Reduction of malaria during pregnancy by permethrin-treated bed nets in an area of intense perennial malaria transmission in western Kenya. Effect of insecticide-treated bed nets on haemoglobin values, prevalence and multiplicity of infection with Plasmodium falciparum in a randomized controlled trial in Tanzania. A community randomized controlled trial of insecticide-treated bednets for the prevention of malaria and anaemia among primigravid women on the Kenyan coast. The impact of insecticide-treated bednets on malaria and anaemia in pregnancy in Kassena-Nankana district, Ghana: a randomized controlled trial.
The impact of insecticide (permethrin)-treated bed nets (ITNs) on malaria in pregnancy was studied in a rural area in western Kenya with intense perennial malaria transmission. All households in 40 of 79 villages were randomized to receive ITNs by January 1997. The ITNs were distributed in control villages two years later. Complete data on birth outcome were available on 2,754 (89.6%) of 3,072 deliveries. Women (n = 780) were followed monthly throughout pregnancy in 19 of 79 villages. Among gravidae 1-4, ITNs were associated with reductions of 38% (95% confidence interval [CI] = 17-54%) in the incidence of malaria parasitemia and 47% (95% CI = 6-71%) in the incidence of severe malarial anemia (hemoglobin level < 8 g/dL with parasitemia) during pregnancy. At the time of delivery, mean hemoglobin levels were 0.6 g/dL (95% CI = 0.01-1.2 g/dL) higher, the prevalence of placental or maternal malaria was reduced by 35% (95% CI = 20-47%), and the prevalence of low birth weight was reduced by 28% (95% CI = 2-47%) in gravidae 1-4 from ITN villages. No beneficial impact was observed in gravidae five or higher. In areas of intense perennial malaria transmission, permethrin-treated bed nets reduce the adverse effect of malaria during the first four pregnancies. A randomized controlled trial of insecticide-treated bed nets (ITNs) was conducted in an area of high malaria transmission in Tanzania in order to assess the effects of ITNs on infection and anaemia. One hundred and twenty-two children, aged 5 to 24 months, were randomly allocated to 2 groups, one of which received ITNs. Outcome measures were assessed in 6 consecutive months with monthly cross-sectional surveys. These measures were haemoglobin values, Plasmodium falciparum prevalence and density, and multiplicity of infection determined by polymerase chain reaction-restriction fragment length polymorphism analysis (PCR-RFLP) of the msp2 locus. There was a significant increase in mean heamoglobin values and a significant decrease of 16.4% in microscopically determined P. falciparum prevalence in children in the ITN group six months after the start of the trial. Both effects were more pronounced in younger children. However, no significant difference was observed in parasite density or multiplicity of infection among infected children. Comparison with PCR results indicated that microscopically subpatent parasitaemia was more frequently found in children in the ITN group. This, together with the observed similar multiplicity in the 2 groups, suggests that infections are maintained despite ITN use, owing to the chronicity of infections. This study shows that ITNs reduce the risk of anaemia in highly exposed young children. The virtually unchanged multiplicity of infection indicates that the potentially protective concomitant immunity is not compromised. The effectiveness of insecticide-treated bednets (ITBN) in preventing malaria and anaemia among primigravidae living in Kilifi District, Kenya, was assessed by a randomized controlled trial between September 1994 and November 1995. All residents within 28 community clusters received ITBN in July 1993, whilst residents of another 28 clusters served as contemporaneous controls. All resident primigravid women with singleton pregnancies attending antenatal care at Kilifi District Hospital were eligible for recruitment. 503 primigravidae were recruited. 91.4% were anaemic antenatally (Hb < 11 g/dl): 91.0% from the intervention arm and 92.0% from the control arm. Severe anaemia (Hb < 7 g/dl) was found among 15.1% of intervention women and 20.1% of control women (P = 0.28). No significant differences were observed in reports of febrile illness or the presence of chloroquine in the serum or peripheral parasitaemia during the third trimester between the two groups. In the women delivering in hospital (n = 130), there was no association between placental malaria infection and the intervention: 77.4% of placentas from control women had evidence of past or active infection, compared with 72.0% of placentas from intervention women (P = 0.76). Similarly, in the women delivering in hospital, ITBN did not improve birth weight, and there were no differences in perinatal mortality between the two study groups. Despite ITBN having a great impact on paediatric severe malaria and mortality in this transmission setting, there was very little impact of ITBN on the morbidity associated with malaria infection in primigravidae. Alternative strategies are required to tackle this continued public health problem for pregnant women living in endemic areas similar to the Kenyan Coast. The impact of insecticide-treated bednet use on malaria and anaemia in pregnancy was assessed, as a supplementary study, in a major WHO/TDR-supported bednet trial in northern Ghana between July 1994 and April 1995. The study area was divided into 96 clusters of compounds, with 48 clusters being randomly allocated to intervention. All pregnant women were included in the study but the focus was on primigravidae and secundigravidae. 1961 pregnant women were recruited into the study--1033 (52.7%) in the treated bednet group and 928 (47.3%) in the no net group. 1806 (92.1%) had blood taken for malaria microscopy and haemoglobin determination in the third trimester. Pregnancy outcomes were reported for 847 women. The characteristics of women in intervention and control groups were comparable. The odds ratios, with 95% confidence interval (CI), for different study endpoints were, for Plasmodium falciparum parasitaemia--0.89 (0.73, 1.08), for anaemia--0.88 (0.70, 1.09), for low birthweight (LBW)--0.87 (0.63, 1.19), indicating no benefit for treated bednet use. Effective net use by parity varied from 42% in primigravidae to 63% in multigravidae, in spite of free nets and insecticide impregnation. The main reasons for not using a net were warm weather and perceived absence of mosquito biting. Chloroquine use in pregnancy was low and comparable in both groups. Implications of findings for malaria control in pregnancy and further research are discussed.
ITNs have a beneficial impact on pregnancy outcome in malaria-endemic regions of Africa when used by communities or by individual women. No further trials of ITNs in pregnancy are required in sub-Saharan Africa. Further evaluation of the potential impact of ITNs is required in areas with less intense and Plasmodium vivax transmission in Asia and Latin America.