Stronger host response per parasitized erythrocyte in Plasmodium vivax or ovale than in Plasmodium falciparum malaria

Objective and methods Fever tends to start at a lower level of parasitemia in Plasmodium vivax or ovale than in P. falciparum malaria, but hyperparasitemia and complications are more likely to occur in P. falciparum malaria. Therefore, we compared the relationship between parasitemia and host response parameters before therapy in 97 patients with P. faciparum malaria (18 with complications), and 28 with P. vivax or ovale malaria. Results In both types of malaria, parasitemia correlated with blood levels of tumour necrosis factor alpha (TNF‐alpha), lactate dehydrogenase (LDH), Thrombin–antithrombin III (TAT) and elastase, and these parameters were higher in P. falciparum malaria than in P. vivax or ovale malaria. In contrast, the ratios of TNF‐alpha, TAT, elastase, and LDH per parasitized erythrocyte were higher in P. vivax or ovale malaria than in uncomplicated P. falciparum malaria. They were lowest in complicated disease. Multivariate regression analysis confirmed that parasitemia did not affect these differences. Conclusion The host response may reach full strength at lower parasitemia in Plasmodium vivax or ovale, than in P. falciparum malaria. With hyperparasitemia in P. falciparum malaria, the host response seems to be unable to control parasite multiplication.     

Usefulness of clinical algorithm as screening process to detected malaria in low-to-moderate transmission areas of scarce health related resources

Introduction: In areas of low-to-moderate risk of malaria transmission, the World Health Organization recommends parasitic confirmation before treatment. Such areas have usually low budget for health care and malaria diagnosis is mostly based on clinical assumption. Algorithms have been developed to improve health care providers’ identification of clinical malaria and could be used as screening to reduce the number of individuals requiring parasitic confirmation before treating. Methods: Prospective clinical and parasitological data were collected from inhabitants of four villages from March 1984 through March 1985. Symptoms and signs recorded by physicians were used in multivariate models to test the best predictors of malaria. Sensitivity and specificity were calculated for various cut-offs of scores and compared to clinical diagnosis. Results: A total of 8.941 individuals were evaluated during the 1-year period of data collection. The overall prevalence of malaria parasitemia was 19.7% (n = 1762). Of the 4280 people evaluated during the high season period, 24% (n = 1024) presented any parasitemia, 55.3% (566/1024) due to Plasmodium falciparum. The final clinical algorithm included history of fever, rigors, headache, absence of myalgia, backache or cough, nausea or vomiting, and splenomegaly on examination as predictable variables. At a cut-off score of 2.0, the sensitivity of the algorithm was higher for the entire sample (57% vs. 43%), for high season period (70% vs. 53%), for children less than 6 years of age (59% vs. 40%), for individuals with parasitemia due to P. falciparum (65% vs. 48%), and for high P. falciparum parasitemic individuals at high season (84% vs. 68%). However, specificity was usually lower unless a higher cut off was used, in which case the gain in sensitivity by using the algorithm was reduced. Conclusion: In low-to-moderate transmission areas in which health related resources are scarce, a clinical algorithm increases the identification of real cases of malaria and could be used as screening for further parasitic identification.     

Fatal Malaria in a German Couple Returning from Burkina Faso

We report on a German couple found dead at home 7 days after returning from Burkina Faso. Postmortem evaluation revealed Plasmodium falciparum infection with a parasitemia of approximately 80% in both cases. No pathological findings of the organs were present at autopsy except moderate splenomegaly in both cases and myocarditis in one case. Typical findings of fatal malaria like petechial hemorrhages of the brain or other organs, or sequestration of parasitized erythrocytes in venules and capillaries were absent. Lack of sequestration with excessive hyperparasitemia leading to systemic hypoxemia and host cytokine release may have contributed to the rapid fatal course in these nonimmune patients.     

