Browsing by Author "Kibondo, Ummi"

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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
Contrasting vector competence of three main East African Anopheles malaria vector mosquitoes for Plasmodium falciparum
(Scientific reports, 2025-01-17) Kweyamba, Prisca; Hofer, Lorenz; Kibondo, Ummi; Mwanga, Rehema; Sayi, Rajabu; Matwewe, Fatuma; Lwetoijera, Dickson; Tambwe, Mgeni; Moore, Sarah
There are three Anopheles mosquito species in East Africa that are responsible for the majority of malaria transmission, posing a significant public health concern. Understanding the vector competence of different mosquito species is crucial for targeted and cost-effective malaria control strategies. This study investigated the vector competence of laboratory reared strains of East African An. gambiae sensu stricto, An. funestus s.s., and An. arabiensis mosquitoes towards local isolates of Plasmodium falciparum infection. Mosquito feeding assays using gametocytaemic blood from local donors revealed significant differences in both prevalence and intensity of oocyst and sporozoite infections among the three vectors. An. funestus mosquitoes presented the highest sporozoite prevalence 23.5% (95% confidence interval (CI) 17.5–29.6) and intensity of infection 6-58138 sporozoites. Relative to An. funestus, the odds ratio for sporozoites prevalence were 0.46 (95% CI 0.25–0.85) in An. gambiae and 0.19 (95% CI 0.07–0.51) in An. arabiensis, while the incidence rate ratio for sporozoite intensity was 0.31 (95% CI 0.14–0.69) in An. gambiae and 0.66 (95% CI 0.16–2.60) in An. arabiensis. Our findings indicate that all three malaria vector species may contribute to malaria transmission in East Africa, with An. funestus demonstrating superior vector competence. In conclusion, there is a need for comprehensive malaria control strategies targeting major malaria vector species, an update of malaria transmission models to consider vector competence and evaluation of malaria transmission blocking interventions in assays that include An. funestus mosquitoes.
In starvation, a bone can also be meat”: a mixed methods evaluation of factors associated with discarding of long-lasting insecticidal nets in Bagamoyo, Tanzania
(Springer Nature., 2022-03-24) Madumla, Edith; Moore, Sarah; Moore, Jason; Mbuba, Emmanuel; Mbeyela, Edgar; Kibondo, Ummi; Mmbaga, Selemani; Kobe, Dickson; Baraka, Jitihada; Msellemu, Daniel; Swai, Johnson; Mboma, Zawadi; Odufuwa, Olukayode
Background: Between 2000 and 2019, more than 1.8 billion long-lasting insecticidal nets (LLINs) were distributed in Africa. While the insecticidal durability of LLINs is around 3 years, nets are commonly discarded 2 years post distribu tion. This study investigated the factors associated with the decision of users to discard LLINs. Methods: A mixed-method sequential explanatory approach using a structured questionnaire followed by focus group discussions (FGDs) to collect information on experiences, views, reasons, how and when LLINs are discarded. Out of 6,526 households that responded to the questionnaire of LLINs durability trial, 160 households were randomly selected from the households in four villages in Bagamoyo Tanzania for FGDs but only 155 households participated in the FGDs. Five of the household representatives couldn’t participate due to unexpected circumstances. A total of sixteen FGDs each comprising of 8–10 adults were conducted; older women (40–60 years), older men (40–60 years), younger women (18–39 years), younger men (18–39 years). During the FGDs, participants visually inspected seven samples of LLINs that were “too-torn” based on Proportionate Hole Index recommended by the World Health Organi zation (WHO) guidelines on LLIN testing, the nets were brought to the discussion and participants had to determine if such LLINs were to be kept or discarded. The study assessed responses from the same participants that attended FGD and also responded to the structured questionnaire, 117 participants fulflled the criteria, thus data from only 117 participants are analysed in this study. Results: In FGDs, integrity of LLIN infuenced the decision to discard or keep a net. Those of older age, women, and householders with lower income were more likely to classify a WHO “too-torn” net as “good”. The common methods used to discard LLINs were burning and burying. The fndings were seen in the quantitative analysis. For every addi tional hole, the odds of discarding a WHO “too-torn” LLIN increased [OR=1.05 (95%CI (1.04–1.07)), p<0.001]. Younger age group [OR=4.97 (95%CI (3.25–7.32)), p<0.001], male-headed households [OR=6.85 (95%CI (4.44 –10.59)), p<0.001], and wealthy households [OR=3.88 (95%CI (2.33–6.46)), p<0.001] were more likely to discard LLINs.
