**Abstract**

Entomological inoculation rate (EIR) is a method to estimate the level of human exposure to infective mosquito bites and assess impacts of vector control measures. The objective is to assess the effect of indoor residual spray (IRS) on blood meal index (BMI), sporozoite infection rate (SR), and EIR in *An. arabiensis* under local ecological settings in Ethiopia. A total 1541 fresh fed (FF) female *An. arabiensis* collected by CDC light trap and PSC were processed at the Center for Disease Control and Prevention Laboratory, Atlanta, Georgia, USA, to determine their BMI and SR, using enzyme-linked immunosorbent assay (ELISA). IRS reduced the abundance of FF female *An. arabiensis* in sprayed villages (n=62) while the number remained high in non-sprayed villages (n=1,690). The relative adjusted reduction in human blood feeding index (HBI) due to IRS varied between 3 and 10% except in 2014 when no human blood was detected in any of the three mosquitoes tested. The relative adjusted reduction in *P. falciparum* infection and EIR in *An. arabiensis* was 100% after IRS. The results illustrated that IRS was strong enough to reduce EIR in *An. arabiensis*. IRS is recommended to control malaria transmission in areas of similar ecological set.

**Keywords:** *A. arabiensis*, Ethiopia, EIR, IRS, vector control
