Nanocarrier‐mediated delivery of dsRNA targeting the ecdysone receptor enables non‐invasive RNAi control of ticks

Ticks are ectoparasites that can transmit zoonotic pathogens, causing significant economic losses worldwide. RNA interference (RNAi) offers a gene-specific alternative to chemical acaricides; however, its application is limited by double-stranded RNA (dsRNA) instability and poor cuticle penetration. Using Haemaphysalis longicornis (H. longicornis) as a model, we identified the ecdysone receptor gene (ECR) as an effective RNAi target. Microinjection of dsECR completely abolished engorgement rate (0%) and reduced body weight by ∼90%. To enable practical delivery, three nanocarrier systems-chitosan (CS), star polycation (SPc), and disulfide-crosslinked chitosan (CS-ss) were developed to improve the stability and uptake of dsRNA. All three nanocarrier systems enhanced dsRNA resistance to ribonuclease (RNase) degradation while exhibiting distinct physicochemical properties: CS-ss formed the smallest nanoparticles (∼175 nm), whereas SPc showed superior surface wettability. All nanocarrier-dsRNA complexes achieved comparable RNAi efficiency under microinjection. In contrast, immersion delivery of naked dsECR was ineffective, whereas SPc-dsECR and CS-ss-dsECR enabled significant ECR silencing, reduced engorgement rate, and decreased body weight. Similar RNAi efficiency levels were validated in Hyalomma asiaticum, supporting the cross-species applicability of this strategy. Notably, SPc-dsRNA exhibited lower contact angles on the tick cuticle, indicating enhanced spreading and suggesting improved penetration efficiency. Collectively, the results of this study demonstrate that nanocarrier encapsulation is effective for immersion-based RNAi control of ticks. SPc provides superior dispersion and surface interaction for consistent delivery, while CS-ss offers the potential for redox-responsive release. The findings establish a scalable and non-invasive RNAi strategy for sustainable tick control.