Bio-Efficacy of Insecticides Used for Vector Control in Busia and Tororo Districts, Eastern Uganda

Abstract

Reductions in malaria burden worldwide coincides with the massive scale-up of malaria treatment and prevention measures, of which vector control is the major component, particularly in SSA. The key vector control interventions in Africa including Uganda, rely heavily on utilisation of long-lasting insecticidal nets (LLINs) and insecticide-based indoor residual spraying (IRS). This study assessed the bio-efficacy of insecticides used for vector control in LLINs and IRS in Busia and Tororo. Samples of Anopheles mosquito larvae were collected from various breeding grounds before rearing them in an insectary. Emerged adults were observed under a dissecting microscope and identified using standardized morphological keys after respective bioassays on used nets and sprayed walls. Independent two sample T-test was used to test for significant differences in the mean malaria vectors diversity, mean variations, mortalities by net and wall type. Results showed that mean mortalities of Anopheles mosquitoes to used brands of nets from Busia (9.86±11.35) and Tororo (9.64 ±11.12) varied insignificantly (t=0.119, p=0.906). A disaggregated analysis for each net used revealed that, the DAWA plus 2.0 registered a highest mean mortality of mosquitos, followed by PermaNet 3.0+PBO, Olyset and PermaNet 2.0 respectively. Fludora fusion revealed highest mortalities on plastered painted wall, followed by Brick plain then mud/wattle walls at all times. The trend is similar for Actellic, but unlike Fludora fusion, Actellic exhibited mortalities lower than the 80% threshold for all the wall types and T-test (T-test P values<0.001) indicated Actellic efficacy to be significantly lower than that of Fludora fusion on all the three wall substrates. This study has shown that vector behaviour, biology and physiology need consistent monitoring and surveillance for further entomological characterisation.