Toxicity of Lippia origanoides essential oil in tambaqui (Colossoma macropomum) and its effect against Aeromonas hydrophila

Abstract

The study evaluated the toxicity of Lippia origanoides essential oil (EO) in tambaqui (Colossoma macropomum) and its in vivo activity against Aeromonas hydrophila. Toxicity was tested by tambaqui exposure to 0, 5, 10, 12.5, 15, 17.5 and 20 mg L^-1 of L. origanoides EO for 96 h. The mean lethal concentration (LC₅₀) was 15.2 mg L^-1. After tambaqui exposure to sublethal concentrations of L. origanoides EO (7.6 and 11.4 mg L^-1) for 96 h, only the 7.6 mg L^-1 level caused minor hematologic and biochemical changes that include increase in mean corpuscular volume and decrease in total protein, which did not compromise fish homeostasis. Tambaqui experimentally infected with A. hydrophila had higher survival rate (79.2%) after therapeutic bath with 10 mg L^-1 L. origanoides EO. Therefore, tambaqui exhibits moderate tolerance to L. origanoides EO, and this oil has potential for use in the treatment of tambaqui infected with A. hydrophila.