Evaluation of the Effect of Indoor Residual Spraying on Malaria Morbidity Trends the Gusheigu and Karaga Districts of Northern Region, Ghana

Abstract

Background Malaria is endemic in Ghana with pronounced seasonal variations in the northern parts. Several efforts have been made to control malaria in Ghana including implementation of indoor residual spraying (IRS). This study assessed the effect of IRS reintroduction on malaria morbidity trends in the Karaga and Gusheigu districts in the midst of other interventions. Method A controlled Interrupted Time Series Analysis (itsa) design was used for the study. Routine data on monthly suspected and monthly confirmed cases of malaria were retrieved from the National Malaria Control Programme (NMCP). Data span a four year period (2015-2018). The outcome variable is test positivity rate (TPR), calculated as a percentage proportion of confirmed malaria cases out of the number tested in a month. The exposure variable is time (categorized into pre-implementation and post-implementation segments). Line graphs of TPR were plotted to show seasonal trends of malaria in the districts. Segmented regression was used to estimate the immediate and temporal changes in TPR following IRS implementation. Yendi and Tolon districts were used as controls. A change in TPR is considered significant if p-value is less than 0.05 Results The study revealed that monthly TPR in the Gusheigu and Karaga districts followed seasonal patterns with peaks between July and October each year, and decreasing trends between November of a particular year and February of the ensuing year. Following the first and second rounds of IRS in the Gusheigu district, there appeared to be immediate decreases in TPR of 13.9% and 23.7% respectively. In the Karaga district, there was a reduction in TPR of 5.2% and 12.7% following the first and second cycles of spraying respectively. Conclusion There was an immediate decrease in malaria TPR following the first and second rounds of IRS in the Gusheigu and Karaga districts. The magnitude of decrement was greater in the second round of IRS than the first. Also, the decrease following the second cycle was sustained with an average of two percentage point reduction in monthly malaria TPR. Recommendation Based on the positive indications of IRS intervention revealed by this study, it is recommended that the NMCP and its partners sustain the intervention in these districts so as to maximize the benefits thereof.