[Efficacy is good, impact is great]. / L'efficacité c'est bien, l'impact c'est top!

This article summarizes the different stages of research for the development of medical interventions and their specific characteristics in terms of design, population, resources, importance of results and scientific interest. The emphasis is focused on the two final stages of development, the effectiveness and the impact. An example from our own experience is given to illustrate the reduction of the effect of an intervention against malaria in young children at different stages of the development of the intervention, and the parallel decrease of the recognition by the scientific community of the importance of these results.

Towards a comprehensive simulation model of malaria epidemiology and control.

Planning of the control of Plasmodium falciparum malaria leads to a need for models of malaria epidemiology that provide realistic quantitative prediction of likely epidemiological outcomes of a wide range of control strategies. Predictions of the effects of control often ignore medium- and long-term dynamics. The complexities of the Plasmodium life-cycle, and of within-host dynamics, limit the applicability of conventional deterministic malaria models. We use individual-based stochastic simulations of malaria epidemiology to predict the impacts of interventions on infection, morbidity, mortality, health services use and costs. Individual infections are simulated by stochastic series of parasite densities, and naturally acquired immunity acts by reducing densities. Morbidity and mortality risks, and infectiousness to vectors, depend on parasite densities. The simulated infections are nested within simulations of individuals in human populations, and linked to models of interventions and health systems. We use numerous field datasets to optimise parameter estimates. By using a volunteer computing system we obtain the enormous computational power required for model fitting, sensitivity analysis, and exploration of many different intervention strategies. The project thus provides a general platform for comparing, fitting, and evaluating different model structures, and for quantitative prediction of effects of different interventions and integrated control programmes.

Cost-sharing strategies combining targeted public subsidies with private-sector delivery achieve high bednet coverage and reduced malaria transmission in Kilombero Valley, southern Tanzania.

BACKGROUND: Cost-sharing schemes incorporating modest targeted subsidies have promoted insecticide-treated nets (ITNs) for malaria prevention in the Kilombero Valley, southern Tanzania, since 1996. Here we evaluate resulting changes in bednet coverage and malaria transmission. METHODS: Bednets were sold through local agents at fixed prices representing a 34% subsidy relative to full delivery cost. A further targeted subsidy of 15% was provided to vulnerable groups through discount vouchers delivered through antenatal clinics and regular immunizations. Continuous entomological surveys (2,376 trap nights) were conducted from October 2001 to September 2003 in 25 randomly-selected population clusters of a demographic surveillance system which monitored net coverage. RESULTS: Mean net usage of 75% (11,982/16,086) across all age groups was achieved but now-obsolete technologies available at the time resulted in low insecticide treatment rates. Malaria transmission remained intense but was substantially reduced: Compared with an exceptionally high historical mean EIR of 1481, even non-users of nets were protected (EIR [fold reduction] = 349 infectious bites per person per year [x4]), while the average resident (244 [x6]), users of typical nets (210 [x7]) and users of insecticidal nets (105 [x14]) enjoyed increasing benefits. CONCLUSION: Despite low net treatment levels, community-level protection was equivalent to the personal protection of an ITN. Greater gains for net users and non-users are predicted if more expensive long-lasting ITN technologies can be similarly promoted with correspondingly augmented subsidies. Cost sharing strategies represent an important option for national programmes lacking adequate financing to fully subsidize comprehensive ITN coverage.

Child mortality and malaria transmission intensity in Africa.

The desirability of controlling malaria transmission in the areas of highest endemicity of Plasmodium falciparum has long been debated. Most recently, it has been claimed that rates of malaria morbidity are no higher in areas of very high transmission in Africa than they are in places with lower inoculation rates. We now review the literature on the relationship of morbidity and mortality to malaria transmission intensity, and have linked published child mortality and malaria transmission rates to examine how age-specific mortality actually varies with the inoculation rate of P. falciparum.

The contribution of health-care services to a sound and sustainable malaria-control policy.

