe imported malaria. The following pooled prevalence rates were determined: 1) the pooled prevalence of severe malaria among patients with imported malaria, 2) the pooled prevalence of deaths among patients with severe imported malaria, 3) the pooled prevalence of anti-malarial chemoprophylaxis among patients with severe imported malaria, and 4) the causes of death among patients with severe imported malaria.

RESULTS

The search identified 52 studies that were mainly conducted in Europe (25, 48.1%), North America (16, 30.8%) and Asia (7, 13.5%). The pooled prevalence of severe imported malaria was 12.5% (95% confidence interval [CI] = 10.3%-14.6%, I² = 99.32%, 12393 severe cases/118325 imported cases). The pooled prevalence of deaths attributable to severe imported malaria was 5.1% (95% CI = 4.0%-6.2%, I² = 91.72%, 721 deaths/16310 severe cases). The pooled prevalence of adequate anti-malarial chemoprophylaxis among patients with severe imported malaria was 9.7% (95% CI = 6.5%-13.0%, I² = 89.9%, 203/2049 cases). The most common cause of death was multi-organ failure (12.3%).

CONCLUSION

The results highlighted the need for education and preventative measures for travellers, immigrants, or workers who plan to visit malaria-endemic areas to minimize the risk of severe disease or death.

Prevalence and Characteristics of Malaria and Influenza Co-Infection in Febrile Patients: A Systematic Review and Meta-Analysis

Malaria and influenza are co-endemic in several geographical areas, and differentiation of their clinical features is difficult. The present study aimed to qualitatively and quantitatively analyze the prevalence and characteristics of malaria and influenza co-infection in febrile patients. The systematic review was registered at PROSPERO (CRD42021264525). Relevant literature that reported malaria and influenza co-infection in febrile patients were searched in PubMed, Web of Science, and Scopus from 20 June to 27 June 2021 and the risk of bias for each study was assessed. Quantitative analysis included pooled prevalence, and the odds of malaria and influenza virus co-infection among febrile patients were estimated using a random-effects model. Subgroup analyses were performed to summarize the effect estimate for each group. Funnel plot, Egger’s test, and contour-enhanced funnel plot were used to demonstrate any publication bias among outcomes of included studies. Among 4253 studies retrieved, 10 studies that enrolled 22,066 febrile patients with 650 co-infected patients were included for qualitative and quantitative syntheses. The pooled prevalence of malaria and influenza virus co-infection among febrile patients was 31.0% in Nigeria, 1.0% in Tanzania, 1.0% in Uganda, 1.0% in Malawi, 1.0% in Ghana, 0% in Cambodia, 7.0% in the Central African Republic, and 7.0% in Kenya. Meta-analysis also showed co-infection occurrence by chance (p = 0.097, odds ratio 0.54, 95% CI 0.26–1.12, I² 94.9%). The prevalence of malaria and influenza virus co-infection among febrile patients was heterogeneous by country, characteristics of febrile participants, and diagnostic tests for influenza virus. Further studies should investigate severe clinical manifestations or differentiate clinical outcomes between mono-infected or co-infected individuals, whether the co-infection leads to severe disease outcome.

Diagnosis, Treatment, and Prevention of Malaria in the US: A Review

IMPORTANCE

Malaria is caused by protozoa parasites of the genus Plasmodium and is diagnosed in approximately 2000 people in the US each year who have returned from visiting regions with endemic malaria. The mortality rate from malaria is approximately 0.3% in the US and 0.26% worldwide.

OBSERVATIONS

In the US, most malaria is diagnosed in people who traveled to an endemic region. More than 80% of people diagnosed with malaria in the US acquired the infection in Africa. Of the approximately 2000 people diagnosed with malaria in the US in 2017, an estimated 82.4% were adults and about 78.6% were Black or African American. Among US residents diagnosed with malaria, 71.7% had not taken malaria chemoprophylaxis during travel. In 2017 in the US, P falciparum was the species diagnosed in approximately 79% of patients, whereas P vivax was diagnosed in an estimated 11.2% of patients. In 2017 in the US, severe malaria, defined as vital organ involvement including shock, pulmonary edema, significant bleeding, seizures, impaired consciousness, and laboratory abnormalities such as kidney impairment, acidosis, anemia, or high parasitemia, occurred in approximately 14% of patients, and an estimated 0.3% of those receiving a diagnosis of malaria in the US died. P falciparum has developed resistance to chloroquine in most regions of the world, including Africa. First-line therapy for P falciparum malaria in the US is combination therapy that includes artemisinin. If P falciparum was acquired in a known chloroquine-sensitive region such as Haiti, chloroquine remains an alternative option. When artemisinin-based combination therapies are not available, atovaquone-proguanil or quinine plus clindamycin is used for chloroquine-resistant malaria. P vivax, P ovale, P malariae, and P knowlesi are typically chloroquine sensitive, and treatment with either artemisinin-based combination therapy or chloroquine for regions with chloroquine-susceptible infections for uncomplicated malaria is recommended. For severe malaria, intravenous artesunate is first-line therapy. Treatment of mild malaria due to a chloroquine-resistant parasite consists of a combination therapy that includes artemisinin or chloroquine for chloroquine-sensitive malaria. P vivax and P ovale require additional therapy with an 8-aminoquinoline to eradicate the liver stage. Several options exist for chemoprophylaxis and selection should be based on patient characteristics and preferences.

