Influence of Indoor Residual Spay on An. Gambiae S.L. and An. Funestus Abundance, Resting Behavior and Community Perception on Irs Intervention In Kagera-Tanzania

Abstract

Background: There has been a persistence of malaria transmission in Kagera Region despite consecutive phases of indoor residual spraying (IRS) targeting malaria vectors. In addition to that, there is limited information on the resting behaviors of An. gambiae s.l. and An. funestus and community perception on IRS in Kagera. Methods: The study was conducted in two districts; Missenyi and Karagwe. Missenyi was IRS sprayed with Pirimiphos methyl insecticide and Karagwe was unsprayed. Mosquito collections were conducted using bucket traps and CDC (Centre for Disease Control) light traps. Mosquitoes were identified morphologically using taxonomical key. Sibling species were identified by polymerase chain reaction (PCR). Interviews and focused group discussions (FGDs) were conducted in order to obtain information on community perception with regard to IRS interventions. Results: A total of 5,777 mosquitoes were collected indoors by CDC light traps. An. gambiae s.l. and An. funestus accounted for 13% (n=749) of all mosquitoes collected. Unexpectedly, large proportions of An. funestus were collected indoors in Missenyi district, despite the fact that, the area was sprayed. In Karagwe district, An. gambiae s.l. was collected in large proportion. Results have showed that, An. arabiensis was the dominant sibling species among the An. gambiae s.l. in Karagwe and Missenyi districts with 82.8% (n=24) and 98.8% (n=166), respectively. Study participants agreed that, IRS campaign is useful for control of malaria vectors. They also reported that, malaria transmission have declined by comparing before and after IRS. Challenges reported which the IRS campaign poses to them, including the emergence of other insects in their houses and increase of mosquitoes later after IRS. They also reported some mosquito resting places which are not a target during spray operations. Conclusion: The present study has revealed the abundance of malaria vectors and community perception on IRS intervention efficacy and sustainability. Surprisingly, large proportions of An. funestus were collected indoors, despite the fact that, Missenyi district was sprayed. This situation calls for further studies on An. funestus behaviors and possible reasons for tolerance in sprayed area. Community sensitization before, during and after IRS application needs to be strengthen for getting intended results.