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This study evaluated the effect of short‐term baths with the essential oils (EOs) of Lippia sidoides, Ocimum gratissimum and Zingiber officinale on the survival, haematological, biochemical and histopathological parameters of native fish tambaqui (Colossoma macropomum), challenged with Aeromonas hydrophila. After challenge, the fish infected with A. hydrophila received therapeutic baths of 60 min, for five consecutive days. Treatments were as follows: challenged and not treated; challenged and treated with 10 mg L−1 of gentamicin; challenged and treated with EO of L. sidoides (2.5 and 5.0 mg L−1); challenged and treated with EO of O. gratissimum (5.0 and 10.0 mg L−1); challenged and treated with Z. officinale EO (5.0 and 10.0 mg L−1). The highest survival rates were 89.5% (fish treated with 5.0 mg L−1 of O. gratissimum EO) and 75.0% (fish treated with 5.0 mg L−1 of L. sidoides EO). Reductions in the haematocrit percentage, haemoglobin and erythrocyte number were observed in fish treated with L. sidoides and Z. officinale EOs compared with control fish. Mild to moderate damage to the liver tissue of fish after challenge and EO treatments were observed. It is suggested that baths containing O. gratissimum and L. sidoides EOs consist in a viable treatment to increase survival rates of C. macropomum infected with A. hydrophila. [ABSTRACT FROM AUTHOR]

In this study, we evaluated the chemical composition and the in vitro anthelmintic efficacy of the essential oils (EOs) of the plants Aloysia triphylla, Adenocalymna alliaceum, Allium sativum, Croton cajucara (white and red morphotypes), Curcuma longa, Lippia gracilis, Lippia origanoides, Ocimum gratissimum, Mentha arvensis, and Piper aduncum against the Acantocephalan Neoechinorhynchus buttnerae. The in vitro viability of worms was observed after 24 h-exposure to nine concentrations of EOs from each plant. Lower EC50 values were obtained for M. arvensis, L. origanoides, L. gracilis, C. cajucara (red and white morphotypes), O. gratissimum, and P. aduncum. All EOs showed 100% anthelmintic efficacy in vitro in 24 h. In regard to damage to the integument of helminths, edema in the lacunar spaces with formation of bubbles in the subcuticle, body swelling, increased volume of the pseudocelomatic cavity and degeneration of the reproductive organs were observed after exposure to A. triphylla OE. [ABSTRACT FROM AUTHOR]