Insecticide resistance and the role of target-site insensitivity mutations among malaria vectors in China: A systematic review and meta-analysis.

Background: Malaria, which is transmitted by Anopheles mosquitoes (Diptera: Culicidae), remains a critical global public health problem. Vector control interventions, particularly insecticide-based strategies, are pivotal for malaria control and elimination, as the efficacy of these interventions is heavily dependent on the high susceptibility of Anopheles mosquitoes to insecticides. However, insecticide resistance in mosquito vectors poses a considerable threat to the sustainability of these control efforts. Notably, no synthesis data on insecticide resistance have been reported in China in recent decades.

Methods: This systematic review and meta-analysis aimed to assess the mortality rates and frequency of knockdown resistance (kdr) and acetylcholinesterase-1 (ace-1) mutations in Anopheles mosquitoes. The Chinese National Knowledge Infrastructure, Wan Fang, PubMed, Embase, and Web of Science databases were searched from 2000 to 2024 to identify relevant articles. Meta-analysis was performed using R and Stata software.

Results: Thirty articles reporting 30,065 An. sinensis were included. The pooled mortality rate for insecticide resistance was 61% [95% confidence interval (CI): 53-68]. The mortality rates of various insecticides were as follows: dichlorodiphenyltrichloroethane (DDT), 49%; deltamethrin, 47%; malathion, 81%; propoxur, 69%; permethrin, 61%; beta-cyfluthrin, 28%; fenitrothion, 82%; beta-cypermethrin, 48%; cyfluthrin, 59%; and lambda-cyhalothrin, 56%. Moreover, the frequency of knockdown resistance (kdr) to insecticides was 36%, whereas the frequency of acetylcholinesterase-1 (ace-1) resistance was 78%. Kdr genotype analysis revealed that 13% of the reported mosquitoes were homozygote resistant, 13% were heterozygote resistant, and 74% were zygote susceptible. Ace-1 genotype analysis revealed that 42% of the reported mosquitoes were homozygote resistant, 25% were heterozygote resistant, and 33% were zygote susceptible.

Conclusions: Of An. sinensis, 36% had kdr mutations, and 78% had ace-1 mutations. These vectors were resistant to pyrethroid, organochlorine, carbamate, and organophosphate insecticides. To prevent the development of resistance to alternative insecticides, it is critical to target Anopheles mosquitoes with novel chemical insecticides or biocontrol approaches.