The additional effect of focal indoor residual spraying on incidence of malaria in a setting with high insecticide treated bed net coverage in Mansa District, Luapula Province

Abstract

Malaria is a leading cause of morbidity and mortality especially in children under 5 years and pregnant women in Zambia. Environmental factors and behavioral patterns of vectors and human populations combine to provide favorable conditions for malaria transmission. Focal-Indoor Residual Spraying (IRS) was first conducted in Zambia’s Luapula Province in 2014 in areas with high burden of malaria. A quasi experimental study design comparing incidence of malaria pre and post-IRS intervention was used. Malaria is diagnosed by use of rapid diagnostic test or microscopically. Malaria incidence was calculated based on extrapolated census data for health centres. We extracted malaria morbidity data from the Health Management Information System from 2013 to 2015. There was no physical contact with participants as only secondary data were used. Epi-Info version 7 was used to analyze the data. Associations between variables were tested using a Chisquare with the level of statistical significance set at desired accuracy of 5% and 95% confidence interval. A total of 11 of 25 (44%) health facility catchment areas conducted focal-IRS in 2014 in addition to Insecticide Treated bed Nets (ITNs) use. Six of 11 (55%) IRS health facility catchment areas recorded spray coverage of above 85%. Of the 11 IRS health facility catchment areas, 5 (45%) recorded decrease in incidence of total malaria (clinical and confirmed) in 2015 compared to 2013 whilst 6 (55%) recorded increased incidence post spraying. About 5 of 14 (36%) ITN only health facility catchment areas recorded decrease in incidence of total malaria in 2015 compared to 2013. Only 1 of 11(9%) IRS-health facility catchment areas (Muwanguni RHC) recorded decrease in incidence of lab-confirmed malaria while 91% recorded increase in 2015 compared to 2013. Use of focal IRS strategy in addition to ITNs in Mansa district did not yield additional effect compared to use of ITNs only. This strategy needs to be redesigned to ensure that questions of its efficacy and operationalization are well understood before scale-up of the concept is enhanced. Keywords: Malaria; Incidence; focal indoor residual spraying; insecticide treated net.