Daily survival and human blood index of major malaria vectors associated with oil palm cultivation in Cameroon and their role in malaria transmission

Objective To describe the daily survival rate, biting habits, feeding behaviour, sporozoite and entomological inoculation rates of Anopheles species and their relative contribution to Plasmodium falciparum transmission in large‐scale oil palm–growing zones in Cameroon. Methods Entomological surveys by employing human‐landing catches, both indoors and outdoors, two nights per month for 12 months from October 2004. Results A total of 2485 Anopheles were collected and four species recorded: An. funestus, An. hancocki, An. gambiae s.s. and An. nili. There was substantial indoors to outdoors variation and seasonality in the distribution of the Anopheles population. All four species showed similar nocturnal biting patterns and were sympatrically involved in malaria transmission simultaneously or replacing each other seasonally. Their constant presence throughout the year and longevity suggest that transmission can occur at any time if parasite reservoirs are present in the area. The circumsporozoite protein rates were 5.8%, 6.3%, 8.4% and 4.1%; mean anthropophilic rates were 97.1%, 94.5%, 73.9% and 77.6%, respectively, for An. funestus, An. gambiae s.l, An. nili and An. hancocki. The annual entomological inoculation rate was 1077 infectious bites per person. Of those An. gambiae specimens testing positive for P. falciparum sporozoites, 69.01% were M form and 30.99% were S form. Conclusion Any vector control strategy intending to significantly reduce the malaria burden in the palm estate will have to take into account entomological heterogeneity in addition to ecological and socio‐economic multiplicity.     

Cytokine profile of Plasmodium falciparum-specific T cells in non-immune malaria patients

CD3⁺ T cells are important sources of both pro‐ and anti‐inflammatory cytokines during Plasmodium falciparum malaria. We studied the frequency of interleukin‐2 (IL‐2), gamma interferon (IFN‐γ), tumour necrosis factor‐alpha (TNF‐α) and IL‐10 expressing CD3⁺ cells in 10 non‐immune malaria patients with uncomplicated malaria and in one patient with cerebral malaria after P. falciparum‐specific and non‐specific mitogenic stimulation. Analysis by fluorescence‐activated cell sorting was performed after drug‐induced clearance of parasites to allow previously sequestered T cells to be detected in peripheral blood. CD3⁺ cells of patients responded to P. falciparum infected erythrocytes with significant increases in the percentage of IL‐2, IFN‐γ, and TNF‐α, but also IL‐10, positive cells. CD3⁺ cells from malaria‐naïve donors were also responsive to specific stimulation albeit to a much lesser extent. Mitogenic stimulation of PBMC revealed no significant differences between cells of patients and controls. CD3⁺ cells of the patient with cerebral malaria were hyporesponsive both to the infecting parasite isolate as well as to our laboratory‐adapted P. falciparum isolate, whereas two patients with uncomplicated disease were more responsive to their infecting parasites than to the laboratory‐adapted isolate. The results indicate that the increased responsiveness of in vivo primed compared to malaria‐naïve CD3⁺ cells is Plasmodium‐specific and biased towards production of IFN‐γ and TNF‐α.     

Plasmodium falciparum,anaemia and cognitive and educational performance among school children in an area of moderate malaria transmission: baseline results of a cluster randomized trial on the coast of Kenya

Objectives Studies have typically investigated health and educational consequences of malaria among school‐aged children in areas of high malaria transmission, but few have investigated these issues in moderate transmission settings. This study investigates the patterns of and risks for Plasmodium falciparum and anaemia and their association with cognitive and education outcomes on the Kenyan coast, an area of moderate malaria transmission. Methods As part of a cluster randomised trial, a baseline cross‐sectional survey assessed the prevalence of and risk factors for P. falciparum infection and anaemia and the associations between health status and measures of cognition and educational achievement. Results are presented for 2400 randomly selected children who were enrolled in the 51 intervention schools. Results The overall prevalence of P. falciparum infection and anaemia was 13.0% and 45.5%, respectively. There was marked heterogeneity in the prevalence of P. falciparum infection by school. In multivariable analysis, being male, younger age, not sleeping under a mosquito net and household crowding were adjusted risk factors for P. falciparum infection, whilst P. falciparum infection, being male and indicators of poor nutritional intake were risk factors for anaemia. No association was observed between either P. falciparum or anaemia and performance on tests of sustained attention, cognition, literacy or numeracy. Conclusion The results indicate that in this moderate malaria transmission setting, P. falciparum is strongly associated with anaemia, but there is no clear association between health status and education. Intervention studies are underway to investigate whether removing the burden of chronic asymptomatic P. falciparum and related anaemia can improve education outcomes.     

