Joseph Barnabas Muganga

Aedes aegypti surveillance is essential for guiding arbovirus control strategies. The BG-Sentinel (BGS) trap is a widely used reference trap for monitoring adult Ae. aegypti, but its cost and need for electricity limit its use in resource-constrained settings. This study evaluated locally made, low-cost oviposition-based traps relative to the BGS trap. The Ovillanta trap was modified with internal adhesive surfaces to capture adult mosquitoes. Six trap types were evaluated at six outdoor locations, including (1) Ovillanta with yeast (2) Ovillanta with only water, (3) BG-Gravid Aedes Trap (BG-GAT) with yeast, (4) one modified GAT (1MoGAT) with yeast, (5) four modified GATs (4MoGAT) with yeast, and (6) a standard BGS trap with BG-Lure. Traps were deployed for three consecutive 24 h sampling periods before rotation. This process was repeated four times resulting in a total of 72 experimental days. The primary outcome was total number of captured female Ae. aegypti. The yeast-baited modified Ovillanta captured more Ae. aegypti than the other oviposition-based traps (n = 468), with catches comparable to the BGS trap (n = 497; IRR = 1.03, 95% CI: 0.76–1.41; p = 0.859). Removing yeast from the Ovillanta reduced captures by 31% (n = 321; IRR = 0.69, 95% CI: 0.51–0.95; p = 0.023). The BG-GAT (n = 95), 4MoGAT (n = 35), and 1MoGAT (n = 31) captured significantly fewer Ae. aegypti than the yeast-baited modified Ovillanta (all p < 0.0001). Around 95% of captured mosquitoes were unfed across all trap types. These findings suggest that the yeast-baited modified Ovillanta may provide a low-cost alternative for adult female Ae. aegypti surveillance, but further evaluation across diverse ecological and operational settings is needed.

Aedes aegypti surveillance is essential for guiding arbovirus control strategies. The BG-Sentinel (BGS) trap is a widely used reference trap for monitoring adult Ae. aegypti, but its cost and need for electricity, limit its use in resource-constrained settings. This study evaluated locally made, low-cost oviposition-based traps relative to the BGS trap. The Ovillanta trap was modified with internal adhesive surfaces to capture adult mosquitoes. Six trap types were evaluated at six outdoor locations, including 1) Ovillanta with yeast 2) Ovillanta with only water, 3) BG-Gravid Aedes Trap (BG-GAT) with yeast, 4) one modified GAT (1MoGAT) with yeast, 5) four modified GATs (4MoGAT) with yeast, and 6) standard BGS trap with BG-Lure. Traps were deployed for three consecutive 24-hour sampling periods before rotation. This process was repeated four times resulting in a total of 72 experimental days. The primary outcome was total captured of female Ae. aegypti. The yeast-baited modified Ovillanta captured more Ae. aegypti than the other oviposition-based traps (n = 468), with catches comparable to the BGS trap (n = 497; IRR = 1.03, 95% CI: 0.76–1.41; p = 0.859). Removing yeast from the Ovillanta reduced captures by 31% (n = 321; IRR = 0.69, 95% CI: 0.51–0.95; p = 0.023). The BG-GAT (n = 95), 4MoGAT (n = 35), and 1MoGAT (n = 31) captured significantly fewer Ae. aegypti than the yeast-baited modified Ovillanta (all p < 0.0001). Around 95% of captured mosquitoes were unfed across all trap types. These findings suggest that the yeast-baited modified Ovillanta may provide a low-cost alternative for adult female Ae. aegypti surveillance, but further evaluation across diverse ecological and operational settings is needed.

