On 15 October 2026, Tepa Njiguet Gabin Arnaud successfully defended his PhD thesis in Medical Biochemistry at the Faculty of Medicine and Biomedical Sciences of the University of Yaoundé I, earning the distinction of “Très Honorable.”
Dr Arnaud Tepa
His thesis, “Elucidation of the Molecular Basis of the Escalation of Pyrethroid Resistance in Anopheles gambiae in Mangoum, Cameroon,” was supervised by Prof. Constant Pieme (University of Yaoundé I) and Prof. Charles Wondji (Liverpool School of Tropical Medicine, LSTM).
The jury was chaired by Prof. Ndongo Judith épse Torimiro, who commended the quality of the work and praised the longstanding collaboration between CRID and LSTM in training young scientists from Cameroonian universities. Partnerships like this, she noted, build local scientific capacity and generate research that responds directly to pressing public health challenges.
Addressing a Growing Threat to Malaria Control
Pyrethroids are the insecticides used in conventional mosquito nets, one of the most important tools for preventing malaria. In Mangoum, however, mosquito populations have developed extremely high levels of resistance to them. Dr. Tepa set out to understand why, because knowing the molecular mechanisms behind resistance is essential to keeping prevention tools effective and protecting vulnerable communities.
To answer that question, Arnaud Tepa brought together field entomology, laboratory bioassays, genomic sequencing, gene-expression analyses and functional validation experiments, drawing on cutting-edge genomic, molecular biology and bioinformatics approaches.
Key Findings from the study
Conventional nets are losing ground. Mosquitoes showed extremely low mortality when exposed to commonly used pyrethroids, a sign that conventional insecticide-treated nets are becoming increasingly ineffective against local vector populations.
Resistance has many causes working together. The study identified several genetic mutations and detoxification genes that contribute to resistance, including a range of candidate genes that are either permanently overexpressed or switched on when mosquitoes are exposed to pyrethroids. These genes help mosquitoes break down or tolerate the insecticide, allowing them to survive doses that would normally be lethal. Because resistance results from multiple mechanisms acting together rather than a single genetic change, it is all the more difficult to overcome.
PBO nets offer a way forward beside the new generation nets actually deployed. In laboratory assays, piperonyl butoxide (PBO) only partially restored the mosquitoes’ susceptibility to pyrethroids. Even so, next-generation nets containing PBO achieved high mosquito mortality against the resistant Mangoum populations, making them a promising alternative wherever pyrethroid resistance is intense.
Strengthening Resistance Surveillance
Beyond identifying resistance mechanisms, the study generated valuable molecular markers that could be used for future resistance monitoring. These markers can help researchers and public health authorities track the emergence and spread of resistance in mosquito populations and adapt malaria control strategies accordingly. The work also highlights the importance of integrating genomic surveillance into routine vector control programs. By detecting resistance early, countries can make informed decisions about which interventions are likely to remain effective and where alternative tools may be needed.
The findings reinforce the need for continuous monitoring of insecticide resistance, deployment of improved vector control tools, and sustained community engagement around malaria prevention, including the proper and consistent use of insecticide-treated mosquito nets.
Congratulations to Dr. Tepa on this outstanding achievement!