Successful oral therapy for severe falciparum malaria: the World Health Organization criteria revisited

We report a successful treatment of severe falciparum malaria in a non-immune adult patient with 30% parasitemia treated with the 6-dose oral regimen of artemether plus lumefantrine combination therapy alone. We have also retrospectively searched our tertiary center's database for similar cases and we have found two additional severe malaria cases, resolved uneventfully with oral regimen. These cases might indicate a need to specifically address the definition of severe and complicated malaria in non-immune patients either in designated guidelines or as an explicit addition to the historical World Health Organization criteria.     

The combination of indoor residual spraying and insecticide-treated nets provides added protection against malaria compared with insecticide-treated nets alone

Both insecticide-treated bed nets (ITNs) and indoor residual spraying (IRS) reduce malaria in high malaria transmission areas. The combined effect of these interventions is unknown. We conducted a non-randomized prospective cohort study to determine protective efficacy of IRS with ITNs (ITN + IRS) compared with ITNs alone (ITN only) in preventing Plasmodium falciparum parasitemia. At baseline, participants provided blood samples for malaria smears, were presumptively treated for malaria, and received ITNs. Blood smears were made monthly and at sick visits. In total, 1,804 participants were enrolled. Incidence of P. falciparum parasitemia in the ITN + IRS and ITN only groups was 18 and 44 infections per 100 persons-years at risk, respectively (unadjusted rate ratio = 0.41; 95% confidence interval [CI] = 0.31-0.56). Adjusted protective efficacy of ITN + IRS compared with ITN only was 62% (95% CI = 0.50-0.72). The combination of IRS and ITN might be a feasible strategy to further reduce malaria transmission in areas of persistent perennial malaria transmission.     

Activated protein C protects vascular endothelial cells from apoptosis in malaria and in sepsis

Objective In malaria and sepsis, apoptotic endothelial damage is preventable in vitro by antioxidants and protease inhibitors. Activated protein C, which has anti‐apoptotic effects, improves survival in sepsis. Therefore, we studied whether activated protein C prevents endothelial cell apoptosis, induced by serum from patients with malaria or sepsis. Methods Endothelial cells were incubated with patient sera (Plasmodium falciparum malaria, Escherichia coli sepsis, Staphylococcus aureus sepsis) or culture supernatants of the respective organisms, with or without neutrophils. Activated protein C was used to reduce endothelial cell apoptosis in vitro. The proportion of apoptotic endothelial cells was determined by TUNEL staining. Results The apoptosis‐inducing effect of patient sera or culture supernatants (P. falciparum, E. coli, S. aureus) on endothelial cells was augmented by neutrophils and reduced by activated protein C in the presence of neutrophils. Pre‐incubating either endothelial cells or neutrophils with activated protein C also reduced the endothelial cell apoptosis rate. The pro‐apoptotic effect of P. falciparum supernatant was reduced by pan‐caspase inhibitor and caspase 8 inhibitor, but not by caspase 9 inhibitor. The pro‐apoptotic effect of E. coli and S. aureus supernatants was also reduced by caspase 9 inhibitor. Conclusions Activated protein C protects vascular endothelial cells from apoptosis triggered by patient sera or culture supernatants in combination with neutrophils. It seems to act both on neutrophils and on endothelial cells. Activated protein C blocks caspase‐8‐dependent apoptosis, which accounts for endothelial damage in sepsis and malaria. Therefore, activated protein C might offer clinical benefit not only in sepsis but also in malaria.     

