Bone marrow suppression and severe anaemia associated with persistent Plasmodium falciparum infection in African children with microscopically undetectable parasitaemia

BACKGROUND: Severe anaemia can develop in the aftermath of Plasmodium falciparum malaria because of protracted bone marrow suppression, possibly due to residual subpatent parasites. MATERIALS AND METHODS: Blood was collected from patients with recent malaria and negative malaria microscopy. Detection of the Plasmodium antigens, lactate dehydrogenase (Optimal(®)), aldolase and histidine rich protein 2 (Now malaria(®)) were used to differentiate between patients with (1) no malaria, (2) recent cleared malaria, (3) persistent P. falciparum infection. Red cell distribution width (RDW), plasma levels of soluble transferrin receptor (sTfR) and erythropoietin (EPO) were measured as markers of erythropoiesis. Interleukin (IL) 10 and tumour necrosis factor (TNF)α were used as inflammation markers. RESULTS: EPO was correlated with haemoglobin, irrespective of malaria (R = -0.36, P < 0.001). Persistent P. falciparum infection, but not recent malaria without residual parasites, was associated with bone marrow suppression i.e., low RDW (P < 0.001 vs. P = 0.56) and sTfR (P = 0.02 vs. P = 0.36). TNF-α and IL-10 levels were not associated with bone marrow suppression. CONCLUSION: In the treatment of malaria, complete eradication of parasites may prevent subsequent development of anaemia. Severely anaemic children may benefit from antimalarial treatment if antigen tests are positive, even when no parasites can be demonstrated by microscopy

Complement activation in Ghanaian children with severe Plasmodium falciparum malaria

<p>Abstract</p> <p>Background</p> <p>Severe anaemia (SA), intravascular haemolysis (IVH) and respiratory distress (RD) are severe forms of <it>Plasmodium falciparum </it>malaria, with RD reported to be of prognostic importance in African children with malarial anaemia. Complement factors have been implicated in the mechanism leading to excess anaemia in acute <it>P. falciparum </it>infection.</p> <p>Methods</p> <p>The direct Coombs test (DCT) and flow cytometry were used to investigate the mean levels of RBC-bound complement fragments (C3d and C3bαβ) and the regulatory proteins [complement receptor 1 (CD35) and decay accelerating factor (CD55)] in children with discrete clinical forms of <it>P. falciparum </it>malaria. The relationship between the findings and clinical parameters including coma, haemoglobin (Hb) levels and RD were investigated.</p> <p>Results</p> <p>Of the 484 samples tested, 131(27%) were positive in DCT, out of which 115/131 (87.8%) were positive for C3d alone while 16/131 (12.2%) were positive for either IgG alone or both. 67.4% of the study population were below 5 years of age and DCT positivity was more common in this age group relative to children who were 5 years or older (Odds ratio, OR = 3.8; 95%CI, 2.2–6.7, p < 0.001). DCT correlated significantly with RD (β = -304, p = 0.006), but multiple regression analysis revealed that, Hb (β = -0.341, p = 0.012) and coma (β = -0.256, p = 0.034) were stronger predictors of RD than DCT (β = 0.228, p = 0.061). DCT was also not associated with IVH, p = 0.19, while spleen size was inversely correlated with Hb (r = -402, p = 0.001). Flow cytometry showed similar mean fluorescent intensity (MFI) values of CD35, CD55 and C3bαβ levels on the surfaces of RBC in patients and asymptomatic controls (AC). However, binding of C3bαβ correlated significantly with CD35 or CD55 (p < 0.001).</p> <p>Conclusion</p> <p>These results suggest that complement activation contributed to anaemia in acute childhood <it>P. falciparum </it>malaria, possibly through induction of erythrophagocytosis and haemolysis. In contrast to other studies, this study did not find association between levels of the complement regulatory proteins, CD35 and CD55 and malarial anaemia. These findings suggest that complement activation could also be involved in the pathogenesis of RD but larger studies are needed to confirm this finding.</p