Repellent effects of insecticides against Aedes aegypti: a systematic review.

BACKGROUND: Aedes aegypti is the primary vector of arboviruses, including dengue, Zika and chikungunya, representing a major global public health concern. Owing to the lack of effective vaccines and specific therapeutic options for these infections, vector control remains the main strategy to limit their spread. Traditionally, vector control has relied on extensive use of insecticides combined with the elimination of breeding sites. However, in addition to selecting for insecticide-resistant mosquitoes, concerns have arisen about behavioural effects induced by insecticides, particularly repellency - defined as the ability of a chemical compound to trigger avoidance behaviour in insects, thereby reducing their exposure to treated surfaces. This systematic review aimed to synthesise current knowledge on repellent effects of certain insecticides on A. aegypti. METHODS: A literature search was conducted in the databases Virtual Health Library (BVS), PubMed® and Scientific Electronic Library Online (SciELO), following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A total of 46 original studies published between 1990 and 2023 were included. RESULTS: Altogether, 433 bioassays were analysed, of which 69.8% reported repellent effects. The most common methods used to assess repellency were excito-repellency chambers, HITSS assays and the arm-in-cage test. Pyrethroids were used in 86.6% of repellency assays, followed by organochlorines (9.4%). Regarding the resistance profile of tested mosquito populations, susceptible populations exhibited higher frequencies of contact (92.2%) and spatial (77.3%) repellency behaviours than resistant ones (74.1% and 44.0%, respectively). CONCLUSIONS: Our findings indicate that insecticide-induced repellency is common and may interfere with the effectiveness of chemical control strategies. Nevertheless, studies addressing the underlying molecular and sensory mechanisms involved in repellent perception remain scarce.