Evaluation of C-reactive protein and haptoglobin as malaria episode markers in an area of high transmission in Africa

Performance evaluation of a combination Plasmodium dual-antigen CRP rapid diagnostic test in Lambaréné, Gabon

PURPOSE

The consequent use of malaria rapid diagnostic tests (RDTs) preceding a treatment decision has improved the global management of malaria. A combination RDT, including an inflammation marker to potentially guide antibiotic prescription, could improve the management of acute febrile illness (AFI).

METHODS

We performed a prospective, cross-sectional study in Gabon evaluating the STANDARD Malaria/CRP DUO (S-DUO) RDT. Participants aged 2 to 17 years with fever at presentation and/or a history of fever < 7 days were enrolled. Expert microscopy, SD Bioline Malaria Ag P.f/Pan test for malaria detection, and NycoCard CRP device for CRP were used as comparators. AFI cases were classified on a spectrum encompassing bacterial vs. non-bacterial infection.

RESULTS

415 participants with AFI were enrolled. S-DUO RDT sensitivity and specificity for malaria detection vs. microscopy were 99·1% (95·2-100%) and 72·7% (64·3-80·1%); and for CRP detection (20 mg/L and above) 86·9% (80-92%) and 87% (79·2-92·7%), respectively. The difference in CRP levels between bacterial infection (mean = 41·2 mg/L) and other causes of fever, measured from our study population using the Nycocard device, was statistically significant (p < 0·01); CRP precision-recall AUC to distinguish bacterial infection class vs. non-bacterial classifications was 0·79.

CONCLUSION

S-DUO RDT is suitable for malaria detection in moderate-to-high malaria transmission settings such as in Lambaréné; however, a CRP band detection limit > 40 mg/L is more adequate for indication of antibiotic prescription for AFI cases in Gabon.

The roles of betulinic acid on circulating concentrations of creatine kinase and immunomodulation in mice infected with chloroquine-susceptible and resistant strains of Plasmodium berghei

Complete malarial therapy depends largely on the immunological and inflammatory response of the host to the invading potentials of malarial parasite. In this study, we evaluated the roles of betulinic acid on immunological response, anti-inflammatory potentials, cardiac and skeletal muscle tissue damage in mice infected with chloroquine susceptible (NK 65) and resistant (ANKA) strains of Plasmodium berghei. Serum Interleukins 1β and 6 (IL-1β, IL-6), tumour necrosis factor alpha (TNF-α), immunoglobulins G and M (IgG and IgM), C-reactive protein (CRP) and creatine kinase (CK) were determined using ELISA technique. Aspartate aminotransferase (AST), alanine aminotransferase (ALT) and gamma glutammyl transferase (GGT) were determined using ELISA technique. The results showed that betulinic acid decreased the levels of IL-1β, IL-6, TNF-α and CRP relative to the infected control. The IgG and IgM levels significantly increased in both models while CK did not decrease significantly in both models although serum AST, ALT and GGT significantly decreased compared to the infected control. These results showed that betulinic acid possessed anti-inflammatory, immunomodulatory and remediating effects on tissue damage. Furthermore, the decrease in activity of CK brought about by betulinic acid is indicative of decrease in cardiac and skeletal muscle injury which is a major pathological concern in Plasmodium infection and treatment.

C-reactive protein as an early biomarker for malaria infection and monitoring of malaria severity: a meta-analysis

This study investigated whether C-reactive protein (CRP) can be used as a marker for the early detection and monitoring of malaria severity. Potentially relevant studies were searched in Medline (PubMed), Scopus, and Web of Science. Differences in CRP between (1) severe malaria and uncomplicated malaria, (2) uncomplicated malaria and asymptomatic malaria, (3) uncomplicated malaria and febrile/healthy controls, and (4) asymptomatic malaria and febrile/healthy controls were estimated using random-effects models. Twenty-nine studies were included for meta-analysis. The results of meta-analysis demonstrated higher mean CRP levels in (1) patients with severe malaria compared with uncomplicated malaria (p < 0.001, standard mean difference [SMD]: 1.52, 95% confidence interval [CI]: 0.91-2.12, I2: 95.1%), (2) patients with uncomplicated malaria than in those with asymptomatic malaria (p: 0.001, SMD: 1.65, 95% CI: 0.67-2.62, I2: 96.7%), (3) patients with uncomplicated malaria compared with febrile/healthy controls (p < 0.001, SMD: 2.38, 95% CI: 1.37-3.40, I2: 98.5%), and (4) patients with asymptomatic malaria compared with febrile/healthy controls (p < 0.001, SMD: 2.55, 95% CI: 1.60-3.50, I2: 99.2%). This study demonstrated CRP levels are a biomarker for the early detection and monitoring of malaria severity.

High-Sensitivity C-Reactive Protein: A Potential Ancillary Biomarker for Malaria Diagnosis and Morbidity

Background

Malaria remains an important cause of morbidity and mortality in Africa. Previous studies that assessed C-reactive protein (CRP) have centered on the conventional method. This study evaluated the usefulness of high-sensitivity CRP (hs-CRP) in malaria diagnosis and morbidity in a pediatric population in Ghana.

Methodology

A total of 267 subjects (100 microscopically proven nonmalarial parasitaemics as controls and 167 plasmodium parasitaemic subjects as cases), between the ages of 7 months and 18 years, were recruited for this case-control study. Blood samples were collected for malaria parasite density by microscopic examination; full blood count, electrolytes, and liver function tests using an automated analyzer; and hs-CRP levels by sandwich ELISA method.

Results

The median hs-CRP concentration was lowest in the control group and increased significantly from low to high parasitaemia. The median hs-CRP level was significantly higher in high malaria parasitaemia compared to moderate and low malaria parasitaemia. Increasing hs-CRP cutoff (3.12-4.64 mg/L) presented with increasing specificity (79.3-93.1%) and sensitivity (96.4%-97.4%), except for moderate parasitaemia where a decline in sensitivity (80.9%) was observed. However, hs-CRP had relatively lower PPV but high NPV at low parasitaemia while both the PPV and NPV were moderate in moderate parasitaemia.

Conclusion

hs-CRP yielded a high sensitivity, specificity, and accuracy for low, moderate, and high-grade malaria, respectively, and thus may serve as an effective supplementary diagnostic and prognostic biomarker for Plasmodium parasite infection. However, hs-CRP might not be readily useful yet for diagnostic purposes in hospitals due to the relatively low PPV and NPV for low and moderate parasitaemia and thus necessitates further studies in larger cohorts.

