Hamidou Maiga

Background: Malaria control tools are nowadays challenged by the expansion and persistence of insecticide resistance in the malaria vector along with the changes in vector behaviour. To complement and reinforce the existing control tools, innovative vector control methods, such as gene drives, are currently under development. Understanding the Anopheles gambiae sensu lato ( An. gambiae s.l. ) population structure is crucial for the implementation of genetic control tools and improvement of existing control strategies. Here we investigated the genetic diversity and population structure of Anopheles gambiae s.l. populations from three climatic zones in Burkina Faso. Method: Mosquito specimens were collected across three ecological settings in Burkina Faso using pyrethroid spray catches. The whole genomes of Anopheles gambiae s.l. specimens were sequenced as part of the Anopheles gambiae 1000 Genomes Project. Data were analysed using MalariaGEN Resources to investigate the genetic diversity and the population structure. Results: The results revealed the absence of geographical population structure in Anopheles coluzzii and Anopheles gambiae sensu stricto ( An. gambiae s.s. ) collected in the three climatic zones, implicating high gene flow within the country. Anopheles arabiensis showed a structure that separates Hauts-Bassins samples in the Soudanian zone from other An. arabiensis samples. The cryptic species ( An. goundry and An. tengrela ) previously identified in the country were not detected in this study. Our findings also indicate population expansion in An. gambiae s.l. ; however, An. arabiensis populations show evidence of a smaller population size or a bottleneck. Conclusion: Our findings could indicate that An. arabiensis has a distinct demographic history. The population structure of An. gambiae s.s. and An. coluzzii across the country is characterized by a lack of geographical differentiation. These findings have important implications for both current vector control strategies and the potential implementation of gene drive technologies. Indeed, the lack of geographical population structure offers the potential for the rapid spread of gene drive constructs.

In mosquito Sterile Insect Technique (SIT) programs, adult male longevity is widely used as a quality control (QC) indicator for process monitoring and post-treatment assessment. However, longevity assays are frequently implemented using non-standardized protocols, limiting their comparability and operational interpretation. In this study, we evaluated whether and how key assay design parameters influence measured longevity and the ability of longevity-based tests to detect high dose irradiation related quality effects in male Aedes aegypti (Linnaeus, 1762). Using a factorial cage-based design, we assessed the effects of adult holding density, female presence, and observation period on male survival under standard holding conditions. Increasing density reduced male survival, primarily reflecting an assay-related stress effect. Irradiation consistently reduced longevity across all experimental conditions, while female presence imposed additional survival costs under some conditions. Combined high-density and mixed-sex environments produced the lowest overall survival but did not disproportionately amplify irradiation related effects. We also evaluated a rapid acute-stress assay conducted without access to sugar or water. Treatment-related differences were detectable during the early stages of the assay but diminished as mortality approached saturation, demonstrating that rapid stress assays are highly dependent on the timing of assessment. Together, these findings demonstrate that longevity-based QC indicators can be strongly influenced by experimental design and must be applied under standardized and purpose-specific conditions. Rapid stress assays can support routine SIT QC as targeted screening tools, but they require prior calibration and should not be considered universal proxies of overall male quality.

Variations in environmental parameters such as temperature and relative humidity (RH) can significantly affect mass-rearing outcomes and quality assessment. While the impact of broad temperature changes is well documented, the effects of small-scale fluctuations (1–2 °C shifts) on development and quality remain largely unexplored. This study was carried out to investigate the responses of Aedes aegypti and Aedes albopictus to incremental changes in rearing temperature and to evaluate the influence of temperature and RH on quality assessment with the Food and Agriculture Organization of the United Nations/International Atomic Energy Agency (FAO/IAEA) flight test device (FTD). First-instar larvae were reared under controlled conditions at five constant temperatures (26, 27, 28, 29 and 30 °C) maintaining the larval density and feeding regime as applied in mass-rearing conditions. Key parameters assessed included time to pupation, pupation rate, male escape rate, and body size. Additionally, male Ae. aegypti escape rate was evaluated under varying room temperatures and RH levels to assess the consistency and reliability of the FTD. Small-scale temperature fluctuations significantly impacted key life-history traits of Aedes mosquitoes, with higher temperatures accelerating time to pupation and enhancing pupation rates in both Ae. aegypti and Ae. albopictus . Moreover, Aedes albopictus consistently exhibited lower pupal yields and male escape rates compared to Ae. aegypti . Adult male quality assessed using the FTD was significantly influenced by the environmental temperature, but showed no significant variation in response to changes in RH. These results highlight the importance of precisely controlling environmental conditions during larval mass-rearing and adult quality assessment using the FAO/IAEA FTD to ensure consistent and reliable outcomes.

