Sickle cell trait, malaria and anaemia in pregnant Zambian women

In a sample of 424 pregnant Zambian women a series of tests was carried out: sickle cell test, haemoglobin estimation and screening of a thick blood smear for malarial parasites. More anaemia was found in the primigravidae than in the multigravidae. The haemoglobin level was found to be lower with primigravidity and, independently of this gravidity effect, also with malaria. Taking into account the higher malaria frequency in primigravidae, this group must be considered as a high risk group for development of anaemia. There was no significant interaction between sickle cell trait, anaemia and malaria. In addition to the tests during pregnancy, the placentae and umbilical cords of 155 women were screened for malaria as were the mothers just before delivery. More malaria parasites were detected in the placentae of the primiparous than in those of multiparous women. Peripheral parasitaemia was strikingly less prevalent than infestation of the placenta.     

Sickle hemoglobin (HbS) allele and sickle cell disease: a HuGE review

Sickle cell disease is caused by a variant of the beta-globin gene called sickle hemoglobin (Hb S). Inherited autosomal recessively, either two copies of Hb S or one copy of Hb S plus another beta-globin variant (such as Hb C) are required for disease expression. Hb S carriers are protected from malaria infection, and this protection probably led to the high frequency of Hb S in individuals of African and Mediterranean ancestry. Despite this advantage, individuals with sickle cell disease exhibit significant morbidity and mortality. Symptoms include chronic anemia, acute chest syndrome, stroke, splenic and renal dysfunction, pain crises, and susceptibility to bacterial infections. Pediatric mortality is primarily due to bacterial infection and stroke. In adults, specific causes of mortality are more varied, but individuals with more symptomatic disease may exhibit early mortality. Disease expression is variable and is modified by several factors, the most influential being genotype. Other factors include beta-globin cluster haplotypes, alpha-globin gene number, and fetal hemoglobin expression. In recent years, newborn screening, better medical care, parent education, and penicillin prophylaxis have successfully reduced morbidity and mortality due to Hb S.     

The emergence and maintenance of sickle cell hotspots in the Mediterranean

Genetic disorders of haemoglobin (haemoglobinopathies), including the thalassaemias and sickle cell anaemia, abound in historically malarious regions, due to the protection they provide against death from severe malaria. Despite the overall spatial correlation between malaria and these disorders, inter-population differences exist in the precise combinations of haemoglobinopathies observed. Greece and Italy present a particularly interesting case study: their high frequencies of beta thalassaemia speak to a history of intense malaria selection, yet they possess very little of the strongly malaria protective mutation responsible for sickle cell anaemia, despite historical migrational links with Africa where high frequencies of sickle cell occur. Twentieth century surveys of beta thalassaemia and sickle cell in Greece, Sicily and Sardinia have revealed striking sickle cell ‘hotspots’ – places where the frequency of sickle cell approaches that seen in Africa while neighbouring populations remain relatively sickle cell free. It remains unclear how these hotspots have been maintained over time without sickle cell spreading throughout the region. Here we use a metapopulation model to show that (i) epistasis between the alpha and beta forms of thalassaemia can restrict the spread of sickle cell through a network of linked subpopulations and (ii) the emergence of sickle cell hotspots requires relatively low levels of gene flow, but the aforementioned epistasis increases the chances of hotspots forming.     

Anaemia in pregnant Ghanaian women: importance of malaria, iron deficiency, and haemoglobinopathies

In sub-Saharan Africa, anaemia in pregnancy results from multiple causes including malaria, iron deficiency and haemoglobinopathies. In a cross-sectional study among 530 pregnant women in Ghana in November-December 1998, red blood cell indices were analysed with respect to malaria, serum concentrations of ferritin and C-reactive protein (CRP), and the haemoglobin and alpha-globin genotypes. Anaemia (haemoglobin [Hb] < 11 g/dL) was found in 54% of the women; 63% harboured malaria parasites at predominantly low numbers. Ferritin levels were considerably influenced by malaria and inflammatory processes (CRP > 0.6 mg/dL). Depending on the definition applied, the prevalence of iron deficiency ranged between 5% and 46%. The HbAS trait was observed in 14%, HbAC and elevated HbF in 7% each, and sickle cell disease in 1%. Heterozygous beta-thalassaemia was present in 1% of the women and alpha(+)-thalassaemia in 33% (29% heterozygous, 4% homozygous). Women with HbAS had higher malaria parasite densities than those with HbAA. In individuals with highly elevated HbF (> 10%), parasitaemia occurred in 27% only. Low gravidity, second trimester of pregnancy, malaria, raised CRP levels, and homozygous alpha(+)-thalassaemia were independent risk factors for anaemia in multivariate analysis. alpha(+)-Thalassaemia, however, was associated with a lesser degree of malarial anaemia when compared to non-thalassaemic women. Iron deficiency appears not to be a major health problem in this population. Haemoglobinopathies are common but, except for homozygous alpha(+)-thalassaemia, do not substantially contribute to anaemia in pregnancy. alpha(+)-Thalassaemia ameliorates malarial anaemia in pregnant women.     