Background: Gaps in unimproved house structures, especially in eaves and windows, allow mosquito entry, increasing indoor vector-borne disease transmission. Simple modifications to such houses may reduce human exposure, and insecticide treatment may kill mosquitoes, benefiting all community members. This study evaluated insecticide-treated screening (ITS) for eaves and windows, incorporated with deltamethrin and piperonyl butoxide (PBO), compared to a permethrin and PBO-treated bednet in Tanzania. Method: A randomised Latin-square design (4 × 4) was used in four experimental huts within a large netting cage to allow mosquito recapture inside and outside of huts. Four treatments were evaluated: (1) new (12-month stored) ITS; (2) 12-month naturally-aged ITS; (3) 12-month field-used pyrethroid-PBO bednet (standard of care in Tanzania), and (4) no treatment. The study was performed for 32 nights using 30 mosquitoes per strain, per hut per night. Four laboratory-reared strains were used: malaria vectors ( Anopheles arabiensis and An. funestus ), dengue vector ( Aedes aegypti ), and nuisance biting ( Culex quinquefasciatus ). Recaptured mosquitoes were assessed for mortality at 72 h, blood-feeding, and hut entry. A simulation with a modified mechanistic model tracking Plasmodium falciparum malaria was used to illustrate potential epidemiological impact from these products. Results: Against all mosquito species compared to 12-month aged pyrethroid-PBO-treated bednet, new ITS induced higher mortality [Odds Ratio:2.25(95%Confidence Interval:1.65–3.06), p < 0.0001], and aged-ITS was similar [OR:0.80(95%CI:0.59–1.08), p = 0.141]. Both new and aged ITS significantly ( p < 0.0001) reduced mosquito blood-feeding [new OR:0.02(95% CI:0.01–0.03); aged OR:0.09(95%CI:0.05–0.14)] and hut entry [new IRR:0.10(95%CI:0.08–0.13); aged IRR:0.25(95%CI:0.21–0.31)]. Transmission model estimates indicate epidemiological impacts of ITS may supersede pyrethroid-PBO-treated bednets at the population level. The model results indicate impact potency depends on assumed intervention percentage cover, durability, and mosquito bionomics. Conclusions: This study introduces a standardised semi-field bioassay to evaluate ITS, generating entomological data that, for the first time, enabled modelling of its potential impact on malaria transmission. ITS is an efficacious tool for public health as it kills substantial proportions of malaria and dengue vectors, and reduces nuisance biting. Given its simplicity, it should be considered an additional or stand-alone tool for screening unimproved houses.

New insecticides for indoor residual spraying (IRS) are being developed to manage resistance. Chlorfenapyr (Sylando^® 240SC), a pro-insecticide, is metabolized by active mosquitoes into the toxic metabolite tralopyril. This mode of action requires adapted “free flying” bioassays (because chlorfenapyr is converted to its toxic metabolite tralopyril when mosquitoes are metabolically active). A miniature-experimental hut (MEH) assay was developed within the Ifakara Ambient Chamber Test (I-ACT) with a rabbit as a host to measure residual efficacy under controlled conditions. Sylando^® 240SC was compared with SumiShield^® 50WG (clothianidin) for 12-month residual efficacy against malaria and arbovirus vectors. Residual activity was assessed on mud, wood and concrete with two huts per substrate treated with Sylando^® 240SC, one with SumiShield^® 50WG, and one with untreated control. Five replicates of 20 mosquitoes per strain (malaria vectors: pyrethroid-susceptible Anopheles gambiae and -resistant An. arabiensis and An. funestus; culicines Aedes aegypti and Culex quinquefasciatus) were exposed overnight at one-week post spraying and monthly thereafter. Multivariable mixed-effect logistic regression with binomial errors and log link function assessed non-inferiority with a 7% margin on mosquito mortality as the primary outcome for malaria vectors. Both products induced delayed mortality, with higher effects on malaria vectors than culicines. Across all substrates and malaria species combined over the full 12 months of observation, Sylando^® 240SC was non-inferior to SumiShield^® 50WG on mortality measured at 72 h (76% vs. 67%, OR = 0.86, 95% CI: 0.77–0.97) and 168 h (89% vs. 82%, OR = 0.74, 95% CI: 0.63–0.87). Sylando^® 240SC performed comparably to SumiShield^® 50WG, supporting its use as an IRS additional option. The new I-ACT mini-experimental-hut assay provides a practical tool for evaluating pro-insecticides. The importance of free-flight evaluation methods for pro-insecticides is discussed.

