Anemia due to infection is a major health problem in endemic areas for young children and pregnant women. The anemia is caused by excess removal of nonparasitized erythrocytes in addition to immune destruction of parasitized red cells, and impaired compensation for this loss by bone marrow dysfunction. The pathogenesis is complex, and a predominant mechanism has not been identified. Certain parasite and host characteristics may modify the anemia. Concomitant infections and nutritional deficiencies also contribute to anemia and may interact with the malarial infection. Few preventive strategies exist, and the management of severe malarial anemia with blood transfusion carries a risk of HIV transmission. The current increase in malaria-specific childhood mortality in sub-Saharan Africa attributed to drug-resistant infection is likely partly related to an increase in severe anemia. This review summarizes recent findings on the pathogenesis and epidemiology of malarial anemia.
Transmitted drug resistance (TDR) is a clinical and epidemiological problem because it may contribute to failure of antiretroviral treatment. The prevalence of TDR varies geographically, and its prevalence in Sweden during the last decade has not been reported. Plasma samples from 1,463 patients newly diagnosed with HIV-1 infection between 2003 and 2010, representing 44% of all patients diagnosed in Sweden during this period, were analyzed using the WHO 2009 list of mutations for surveillance of TDR. Maximum likelihood phylogenetic analyses were used to determine genetic subtype and to investigate the relatedness of the sequences. Eighty-two patients showed evidence of TDR, representing a prevalence of 5.6% (95% CI: 4.5%–6.9%) without any significant time trends or differences between patients infected in Sweden or abroad. Multivariable logistic regression showed that TDR was positively associated with men who have sex with men (MSM) and subtype B infection and negatively associated with CD4 cell counts. Among patients with TDR, 54 (68%) had single resistance mutations, whereas five patients had multi-drug resistant HIV-1. Phylogenetic analyses identified nine significantly supported clusters involving 29 of the patients with TDR, including 23 of 42 (55%) of the patients with TDR acquired in Sweden. One cluster contained 18 viruses with a M41L resistance mutation, which had spread among MSM in Stockholm over a period of at least 16 years (1994–2010). Another cluster, which contained the five multidrug resistant viruses, also involved MSM from Stockholm. The prevalence of TDR in Sweden 2003–2010 was lower than in many other European countries. TDR was concentrated among MSM, where clustering of TDR strains was observed, which highlights the need for continued and improved measures for targeted interventions.
Acute haemolysis associated with clinical episodes of high-level Plasmodium falciparum parasitaemia was studied in 20 children from an holoendemic area (coastal Tanzania). The change in blood haemoglobin (Hb) concentration ranged from -46 to g/L during the 72-h observation period and was linearly related to maximum parasitaemia. Balance studies between loss of blood Hb, increase in plasma Hb and appearance of Hb in the urine indicated that extravascular clearance of red cells was the predominant mode of erythrocyte clearance. Most subjects, however, showed minor signs of intravascular haemolysis. The plasma Hb was << 1% of blood Hb and haemoglobinuria was detected in 14/20 children but the excretion of Hb in urine was < 0.5% of total Hb loss. Haemoglobinuria was, however, a marker of severe haemolysis, since the maximum blood Hb loss in children without haemoglobinuria was 10 g/L. Erythrocyte-bound opsonins known to induce erythrophagocytosis, i.e., complement C3c fragments and autologous IgG, were increased in all patients. In the patients with major haemolysis, the changes correlated to the haemolysis over time. Hence, a similar mechanism for predominantly extravascular erythrocyte clearance may be operative in acute malarial anaemia, normal erythrocyte senescence and other forms of acute haemolysis.
Childhood anaemia is a major public health problem in malaria holoendemic areas. We assessed the effects of antimalarial treatment in an area with drug-resistant falciparum malaria on haemoglobin levels in small children by applying the 1996 World Health Organization in vivo method for the evaluation of standard chloroquine treatment at the community level. In Fukayosi village, coastal Tanzania, 117 children aged 5-36 months with clinical malaria episodes were treated with chloroquine syrup (25 mg/kg). Early treatment failure (ETF) occurred in 20% and late treatment failure (LTF) in 22% of cases. Age > 1 year and malnutrition were protective factors against ETF. The evidence that chloroquine treatment could not prevent an exacerbation of anaemia was (i) the fact that the fall in haemoglobin level after 72 h was significantly greater in ETF than in children with LTF and an adequate clinical response, and (ii) the absence of any haematological improvement at follow-up in children receiving chloroquine alone, even in true treatment successes. In contrast, pyrimethamine/sulfadoxine administered to treatment failures improved the haemoglobin level significantly > 21 d after treatment started (mean difference 14 g/L, 95% confidence interval 2.1-27). We conclude that, when chloroquine treatment of childhood malaria is associated with a 20% ETF rate, the haemoglobin response is unsatisfactory and there is a need to change the recommended first-line treatment.
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