Chemopreventive and remediation effect of Adansonia digitata L. Baobab (Bombacaceae) stem bark extracts in mouse model malaria

ETHNOPHARMACOLOGICAL RELEVANCE

Adansonia digitata L. Baobab (Bombacaceae) solvent extracts have been reported to possess medicinal properties and are currently been used traditionally for the treatment of malaria and several other diseases and infection; however few reports exist in literature that provides supportive scientific evidence in favour of its medicinal use.

AIM OF THE STUDY

This study investigated the efficacy of Adansonia digitata stem bark extract in offering protection against experimental malaria and also examined its remediation effect when administered after established infection.

MATERIALS AND METHODS

Weanling albino mice were used in the study. The mice were transfected intraperitonially with an inoculums size of 1× 10⁷ of chloroquine susceptible strain of plasmodium berghei infected erythrocytes. Mechanisms of action of the extract were investigated by measuring the degree of tissue peroxidation and tissue antioxidant status. Severity of malaria was determined by measuring the serum C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-α), and serum and tissue Alkaline phosphatase (ALP) activity.

RESULTS

There was a significant increase in serum CRP, TNF-α concentrations and serum and tissue ALP activity in the control mice following Plasmodium berghei infection. All the treatment had effect on the growth of Plasmodium berghei parasites in mice. The extracts showed a significant dose dependent increase packed cell volume (PCV), percentage chemosupression/clearance and a significant decrease in percentage parasitemia at the two doses when administered after established infection. Methanolic extract (MEAD) at 400mg/kg exhibited the highest chemosupressive activity. The extract significantly reduced the degree of tissue peroxidation, increased the level of reduced glutathione (GSH), catalase and superoxide dismutase activity. Administration of the extract after established infection reduced serum CRP and TNF-α concentrations and serum and tissue ALP activity.

CONCLUSION

Our study suggests that Adansonia digitata protects against Plasmodium berghei induced-malaria, and that administration of the extract after established infection reduced malaria progression.

Profile of C-reactive protein, white cells and neutrophil populations in febrile children from rural north-eastern Tanzania

Introduction

C-reactive protein (CRP), white blood cell (WBC) and absolute neutrophil counts (ANC) are important inflammatory biomarkers in the early diagnosis of infections. However, little is known on their profile and usefulness in fever case management in children attending outpatient clinic in rural north-eastern Tanzania.

Methods

Patients aged between 2 and 59 months presenting with fever at Korogwe District Hospital were enrolled. Venous blood was collected for evaluation of serum CRP, WBC and ANC. Individual patient diagnosis was based on integrated management of childhood illness (IMCI) guidelines and laboratory investigations (blood and urine cultures).

Results

A total of 867 patients were enrolled, out of which 691 (79.7%) had complete clinical and laboratory data available for analysis. Acute upper respiratory tract infection 284 (41.1%), acute gastroenteritis 127 (18.4%) and pneumonia 100 (14.5%) were the most frequent diagnoses. The geometric mean levels of serum CRP, WBC and ANC were 10.4 (95% CI: 9.2 - 11.8), 11.5 (95% CI: 11.1 - 11.9) and 5.5 (95% CI: 5.2 - 5.8), respectively. CRP≤20, WBC≤15 (10³cells/µL) and ANC≤10 10³cells/µL) were observed in the majority of the patients with upper respiratory tract infection, pneumonia, acute gastroenteritis and non-specific febrile illness. Only serum CRP levels were positively correlated with positive blood cultures at a calculated cut-off value of 37.3 mg/L, giving a specificity of 77.8% and sensitivity of 74.2%.

Conclusion

CRP assessment together with IMCI guidelines may be useful in assisting the diagnosis and management of paediatric febrile infections in Tanzania.

Elevated Values of C-Reactive Protein Induced by Imported Infectious Diseases: A Controlled Cross-Sectional Study of 11,079 Diseased German Travelers Returning from the Tropics and Subtropics

The present controlled cross-sectional study aimed to assess elevated values of C-reactive protein (CRP), a positive acute-phase protein, induced by imported infectious diseases (IDs) seen in patients consulting the University of Munich (1999-2015) after being in the tropics/subtropics. The analysis investigated data sets from 11,079 diseased German travelers (cases) returning from Latin America (1,986), Africa (3,387), and Asia (5,706), and from 714 healthy Germans who had not recently traveled (controls). The proportions of elevated values of CRP (> 0.5 mg/dL) were significantly larger among cases (44.3%) than among controls (20.7%). Among cases, this proportion was largest among males (49.2%) in comparison to females (39.9%), among travelers with short travel duration of 1-14 days (49.6%) in comparison to travelers with a travel duration of > 180 days (30.8%), and with travel destination in Africa (47.0%) in comparison to Asia (44.2%) and Latin America (39.9%), among all-inclusive travelers (47.4%) in comparison to business travelers (46.7%) and backpackers (44.1%), and among patients presenting with fever (70.9%) and arthralgia (54.3%). The study identified various imported IDs with significantly larger proportions of elevated values of CRP including viral (cytomegalovirus infection [94.7%], influenza [88.9%], infectious mononucleosis [71.8%]), bacterial (typhoid fever [100%], paratyphoid fever [92.9%], shigellosis [76.8%], rickettsiosis [74.2%], Salmonella enteritis [71.3%], Campylobacter infection [68.7%]), and protozoan (vivax malaria [100%], ovale malaria [100%], falciparum malaria [95.4%], noninvasive Entamoeba infection [65.9%]) IDs. This study demonstrates that elevated values of CRP can be a useful laboratory finding for travelers returning from the tropics/subtropics, as these findings are typically caused mainly by certain imported bacterial IDs, but also by viral and protozoan IDs.

Is asymptomatic malaria really asymptomatic? Hematological, vascular and inflammatory effects of asymptomatic malaria parasitemia

Asymptomatic malaria infections are highly prevalent in malaria endemic regions and most of these infections remain undiagnosed and untreated. Whereas conventional malaria symptoms are by definition absent, little is known on the more subtle health consequences of these infections. The aim of our study was to analyze the hematologic, vascular and inflammatory effects of patent and subpatent asymptomatic malaria parasitemia in children and adults on the Indonesian island Sumba. Both children and adults with parasitemia had increased high-sensitive C-reactive protein levels compared to aparasitemic individuals. In addition, children, but not adults with parasitemia also had lower platelet counts and Hb levels and higher levels of von Willebrand factor and platelet factor-4, markers of endothelial and platelet activation, respectively. These findings suggest that asymptomatic malaria infections have subtle health consequences, especially in children, and should be regarded as potentially harmful.