New insecticides for indoor residual spraying (IRS) are being developed to manage resistance. Chlorfenapyr (Sylando^® 240SC), a pro-insecticide, is metabolised by active mosquitoes into the toxic metabolite tralopyril. This mode of action requires adapted “free flying” bioassays. A miniature-experimental hut (MEH) assay was developed within the Ifakara Ambient Chamber Test (I-ACT) with a rabbit blood host to measure residual efficacy under controlled conditions. Sylando^® 240SC was compared with SumiShield^® 50WG (clothianidin) for 12-month residual efficacy against malaria and arbovirus vectors. Residual activity was assessed on mud, wood and concrete with two huts per substrate treated with Sylando^® 240SC, one with SumiShield^® 50WG, and one untreated control. Five replicates of 20 mosquitoes per strain (malaria vectors: pyrethroid-susceptible Anopheles gambiae, resistant An. arabiensis and An. funestus; culicines Aedes aegypti and Culex quinquefasciatus) were exposed overnight at one-week post-spraying and monthly thereafter. Multivariable mixed-effects logistic regression assessed non-inferiority with a 7% margin. Both products induced delayed mortality, with higher effects on malaria vectors than culicines. Across all substrates and malaria species combined over the full 12 months of observation, Sylando^® 240SC was non-inferior to SumiShield^® 50WG at 72 h (76% vs. 67%, OR=0.86, 95% CI: 0.77–0.97) and 168 h (89% vs. 82%, OR=0.74, 95% CI: 0.63–0.87). Sylando^® 240SC performed comparably to SumiShield^® 50WG, supporting its use as an IRS option. The new I-ACT mini-experimental-hut assay provides a practical tool for evaluating pro-insecticides. The importance of free flight evaluation methods for pro-insecticides is discussed.

Controlling mosquito-borne diseases is increasingly challenging due to factors such as outdoor and early biting mosquitoes and logistical or behavioral barriers, particularly in displaced populations where the use and efficacy of core interventions are inadequate. This study evaluated the impact of BiteBarrier, a transfluthrin-based spatial emanator, over eight weeks of aging against multiple mosquito species in semi-field system simulating both indoor and outdoor settings. We assessed the protective efficacy using both landing rate and feeding success methods across five mosquito species, including pyrethroid susceptible Anopheles gambiae sensu stricto (s.s.) and Aedes aegypti, An. gambiae s.s. with knock down resistance (KDR), and pyrethroid resistant An. funestus and Culex quinquefasciatus with upregulation of mixed function oxidases. The results show that the feeding endpoint provides more robust estimates of protective efficacy compared to the landing endpoint. The BiteBarrier provided over 93% (95% CI: 92 - 93) protection indoors and 80% (95% CI: 78 - 81) outdoors against mosquito bites and substantial mortality 47% (95% CI: 43 - 53) indoor and 26% (95% CI: 22 - 30) outdoors, regardless of mosquito species or resistance status. Overall, the BiteBarrier shows potential as a tool for reducing mosquito bites and vectorial capacity, offering protection over at least eight weeks of use for both indoor and outdoor environments.

