Browsing by Author "Kahamba, Najat"

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Common predators and factors influencing their abundance in Anopheles funestus aquatic habitats in rural south-eastern Tanzania
(PLOS ONE, 2023-06-26) Mahenge, Herieth; Muyaga, Letus; Nkya, Joel; Kifungo, Khamis; Kahamba, Najat; Ngowo, Halfan; Kaindoa, Emmanuel
Background The role of larval predators in regulating the Anopheles funestus population in various malaria-endemic countries remains relatively unknown. This study aimed to investigate the common predators that co-exist with Anopheles funestus group larvae and evaluate factors that influence their abundance in rural south-eastern Tanzania. Methods Mosquito larvae and predators were sampled concurrently using standard dipper (350 ml) or 10 L bucket in previously identified aquatic habitats in selected villages in southern Tan zania. Predators and mosquito larvae were identified using standard identification keys. All positive habitats were geo-located and their physical features characterized. Water physico chemical parameters such as dissolved oxygen (DO), pH, electrical conductivity (EC), total dissolved solids (TDS) and temperature were also recorded. Results A total of 85 previously identified An. funestus aquatic habitats in nine villages were sampled for larvae and potential predators. A total of 8,295 predators were sampled. Of these Coena grionidae 57.7% (n = 4785), Corixidae 12.8% (n = 1,060), Notonectidae 9.9% (n = 822), Aeshnidae 4.9% (n = 405), Amphibian 4.5% (n = 370), Dytiscidae 3.8% (n = 313) were com mon. A total of 5,260 mosquito larvae were sampled, whereby Anopheles funestus group were 60.3% (n = 3,170), Culex spp. 24.3% (n = 1,279), An. gambie s.l. 8.3% (n = 438) and other anophelines 7.1% (n = 373). Permanent and aquatic habitats larger than 100m2 were positively associated with An. funestus group larvae (P<0.05) and predator abundance(P<0.05). Habitats with submerged vegetation were negatively associated with An. funestus group larvae (P<0.05). Only dissolved oxygen (DO) was positively and significantly affect the abundance of An. funestus group larvae (P<0.05). While predators’ abundance was not impacted by all physicochemical parameters. Conclusion Six potential predator families were common in aquatic habitats of An. funestus group lar vae. Additional studies are needed to demonstrate the efficacy of different predators on lar val density and adult fitness traits. Interventions leveraging the interaction between mosquitoes and predators can be established to disrupt the transmission potential and sur vival of the An. funestus mosquitoes
Elevating larval source management as a key strategy for controlling malaria and other vector-borne diseases in Africa
(BMC, 2025-02-07) Okumu, Fredros; Moore, Sarah; Selvaraj, Prashanth; Yafin, Arnon; Juma, Elijah; Shirima, GloriaSalome; Majambere, Silas; Hardy, Andy; Knols, Bart; Msugupakulya, Betwel; Finda, Marceline; Kahamba, Najat; Thomsen, Edward; Ahmed, Ayman; Zohdy, Sarah; Chaki, Prosper; DeChant, Peter; Fornace, Kimberly; Govella, Nicodem; Gowelo, Steven; Hakizimana, Emmanuel; Hamainza, Busiku; Ijumba, Jasper; Jany, William; Kafy, Hmooda; Kaindoa, Emmanuel; Kariuki, Lenson; Kiware, Samson; Kweka, Eliningaya; Lobo, Neil; Marrenjo, Dulcisária; Matoke-Muhia, Damaris; Mbogo, Charles; McCann, Robert; Monroe,n April; Ndenga, Bryson; Ngowo, Halfan; Ochomo, Eric; Opiyo, Mercy; Reithinger, Richard; Sikaala, Chadwick; Tatarsky, Allison; Takudzwa, David; Trujillano, Fedra; Sherrard-Smith, Ellie
Larval source management (LSM) has a long history of advocacy and successes but is rarely adopted where funds are limited. The World Health Organization (WHO) guidelines on malaria prevention recommend the use of LSM as a supplementary intervention to the core vector control methods (insecticide-treated nets and indoor residual spraying), arguing that its feasibility in many settings can be limited by larval habitats being numerous, transient, and difficult to find or treat. Another key argument is that there is insufficient high-quality evidence for its effectiveness to support wide-scale implementation. However, the stagnation of progress towards malaria elimination demands that we consider additional options to the current emphasis on insecticidal commodities targeting adult mosquitoes inside homes. This letter is the result of a global, crossdisciplinary collaboration comprising: (a) detailed online expert discussions, (b) a narrative review of countries that have eliminated local malaria transmission, and (c) a mathematical modeling exercise using two different approaches. Together, these efforts culminated in seven key recommendations for elevating larval source management as a strategy for controlling malaria and other mosquito-borne diseases in Africa (Box 1). LSM encompasses the use of larvicide (a commodity) as well as various environmental sanitation measures. Together, these efforts lead to the long-term reduction of mosquito populations, which benefits the entire community by controlling both disease vector and nuisance mosquitoes. In this paper, we argue that the heavy reliance on large-scale cluster-randomized