Apical membrane protein 1‐specific antibody profile and temporal changes in peripheral blood B‐cell populations in Plasmodium vivax malaria

Plasmodium falciparum‐specific antibodies tend to be short‐lived, but their cognate memory B cells (MBCs) circulate in the peripheral blood of exposed subjects for several months or years after the last infection. However, the time course of antigen‐specific antibodies and B‐cell responses to the relatively neglected parasite Plasmodium vivax remains largely unexplored. Here, we showed that uncomplicated vivax malaria elicits short‐lived antibodies but long‐lived MBC responses to a major blood‐stage P vivax antigen, apical membrane protein 1 (PvAMA‐1), in subjects exposed to declining malaria transmission in the Amazon Basin of Brazil. We found that atypical (CD19⁺CD10^?CD21^?CD27^?) MBCs, which appear to share a common precursor with classical MBCs but are unable to differentiate into antibody‐secreting cells, significantly outnumbered classical MBCs by 5:1 in the peripheral blood of adult subjects currently or recently infected with P vivax and by 3:1 in healthy residents in the same endemic communities. We concluded that malaria can drive classical MBCs to differentiate into functionally impaired MBCs not only in subjects repeatedly exposed to P falciparum, but also in subjects living in areas with low levels of P vivax transmission in the Amazon, leading to an impaired B‐cell memory that may affect both naturally acquired and vaccine‐induced immunity.     

Analysis of circulating populations of Plasmodium falciparum in mild and severe malaria in two different epidemiological patterns in Madagascar

Objective To investigate whether the severity of Plasmodium falciparum attack in endemic areas was associated with the multiplicity of infection (MOI) and/or with a particular genotype(s). Method In two areas of different malaria transmission pattern in Madagascar (Sainte‐Marie – mesoendemic and Tsiroanomandidy – hypoendemic) the number and the proportions of msp‐2 genotypes within isolates were determined for each patient using a capillary electrophoresis genotyping method. DNA sequencing was performed to identify the msp‐2 allelic family of dominant clones. Results Eighty six uncomplicated and 33 severe cases were included in Sainte‐Marie and 48 uncomplicated and 69 severe cases were included in Tsiroanomandidy. We found no association between the MOI and severity of malaria as the same mean number of msp‐2 genotypes was found in isolates from uncomplicated and from severe malaria cases (3.72 and 3.73, respectively, P>0.05). The study of the association of dominant clones with clinical status showed no particular genotype or allelic family associated with malaria severity. Conclusions Severity of malaria was not associated with higher MOI in our study. Severity did not appear restricted to some particular genotypes either. On the contrary, severe malaria appeared to be caused by very common genotypes in the studied areas. More comprehensive explorations including immunity and genetic factors of the host are needed to acquire new information about this complex condition.     

Intermittent preventive treatment using artemisinin-based combination therapy reduces malaria morbidity among school-aged children in Mali

Objective  To assess the efficacy of intermittent preventive treatment (IPT) against malaria in school-aged children.
Methods  This was an open randomized controlled trial of seasonal IPT among school children (IPTsc) aged 6–13 years in Kollé, Mali. The study began in September 2007 and completed follow-up in May 2008. Students were randomized to one of three study arms: Sulfadoxine–pyrimethamine plus artesunate (SP/AS), amodiaquine plus artesunate (AQ/AS) or vitamin C. All students received two full treatment doses, given 2 months apart during the season of high transmission from September to December. Groups were compared with respect to incidence of clinical malaria, asymptomatic parasitemia and haemoglobin concentration.
Results  A total of 296 students were randomized, and retention in the study was 99.3%. Clinical malaria incidence in the SP/AS and AQ/AS arms was reduced by 66.6% and 46.5%, respectively, vs . vitamin C ( P  < 0.001). There were fewer clinic visits for any cause among the children receiving SP/AS or AQ/AS ( P  = 0.024). The prevalence of asymptomatic parasitemia was fivefold higher in the vitamin C arm than either SP/AS or AQ/AS at each post-treatment evaluation ( P  < 0.001). At the end of the transmission period, children treated with IPT had lower rates of anaemia (SP/AS, 17.7%; AQ/AS, 16.0%; vitamin C, 29.6%; P  = 0.039).
Conclusion  IPT among school children reduced the rates of clinical malaria, all-cause acute clinic visits, asymptomatic parasitemia and anaemia among school-aged children.     

