The indirect health effects of malaria estimated from health advantages of the sickle cell trait

Sickle cell allele HBB-rs334(T) is associated with decreased risk of childhood Burkitt lymphoma in East Africa

Burkitt lymphoma (BL) is an aggressive B-cell lymphoma that significantly contributes to childhood cancer burden in sub-Saharan Africa. Plasmodium falciparum, which causes malaria, is geographically associated with BL, but the evidence remains insufficient for causal inference. Inference could be strengthened by demonstrating that mendelian genes known to protect against malaria-such as the sickle cell trait variant, HBB-rs334(T)-also protect against BL. We investigated this hypothesis among 800 BL cases and 3845 controls in four East African countries using genome-scan data to detect polymorphisms in 22 genes known to affect malaria risk. We fit generalized linear mixed models to estimate odds ratios (OR) and 95% confidence intervals (95% CI), controlling for age, sex, country, and ancestry. The ORs of the loci with BL and P. falciparum infection among controls were correlated (Spearman's ρ = 0.37, p = .039). HBB-rs334(T) was associated with lower P. falciparum infection risk among controls (OR = 0.752, 95% CI 0.628-0.9; p = .00189) and BL risk (OR = 0.687, 95% CI 0.533-0.885; p = .0037). ABO-rs8176703(T) was associated with decreased risk of BL (OR = 0.591, 95% CI 0.379-0.992; p = .00271), but not of P. falciparum infection. Our results increase support for the etiological correlation between P. falciparum and BL risk.

Contribution of malaria and sickle cell disease to anaemia among children aged 6-59 months in Nigeria: a cross-sectional study using data from the 2018 Demographic and Health Survey

OBJECTIVES

To estimate the fraction of anaemia attributable to malaria and sickle cell disease (SCD) among children aged 6-59 months in Nigeria.

DESIGN

Cross-sectional analysis of data from Nigeria's 2018 Demographic and Health Survey (DHS).

SETTING

Nigeria.

PARTICIPANTS

11 536 children aged 6-59 months from randomly selected households were eligible for participation, of whom 11 142 had complete and valid biomarker data required for this analysis. Maternal education data were available from 10 305 of these children.

PRIMARY OUTCOME MEASURE

Haemoglobin concentration.

RESULTS

We found that 70.6% (95% CI: 62.7% to 78.5%) of severe anaemia was attributable to malaria compared with 12.4% (95% CI: 11.1% to 13.7%) of mild-to-severe and 29.6% (95% CI: 29.6% to 31.8%) of moderate-to-severe anaemia and that SCD contributed 0.6% (95% CI: 0.4% to 0.9%), 1.3% (95% CI: 1.0% to 1.7%) and 10.6% (95% CI: 6.7% to 14.9%) mild-to-severe, moderate-to-severe and severe anaemia, respectively. Sickle trait was protective against anaemia and was associated with higher haemoglobin concentration compared with children with normal haemoglobin (HbAA) among malaria-positive but not malaria-negative children.

CONCLUSIONS

This approach used offers a new tool to estimate the contribution of malaria to anaemia in many settings using widely available DHS data. The fraction of anaemia among young children in Nigeria attributable to malaria and SCD is higher at more severe levels of anaemia. Prevention of malaria and SCD and timely treatment of affected individuals would reduce cases of severe anaemia.

Improving the diagnosis of severe malaria in African children using platelet counts and plasma PfHRP2 concentrations

Severe malaria caused by Plasmodium falciparum is difficult to diagnose accurately in children in high-transmission settings. Using data from 2649 pediatric and adult patients enrolled in four studies of severe illness in three countries (Bangladesh, Kenya, and Uganda), we fitted Bayesian latent class models using two diagnostic markers: the platelet count and the plasma concentration of P. falciparum histidine-rich protein 2 (PfHRP2). In severely ill patients with clinical features consistent with severe malaria, the combination of a platelet count of ≤150,000/μl and a plasma PfHRP2 concentration of ≥1000 ng/ml had an estimated sensitivity of 74% and specificity of 93% in identifying severe falciparum malaria. Compared with misdiagnosed children, pediatric patients with true severe malaria had higher parasite densities, lower hematocrits, lower rates of invasive bacterial disease, and a lower prevalence of both sickle cell trait and sickle cell anemia. We estimate that one-third of the children enrolled into clinical studies of severe malaria in high-transmission settings in Africa had another cause of their severe illness.

