From the laboratories of the Centre for Applied Entomology and Parasitology at Keele University and the Institut de Recherche en Sciences de la Santé in Burkina Faso, a new study led by Akpodiete Nwamaka O, Diabate Abdoulaye, and Tripet Frédéric provides insightful findings that may revolutionize mass-rearing techniques for malaria vector mosquitoes, particularly the Anopheles gambiae complex. The research, recently published in Parasites & Vectors, opens potential avenues to enhance the success of sterile insect and genetically-modified mosquito release programs as part of the integrated vector management (IVM) strategies in the fight against malaria – a disease that continues to inflict high morbidity and mortality rates in sub-Saharan Africa.
DOI: 10.1186/s13071-019-3465-0.
As insecticide resistance threatens to diminish the impact of conventional vector control methods such as bed nets and indoor residual spraying, complementary approaches are considered imperative. One such strategy focuses on the release of sterile or modified mosquitoes to reduce the population of these malaria vectors. However, the production of high-quality mosquitoes that could successfully compete with wild populations for mates is of paramount importance for the efficacy of such biocontrol initiatives.
The sibling species of the Anopheles gambiae complex, including An. gambiae sensu stricto and An. coluzzii, are primary vectors of malaria in sub-Saharan Africa. The breeding habits of their larvae – favoring clean, soft water – have driven speciation and localized adaptations that influence their respective distributions and vectorial capacities.
Understanding that water hardness and nutrition are crucial to larval development, researchers compared the effects of deionised, mineral, and mixed water types on first-instar larvae reared in controlled insectary conditions. Additionally, the investigation delved into the influence of two standardized feeding regimens – solution and powder feed – on the developmental outcomes of the mosquitoes.
The findings were significant, delineating clear impacts on phenotypic traits linked to vectorial capacity. Mosquitoes raised in mineral water exhibited earlier emergence times and greater adult sizes compared to those reared in deionised water – with wing-length identified as a sensitive metric of mosquito quality. These phenotypic benefits were prevalent across both sexes and strains tested, including the Kisumu strain of An. gambiae and the Mopti and VK3 strains of An. coluzzii.
Given that larger mosquitoes have been associated with greater survival, blood-feeding success, and potential for malaria transmission, this study highlighted that mineral water and powder feed contributed positively to the desired phenotypic quality. While the increase in mosquito numbers was not statistically significant, the enhanced phenotypic quality holds implications for improved mating competitiveness, longevity, and fecundity – traits that are critical for the success of release programs.
The research underscores the need for optimized rearing protocols that incorporate mineral water – a shift from the common use of deionised water in many mosquito rearing setups. Furthermore, the interplay between water type and nutrition offers a tangible approach to achieve high-quality mosquitoes for release programs, which can complement current control measures and add resilience against insecticide resistance.
As the research team recommends further studies to assess how these fitness traits translate into field conditions and impact malaria transmission dynamics, there is cautious optimism that improving mass-rearing techniques may lead to more robust vector control strategies. Such enhancements are particularly pertinent in the wake of rising concerns surrounding the effectiveness of insecticide-based control in the face of growing resistance.
With thoughtful consideration to local ecological contexts and adaptive mosquito behaviors, this line of research propels us toward a more nuanced understanding of vector biology – a critical component in the quest to curb malaria’s burden on humanity.
References
1. Akpodiete Nwamaka O, Diabate Abdoulaye, Tripet Frédéric. “Effect of water source and feed regime on development and phenotypic quality in Anopheles gambiae (s.l.): prospects for improved mass-rearing techniques towards release programmes.” Parasites & Vectors, vol. 12, no. 1, 2019, p. 210, doi:10.1186/s13071-019-3465-0.
2. World Health Organization. “World Malaria Report 2017.” Geneva: World Health Organization, 2017.
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4. Della Torre A, Costantini C, Besansky NJ, Caccone A, Petrarca V, Powell JR et al. “Speciation within Anopheles gambiae – the glass is half full.” Science, vol. 298, 2002, pp. 115-117, doi:10.1126/science.1078170.
5. Takken W, Smallegange RC, Vigneau AJ, Johnston V, Brown M, Mordue-Luntz AJ, et al. “Larval nutrition differentially affects adult fitness and Plasmodium development in the malaria vectors Anopheles gambiae and Anopheles stephensi.” Parasites & Vectors, vol. 6, 2013, p. 345, doi:10.1186/1756-3305-6-345.
Keywords
1. Anopheles gambiae rearing
2. Mosquito quality control
3. Sterile insect technique
4. Malaria vector management
5. Insectary water type