HIV and AIDS, tuberculosis, and malaria, besides presenting a large mortality and morbidity burden in developing countries, are also responsible for poor economic development. In the past international agencies devoted resources and efforts to control malaria and other diseases without taking into account health-system performance and sustainability. Even assuming that the Global Fund to Fight AIDS, Tuberculosis, and Malaria (GFATM)--a recent international initiative--would provide the necessary funds, a poorly performing health-care system will not be able to use these funds optimally. Moreover, even if all interventions are cost-effective, their impact on mortality and morbidity will only be marginal if access to proper care is not guaranteed. It is the responsibility of scientists and health managers to highlight to donor agencies the importance of an accessible and well functioning health-care system at all levels for the control of specific diseases.

Usefulness of a dispensary-based case-control study for assessing morbidity impact of a treated net programme.

BACKGROUND: Case-control studies have been proposed as an appropriate tool for health impact evaluation of insecticide-treated nets (ITN) programmes. METHODS: A dispensary-based case-control study was carried out in one village in Tanzania. Each case of fever and parasitaemia in a child under 5 years was paired with one community and one dispensary control without fever and parasitaemia. Cases and controls were compared with regard to ITN ownership and other factors assessed by a questionnaire. A cross-sectional survey of factors associated with parasitaemia, including ITN use, was carried out during the study. Dispensary attendance rates of the study children were calculated using passive case detection data. RESULTS: Cases and dispensary controls had higher dispensary attendance rates compared to community controls and children with nets attended more for most of the illness events. A comparison of cases and community controls showed a strong and statistically significant association between untreated net use and being a case (odds ratio [OR] = 2.1, 95% CI : 1.3-3.4). For those with ITN there was a smaller and weaker association between risk of being a case and ITN use (OR =1.4, 95% CI : 0.9-2.2). Comparison of cases and dispensary controls showed no association between untreated or treated nets and the risk of being a case (for treated nets OR = 0.9, 95% CI : 0.5-1.4 and for untreated nets OR = 1.2, 95% CI : 0.7-2.0). These results are contrary to those from the cross-sectional assessment, where children with ITN had a lower prevalence of parasitaemia than those with no nets (OR = 0.5, 95% CI : 0.3-0.9), and also contrary to other assessments of the health impact of ITN in this population. CONCLUSIONS: The positive association between mild malaria and net ownership is counter-intuitive and best explained by attendance bias, since children with nets attended more frequently for all curative and preventive services at the dispensary than those without nets. Dispensary-based case-control studies may not be appropriate for assessing impact of treated nets on clinical malaria, while cross-sectional surveys might represent an attractive alternative.

Community-based questionnaires and health statistics as tools for the cost-efficient identification of communities at risk of urinary schistosomiasis.

Self-administered questionnaires, distributed by existing administrative channels to village party chairmen, head-teachers and schoolchildren, showed good diagnostic performance for the qualitative assessment of urinary schistosomiasis endemicity. At a cost 34 times below that of the WHO-recommended parasitological screening strategy, the schoolchildren's questionnaire allowed the screening of 75 out of 77 schools of a rural Tanzanian district in six weeks, and the exclusion of schools not at high risk for urinary schistosomiasis with over 90% confidence. The headteacher and party questionnaires made it possible to assess the perceived importance of a spectrum of diseases and symptoms, among which was schistosomiasis. The priority rank of schistosomiasis control was strongly correlated with the prevalence rate of the disease in the community. The questionnaires also looked for the prioritization of health among other community issues and thus contributed important information for planning at district level. Standardized monthly disease reports, sent by all primary health services, were also analysed. They allowed a zonal schistosomiasis endemicity classification.

Relationships between the outcome of Plasmodium falciparum infection and the intensity of transmission in Africa.

