Efficacy of therapeutic baths with Piper callosum essential oil against monogeneans of Colossoma macropomum: hematological and histopathological assessments.

As chemotherapeutants used in control and treatment of monogeniosis can cause environmental damage and risks to human health, there is need of compounds alternatives effective and safe to this parasitosis. Essential oils are herbal compounds with good degradability in nature and effectiveness, and resistance absence that can be alternatives to chemotherapeutants. This study aimed to report the first trial on the effects of therapeutic baths with Piper callosum essential oil anti-monogeneans in fish. Colossoma macropomum (tambaqui) were subjected to six baths with 100 mg/L of P. callosum essential oil, each lasting 20 minutes per day (short duration), with 24-hour intervals between baths. Therapeutic baths demonstrated efficacy of 83.6% against monogeneans of tambaqui. Fish submitted to therapeutic baths had reduction statistically significant in the plasma levels of total proteins, similar to the control group exposed to water from culture tank + 70% alcohol. The toxicity of P. callosum essential oil was low as there were no significant blood or histopathological changes that compromised gill function in the treated fish. Due to high efficacy of 100 mg/L of P. callosum essential oil in controlling monogenean infestations, six short therapeutic baths on alternate days may be recommended as anti-monogeneans strategy for tambaqui.