Knockdown resistance (kdr) and organochlorine insecticide resistance in malaria vectors: a systematic review
Ebrahim Abbasi, Salman Daliri
Abstract
BACKGROUND: Anopheles albimanus, Anopheles darlingi, Anopheles dirus, and Anopheles punctipennis are key malaria vectors across multiple regions. Insecticide resistance especially to organochlorines poses a major challenge to vector control. While knockdown resistance (kdr) mutations are a well-known resistance mechanism, evidence in these species remains inconclusive. This study systematically reviewed the presence of kdr mutations associated with organochlorine resistance in these four Anopheles species. METHODS: A systematic review was conducted in accordance with PRISMA guidelines. Six international databases PubMed, Web of Science, Scopus, Cochrane Library, ScienceDirect, and Google Scholar were searched up to June 2024. Keywords included "kdr mutation," "organochlorine resistance," "malaria vectors," and related terms. Inclusion criteria focused on studies examining kdr mutations and organochlorine resistance in the four target Anopheles species. The quality of studies was assessed using the STROBE checklist. Five studies met all eligibility criteria and were included. RESULTS: Across the five included studies, no kdr mutations (particularly at codons 1010, 1013, or 1014 in the VGSC gene) were identified in any of the four species. Resistance observed in these mosquitoes was attributed primarily to metabolic mechanisms, including elevated activity of mixed-function oxidases (MFO) and non-specific esterases (NSE), rather than target-site insensitivity. CONCLUSION: Current evidence indicates that kdr mutations do not contribute to organochlorine resistance in An. albimanus, An. darlingi, An. dirus, or An. punctipennis. Metabolic and behavioural resistance mechanisms appear to play a larger role. Given the limited number of studies and gene regions analysed, further research with broader genetic screening is essential to fully understand resistance dynamics in these vectors.