Observations on the resistance in Hb E thalassaemia disease to induced infection with Plasmodium vivax

Subjects with sickle cell trait have been known to offer resistance to induced Plasmodium falciparum infection. The resistance to malarial infection in other haemoglobinopathic disorders is not clearly known. Investigations were undertaken to test for resistance to malaria in Hb E thalassaemia disease. Compared to controls, subjects with Hb E thalassaemia disease were found to have significant resistance to induced Plasmodium vivax infection.     

Sickle cell anaemia: haemorheological aspects

The maintenance of erythrocyte shape and membrane integrity is bound to the modification of deformability and/or permeability. Usually, this features are not investigated with normal laboratory tests. The membrane stiffness, the cell geometry, and the viscoelasticity components are influencing factors on survival and functionality of the erythrocytes. Only few studies have analyzed the viscoelastic characteristics of red blood cells, even less are the studies on patients affected by sickle cell disease (SCD), a pathology characterized by acute and chronic impairment of cell flexibility due to the formation of intracellular sickle haemoglobin (Hb S) polymers. A critical point of SCD is represented by the rheologic alterations of sickle cells determined by the transition from sol to gel of haemoglobin producing a dramatic change in cell viscosity and viscoelastic properties. We have investigated the behaviour of the blood in SCD, from an original rheological point of view, by evaluating the viscoelastic properties of sickle cells in oscillating harmonic sinusoidal mode. A comparison between patients with different severity of the disease, with transfusion dependence (TD) or without transfusion dependence (NTD), has been carried out. This study has confirmed the rheologic impairment of SC blood. The TD patients showed a minor heterogeneneity of rheologic behaviour in comparison with NTD patients, because of the normalizing effect of transfusion. The analysis of viscoelastic properties might be an additional useful tool for monitoring transfusional and pharmacological treatments.     

The impact of malarial infection and diet on the anaemia status of rural pregnant Malawian women

OBJECTIVE: To investigate haematological and biochemical iron indices in relation to malaria, gravida, and dietary iron status in rural pregnant Malawian women. DESIGN: In this self-selected sample, haemoglobin, haematocrit, red cell indices, serum ferritin, serum iron, serum transferrin, and serum transferrin receptor (TfR) were measured. Infection was assessed by a malaria slide, serum C-reactive protein, and white blood cell count. Dietary iron variables were measured by three 24-h interactive recalls. SETTING AND SUBJECTS: 152 rural pregnant women recruited at 24 weeks gestation while attending a rural antenatal clinic in Southern Malawi; 36% were primagravid; 43% were gravida 2-4; 26% were gravida >5. RESULTS: Of the women, 69% (n=105) were anaemic (haemoglobin <110 g/l); 37% (n=39) had anaemia and malarial parasitaemia on the test day; 17% (n=26) with malaria were also classified with iron deficiency (ID) anaemia (based on serum ferritin < or = 50 microg/l and Hb <110 g/l) while an additional seven with malaria were classified with ID without anaemia. In malarial-free subjects, 32% were classified with IDA (serum ferritin <12 microg/l and Hb <110 g/l) and 17% with ID (serum ferritin <12 microg/l; Hb > or = 110 g/l). Serum TfR concentrations were elevated in anaemic women (P<0.01). In non-malarial parasitaemic subjects, serum TfR correlated negatively with haemoglobin (r=-0.313; P<0.001) but not serum ferritin. Of the women, 49% were at risk for inadequate iron intakes. Most dietary iron was non-haem; plant foods provided 89%; flesh foods (mainly fish) only 9%. Malarial parasitaemia and intakes of available iron impacted significantly on iron status. CONCLUSION: Anaemia prevalence from all causes was high (that is, 69%); three factors were implicated: malaria, and deficiencies of iron and possibly folate, induced partly by an inadequate dietary supply and/or secondary to malarial parasitaemia. Sponsorship: International Development Research Centre (IDRC) of Canada. Opportunities for Micronutrient Interventions (OMNI) Project. Natural Sciences and Engineering Research Council of Canada.     