controlled trials (CRTs) to generate evidence on epidemiological endpoints restricts the recommendation of approaches to only those interventions that can be measured by functional units and deliver relatively uniform impact and, therefore, are more likely to receive financial support for conducting these trials. The explicit impacts of LSM may be better captured by using alternative evaluation approaches, especially high-quality operational data and a recognition of locally distinct outcomes and tailored strategies. LSM contributions are also evidenced by the widespread use of LSM strategies in nearly all countries that have successfully achieved malaria elimination. Two modelling approaches demonstrate that a multifaceted strategy, which incorporates LSM as a central intervention alongside other vector control methods, can effectively mitigate key biological threats such as insecticide resistance and outdoor biting, leading to substantial reductions in malaria cases in representative African settings. This argument is extended to show that the available evidence is sufficient to establish the link between LSM approaches and reduced disease transmission of mosquito-borne illnesses. What is needed now is a significant boost in the financial resources and public health administration structures necessary to train, employ and deploy local-level workforces tasked with suppressing mosquito populations in scientifically driven and ecologically sensitive ways. In conclusion, having WHO guidelines that recognize LSM as a key intervention to be delivered in multiple contextualized forms would open the door to increased flexibility for funding and aid countries in implementing the strategies that they deem appropriate. Financially supporting the scale-up of LSM with high-quality operations monitoring for vector control in combination with other core tools can facilitate better health. The global health community should reconsider how evidence and funding are used to support LSM initiatives.
Heterogeneous malaria transmission patterns in southeastern Tanzania driven by socio-economic and environmental factors
(BMC, 2025-05-29) Mukabana, Linda; Mshani, Issa; Gachohi, John; Minja, Elihaika; Jackson, Frank; Kahamba, Najat; Pinda, Polius; Muyaga, Letus; Msaky, Dickson; Ngowo, Halfan; Mambo, Susan; Olwendo, Amos; Bisanzio, Donal; Okumu, Fredros
Background As malaria-endemic countries progress towards elimination, distinct patterns of heterogeneous transmission are emerging. In south-eastern Tanzania, despite intensive control efforts, localized transmission shows prevalence ranging from under 1% to over 50% among nearby villages. This study investigated the socioeconomic and environmental factors driving this spatial heterogeneity. Methods A cross-sectional survey was conducted in the Kilombero and Ulanga districts of south-eastern Tanzania between 2022 and 2023, screening 3,249 individuals (ages 5–60) across 10 villages for malaria using rapid diagnostic tests (RDTs). Socioeconomic data was collected from all surveyed households and villages via questionnaires, while environmental data were obtained from remote sensing data sources. Associations between socioeconomic factors and malaria infection were analysed using a zero-inflated negative binomial model and employed a generalized additive model (GAM) to assess the impact of rainfall, and temperature on malaria infection. Results Greater elevation and higher rainfall were positively associated with malaria infection (OR = 1.68, 95% CI 1.38–2.05, p < 0.001 and OR = 1.46, 95% CI 1.14–1.87, p < 0.05 respectively), while temperature showed no significant effect (OR = 0.70, 95% CI 0.51–1.13, p = 0.117). Households in densely vegetated areas had higher malaria infections compared to those in more developed, built-up areas. At the individual level, males had a higher prevalence (355; 28.6%) and displayed significantly greater odds of infection (OR = 1.53, 95% CI 1.15–2.03, p < 0.05) than females (433; 21.6%). School-aged children (5–17 years) had a higher prevalence (36.9%) compared to adults (18–60 years) (15.9%). The probability of infection declined with increasing age (OR = 0.28, 95% CI 0.25–0.31, p < 0.001). Larger household sizes (more than four members) were positively associated with malaria infection (OR = 1.72, 95% CI 1.29–2.29, p < 0.001). Open-eave housing was associated with higher odds of malaria, whereas closed eaves (OR = 0.56, 95% CI 0.38–0.82, p < 0.05) and metal roofs (OR = 0.62, 95% CI 0.44–0.87, p < 0.05) were protective factors. Open water sources were positively associated with malaria infection compared to protected water sources (OR = 0.57, 95% CI 0.38–0.85, p < 0.05). Lack of bed net use was positively associated with malaria but this was not statistically significant (OR = 1.54, 95% CI 0.68–3.48, p = 0.299). Conclusion This study highlights the complex interplay between socioeconomic and environmental factors contributing to the fine-scale spatial heterogeneity of malaria in south-eastern Tanzania. Understanding these localized drivers is essential for designing targeted, effective strategies that support broader malaria elimination goals.
