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

Abstract

Cyathostomins (Strongylida: Cyathostominae) 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 coproculture. The in vitro test was carried out 36 h after the challenge with 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 concentrations lower than 3.9 mg/mL. Therefore, in addition to the uses against other pathogens such as fungi and bacteria, some EOs might attain great importance as an alternative control strategy in the control of nematode eggs.