Confronting Racism in Pain Research: A Call to Action

Racism is an established health determinant across the world. In this 3-part series, we argue that a disregard of how racism manifests in pain research practices perpetuates pain inequities and slows the progression of the field. Our goal in part-1 is to provide a historical and theoretical background of racism as a foundation for understanding how an antiracism pain research framework - which focuses on the impact of racism, rather than "race," on pain outcomes - can be incorporated across the continuum of pain research. We also describe cultural humility as a lifelong self-awareness process critical to ending generalizations and successfully applying antiracism research practices through the pain research continuum. In part-2 of the series, we describe research designs that perpetuate racism and provide reframes. Finally, in part-3, we emphasize the implications of an antiracism framework for research dissemination, community-engagement practices and diversity in research teams. Through this series, we invite the pain research community to share our commitment to the active process of antiracism, which involves both self-examination and re-evaluation of research practices shifting our collective work towards eliminating racialized injustices in our approach to pain research. PERSPECTIVE: We call on the pain community to dismantle racism in our research practices. As the first paper of the 3-part series, we introduce dimensions of racism and its effect on pain inequities. We also describe the imperative role of cultural humility in adopting antiracism pain research practices.

Phthalimide analogs for antimalarial drug discovery

Malaria remains one of the world's most life-threatening diseases and, thus, it is a major public health concern all around the world. The disease can become devastating if not treated with proper medication in a timely manner. Currently, the number of viable treatment therapies is in continuous decline due to compromised effectiveness, probably owing to the complex life cycle of Plasmodium falciparum. The factors responsible for the unclear status of malaria eradication programmes include ever-developing parasite resistance to the most effective treatments used on the frontline (i.e., artemisinin derivatives) and the paucity of new effective therapeutics. Due to these circumstances, the development of novel effective drug candidates with unique modes of action is essential for overcoming the listed obstacles. As such, the discovery of novel chemical compounds based on validated pharmacophores remains an unmet need in the field of medicinal chemistry. In this area, functionalized phthalimide (Pht) analogs have been explored as potential candidates against various diseases, including malaria. Pht presents a promising bioactive scaffold that can be easily functionalized and thus utilized as a starting point for the development of new antimalarial candidates suitable for preclinical and clinical studies. In this short review, we highlight a wide range of Pht analogs that have been investigated for their activity against various strains of Plasmodium falciparum.

Incidence and predictors of hospital readmission in children presenting with severe anaemia in Uganda and Malawi: a secondary analysis of TRACT trial data

BACKGROUND

Severe anaemia (haemoglobin < 6 g/dL) is a leading cause of recurrent hospitalisation in African children. We investigated predictors of readmission in children hospitalised with severe anaemia in the TRACT trial (ISRCTN84086586) in order to identify potential future interventions.

METHODS

Secondary analyses of the trial examined 3894 children from Uganda and Malawi surviving a hospital episode of severe anaemia. Predictors of all-cause readmission within 180 days of discharge were identified using multivariable regression with death as a competing risk. Groups of children with similar characteristics were identified using hierarchical clustering.

RESULTS

Of the 3894 survivors 682 (18%) were readmitted; 403 (10%) had ≥2 re-admissions over 180 days. Three main causes of readmission were identified: severe anaemia (n = 456), malaria (n = 252) and haemoglobinuria/dark urine syndrome (n = 165). Overall, factors increasing risk of readmission included HIV-infection (hazard ratio 2.48 (95% CI 1.63-3.78), p < 0.001); ≥2 hospital admissions in the preceding 12 months (1.44(1.19-1.74), p < 0.001); history of transfusion (1.48(1.13-1.93), p = 0.005); and missing ≥1 trial medication dose (proxy for care quality) (1.43 (1.21-1.69), p < 0.001). Children with uncomplicated severe anaemia (Hb 4-6 g/dL and no severity features), who never received a transfusion (per trial protocol) during the initial admission had a substantially lower risk of readmission (0.67(0.47-0.96), p = 0.04). Malaria (among children with no prior history of transfusion) (0.60(0.47-0.76), p < 0.001); younger-age (1.07 (1.03-1.10) per 1 year younger, p < 0.001) and known sickle cell disease (0.62(0.46-0.82), p = 0.001) also decreased risk of readmission. For anaemia re-admissions, gross splenomegaly and enlarged spleen increased risk by 1.73(1.23-2.44) and 1.46(1.18-1.82) respectively compared to no splenomegaly. Clustering identified four groups of children with readmission rates from 14 to 20%. The cluster with the highest readmission rate was characterised by very low haemoglobin (mean 3.6 g/dL). Sickle Cell Disease (SCD) predominated in two clusters associated with chronic repeated admissions or severe, acute presentations in largely undiagnosed SCD. The final cluster had high rates of malaria (78%), severity signs and very low platelet count, consistent with acute severe malaria.