Comparison of clinical characteristics and laboratory findings of malaria, dengue, and enteric fever in returning travelers: 8-year experience at a referral center in Tokyo, Japan

BACKGROUND

Without specific symptoms, diagnosis of febrile illness in returning travelers is challenging. Dengue, malaria, and enteric fever are common causes of fever in returning travelers and timely and appropriate treatment is important. However, differentiation is difficult without specific diagnostic tests.

METHODS

A retrospective study was conducted at the National Centre for Global Health and Medicine (NCGM) from April 2005 to March 2013. Febrile travelers returning from overseas who were diagnosed with dengue, malaria, or enteric fever were included in this study. Clinical characteristics and laboratory findings were compared for each diagnosis.

RESULTS

During the study period, 86 malaria, 85 dengue, and 31 enteric fever cases were identified. The mean age of the study cohort was 33.1 ± 12 years and 134 (66.3%) study participants were male. Asia was the most common area visited by returning travelers with fevers (89% of dengue, 18.6% of malaria, and 100% of enteric fever cases), followed by Africa (1.2% of dengue and 70.9% of malaria cases). Clinical characteristics and laboratory findings were significantly different among each group with each diagnosis. Decision tree models revealed that returning from Africa and CRP levels <10 mg/L were factors specific for diagnosis of malaria and dengue fever, respectively.

CONCLUSION

Clinical manifestations, simple laboratory test results, and regions of travel are helpful to distinguish between dengue, malaria, and enteric fever in febrile returning travelers with non-specific symptoms.

Identification of protein markers in patients infected with Plasmodium knowlesi, Plasmodium falciparum and Plasmodium vivax

Malaria is caused by parasitic protozoans of the genus Plasmodium and is one of the most prevalent infectious diseases in tropical and subtropical regions. For this reason, effective and practical diagnostic methods are urgently needed to control the spread of malaria. The aim of the current study was to identify a panel of new malarial markers, which could be used to diagnose patients infected with various Plasmodium species, including P. knowlesi, P. vivax and P. falciparum. Sera from malaria-infected patients were pooled and compared to control sera obtained from healthy individuals using the isobaric tags for relative and absolute quantitation (iTRAQ) technique. Mass spectrometry was used to identify serum proteins and quantify their relative abundance. We found that the levels of several proteins were increased in pooled serum from infected patients, including cell adhesion molecule-4 and C-reactive protein. In contrast, the serum concentration of haptoglobin was reduced in malaria-infected individuals, which we verified by western blot assay. Therefore, these proteins might represent infectious markers of malaria, which could be used to develop novel diagnostic tools for detecting P. knowlesi, P. vivax and P. falciparum. However, these potential malarial markers will need to be validated in a larger population of infected individuals.

Deletion of C-reactive protein ameliorates experimental cerebral malaria?

BACKGROUND

C-reactive protein (CRP) level correlates with parasitemia and severity of malaria, but whether this reflects causality remains unknown.

METHODS

Using CRP-transgenic and CRP-deficient mice we compared the onset and severity of experimental cerebral malaria (ECM) induced by Plasmodium berghei ANKA (PbA).

RESULTS

CRP-deficient mice were most resistant to ECM.

CONCLUSIONS

CRP might contribute to the development of cerebral malaria, rather than protect against it.

The usefulness of serum C-reactive protein and total bilirubin levels for distinguishing between dengue fever and malaria in returned travelers

The clinical manifestations of dengue fever (DF) and malaria are similar. Specific diagnostic tests are not always available. A retrospective study to compare the laboratory results of malaria and DF was conducted at the National Center for Global Health and Medicine in Japan from January of 2005 to March of 2013. Febrile returned travelers from overseas diagnosed with malaria or DF were included; 86 malaria and 85 DF cases were identified. C-reactive protein (CRP) and total bilirubin (T-bil) had high area under the receiver operating characteristic curves (> 0.9). A cutoff value of CRP > 2.4 mg/dL to predict malaria as opposed to DF had a sensitivity of 91.9% (95% confidence interval [95% CI] = 83.9-96.7%) and specificity of 90.6% (95% CI = 82.3-95.8%). A cutoff value of T-bil > 0.9 mg/dL to predict malaria as opposed to DF had a sensitivity of 73.8% (95% CI = 62.7-83%) and a specificity of 95.1% (95% CI = 88-98.6%). CRP and T-bil are useful to distinguish between DF and malaria in returned travelers.

Discriminating malaria from dengue fever in endemic areas: clinical and biological criteria, prognostic score and utility of the C-reactive protein: a retrospective matched-pair study in French Guiana

Background

Dengue and malaria are two major public health concerns in tropical settings. Although the pathogeneses of these two arthropod-borne diseases differ, their clinical and biological presentations are unspecific. During dengue epidemics, several hundred patients with fever and diffuse pain are weekly admitted at the emergency room. It is difficult to discriminate them from patients presenting malaria attacks. Furthermore, it may be impossible to provide a parasitological microscopic examination for all patients. This study aimed to establish a diagnostic algorithm for communities where dengue fever and malaria occur at some frequency in adults.

Methodology/Principal Findings

A sub-study using the control groups of a case-control study in French Guiana – originally designed to compare dengue and malaria co-infected cases to single infected cases – was performed between 2004 and 2010. In brief, 208 patients with malaria matched to 208 patients with dengue fever were compared in the present study. A predictive score of malaria versus dengue was established using .632 bootstrap procedures. Multivariate analysis showed that male gender, age, tachycardia, anemia, thrombocytopenia, and CRP>5 mg/l were independently associated with malaria. The predictive score using those variables had an AUC of 0.86 (95%CI: 0.82–0.89), and the CRP was the preponderant predictive factor. The sensitivity and specificity of CRP>5 mg/L to discriminate malaria from dengue were of 0.995 (95%CI: 0.991–1) and 0.35 (95%CI 0.32–0.39), respectively.