Establishing the relationship between transmission intensity and health outcomes is crucial for the planning of long-term malaria control programs. Unfortunately this is fraught with methodologic difficulties. In this report, we address some of these problems by considering some important parameters that have previously been ignored. One important consideration is that the incidence of infection for Plasmodium falciparum malaria is much lower than entomologic inoculation rates (EIRs), especially at higher transmission levels. Moreover, biting rates of malaria vectors per host depend on his or her biomass and thus age. We propose an algorithm for estimating human infection rates from the EIR with allowance for these two factors. We then re-analyzed 1) data on EIR and age-specific incidence of clinical malaria in two villages in Senegal and 2) a survey of infant and child mortality rates across Africa. In each case, we review analyses of incidence in relation to the EIR and carry out a new analysis of morbidity and mortality rates in relation to the estimated incidence of infection (h). Reduction in malaria transmission may result in a shift of acute malaria attacks to older ages, and thus have little impact on life-time risk of clinical attacks. However, our analysis of the Senegalese data indicates that the peak incidence rate of disease relative to infection rates is in the youngest age groups in both the villages of Dielmo (EIR = 200 infectious bites per year) and Ndiop (EIR = 20). This suggests that simple models of acquired clinical immunity can explain age-incidence profiles better when incidence is expressed in relation to h, than when expressed in relation to the EIR. Relationships of malaria transmission intensity (in endemic areas) with overall mortality are very different from those with acute morbidity. Infant mortality rates (IMRs) decrease substantially when the EIR is reduced, probably largely because of prevention of indirect mortality. However, we were are not yet able to draw strong conclusions about the shape of relationships between the IMR and h because many of the available data points have similar values of h. The effects of transmission reduction on mortality rates in older age groups are also uncertain. However, it is clear that reduction of exposure during infancy is not reflected in increased mortality at older ages.

Simple anamnestic questions and recalled water-contact patterns for self-diagnosis of Schistosoma mansoni infection among schoolchildren in western Côte d'Ivoire.

A study to determine the diagnostic performance of simple anamnestic questions and recalled water-contact patterns for self-diagnosis of Schistosoma mansoni infection was carried out in western C te d'Ivoire. A total of 322 schoolchildren were screened over four consecutive days with the Kato-Katz technique to assess S. mansoni and concurrent geohelminth infections. Children were individually interviewed by teachers using a standardized questionnaire asking about symptoms, reported diseases, and water-contact patterns. The cumulative infection prevalence of S. mansoni was 76.4%. Univariate statistics revealed a significant association between the level of S. mansoni infection and three recalled water contact patterns: (1) fishing with nets, (2) swimming/bathing and (3) crossing rivers, but no significant association with reported symptoms and/or reported diseases. Multivariate analysis revealed significant adjusted odds ratios (OR) for crossing the river Tchéorbour (OR = 3.90, P = 0.007), crossing the river Sonbour (OR = 3.90, P = 0.008) and swimming/bathing in the latter (OR = 3.28, P = 0.017). The diagnostic performance of these water-contact patterns was characterized by high specificities but low sensitivities, hence negative predictive values. In the village studied here, recalled water-contact patterns were more useful variables than anamnestic questions for schoolchildren's self-diagnosis of S. mansoni infection, but no generalization of these findings beyond this population is possible at this time.

Presence of the schistosome circulating anodic antigen (CAA) in urine of patients with Schistosoma mansoni or S. haematobium infections.

We investigated the presence of the circulating anodic antigen (CAA) in the urine of schistosomiasis patients. This genus specific antigen was hitherto demonstrated only in the serum of schistosomiasis patients. The urine of 80 patients with Schistosoma mansoni infections, 33 patients with S. haematobium infections, and 2 patients with mixed S. haematobium and S. mansoni infections were screened by a quantitative enzyme-linked immunosorbent assay (ELISA). CAA was demonstrated in 81% of those with intestinal schistosomiasis and in 97% of those with urinary schistosomiasis. CAA titers were less than 1:0.2-1:51.2. Results were compared with circulating cathodic antigen (CCA) titers in urine obtained in an indirect hemagglutination assay (IHA). CCA was generally not detectable in the urine of patients with S. haematobium infection, but was demonstrated in the urine of 85% of the patients with S. mansoni infection. Both CAA titers and CCA titers correlated positively with the number of S. mansoni eggs excreted in the feces, but CAA titers did not show a significant correlation with the number of S. haematobium eggs in urine. Both antigen titers showed a moderate correlation with the serum CAA level in schistosomiasis mansoni. The discovery of CAA in the urine of the majority of schistosomiasis patients tested suggests the use of urine samples for non-invasive immunodiagnosis of the disease.

