| Summary: | This study evaluated the in vitro and in vivo parasiticidal efficacy of the essential oils of Mentha piperita, Lippia alba and Zingiber officinale on Neoechinorhynchus buttnerae (acanthocephalan) and their effect when used as dietary supplementation on hematological parameters of Colossoma macropomum. For the in vitro assay, the parasites were exposed to five different concentrations (360, 540, 720, 1440, and 2880 mg L−1) of the essential oils diluted in 3% Tween 80, for incubation period of 24 hs observed each 15 min. The essential oil of M. piperita caused mortality of 100 % of the parasites in 2 h in the concentration (540 mg L−1), compared to the essential oils of L. alba and Z. officinale. For the in vivo tests, 210 juvenile tambaqui were used; they were fed for 30 days with either the control diet and experimental diets consisting of supplementation with essential oils: control, M. piperita 0.54 g kg−1 and 2.88 g kg−1, L. alba 1.44 g kg-1 and 2.88 g kg−1, Z. officinale 1.44 g kg−1 and 2.88 g kg−1, in triplicate, resulting in 21 experimental units (10 fish per tank). The anthelmintic activity in the animals treated using diets supplemented with M. piperita at 0.54 and 2.88 g kg−1 were 85.46 % and 70.03 %; with L. alba 1.44 and 2.88 g kg−1 were 67.10 % and 56.93 %, and with Z. officinale 1.44 and 2.88 g kg−1 were 11.70 % and 5.19 %, respectively. Total red blood cells count and thrombocytes were higher in fish treated with M. piperita at 0.54 g kg−1 and Z. officinale at 1.44 g kg−1. The supplementation with essential oil of M. piperita at 0.54 g kg−1 was effective in the control of N. buttnerae and presented better specific growth rate. However, despite these promising results, more research is needed to validate their use in commercial production.
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