Biology subjects

Simma, E. A.

Publications and source records attributed to Simma, E. A..

3 recordsLinked to original sources

bioRxiv2025

The influence of Temperature and Relative Humidity on the Development and Survival of Laboratory-Reared Anopheles arabiensis in Ethiopia

Malaria, a major vector-borne disease transmitted by female Anopheles mosquitoes, remains a critical public health challenge in tropical and subtropical regions. Climate change influences vector distribution, abundance, and disease transmission patterns. This study examined the influence of temperature and humidity on the development, abundance, and survival of Anopheles arabiensis, a key malaria vector in Ethiopia. Laboratory reared susceptible An. arabiensis strain mosquitoes were reared under varying conditions, with 400 eggs exposed to temperatures of 14.5-34.35{degrees}C and relative humidity (RH) levels of 64-84% and compared with the ones that reared under standard insectary conditions. Development and survival rates were analyzed across 20 temperature-humidity regimes using SPSS 26, with linear regression, OLS, and quadratic regression models. Results showed optimal egg hatchability (80%) at 25.3-34.35{degrees}C and 64-68% RH. Adult emergence peaked (80%) at 28.37-29.65{degrees}C and 70% RH, but declined significantly below 16{degrees}C and 64% RH. The longest larval development (13 days) occurred at 14.55-15.62{degrees}C and 83-86% RH, while adult survival reached 25 days at 23.65-24.72{degrees}C and 68-69% RH. These findings highlight the profound influence of temperature and humidity on An. arabiensis life stages, emphasizing their role in mosquito population dynamics. Further research is needed to explore how these factors affect malaria parasite development within vectors, offering insights to improve malaria control strategies.

ecology↗

bioRxiv2025

The origin, invasion history and resistance architecture of Anopheles stephensi in Africa.

The invasion of Africa by the Asian urban malaria vector, Anopheles stephensi, endangers 126 million people across a rapidly urbanising continent where malaria is primarily a rural disease. Control of An. stephensi requires greater understanding of its origin, invasion dynamics, and mechanisms of widespread resistance to vector control insecticides. We present a genomic surveillance study of 551 An. stephensi sampled across the invasive and native ranges in Africa and Asia. Our findings support a hypothesis that an initial invasion from Asia to Djibouti seeded separate incursions to Sudan, Ethiopia, and Yemen before spreading inland, aided by favourable temperature, vegetation cover, and human transit conditions. Insecticide resistance in invasive An. stephensi is conferred by detoxification genes introduced from Asia. These findings, and a companion genomic data catalogue, will form the foundation of an evidence base for surveillance and management strategies for An. stephensi.

genomics↗

bioRxiv2018

Genome-wide gene expression profiling reveals that cuticle alterations and P450 detoxification are associated with pyrethroid resistance in Anopheles arabiensis populations from Ethiopia

BACKGROUNDVector control is the main intervention in malaria control and elimination strategies. However, the development of insecticide resistance is one of the major challenges for controlling malaria vectors. Anopheles arabiensis populations in Ethiopia showed resistance against both DDT and the pyrethroid deltamethrin. Although a L1014F target-site resistance mutation was present in the voltage gated sodium channel of investigated populations, the levels of resistance and biochemical studies indicated the presence of additional resistance mechanisms. In this study, we used genome-wide transcriptome profiling by RNAseq to assess differentially expressed genes between three deltamethrin and DDT resistant An. arabiensis field populations (Tolay, Asendabo, Chewaka) and two susceptible strains (Sekoru and Mozambique).\n\nRESULTSBoth RNAseq analysis and RT-qPCR showed that a glutathione-S-transferase, gstd3, and a cytochrome P450 monooxygenase, cyp6p4, were significantly overexpressed in the group of resistant populations compared to the susceptible strains, suggesting that the enzymes they encode play a key role in metabolic resistance against deltamethrin or DDT. Furthermore, a gene ontology enrichment analysis showed that expression changes of cuticle related genes were strongly associated with insecticide resistance, although this did not translate in increased thickness of the procuticle.\n\nCONCLUSIONOur transcriptome sequencing of deltamethrin/DDT resistant An. arabiensis populations from Ethiopia suggests non-target site resistance mechanisms and pave the way for further investigation of the role of cuticle composition in resistance.

molecular biology↗