BackgroundWe investigated the biting patterns and seasonal abundances of Anopheles gambiae s.l. and An. funestus mosquitoes in Kamuli District, Uganda.MethodsHourly indoor and outdoor catches of human biting mosquitoes were sampled from 19.00 to 07.00 hours for four consecutive nights each month using bed net traps in forty-eight houses randomly selected from Bugabula county where insecticide-treated bed nets (ITNs) had been used for at least five years and Budiope county where ITNs had not been used. The indoor and outdoor human-biting fractions, time of biting of the anophelines and climatic data were recorded from January to December 2010. Data were analysed using Multi-way analysis of variance, Kruskal-wallis rank sum test and Pearson correlation. The number of mosquitoes caught biting humans and resting indoors, the indoor and outdoor human biting densities and biting rates during different hours of the night, and mosquito abundances for a twelve-month sampling period in both zones are reported.ResultsApproximately four times more Anopheles mosquitoes were caught biting humans in Budiope County than in the Bugabula zone, with An. gambiae s. l. catches exceeding those of An. funestus. In both zones, peak night biting occurred between 23.00 and 05.00 hours. The majority of bites occurred between 03.00 and 06.00 hours for both Anopheles gambiae s. l. and funestus group. Outdoor biting densities of Anopheles gambiae s. l. exceeded the indoor biting densities throughout the night in both zones, while the indoor and outdoor human biting densities of An. funestus group were apparently equal. The outdoor and indoor human biting rates were similar in both zones. In Bugabula county, the abundance of An. gambiae s.l. was rainfall-dependent, while the An. funestus group could thrive with or without rain fall. In Budiope county, both An. gambiae s.l. and An. funestus mosquitoes thrived all year round regardless of the amount of rainfall.ConclusionConsidering the biting patterns, and seasonal abundances exhibited by Anopheles gambiae s.l. and An. funestus mosquitoes in Kamuli district, intensive use of ITNs combined with indoor residual spraying, environmental management and improved house designs in the context of integrated vector management may be the appropriate vector control strategy.

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.

Anopheles gambiae sensu stricto Giles (formerly A. gambiae S molecular form), the largely anthropophilic species, is reportedly the most important malaria vector in Uganda among the A. gambiae complex species. Indoor and outdoor human-biting mosquitoes were caught for four consecutive nights in each of 48 households in Kamuli district using human-baited bed net traps for subsequent identification of the principal Anopheles sibling species responsible for transmitting malaria. Sibling species under the A. gambiae complex were characterized by polymerase chain reaction using species specific single nucleotide polymorphism (SNPs) in the intergenic spacer region (IGS) with primers specific for A. gambiae s.s., Anopheles arabiensis, Anopheles melas, Anopheles merus and Anopheles quadriannulatus. Molecular forms of the A. gambiae s.s. were further discriminated using primers specific for Mopti and Savannah forms. Out of 300 A. gambiae s.l. amplified, 98% (n= 294) were A. gambiae s.s. Out of 142 A. gambiae s.s. samples analyzed for molecular forms, 78.9% (n=112) were identified as A. gambiae s.s. Giles (A. gambiae Savannah (S) form, while the other 21.1% were not identifiable. the presence of A. gambiae s.s. Giles in Kamuli was also reported. Considering the anthropophilic, endophagic and endophilic behavior of A. gambiae s.s. (and of the molecularly similar A. gambiae s.s. Giles), the combined use of insecticide-treated nets (ITNs), indoor residual spraying, larval source management and improved house design in the context of integrated vector management, may be the appropriate vector control strategies in the area. There is also need for regular monitoring of the vector species composition, distribution and behavior for proper planning of appropriate vector control interventions in the future.

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Background:The blood-feeding patterns are crucial in incriminating disease vectors as well as facilitating the design and consolidation of effective vector control interventions in an area. Objective: This study aimed to establish if prolonged use of insecticide-treated bed nets (ITNs) caused a shift in the preferred hosts of the common malaria vectors as the hosts were under the IJTDH, 41(1): 16-25, 2020; Article no.IJTDH.54089 17 bed net. Such a shift would render ITNs less effective and would probably explain the continued morbidity and mortality due to malaria in the highly endemic Kamuli district. Methods: A total of 3,519 indoor and outdoor human biting female Anopheles gambiae sensu lato and An. funestus mosquitoes were collected from 48 households using human-baited bed net traps. All 187 indoor resting blood-fed anophelines collected were tested by direct enzyme-linked immunosorbent assay (ELISA) for blood meal host identification. Of these, 73 mid guts came from 24 households in villages with a 69% ITNs coverage, while 114 mid guts were from 24 households in non-ITN villages. Results: Blood meal hosts were identified in only 10.96% (n = 8) and 14.91% (n = 17) of the Anopheles blood meals from the intervention and non-intervention zones, respectively. Other blood meals could not be clearly identified. Eight (100%) blood meals in the intervention zone were from humans, while in the non-intervention zone, 15 (88.24%), one (5.88%) and one (5.88%) came from humans, cattle and goat, respectively. These findings demonstrated that the malaria vectors in Kamuli district are anthropophilic, with nearly all the mosquitoes collected from both zones feeding on humans during every blood meal (p = 0.82). This indicated high vector-human contacts, and thus implicating these species as important in the transmission of Plasmodium species and probably other infections. Conclusion: The use of insecticide-treated bed nets is effective for controlling malaria vectors inside houses, evoking universal coverage of houses in the area. Original Research Article