CONCLUSIONS AND RELEVANCE

Approximately 2000 cases of malaria are diagnosed each year in the US, most commonly in travelers returning from visiting endemic areas. Prevention and treatment of malaria depend on the species and the drug sensitivity of parasites from the region of acquisition. Intravenous artesunate is first-line therapy for severe malaria.

Low Interleukin-12 Levels concerning Severe Malaria: A Systematic Review and Meta-Analysis

Although many studies have investigated the role of interleukin (IL)-12 cytokine in the pathogenesis of severe malaria, these studies were based on a limited number of participants, possibly affecting their outcomes. We analyzed the difference in IL-12 levels between patients with severe and uncomplicated malaria through a meta-analysis. A systematic review was conducted following the Cochrane Handbook for Systematic Reviews of Interventions and was reported according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses statement. Systematic literature searches were performed between 20 February and 2 March, 2022 in PubMed, Scopus, and Embase to identify studies reporting IL-12 levels in patients with severe and uncomplicated malaria. The quality of included studies was determined using the Strengthening the Reporting of Observational Studies in Epidemiology guidelines. The pooled mean difference (MD) in IL-12 between patients with severe and uncomplicated malaria was estimated using the DerSimonian-Laird method for the random-effects model. Altogether, 1885 potentially relevant articles were identified, and 10 studies enrolling 654 patients with severe malaria and 626 patients with uncomplicated malaria were included in the meta-analysis. Patients with severe malaria had lower mean IL-12 levels than those with uncomplicated malaria (p = 0.01, MD: -33.62, 95% confidence interval [CI]: -58.79 to -8.45, I2: 99.29%, 10 studies). In conclusion, decreased IL-12 levels might significantly contribute to the development of severe malaria. As most published literature demonstrated the role of IL-12 in animal models, human studies are required to understand the mechanisms involved in low IL-12 levels in patients with severe malaria.

Impact of Plasmodium vivax malaria on executive and cognitive functions in elderlies in the Brazilian Amazon

The exact path leading to cognitive impairment that goes beyond malaria is unclear, but it appears to be the result of interactive factors. Time of exposure to disease and recurrences are potentially major determinant variables. Cognitive impairment is described mainly in children, rarely in adults. The disease in high endemic areas usually does not affect elderlies, because of acquired immunity over time. However, this population is relatively more frequently sick in lower endemic areas, such as in the Amazon. This study assessed the effect of Plasmodium vivax malaria on the executive and cognitive functions of elderlies, in the Brazilian Amazon. A cohort study was conducted to evaluate executive and cognitive functions one week (T0), two months (T2) and eight months (T8) after the malaria episode. Mini-Mental State Examination (MMSE), Beck Depression Inventory II (BDI-II), Clock Drawing Test (CDT), Wechsler adult intelligence scale (WAIS-III), and Wisconsin Card Sorting Test (WCST) were used to assess executive and cognitive functions. One hundred-forty elderlies were enrolled (70 with P. vivax malaria and 70 without malaria). P. vivax malaria was associated with impairment of the executive and cognitive functions in elderlies for up to 8 months after acute P. vivax malaria. Prior history of malaria, recurrences and higher parasitemia were independently associated with various surrogates of executive and cognitive impairment. With the increase in life expectancy, elderlies living in malaria endemic areas will deserve more attention from health authorities, to guarantee improvement of their quality of life in the tropics.

Prevalence of Malaria and Associated Risk Factors among the Community of Mizan-Aman Town and Its Catchment Area in Southwest Ethiopia

Background

Ethiopia is a Sub-Saharan African country with a high annual malaria case count, owing to the majority of the country's geography favoring vector rearing. As part of the country's prevention-based health policy, substantial efforts have been made to control and prevent malaria transmission. The objective of this study was to determine the prevalence of malaria and the associated factors in the community of Mizan-Aman and its catchment.

Materials and Methods

From September to October 2021, a community-based cross-sectional survey was undertaken among the communities of Mizan-Aman town and its catchment area in Southwest Ethiopia. A pretested structured questionnaire was used to collect sociodemographic data, as well as a capillary blood sample from each study participant. Epi-data manager (v4.0.2.101) was used to enter the data and analyzed by SPSS version 25.0. A statistical significance was set at a P value of <0.05.

Result

The study comprised a total of 412 people, of which 87 (21.1%) tested positive for malaria parasites, with a greater prevalence reported among those aged 25 to 34 years (5.8%). Individuals who lived near stagnant water were more likely to become infected with the malaria parasite (AOR = 8.996, 95% CI: 5.087-15.908) compared to those who lived further away, in warm climates, and those who did not use insecticide-treated bed nets were more susceptible to malaria parasite infection (AOR = 4.647, 95% CI: 1.257-17.184) compared to those who did use ITN and With (AOR = 0.466, 95% CI: 0.218-0.996 and AOR = 0.352, 95% CI: 0.206-0.604); participants with a history of antimalarial medication appear to have a protective function against malaria infection, respectively.

Conclusion

The overall malaria prevalence in this study was 87 (21.1%), demonstrating that malaria remains a significant concern to the populations in the study area, with Plasmodium falciparum accounting for the vast majority of cases.