Case studies from the biomedical and health systems research activities of the Swiss Tropical Institute in Africa.

Neither high theoretical efficacy of disease control tools, nor diagnostic accuracy, nor good compliance, nor adequate coverage can lead on its own to the final goal of community effectiveness. There is a complex relationship between these factors. The different steps in the process leading to effective health care in the community are discussed on the basis of biomedical and health systems research activities of the Swiss Tropical Institute. Schistosomiasis and malaria control provide the background to problems related to the efficacy of tools. In particular, information on the trial of a malaria vaccine candidate (SPf66) is given. Approaches to the rapid, accurate and economical diagnosis of communities at risk are discussed with reference to Schistosoma haematobium and S. mansoni. Health service support projects in Tanzania and Chad are presented to exemplify problems linked to the compliance of users/providers and coverage. Finally, it is shown that community effectiveness depends on the highest possible success rate for each step. This requires the co-operative efforts of all those involved: the scientist, the manager, the community health worker and, last but not least, the community itself.

Sero-epidemiological survey for alveolar echinococcosis (by Em2-ELISA) of blood donors in an endemic area of Switzerland.

Sera from 17,166 blood donors living in 10 cantons of northern Switzerland in an area endemic for Echinococcus multilocularis were investigated by serological survey for alveolar echinococcosis (AE). A highly species-specific antigen (Em2) and a commonly used E. granulosus hydatid fluid antigen (EgHF) were compared for their suitability in seroepidemiology. EgHF showed a degree of nonspecificity which did not allow direct detection of AE cases. Antibody reaction with Em2 resulted in the detection of 2 asymptomatic clinical cases of AE (seroprevalence 0.01%) within this population of blood donors. A further 4 persons were positive in Em2-ELISA. These 4 persons had negative imaging studies and will be followed serologically and clinically.

Intestinal amoebiasis, giardiasis and geohelminthiases: their association with other intestinal parasites and reported intestinal symptoms.

In order to determine reported signs and symptoms that may predict an intestinal parasitic infection, 241 schoolchildren in western Côte d'Ivoire were interviewed with a simple questionnaire and their stool specimens were examined over several consecutive days. Special emphasis was placed on (i) assessing infections by Entamoeba histolytica/E. dispar, Giardia duodenalis and by intestinal worms, (ii) looking for associations between these parasites, and (iii) looking for associations between these parasites and commonly perceived intestinal signs and symptoms. Complete questionnaire results, intestinal helminth infections derived from 4 Kato-Katz thick smears, and intestinal protozoa infections assessed on a single day by a formalin-ether concentration procedure were obtained from 209 children (87%). A logistic regression modelling approach showed that an infection with E. histolytica/E. dispar was significantly associated with an Entamoeba coli infection. However, for G. duodenalis, hookworm and Ascaris lumbricoides, no association was found between any of these parasites and other intestinal parasites. In a multivariate analysis reported diarrhoea was the only symptom positively associated with an E. histolytica/E. dispar infection (P = 0.028). Its diagnostic performance showed a low sensitivity (28%), a high specificity (85%) and moderate positive and negative predictive values (52% and 67%, respectively). Surprisingly, reported 'turning stomach' was less often reported by children infected with G. duodenalis (borderline significance, P = 0.057). It is concluded that reported diarrhoea could be a symptom worth exploring further for the rapid identification of schoolchildren infected with E. histolytica/E. dispar.