Complement binding to erythrocytes is associated with macrophage activation and reduced haemoglobin in Plasmodium falciparum malaria.

We have examined IgG and complement factor C3d deposition on erythrocytes by means of the direct Coombs' test (DAT) and looked for an association with the anaemia seen in falciparum malaria in children living in an area of hyperendemic malaria transmission (in Ghana). In one study (in 1997), 53 out of 199 patients had a positive DAT. Of these, 45 samples reacted with anti-C3d antibodies, 2 with anti-IgG and 6 with both reagents. There were significantly lower haemoglobin (Hb)-levels and higher prevalence of spleen enlargement in DAT-positive than in DAT-negative patients. Hb-levels were independently associated with DAT and age. This initial study was designed to investigate the role of intravascular haemolysis (IVH), but we found no association between IVH and either DAT result or anaemia. Because of the risk of selection bias we repeated the study using consecutive enrollment of malaria patients and were able to confirm the results in a total of 49 DAT-positive and 183 DAT-negative patients. This second study (in 1998) was designed to look at the importance of erythrophagocytosis through measurement of plasma neopterin levels and total nitrite and nitrate as markers of NO-release. Both parameters were significantly higher in DAT-positive than in DAT-negative patients (P < 0.001), indicating that complement binding to erythrocytes was associated with macrophage activation. Plasma levels of haptoglobin, interleukin-10 and tumour necrosis factor-alpha did not vary between the groups. The studies support the role of complement activation and erythrophagocytosis in the pathogenesis of anaemia in falciparum malaria in African children.     

Malaria and hookworm infections in relation to haemoglobin and serum ferritin levels in pregnancy in Masindi district, western Uganda

This study examined the predictors of haemoglobin (Hb) concentration and serum ferritin (SF) levels in pregnant women in an area of stable malaria transmission and high prevalence of intestinal helminth infections. In total, 834 women attending antenatal care for the first time were examined. Blood slides for malaria parasites were prepared for 802, of which 154 were primigravidae (PG) and 648 were multigravidae (MG). Malaria parasitaemia rate was 42.6% (66) in PG and 33.3% (216) in MG (P=0.04). The geometric mean parasite density was 1695.8 (95% CI 1005.0-2386.5) in PG and 922.7 (95% CI 626.7-1382.6) in MG (P=0.02). Anaemia (Hb<100g/l) was found in 18.0% (94) of aparasitaemic women compared to 28.5% (80) among parasitaemic women (P<0.001). The prevalence of anaemia was 15.1% (42) in women without hookworm infection compared to 23.3% (129) among infected women (P=0.006). Malaria parasitaemia, hookworm infection, C-reactive protein, gravidity and gestational age were associated with Hb status. Malaria parasitaemia, Ascaris lumbricodes and Trichuris trichiura infections and age were associated with SF. Malaria, hookworm infections and iron deficiency were associated with anaemia in the study population.     

Anaemia during pregnancy in Burkina Faso, west Africa, 1995-96: prevalence and associated factors. DITRAME Study Group

