Preliminary Evaluation of Indoor Residual Spraying (IRS) on Malaria Morbidity in Ikorodu Local Government Area (LGA) of Lagos State, Nigeria

The Government of Lagos State prioritized Integrated Vector Management (IVM) to tackle the scourge of malaria. Indoor Residual Spraying (IRS), as a component of IVM was then adopted and it remains  one of the best strategies  to control malaria in endemic areas. IRS refers to the application of  residual   chemical insecticides on the inside of  houses and animal shelters in order to kill the  insecticides that land and rest on the walls and roofs. IRS was first implemented in 2 LGAs (Ojo & Ikorodu) in Lagos State in April 2010. Series of entomological surveys determined the choice of insecticides to use and locations for the IRS exercise.

The objectives of the study were to assess the IVM strategy for malaria control, to assess the impact of IRS strategy and to  identify gaps for future programming and scale-up exercise to other LGAs.

Monthly data from reporting health facilities in Ikorodu LGA were reviewed from 12 months preceding the implementation of IRS (April 2009-March 2010) and 12 months following the implementation (April 2010- March 2010). Data on new malaria cases treated for each month was collated.  Data was summarised using means and paired ‘t’test  to explore the differences in malaria incidence in pre IRS and post IRS periods . Level of significance was set at p<0.05.

The mean incidence of malaria post IRS (3.94 cases/1,000 population/month, SD 1.59) was significantly (t₍₁₁₎ =2.31, p=0.04) less than  the mean incidence pre IRS( 5.76 cases /1000 population/month, S.D 2.49) with  a mean difference of 1.82 (95%CI, 0.84,3.56).

IRS has achieved its goal of reducing morbidities from malaria in  Ikorodu LGA. IRS is still continuing in 6 LGAs (Ojo, Ikorodu, Amuwo/Odofin, Kosofe, Badagry, and Ibeju/Lekki) to prevent resurgence and efforts are being intensified to scale up the IRS exercise to other LGAs within the State.