Prevalence and risk of Plasmodium vivax infection among Duffy-negative individuals: a systematic review and meta-analysis

A better understanding of the occurrence and risk of Plasmodium vivax infection among Duffy-negative individuals is required to guide further research on these infections across Africa. To address this, we used a meta-analysis approach to investigate the prevalence of P. vivax infection among Duffy-negative individuals and assessed the risk of infection in these individuals when compared with Duffy-positive individuals. This study was registered with The International Prospective Register of Systematic Reviews website (ID: CRD42021240202) and followed Preferred Reporting Items for Systematic review and Meta-Analyses guidelines. Literature searches were conducted using medical subject headings to retrieve relevant studies in Medline, Web of Science, and Scopus, from February 22, 2021 to January 31, 2022. Selected studies were methodologically evaluated using the Joanna Briggs Institute (JBI) Critical Appraisal Tools to assess the quality of cross-sectional, case-control, and cohort studies. The pooled prevalence of P. vivax infection among Duffy-negative individuals and the odds ratio (OR) of infection among these individuals when compared with Duffy-positive individuals was estimated using a random-effects model. Results from individual studies were represented in forest plots. Heterogeneity among studies was assessed using Cochrane Q and I2 statistics. We also performed subgroup analysis of patient demographics and other relevant variables. Publication bias among studies was assessed using funnel plot asymmetry and the Egger's test. Of 1593 retrieved articles, 27 met eligibility criteria and were included for analysis. Of these, 24 (88.9%) reported P. vivax infection among Duffy-negative individuals in Africa, including Cameroon, Ethiopia, Sudan, Botswana, Nigeria, Madagascar, Angola, Benin, Kenya, Mali, Mauritania, Democratic Republic of the Congo, and Senegal; while three reported occurrences in South America (Brazil) and Asia (Iran). Among studies, 11 reported that all P. vivax infection cases occurred in Duffy-negative individuals (100%). Also, a meta-analysis on 14 studies showed that the pooled prevalence of P. vivax infection among Duffy-negative individuals was 25% (95% confidence interval (CI) - 3%-53%, I2 = 99.96%). A meta-analysis of 11 studies demonstrated a decreased odds of P. vivax infection among Duffy-negative individuals (p = 0.009, pooled OR 0.46, 95% CI 0.26-0.82, I2 = 80.8%). We confirmed that P. vivax infected Duffy-negative individuals over a wide prevalence range from 0 to 100% depending on geographical area. Future investigations on P. vivax infection in these individuals must determine if Duffy-negativity remains a protective factor for P. vivax infection.

Prevalence of Signs of Severity Identified in the Thai Population with Malaria: A Systematic Review and Meta-Analysis

Understanding the prevalence of signs of severity identified in the Thai population with malaria could aid clinical management and disease control efforts, decrease mortality, and promote malaria elimination in Thailand. This systematic review aimed to collate the evidence regarding signs of severity identified in the Thai population with malaria. MEDLINE, Web of Science, and Scopus were searched for potentially relevant studies. The quality of the included studies was assessed using the Joanna Briggs Institute critical appraisal tools. The pooled prevalence of signs of severity among patients with severe malaria and the pooled proportion of each sign of severity among all signs of severity were estimated using random-effects models. Heterogeneity among included studies was assessed using Cochran’s Q test. A subgroup analysis was performed to evaluate whether differences in pooled estimates between different study sites. Publication bias was assessed by visualizing funnel plot asymmetry and using Egger’s test. Among 741 studies identified by literature searching, 12 studies of a total of 2900 patients with severe malaria, in 7 Thai hospitals, met the eligibility criteria. Results of meta-analyses showed that the signs of the severity of malaria with the highest prevalence in Thailand were jaundice (54%), hyperparasitemia (47%), impaired consciousness/coma (21%), acidosis (18%), renal impairment (13%), shock (10%), convulsions (9%), severe anemia (8%), pulmonary edema/acute respiratory distress syndrome (ARDS) (8%), hypoglycemia (4%), and bleeding/disseminated intravascular coagulation (DIC) (2%). The signs of the severity of malaria that made up the highest proportion of all signs of severity identified in the Thai population with malaria were hyperparasitemia (33%), jaundice (33%), impaired consciousness/coma (12%), acidosis (9%), renal impairment (7%), severe anemia (6%), convulsions (5%), shock (5%), pulmonary edema/ARDS (3%), bleeding/DIC (1%), and hypoglycemia (1%). The present study revealed the prevalence of signs of severity identified in the Thai population with malaria. Jaundice, hyperparasitemia, and impaired consciousness/coma were the most common signs of severity identified. These results may inform the management of patients with severe malaria and promote malaria-elimination efforts in Thailand.

Prevalence and outcomes of malaria as co-infection among patients with human African trypanosomiasis: a systematic review and meta-analysis

