Efficiency of Fipronil Nanoparticles against Rhipicephalus sanguineus (Latreille) (Acari: Ixodidae) Ticks on Dogs

Fipronil nanoparticles were formulated and characterized to evaluate their acaricidal efficacy against Rhipicephalus sanguineus (Latreille) ticks infesting dogs. Transmission electron microscopy (TEM) confirmed uniformly dispersed, spherical nano-encapsulated particles ranging from 83.6 to 102.23 nm, demonstrating successful nanoscale formulation. Dynamic light scattering (DLS) indicated a unimodal Gaussian distribution dominated by submicron particles (mean particle size: 739.7 nm intensity-based; PI = 0.25), while zeta potential measurements (12.05 mV) revealed moderate colloidal stability. The acaricidal performance of three concentrations—nano-fipronil 0.125%, nano-fipronil 0.25%, and conventional fipronil 1%—was evaluated on naturally infested dogs. Results showed a concentration-dependent response, with the highest efficacy recorded at 48–72 h post-treatment for nano-fipronil 0.25% (89.61%) and fipronil 1% (94.48%), with no significant difference between them (P < 0.05). Nano-fipronil 0.125% showed moderate efficiency (56.59%). The 0.25% nano-formulation reduced tick numbers comparably to the standard 1% formulation, indicating enhanced biological activity and improved acaricidal effect at a reduced dose. These findings demonstrate the potential of nano-encapsulated fipronil as an effective and concentration-reduced alternative for controlling R. sanguineus ticks.