Anopheles funestus group and Anopheles gambiae complexes are among the most efficient malaria vectors in Africa, thriving in a variety of environm

Malaria transmission in sub-Saharan Africa is dominated by the An. gambiae complex and An. funestus group, whose distribution varies across ecological settings. Secondary species occur at lower densities, but their role in transmission may differ from one locality to another depending on local conditions. Assessing Anopheles biodiversity using ecological indices is therefore essential to characterise their diversity and relative abundance. This study investigated the biodiversity and spatial distribution of Anopheles species across the three climatic zones of Burkina Faso to guide effective vector control strategies. Indoor resting mosquitoes were collected from 67 health districts across the 13 regions of Burkina Faso between September and December 2022 using pyrethroid spray catches. A total of 30,521 Anopheles mosquitoes were identified, with An. gambiae s.l. dominating (94.4%). The Sudano-Sahelian zone recorded the highest abundance, followed by the Soudanian and Sahelian zones. Biodiversity decreased from humid southern to arid northern areas, with the Soudanian zone showing the highest diversity. Molecular analysis of 2026 An. gambiae s.l. specimens revealed marked heterogeneity: An. coluzzii predominated in Sahelian (74.9%) and Sudano-Sahelian (71.2%) zones, while An. gambiae s.s. was most frequent in the Soudanian zone (53.8%). These results highlight spatial and ecological differences in Anopheles composition across Burkina Faso and emphasize the need for locally adapted malaria vector control strategies.

Background: The sterile insect technique (SIT) is a well-established, environmentally friendly method of insect population suppression that relies on the release of sterile males to reduce reproduction in wild populations. SIT has been successfully applied against several insect pests, including the tsetse fly (hereafter tsetse) in Africa and Aedes aegypti mosquitoes in Asia and the Americas, and is increasingly considered to be a complementary tool for vector control. For an SIT programme to succeed, the release process must ensure good coverage of the targeted area without compromising the performance of the released insects. The use of release systems paired with drones may play an important role. While interest in aerial releases is growing, the number of available aerial release systems remains limited. Methods: The Birdview insect cassette, a lightweight, three-dimensional (3D)-printed device compatible with drones, was described and assessed for its suitability to release adult Aedes mosquitoes and tsetse under laboratory conditions. We determined the carrying capacity of the release system and the flight propensity, survival of and potential physical damage to Ae. aegypti and the tsetse Glossina palpalis gambiense , under laboratory conditions, using between 8000 and 30,000 insects. Results: Overall, our findings highlight the potential of the insect cassette system, which can support loading densities up to 45,000 Ae. aegypti or 11,000 G. p. gambiensis , with release efficiencies ranging from 60% to 96% and a survival rate of > 70% after a 26-day monitoring period. Of the released insects, > 80% escaped from flight ability devices. Conclusions: The Birdview insect cassette is valuable for aerial release programmes targeting Aedes mosquitoes and tsetse. Future research should focus on refining the system's design and functionality, as well as evaluating its performance in field settings to validate its effectiveness in vector control. Graphical

Dengue fever remains a significant public health concern in Sri Lanka, leading to recurrent epidemics and imposing substantial socio-economic burdens. This study aimed to assess the efficacy of the Sterile Insect Technique (SIT) against Aedes albopictus (Skuse), the predominant dengue vector in the country, through a pilot field trial of an Integrated Vector Management (IVM) strategy including the SIT. The pilot trial was conducted in the Gampaha district, which reports the second-highest number of dengue cases in the country. A total of 3,300,000 sterile males, exposed to a 50 Gy radiation dose, were released over 33 weeks (100,000/week) within a 30-hectare release area. Entomological assessments were conducted at 115 trapping stations over a period of 71 weeks (October 2020–August 2022). Induced sterility of 98.16% in mosquito eggs was reached within the release area as compared to the control area (binomial generalized linear mixed model, deviance 2.408, df = 2, p = 0.016), indicating a notable impact of the SIT. The trial achieved nearly 98% suppression of adult vector mosquitoes, with a sustained suppression effect for 13 weeks post cessation of releases. These findings suggest that SIT can be effectively integrated as a potential additional tool into the future IVM strategy in Sri Lanka.