PRONet Duo insecticide-treated net incorporated with chlorfenapyr and bifenthrin is superior to Interceptor® G2 nets against pyrethroid-resistant Anopheles gambiae sensu lato: a randomized experimental hut trial in Côte d’Ivoire and Tanzania using non-inferiority design
(Frontiers, 2025-03-14) Assenga, Alphonce; Ahoua Alou, Ludovic; Camara, Soromane; Koffi, Alphonsine; N’Guessan, Raphael; Kamande, Dismas; Ngonyani, Safina; Kibondo, Ummi; Odufuwa, Olukayode; Ntabaliba, Watson; Lekundayo, Ruth; Abilah, Faraji; Madumla, Edith; Muganga, Joseph; Moore, Jason; Moore, Sarah
Background: The widespread development of pyrethroid-resistant Anopheles populations, has reduced the efficacy of pyrethroid insecticide-treated nets (ITNs), hindering malaria control efforts. This study tested PRONet Duo, a new ITN with two active ingredients-bifenthrin and chlorfenapyr. Bifenthrin is a fluorinated pyrethroid that is highly stable and more slowly detoxified by pyrethroid-resistant mosquitoes. Chlorfenapyr disrupts cellular energy production. The efficacy of PRONet Duo was compared to Interceptor® G2, an alpha-cypermethrin and chlorfenapyr ITN with proven efficacy in malaria reduction. Methods: The study was conducted in two identical 9x9 Latin square experimental hut trials against wild free-flying Anopheles gambiae sensu lato in M’Bé, Côte d’Ivoire, and Lupiro, Tanzania using 18 experimental huts over 108 nights. The primary endpoint was the proportion of 72-hour mosquito mortality (M72) and the secondary endpoint was the proportion of mosquito blood-feeding. The study was done following World Health Organization guidelines. Data were analyzed using mixed-effect linear regression with a 7% margin of non-inferiority. Data were classified as non-inferior using delta and superior using the line of no difference. Results: PRONet Duo demonstrated a non-inferior and superior mosquito mortality compared to Interceptor® G2 in both study sites. In Côte d’Ivoire, the M72 of PRONet Duo was 84% [81,88], higher than that of Interceptor® G2 (72% [68,76], OR: 1.54 [1.27,1.88]) and it was superior to MAGNet® (30% [27,34], OR: 13.74 [11.35,16.63], p<0.0001). In Tanzania, M72 of PRONet Duo was 68% [62,73], higher than that induced by Interceptor® G2 (44% [40,49], Odds Ratio (OR): 2.77 [2.31, 3.33]), and MAGNet® (36% [32,41], OR:4.82 [4.06,5.72] p<0.0001). PRONet Duo also induced non-inferior and superior prevention of blood-feeding compared to Interceptor® G2, with less than 11% feeding success observed in either trial site. Conclusion: PRONet Duo ITNs are non-inferior and superior to the first-in-class Interceptor® G2 in terms of mosquito mortality and prevention of blood-feeding demonstrating the added benefit of bifenthrin for insecticide resistance management. Both chlorfenapyr nets offered superior mortality compared to the pyrethroid-only ITN. PRONet Duo offers an additional highly effective ITN for control of pyrethroid-resistant mosquitoes in malaria endemic regions.