Ocimum micranthum essential oil as a sustainable phytotherapeutic alternative against Haemonchus contortus

This study is the first to evaluate the anthelmintic activity of Ocimum micranthum essential oil against Haemonchus contortus. The oil was chemically characterized using gas chromatography-mass spectrometry. Anthelmintic activity was assessed using the egg hatching test (EHT), larval development test (LDT), larval migration inhibition test (LMIT), and adult worm motility test (AWMT) against a multidrug-resistant H. contortus isolate. Following AWMT, oil-induced morphological and ultrastructural alterations were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Eugenol was the major oil component (78.44%). The oil exhibited anthelmintic activity in all assays, with EC50 values of 0.19 (EHT), 0.031 (LDT), 0.63 (LMIT) and 0.046 (AWMT) mg/mL. At 0.25 mg/mL, complete inhibition of adult motility was observed at the first evaluation time point (3 h post-exposure). SEM revealed damage to the cuticle, buccal capsule, and vulvar flap, whereas TEM demonstrated alterations in internal tissues. Ocimum micranthum essential oil was effective against H. contortus eggs, larvae, and adults. Therefore, further studies evaluating its toxicological safety and efficacy in small ruminants are required to validate its potential as an anthelmintic.