Acaricidal activity of Astragalus polysaccharides nanoemulsion against camel tick, Hyalomma dromedarii

Hyalomma dromedarii (H. dromedarii) is a major ectoparasite of camels in arid regions such as Egypt, where it causes significant economic losses and transmits several zoonotic pathogens. This study evaluated the acaricidal efficacy of a novel, locally prepared Astragalus polysaccharides nanoemulsified formulation (APS-NE) against various developmental stages of H. dromedarii infesting camels. APS-NE was prepared using ultrasonic emulsification and characterized by dynamic light scattering, transmission electron microscopy, and GC-MS, revealing uniform nanoparticle size (30-53 nm), good water solubility, and bioactive constituents including palmitic acid and quercetin derivatives. The formulation exhibited strong biological activity with very low toxicity and a wide safety margin in mice. In vitro bioassays showed a clear concentration-dependent acaricidal effect following short immersion periods: at 2% APS-NE, mortality reached 100% for eggs, larvae, nymphs, and unfed adults. Mortality rates at lower concentrations (0.5-1.5%) ranged from 63.6% to 94.6% in eggs, 33.6% to 84.3% in larvae, 53.3% to 93.6% in nymphs, and 31% to 87% in unfed adults, with larvae being the most susceptible stage. APS-NE also significantly impaired reproductive parameters in engorged females, including reductions in egg production index, egg mass, and hatchability compared to the reference drug. Strong positive correlations were observed between APS-NE concentration and tick mortality, with negative correlations for reproductive metrics. These results highlight APS-NE as a safe, eco-friendly alternative to conventional acaricides for effective H. dromedarii control, supporting integrated tick management strategies.