The needs and opportunities for housing improvement for malaria control in southern Tanzania
(BMC, 2023-02-27) Bofu, Ramadhani; Santos, Ellen; Msugupakulya, Betwel; Kahamba, Najat; Swilla, Joseph; Njalambaha, Rukiyah; Kelly, Ann; Lezaun, Javier; Christofides, Nicola; Okumu, Fredros; Finda, Marceline;
Background Malaria disproportionately afects low-income households in rural communities where poor housing is common. Despite evidence that well-constructed and mosquito-proofed houses can reduce malaria risk, housing improvement is rarely included in malaria control toolboxes. This study assessed the need, magnitude, and opportuni ties for housing improvement to control malaria in rural Tanzania. Methods A mixed-methods study was conducted in 19 villages across four district councils in southern Tanzania. A structured survey was administered to 1292 community members to assess need, perceptions, and opportunities for housing improvement for malaria control. Direct observations of 802 houses and surrounding environments were done to identify the actual needs and opportunities, and to validate the survey fndings. A market survey was done to assess availability and cost of resources and services necessary for mosquito-proofng homes. Focus group discussions were conducted with key stakeholders to explore insights on the potential and challenges of housing improvement as a malaria intervention. Results Compared to other methods for malaria control, housing improvement was among the best understood and most preferred by community members. Of the 735 survey respondents who needed housing improvements, a majority needed window screening (91.1%), repairs of holes in walls (79.4%), door covers (41.6%), closing of eave spaces (31.2%) and better roofs (19.0%). Community members invested signifcant eforts to improve their own homes against malaria and other dangers, but these eforts were often slow and delayed due to high costs and limited household incomes. Study participants suggested several mechanisms of support to improve their homes, including government loans and subsidies. Conclusion Addressing the need for housing improvement is a critical component of malaria control eforts in southern Tanzania. In this study, a majority of the community members surveyed needed modest modifcations and had plans to work on those modifcations. Without additional support, their eforts were however generally slow; households would take years to sufciently mosquito-proof their houses. It is, therefore, crucial to bring together the key players across sectors to reduce barriers in malaria-proofng housing in endemic settings. These may include government subsidies or partnerships with businesses to make housing improvement more accessible and afordable to residents.