Conclusions/Significance

The clinical and biological score performed relatively well for discriminating cases of dengue versus malaria. Moreover, using only the CRP level turned to be a useful biomarker to discriminate feverish patients at low risk of malaria in an area where both infections exist. It would avoid more than 33% of unnecessary parasitological examinations with a very low risk of missing a malaria attack.

The authors present a retrospective matched-pair study on dengue and malaria performed in French Guiana. These two infections are major public health concerns in tropical regions, especially in South America and Southeast Asia, where they affect neglected populations which makes them interesting to be published in a journal aiming to publish about neglected tropical diseases. Although the pathogeneses of these two arthropod-borne differ, their clinical and biological presentations are unspecific. During dengue epidemics, hundreds of patients are admitted weekly with diffuse pains and fever at the emergency room. Among them, it is difficult to accurately distinguish malaria attacks, which are far less frequent than dengue fever cases. Moreover, it may be impossible to provide a parasitological microscopic examination for all patients. We believe the results of the present study, based on a sample of n = 416 individual are worthwhile as they support evidence that biological factors can help to discriminate between the two, in areas where they co-exist in endemic areas. A simple prognostic score based on clinical and biological criteria was built, interesting and easy-to-use for physicians in tropical areas.

Low C-reactive protein levels in a traditional West-African population living in a malaria endemic area

Background

C-reactive protein (CRP) levels are reported to be elevated in populations of African descent living in affluent environments compared to populations of European ancestry. However, the natural history of CRP levels in populations of African descent living under adverse environments remains largely unknown.

Methods

CRP levels were measured with a high sensitivity assay in 624 apparently healthy individuals who contributed blood as part of a study on innate immune responsiveness in a traditional Ghanaian population living under adverse environmental conditions in a malaria endemic area. As a comparison, we included CRP measurements from 2931 apparently healthy individuals from the Dutch population that were included in the same batch of CRP analyses. Associations between CRP and body mass index (BMI), immune responsiveness, and P. falciparum parasitaemia were investigated.

Results

In an age- and sex-adjusted model, CRP levels were 0.54 mg/L lower in the Ghanaian compared to the Dutch cohort (1.52 vs. 0.98 mg/L, p<0.001). When accounting for the substantially higher average BMI in the Dutch compared to the Ghanaians (25.6 vs. 18.4 kg/m²) the difference in CRP levels disappeared. BMI associated positively with CRP in the Dutch but not in the Ghanaians. In individuals with an acute phase response, CRP levels were higher in the Ghanaian compared to the Dutch cohort (24.6 vs. 17.3 mg/L, p = 0.04). Levels of CRP were positively related to immune responsiveness and P. falciparum parasitaemia (all p<0.001) among Ghanaians.

Conclusions

Our study demonstrates that West-Africans do not exhibit an inherently high inflammatory state. The role of genes, environment and gene-environment interaction in explaining reports of elevated CRP levels in populations of African ancestry when compared to other ethnicities living in affluent environments thus merits further investigation.

Bacterial coinfections in travelers with malaria: rationale for antibiotic therapy

Malaria predisposes children in areas where malaria is endemic to concurrent bacteremia, often with severe outcomes. The importance of bacterial coinfections in patients diagnosed with malaria in nonendemic settings has, however, not been reported. A retrospective analysis of microbiology data was performed in 755 travelers diagnosed with malaria in Sweden. Bacterial cultures from blood and other locations were correlated to clinical outcome and antibiotic treatment. Blood cultures were drawn from 417 (55%) patients (88% of whom were >15 years old), and bacterial isolates of clinical relevance (Salmonella enterica serovar Enteritidis and Escherichia coli) were detected in 2 patients (0.3%). Cultures from other locations (mainly urine, nasopharyngeal, and fecal samples) were obtained from 44% of the patients with 4.9% positivity. Of the 38 patients given antibiotics, 47% had neither severe malaria nor positive cultures and/or radiology signs indicative of treatment. C-reactive protein levels were associated with bacterial infections but had only a fair predictive value. Bacterial coinfections are uncommon among travelers with malaria. These data suggest a weaker association between malaria and bacteremia than previously described in endemic settings and might indicate different patient populations with different pathophysiological mechanisms and microbial environments. The study supports a restrictive antibiotic policy in returning travelers with malaria.

Quality and reliability of current malaria diagnostic methods

Malaria is a life threatening disease with a major impact on global health. The WHO declared an early diagnosis as one of the most important steps to fight the disease. The quality and the reliability of test results depend on the diagnostic tools used. Not every test meets the needs in every situation. PCR tests have the best sensitivity and specifity but are not as rapid as other tests and also due to the costs not available everywhere. The 'gold standard' method is to check stained blood slides, thick films require experienced persons to obtain correct results. So-called rapid tests are only additional tools no matter whether they are based on the detection of antigens, enzymes or plasmodial DNA by fluorescent staining. Some other blood bound markers may also provide a hint but are no sufficient tool for malaria diagnosis.

Study of C reactive protein as a prognostic marker in malaria from Eastern India

Background:

C-reactive protein (CRP) is useful as marker of severity in malaria. African studies have shown that serum CRP levels correlate with parasite burden and complications in malaria, especially falciparum. However, there are very few data on CRP levels in Indian malaria patients.

Materials and Methods:

We assessed CRP levels in malaria patients at presentation and studied for any relation of CRP levels with subsequent prognosis. Statistical tests included student's t-test, Mann Whitney U test, and chi square test, all with 2-tailed analyzes.

Results:

Of 71 patients in our study, 42 (59.1%) were infected with P. falciparum. 23 (32.4%) patients needed admission and 10 (14.1%) died. Average CRP levels were quite high in malaria patients (31.29 ± 20.4 mg/L). There was no significant difference in CRP between vivax and falciparum cases. Admitted patients had significantly higher CRP levels compared to those treated on outdoor basis (47.11 ± 19.13 vs. 23.71 ± 16.35 mg/L; P < 0.0001). 8 patients were admitted with multiple complications. They had significantly high CRP level compared to those with 1 complication (P = 0.015). Also, patients who died had higher CRP levels compared to survivors (P = 0.000346). CRP levels at presentation showed positive correlation with duration of hospital stay (r = 0.59; P < 0.05). CRP levels >35 mg/L was highly sensitive in predicting mortality.

Conclusion:

Our study in Indian population corroborates the findings in African studies regarding prognostic role of CRP in malaria. CRP is an effective biomarker in assessing malaria severity and also for follow-up.

