Preliminary screening of plant essential oils from an oceanic climate zone (NW Spain) for the control of equine cyathostomins

Abstract

Cyathostomins are gastrointestinal nematodes (GIN) that affect equines in many parts of the world. Due to anthelmintic resistance (AR), it is necessary to search for control alternatives. The objective of the study was to carry out a screening of 26 essential oils (EOs) from plants to determine in vitro their action on cyathostomins. Essential oils were obtained by hydro-distillation from leaves, flowers, fruits and seeds of the selected species and used against the eggs of cyathostomins by means of the tests of egg hatching and larval motility inhibition. For each EO, different concentrations were prepared (250, 125, 62.5, 31.3, 15.6, 7.8, 3.9, 2.0, 1.0, 0.5 and 0.24 mg/mL). Oxfendazole at 2.5% mixed with closantel 5% was used as positive control, and PBS served as negative control. Cyathostomin eggs were obtained from feces of infected horses and infective larvae were recovered after de coproculture. The in vitro test was carried out 36 hours after the challenge con the EOs. The highest production of EOs was obtained from leaves of bay, eucalyptus, mallow and basil, as well as from seeds of black pepper, coriander, cinnamon, anise, and peel of orange and cloves, cumin and Lawson’s cypress. The oils extracted from laurel leaves, ground cinnamon, anise, cumin, and coriander seeds had a very high effect on cyathostomins eggs up to doses lower than 3.9 mg/mL. Therefore, in addition to the uses in other species such as fungi and bacteria, the use of EOs in the control of nematode eggs gives greater importance as alternative control.