Abstract
BackgroundControl measures which reduce individual exposure to malaria are expected to reduce disease, but also to eventually reduce immunity. Reassuringly, long term data following community wide ITN distribution show sustained benefits at a population level. However, the more common practice in Sub-Saharan Africa is to target ITN distribution on young children. There are few data on the long term outcomes of this practice.Methodology/Principal FindingsEpisodes of febrile malaria were identified by active surveillance in 383 children over 18 months of follow up. In order to compare the short and long term outcomes of ITN use, we examined interactions between ITN use and age (12–42 months of age versus 42–80 months) in determining the risk of febrile malaria. ITN use and older age protected against the first or only episode of malaria (Hazard Ratio [HR] = 0.33, 95%CI 0.17–0.65 and HR = 0.30, 95%CI 0.17–0.51, respectively). The interaction term between ITN use and older age was HR = 2.91, 95%CI 1.02–8.3, p = 0.045, indicating that ITNs did not protect older children. When multiple episodes were included in analysis, ITN use and older age were again protective against malaria episodes (Incident Rate Ratio [IRR] = 0.43 95%CI 0.27–0.7) and IRR = 0.23, 95%CI 0.13–0.42, respectively) and the interaction term indicated that ITNs did not protect older children (IRR = 2.71, 95%CI 1.3–5.7, p = 0.008).Conclusions/SignificanceThese data on age interactions with ITN use suggest that larger scale studies on the long term individual outcomes should be undertaken if the policy of targeted ITN use for vulnerable groups is to continue.
Highlights
Malaria is a global public health problem
There were 355 children with data on insecticide treated nets (ITNs) use. 102 children slept under an ITN, 253 did not. 18 children had nets with more than 3 holes, and 2 had nets with more than 6 holes. 74 children acquired an ITN during the 18 months of follow up, and 7 children had ITNs that developed more than 3 holes over the 18 months. 6 children lost the use of an ITN during the study. 236 episodes of febrile malaria were reported
ITNs were protective, but in older children there was a tendency for more febrile malaria with ITN use (Figure 1)
Summary
Malaria is a global public health problem. There were over 500 million episodes globally in 2002, and over a million deaths in Africa [1,2]. The current practice in most malaria endemic countries is to target vulnerable groups in distribution programmes, and this policy may not yield the same long term results since community-wide ITN use reduces mosquito survival and infectivity [12], reducing overall transmission [13,14,15]. These reductions in transmission may offset reductions in immunity, explaining the sustained benefits of ITN use [16]. There are few data on the long term outcomes of this practice
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