Ascaridia (A.) galli is a gastrointestinal nematode that causes significant economic losses in poultry production worldwide. The emergence of anthelmintic resistance and concerns regarding chemical residues have stimulated interest in plant-based alternatives. Cymbopogon nardus essential oil (CNEO) has demonstrated various biological activities; however, its anthelmintic potential against A. galli and the possible underlying mechanisms remain poorly characterised. Herein, CNEO was tested in vitro against adult A. galli worms. Mortality data were analysed by a generalised linear mixed model (GLMM) with binomial error and logit link, with treatment, exposure time and their interaction as fixed effects and replicate as a random factor. CNEO produced concentration- and time-dependent mortality, reaching 100% by 80min at 10% and by 160min at 1% (P<0.001 versus the pooled NaCl control; Cohen’s h≈2.92 at both concentrations). Scanning electron microscopy (SEM) confirmed cuticular roughening, lip distortion and abnormal annulation patterns. Histology of treated worms showed cuticular deformation, fragmentation of cortical and fibrous layers, and disruption of ovarian structures with egg deformation. Predictive molecular docking of the three principal monoterpenoids, citronellal, citronellol and geraniol, against aquaporin (AQP), glutamate‑gated chloride channel (GluCl), nicotinic acetylcholine receptor (nAChR) and Na⁺/K⁺‑ATPase revealed favourable binding energies (ΔG in kcal/mol): citronellal gave -6.2 (AQP), -5.1 (GluCl), -4.5 (nAChR) and -4.8 (Na⁺/K⁺‑ATPase); citronellol gave -6.4, -5.0, -4.6 and -4.7, respectively; geraniol gave -6.6, -5.1, -4.8 and -5.0, respectively. Residue‑level interaction analyses showed that citronellol formed the most diverse contacts at nAChR (including Pi‑alkyl, Pi‑sigma and hydrogen bonds), whereas geraniol consistently exhibited the strongest hydrophobic networks at AQP and Na⁺/K⁺‑ATPase. Importantly, the predicted binding energies of the three monoterpenoids at nAChR (-4.5 to -4.8kcal/mol) are comparable to those of the reference nAChR‑specific drugs levamisole (-5.1) and pyrantel pamoate (-5.4). Furthermore, CNEO exhibits a complementary multi‑target profile that could potentiate or synergise with existing anthelmintics, positioning it may act as a complementary adjuvant candidate. Further, functional validation by bio‑guided fractionation and target‑specific assays is recommended.

To Cite This Article: Atthahirah CW, Hamid PH, Nugroho HA, Wibowo S and Maulydia NB, 2026. Essential oil of Cymbopogon nardus disrupts osmoregulation and cuticle integrity in parasitic nematode. Pak Vet J, 46(7): 1695-1707. http://dx.doi.org/10.29261/pakvetj/2026.163