We report the results of a cross-sectional study carried out in 1995-96 on anaemia in pregnant women who were attending two antenatal clinics in Bobo-Dioulasso, Burkina Faso, as part of a research programme including a clinical trial of zidovudine (ZDV) in pregnancy (ANRS 049 Clinical Trial). For women infected with human immunodeficiency virus (HIV) in Africa, anaemia is of particular concern when considering the use of ZDV to decrease mother-to-child transmission of HIV. The objectives were to determine the prevalence of and risk factors for maternal anaemia in the study population, and the effect of HIV infection on the severity of maternal anaemia. HIV counselling and testing were offered to all women, and haemograms were determined for those women who consented to serological testing. Haemoglobin (Hb) levels were available for 2308 of the 2667 women who accepted HIV testing. The prevalence of HIV infection was 9.7% (95% confidence interval (CI): 8.6-10.8%). The overall prevalence of anaemia during pregnancy (Hb level < 11 g/dl) was 66% (95% CI: 64-68%). The prevalence of mild (10 g/dl < or = Hb < 11 g/dl), moderate (7 g/dl < or = Hb < 10 g/dl) and severe (Hb < 7 g/dl) anaemia was 30.8%, 33.5% and 1.7%, respectively. The prevalence of anaemia was 78.4% in HIV-infected women versus 64.7% in HIV-seronegative women (P < 0.001). Although the relative risk of HIV-seropositivity increased with the severity of anaemia, no significant association was found between degree of anaemia and HIV serostatus among the study women with anaemia. Logistic regression analysis showed that anaemia was significantly and independently related to HIV infection, advanced gestational age, and low socioeconomic status. This study confirms the high prevalence of anaemia during pregnancy in Burkina Faso. Antenatal care in this population must include iron supplementation. Although HIV-infected women had a higher prevalence of anaemia, severe anaemia was infrequent, possibly because few women were in the advanced stage of HIV disease. A short course regimen of ZDV should be well tolerated in this population.     

Sickle cell anaemia trial

The major cause of death in sickle cell anaemia is from infection, especially infection caused by Streptococcus pneumoniae. Meningitis, pneumonia and septicaemia caused by this organism are the primary types of infection leading to death. Children under three years of age are at highest risk. We have known for over twenty years that approximately 30 per cent of the infants born with sickle cell anaemia will become infected in the first three years of life and one-third can be expected to die from the infection. These data were the reason that we conducted the Prophylactic Penicillin Study (PROPS), a trial to investigate the effectiveness of oral prophylactic penicillin in preventing severe infection due to S. pneumoniae. This investigation was a very efficient, cost effective study because of its timeliness and its conduct within the framework of an ongoing study. Moreover, the question being answered was simple and focused with up-to-date data that permitted accurate estimates of sample size and incidence.     

The contribution of hookworm and other parasitic infections to haemoglobin and iron status among children and adults in western Kenya.

A cross-sectional study of 729 children and adults in western Kenya investigated the impact of infection with hookworm, Ascaris lumbricoides, Trichuris trichiura, Schistosoma mansoni and malaria on iron status. In bivariate analyses, hookworm intensities as low as 300 eggs/g of faeces were negatively related to levels of haemoglobin (Hb) and serum ferritin (SF). Malaria parasitaemia was negatively related to Hb and positively related to SF, while S. mansoni intensities were negatively related to SF. Multivariate regression analysis was done to identify predictors of Hb and SF levels. In children, age (in years) was the only predictor for Hb (B = 1.7 g/L) and only malaria parasitaemia (negative, light, moderate, heavy) was retained in the model for log10 SF (B = 0.097 microgram/L). In adults, hookworm infection and malaria parasitaemia together with age, sex, pregnancy, SF levels < 12 micrograms/L and elevated body temperature were significant predictors of low Hb. The regression coefficient for hookworm egg count (for increments of 100 eggs/g) was -1.3 g/L. Significant interactions between sex and age and between sex and malaria parasitaemia were revealed. Age and malaria parasitaemia were significant predictors only among females, with a regression coefficient for malaria parasitaemia of -6.9 g/L. The regression coefficient for hookworm did not change when SF < 12 micrograms/L was taken out of the model, indicating that the effect of hookworm cannot be explained by low iron stores alone. Using SF as the dependent variable, hookworm and S. mansoni intensities together with age and sex were retained in the model. The regression coefficients for hookworm egg count (increments of 100 eggs/g) and S. mansoni egg count (increments of 10 eggs/g) were -0.011 microgram/L and -0.012 microgram/L, respectively. Iron deficiency was a problem in this population and hookworm infections contributed significantly to this situation.     