The study assessed the trapping efficacy of locally modified (1) Gravid Aedes Trap (GAT) lined with insecticide-treated net (ITN) as a killing agent and (2) Autocidal Gravid Ovitrap (AGO) with sticky board in the semi-field system (SFS) and field setting. Fully balanced Latin square experiments were conducted to compare GAT lined with ITN vs. AGO, both with either yeast or grass infusion. Biogent-Sentinel (BGS) with BG-Lure and no CO₂ was used as a standard trap for Aedes mosquitoes. In the SFS, GAT outperformed AGO in collecting both nulliparous (65% vs. 49%, OR = 2.22, [95% CI: 1.89–2.60], p < 0.001) and gravid mosquitoes (73% vs. 64%, OR = 1.67, [95% CI: 1.41–1.97], p < 0.001). Similar differences were observed in the field. Yeast and grass infusion did not significantly differ in trapping gravid mosquitoes (OR = 0.91, [95% CI: 0.77–1.07], p = 0.250). The use of ITN improved mosquito recapture from 11% to 70% in the SFS. The same trend was observed in the field. Yeast was chosen for further evaluation in the optimized GAT due to its convenience and bifenthrin net for its resistance management properties. Mosquito density was collected when using 4× GATs relative to BGS-captured gravid mosquitoes 64 vs. 58 (IRR = 0.82, [95% CI: 0.35–1.95], p = 0.658) and showed no density dependence. Deployment of multiple yeast-baited GAT lined with bifenthrin net is cost-effective (single GAT < $8) compared to other traps such as BGS ($160).

The study assessed the trapping efficacy of locally-modified 1) Gravid Aedes Trap(GAT) lined with insecticide-treated net (ITN) as a killing agent, 2) Autocidal Gravid Ovitrap(AGO) with sticky board in the semi-field system (SFS) and field setting. Fully-balanced Latin square experiments were conducted to compare GAT lined with ITN vs AGO, both with either yeast or grass infusion. Biogents-Sentinel (BGS) with BG-Lure and no CO2 was used as standard trap for Aedes mosquitoes. In the SFS, GAT outperformed AGO in collecting both nulliparous (65% vs 49%,OR=2.22,[95%CI:1.89-2.60],p

Background: Despite extensive use of available vector control tools, the burden of malaria and dengue continues to increase throughout sub-Saharan Africa. Gaps in house structures, most especially in eaves and windows, allow vector entry and facilitate indoor vector biting and disease burden. Simple house modification tools that target these structures therefore have the potential to reduce human exposure to bites in the home. This study assessed the performance of Insecticide Treated Screening (ITS) comprising Eave Nets and Window Screens (ITENs & ITWS), incorporated with deltamethrin and piperonyl-butoxide (PBO) in Tanzania. Method: A randomised Latin square (4 X 4) was conducted in four experimental huts built in a semi-field system (SFS). Each hut within each of the chambers of the SFS was covered with a large netting cage to allow recapture of mosquitoes inside and outside of the huts. Four treatment arms were evaluated: 1) new ITS; 2) 12-months naturally-aged ITS; 3) estimated 12 months field-used Olyset® Plus ITNs (Standard-of-Care in Tanzania), and; 4) no treatment. The study was performed for 32 nights using a minimum of 30 mosquitoes per strain per night, that is, a total of 120 (4 x 30) mosquitoes per hut per night. Four laboratory-reared strains were used: transmitters of malaria ( Anopheles arabiensis and An. funestus ) and dengue infection ( Aedes aegypti ) and those known for nuisance biting ( Culex quinquefasciatus ). Recaptured mosquitoes were assessed for mortality at 72 hours (M72), blood feeding and hut entry endpoints. A simulation exercise with a modified mechanistic model tracking Plasmodium falciparum malaria was used to illustrate the potential epidemiological impact from these products. Results: New ITS induced higher M72 than field-used ITNs against all mosquito species tested [OR: 2.25 (95%CI: 1.65-3.06), p<0.0001], while M72 was similar between aged ITS and field-used ITNs [OR: 0.80 (95%CI: 0.59-1.08), p=0.141]. Both new, and aged ITS reduced more mosquito blood feeding and hut entry than field-used ITNs for all mosquito species tested (p<0.0001). Transmission model estimates indicate epidemiological impacts of ITS may supersede those of ITNs at the population level. The model results indicate that the potency of these impacts depends on assumed intervention percentage cover, durability and mosquito bionomics. Conclusions: ITS is an efficacious tool for controlling vectors transmitting malaria, and dengue, and those known for nuisance biting in a semi-field setting. Given the intervention’s simplicity, it should be considered as an additional (or stand-alone) tool alongside behavioural change educational efforts to encourage the repurposing of old ITNs for house screening.