Risk of Aedes-borne diseases in and around the Tanzanian seaport of Tanga despite community members being more concerned about malaria
(BioMed Central, 2024-12-18) Abas, Amri; Simfukwe, Alfred; Masalu, John; Kahamba, Najat; Nambunga, Ismail; Msaky, Dickson; Limwagu, Alex; Kipekepeke, Abdallah; Wergin, Carsten; Njalambaha, Rukiyah; Kemibala, Elison; Seleman, Amour; Mlacha, Yeromin; Finda, Marceline; Beisel, Uli; Kimaro, Esther; Ngowo, Halfan; Okumu, Fredros
Background Increased global trade, while beneficial economically, can also increase the spread of vector-borne diseases, particularly those transmitted by Aedes mosquitoes spreading via trade routes. Given the heightened trade- induced activity at ports of entry, it is particularly crucial to assess the risk of mosquito-borne diseases in these set- tings. This study compared the risks of Aedes-borne disease in and around the eastern Tanzanian seaport of Tanga. Methods A 200 m × 200 m grid-based system was used to sample mosquitoes within the port area, and in surround- ing areas at 2 km, 2.5 km, and 5 km away, between June and December 2023. We characterized mosquito breeding habitats, collected mosquito larvae using standard dippers and tested susceptibility of raised adult Aedes aegypti populations to different insecticides. Adult mosquitoes were collected using BG sentinel traps (daytime) and Centers for Disease Control (CDC) light traps (night-time). Additionally, more than 200 port users and neighboring residents were surveyed to assess their experiences with and perceptions of mosquito biting and disease risks. Results There were 2931 breeding sites, with (60.8%, n = 1782) positive for Aedes larvae. The percentage of water- holding containers infested with Aedes immatures, i.e., the container index (CI), was highest in the port area (66.2%), and lowest 5 km away (44.6%). The port area also had a greater proportion of temporary breeding sites (64.9%) than did the surrounding areas. The adult mosquito surveys revealed 20,449 mosquito species including: Culex quinquefasciatus (56.2%), Mansonia uniformis (38.6%), Ae. aegypti (5.1%), Anopheles gambiae (0.1%), and Anoph- eles funestus. Ae. aegypti were more abundant in the port area than in the surrounding areas (P < 0.001), whereas Culex sp., and Mansonia sp., were significantly outside (P < 0.001). Adult Anopheles sp., were found only in the port area, but Anopheles larvae were found both within and outside the port areas. Tests on Ae. aegypti sp., revealed susceptibility to bendiocarb and DDT, and resistance to permethrin. Awareness of mosquito-borne diseases among respondents was high for malaria (64.8%), but low for dengue (26.3%) and Chikungunya (1.7%). Most respond- ents reported being bothered by mosquitoes mostly at night (53.4%) or in the evening (40.7%). In addition to insecti- cidal bednets, which are used primarily against malaria, preventive measures for Aedes-borne diseases are limited. Conclusions This study identified significant potential risk of Aedes species, specifically Ae. aegypti sp., and associated diseases, but low perception of risk and inadequate personal protection measures in the study area. This low percep- tion of risk highlights the need to improve public knowledge of the transmission and control of Aedes-borne diseases.
Semi-field evaluation of aquatic predators for the control of Anopheles funestus in rural south-eastern Tanzania
(Springer Nature, 2024-08-02) Mahenge, Herieth; Muyaga, Letus; Nkya, Joel; Kafwenji, Andrew; Mwalugelo, Yohana; Kahamba, Najat; Ngowo, Halfan; Kaindoa, Emmanuel
Background Biological control is a promising alternative or complementary approach for controlling vector populations in response to the spread of insecticide resistance in malaria vectors. This study evaluated the efficacy of three selected potential predators on the density and fitness parameters of Anopheles funestus larvae in rural Tanzania. Methods Common predator families Aeshnidae (dragonflies), Coenagrionidae (damselflies), and Notonectidae (backswimmers) and An. funestus group larvae were collected from natural aquatic habitats in rural south-eastern Tanzania. Predators were starved for 12-h while An. funestus larvae were given fish food before starting the experiment. Anopheles funestus larvae were placed into artificial habitats containing predators, exposing them to potential predation. The number of surviving An. funestus larvae were counted every 24-h. An emergence traps were placed at the top of artificial habitats to capture emerging mosquitoes. Emerged mosquitoes were monitored until they died. Female wings were measured and used as a proxy for body size. Generalized linear mixed models (GLMM) with binomial variates at 95% CI and Cox proportional hazard models were used to assess the proportion of dead mosquitoes and the daily survival determined. Results There were significant differences in the number of emerged mosquitoes between the treatment and control groups (P<0.001). Thus, all predator species played a significant role in reducing the density of An. funestus mosquitoes (P<0.001). Furthermore, these predators had notable effects on the fitness parameters and survival of emerged mosquitoes (P<0.001). Among the three predators studied, Coenagrionidae (damselflies) were most efficient followed by Notonectidae (backswimmers), with Aeshnidae (dragonflies) being the least efficient. Conclusion Selected aquatic predators have the potential to reduce the survival and density of An. funestus larvae. They might eventually be included within an integrated malaria vector control strategy, ultimately leading to a reduction in malaria transmission.
