Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

<ns4:p><ns4:bold>Background</ns4:bold>: Insecticide treated nets (ITNs) protect humans against bites from the <ns4:italic>Anopheles </ns4:italic>mosquito vectors that transmit malaria, thereby reducing malaria morbidity and mortality. It has been noted that ITN use leads to a switch from indoor to outdoor feeding among these vectors. It might be expected that outdoor feeding would undermine the effectiveness of ITNs that target indoors vectors, but data are limited.</ns4:p><ns4:p> <ns4:bold>Methods</ns4:bold>: We linked homestead level geospatial data to clinical surveillance data at a primary healthcare facility in Kilifi County in order to map geographical heterogeneity in ITN effectiveness and observed vector feeding behaviour using landing catches and CDC light traps in six selected areas of varying ITN effectiveness. We quantified the interaction between mosquitoes and humans to evaluate whether outdoor vector biting is a potential explanation for the variation in ITN effectiveness.</ns4:p><ns4:p> <ns4:bold>Results</ns4:bold>: We observed 37% and 46% visits associated with positive malaria slides among ITN users and non-ITN-users, respectively; ITN use was associated with 32% protection from malaria (crude OR = 0.68, 95% CI: 0.64, 0.73). We obtained modification of ITN effectiveness by geographical area (p=0.016), and identified 6 hotspots using the spatial scan statistic. Majority of mosquitoes were caught outdoor (60%) and were of the <ns4:italic>An. funestus</ns4:italic> group (75%). The overall propensity to feed at times when most people were asleep was high; the vast majority of the <ns4:italic>Anopheles</ns4:italic> mosquitoes were caught at times when most people are indoors asleep. Estimates for the proportion of human-mosquito contact between the first and last hour when most humans were asleep was consistently high across all locations, ranging from 0.83 to 1.00.</ns4:p><ns4:p> <ns4:bold>Conclusion</ns4:bold>: Our data do not provide evidence of an epidemiological association between microgeographical variations in ITN effectiveness and variations in the microgeographical distribution of outdoor biting.</ns4:p>

Original publication

DOI

10.12688/wellcomeopenres.11073.4

Type

Journal article

Journal

Wellcome Open Research

Publisher

F1000 Research Ltd

Publication Date

03/12/2018

Volume

2

Pages

22 - 22