Efficacy of the essential oils of Aloysia triphylla, Lippia gracilis and Piper aduncum in the control of Piscinoodinium pillulare (Shaperclaus, 1954) in Colossoma macropomum (Cuvier, 1818)

The objectives of this study were to determine the efficacy of essential oils (EO) of Aloysia triphylla, Lippia gracilis and Piper aduncum in the control of P. pillulare in juvenile tambaqui (Colossoma macropomum), as well as the safety of treatment through the analysis of hematological, biochemical and enzymatic values, after application of therapeutic baths. Seven treatments were evaluated, with three repetitions: control, EO of A. triphylla (40 and 50 mg L−1), EO of L. gracilis (20 and 30 mg L−1) and EO of P. aduncum (10 and 20 mg L−1). The fish were exposed to three 15-min baths with the EOs, every 24 h. To assess the physiological state of the fish, hematocrit, number of erythrocytes, hemoglobin, glucose, and total proteins were determined, as well as the activity of the enzymes aspartate aminostransferase (AST), alanine aminostransferase (ALT) and alkaline phosphatase (ALP). The efficacy of the EOs in the control of P. pillulare ranged from 63.8 to 83.8%, with the highest values obtained with the use of EO of P. aduncum. Regarding the hematological and biochemical parameters, no significant differences were observed between treatments with the EOs, although the P. pillulare infection promoted a reduction in hematocrit and hemoglobin values, as well as an increase in plasma glucose and total proteins. There was a significant reduction in ALT values with P. aduncum and A. triphylla EOs compared to L. gracilis EO treatments, but they did not compromise the liver function of fish. Therefore, the use of EOs of A. triphylla, L. gracilis and P. aduncum is clinically safe for the treatment of tambaqui infested by P. pillulare, and the EO of P. aduncum, at a concentration of 20 mg L−1, had the highest efficacy (83.8%) among the oils tested here.