Biology subjects

DIABATE, A.

Publications and source records attributed to DIABATE, A..

3 recordsLinked to original sources

bioRxiv2026

Multi-site phenotypic characterisation of Kisumu colonies for comparison of insecticide susceptibility between testing centres

Testing of insecticides and insecticide-based vector control tools relies on the use of bioassays whereby insects are exposed and mortality, or another relevant entomological endpoint, is measured. To be able to compare results between products and across time and space standard laboratory strains are used. Insecticide-susceptible strains are often used as comparators in studies involving insecticide-resistant populations. Kisumu is a long-established, widely-used insecticide-susceptible strain of Anopheles gambiae. In this study, 16 facilities across different countries exposed their Kisumu colonies aged 3-5 days to four insecticides (permethrin, alpha-cypermethrin, DDT and pirimiphos-methyl) at a range of concentrations in WHO tube assays to assess susceptibility. Insecticide-treated filter papers were made at the Liverpool School of Tropical Medicine and sent to testing centres, along with a standard protocol and testing conditions requirements, to standardise testing as much as possible. A first observation was that DDT results were affected by the use of Risella oil, the WHO-recommended carrier oil but immiscible in acetone, leading to uneven coating of papers and increased variability in bioassay results (40x variance between colonies). Bioassay data generated by the testing facilities suggest a wide range of susceptibility to different insecticides between colonies of Kisumu: LC50 values between colonies differed, though not significantly, by up to 4x for permethrin, 6x for pirimiphos-methyl, and 15x for alpha-cypermethrin. Some colonies are classified as insecticide resistant based on the WHO definition of <98% mortality on exposure to a discriminating concentration. The assumption that Kisumu is a standard susceptible strain, consistent between facilities is challenged, which has implications when comparing results between studies. We propose genotypic analysis of the colonies to identify signs of resistance markers indicative of contamination from resistant strains or wild mosquitoes, and generation of guidance to support the maintenance and monitoring of susceptible mosquito strains.

zoology↗

bioRxiv2026

Laboratory An. gambiae s.l. mosquito colonies show sustained high transmission of Microsporidia sp. MB and a small fecundity cost

Microsporidia sp. MB, a microsporidian symbiont found naturally in Anopheles mosquitoes, has potential as a novel malaria control tool since it can inhibit Plasmodium development and transmission. The most feasible MB-based Plasmodium control strategy would involve dissemination through live mosquito releases, or release of spores infective to mosquito larvae. To implement either strategy, establishment of stable mosquito colonies carrying MB at a high frequency is likely to be essential. The progeny of field caught An. gambiae s.l from Burkina Faso were isolated for individual egg laying and tested for MB. The progeny of the MB positive females were pooled and this process was repeated for multiple generations. The relative density of MB in different life stages and tissues of the An. coluzzii host was examined using a novel duplex qPCR assay. We also examined the impact of MB on fecundity through individualization for egg laying and counting of eggs. Finally, we examined laid eggs for presence of MB spores. Three An. coluzzii colonies and one An. gambiae s.l hybrid colony were established with high prevalence and density of MB and were maintained for more than two years with minimal intervention. MB prevalence and density was highest in eggs and adult females and lowest in L4 larvae; in adults density was highest in the gonads. Additionally, MB density increased in ovary samples following blood feeding which was likely due to the activation of sporogony. The production of spores is the reason why MB-carrying females lay more white non-hatching eggs and show a small reduction in fecundity. Establishment of several stable MB carrying An. gambiae s.l colonies and understanding the impact of spores on fecundity are significant steps forward in developing MB as a malaria control tool.

microbiology↗

bioRxiv2025

Maternal and cross-stage effects of Metarhizium fungal infection on the malaria mosquito Anopheles coluzzii life-history

BackgroundEntomopathogenic fungi of the Metarhizium genus are widely used as biocontrol agents against harmful insects. These fungi are cost-effective and eco-friendly for vector control, providing an alternative to synthetic chemical insecticides. They have great potential as larvicides against malaria vectors, but their impacts on mosquito fitness have not been fully measured. This study evaluated the effect of Metarhizium fungal strains, locally isolated in Burkina Faso, on the larval survival of the mosquito Anopheles coluzzii, the life history of the emerging adults and on the maternal effects of exposed females. MethodsWe assessed the efficacy of Metarhizium pingshaense (strains S10 and S26) conidia against An. coluzzii larvae. First, larvae were reared in the presence of fungal spores and the survival of the larvae and adults that emerged, their wing length, oviposition rate and blood feeding behaviour were measured. Additionally, we assessed the efficacy of fungal strains S10 and S26 conidia against An. coluzzii adults by spraying them with spore suspensions and assessing the survival of their larval offspring. Survival data was analyzed using Cox proportional hazards model, while other life history traits using generalized linear mixed models. ResultsThe fungal suspension applied to the water in which the larvae were reared caused mortality at the pupae stage. Only a small number of larvae emerged to reach adulthood. Furthermore, at the adult stage, these mosquitoes exhibited reduced survival compared to the control. However, body size and blood-feeding behavior were not affected by the treatment. When fungi was applied to adult females, the number of eggs layed was more abundant in infected group compared to controls, however a lower proportion of larvae successfully developed into adults. ConclusionThe results of this study demonstrate the potential of Metarhizium pingshaense conidia for mosquito larval control. The identified cross-stage and maternal effects showed additional virulent effects of Metarhizium, thus reinforcing the evidence that this biocontrol agent should be part of an integrated vector management. Future work should focus on the molecular mechanism of the fungal infection at the larval stage to improve formulation or genetically engineer the conidia of these strains to make them more virulent.

microbiology↗