The low epg reduction obtained with ivermectin indicates the presence of resistant nematodes. This is a common situation in Brazil and elsewhere (Melo et al., 1998; Schnyder et al., 2005; Camurc¸ a-Vasconcelos et al.,2008). The use of E. staigeriana essential oil would be justifiedeven with effectiveness less than 95%, especially in
situations where the synthetic anthelmintic was not recommended, such as on organic farms, in milk-producing animals, or when the cost is not compensatory.
E. staigeriana essential oil was shown in vitro and in vivo to possess anthelmintic activity at the concentrations and dose levels tested. However, its efficacy does
not reach the therapeutically required level of synthetic anthelmintics.
Classes of secondary metabolites found in the current experiment are considered sources of chemical components responsible for a wide range of therapeutic
activities in several medicinal plants.
Further investigation of isolated fractions at different dose levels should be pursued.