Browsing by Author "Tenywa, Frank"

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Bioassays for the evaluation of the attractiveness of attractive targeted sugar bait (ATSB) against Anopheles mosquitoes in controlled semi-field systems
(BMC, 2025-02-04) Tenywa, Frank; Kibondo, Ummi; Entwistle, Julian; Dogan, Osward; Haruna, Mapipi; Phisoo, Restuta; Moore, Jason; Machange, Jane; Haji Makame1,; Tripet, Frederic; Müller, Pie; Mondy, Mathias; Nimmo, Derric; Stevenson, Jennifer; Moore, Sarah
Background Sugar feeding is an essential aspect of mosquito biology that may be exploited for mosquito control by adding insecticides to sugar attractants, so-called ‘attractive targeted sugar baits’ (ATSBs). To optimize their effectiveness, ATSB products need to be maximally attractive at both short and long range and induce high levels of feeding. This study aimed to assess the attractiveness and feeding success of Anopheles mosquitoes exposed to attractive sugar baits (ASBs). Method Experiments were conducted in 2 × 5 × 2-m cages constructed within the semi-field systems (SFS) at Ifakara Health Institute, Bagamoyo, Tanzania. Male and female Anopheles gambiae s.s. and An. funestus s.s. mosquitoes were exposed to either 20% sucrose or different ASB station prototypes produced by Westham Co. in either (1) no-choice experiments or (2) choice experiments. Mosquitoes were exposed overnight and assessed for intrinsic or relative olfactory attraction using fluorescent powder markers dusted over the ASB stations and 20% sucrose and for feeding using uranine incorporated within the bait station and food dye in 20% sucrose controls. Results Both male and female An. gambiae and An. funestus mosquitoes were attracted to the ASBs, with no significant difference between the sexes for each of the experiments conducted. Older mosquitoes (3–5 days) were more attracted to the ASBs (OR = 8.3, [95% CI 6.6–10.5] P < 0.001) than younger mosquitoes (0–1 day). Similarly, older mosquitoes responded more to 20% sucrose (OR = 4.6, [3.7–5.8], P < 0.001) than newly emerged Anopheles. Of the four prototypes tested, the latest iteration, ASB prototype v1.2.1, showed the highest intrinsic attraction of both Anopheles species, attracting 91.2% [95% CI 87.9–94.5%]. Relative to ATSB v1.1.1, the latest prototype, v.1.2.1, had higher attraction (OR = 1.19 [95% CI 1.07–1.33], P < 0.001) and higher feeding success (OR = 1.71 [95% CI 1.33–2.18], P < 0.001). Conclusions Data from these experiments support using ASBs v1.2.1, deployed in large-scale epidemiological trials, as it is the most attractive and shows the highest feeding success of the Westham prototypes tested. The findings indicate that future bioassays to evaluate ATSBs should use mosquitoes of both sexes, aged 3–5 days, include multiple species in the same cage or chamber, and utilize both non-choice and choice tests with a standard comparator. Background
DENV-2 Circulation and Host Preference Among Highly Anthropophilic, Outdoor-Biting Aedes aegypti in Dar es Salaam, Tanzania
(MDPI, 2025-06-05) Tenywa, Frank; Hälg, Silvan; Makame, Haji; Moore, Jason; Dogan, Osward; Mapipi, Harubu; Machange, Jane; Lilolime, Nasoro; Hofer, Lorenz; Batao, Lewis; Mwamlima, Tunu; Müller, Pie; Moore, Sarah
In Tanzania, dengue outbreaks have occurred almost annually over the past decade, with each new outbreak becoming more severe. This study investigated the preva- lence of dengue virus (DENV) serotypes in the wild Aedes aegypti and their blood sources to determine human exposure risk in Dar es Salaam, Tanzania. A two-year longitudinal survey was conducted in the Ilala, Kinondoni, and Temeke districts of Dar es Salaam to sample Ae. aegypti mosquitoes using Biogents Sentinel trap (BGS), Prokopack aspira- tion, and Gravid Aedes trap (GAT). Collected mosquitoes were pooled in groups of 10 and tested for DENV1–4 serotypes using reverse transcription polymerase chain reaction (RT-qPCR). Blood meal sources were identified using an enzyme-linked immunosorbent assay (ELISA). Of 854 tested pools, only DENV-2 was detected and was found in all three districts: Temeke (3/371 pools), Ilala (1/206 pools), and Kinondoni (1/277 pools). Blood meal analysis showed a strong preference for humans (81%) as well as for mixed blood meals that contained human blood and other hosts (17%). Out of 354 collected hosts seeking Ae. aegypti, 78.5% were captured outdoors and 21.5% indoors. This study confirms the circulation of DENV-2 in Ae. aegypti populations, indicating a potential dengue outbreak risk in Tanzania. This study also demonstrates that xenomonitoring may be feasible in this setting. The mosquitoes’ strong preference for human hosts and predominance in outdoor settings pose challenges for dengue control effort
Laboratory efficacy of Bactivec ® and Griselesf ® biolarvicides used for large-scale larviciding in Tanzania
(Frontiers, 2025-07-21) Tegemeo, Gavana; Kailembo, Denis; Machange, Jane; Venance Michael; Swai, Kyeba; Olukayode, Odufuwa; Tenywa, Frank; Mwalimu, Charles; Jubilate Bernard; Samwel Lazaro; Best Yoram; Kajange, Stella; Kasagama, Elizabeth; Kisoka, Noela; Mbuba, Emmanuel; Chaki, Prosper; Lengeler, Christian; Moore, Sarah
From 2022 to 2024, a project piloting large-scale larviciding in Tanzania was implemented in Tanga Region. The project used in-country manufactured biolarvicides, The study was conducted at Ifakara Health Institute (IHI) in Tanzania. Laboratory-based dose–response experiments were performed using Bactivec® and Griselesf® against laboratory-reared early third instar larvae of Anopheles gambiae sensu stricto, Anopheles arabiensis, Anopheles funestus, Aedes aegypti and Culex quinquefasciatus. Larvae were exposed to various concentrations of Bactivec® and Griselesf®. VectoBac® served as a positive control, and distilled water as a negative control. Twelve replicates per concentration, with 25 larvae per replicate, were tested. Larval mortality was recorded at 24 and 48 hours after exposure to Bactivec® and Griselesf®, respectively. Probit regression analysis was used to determine the lethal concentration (LC50 and LC90) values.Bactivec® and Griselesf®. This study independently assessed the efficacy of both biolarvicide products to ensure that they represented a good option for scaling up.