Human African trypanosomiasis (HAT) is endemic in Africa; hence, the possibility of co-infection with malaria among patients with HAT exists. The present study investigated co-infection with malaria among patients with HAT to provide current evidence and characteristics to support further studies. Potentially relevant studies that reported Plasmodium spp. infection in patients with HAT was searched in PubMed, Web of Science, and Scopus. The risk of bias among the included studies was assessed using the checklist for analytical cross-sectional studies developed by the Joanna Briggs Institute. The pooled prevalence of Plasmodium spp. infection in patients with HAT was quantitatively synthesized using a random-effects model. Subgroup analyses of study sites and stages of HAT were performed to identify heterogeneity regarding prevalence among the included studies. The heterogeneity of the outcome among the included studies was assessed using Cochran’s Q and I² statistics for consistency. Publication bias was assessed if the number of included studies was 10 or more. For qualitative synthesis, a narrative synthesis of the impact of Plasmodium spp. infection on the clinical and outcome characteristics of HAT was performed when the included studies provided qualitative data. Among 327 studies identified from three databases, nine studies were included in the systematic review and meta-analysis. The prevalence of Plasmodium spp. co-infection (692 cases) among patients with HAT (1523 cases) was 50% (95% confidence interval [CI] = 28–72%, I² = 98.1%, seven studies). Subgroup analysis by type of HAT (gambiense or rhodesiense HAT) revealed that among patients with gambiense HAT, the pooled prevalence of Plasmodium spp. infection was 46% (95% CI = 14–78%, I² = 96.62%, four studies), whereas that among patients with rhodesiense HAT was 44% (95% CI = 40–49%, I² = 98.3%, three studies). Qualitative syntheses demonstrated that Plasmodium spp. infection in individuals with HAT might influence the risk of encephalopathy syndrome, drug toxicity, and significantly longer corrected QT time. Moreover, longer hospital stays and higher treatment costs were recorded among co-infected individuals. Because of the high prevalence of malaria among patients with HAT, some patients were positive for malaria parasites despite being asymptomatic. Therefore, it is suggested to test every patient with HAT for malaria before HAT treatment. If malaria is present, then antimalarial treatment is recommended before HAT treatment. Antimalarial treatment in patients with HAT might decrease the probability of poor clinical outcomes and case fatality in HAT.

Plasmodium vivax transmission-blocking vaccines: Progress, challenges and innovation

Existing control measures have significantly reduced malaria morbidity and mortality in the last two decades, although these reductions are now stalling. Significant efforts have been undertaken to develop malaria vaccines. Recently, extensive progress in malaria vaccine development has been made for Plasmodium falciparum. To date, only the RTS,S/AS01 vaccine has been tested in Phase 3 clinical trials and is now under implementation, despite modest efficacy. Therefore, the development of a malaria transmission-blocking vaccine (TBV) will be essential for malaria elimination. Only a limited number of TBVs have reached pre-clinical or clinical development with several major challenges impeding their development, including low immunogenicity in humans. TBV development efforts against P. vivax, the second major cause of malaria morbidity, lag far behind those for P. falciparum. In this review we summarize the latest progress, challenges and innovations in P. vivax TBV research and discuss how to accelerate its development.

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.

Alteration of Blood Lactate Levels in Severe Falciparum Malaria: A Systematic Review and Meta-Analysis

Simple Summary

Alteration of blood lactate levels in patients with severe falciparum malaria is well recognized. However, data on blood lactate in literatures were based on a limited number of participants. The present systematic review aimed to collate the blood lactate levels recorded in the literature and used a metaanalysis approach to pool the evidence in a larger sample size than that used in the individual studies to determine the trend. Results from this study will provide the pooled evidence of blood lactate levels in patients with severe malaria for further studies that identifying patients with a high risk of developing severe malaria or death.

Abstract

Metabolic acidosis in severe malaria usually occurs in the form of lactic acidosis. The present study aimed to collate articles from the literature that have reported blood lactate levels in patients with severe malaria and tested the hypothesis that blood lactate levels are elevated in patients with malaria compared to those with uncomplicated malaria. Moreover, the difference in lactate levels between patients who died and those who survived was estimated using a meta-analytic approach. Potentially relevant studies were searched for in PubMed, Web of Science, and Scopus. The quality of the included studies was assessed using the Jadad scale and strengthening the reporting of observational studies in epidemiology (STROBE). The pooled mean blood lactate in patients with severe malaria, the pooled weighted mean difference (WMD) of blood lactate between patients with severe malaria and those with uncomplicated malaria, and the pooled WMD and 95% CI of blood lactate between patients who died from and those who survived severe malaria were estimated using the random-effects model. Heterogeneity among the outcomes of the included studies was assessed using Cochran’s Q and I² statistics. A meta-regression analysis was performed to identify the source(s) of heterogeneity of outcomes among the included studies. A subgroup analysis was further performed to separately analyze the outcomes stratified by the probable source(s) of heterogeneity. Publication bias was assessed by the visual inspection of the funnel plot asymmetry. Of 793 studies retrieved from the searches, 30 studies were included in qualitative and quantitative syntheses. The pooled mean lactate in patients with severe malaria was 5.04 mM (95% CI: 4.44–5.64; I²: 99.9%; n = 30,202 cases from 30 studies). The mean lactate in patients with severe malaria (1568 cases) was higher than in those with uncomplicated malaria (1693 cases) (p = 0.003; MD: 2.46; 95% CI: 0.85–4.07; I²: 100%; nine studies). The mean lactate in patients with severe malaria who died (272 cases) was higher than in those with severe malaria who survived (1370 cases) (p < 0.001; MD: 2.74; 95% CI: 1.74–3.75; I²: 95.8%; six studies). In conclusion, the present study showed a high mean difference in blood lactate level between patients with severe malaria and patients with uncomplicated malaria. In addition, there was a high mean difference in blood lactate level between patients with severe malaria who died compared to those with severe malaria who survived. Further studies are needed to investigate the prognostic value of blood lactate levels to identify patients who are at high risk of developing severe malaria or dying.

Prevalence and characteristics of malaria among COVID-19 individuals: A systematic review, meta-analysis, and analysis of case reports

BACKGROUND

The world population is currently at a very high risk of Coronavirus disease-2019 (COVID-19), caused by the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2). People who live in malaria-endemic areas and get infected by SARS-CoV-2 may be at increased risk of severe COVID-19 or unfavorable disease outcomes if they ignore their malaria status. Therefore, the present study aimed to synthesize, qualitatively and quantitatively, information on the prevalence and characteristics of malaria infection among COVID-19-infected individuals. The findings will help us better understand this particular comorbidity during the COVID-19 pandemic.