Clinical case definitions and malaria vaccine efficacy

Reported efficacies from vaccine trials may depend heavily on the clinical case definition used in the trial. The dependence may be particularly striking for diseases such as malaria, in which no single case definition is appropriate. We used logistic regression modeling of the relationship between parasitemia and fever in data sets from Ghanaian children to determine the fraction of fevers attributable to malaria and to model how the choice of a threshold parasitemia in the clinical case definition affects the measured efficacy of malaria vaccines. Calculated clinical attack rates varied 10-fold as a function of the threshold parasitemia. Strikingly, measured vaccine efficacies in reducing clinical malaria depended heavily on the threshold parasitemia, varying between 20% and 80% as the threshold varied between 1 and 5000 parasites/ microL. We suggest that clinical case definitions of malaria that incorporate a threshold parasitemia are arbitrary and do not yield stable estimates of vaccine trial end points.     

Case definitions of clinical malaria under different transmission conditions in Kilifi District, Kenya

BACKGROUND: Clear case definitions of malaria are an essential means of evaluating the effectiveness of present and proposed interventions in malaria. The clinical signs of malaria are nonspecific, and parasitemia accompanied by a fever may not be sufficient to define an episode of clinical malaria in endemic areas. We defined and quantified cases of malaria in people of different age groups from 2 areas with different rates of transmission of malaria. METHODS: A total of 1602 people were followed up weekly for 2 years, and all the cases of fever accompanied by parasitemia were identified. Logistic regression methods were used to derive case definitions of malaria. RESULTS: Two case definitions of malaria were derived: 1 for children 1-14 years old and 1 for infants (<1 year old) and older children and adults (> or =15 years old). We also found a higher number of episodes of clinical malaria per person per year in people from an area of low transmission of malaria, compared with the number of episodes in those from an area of higher transmission (0.84 vs. 0.55 episodes/person/year; incidence rate ratio, 0.66 [95% confidence interval, 0.61-0.72]; P<.001). CONCLUSIONS: Case definitions of malaria are bound to be altered by factors that affect immunity, such as age and transmission. Case definitions may, however, be affected by other immunity-altering factors, such as HIV and vaccination status, and this needs to be borne in mind during vaccine trials.     

Protective effect of amiodarone in malaria

According to previous observations, amiodarone triggers suicidal erythrocyte death or eryptosis, which is characterized by cell shrinkage and exposure of phosphatidylserine at the erythrocyte surface. Eryptosis may in turn accelerate the clearance of Plasmodium-infected erythrocytes. The present study tested whether amiodarone augments phosphatidylserine exposure of Plasmodium-infected erythrocytes, interferes with the development of parasitemia and thus influences the course of malaria. The in vitro infection of human erythrocytes with Plasmodium falciparum (strain BinH) increased annexin V-binding, an effect significantly augmented by amiodarone (10 μM). Amiodarone further significantly decreased intraerythrocytic DNA/RNA content (≥5 μM) and in vitro parasitemia (≥1 μM). Following infection of mice with Plasmodiumberghei ANKA by intraperitoneal injection of parasitized murine erythrocytes (1 × 10⁶) amiodarone (intraperitoneal 50 mg/kg b.w.) significantly decreased the parasitemia and increased the survival of P. berghei-infected mice (from 0% to 70% 26 days after infection). Moreover, treatment with amiodarone significantly increased the percentage of PS-exposing infected erythrocytes. In conclusion, amiodarone inhibits intraerythrocytic growth of P. falciparum, enhances suicidal death of infected erythrocytes, decreases parasitemia following P. berghei infection and supports host survival during malaria.     

