Effect of indoor residual spraying on malaria incidence rate in selected prison facilities of Uganda

Abstract

Background: Indoor residual spraying (IRS) is a powerful intervention for reducing adult mosquito vector density and reducing malaria transmission. Uganda Prison Services (UPS) had been implementing IRS in some facilities for some time but the malaria prevalence among prisoners was still as high as 20.6% in the Northern region, 10.8% in the central region and 8.5% in the East central and yet IRS program was expected to significantly reduce the malaria burden in those facilities. In addition, the effect of the IRS program on malaria incidence rates had not yet been evaluated. Therefore, the aim of the study was to determine the effect of IRS on malaria incidence rates in selected prison facilities in Uganda and describe the IRS program considering the unique context of prisons. Methods: This was a comparative cross-sectional design with retrospective review of records and utilized mixed methods approaches for data collection. Qualitative data were generated using in-depth interviews (IDI) from 10 purposively selected participants using IDI guide. All (210) monthly malaria reports for the period of five years (2018 to 2022) for the intervention (2) and comparison (2) prison facilities located in central and northern regions of Uganda were reviewed using a data abstraction guide. Thematic content analysis was used to analyze the qualitative data. Malaria incidence rate trends were generated using Microsoft Excel software while interrupted time series analysis was conducted to determine IRS effect on malaria incidence rate. Results: The UPS IRS program was well structured and required resources such as trained human resources, IRS equipment, incentives, IRS consumables, IRS guiding documents, and waste management resources for efficient implementation. However, the program faced a number of challenges including inadequate and unreliable access to key IRS resources, welfare challenges and limited technical skills of the IRS teams. The malaria incidence trends were at lower levels among the intervention facilities compared with the comparison facilities across the entire study period regardless of the region. The difference in the post IRS intervention slope and level of monthly malaria incidence per 1000 population between intervention and comparison facilities (central region) was not statistically significant (slope: (P = 0.154, CI = [-76.5, 12.9]); level: P = 0.504, CI = [-118.1, 233.0]). The difference between intervention and comparison facilities (northern region) in the slope of the trend of monthly malaria incidence per 1000 population post IRS compared with the pre IRS period was statistically significant (P = 0.001, CI = [21.9, 67.7]). Conclusion: The evaluated IRS intervention was able to reduce the monthly malaria incidence per 1000 population among the intervention facility located in northern Uganda but not significantly in the intervention facility located in central Uganda. IRS intervention facilities had consistently lower malaria incidence rates throughout the study period and across regions. Recommendation: UPS should consider strengthening the IRS program through timely and adequate provision of IRS resources, capacity development of IRS teams, improve IRS supervision, build internal capacity to conduct entomological surveys to monitor insecticide resistance and promote rational use of insecticides. To strategically improve the malaria control efforts within the study areas, the study recommends IRS implementation before the onset of the peak seasons of malaria incidence rates particularly in the months of September and March. The study further recommends that UPS considers extending the IRS program to all the prisons especially those located in regions of high malaria transmission of Uganda where the program has proved to significantly reduce malaria incidence rates.