Neonatal screening for hemoglobinopathies in Rio de Janeiro, Brazil]

OBJECTIVE: To describe the main results obtained in the first 15 months of neonatal screening for sickle cell disease in the state of Rio de Janeiro, Brazil, from August 2000 to November 2001. METHODS: Starting in August 2000, blood samples began to be collected for sickle cell disease screening from all newborns receiving care in primary health care clinics in the state of Rio de Janeiro. The samples were submitted to high-resolution liquid chromatography. If the resulting chromatogram was compatible with sickle cell disease, the child and the parents were referred for diagnostic confirmation and treatment. RESULTS: Between August 2000 and November 2001, 99 260 newborns were screened. There was one case of homozygous Hb C. On average, one of every 27 newborns who were screened presented sickle cell trait (Hb AS). Sickle cell disease was observed in 83 cases, or one new case in each 1 196 births. The 83 consisted of: 62 Hb S, 18 Hb SC, and 3 Hb SD. One child did not appear for diagnostic confirmation. The 82 children who were followed up by the program presented 15 intercurrent illnesses (upper respiratory infections, fever, splenic sequestration crises, hand-foot syndrome, and vascular occlusion), resulting in seven hospital admissions. Blood transfusions were necessary with 15 children, but none developed alloimmunization. All the other babies were doing well with the use of prophylactic penicillin. CONCLUSIONS: Our data show the importance of early diagnosis for sickle cell disease, so as to prevent the frequent infectious complications faced by these patients.     

The effects of neonatal screening for sickle cell disorders on lifetime treatment costs and early deaths avoided: a modelling approach

BACKGROUND: The aim of the study was to calculate the cost to the UK National Health Service of providing treatment services for patients with sickle cell disorders. The rates of differential morbidity and mortality, in the first 10 years of life, between screen-detected early diagnosed and clinically presenting late diagnosed cohorts of sickle cell disorder patients are also estimated. METHOD: A cost model was developed, based on predictions of survival and the incidence of sickle cell disorder-related events. Direct data from the NHS are lacking, so data were incorporated from disparate sources. Patients with sickle cell disorders were divided into two categories: those with sickle cell anaemia and those with sickle HbC disease. RESULTS: Differentiating between sickle cell anaemia and sickle HbC disorder patients, the results show that the undiscounted (discounted at 6 per cent) lifetime treatment costs range from pound sterling 92323 (pound sterling 24917) to pound sterling 185614 (pound sterling 53861). The number of early deaths avoided per 100 births, as a result of early diagnosis through screening, ranges from 0.57 to 1.25. CONCLUSIONS: The resulting estimates may act as a guide to those involved in the planning of health care provision with regard to the resources required to treat sickle cell disorder patients. Such information may also be incorporated into the evaluation of both antenatal and neonatal screening programmes for sickle cell disorders.     

Mild riboflavin deficiency is highly prevalent in school-age children but does not increase risk for anaemia in Côte d'Ivoire

There are few data on the prevalence of riboflavin deficiency in sub-Saharan Africa, and it remains unclear whether riboflavin status influences the risk for anaemia. The aims of this study were to: (1) measure the prevalence of riboflavin deficiency in children in south-central C?te d'Ivoire; (2) estimate the riboflavin content of the local diet; and (3) determine if riboflavin deficiency predicts anaemia and/or iron deficiency. In 5- to 15-year-old children (n 281), height, weight, haemoglobin (Hb), whole blood zinc protoporphyrin (ZPP), erythrocyte glutathione reductase activity coefficient (EGRAC), serum retinol, C-reactive protein (CRP) and prevalence of Plasmodium spp. (asymptomatic malaria) and Schistosoma haematobium (bilharziosis) infections were measured. Three-day weighed food records were kept in twenty-four households. Prevalence of anaemia in the sample was 52%; 59% were iron-deficient based on an elevated ZPP concentration, and 36% suffered from iron deficiency anaemia. Plasmodium parasitaemia was found in 49% of the children. Nineteen percent of the children were infected with S. haematobium. Median riboflavin intake in 5- to 15-year-old children from the food records was 0.42 mg/d, approximately 47% of the estimated average requirement for this age group. Prevalence of riboflavin deficiency was 65%, as defined by an EGRAC value > 1.2. Age, elevated CRP and iron deficiency were significant predictors of Hb. Riboflavin-deficient children free of malaria were more likely to be iron deficient (odds ratio; 3.07; 95% CI 1.12, 8.41). In conclusion, nearly two-thirds of school-age children in south-central C?te d'Ivoire are mildly riboflavin deficient. Riboflavin deficiency did not predict Hb and/or anaemia, but did predict iron deficiency among children free of malaria.     