KINET: a social marketing programme of treated nets and net treatment for malaria control in Tanzania, with evaluation of child health and long-term survival.

We present a large-scale social marketing programme of insecticide-treated nets in 2 rural districts in southwestern Tanzania (population 350,000) and describe how the long-term child health and survival impact will be assessed. Formative and market research were conducted in order to understand community perceptions, knowledge, attitudes and practice with respect to the products to be socially marketed. We identified Zuia Mbu (Kiswahili for 'prevent mosquitoes') as a suitable brand name for both treated nets and single-dose insecticide treatment sachets. A mix of public and private sales outlets is used for distribution. In the first stage of a stepped introduction 31 net agents were appointed and trained in 18 villages: 15 were shop owners, 14 were village leaders, 1 was a parish priest and 1 a health worker. For net treatment 37 young people were appointed in the same villages and trained as agents. Further institutions in both districts such as hospitals, development projects and employers were also involved in distribution. Promotion for both products was intense and used a variety of channels. A total of 22,410 nets and 8072 treatments were sold during the first year: 18 months after launching, 46% of 312 families with children aged under 5 years reported that their children were sleeping under treated nets. A strong evaluation component in over 50,000 people allows assessment of the long-term effects of insecticide-treated nets on child health and survival, anaemia in pregnancy, and the costs of the intervention. This evaluation is based on cross-sectional surveys, and case-control and cohort studies.

Species-specific field testing of Entamoeba spp. in an area of high endemicity.

Entamoeba histolytica has been separated in recent years into 2 morphologically identical species: the apathogenic E. dispar and the pathogenic E. histolytica, only the latter being pathogenic. Although various laboratory techniques allow discrimination between the 2 species there is a lack of field data about the suitability of available diagnostic tests for use in epidemiological studies and few epidemiological studies using species-specific diagnosis have been performed at community level in endemic areas, especially in sub-Saharan Africa. We conducted a repeated cross-sectional study of 967 schoolchildren in central Côte d'Ivoire to compare and evaluate light microscopy, 2 different antigen detection assays, and one polymerase chain reaction (PCR) assay. Microscopy and a non-specific antigen capture Entamoeba enzyme-linked immunosorbent assay (ELISA) were used for the primary screening of all children (time t0). The prevalence of the E. histolytica/E. dispar species complex at t0 was 18.8% by single microscopical examination and 31.4% using the non-specific ELISA. Approximately 2 months after the initial screening, fresh stool specimens were collected on 2 consecutive days (t1 and t2) from (i) all the children who were positive by microscopy at t0 (n = 182) and (ii) 155 randomly selected children who were negative at the primary screening. These samples were tested with a second antigen detection ELISA specific for E. histolytica (n = 238) and with a species-specific PCR assay (n = 193). The second and third examinations (t1 and t2) revealed an additional 43 infections with the species complex E. histolytica/E. dispar, so that the cumulative microscopical prevalence for t1 and t2 was 27.7%. The overall prevalence of E. histolytica by species-specific ELISA antigen detection was low (0.83%), while the prevalence of E. dispar was 15%. When analysing only microscopically positive samples by PCR (n = 129), the ratio E. histolytica: E. dispar was very low (1:46), suggesting that the vast majority of Entamoeba infections in this area were apathogenic. Both species-specific tests performed well but the ELISA was easier to use for large-scale field screening.

The 1990 meningococcal meningitis epidemic of Sarh (Chad): how useful was an earlier mass vaccination?

