Community-Wide Effects of Permethrin-Treated Bed Nets on Child Mortality and Malaria Morbidity in Western Kenya

Abstract

Spatial analyses of the effect of insecticide (permethrin)-treated bed nets (ITNs) on nearby households both with and without ITNs was performed in the context of a large-scale, group-randomized, controlled mortality trial in Asembo, western Kenya. Results illustrate a protective effect of ITNs on compounds lacking ITNs located within 300 meters of compounds with ITNs for child mortality, moderate anemia, high-density parasitemia, and hemoglobin levels. This community effect on nearby compounds without nets is approximately as strong as the effect observed within villages with ITNs. This implies that in areas with intense malaria transmission with high ITN coverage, the primary effect of insecticide-treated nets is via area-wide effects on the mosquito population and not, as commonly supposed, by simple imposition of a physical barrier protecting individuals from biting. The strength of the community effect depended upon the proportion of nearby compounds with treated nets. To maximize their public health impact, high coverage with treated nets is essential.

Impact of a Spatial Repellent on Malaria Incidence in Two Villages in Sumba, Indonesia

“…Such evidence of human health impact is a fundamental and essential component in the critical path of development of any vector control tool, [38][39][40][41] especially new paradigms such as SR. 4 If the crude estimate of protective efficacy shown here, about 52%, is verified in statistically robust cluster-randomized trials, this instrument of control would likely approximate that benefit associated with LLINs. 42 It is important to note this study was not intended to assess a practical method of delivery of a spatial repellent product in malaria control.…”

Prevalence and Severity of Malnutrition in Pre-School Children in a Rural Area of Western Kenya

“…10,23 Although children living in intervention villages were excluded from these latter two surveys, bed nets were also found to exert a mass or community effect, resulting in marked reductions in mosquito populations, symptomatic malaria, and severe malarial anemia in control households located within 300 meters of bed net villages. 24 Despite a clear effect on malaria-specific parameters, there was no evidence for a community effect on any of the standard nutritional parameters (Hawley WA and others, unpublished data). Thus, although a small community effect cannot be excluded, it is unlikely that that this will have resulted in a substantial underestimation of the prevalence of malnutrition in this analysis.…”

Free Distribution or Cost-Sharing? Evidence from a Randomized Malaria Prevention Experiment

“…13,14 In a randomized trial of an ITN distribution program at the village level in Western Kenya, the positive impacts of ITN distribution on child mortality, anemia and malaria infection were as strong among non-beneficiary households within 300 meters of beneficiary villages as they were among households in the beneficiary villages themselves (Gimnig et al, 2003;Hawley et al, 2003). 15 While ITNs may have positive externalities at low levels of coverage (e.g.…”

“…Western Kenya imply that "in areas with intense malaria transmission with high ITN coverage, the primary effect of insecticide-treated nets is via area-wide effects on the mosquito population and not, as commonly supposed, by simple imposition of a physical barrier protecting individuals from biting" (Hawley et al, 2003). In this context, we propose the following methodology to measure the health impact of each ITN pricing scheme: we create a "protection index for non-users" (a logistic function of the share of users in the total population) and a "protection index for users" (a weighted sum of a "physical barrier" effect of the ITN and the externality effect, the weights depending on the share of users).…”