Rapid Neurotoxicity of Transfluthrin Volatiles and Spatial Repellency of Alternate Deterrents Against Host Seeking Black Flies, Simulium Vittatum (Diptera: Simuliidae)
Year: 2026
Type: preprint
Abstract: Spatial repellants are novel tools that aim to disrupt host seeking behavior in hematophagous insects. Outdoor spatial repellents succeed only when the aerodynamic channel is predictable enough to maintain a behavioral repellent field. Though standardized bioassays are essential for characterizing deterrent mediated behavioral responses, substantial knowledge gaps remain about the practical use of high throughput assays to evaluate repellency in outdoor biting species such as Simulium species. This is particularly relevant within the context of spatial repellent formulations for outdoor use. This study evaluated the comparative spatial repellency, knockdown and lethality thresholds of transfluthrin, permethrin, DEET (N, N diethyl meta toluamide), citronella oil and neem oil against host-seeking adult black flies (Diptera: Simuliidae). Concentration response data obtained (T=15, 30mins,1hr and 24hrs) across different concentration scales (0.001ug-10mg/cm 2 ) were analyzed using a nonlinear regression to four parameter logistic equations to calculate half repellency (EC50), half knockdown (KC50) and half lethality (L50) concentration thresholds respectively. Results revealed that black flies exhibited significant repellency, knock down and lethality rates towards transfluthrin in horizontal orientation compared to DEET, permethrin, citronella and neem oil (χ² = 48.99, df = 32, P = 0.028). Driven by rapid vapor phase, transfluthrin demonstrated unparalleled repellency at a concentration of 0.1ug/cm 2 in horizontal orientation (EC 50 values = 0.0201 μg/cm²) and vertical orientation (EC 50 values = 0.030 μg/cm²) compared to DEET (1h EC50 = 39.72 μg/cm²). 1h KC 50 values revealed rapid knockdown effects (0.0259 μg/cm²) compared to DEET (38.24 μg/cm²) evidenced by rapid progression of neurotoxic hyper excitation in black flies in both orientations. Permethrin showed least repellency nor knockdown rates even at the highest concentrations (10mg/cm 2 ). Compound concentration significantly impacted chemical diffusion dynamics (χ² = 75.85, df = 36, P = 0.000116), revealing that total compound loss through time depends heavily on chemical type. In conclusion, results from this study validates dose dependent spatial repellency of transfluthrin against the outdoor biting insect vector, Simulium vittatum in varied orientation placements using a high throughput repellency assay. This underscores the potential of spatial repellent compounds as a promising novel tool against both vectors of onchocerciasis, Simulium damnosum s.l. and vesicular stomatitis virus, Simulium vittatum .
Source: medRxiv
Institution: University of Georgia
Language: English
Subfield: Plant Science
Domain: Life Sciences
Open Access status: green
Awards: G3659105299, G8999607114
OpenAlex ID: W7223453822