METHODS

The systematic review protocol was registered at the International Prospective Register of Systematic Reviews (PROSPERO) with the identification number: CRD42021247521. We searched for studies reporting on the coinfection of COVID-19 and malaria in PubMed, Web of Science, and Scopus from inception to March 27, 2021 using Medical Subject Headings (MeSH) terms. The study's methodological quality in the search output was assessed using the Joanna Briggs Institute (JBI) Critical Appraisal Tools for cross-sectional study. The pooled prevalence of Plasmodium spp. infection among patients infected with COVID-19 was estimated using the random effect model and then graphically presented as forest plots. The heterogeneity among the included studies was assessed using Cochrane Q and I2 statistics. The characteristics of patients co-infected with COVID-19 and malaria were derived from case reports and series and were formally analyzed using simple statistics.

RESULTS

Twelve of 1,207 studies reporting the coinfection of COVID-19 and malaria were selected for further analysis. Results of quantitative synthesis show that the pooled prevalence of Plasmodium spp. infection (364 cases) among COVID-19 individuals (1,126 cases) is 11%, with a high degree of heterogeneity (95% CI: 4%-18%, I2: 97.07%, 5 studies). Most of the coinfections were reported in Nigeria (336 cases), India (27 cases), and the Democratic Republic of Congo (1 case). Results of qualitative synthesis indicate that patients with coinfection are typically symptomatic at presentation with mild or moderate parasitemia. An analysis of case reports and series indicates that co-infected individuals often display thrombocytopenia, lymphopenia, and elevated bilirubin levels. Among four patients (30%) who required treatment with intravenous artesunate, one experienced worsened clinical status after administering the drug. One serious outcome of coinfection involved a pregnant woman who experienced fetal abortion due to the initial misdiagnosis of malaria.

CONCLUSIONS

All individuals in malaria-endemic regions who are febrile or display symptoms of COVID-19 should be evaluated for malaria to avoid serious complications. Further prospective studies are required to investigate the burden and outcomes of COVID-19 in malaria-endemic regions. Prompt management is required to prevent serious outcomes in individuals co-infected with COVID-19 and malaria.

A meta-analysis on the prevalence and characteristics of severe malaria in patients with Plasmodium spp. and HIV co-infection

Co-infection with malaria and human immunodeficiency virus (HIV) increases the severity and mortality rates of both diseases. A better understanding of the effects of co-infections could help in the diagnosis, prompt treatment, prevention, and control of malarial parasites among HIV-infected patients. In this systematic review and meta-analysis, we estimated the prevalence and characteristics of severe malaria (SM) caused by co-infection with HIV. We included relevant studies that were conducted between the years 1991 and 2018 and reporting on SM. We pooled the prevalence of SM in patients with co-infection, pooled odds ratios of SM in patients with co-infection and Plasmodium mono-infection, and differences in laboratory parameters such as parasite density and leucocyte counts, between co-infected and Plasmodium mono-infected patients. The meta-analysis included 29 studies (1126 SM cases). The pooled prevalence of SM in co-infected patients using the data of 23 studies (SM = 795 cases, all co-infection cases = 2534 cases) was 43.0% (95% confidence interval [CI] 31.0–56.0%; I², 98.0%). Overall, the odds of SM from 18 studies were pooled. The odds of SM were significantly higher in co-infected patients than in Plasmodium mono-infected patients (OR 2.41; 95% CI 1.43–4.08; I² = 85%; P = 0.001) and also significantly higher in children (OR 9.69; 95% CI 5.14–18.3; I², 0%; P < 0.0001; two studies) than in adults (OR 2.68; 95% CI 1.52–4.73; I², 79.0%; P = 0.0007; 12 studies). Co-infected patients with SM had a higher parasite density than those with Plasmodium mono-infection when the data of seven studies were analysed (SMD, 1.25; 95% CI 0.14–2.36; I², 98.0%; P = 0.03) and higher leukocyte counts when the data of four studies were analysed (MD, 1570 cells/µL; 95% CI 850–2300 cells/µL; I², 21.0%; P < 0.0001). Thus, the prevalence of SM among patients co-infected with Plasmodium spp. and HIV is high. Because co-infections could lead to SM, patients with Plasmodium spp. and HIV co-infection should be identified and treated to reduce the prevalence of SM and the number of deaths.

Blood Lead Levels and Subsequence Risk of Malaria in the African Population: A Systematic Review and Meta-Analysis