A large outbreak of meningococcal meningitis (Serogroup A) occurred in southern Chad in 1990. We describe the epidemic in the town of Sarh, where a mass vaccination against meningococcal meningitis had taken place two years before, in 1988 (estimated coverage: 66%). Early warning that an epidemic was imminent was given at the end of February, following more than 15 recorded cases per 100,000 population on 3 consecutive weeks. This threshold proved to be adequate to predict the outbreak. A total of 721 cases were recorded at Sarh hospital and at a nearby health centre. Direct agglutination tests confirmed that Neisseria meningitis serogroup A was the only causative agent. The overall incidence rate in this population of 80,000 was 0.9%. The highest weekly incidence rate was 186 cases per 100,000 population. The mean age of the patients was 12.6 years and age-specific incidence rates ranged from 0.23% to 1.42%. The male/female sex ratio was 1.36. Overall, the mortality among hospitalized patients was 7.9%. Mortality increased during the epidemic. The major risk factor for dying was the delay until reaching hospital. Only 4 out of 29 interviewed parents said that their child had been vaccinated two years before. Among adult patients this proportion was 12/38 (32%). Because of the small numbers and because of the impossibility to check the vaccination records it was not possible to assess precisely the impact of earlier mass vaccination. However, the previous mass vaccination did not prevent this major epidemic and its impact is likely to have been unimportant.

Urinary schistosomiasis: testing with urine filtration and reagent sticks for haematuria provides a comparable prevalence estimate.

The relationship between school prevalence rates of urinary schistosomiasis, measured by urine filtration and by reagent sticks detecting haematuria, was investigated in nine primary schools in Tanzania. The aim of the study was to provide a methodological tool to compare results from studies that used these two different diagnostic techniques. A strong correlation was found between both measures (r = 0.96, P < 0.0001), and the equation of this linear relationship could be used to extrapolate the parasitological prevalence rate on the basis of the reagent stick testing, or the reverse. A review of the available literature indicated that the relationship holds true for certain settings, mainly in East Africa, but not for others, and it is therefore likely to be setting-specific. The same data demonstrated also a good relationship, at school level, between the mean school parasitological intensity and the sensitivity of the reagent sticks. A comparative testing of two different reagent stick brands (Hemastix and Combur 9) on 320 samples showed that the latter detected about 1.2-times more haematuria positives, and that this had also to be taken into account when aiming for a comparison of different techniques.

Simple school questionnaires can map both Schistosoma mansoni and Schistosoma haematobium in the Democratic Republic of Congo.

The use of self-administered questionnaires has been shown in different African countries to be inexpensive and reliable for the rapid identification of communities at highest risk of urinary schistosomiasis. For intestinal schistosomiasis due to Schistosoma mansoni there is a clear need for a similar approach. We report the results from a large-scale study undertaken in the western part of the Democratic Republic of Congo (DRC, formerly Zaire). Within 4 weeks questionnaires were correctly completed in 136 out of 160 schools (85%). In 57 of these schools children were screened for infections with schistosomes and geohelminths. The prevalence of 'schistosomiasis' as reported in the questionnaires showed the best correlation with the prevalence of S. mansoni infections (r = 0.77, P < 0.0001). Calculations of the diagnostic performance of reported 'schistosomiasis' to detect schools with a high risk of intestinal schistosomiasis gave positive predictive values of 87 and 62%, and negative predictive values of 74 and 87% for moderate and high infection thresholds, respectively. Reported 'blood in stool' was another useful indicator for intestinal schistosomiasis. Reported 'blood in urine' showed the best correlation with urinary schistosomiasis (r = 0.75, P < 0.001) and the positive predictive values were 81 and 50%, and the negative predictive values were 89 and 95% for moderate and high infection thresholds, respectively. We conclude that school children in DRC have a distinct perception of intestinal and urinary schistosomiasis and that questionnaires could be useful to identify high-risk schools for both parasites.

Insecticide-treated bed nets and curtains for preventing malaria.

