A health facility based case-control study of effectiveness of insecticide treated nets: potential for selection bias due to pre-treatment with chloroquine.
(73/490)
Case control studies offer an attractive way to assess the effectiveness of insecticide treated nets (ITN) under programme conditions but have the drawback of being susceptible to bias in the choice of controls. We evaluated the potential for pre-treatment with chloroquine to result in misclassification of cases and controls and affect estimates of ITN effectiveness in case control studies in urban and rural clinics in Eastern Afghanistan. During the one-month study, use of ITN showed no effect against malaria in the urban clinic (adjusted odds ratio OR 1.08; 95% CI 0.73-1.6) and the protective effect seen in the rural clinic was not significant (OR 0.62; 95% CI 0.2-2.4). Levels of pre-treatment were high in both clinics: 24% in urban and 19% in rural clinic attenders. In the urban clinic attenders the level of pre-treatment between bed net users and non-users was not significantly different (OR 1.07, 95% CI 0.70-1.64); therefore the misclassification of cases as controls did not introduce any selection bias. Amongst rural clinic attenders, bed net users were less likely to pre-treat with chloroquine than users (OR 0.33, 95% CI 0.14-0.77); this introduced a selection bias that resulted in an underestimation of the effectiveness of bed nets. Case control studies using health facility data are liable to selection bias especially in areas of high pre-treatment rates with chloroquine. Generalisation of results over a wide geographic region, or between urban and rural settings, may not be appropriate. (+info)
A new tool for malaria prevention?: Results of a trial of permethrin-impregnated bedsheets (shukas) in an area of unstable transmission.
(74/490)
BACKGROUND: Despite gains in malaria control through impregnated treated nets (ITN), malaria remains a major concern. Netting is expensive and impractical for many communities. Here we present the findings of a community-based trial of impregnated bedsheets (shukas) in Kenya. METHODS: A total of 472 individuals were enrolled in a randomized community trial where the unit of randomization was the hamlet (manyatta). Baseline data included socio-demographic data, parasite prevalence data from thick and thin blood smears, and clinical measures of malaria. The intervention involved the dipping of shukas owned by the experimental group in permethrin. FINDINGS: The prevalence of malaria in the study population (based on laboratory results) was considerably lower than that used for the power calculation based on clinical estimates (2.2% versus 20%). For those aged 6 or over, the rate of malaria cases (events per 10 000 person-days at risk) was 1.41 in the experimental group versus 7.49 in the control group (incidence rate ratio 0.187, 95% CI: 0.046- 0.770). For children +info)
Effect of bedding control on amount of house dust mite allergens, asthma symptoms, and peak expiratory flow rate.
(75/490)
This quasi-experimental study was designed to investigate the effect of bedding control on the amount of house dust mite (HDM) allergens, asthma symptoms, and peak expiratory flow rate (PEFR) in asthmatics sensitive to HDMs. The subjects in the study were drawn from patients receiving treatment at the allergy clinics of three university-affiliated hospitals in Seoul. Forty-two patients without prior practice of the bedding control used in this study were selected. They commonly showed bronchial asthma caused by HDMs, and exhibited strong positive points (more than 3 points) in skin prick test (D. farinae, D. pteronyssinus), and positive response in both fluoro-allergosorbent test (FAST), and PC20 methacholine test. Of the subjects, alternatively, 22 were assigned to the experimental group and 20 to control group. Bedding control consisted of the use of outer cotton covers, boiling them for 10 minutes fortnightly, and disinfecting bedding by sunlight fortnightly. The experimental group was under bedding control for 4 weeks. The data were collected from October 2000 to January 2001. The results were as follows: 1. After bedding control, the total amount of HDM allergens decreased significantly in the experimental group. However there was no significant difference in the decrease of the amount of HDM allergens between the two groups. 2. Of the asthma symptoms, there was significant difference only in the decrease of the frequency of dyspnea, and in the increase of sleeping disturbance between the two groups after bedding control. 3. After bedding control, PEFR increased in the experimental group whereas it decreased in the control group. However, neither change was significant. The above findings indicate that bedding control improved several asthma symptoms in asthmatics sensitive to HDMs. Accordingly, we suggest that bedding control is adopted as a useful nursing intervention in the field. (+info)
Targeted subsidy for malaria control with treated nets using a discount voucher system in Tanzania.