Previous epidemiological studies showed that blood lead level (BLL) was associated with malaria infection and severity. Therefore, the present study aimed to qualitatively and quantitatively synthesize the evidence on the association between BLL and risk of malaria infection and severity using the systematic review and meta-analysis approach. Potentially relevant studies were identified from three databases using a combination of search terms. The quality of the included studies was assessed using the checklist for the cross-sectional studies developed by the Joanna Briggs Institute. The qualitative synthesis of the risk or odds of malaria infection in patients with BLL was performed as the outcome of each included study could not be pooled. The pooled mean BLL and prevalence of malaria infection of the included studies was estimated using a random-effect model. The heterogeneity of the outcomes among the included studies was assessed using the Cochran Q test and I² statistics. The subgroup analysis of the study sites and participants was performed to explore the source(s) of heterogeneity of the outcomes. Publication bias was assessed in the case of more than 10 studies used for pooling of the same outcome. Among 114 potentially relevant studies identified from the databases, 6 eligible studies were included for qualitative and quantitative syntheses. The results showed that the pooled mean BLLs were 7.33 μg/dL in children (95% confidence interval (95%CI), 4.08–10.58; I², 98.2%), 7.94 μg/dL in children with BLL > 45 mg/dL before chelation (95%CI, 7.87–8.01), 7.41 μg/dL in infants (95%CI, 7.34–7.48 μg/dL), 9.20 μg/dL in children with malaria (95%CI, 9.16–9.24 μg/ dL), and 36.37 μg/dL in pregnant women (95%CI, 34.43–38.31 μg/dL). The prevalence rates of malaria among participants (2381 participants, 803 malaria-positive patients) were 53% in children (95%CI, 50–57%; I², 99.8%), 24% in children with BLL > 45 mg/dL before chelation (95%CI, 21–27%), 12% in infants (95%CI, 8–18%), and 21% in pregnant women (95%CI, 18–26%). The subgroup analysis of countries demonstrated that the prevalence rates of malaria among participants was 17% in Benin (95%CI, 13–21%; I², 98.8%) and 36% in Nigeria (95%CI, 10–63%; I², 99.4%). BLL associated with decreased risk of malaria was demonstrated by two studies conducted in Benin and Nigeria, while BLL associated with increased risk of malaria was demonstrated by a study conducted in Nigeria. BLL was associated with the risk of severe malaria, involving severe neurological features and severe anemia. In conclusion, the present systematic review and meta-analysis determined the current status of the studies on BLL and risk of malaria in African countries. Further studies are needed to investigate the impact of BLL on patients with malaria to help the clinician determine the risk of severity, such as the development of neurological features or severe anemia, among patients exposed to lead.

Prevalence of Malaria and Leptospirosis Co-Infection among Febrile Patients: A Systematic Review and Meta-Analysis

Malaria and leptospirosis are important cosmopolitan infections that have emerged with overlapping geographic distribution, especially in tropical and subtropical regions. Therefore, co-infection with malaria and leptospirosis may occur in overlapping areas. The present study aimed to quantify the prevalence of malaria and leptospirosis co-infection among febrile patients. The association between malaria and leptospirosis infections was also investigated. Relevant studies that had reported malaria and leptospirosis co-infection were identified from PubMed, Scopus, and Web of Science. The risk of bias of the studies was assessed using the Joanna Briggs Institute (JBI) Critical Appraisal Tool. The pooled prevalence of malaria and leptospirosis co-infections among febrile patients and the pooled prevalence of leptospirosis infection among malaria patients were estimated using random effect models. The association between malaria and leptospirosis infection among febrile patients was estimated using random effect models. The outcomes of each study were shown in a forest plot in point estimate and 95% confidence interval (CI). Heterogeneity among the included studies was assessed using Cochran’s Q and quantified using I-squared statistics. For leptospirosis, subgroup analyses of countries, diagnostic tests, and participants’ age groups were performed to specify prevalence in each subgroup. Publication bias was assessed by funnel-plot visualization. Of the 2370 articles identified from the databases, 15 studies met the eligibility criteria and were included for qualitative and quantitative syntheses. Most of the included studies were conducted in India (5/15, 33.3%), Thailand (3/15, 20%), and Cambodia (2/15, 13.3%). Most of the enrolled cases were febrile patients (5838 cases) and malaria-positive patients (421 cases). The meta-analysis showed that the pooled prevalence of malaria and leptospirosis co-infection (86 cases) among febrile patients was 1% (95% CI: 1–2%, I²: 83.3%), while the pooled prevalence of leptospirosis infection (186 cases) among malaria patients was 13% (95% CI: 9–18%, I²: 90.3%). The meta-analysis showed that malaria and leptospirosis co-infections occurred by chance (p: 0.434, OR: 1.4, 95% CI: 0.6–3.28, I²: 85.2%). The prevalence of malaria in leptospirosis co-infection among febrile patients in the included studies was low. Co-infection was likely to occur by chance. However, as clinical symptoms of leptospirosis patients were non-specific and not distinguishable from symptoms of malaria patients, clinicians caring for febrile patients in an area where those two diseases are endemic should maintain a high index of suspicion for both diseases and whether mono-infections or co-infections are likely. Recognition of this co-infection may play an important role in reducing disease severity and treatment duration.

Viability and Infectivity of Plasmodium vivax Gametocytes in Short-Term Culture

The control and elimination of malaria caused by Plasmodium vivax both represent a great challenge due to the biological aspects of the species. Gametocytes are the forms responsible for the transmission of the parasite to the vector and the search for new strategies for blocking transmission are essential in a scenario of control and elimination The challenges in this search in regard to P. vivax mainly stem from the lack of a long-term culture and the limitation of studies of gametocytes. This study evaluated the viability and infectivity of P. vivax gametocytes in short-term culture. The samples enriched in gametocytes using Percoll (i), using magnetic-activated cell sorting (MACS®) (ii), and using non-enriched samples (iii) were evaluated. After the procedures, gametocytes were cultured in IMDM medium for up to 48 h. Cultured P. vivax gametocytes were viable and infectious for up to 48 h, however differences in viability and infectivity were observed in the samples after 12 h of culture in relation to 0 h. Percoll-enriched samples were shown to be viable in culture for longer intervals than those purified using MACS®. Gametocyte viability after enrichment procedures and short-term culture may provide new avenues in the development of methods for evaluating P. vivax TB.

