Malaria burden remains one of the major public health challenges in sub-Saharan Africa, Uganda inclusive. Uganda has the 3rd highest global disease cases estimated to be 225 million and the 8th highest level of deaths equivalent to 781,000 per year. Malaria remains a leading cause of morbidity and mortality in Uganda, accounting for 30-50% of outpatient visits at health facilities, 15-20% of all hospital admissions, and up to 20% of all hospital deaths with at least 27.2% of inpatient deaths among children under five years of age. Widely recommended Plasmodium vector control approaches include utilization of long-lasting insecticidal nets and indoor residual sprays which are insecticide-based. This study assessed a nine-year period malaria cases data (2012-2020) obtained from the health management database to depict malaria spatial and temporal patterns in Busia and Tororo districts pre and post-vector control interventions. The routine malaria surveillance data reported passively through public and high-volume private health facilities were entered and manipulated into MS Excel. This was done separately for each of the 9 years. Considering the malaria cases registered on annual basis, Mann- Kendal test revealed a drastic decline of malaria cases over the nine-year period (2012 -2020) in Tororo district with Sen’s slope of -22, while for Busia district it revealed an increase of malaria cases (Sen’s slope +28). Equally, these trends reveal varied spatial patterns over the two districts. Both Busia and Tororo revealed a high prevalence of malaria between May-November in respect to bimodal rainfall pattern, matching with the perennial transmission setting of Uganda. This study has shown that, for further epidemiological characterization, vector behavior, biology and physiology need consistent monitoring and surveillance while implementing new vector control interventions targeting outdoor biting Plasmodium vectors.

This study assessed the susceptibility of Anopheles mosquitoes to LLINs and IRS as vector control interventions used in Tororo and Busia district. Samples of Anopheles mosquito larvae were collected from various breeding grounds and reared in an insectary. Emerged adults were dissected under a stereoscopic microscope and identified using standardized morphological keys after respective bioassays on used LLINs and sprayed walls. A One-Way Analysis of Variance (ANOVA) was used to test for significant differences in the mean composition of mosquito species across the study area, mean variations, mortalities by net and wall type. Results showed that the Anopheles gambiae sensu lato revealed a higher mean of 78.33 ± 41.52, compared to Anopheles funestus (16.42 ± 24.87) which was lonely found in Busia district. Out of four brands of nets tested for insecticides susceptibility, 99% mortality was recorded for the insecticide concentration of 80 mg/m2 deltamethrin impregnated DAWA plus 2.0 nets. PermaNet 3.0 and Olyset recorded mortality rate of 95% and 93% at chemical concentrations of 50 mg/m2 and 525 mg/m2 permethrin respectively. PermaNet 2.0 recorded 67% mortality at 55 mg/m2 permethrin. The average number of Anopheles mosquitoes were more susceptible to 12.5 mg/m2 of Fludora fusion impregnated onto plastered painted walls at a rate of 100% as compared to the other types of walls after 2 weeks (6.86 ± 4.07) and 1 month of chemical spray (6.69 ± 4.01) varied insignificantly (t = 0.175, P = 0.861). Meanwhile, a disaggregated results by time of spray (T0 and T1) and exposure periods, showed that plastered painted wall, had higher mortalities followed by Brick Plain and Mud/Wattle wall substrates, respectively. This study has shown that vector behavior, biology and physiology need consistent monitoring and surveillance for further entomological characterization and the need for coming up with new vector control interventions.