Stephan Ehrhardt

Hemoglobin C and Resistance to Severe Malaria in Ghanaian Children

Hemoglobin (Hb) C has been reported to protect against severe malaria. It is unclear whether relative resistance affects infection, disease, or both. Its extent may vary between regions and with disease pattern. We conducted a case-control study of children with severe malaria, asymptomatic parasitemic children, and healthy children in Ghana. HbAC did not prevent infection but reduced the odds of developing severe malaria and severe anemia. Protection was stronger with HbAS. The frequencies of HbCC and HbSC decreased, from healthy children to asymptomatic parasitemic children to children with severe malaria. These data support the notion that natural selection of HbC occurs because of the relative resistance it confers against severe malaria but argue against the notion that HbC offers resistance to infection.

A randomized, placebo-controlled, double-blind trial on sulfadoxine–pyrimethamine alone or combined with artesunate or amodiaquine in uncomplicated malaria

The therapeutic efficacy of sulfadoxine–pyrimethamine (SP) alone, SP plus amodiaquine (AQ), and SP plus artesunate (AS) was assessed in a randomized, placebo‐controlled, and double‐blind trial among 438 children with uncomplicated Plasmodium falciparum malaria in northern Ghana. Clinical and parasitological responses were monitored for 28u2003days following treatment; 86%, 98% and 97% of SP‐, SPu2003+u2003AQ‐, and SPu2003+u2003AS‐treated patients achieved adequate clinical and parasitological response (ACPR) within 2u2003weeks, respectively. Parasite clearance was better with SPu2003+u2003AS than with SP or SPu2003+u2003AQ treatment but re‐infections were more common. Polymerase chain reaction (PCR)‐corrected rates of ACPR at day 28 were 72.2% for SP, 94.1% for SPu2003+u2003AQ (Pu2003<u20030.0001), and 94.5% for SPu2003+u2003AS (Pu2003<u20030.0001). Gametocyte prevalence and density 1u2003week after treatment were highest in children treated with SP, and lowest in patients receiving SPu2003+u2003AS. No severe adverse events attributable to study medication were observed. In northern Ghana, more than one of four children suffered SP treatment failure within 4u2003weeks. Both SPu2003+u2003AQ and SPu2003+u2003AS are efficacious alternative therapeutic options in this region. Although SPu2003+u2003AS and SPu2003+u2003AQ treatments have virtually identical cure rates, rapid parasite clearance and pronounced gametocidal effects are the advantages of the former, whereas cost and a lower rate of late re‐infections are those of the latter.

A syringe exchange programme in prison as prevention strategy against HIV infection and hepatitis B and C in Berlin, Germany

In two prisons in Berlin, Germany, provision of sterile injection equipment for injecting drug users (IDUs) started in 1998. To assess the programmes impact, the frequency of injecting drug use and syringe sharing, and the incidence of HIV, HBV, and HCV infection were determined in a follow-up study. Of all IDUs (n=174), 75% continued to inject. After the project start the level of syringe sharing declined from 71% during a 4-month period of previous imprisonment to 11% during the first 4 months of follow-up, and to virtually zero thereafter. Baseline seroprevalences for HIV, HBV, and HCV were 18, 53, and 82%. HIV and HCV seroprevalence at baseline was significantly associated with drug injection in prison prior to the project start. No HIV and HBV seroconversions, but four HCV seroconversions occurred. The provision of syringes for IDUs in appropriate prison settings may contribute to a substantial reduction of syringe sharing. However, the prevention of HCV infection requires additional strategies.

Reduced prevalence of Plasmodium falciparum infection and of concomitant anaemia in pregnant women with heterozygous G6PD deficiency.

Glucose‐6‐phosphate dehydrogenase (G6PD) deficiency confers protection against malaria in children, yet its role in malaria in pregnancy is unknown. In a cross‐sectional study among 529 pregnant Ghanaian women, Plasmodium falciparum infection, anaemia and G6PD genotypes were assessed. Of these, 30.4% were heterozygous and 2.6% were homozygous for G6PD deficiency. The prevalence of P. falciparum infection decreased from 66% in G6PD‐normal women to 58% in heterozygotes, and to 50% in individuals with homozygous G6PD deficiency (, Pu2003=u20030.04). Multivariate analysis revealed that in multigravid women but not in primigravidae, heterozygous G6PD deficiency was associated with a reduced risk of P. falciparum infection (Odds ratio (OR), 0.6; 95% confidence interval (95% CI), [0.4–0.9]). This protection against infection was limited to the third trimenon of pregnancy. In addition, heterozygous G6PD deficiency was associated with a reduced risk of anaemia among infected multigravidae (OR, 0.5 [0.3–1.0]). Pregnancy is a period of high vulnerability to malaria. The results of this study provide evidence for protection against malaria in pregnancy caused by heterozygous G6PD deficiency. This advantage, even if confined to multigravid women, may contribute to the selection of G6PD variants in malaria‐endemic regions.