Malaria Infection and Risk for Endemic Burkitt Lymphoma: A Systematic Review and Meta-Analysis

Background: Malaria infection is reportedly linked to endemic Burkitt lymphoma (eBL) in malaria-endemic areas. This study aimed to pool the overall risk (or odds) of eBL among children with previous or concurrent malaria infection. Methods: We searched PubMed, Web of Science, Scopus, and reference lists of publications for potentially relevant studies on malaria infection and eBL. The quality of the included studies was assessed using the Joanna Briggs Institute for case-control studies. Random-effects meta-analysis was used to summarize whether the odds of eBL can be increased by (1) malaria infection or (2) elevated titer of IgGs to malaria antigen. The level of heterogeneity was evaluated using Cochran’s Q statistic and I². The individual study data, pooled odds, and confidence interval (CI) were illustrated using the forest plot. Publication bias was assessed using funnel plots and Egger’s test. Results: Ten studies were included, reporting the number of malaria cases in eBL and non-eBL (5 studied malaria infection and the odds of eBL; five studied the burden of IgGs to malarial antigens and the odds of eBL). According to the meta-analysis results, the odds of eBL was not increased by malaria infection (p = 0.562, OR: 0.87, 95% CI: 0.54–1.39, I²: 93.5%, malaria in eBL: 604/1506 cases, malaria in non-eBL: 2117/4549 cases) and the elevated titer of IgGs to malaria antigen (p = 0.051, OR: 1.50, 95% CI: 1.00–2.25, I²: 89%, increased IgG titer in eBL: 1059/1736 cases, increased IgG titer in non-eBL: 847/1722 cases). In meta-regression analysis, sex was not a confounding factor for the effect size of malaria infection and eBL (p = 0.10) and that of increased IgGs and eBL (p = 0.80). Conclusions: Malaria infection and IgG titer elevation did not increase the risk for eBL among children. However, the included studies, which are only few, do not generally agree on this point. Therefore, the risk for eBL in children diagnosed with malaria should be investigated further by longitudinal studies to confirm our evidence-based approach.

The high risk of malarial recurrence in patients with Plasmodium-mixed infection after treatment with antimalarial drugs: a systematic review and meta-analysis

Background

Malaria mixed infections are often unrecognized by microscopists in the hospitals, and a delay or failure to treat Plasmodium-mixed infection may lead to aggravated morbidity and increased mortality. The present study aimed to quantify the pooled proportion and risk of malarial recurrences after the treatment of Plasmodium-mixed infection. The results of the study may provide benefits in the management of Plasmodium-mixed infection in co-endemic regions.

Methods

This systematic review and meta-analysis searched the international Prospective Register of Systematic Reviews (PROSPERO; ID = CRD42020199709), MEDLINE, Web of Science, and Scopus for potentially relevant studies in any language published between January 1, 1936, and July 20, 2020, assessing drug efficacy in patients with Plasmodium-mixed infection. The primary outcome was the pooled prevalence of Plasmodium parasitemia after initiating antimalarial treatment for Plasmodium-mixed infection. The secondary outcome was the pooled risk ratio (RR) of malarial recurrence in Plasmodium-mixed infection compared with those in Plasmodium falciparum and Plasmodium vivax mono-infection. The pooled analyses were calculated by random-effects meta-analysis. After the initial treatment in different days of recurrences (≤ 28 days or > 28 days), the risk of Plasmodium parasitemia was compared in subgroup analysis.

Results

Out of 5217 screened studies, 11 were included in the meta-analysis, including 4390 patients from six countries. The pooled prevalence of all recurrences of Plasmodium-mixed parasitemia was 30% (95% confidence interval (CI) 16–43; I²: 99.2%; 11 studies). The RR of malarial recurrence within 28 days after the initial treatment (clinical treatment failure) of Plasmodium-mixed parasitemia compared with the treatment of P. falciparum was 1.22 (p: 0.029; 95% CI 1.02–1.47; Cochran Q: 0.93; I²: 0%; six studies), while there was no significant difference in the risk of recurrence 28 days after initial treatment compared with the treatment of P. falciparum (p: 0.696, RR: 1.14; 95% CI 0.59–2.18; Cochran Q < 0.05; I²: 98.2%; four studies). The subgroup analysis of antimalarial drugs showed that significant malarial recurrence within 28 days was observed in patients treated with artemisinin-based combination therapies (ACTs) with no significant heterogeneity (p: 0.028, RR: 1.31; 95% CI 1.03–1.66; Cochran Q: 0.834; I²: 0%).

Conclusions

The present findings showed a high prevalence of malarial recurrence after the initial treatment of Plasmodium-mixed infection. Moreover, significant malaria recurrence of mixed infection occurred within 28 days after treatment with ACTs.

Graphic Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04792-5.