CONCLUSIONS

Younger age, HIV infection and history of previous hospital admissions predicted increased risk of readmission. However, no obvious clinical factors for intervention were identified. As missing medication doses was highly predictive, attention to care related factors may be important.

TRIAL REGISTRATION

ISRCTN ISRCTN84086586 .

Improving statistical power in severe malaria genetic association studies by augmenting phenotypic precision

Severe falciparum malaria has substantially affected human evolution. Genetic association studies of patients with clinically defined severe malaria and matched population controls have helped characterise human genetic susceptibility to severe malaria, but phenotypic imprecision compromises discovered associations. In areas of high malaria transmission, the diagnosis of severe malaria in young children and, in particular, the distinction from bacterial sepsis are imprecise. We developed a probabilistic diagnostic model of severe malaria using platelet and white count data. Under this model, we re-analysed clinical and genetic data from 2220 Kenyan children with clinically defined severe malaria and 3940 population controls, adjusting for phenotype mis-labelling. Our model, validated by the distribution of sickle trait, estimated that approximately one-third of cases did not have severe malaria. We propose a data-tilting approach for case-control studies with phenotype mis-labelling and show that this reduces false discovery rates and improves statistical power in genome-wide association studies.

Malaria is a cause of iron deficiency in African children

Malaria and iron deficiency (ID) are common and interrelated public health problems in African children. Observational data suggest that interrupting malaria transmission reduces the prevalence of ID1. To test the hypothesis that malaria might cause ID, we used sickle cell trait (HbAS, rs334 ), a genetic variant that confers specific protection against malaria2, as an instrumental variable in Mendelian randomization analyses. HbAS was associated with a 30% reduction in ID among children living in malaria-endemic countries in Africa (n = 7,453), but not among individuals living in malaria-free areas (n = 3,818). Genetically predicted malaria risk was associated with an odds ratio of 2.65 for ID per unit increase in the log incidence rate of malaria. This suggests that an intervention that halves the risk of malaria episodes would reduce the prevalence of ID in African children by 49%.

Glucose-6-phosphate dehydrogenase deficiency and susceptibility to childhood diseases in Kilifi, Kenya

Few previous studies have reported the effects of glucose-6-phosphate dehydrogenase (G6PD)-deficiency on child health in Africa. We conducted a case-control study in which cases (n = 6829) were children admitted, for any reason, to Kilifi County Hospital, Kenya, while controls (n = 10 179) were recruited from the surrounding community. Cases were subclassified based on their clinical and laboratory findings at admission. We calculated the prevalence of specific diseases by G6PD c.202 genotype, the only significant cause of G6PD-deficiency in this area, then estimated the association between genotype and admission with specific conditions using logistic regression.  Among neonates, the prevalence of jaundice was higher in both G6PD c.202T heterozygotes (40/88; 45.5%; P = .004) and homo/hemizygotes (81/134; 60.5%; P < .0001) than in wild-type homozygotes (157/526; 29.9%). Median bilirubin levels also increased across the groups, being highest (239 mmol/L; interquartile range 96-390 mmol/L) in G6PD c.202T homo/hemizygotes. No differences were seen in admission hemoglobin concentrations or the prevalence of anemia or severe anemia by G6PD c.202 genotype. On case control analysis, G6PD heterozygosity was negatively associated with all-cause hospital admission (odds ratio 0.81; 95% confidence interval 0.73-0.90; P < .0001) and, specifically, admission with either pneumonia or Plasmodium falciparum parasitemia; while, conversely, it was positively associated with Gram-positive bacteremia. G6PD c.202T homo/heterozygosity was positively associated with neonatal jaundice, severe pneumonia, the receipt of a transfusion, and in-patient death. Our study supports the conclusion that G6PD c.202T is a balanced polymorphism in which a selective advantage afforded to heterozygous females against malaria is counterbalanced by increased risks of neonatal jaundice, invasive bacterial infections, and anemia.

