Variation in the effectiveness of insecticide treated nets against malaria and outdoor biting by vectors in Kilifi, Kenya

Wellcome Open Research

article

Alice Kamau¹  Joseph M. Mwangangi¹  Martin K. Rono¹  Polycarp Mogeni¹  Irene Omedo¹  Janet Midega¹  J. Anthony G. Scott¹  Philip Bejon¹ 

[1] KEMRI-Wellcome Trust Research Programme, Centre for Geographic Medicine Research-Coast;Integrated Vector and Disease Management Cluster, International Centre of Insect Physiology and Ecology;Pwani University Bioscience Research Centre, Pwani University;Centre for Genomics and Global Health, Wellcome Trust Centre for Human Genetics, University of Oxford;Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine;Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford

关键词: ITNs;    outdoor;    Anopheles mosquito;    effectiveness;    Kilifi;    Kenya;    KHDSS;   

DOI  :  10.12688/wellcomeopenres.11073.4

学科分类：内科医学

来源: Wellcome

【 摘 要 】

Background: Insecticide treated nets (ITNs) protect humans against bites from theAnopheles 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.Methods: 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.Results: 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 theAn. funestus group (75%). The overall propensity to feed at times when most people were asleep was high; the vast majority of theAnopheles 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.Conclusion: 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.

【 授权许可】

CC BY