Effectiveness of combined use of non pyrethroid indoor residual spray and longlasting insecticidal nets and their acceptability among the residents of Western Kenya

Abstract

Background: Kenya employed combination of long lasting insecticidal nets (LLINs) and non-pyrethroid indoor residual spray (IRS) in 2017 and 2018 as a strategy to address the widespread pyrethroid resistance which is threatening to affect the progress towards malaria elimination. Objectives: To evaluate the effectiveness of combined use of non-pyrethroid IRS and LLINs on malaria indicators and assess awareness and acceptability of the two interventions among the residents of Nyatike and Suba sub-Counties in Western Kenya. Methods: Record review and tally of monthly aggregates of outpatient attendance, suspected malaria cases and number tested for malaria and number positive for malaria at Karungu Sub-county Hospital in Nyatike (intervention area) and Suba Sub-county Hospital in Suba (comparison area) was done for pre-intervention (1 February 2016 to 31 January 2017) and post-intervention periods (1 April 2017 to 31 March 2018). Interviews and screening for malaria was done among febrile clients at outpatient departments of the two health facilities. Data analyses were done using Epi Info 7 and Stata. Poisson regression was used to determine the effectiveness of the intervention in the presence of confounders. Descriptive statistics was used to evaluate awareness and level of acceptability for LLINs and IRS by the residents. Results: Annual malaria incidences among all ages reduced by 89% from 360 per 1000 in pre-intervention to 38 per 1000 in post-intervention in intervention area and reduced by 52% from 131 per 1000 to 78 per 1000 in the comparison area. Among the under 5 children, the net change in annual malaria incidence was 308 per 1000 population (RR=0.25, 95CI 0.24-0.29 p<0.001).Test positivity rate among the febrile clients was 8% (15/187) and 12% (22/187) in Nyatike and Suba sub-Counties respectively. The majority of the clients had heard about free mass net distribution and IRS campaigns. The level of acceptability for LLINs was 94% in Nyatike and 93% in Suba while the level of acceptability for IRS was 61% in Nyatike and 65% in Suba. Conclusion: Combination of non-pyrethroid IRS and LLINs provided greater protection against malaria. The TPR was lower in Nyatike than in Suba sub-County. The level of awareness was high for both LLINs and IRS. The level of acceptability was high for LLINs but considerably lower for IRS in both sub-counties. Recommendations: Scale up of combined use of LLINs and non-pyrethroid IRS in all malaria endemic areas and address factors contributing to low acceptability for IRS through adequate community sensitization and health education