Effect of α(+)-thalassaemia on episodes of fever due to malaria and other causes: a community-based cohort study in Tanzania

Background

It is controversial to what degree α⁺-thalassaemia protects against episodes of uncomplicated malaria and febrile disease due to infections other than Plasmodium.

Methods

In Tanzania, in children aged 6-60 months and height-for-age z-score < -1.5 SD (n = 612), rates of fevers due to malaria and other causes were compared between those with heterozygous or homozygotes α⁺-thalassaemia and those with a normal genotype, using Cox regression models that accounted for multiple events per child.

Results

The overall incidence of malaria was 3.0/child-year (1, 572/526 child-years); no differences were found in malaria rates between genotypes (hazard ratios, 95% CI: 0.93, 0.82-1.06 and 0.91, 0.73-1.14 for heterozygotes and homozygotes respectively, adjusted for baseline factors that were predictive for outcome). However, this association strongly depended on age: among children aged 6-17 months, those with α⁺-thalassaemia experienced episodes more frequently than those with a normal genotype (1.30, 1.02-1.65 and 1.15, 0.80-1.65 for heterozygotes and homozygotes respectively), whereas among their peers aged 18-60 months, α⁺-thalassaemia protected against malaria (0.80, 0.68-0.95 and 0.78, 0.60-1.03; p-value for interaction 0.001 and 0.10 for hetero- and homozygotes respectively). No effect was observed on non-malarial febrile episodes.

Conclusions

In this population, the association between α⁺-thalassaemia and malaria depends on age. Our data suggest that protection by α⁺-thalassaemia is conferred by more efficient acquisition of malaria-specific immunity.

Erythropoietin levels are not independently associated with malaria-attributable severe disease in Mozambican children

Background

Severe malaria is difficult to differentiate from other forms of malaria or other infections with similar symptoms. Any parameter associated to malaria-attributable severe disease could help to improve severe malaria diagnosis.

Methodology

This study assessed the relation between erythropoietin (EPO) and malaria-attributable severe disease in an area of Mozambique with moderate malaria transmission. 211 children <5 years, recruited at Manhiça District Hospital or in the surrounding villages, were included in one of the following groups: severe malaria (SM, n = 44), hospital malaria without severity (HM, n = 49), uncomplicated malaria (UM, n = 47), invasive bacterial infection without malaria parasites (IBI, n = 39) and healthy community controls (C, n = 32). Malaria was diagnosed by microscopy and IBI by blood/cerebrospinal fluid culture.

Principal Findings

Mean EPO concentration in the control group was 20.95 U/l (SD = 2.96 U/l). Values in this group were lower when compared to each of the clinical groups (p = 0.026 C versus UM, p<0.001 C vs HM, p<0.001 C vs SM and p<0.001 C vs IBI). In the 3 malaria groups, values increased with severity [mean = 40.82 U/l (SD = 4.07 U/l), 125.91 U/l (SD = 4.99U/l) and 320.87 U/l (SD = 5.91U/l) for UM, HM and SM, respectively, p<0.001]. The IBI group [mean = 101.75 U/l (SD = 4.12 U/l)] presented lower values than the SM one (p = 0.002). In spite of the differences, values overlapped between study groups and EPO levels were only associated to hemoglobin. Hemoglobin means of the clinical groups were 93.98 g/dl (SD = 14.77 g/dl) for UM, 75.96 g/dl (SD = 16.48 g/dl) for HM, 64.34 g/dl (SD = 22.99 g/dl) for SM and 75.67 g/dl (SD = 16.58 g/dl) for IBI.

Conclusions

Although EPO levels increase according to malaria severity and are higher in severe malaria than in bacteremia, the utility of EPO to distinguish malaria-attributable severe disease is limited due to the overlap of values between the study groups and the main role of hemoglobin in the expression of EPO.

Association of a single nucleotide polymorphism in the C-reactive protein gene (-286) with susceptibility to Plasmodium falciparum malaria

The role of inflammation in malaria pathogenesis is not fully understood, although C-reactive protein (CRP) may have a negative influence on host immunity to infections. An upstream polymorphism, -286 (C > T > A), in the CRP gene is known to influence CRP levels. In this study, a cohort of 192 Sudanese donors, followed for malaria infection for 9 years, had their CRP -286 gene locus genotyped by pyrosequencing. The number of malaria episodes experienced by each individual over the study period was used as an index for malaria susceptibility. The prevalence of the CRP alleles A, C and T were 21%, 52% and 27%, respectively. Importantly, the A-allele, unlike the C- and T-alleles or CRP genotypes, was significantly associated with an increased number of malaria episodes, P = 0.007. The proportion of A-allele carriers among donors not known to have had malaria during the study period was 18%, whereas it was 43% and 63% among donors who had experienced 1-4 and > or =5 malaria episodes, respectively, over the same period (P = 0.002). Furthermore, the A-allele was associated with higher parasite counts. In conclusion, the CRP -286 A-allele was associated with an increased susceptibility to uncomplicated Plasmodium falciparum malaria.

Marked differences in CRP genotype frequencies between the Fulani and sympatric ethnic groups in Africa

Background

C-reactive protein (CRP) is an acute phase protein that can activate various immune cells and bind to certain Fcγ receptors. The latter may compete with the binding of IgG antibodies to these receptors and could thereby interfere with the antigen-specific immune response. Polymorphisms in the promoter region of the CRP gene have been strongly associated with the plasma concentration of CRP. The known lower susceptibility to malaria in the Fulani ethnic group, as compared to their sympatric neighbours in Africa, has been linked to different genetic backgrounds. The present study was performed to investigate if polymorphisms in the CRP gene could contribute to the lower susceptibility to malaria seen in the Fulani ethnic group.

Methods

The CRP -717 T>C, -286 C>T>A, and +1444 C>T polymorphisms were analysed in asymptomatic Fulani and non-Fulani individuals from Mali and Sudan using Pyrosequencing T and TaqMan r MGB probes.

Results

The rare -286 A allele, previously shown to be associated with increased CRP expression and plasma levels, was shown to be more frequent in the non-Fulani ethnic groups as compared to the sympatric Fulani ethnic group both in Mali and Sudan. The common -717 T allele was more prevalent in the non-Fulani ethnic group compared to the sympatric Fulani ethnic group, but only in Mali. The parasite prevalence was increased for the -286 A allele, but not for the -717 T allele. No differences regarding genotype frequency or parasite prevalence were seen for +1444 C>T.

