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

Abstract

Mosquito-borne diseases remain a major public health challenge, driving the need for affordable and scalable vector control tools. In this study, an excito-repellency system was used to evaluate the contact irritancy and spatial repellency potential of two low-cost repellent-treated fabrics consisting of Calico (100% cotton) and Jute (hessian), and a standard treated bed net polyester (BNP), against a laboratory strain of Aedes aegypti (L.). Fabric swatches (15 x 17.5 cm) were treated with six concentrations of transfluthrin and metofluthrin, and five of permethrin. Behavioral responses were measured via chamber escape over 30 minutes using 60 unfed female mosquitoes per treatment. Chemical retention was assessed using gas chromatography–mass spectrometry (GC-MS). Calico elicited the highest mosquito escape (Odds ratio, OR = 3.12) followed by Jute (OR = 1.74) relative to BNP. Transfluthrin (OR = 5.45) produced the highest escape among insecticides, whereas low dose treatments resulted in more escape (OR = 1.23) than high dose applications. Non-contact chambers elicited more escape (OR = 1.87) than the contact chambers, indicating stronger spatial repellency than contact irritancy. Toxicity was most pronounced with metofluthrin across fabrics (Mortality: OR = 32.27), particulary on BNP which corresponded with reduced escape. GC-MS results showed stable permethrin retention across fabrics, whereas 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. Future studies could investigate chemical interactions between repellents and fabrics to clarify their combined effects.