Ticks and tick-borne diseases (TTBDs) pose significant global health challenges. Essential oils (EOs) have emerged as promising alternative to synthetic chemicals, but their volatile nature, low stability, and exposure to extreme conditions limit their efficacy. Encapsulation of phytochemicals/essential oils in suitable polymers is a potential solution. In this study, the acaricidal activity of chitosan (CS) encapsulated Mentha piperita essential oil (MPEO) against the cattle tick, Rhipicephalus (R.) microplus along with its inhibitory effect on acetylcholinesterase (AChE) was evaluated. Briefly, MPEO was encapsulated in CS nanoparticles (NPs) using emulsification/ionic gelation method, these formulated NPs were characterized thoroughly with the help of encapsulation efficiency percentage (EE%), loading capacity percentage (LC%), zeta analysis, Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and Thermogravimetric Analysis (TGA). The acaricidal efficacy of CS/MPEO NPs was evaluated through prolonged Larval Packet Test (LPT) and climbing repellent bioassay. CS/MPEO NPs with a 1:1 (CS:EO) w/v ratio exhibited the best characterization results such as EE% (98.65), LC% (25.5), average size (293.1nm) and zeta potential as 28mV. Furthermore, the CS/MPEO NPs showed superior acaricidal efficacy, achieving 100% larval mortality at the highest concentration (4mg/mL) by day 7 (LC₅₀=0.126, LC₉₀=1.314), whereas non-encapsulated MPEO revealed decreasing efficacy over time, i.e. 6% mortality by day 7 (LC₅₀=63.269, LC₉₀=614.591). Climbing repellent assay (CRA) exhibited similar trend i.e. encapsulated MPEO showed the highest repellence, reaching 100% at 4mg/mL after 6 hours of exposure and MPEO revealed decreasing repellence over time with 15.3% after 6 hours. Nanoformulation exhibited potent AChE inhibitory activity. Stability analysis after 30 days showed that NPs stored at 4°C had a better characterization results (average size 315.7±1.17nm and ZP 26±0.577mV) compared to those stored at room temperature (405.3±0.75nm, 22.7±0.98mV). This study provides the strong evidence of the larvicidal as well as repellent activity of nanoencapsulated MPEO against R. microplus, offering an eco-friendly alternative for tick control.

To Cite This Article: Ahmad S, Oneeb M, Lateef M, Ijaz M, Siddique MI and Nawaz S 2025. larvicidal and repellent effects of nano-encapsulated mentha piperita essential oil against rhipicephalus microplus. Pak Vet J. http://dx.doi.org/10.29261/pakvetj/2025.275