iNOS promoter variants and severe malaria in Ghanaian children

Nitric oxide is an important mediator in the host defence against Plasmodium falciparum malaria. It has antiparasitic effects in vitro. However, its role in clinical disease remains controversial. Polymorphisms in the inducible nitric oxide synthase promoter (iNOS; −954G→C, −1173C→T, −2.6u2003kb CCTTT(n) microsatellite) may influence susceptibility to and severity of malaria. We tested this hypothesis in a case–control study among Ghanaian children with severe malaria (SM) and asymptomatic parasitaemia, respectively, and in healthy controls. In this study, the respective frequencies of iNOS−954G→C and −1173C→T did not differ between groups but ≥13 microsatellite copies were associated with SM. −954G→C and −1173C→T were in linkage disequilibrium with CCTTT(8) and CCTTT(13), respectively. −954G→C/CCTTT(8) protected against hyperparasitaemia whereas −1173C→T/CCTTT(13) increased fatality. These findings suggest that iNOS promoter haplotypes rather than single nucleotide polymorphisms are associated with malaria in Ghanaian children.

Efficacy of chloroquine in the treatment of uncomplicated, Plasmodium falciparum malaria in northern Ghana

Abstract Chloroquine (CQ) resistance in Plasmodium falciparum contributes to growing malaria-attributable morbidity and mortality in sub-Saharan Africa. However, the extent and degree of such resistance vary considerably between endemic areas. Data on CQ resistance in northern Ghana are almost entirely lacking. The therapeutic efficacy of CQ in uncomplicated malaria was therefore assessed, in a standard, 14-day protocol, in 225 children aged <5 years in Tamale, in the Northern region of Ghana. Early treatment failure (ETF) was observed in 11% of the children and late treatment failure in 18%. High initial parasite density and young age were independent predictors for ETF. Resistant parasitological responses (RI-RIII) were seen in 57% of the cases that could be classified. More than half of these responses occurred in children fulfilling the criteria for adequate clinical response (ACR), indicating a considerable lack of agreement between parasitological and clinical outcome. During the follow-up period, haemoglobin levels increased by approximately 1g/dl not only in patients with ACR but also in those who experienced clinical failure more than 1 week post-treatment. As CQ-treatment failure occurred in >25% of the children and more than half of the parasitological responses indicated resistance, current recommendations for the treatment of uncomplicated malaria in young children in northern Ghana have to be reconsidered.

Renal dysfunction in children with uncomplicated, Plasmodium falciparum malaria in Tamale, Ghana.

Abstract In a study performed in Tamale, in the Northern region of Ghana, cystatin C, a new and sensitive indicator of the glomerular filtration rate (GFR), was used to estimate the frequency of renal dysfunction in 78 children with uncomplicated, Plasmodium falciparum malaria. The excretion in urine of albumin, immunoglobulin G and α1-microglobulin was also investigated. Plasma concentrations of cystatin C were found to be elevated in 17% of the children, indicating subclinical impairment of renal function. As most (85%) of the children had glomerular as well as tubular patterns of proteinuria, it appears that both glomerulonephritis and damage to tubular cells often occur in P. falciparum malaria.

Plasmodium falciparum multiplicity correlates with anaemia in symptomatic malaria.

In 366 Ghanaian children with symptomatic Plasmodium falciparum malaria, low haemoglobin levels and severe anaemia were associated with a high multiplicity of infection (MOI) and with distinct merozoite surface protein alleles. High MOI not only reflects premunition but may also contribute to anaemia in symptomatic malaria.

Short Communication: Prevalence of mutations associated with resistance to atovaquone and to the antifolate effect of proguanil in Plasmodium falciparum isolates from northern Ghana

Atovaquone‐proguanil has recently been introduced for the treatment and prophylaxis of malaria. However, resistance of Plasmodium falciparum is increasingly reported. We assessed P. falciparum polymorphisms associated with resistance to atovaquone (cytochrome b, cytb) and to cycloguanil, the active compound of proguanil (dihydrofolate reductase, dhfr) in 100 isolates from northern Ghana. None of these exhibited cytb codon 268 mutations. Moreover, no dhfr V16A, S108T or I164L mutations linked with cycloguanil resistance were detected. However, dhfr triple mutants (S108N‐I51L‐C59R) conferring resistance to proguanil and sulphadoxine‐pyrimethamine were seen in 51% of the isolates. In northern Ghana, P. falciparum cytb codon 268 mutations associated with atovaquone resistance are absent. Although proguanil appears to act synergistically with atovaquone in a way different from its antifolate property, the abundance of dhfr polymorphisms will likely compromise the prevention of dissemination of atovaquone‐resistant parasites once emerged.