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. 2017 Jan 17;16(1):32.
doi: 10.1186/s12936-017-1686-2.

Insecticide-treated net effectiveness at preventing Plasmodium falciparum infection varies by age and season

Andrea G Buchwald  1 , Jenna E Coalson  2 , Lauren M Cohee  1 , Jenny A Walldorf  1 , Nelson Chimbiya  3 , Andy Bauleni  3 , Kondwani Nkanaunena  3 , Andrew Ngwira  3 , John D Sorkin  1 , Don P Mathanga  3 , Terrie E Taylor  4 , Miriam K Laufer  5
Affiliations

Insecticide-treated net effectiveness at preventing Plasmodium falciparum infection varies by age and season

Andrea G Buchwald et al. Malar J. .

Abstract

Background: After increasing coverage of malaria interventions, malaria prevalence remains high in Malawi. Previous studies focus on the impact of malaria interventions among children under 5 years old. However, in Malawi, the prevalence of infection is highest in school-aged children (SAC), ages 5 to 15 years. This study examined the interaction between age group and insecticide-treated net (ITN) use for preventing individual and community-level infection in Malawi.

Methods: Six cross-sectional surveys were conducted in the rainy and dry seasons in southern Malawi from 2012 to 2014. Data were collected on household ITN usage and demographics. Blood samples for detection of Plasmodium falciparum infection were obtained from all household members present and over 6 months of age. Generalized linear mixed models were used to account for clustering at the household and community level.

Results: There were 17,538 observations from six surveys. The association between ITN use and infection varied by season in SAC, but not in other age groups. The adjusted odds ratio (OR) for infection comparing ITN users to non-users among SAC in the rainy season and dry season was 0.78 (95% CI 0.56, 1.10) and 0.51 (0.35, 0.74), respectively. The effect of ITN use did not differ between children under five and adults. Among all non-SACs the OR for infection was 0.78 (0.64, 0.95) in those who used ITNs compared to those that did not. Community net use did not protect against infection.

Conclusions: Protection against infection with ITN use varies by age group and season. Individual estimates of protection are moderate and a community-level effect was not detected. Additional interventions to decrease malaria prevalence are needed in Malawi.

Keywords: Insecticide-treated nets; Malawi; Plasmodium falciparum; School-aged children; Universal distribution campaign.

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Figures

Fig. 1
Fig. 1
Net use and infection prevalence (PCR) by age and by survey. Vertical line indicates the timing of universal net distribution in Malawi
Fig. 2
Fig. 2
Adjusted odds ratios for infection comparing ITN users to non-users by strata. Diamonds indicate strata-specific odds ratio estimate. Red horizontal bars indicate 95% confidence intervals. Grey vertical line at 1 indicates an odds ratio of 1, or no difference between ITN users and non-users
See this image and copyright information in PMC

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