Conclusion

This study indicate that CRP may play an important role in the immune responses to malaria, and that the -286 C/T/A CRP polymorphism may be a contributing factor to the lower susceptibility to malaria seen in the Fulani.

The acute phase response in children with mild and severe malaria in Papua New Guinea

The production of acute phase proteins during infection is an important part of innate immunity and limits inflammation. However, little is known of the acute phase response in malaria. We measured acute phase proteins in plasma in children attending clinics and admitted to hospital with acute malaria in Papua New Guinea. Plasma ferritin concentration increased progressively with disease severity with markedly elevated levels in the most severely ill children. Plasma ferritin was >500 ng/ml in 7/99 (7.1%) outpatients with uncomplicated malaria, 22/100 (22.0%) hospital non-severe cases, 64/175 (36.6%) severe malaria cases who survived and 7/9 (77.8%) severe malaria deaths (P<0.001). The greatest concentration of ferritin (3561 ng/ml) was observed in a child who died. By contrast, C-reactive protein concentration was markedly increased in 153 children with uncomplicated malaria [median 203 (interquartile range 51-365) microg/ml] but, surprisingly, was only moderately increased in 135 children with one or more severe manifestations of malaria [47 (17-97) microg/ml; P<0.001] and in 6 children who died [41 (22-280) microg/ml]. Excessive free-radical damage resulting from a combination of iron-induced oxidant stress and reduced levels of C-reactive protein may be an important pathological mechanism in severe malaria and amenable to therapeutic intervention.

Effect of infections and environmental factors on growth and nutritional status in developing countries

Despite numerous advances and improvements in child health globally, malnutrition remains a major problem and underlies a significant proportion of child deaths. A large proportion of the hidden burden of malnutrition is represented by widespread single and multiple micronutrient deficiencies. A number of factors may influence micronutrient deficiencies in developing countries, including poor body stores at birth, dietary deficiencies and high intake of inhibitors of absorption such as phytates and increased losses from the body. Although the effects of poor intake and increased micronutrient demands are well described, the potential effects of acute and chronic infections on the body's micronutrient status are less well appreciated. Even more obscure is the potential effect of immunostimulation and intercurrent infections on the micronutrient distribution and homeostasis. The association therefore of relatively higher rates of micronutrient deficiencies with infectious diseases may be reflective of both increased predisposition to infections in deficient populations as well as a direct effect of the infection itself on micronutrient status indicators. Recently the association of increased micronutrient losses such as those of zinc and copper with acute diarrhea has been recognized and a net negative balance of zinc has been shown in zinc metabolic studies in children with persistent diarrhea. It is also recognized that children with shigellosis can lose a significant amount of vitamin A in the urine, thus further aggravating preexisting subclinical vitamin A deficiency. Given the epidemiological association between micronutrient deficiencies and diarrhea, supplementation strategies in endemic areas are logical. The growing body of evidence on the key role of zinc supplementation in accelerating recovery from diarrheal illnesses in developing countries supports its use in public health strategies.

Plasma zinc concentrations are depressed during the acute phase response in children with falciparum malaria

Plasma concentrations of some micronutrients are altered in the setting of acute infectious or inflammatory stress. Previous studies have provided conflicting evidence concerning the extent and direction of changes in plasma zinc concentrations during the acute phase response. We carried out an observational cohort study in 689 children enrolled in a randomized trial of zinc supplementation during acute falciparum malaria in order to evaluate the relation between plasma zinc concentration and the acute phase response. Plasma zinc was measured by atomic absorption spectrophotometry. On admission, 70% of all subjects had low plasma zinc (<9.2 micromol/L). Multivariate analysis of predictors of admission plasma zinc showed that admission C-reactive protein (CRP), parasite density, and study site were the most important predictors. Predictors of changes in plasma zinc from admission to 72 h included baseline CRP, change in CRP, treatment group, study site, and baseline zinc concentration. In children with acute malaria infection, baseline plasma zinc concentrations were very low and were inversely correlated with CRP (r = -0.24, P < 0.0001) and the degree of parasitemia (r = -0.19, P < 0.0001). Even when CRP and time were taken into account, zinc supplementation increased plasma zinc concentration from admission to 72 h. When available, plasma zinc concentrations should be interpreted with concurrent measures of the acute phase response such as CRP. In children whose age, diet, and/or nutritional status place them at risk of zinc deficiency, those with low plasma zinc levels should be supplemented with oral zinc and followed for clinical and/or biochemical response.

Assessing micronutrient status in the presence of inflammation

Measurement of micronutrient status in the presence of inflammation is difficult for several reasons. Changes in levels of acute phase proteins are associated with increased plasma levels of some indicators of micronutrient status, such as ferritin, and decrease of others, such as retinol. Alterations in the plasma levels of acute phase proteins can occur from hemodilution, sequestration and increased or decreased rates of synthesis and breakdown. How much these relate to functional deficiency is not known. Assays that are less perturbed by inflammation, such as the transferrin receptor assay, and adjustment of plasma micronutrient levels according to different cutoff levels for acute phase proteins are helpful but they do not enable precise assessment of micronutrient status among individuals who are infected. Improving assessment of micronutrient status is important if micronutrient interventions are to be targeted to those with the greatest need.

Haptoglobin genotypes are not associated with resistance to severe malaria in The Gambia

The influence of haptoglobin polymorphisms on severe malaria occurrence was assessed in 1183 individuals from The Gambia. No significant association was found between severe malaria and either haptoglobin genotypes or phenotypes. The advantages of using a deoxyribonucleic acid-based haptoglobin typing method are discussed.

Relation of serum retinol to acute phase proteins and malarial morbidity in Papua New Guinea children

BACKGROUND

Acute phase proteins (APPs) are associated with malaria-induced hyporetinemia (serum retinol <0.70 micromol/L); however, the degree of the association is not well documented.

OBJECTIVE

The association between malaria-induced hyporetinemia and APPs was assessed.

DESIGN

In a cross-sectional study, 90 children with serum retinol concentrations from <0.35 to >1.05 micromol/L were selected from children in a clinical trial of vitamin A supplementation. Serum was collected before treatment allocation. Retinol binding protein (RBP) concentrations were determined by radioimmunoassays, and transthyretin, alpha(1)-acid glycoprotein (AGP), alpha(1)-antichymotrypsin, C-reactive protein (CRP), haptoglobin, and albumin concentrations by radial immunodiffusion assays.

