Control of disease due to perennially transmitted malaria in children of rural Sierra Leone.

The effects of the community-wide use of lambdcyhalothrin-impregnated mosquito nets and fortnightly Maloprim/Vplacebo prophylaxis, singly or in combination, were assessed in a randomised controlled trial as control measures to reduce disease due to perennially transmitted Plasmodium falciparum in children of Bo district, Southern Sierra Leone. Age-specific illness thresholds of 2000 Plasmodium falciparum parasites/ul for children younger than 24 months and a corresponding level of 5000 Plasmodium falciparum parasites for older children, together with fever, were used as case definitions of clinical malaria. Using an active case detection scheme, children were clinically screened and thick smears for parasitological diagnosis collected from those fulfilling any one or more of the set of sampling criteria. A series of cross-sectional surveys (pre-rain and immediately post rainy season) were also conducted during which, in addition to clinical and parasitological data, spleen size and haematocrit level were assessed for all children irrespective of health status. A 49% protective efficacy against cases of Plasmodium falciparum clinical malaria was demonstrated in children using the insecticide-impregnated mosquito nets. The impact of combining MaloprimR prophylaxis with use of the lambdacyhalothrin-impregnated mosquito nets resulted in a 72% protective efficacy against disease due to Plasmodium falciparum. The interventions unexpectedly demonstrated a significant impact on some of the traditional malariometric indices; reducing the average spleen rate and the geometric mean parasite density. It was found that children using the impregnated mosquito nets exhibited the largest increase in the mean haematocrit level documented during this trial (which lasted a year). These results provide additional evidences that synthetic pyrethroid-impregnated mosquito nets have the potential of serving as an alternative strategy for the control of disease due to perennially transmitted Plasmodium falciparum

Review: Intermittent preventive treatment--a new approach to the prevention of malaria in children in areas with seasonal malaria transmission.

Intermittent preventive treatment, the administration of a full course of an anti-malarial treatment to a population at risk at specified time points regardless of whether or not they are known to be infected, is now a recommended approach to the prevention of malaria in pregnancy and is being explored as a potential way of preventing malaria in infants. However, in many malaria endemic areas, the main burden of malaria is in older children and increasing use of insecticide treated bednets is likely to increase further the proportion of episodes of malaria that occur in older children. Recently, it has been shown in Senegal and in Mali that intermittent preventive treatment given to older children during the malaria transmission season can be remarkably effective in preventing malaria. This approach to malaria control is likely to be most effective in areas with a high level of malaria transmission concentrated in a short period of the year. However, several issues need to be addressed before intermittent preventive treatment in children can be advocated for use in malaria control programmes. These include: (1) determination of whether intermittent preventive treatment adds to the protection afforded by other control measures such as insecticide-treated bednets; (2) whether an effective and sustainable delivery system can be found; (3) choice of drug to be used; (4) optimum timing of drug administration; (5) the requisite interval between treatments. The potential benefits of intermittent preventive treatment in children are substantial; more research is needed to determine if this is a practical approach to malaria control

Impact of malaria control on childhood anaemia in Africa -- a quantitative review.

OBJECTIVE: To review the impact of malaria control on haemoglobin (Hb) distributions and anaemia prevalences in children under 5 in malaria-endemic Africa. METHODS: Literature review of community-based studies of insecticide-treated bednets, antimalarial chemoprophylaxis and insecticide residual spraying that reported the impact on childhood anaemia. Anaemia outcomes were standardized by conversion of packed cell volumes into Hb values assuming a fixed threefold difference, and by estimation of anaemia prevalences from mean Hb values by applying normal distributions. Determinants of impact were assessed in multivariate analysis. RESULTS: Across 29 studies, malaria control increased Hb among children by, on average, 0.76 g/dl [95% confidence interval (CI): 0.61-0.91], from a mean baseline level of 10.5 g/dl, after a mean of 1-2 years of intervention. This response corresponded to a relative risk for Hb < 11 g/dl of 0.73 (95% CI: 0.64-0.81) and for Hb < 8 g/dl of 0.40 (95% CI: 0.25-0.55). The anaemia response was positively correlated with the impact on parasitaemia (P = 0.005, P = 0.008 and P = 0.01 for the three outcome measures), but no relationship with the type or duration of malaria intervention was apparent. Impact on the prevalence of Hb < 11 g/dl was larger in sites with a higher baseline parasite prevalence. Although no age pattern in impact was apparent across the studies, some individual trials found larger impacts on anaemia in children aged 6-35 months than in older children. CONCLUSION: In malaria-endemic Africa, malaria control reduces childhood anaemia. Childhood anaemia may be a useful indicator of the burden of malaria and of the progress in malaria control