Irritancy and spatial repellency efficacy of repellent-treated fabrics against Aedes aegypti (L.) (Diptera: Culicidae) in an excito-repellency system

Mosquito-borne diseases remain a major public health challenge, driving the need for affordable and scalable vector control tools. In this study, we used an excito-repellency system to evaluate the deterrent potential of two low-cost repellent-treated fabrics consisting of Calico (100% cotton) and Jute (hessian), to a standard treated bed net polyester (BNP), against a laboratory strain of Aedes aegypti (L.). Fabrics (15 x 17.5 cm) were treated with six concentrations of transfluthrin and metofluthrin, and five of permethrin, categorized as low and high doses. Chemical retention was assessed using gas chromatography-mass spectrometry (GC-MS), and behavioral avoidance was measured via chamber escape responses over 30 minutes using 60 female mosquitoes per replicate (n = 4). Calico elicited the strongest mosquito escape (OR = 3.12) followed by Jute (OR = 1.74). Transfluthrin (OR = 5.45) produced the most escape whereas low dose treatments resulted in greater escape (OR = 1.23) than high dose applications. Non-contact chambers elicited more escape (OR = 1.87) than the contact test chamber, indicating stronger spatial repellency than irritancy. GC-MS results confirmed fabric-specific chemical retention dynamics: permethrin remained stable across all fabrics and time points, while transfluthrin retention varied significantly between Calico and BNP after 24 h drying. These findings highlight the importance of fabric- insecticide compatibility and the influence of exposure method, dose, and chemical volatility on repellent efficacy. Notably, both metofluthrin-treated fabrics and BNP exhibited pronounced insecticidal effects, suggesting that toxicity may mask repellency--a hypothesis warranting further evaluation at lower concentrations.