In vitro efficacy of essential oils against Haematobia irritans

The horn fly (Haematobia irritans) infestation in the cattle in Brazil leads to significant economic damage for livestock. The efficacy of many essential oils has been demonstrated in the control of veterinary ectoparasites. This study aimed to evaluate the in vitro efficacy of four essential oils to adult horn fly control. The essential oil from Mesosphaerum suaveolens (L.) Kuntze (Lamiaceae) was extracted by hydro-distillation, while that the water steam distillation method was used to extract the essential oils from Varronia curassavica (Jacq.) Roem. & Schult. (Boraginaceae), Alpinia zerumbet (Pers.) B.L. Burtt & R.M. Sm. (Zingiberaceae) and Psidium guajava L. (Myrtaceae). Afterwards, all the essential oils were analyzed by Gas Chromatography Mass Spectrometry (GC?MS) and Flame Ionization Detector (GC-FID) for determination of their chemical composition. The bioassays in vitro were performed according to the impregnated filter paper methodology. All the essential oils evaluated in this study exhibited efficacy in vitro against H. irritans. The highest mortality of H. irritans was determined by essential oils from A. zerumbet (100%) and M. suaveolens (96.2%) at 50 mg mL-1. In concentration of 100 mg mL-1 V. curassavica and P. guajava essential oils caused the mortality of 99.2% and 82.8%, respectively. The A. zerumbet, M. suaveolens, V. curassavica and P. guajava essential oils showed in vitro efficacy against H. irritans. Further studies with associations and nanoemultions are necessary to increase the efficacy and stability of these essential oils on field conditions.