(76/490)
During the last decade insecticide-treated nets have become a key strategy for malaria control. Social marketing is an appealing tool for getting such nets to poor rural African communities who are most afflicted by malaria. This approach usually involves subsidized prices to make nets and insecticide more affordable and help establish a commercial market. We evaluated a voucher system for targeted subsidy of treated nets in young children and pregnant women in two rural districts of southern Tanzania. Qualitative work involved focus group discussions with community leaders, male and female parents of children under 5 years. In-depth interviews were held with maternal and child health clinic staff and retail agents. Quantitative data were collected through interviewing more than 750 mothers of children under 5 years during a cluster sample survey of child health. The voucher return rate was extremely high at 97% (7720/8000). However, 2 years after the start of the scheme awareness among target groups was only 43% (45/104), and only 12% of women (12/103; 95% CI 4-48%) had used a voucher towards the cost of a net. We found some evidence of increased voucher use among least poor households, compared with the poorest households. On the basis of these results we renewed our information, education and communication (IEC) campaign about vouchers. Discount vouchers are a feasible system for targeted subsidies, although a substantial amount of time and effort may be needed to achieve high awareness and uptake - by which we mean the proportion of eligible women who used the vouchers - among those targeted. Within a poor society, vouchers may not necessarily increase health equity unless they cover a high proportion of the total cost: since some cash is needed when using a voucher as part-payment, poorer women among the target group are likely to have lower uptake than richer women. The vouchers have two important additional functions: strengthening the role of public health services in the context of a social marketing programme and forming an IEC tool to demonstrate the group at most risk of severe malaria. (+info)
The efficacy of permethrin-treated bed nets on child mortality and morbidity in western Kenya I. Development of infrastructure and description of study site.
(77/490)
Randomized controlled trials in sub-Saharan Africa have shown that permethrin-treated bed nets and curtains reduce all-cause child mortality by 15-33% in areas with low or high but seasonal malaria transmission. This report describes the study site for a community-based, group-randomized, controlled trial in an area of high and year-round malaria transmission in western Kenya. We outline the development of the human and physical infrastructure required to conduct this trial and discuss some of the difficulties encountered and lessons learned in conducting it. (+info)
The efficacy of permethrin-treated bed nets on child mortality and morbidity in western Kenya II. Study design and methods.
(78/490)
This paper describes the study design and methods used in a large community-based, group-randomized, controlled trial of permethrin-treated bed nets (ITNs) in an area with intense, perennial malaria transmission in western Kenya conducted between 1996 and 1999. A multi-disciplinary framework was used to explore the efficacy of ITNs in the reduction of all-cause mortality in children less than five years old, the clinical, entomologic, immunologic, and economic impact of ITNs, the social and behavioral determinants of ITN use, and the use of a geographic information system to allow for spatial analyses of these outcomes. Methodologic difficulties encountered in such large-scale field trials are discussed. (+info)
Impact of permethrin-treated bed nets on entomologic indices in an area of intense year-round malaria transmission.
(79/490)
The effect of permethrin-treated bed nets (ITNs) on malaria vectors was studied as part of a large-scale, randomized, controlled trial in western Kenya. Indoor resting densities of fed Anopheles gambiae s.l. and An. funestus in intervention houses were 58.5% (P = 0.010) and 94.5% (P = 0.001) lower, respectively, compared with control houses. The sporozoite infection rate in An. gambiae s.l. was 0.8% in intervention areas compared with 3.4% (P = 0.026) in control areas, while the sporozoite infection rates in An. funestus were not significantly different between the two areas. We estimated the overall transmission of Plasmodium falciparum in intervention areas to be 90% lower than in control areas. Permethrin resistance was not detected during the study period. As measured by densities of An. gambiae s.l., the efficacy of bed nets decreased if one or more residents did not sleep under a net or if bed nets had not been re-treated within six months. These results indicate that ITNs are optimally effective if used every night and if permethrin is reapplied at least biannually. (+info)
Efficacy of permethrin-treated bed nets in the prevention of mortality in young children in an area of high perennial malaria transmission in western Kenya.
(80/490)
A group-randomized controlled trial of insecticide (permethrin)-treated bed nets (ITNs) was conducted in an area of high perennial malaria transmission in western Kenya to test the effect of ITNs on all-cause mortality in children 1-59 months of age. Child deaths were monitored over a two-year period by biannual household census in Asembo (1997-1998) and in Gem (1998-1999). Overall, 1,722 deaths occurred in children 1-59 months followed for 35,932 child-years. Crude mortality rates/1,000 child-years were 51.9 versus 43.9 in control and ITN villages in children 1-59 months old. The protective efficacy (PE) (95% confidence interval) adjusted for age, study year, study site, and season was 16% (6-25%). Corresponding figures in 1-11- and 12-59-month-old children in control and ITN villages were 133.3 versus 102.3, PE = 23% (11-34%) and 31.1 versus 28.7, PE = 7% (-6-19%). The numbers of lives saved/1,000 child-years were 8, 31, and 2 for the groups 1-59, 1-11, and 12-59 months old, respectively. Stratified analysis by time to insecticide re-treatment showed that the PE of ITNs re-treated per study protocol (every six months) was 20% (10-29%), overall and 26% (12-37%) and 14% (-1-26%) in 1-11- and 12-59-month-old children, respectively. ITNs prevent approximately one in four infant deaths in areas of intense perennial malaria transmission, but their efficacy is compromised if re-treatment is delayed beyond six months. (+info)