RESULTS

Children in the subsample had high rates of splenomegaly and Plasmodium-positive blood-smear slides (P < 0.01); AGP (Pearson's r = -0.40, P < 0.001) and CRP (r = -0.21, P = 0.04) were inversely correlated with retinol. The negative APPs RBP, transthyretin, and albumin were positively and significantly associated with retinol. All APPs, except alpha(1)-antichymotrypsin, were significantly correlated with splenomegaly. Of the positive APPs, AGP correlated with CRP (r = 0.37, P < 0.001), indicating chronic inflammation. In a stepwise regression analysis, 73% of retinol's variability was explained by RBP and transthyretin. The model predicted that a 1-SD increase in RBP or transthyretin increases retinol by approximately 0.38 or 0.47 micromol/L, respectively, whereas an equivalent increase in AGP decreases retinol by 0.12 micromol/L.

CONCLUSIONS

The RBP-transthyretin transport complex of retinol is not altered by inflammation. Positive APPs are useful markers of type and severity of inflammation; however, except for AGP, it is unlikely that they can correct for malaria-induced hyporetinemia.

Decreased antitoxic activities among children with clinical episodes of malaria

Healthy Gambian children, children with clinical Plasmodium falciparum malaria, and children with asymptomatic P. falciparum infections were studied to investigate whether antitoxic activities may contribute to protection against malarial symptoms. Markers of inflammatory reactions, soluble tumor necrosis factor receptor I, and C-reactive protein were found in high concentrations in children with symptomatic P. falciparum malaria compared with levels in children with asymptomatic P. falciparum infections or in healthy children, indicating that inflammatory reactions are induced only in children with clinical symptoms. Concentrations of soluble tumor necrosis factor receptor I and C-reactive protein were associated with levels of parasitemia. We detected antitoxic activities in sera as measured by their capacity to block toxin-induced Limulus amoebocyte lysate (LAL) activation. Symptomatic children had decreased capacity to block induction of LAL activation by P. falciparum exoantigen. The decreased blocking activity was restored in the following dry season, when the children had no clinical malaria. Symptomatic children also had the highest immunoglobulin G (IgG) reactivities to conserved P. falciparum erythrocyte membrane protein 1 and "Pfalhesin" (band #3) peptides, indicating that such IgG antibodies are stimulated by acute disease but are lost rapidly after the disease episode. Half of the children with symptomatic infections had low levels of haptoglobin, suggesting that these children had chronic P. falciparum infections which may have caused symptoms previously. Only a few of the children with asymptomatic P. falciparum infections had high parasite counts, and antitoxic immunity in the absence of antiparasite immunity appears to be rare among children in this community.

Soluble haemoglobin is a marker of recent Plasmodium falciparum infections

Monoclonal antibodies (Mab) were raised against haemoglobin (Hb) associated with Plasmodium falciparum protein and used to develop an ELISA, measuring circulating levels of released Hb. This assay was evaluated in different malaria patients in parallel with ELISA assays for C-reactive protein (CRP) and haptoglobin. Levels of Hb were negatively associated with levels of haptoglobin. Increased levels of serum Hb and CRP and decreased levels of haptoglobin were seen in Danish malaria patients. Consecutive studies showed that increased Hb levels were detectable 3-7 days after initiation of treatment probably because of drug induced destruction of infected erythrocytes. Increased levels of CRP were measured 0-3 days after initiation of treatment. The Hb assay was used in an epidemiological study of malaria in an area of Sudan with unstable malaria transmission. The proportion of Sudanese adults with detectable soluble Hb was higher in the rainy season with malaria transmission compared to the dry season. Hb levels in the rainy season were negatively associated with levels of haptoglobin. Most adults had increased levels of soluble Hb and decreased levels of haptoglobin 7 and 30 days after their treatment of P. falciparum malaria compared to the levels during acute disease. Thus, both soluble Hb and haptoglobin appear to be markers of recent P. falciparum infections. Very high levels of CRP protein were measured in some of the malaria patients at the day of treatment while lower levels were recorded 7 and 30 days after treatment. Soluble Hb levels were associated with malariometric parameters in a similar fashion to haptoglobin. The new Mab-based assay for measuring soluble Hb in the peripheral blood of malaria patients may be useful for future epidemiological studies of malaria.

MRP 8/14 as marker for Plasmodium falciparum-induced malaria episodes in individuals in a holoendemic area

Presence of Plasmodium falciparum parasites in the peripheral blood of patients in a holoendemic area does not necessarily show that their illness is due to malaria. The aim of the present project was therefore to look for biological markers related to symptomatology or clinical events during a malaria episode. We focused our work on a complex of heterodimeric calcium-binding proteins secreted by stimulated neutrophils and monocytes, named MIF or myeloid-related proteins (MRP 8/14). In a longitudinal study including 51 adults from Ifakara, Tanzania (84.7% prevalence for P. falciparum in adults during the study), the level of MRP 8/14 in the serum was significantly related to the parasite load (Spearman correlation coefficient, 0.52; P < 0.0001). In the serum from children up to 6 years admitted at a health post the MRP 8/14 levels were closely related to parasitemia but also to fever episodes (Spearman correlation coefficients, 0.96 and 0.736; P < 0.0001 and P < 0.001, respectively). Although not specific to malaria, the measurement of MRP 8/14 could be an additional tool in assessing malaria-related morbidity.

C-reactive protein and haptoglobin in the evaluation of a community-based malaria control programme

When cross-sectional surveys are used to evaluate malaria intervention programmes in the community, the prevalence of morbidity is difficult to assess because of the fluctuating nature of malarial fever. We have therefore investigated the impact of bed net usage on 2 surrogate markers of malarial morbidity: (i) elevated C-reactive protein (CRP) (> 8 mg/L) plus detectable parasitaemia, as an indicator of malaria-induced acute-phase response; and (ii) reduced haptoglobin levels (< 180 mg/L), which in this population indicates malaria-induced intravascular haemolysis. Among 1505 Gambian children 1-5 years old, examined on a single occasion at the end of the malarial transmission season, 5% had parasitaemia plus fever, while 24% had parasitaemia plus elevated CRP, and 35% had low haptoglobin. The proportion of children who had parasitaemia plus elevated CRP was significantly lower among those who had slept under insecticide-treated bed nets than among those who did not use a bed net (16% vs. 34%, P < 0.003), and the proportion with low haptoglobin differed similarly (24% vs. 49%, P < 0.003). Use of an untreated bed net had a weaker effect on both indices (22% had parasitaemia plus elevated CRP, 34% had low haptoglobin). CRP and haptoglobin are simple and inexpensive to measure in large numbers of people, and these results suggest that they could be useful for the assessment of malaria intervention programmes.