Risk of pneumococcal bacteremia in Kenyan children with glucose-6-phosphate dehydrogenase deficiency

BACKGROUND

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common enzyme deficiency state in humans. The clinical phenotype is variable and includes asymptomatic individuals, episodic hemolysis induced by oxidative stress, and chronic hemolysis. G6PD deficiency is common in malaria-endemic regions, an observation hypothesized to be due to balancing selection at the G6PD locus driven by malaria. G6PD deficiency increases risk of severe malarial anemia, a key determinant of invasive bacterial disease in malaria-endemic settings. The pneumococcus is a leading cause of invasive bacterial infection and death in African children. The effect of G6PD deficiency on risk of pneumococcal disease is undefined. We hypothesized that G6PD deficiency increases pneumococcal disease risk and that this effect is dependent upon malaria.

METHODS

We performed a genetic case-control study of pneumococcal bacteremia in Kenyan children stratified across a period of falling malaria transmission between 1998 and 2010.

RESULTS

Four hundred twenty-nine Kenyan children with pneumococcal bacteremia and 2677 control children were included in the study. Among control children, G6PD deficiency, secondary to the rs1050828 G>A mutation, was common, with 11.2% (n = 301 of 2677) being hemi- or homozygotes and 33.3% (n = 442 of 1329) of girls being heterozygotes. We found that G6PD deficiency increased the risk of pneumococcal bacteremia, but only during a period of high malaria transmission (P = 0.014; OR 2.33, 95% CI 1.19-4.57). We estimate that the population attributable fraction of G6PD deficiency on risk of pneumococcal bacteremia in areas under high malaria transmission is 0.129.

CONCLUSIONS

Our data demonstrate that G6PD deficiency increases risk of pneumococcal bacteremia in a manner dependent on malaria. At the population level, the impact of G6PD deficiency on invasive pneumococcal disease risk in malaria-endemic regions is substantial. Our study highlights the infection-associated morbidity and mortality conferred by G6PD deficiency in malaria-endemic settings and adds to our understanding of the potential indirect health benefits of improved malaria control.

A common polymorphism in the mechanosensitive ion channel PIEZO1 is associated with protection from severe malaria in humans

Malaria caused by the apicomplexan parasite Plasmodium falciparum has served as a strong evolutionary force throughout human history, selecting for red blood cell polymorphisms that confer innate protection against severe disease. Recently, gain-of-function mutations in the mechanosensitive ion channel PIEZO1 were shown to ameliorate Plasmodium parasite growth, blood-brain barrier dysfunction, and mortality in a mouse model of malaria. In humans, the gain-of-function allele PIEZO1 E756del is highly prevalent and enriched in Africans, raising the possibility that it is under positive selection due to malaria. Here we used a case-control study design to test for an association between PIEZO1 E756del and malaria severity among children in Gabon. We found that the E756del variant is strongly associated with protection against severe malaria in heterozygotes. In subjects with sickle cell trait, heterozygosity for PIEZO1 E756del did not confer additive protection and homozygosity was associated with an elevated risk of severe disease, suggesting an epistatic relationship between hemoglobin S and PIEZO1 E756del. Using donor blood samples, we show that red cells heterozygous for PIEZO1 E756del are not dehydrated and can support the intracellular growth of P. falciparum similar to wild-type cells. However, surface expression of the P. falciparum virulence protein PfEMP-1 was significantly reduced in infected cells heterozygous for PIEZO1 756del, a phenomenon that has been observed with other protective polymorphisms, such as hemoglobin C. Our findings demonstrate that PIEZO1 is an important innate determinant of malaria susceptibility in humans and suggest that the mechanism of protection may be related to impaired export of P. falciparum virulence proteins.