Clinical and parasitological characteristics of puerperal malaria

BACKGROUND: Women with semi-immunity to malaria who live in regions where the disease is endemic are at increased risk for more frequent and severe episodes of malaria during pregnancy. Recent findings indicate that this increased risk might persist beyond delivery, but the underlying mechanisms for this change in risk are poorly understood. METHODS: One hundred fifty women were included in a cohort study in Lambaréné, Gabon, and were actively followed up weekly for 10 weeks after delivery, as were nonpregnant control women who had been matched to them by location and age. Parasites in samples of placenta and blood were genotyped by use of polymerase chain reaction amplification of the merozoite surface antigen 2 gene and the subtelomeric variable open reading frame gene of Plasmodium falciparum. RESULTS: Eleven puerperal women had cases of clinical malaria, compared with 1 control woman (rate ratio, 9.8; P=.006). Eighteen puerperal women had P. falciparum parasitemia, compared with 6 control women (rate ratio, 2.7; P=.03). Five of 16 puerperal women (31%) with parasitemia on follow-up had identical parasites in their placentas and blood, and 11 of these cases (69%) were the result of reinfection. Puerperal women remained at equal risk for the development of parasitemia throughout the first 10 weeks after delivery. Use of bed nets, use of chloroquine prophylaxis during pregnancy, presence of malaria episodes during pregnancy, gravidity, and age were not associated with the acquisition of parasitemia during follow-up. CONCLUSIONS: Compared with nonpregnant women, puerperal women have a considerably increased risk for the development of malaria and/or parasitemia. This increased risk is caused both by the recurrence of P. falciparum parasitemia and by the increased susceptibility to new infections, although the latter plays a more significant role.     

Multiple splenic infarcts in acute Plasmodium vivax malaria: A rare case report

In tropical countries like India, malaria has been one of the most common parasitic illnesses leading to frequent hospitalization and causing major economic burden among the masses. Although Plasmodium vivax infection is considered to be benign, in contrast to Plasmodium falciparum infection which is notorious for its severe splenic complications can occur frequently. Splenomegaly tends not to receive special attention, as it is not usually accompanied by any symptoms and can be gradually resolved via standard antimalarial therapy. Splenic infarction, although rarely attributable to malaria in an endemic region with high parasitemia, can be a rare presentation of this disease entity.     

Retrospective analysis of vivax malaria patients presenting to tertiary referral centre of Uttarakhand

Introduction

Despite the high prevalence of Plasmodium vivax (P vivax) malaria, research into its complications has lagged disproportionately as compared to Plasmodium falciparum (P falciparum) malaria.

Material and methods

The present retrospective observational study was conducted on cases with P vivax mono-infection presenting with severe malaria on the basis of one or more criteria as per the World Health Organization guidelines being used for severe falciparum malaria in children, as well as other manifestations been classified as complicated malaria, during an outbreak of malaria in a single tertiary referral hospital of north India.

Results

Seventy-four patients of acute malaria presented during the outbreak, of which 50 cases with P vivax mono-infection were included for the study. Complicated malaria was diagnosed in 41/50 cases, with thrombocytopenia being the commonest manifestation. Other presentations of severe malaria in our patients were liver dysfunction (with or without jaundice) 31/50 cases, respiratory involvement 14/50 cases, renal impairment 11/50 cases, circulatory collapse (Shock) 8/50 cases, severe anaemia 3/50 cases and central nervous system (CNS) involvement 2/50 cases.

Conclusion

The term “benign tertian malaria” no longer holds true for P vivax mono-infection. The authors wish to open a new front for researches on the possible genotypic abnormalities that the parasite or its carrier might have acquired over decades and has transformed into a species with the malignant potential of P falciparum.     

Association of intraleukocytic Plasmodium falciparum malaria pigment with disease severity, clinical manifestations, and prognosis in severe malaria

Peripheral parasite density of Plasmodium falciparum is used as an indicator of malaria disease severity, but does not quantify central sequestration, which is important in the pathogenesis of severe disease. Malaria pigment, recognizable within the cytoplasm of phagocytic cells by light microscopy may represent a peripheral marker for parasite biomass. One hundred seventy-two index cases of severe malaria and 172 healthy age-, residence-, and ethnicity-matched controls with uncomplicated malaria in Bandiagara, Mali were analyzed prospectively for presence of malaria pigment. The presence of polymorphonuclear cell (PMN) and monocyte pigment was strongly associated with severe disease compared with uncomplicated malaria. Total PMN pigment burden in children with severe malaria was higher in those with cerebral manifestations and with combined cerebral manifestations and severe anemia (hemoglobin < or = 5 g/dL) but was not associated with hyperparasitemia (> 500,000 asexual forms/mm3). Additionally, pigmented PMNs/mm3 was associated with a fatal outcome in patients with severe malaria. This study validates the presence of malaria pigment in monocytes and neutrophils as a marker for disease severity, and demonstrates that pigmented neutrophils are associated with cerebral malaria and with death in children with severe malaria.