Comparison of Plasmodium ovale curtisi and Plasmodium ovale wallikeri infections by a meta-analysis approach

Malaria caused by Plasmodium ovale species is considered a neglected tropical disease with limited information about its characteristics. It also remains unclear whether the two distinct species P. ovale curtisi and P. ovale wallikeri exhibit differences in their prevalence, geographic distribution, clinical characteristics, or laboratory parameters. Therefore, this study was conducted to clarify these differences to support global malaria control and eradication programs. Studies reporting the occurrence of P. ovale curtisi and P. ovale wallikeri were explored in databases. Differences in proportion, clinical data, and laboratory parameters between the two species were estimated using a random-effects model and expressed as pooled odds ratios (ORs), mean difference (MD), or standardized MD depending on the types of extracted data. The difference in geographical distribution was visualized by mapping the origin of the two species. A total of 1453 P. ovale cases extracted from 35 studies were included in the meta-analysis. The p-value in the meta-analyses provided evidence favoring a real difference between P. ovale curtisi malaria cases (809/1453, 55.7%) and P. ovale wallikeri malaria cases (644/1453, 44.3%) (p: 0.01, OR 1.61, 95% CI 0.71-3.63, I2: 77%). Subgroup analyses established evidence favoring a real difference between P. ovale curtisi and P. ovale wallikeri malaria cases among the imported cases (p: 0.02, 1135 cases). The p value in the meta-analyses provided evidence favoring a real difference in the mean latency period between P. ovale curtisi (289 cases) and P. ovale wallikeri malaria (266 cases) (p: 0.03, MD: 27.59, 95% CI 1.99-53.2, I2: 94%), total leukocyte count (p < 0.0001, MD: 840, 95% CI 610-1070, I2: 0%, two studies) and platelet count (p < 0.0001, MD: 44,750, 95% CI 2900-60,500, I2: 32%, three studies). Four continents were found to have reports of P. ovale spp., among which Africa had the highest number of reports for both P. ovale spp. in its 37 countries, with a global proportion of 94.46%, and an almost equal distribution of both P. ovale spp., where P. ovale curtisi and P. ovale wallikeri reflected 53.09% and 46.90% of the continent's proportion, respectively. This is the first systematic review and meta-analysis to demonstrate the differences in the characteristics of the two distinct P. ovale species. Malaria caused by P. ovale curtisi was found in higher proportions among imported cases and had longer latency periods, higher platelet counts, and higher total leukocyte counts than malaria caused by P. ovale wallikeri. Further studies with a larger sample size are required to confirm the differences or similarities between these two species to promote malaria control and effective eradication programs.

Clinical spectrum and predictors of severe Plasmodium vivax infections at a tertiary care center in North India

Traditionally attributed only to Plasmodium falciparum, Plasmodium vivax has recently been reported to cause a significant burden of complicated malaria cases. The present study aimed to delineate the clinical spectrum and identify predictors for severe disease. This was a prospective observational cohort study conducted at a tertiary care hospital in North India. Patients with acute febrile illness (AFI) aged at least 14 years were included if they were diagnosed with vivax malaria based on rapid kits or peripheral smears. Clinical data and investigations during hospital stay was recorded. 439 cases of acute febrile illness were screened, of whom 50 (11%) were diagnosed with malaria including eight P. falciparum infections. Forty-two vivax malaria cases, 22 (52%) of whom were severe, were followed till discharge or death. The median age of the cohort was 24.5 years (Q1-Q3, 19-36 years), including a total of 29 males (69%). Severe malaria was more frequently associated with historical complaints of oliguria or dyspnea, and examination findings of pallor, splenomegaly or altered sensorium. The following five factors were identified to predict severe disease: prolonged illness over 7 days, symptoms of oliguria or dyspnea, examination findings of pallor or crepitations on auscultation. Malaria accounts for 1 in 10 cases of AFI at our North Indian tertiary care center and approximately half of them present with severe disease. Prolonged duration of disease prior to presentation is a modifiable predictor for severe disease and should be targeted for reducing morbidity.

Comorbidity of Geo-Helminthes among Malaria Outpatients of the Health Facilities in Ethiopia: Systematic Review and Meta-Analysis

Background: Coinfection of malaria and intestinal helminths affects one third of the global population, largely among communities with severe poverty. The spread of these parasitic infections overlays in several epidemiological locations and the host shows different outcomes. This systematic review and meta-analysis determine the pooled prevalence of malaria and intestinal helminthiases coinfections among malaria suspected patients in Ethiopia. Methods: Primary studies published in English language were retrieved using appropriate search terms on Google Scholar, PubMed/MEDLINE, CINHAL, Scopus, and Embase. The Joanna Briggs Institute Meta-Analysis of Statistics Assessment and Review Instrument (JBI-MAStARI) was used for critical appraisal of studies. A pooled statistical meta-analysis was conducted using STATA Version 14.0 software. The heterogeneity and publication bias were assessed using the I2 statistics and Egger’s test, respectively. Duval and Tweedie’s nonparametric trim and fill analysis using the random-effect analysis. The Random effects model was used to estimate the summary prevalence of comorbidity of malaria and soil transmitted helminthiases and the corresponding 95% confidence intervals (CI). The review protocol has registered in PROSPERO number CRD42019144803. Results: We identified ten studies (n = 6633 participants) in this study. The overall pooled result showed 13% of the ambulatory patients infected by malaria and intestinal helminths concurrently in Ethiopia. The pooled prevalence of Plasmodium falciparum and Plasmodium vivax, and mixed infections were 12, 30, and 6%, respectively. The most common intestinal helminth parasites detected were Hookworm, Ascaris lumbricoides, and Tirchuris trichiura. Conclusions: The comorbidity of malaria and intestinal helminths causes lower hemoglobin level leading to maternal anemia, preterm delivery, and still birth in pregnant women and lactating mother. School-aged children and neonates coinfected by plasmodium species and soil transmitted helminths develop cognitive impairment, protein energy malnutrition, low birth weight, small for gestational age, and gross motor delay. The Ministry of Health of Ethiopia and its international partners working on malaria elimination programs should give more emphasis to the effect of the interface of malaria and soil transmitted helminths, which calls for an integrated disease control and prevention.