The epidemiology of malaria in the Wosera area, East Sepik Province, Papua New Guinea, in preparation for vaccine trials. II. Mortality and morbidity

Malaria mortality and morbidity were studied in a rural population of 4000 in the Wosera area, East Sepik Province, Papua New Guinea. Malaria accounted for 4.9% of the 162 deaths investigated by verbal autopsy and for 12.2% of the 49 deaths assessed through medical records. Malaria was the first cause of death in children aged 0.5-4 years. Of the 7795 subjects interviewed and bled during six cross-sectional community-based surveys, children of 1-4 years had the highest malaria-related morbidity. In this age group, point prevalences of fever, fever associated with parasitaemia, and fever plus Plasmodium falciparum (Pf) parasitaemia > or = 10,000 parasites/microliters blood were 5%, 4.1% and 1.5%, respectively. The corresponding figures for adults were 2%, 0.9% and 0.1%, respectively. The calculation of attributable fraction (AF) using a multiple logistic regression model showed that malaria accounted for 0.44 of all fevers in children of 1-4 years and 0.08 of the fevers in adults. Prevalence data derived from the AF estimate were compared with those calculated using different accepted density thresholds. The prevalences which best approximated the results from the logistic regression model were obtained using parasitaemia cut-offs of > or = 1000 Pf parasites/microliter in children aged 1-4 years and adults older than 19 years and of > or = 10,000 parasites/microliter in those aged 5-19 years. Prevalence of fever associated with parasitaemia was highly seasonal, with a peak at the beginning of the wet season. The geographical distribution of malaria morbidity was not uniform. The measurement of malaria-related morbidity, the identification of significant seasonal and local variation as well as the assessment of different methods of defining a clinical episode of Pf malaria are crucial for the design and evaluation of intervention studies, including field trials of antimalarial vaccines.

Immunological markers of childhood fevers in an area of intense and perennial malaria transmission

In order to describe presumed paediatric malaria on a cell-immunological basis, the soluble receptors of IL-2 (sIL-2R) and tumour necrosis factor (sTNF-R55 and sTNF-R75) were quantified in highly exposed young Tanzanian children. Sera were obtained from 66 acute and 72 reported febrile patients during health post consultations and follow-ups and from 68 community controls. Levels of sIL-2R, sTNF-R55 and sTNF-R75 were significantly elevated during fever attacks, especially in very young children. Soluble TNF-R75 levels were most stable and those of sTNF-R55 least. Levels of sTNF-R55 were related to the magnitude of fever and thus appeared to reflect attack severity. Levels of sTNF-R75 were highly significantly associated with parasite density, indicating that this response is malaria-specific. The present study indicates that sTNF-R75 levels could become a useful immunological tool in malaria intervention studies, as they reflect changes in malaria-specific immune responses. Future studies should validate this potential in different endemic settings.

Attributable fraction estimates and case definitions for malaria in endemic areas

Asymptomatic carriage of malaria parasites occurs frequently in endemic areas and the detection of parasites in a blood film from a febrile individual does not necessarily indicate clinical malaria. In areas of low and moderate endemicity the parasite prevalence in fever cases can be compared with that in community controls to estimate the fraction of cases which are attributable to malaria. In areas of very high transmission such estimates of the attributable fraction may be imprecise because very few individuals are without parasites. Furthermore, non-malarial fevers appear to suppress low levels of parasitaemia resulting in biased estimates of the attributable fraction. Alternative estimation techniques were therefore explored using data collected during 1989-1991 from a highly endemic area of Tanzania, where over 80 per cent of young children are parasitaemic. Logistic regression methods which model fever risk as a continuous function of parasite density give more precise estimates than simple analyses of parasite prevalence and overcome problems of bias caused by the effects of non-malarial fevers. Such models can be used to estimate the probability that any individual episode is malaria-attributable and can be extended to allow for covariates. A case definition for symptomatic malaria that is used widely in endemic areas requires fever together with a parasite density above a specific cutoff. The choice of a cutoff value can be assisted by using the probabilities derived from the logistic model to estimate the sensitivity and specificity of the case definition.

Do high levels of C-reactive protein in Tanzanian children indicate malaria morbidity

Children under 6 years of age living in an area of Tanzania highly endemic for malaria were tested for C-reactive protein (CRP) in order to determine how the acute-phase response is related to malaria in children of different ages and to investigate whether serum CRP concentrations might be useful in the qualification of morbidity in such children. The median CRP level in the 629 finger-prick blood samples measured, 6.0 mg/liter, was much higher than that reported in the blood of children in Europe. The CRP concentration was correlated with recent illness reported by the parents. High CRP levels were most strongly associated with Plasmodium falciparum parasitemia in children under 1 year of age. In older children, lower levels of CRP were associated with parasitemia, and fewer children had increased CRP levels attributable to parasitemia. The levels of malaria-attributable CRP appear to track the acquisition of parasitological and clinical tolerance in this area with very high levels of P. falciparum transmission. Determination of CRP levels should be useful in the rapid assessment of the overall burden of morbidity, especially in infants. In areas where malaria is endemic, CRP associated with increased parasite densities provides an objective measure of malaria-specific morbidity. This would be an efficient approach to estimating malaria morbidity risks from small-scale serological surveys.

What is clinical malaria? Finding case definitions for field research in highly endemic areas

In non-endemic areas, the diagnosis of clinical malaria may be made on the basis of fever and a positive blood film. However, in areas of high endemicity, asymptomatic parasitaemia is very common: to assume that a child who presents with fever and parasitaemia is ill from malaria will result in overdiagnosis. In this article, Jo Schellenberg, Tom Smith, Pedro Alonso and Richard Hayes discuss the relationship between fever and parasite density in such areas, and show how the proportion of fevers due to malaria (the attributable fraction) can be estimated and used to evaluate case definitions for use in field trials.