BACKGROUND: Malaria is an important cause of illness and death in many parts of the world, especially in sub-Saharan Africa. There has been a renewed emphasis on preventive measures at community and individual levels. Insecticide-treated nets (ITNs) are the most prominent malaria preventive measure for large-scale deployment in highly endemic areas. OBJECTIVES: To assess the impact of insecticide-treated bed nets or curtains on mortality, malarial illness (life-threatening and mild), malaria parasitaemia, anaemia, and spleen rates. SEARCH STRATEGY: I searched the Cochrane Infectious Diseases Group trials register (January 2003), CENTRAL (The Cochrane Library, Issue 1, 2003), MEDLINE (1966 to October 2003), EMBASE (1974 to November 2002), LILACS (1982 to January 2003), and reference lists of reviews, books, and trials. I handsearched journals, contacted researchers, funding agencies, and net and insecticide manufacturers. SELECTION CRITERIA: Individual and cluster randomized controlled trials of insecticide-treated bed nets or curtains compared to nets without insecticide or no nets. Trials including only pregnant women were excluded. DATA COLLECTION AND ANALYSIS: The reviewer and two independent assessors reviewed trials for inclusion. The reviewer assessed trial methodological quality and extracted and analysed data. MAIN RESULTS: Fourteen cluster randomized and eight individually randomized controlled trials met the inclusion criteria. Five trials measured child mortality: ITNs provided 17% protective efficacy (PE) compared to no nets (relative rate 0.83, 95% confidence interval (CI) 0.76 to 0.90), and 23% PE compared to untreated nets (relative rate 0.77, 95% CI 0.63 to 0.95). About 5.5 lives (95% CI 3.39 to 7.67) can be saved each year for every 1000 children protected with ITNs. In areas with stable malaria, ITNs reduced the incidence of uncomplicated malarial episodes in areas of stable malaria by 50% compared to no nets, and 39% compared to untreated nets; and in areas of unstable malaria: by 62% for compared to no nets and 43% compared to untreated nets for Plasmodium falciparum episodes, and by 52% compared to no nets and 11% compared to untreated nets for P. vivax episodes. When compared to no nets and in areas of stable malaria, ITNs also had an impact on severe malaria (45% PE, 95% CI 20 to 63), parasite prevalence (13% PE), high parasitaemia (29% PE), splenomegaly (30% PE), and their use improved the average haemoglobin level in children by 1.7% packed cell volume. REVIEWERS' CONCLUSIONS: ITNs are highly effective in reducing childhood mortality and morbidity from malaria. Widespread access to ITNs is currently being advocated by Roll Back Malaria, but universal deployment will require major financial, technical, and operational inputs.

Insecticide-treated bednets and curtains for preventing malaria.

BACKGROUND: Malaria is an important cause of illness and death in many parts of the world, especially in Africa. There has been a renewed emphasis on preventive measures, both at community and at individual level. Insecticide treated bednets and curtains are a promising preventive measure. OBJECTIVES: The objective of this review was to assess the effects of insecticide-treated bednets or curtains in preventing malaria SEARCH STRATEGY: We searched the Cochrane Infectious Diseases Group trials register, Medline, Embase and the reference lists of articles. We handsearched journals, contacted researchers, funding agencies and net and insecticide manufacturers. SELECTION CRITERIA: Randomized and quasi-randomized trials of insecticide-treated bednets or curtains with a sufficient dose of a suitable insecticide compared with nets without insecticide or no nets at all. Studies including pregnant women were excluded. DATA COLLECTION AND ANALYSIS: Trial quality was assessed and data extracted by the reviewer. Trial inclusions/exclusions were reviewed by two independent individuals. MAIN RESULTS: Of 65 identified studies, 18 were included. Of these, 11 were randomized by cluster rather than individually. Mortality in children under five was measured in four trials. When impregnated nets were compared with plain nets or no nets, the summary relative risk was 0. 83. This translates to an estimate of protective efficacy of 17%. For treated nets compared with untreated nets, the relative risk of child mortality was 0.77. About six lives can be saved each year for every 1000 children protected with insecticide-treated nets. Insecticide-treated nets also reduced the incidence of mild malarial episodes by 48% (controls=no nets) and 34% (controls=untreated nets). REVIEWER'S CONCLUSIONS: Insecticide-treated nets appear to be effective in reducing childhood mortality and morbidity from malaria. Widespread access to insecticide-treated nets will require major financial, technical and operational inputs.