Outcome of pregnancies among women with sickle cell disease

Purpose: To evaluate the outcome of pregnancies among women affected by sickle cell disease (SCD).Material and methods: This retrospective comparative cohort study was carried out between 1 January 2014 and 31 December 2018. The files of pregnant women with and without SCD were analyzed. The main variables recorded included parity, diseases that occurred during pregnancy, maternal and gestational ages at delivery, mode of delivery, birthweight and Apgar score. Data were analyzed using SPSS 21.0. Fisher exact test and the t-test was used for comparison. p < .05 was considered statistically significant.Results: Our frequency of delivery of women with SCD was 0.1% (35/34,895). Significant complications associated with SCD were maternal anemia (RR = 17.00, 95%CI = 5.35-53.99), intra-uterine fetal demise (RR = 12.00, 95%CI = 1.39-103.22), low birthweight (RR = 2.52, 95%CI = 1.50-4.25), neonatal asphyxia (RR = 7.70, 95%CI = 2.57-22.99), transfer of newborn to the neonatal intensive care unit (RR = 3.42, 95%CI = 1.94-6.03), early neonatal death (RR = 4.56, 95%CI = 1.09-19.10), and maternal postpartum severe anemia (RR = 4.50, 95%CI = 1.36-14.87).Conclusions: Pregnancies amongst women with SCD are still associated with increased risk of maternal anemia as well as perinatal morbidity and mortality despite frequent blood transfusion. Therefore, new strategies should be explored to improve such pregnancies.

Life-Threatening Infectious Complications in Sickle Cell Disease: A Concise Narrative Review

Sickle cell disease (SCD) results in chronic hemolytic anemia, recurrent vascular occlusion, insidious vital organ deterioration, early mortality, and diminished quality of life. Life-threatening acute physiologic crises may occur on a background of progressive diminishing vital organ function. Sickle hemoglobin polymerizes in the deoxygenated state, resulting in erythrocyte membrane deformation, vascular occlusion, and hemolysis. Vascular occlusion and increased blood viscosity results in functional asplenia and immune deficiency in early childhood, resulting in life-long increased susceptibility to serious bacterial infections. Infection remains a main cause of overall mortality in patients with SCD in low- and middle-income countries due to increased exposure to pathogens, increased co-morbidities such as malnutrition, lower vaccination rates, and diminished access to definitive care, including antibiotics and blood. Thus, the greatest gains in preventing infection-associated mortality can be achieved by addressing these factors for SCD patients in austere environments. In contrast, in high-income countries, perinatal diagnosis of SCD, antimicrobial prophylaxis, vaccination, aggressive use of antibiotics for febrile episodes, and the availability of contemporary critical care resources have resulted in a significant reduction in deaths from infection; however, chronic organ injury is problematic. All clinicians, regardless of their discipline, who assume the care of SCD patients must understand the importance of infectious disease as a contributor to death and disability. In this concise narrative review, we summarize the data that describes the importance of infectious diseases as a contributor to death and disability in SCD and discuss pathophysiology, prevalent organisms, prevention, management of acute episodes of critical illness, and ongoing care.

5-(Hydroxymethyl)furfural restores low-oxygen rheology of sickle trait blood in vitro

Sickle cell trait (SCT) is the benign heterozygous carrier state for the sickle variant of the HBB gene. Most of the ~300 million people with SCT worldwide will not experience any significant complications. However, accumulating evidence finds SCT associated with increased risk for the common conditions of chronic kidney disease and venous thromboembolism, and severe but rare renal medullary carcinoma and exercise-induced rhabdomyolysis. The mechanism is uncertain, but probably involves pathological rheology of SCT blood in regions of low oxygen tension, resulting from sickle haemoglobin polymerization in SCT red cells and leading to reduced blood flow and further tissue hypoxia and damage. Here, we used an in vitro microfluidic flow system to study the oxygen-dependent rheology of SCT blood and show that 5-(hydroxymethyl)furfural, a natural breakdown product of glucose and fructose-containing foods, such as fruit juices, can reduce the effects of hypoxia on SCT blood rheology in vitro, restoring near-normal flow velocities at very low oxygen. While opinions regarding the clinical significance of the risks associated with SCT are still evolving, these results suggest that a compound present in some food may provide a potential approach for managing risks that may be associated with SCT.

