1 Tulane University SPHTM, New Orleans, USA.
2 Samburu Aid In Africa, Nanyuki, Kenya.
3 Kenya Medical Research Institute, Mbagathi Way, Nairobi, Kenya.
4 International Centre of Insect Physiology and Ecology, Nairobi, Kenya.
Correspondence: Kate Macintyre, 1440 Canal Street, New Orleans, LA 70112, USA. E-mail: kmacint{at}tulane.edu
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Abstract |
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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 5 years of age results were imprecise with no clear benefit of the intervention.
Conclusions These results suggest that permethrin-impregnated bedsheets may be protective against malaria prevention but further studies with greater power are required to confirm this.
Accepted 4 October 2002
Malaria is an important public health problem in Africa.14 The International Campaign to Roll Back Malaria promotes use of insecticide-treated materials, emphasizing bednets and curtains in particular.2,5 However, the cost of bednets and regular insecticide re-impregnation is prohibitive for some communities,6,7 and for some groups nets or curtains are not compatible with local housing construction or lifestyles. Although other materials and repellent combinations have been experimented with,8,9 the need remains for innovative interventions that make use of effective prevention methods to decrease cost and overcome acceptability barriers to the poorest, most marginalized sectors of society.
This study reports results of a trial to evaluate whether treating personal clothing/sheets worn by nomads is protective against malaria infection. The aim was to test the efficacy of an inexpensive, non-toxic, and locally appropriate strategy. The intervention employed insecticide-impregnated bedsheets, or shukas. A shuka is a 6 by 4 sheet (smaller for children) of varying material that doubles as a wrap during the day and a sheet at night. Nearly all Samburu own at least one shuka.
The impetus for this study occurred during a malaria epidemic in 19971998 in Samburu district, north Kenya, following El Nino rains.10 During the epidemic communities dipped their shukas in permethrin. This approach to malaria prevention cleverly adapted two well-known protection techniques: bednet and clothing impregnation. The effectiveness of insecticide-treated bednets has been demonstrated in a variety of settings.1114 The use of insecticide-impregnated uniforms by military personnel dates back to at least World War II.15 We were interested to see whether impregnated shukas were effective in malaria prevention.
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Data and Methods |
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Study design
Permethrin was selected for this intervention, because it has been extensively tested, is used by military personnel throughout the world18 and is considered the insecticide of choice for clothing treatment.19 Also, permethrin-based creams for child and neonate scabies and lice are widely used.2022
A community randomized study design was used to test the efficacy of the intervention. Randomization was at the level of the manyatta and approval to carry out the study was received from community elders. The sampling frame was constructed using the sole criterion that eligible manyattas be located within a 2-hour walk of the Ngilai health clinic. This represents the clinics proximate catchment area and totalled 84 manyattas. Village records suggested the average manyatta size was 13 people. A minimum sample size of 440 (220 experimental and 220 control participants) was calculated using a confidence level of 95%, power of 80%, an estimate of 20% malaria parasitaemia in the control group, and a least extreme detectable difference of 10% among experimental group members. The estimated prevalence of malaria parasitaemia was based upon clinic reports that suggested a prevalence of 50% during the rainy season. Since this estimate was not based on blood samples we used a more conservative estimate of 20% to calculate the sample size. Of the 84 manyattas, 36 were randomly selected and allocated to the control or experimental groups so that each arm of the study contained 18. Of the original 36 manyattas selected, one elder refused (on behalf of his whole manyatta) to be involved in the study. A substitute manyatta was randomly selected. Informed consent was obtained from all adults and parental consent for all children in the study. A total of 472 people were enrolled: 234 and 238 in the experimental and control arms, respectively.
Appropriate doses of sulphadoxine-pyrimethamine (Fansidar) were given to all members of the study at baseline. Shukas were dipped at baseline and an attempt was made to impregnate all shukas owned by the experimental group. Active case detection to measure parasitaemia took place at 2-week intervals over 4 months. Blood smears were collected, analysed in the field according to standard, quality-controlled procedures, and slides then taken to Nairobi for verification by KEMRI technicians. The lab technicians were blinded to the identity of the blood slides. A malaria case was defined as presence of asexual Plasmodium falciparum parasitaemia at any density.
Efficacy was assessed by comparing the incidence density rates (IDR) of the experimental and control groups while controlling for the clustering effect of manyatta randomization (analysis done using Stata 7.0). An incident case was defined as an individuals first episode of parasitaemia.
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Results |
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Discussion |
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An attempt was made to impregnate all shukas of the experimental group. However, some children refused to have their shukas dipped in the cold early morning hours as it was their only clothing. Other children, one-third of the 5 and unders in both groups owned no shuka. The researchers had been aware of this prior to the study but had felt that this should not affect results since preliminary research indicated that children without shukas slept under their mothers shuka at night. Of the four cases that occurred in the intervention group, three did not own their own shuka and the fourth owned a shuka that was not impregnated.
In summary, this study has some interesting and potentially exciting results. These findings justify further research in this area.
KEY MESSAGES
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Acknowledgments |
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The Thrasher Research Fund funded this study. The authors gratefully acknowledge the support and contribution from the communities in Ngilai, Samburu District. We wish to particularly thank our research collaborators from Samburu Aid in Africa (SAIDIA), Tara Fitzgerald, Eleanor Monbiot, Gabriel Leisiano, Patrick Lolokuria, Julius Mwendwa, Francis Lomoru, Robert Lentaano, Daniel Lenangetai, William Leajore, Sammy Lentukunye, in addition to Daniel Kariuki, Stephen Kaniaru, Gabriel Nzai Karisa, and Jonathan Mwangi, from Kenya Medical Research Institute (KEMRI). Permethrin was generously provided by Coulston Products Inc.
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References |
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