Societal uses of the main water bodies inhabited by malaria vectors and implications for larval source management
(Springer Nature, 2024-11-09) Kahamba, Najat; Tarimo, Felista; Kifungo, Khamisi; Mponzi, Winifrida; Kinunda, Siaba; Simfukwe, Alfred; Mapua, Salum; Msugupakulya, Betwel; Baldini, Francesco; Ferguson, Heather; Okumu, Fredros; Finda, Marceline
Background: Larval source management (LSM) effectively reduces mosquito populations at their breeding sites, addressing issues like insecticide resistance that limit the effectiveness of primary interventions such as insecticide-treated nets (ITNs). Although traditionally used in urban and dry areas, recent research suggests it might also be effective in rural settings in eastern and southern Africa, where Anopheles funestus thrives in permanent water bodies that sustain year-round transmission. Targeting these habitats could enhance LSM, but it requires understanding local community practices, as mosquito breeding sites often overlap with community water resources. This study examined how communities use aquatic habitats and how these practices may impact LSM strategies, with a focus on habitats used by An. funestus. Methods: This study was conducted in three villages in the Ulanga and Malinyi districts of southeastern Tanzania using a mixed-methods approach. Quantitative data were collected through cross-sectional surveillance, and qualitative data through unstructured interviews, focus group discussions, and field observations. Data analysis integrated both quantitative and qualitative findings to develop a comprehensive understanding of community perspectives. Results: A survey of 931 aquatic habitats found mosquito larvae in 73% of them, with late instar An. funestus present in 23%. River streams made up 41% of the habitats, while ground pools accounted for 4%. Most habitats (90%) were used by communities, including 95% of those with An. funestus larvae, for activities such as domestic chores, agriculture, livestock rearing, brickmaking, and fishing. Focus group discussions revealed a willingness to adopt LSM, with a preference for larviciding and habitat modification over habitat removal, as the water sources were vital for daily use. Community concerns centered on the safety of larvicides for humans and animals, the environmental impact, and the need for better awareness of how LSM affects health and livelihoods. Conclusion: This study highlights community perspectives on LSM, focusing on the dual function of aquatic habitats as mosquito breeding sites and essential community water sources. This dual role presents both challenges and opportunities, suggesting that LSM strategies must balance public health needs with socio-economic realities. There was a clear preference for larviciding and habitat modification over removal, with a strong emphasis on health and environmental safety. The study emphasizes the importance of educating communities on the safety and effectiveness of LSM, and tailoring LSM strategies to fit the needs and preferences of local communities.
Spatial distribution and insecticide susceptibility profile of aedes aegypti mosquitoes in south-eastern, Tanzania
(NM-AIST, 2020-02) Kahamba, Najat
Aedes-borne diseases such as dengue and chikungunya constitute constant threats globally. In Tanzania, the main vector species is Aedes aegypti, which is widely distributed in urban areas, but whose ecology remains poorly-understood in growing towns and secondary cities. We collected adult mosquitoes using Gravid Aedes trap and surveyed aquatic habitats of Ae. aegypti mosquitoes in and around Ifakara, a fast-growing town in south-eastern Tanzania. Field-collected mosquitoes were tested for susceptibility to common insecticides in dry and rainy seasons. A total of 926 mosquitoes were collected, 431 (46.5%) were identified as Aedes aegypti, 487 (52.5%) Culex, 8 (0.01%) as other Aedes and 13 (0.01%) as Anopheles mosquitoes. Of 1515 and 1933 aquatic habitats examined in dry and rainy seasons respectively, 18.87% and 14.64% contained Aedes immatures (container index. In the 2315 and 2832 houses visited in dry and rainy seasons, 4.9% and 6.6% had at least one Aedes-positive habitat. The main habitat types included: (a) used vehicle tires and discarded containers, (b) flower pots and clay pots, and (c) holes made by residents on trunks of coconut trees to support climbing harvesters. Aedes aegypti adults were susceptible to all tested insecticides in both seasons, except bendiocarb, against which resistance was observed in rainy season. The high infestation levels indicate significant risk of Aedes-borne diseases, requiring immediate action to prevent potential outbreaks in the area. While used tires, discarded containers and flower pots are key habitats for Aedes, this study also identified coconut harvesting as an important risk factor, and the associated tree-holes as potential targets for Aedes control. Since Ae. aegypti mosquitoes are still susceptible to insecticides, effective control could combine environmental management, preferably involving communities, habitat removal and insecticide spraying.