The epidemiology of sickle cell disease in children recruited in infancy in Kilifi, Kenya: a prospective cohort study

BACKGROUND

Sickle cell disease is the most common severe monogenic disorder in humans. In Africa, 50-90% of children born with sickle cell disease die before they reach their fifth birthday. In this study, we aimed to describe the comparative incidence of specific clinical outcomes among children aged between birth and 5 years with and without sickle cell disease, who were resident within the Kilifi area of Kenya.

METHODS

This prospective cohort study was done on members of the Kilifi Genetic Birth Cohort Study (KGBCS) on the Indian Ocean coast of Kenya. Recruitment to the study was facilitated through the Kilifi Health and Demographic Surveillance System (KHDSS), which covers a resident population of 260 000 people, and was undertaken between Jan 1, 2006, and April 30, 2011. All children who were born within the KHDSS area and who were aged 3-12 months during the recruitment period were eligible for inclusion. Participants were tested for sickle cell disease and followed up for survival status and disease-specific admission to Kilifi County Hospital by passive surveillance until their fifth birthday. Children with sickle cell disease were offered confirmatory testing and care at a dedicated outpatient clinic.

FINDINGS

15 737 infants were recruited successfully to the KGBCS, and 128 (0·8%) of these infants had sickle cell disease, of whom 70 (54·7%) enrolled at the outpatient clinic within 12 months of recruitment. Mortality was higher in children with sickle cell disease (58 per 1000 person-years of observation, 95% CI 40-86) than in those without sickle cell disease (2·4 per 1000 person-years of observation, 2·0-2·8; adjusted incidence rate ratio [IRR] 23·1, 95% CI 15·1-35·3). Among children with sickle cell disease, mortality was lower in those who enrolled at the clinic (adjusted IRR 0·26, 95% CI 0·11-0·62) and in those with higher levels of haemoglobin F (HbF; adjusted IRR 0·40, 0·17-0·94). The incidence of admission to hospital was also higher in children with sickle cell disease than in children without sickle cell disease (210 per 1000 person-years of observation, 95% CI 174-253, vs 43 per 1000 person-years of observation, 42-45; adjusted IRR 4·80, 95% CI 3·84-6·15). The most common reason for admission to hospital among those with sickle cell disease was severe anaemia (incidence 48 per 1000 person-years of observation, 95% CI 32-71). Admission to hospital was lower in those with a recruitment HbF level above the median (IRR 0·43, 95% CI 0·24-0·78; p=0·005) and those who were homozygous for α-thalassaemia (0·07, 0·01-0·83; p=0·035).

INTERPRETATION

Although morbidity and mortality were high in young children with sickle cell disease in this Kenyan cohort, both were reduced by early diagnosis and supportive care. The emphasis must now move towards early detection and prevention of long-term complications of sickle cell disease.

FUNDING

Wellcome Trust.

Dehydrated hereditary stomatocytosis: clinical perspectives

Dehydrated hereditary stomatocytosis (DHSt) is a nonimmune congenital hemolytic disorder characterized by red blood cell (RBC) dehydration and lysis. It has been a recognized diagnostic entity for almost 50 years, and autosomal dominant inheritance has long been suspected, but it was not until 2011 that the first genetic alterations were identified. The current study reviews 73 articles published during 1971–2019 and focuses on clinical perspectives of the disease. All but one of the published clinical data in DHSt were either single case reports or case series. From these, it can be seen that patients with DHSt often have fully or partially compensated hemolysis with few symptoms. Despite this, iron overload is an almost universal finding even in patients without or with only sporadic blood transfusions, and this may lead to organ dysfunction. Other severe complications, such as thrombosis and perinatal fluid effusions unrelated to fetal hemoglobin concentration, may also occur. No specific treatment for symptomatic hemolysis exists, and splenectomy should be avoided as it seems to aggravate the risk of thrombosis. Recently, treatment with senicapoc has shown activity against RBC dehydration in vitro; however, it is not known if this translates into relevant clinical effects. In conclusion, despite recent advances in the understanding of pathophysiology in DHSt, options for clinical management have not improved. Entering data into international registries has the potential to fill gaps in knowledge and eventually care of these rare patients.