Ovicidal effect of eucalyptus wood vinegar on gastrointestinal nematodes' eggs from sheep

Gastrointestinal nematodes (GINs) significantly impair small ruminant production globally, particularly in tropical regions. Anthelmintic resistance due to the indiscriminate use of synthetic drugs has necessitated the search for sustainable, plant-based alternatives. Eucalyptus wood vinegar (WV), a by-product of biomass pyrolysis, possesses bioactive compounds with potential anthelmintic activity. This study aimed to assess the in vitro ovicidal efficacy of eucalyptus WV and WV derived from co-pyrolysis of eucalyptus wood with Origanum majorana (marjoram) against eggs of GINs from naturally infected sheep.

WV samples were produced through controlled pyrolysis and refined through sequential vacuum distillation. Egg hatchability tests were performed using five WV concentrations (0.3125%-5% g/100 mL), with thiabendazole as a positive control and distilled water as a negative control. Egg counts, species identification, and scanning electron microscopy (SEM) were conducted to evaluate structural changes. The chemical compositions of the WVs were characterized using gas chromatography-mass spectrometry (GC/MS).

Both WVs exhibited significant ovicidal activity, with eucalyptus WV achieving 97% inhibition at 1.25%, and the marjoram-enriched WV reaching 100% inhibition at 5%. GC/MS analysis revealed the presence of phenolic compounds, furfural, thymol, and eucalyptol, the latter two being exclusive to the marjoram formulation. SEM micrographs confirmed morphological deformations in treated eggs, including loss of symmetry and membrane integrity. The synergistic interaction among bioactive components, particularly thymol, eucalyptol, and furfural, is proposed as the mechanism enhancing ovicidal activity.

Eucalyptus WV, particularly when enriched with O. majorana through co-pyrolysis, exhibits potent ovicidal effects against GINs in sheep. These findings support the potential use of WVs as eco-friendly anthelmintic alternatives in integrated parasite management strategies for small ruminants.