Reduction in erythrocytic GSH level and stability in Plasmodium vivax malaria

The existence of haemolytic anaemia in malaria indicates disturbances in red cell stability due to physical as well as metabolic stress attributable to the malarial parasite. As erythrocytic reduced glutathione (GSH) is involved in maintaining the integrity of red cells, the status of erythrocytic GSH was studied in 40 patients infected with Plasmodium vivax before and after therapy with chloroquine. 40 normal subjects, age- and sex-matched, were studied as controls. The level of erythrocytic GSH of malaria patients during infection and before therapy was significantly lower in comparison with controls (P less than 0.0005). Instability of GSH was recorded in 17 of 40 patients, while none of the controls showed such a defect. There was a progressive decrease in GSH level and stability of the host red cells with increasing parasitaemia. Normal values were obtained following therapy and cure of malaria indicating that the changes in GSH level and stability are induced by P. vivax. Alterations in the GSH metabolism may represent one of the factors contributing to the severity of anaemia in malaria due to P. vivax infection.     

Prevalence and risk factors for anaemia in pregnant women of eastern Sudan

The prevalence and possible risk factors for anaemia were investigated in 744 pregnant Sudanese women attending the antenatal clinic of New Halfa teaching hospital, eastern Sudan between October 2003 and April 2004. Of those, 466 (62.6%) had anaemia (haemoglobin [Hb]: <11 gm/dl); 52.4% had mild anaemia (Hb: 9.0-10.9 gm/dl); 8.1% had moderate anaemia (Hb: 7.0-8.9 gm/dl); and 2.2% had severe anaemia (Hb: <7 gm/dl), respectively. The prevalence of anaemia (73.2%) was significantly high in grandmultigravidae. Univariate and multivariate analysis showed that age and parity were not significantly associated with anaemia. Malaria (OR = 4.5, 95% CI 2.5-8.1; P < 0.0001) and pica (OR = 1.6, 95% CI 1.05-2.6; P = 0.03) were the risk factors for anaemia. Thus, preventive measures against malaria (chemoprophylaxis and insecticide-treated bednets) may be needed for all pregnant women irrespective of their age or parity.     

Limited influence of haemoglobin variants on Plasmodium falciparum msp1 and msp2 alleles in symptomatic malaria

Haemoglobin (Hb) S, HbC, and alpha(+)-thalassaemia confer protection from malaria. Accordingly, these traits may influence the multiplicity of infection (MOI) of Plasmodium falciparum and the presence of distinct parasite genotypes. In 840 febrile children in northern Ghana, we typed the P. falciparum merozoite surface protein genes (msp1, msp2) and examined effects of the Hb variants on MOI and parasite diversity. HbAC, HbAS, heterozygous, and homozygous alpha(+)-thalassaemia occurred in 21, 5, 29 and 4% of the children, respectively. Plasmodium falciparum was detected in 95%. The haemoglobinopathies did not influence MOI, nor did the Hb type bias the distribution of the msp allelic families. However, IC type parasites were most common among patients with homozygous alpha(+)-thalassaemia (93%), less frequent in heterozygotes (89%), and least frequent in alpha-globin normal children (84%, P(chi2 trend) = 0.03). The opposite was seen for Mad20 type parasites (34%, 47%, 53%, P(chi2 trend) = 0.02). Only a few of the 72 individual msp alleles were selected by the haemoglobinopathies. HbC and alpha(+)-thalassaemia are frequent in northern Ghana. In symptomatic children, the effect of Hb variants on parasite multiplicity and diversity appears to be limited. This may reflect an actual lack of influence or indicate abrogation in symptomatic malaria.     

Plasmodium falciparum or P. malariae parasitemia in carriers of sickle cell trait in various Benin biotypes]

The prevalence of malaria and the frequency of gene S were surveyed in two different regions of Benin, savana and coastal lacustrine regions. In both regions, prevalence of malaria was not significantly different between Hb AA people and Hb AS people. Gene S prevalence was not modified by age, excepted for Hb SS which was not found in people upper than 25 years. In holoendemic area, i.e. lacustrine region, means of P. falciparum parasitaemia were significantly lower in Hb AS children than in Hb AA children. Sickle cell trait did not reduce the prevalence of malaria but seemed to decrease the level of parasitaemia.