Potencial in vitro e in vivo de óleos essenciais contra a infecção por Neoechinorhynchus buttnerae em Colossoma macropomum

Abstract

Neoechinorhynchus buttnerae is an acanthocephalan found in the intestine of the tambaqui Colossoma macropomum and is currently the major constraint in the culture of this fish. At high infection rates, this parasite has compromised production, especially in northern Brazil. Thus, the first stage of this study aimed to evaluate the in vitro survival time of N. buttnerae in minimum essential medium of Eagle (EMEM) supplemented with antibiotics, under different maintenance methodologies, in order to propose an alternative protocol for the maintenance of specimens outside the host, which guarantees greater reliability in future tests with anthelmintics. The results of the survival analysis indicated that the use of the MEME medium associated to supplementation with antibiotics and with replacement every two days, significantly prolonged the survival time of the parasites when kept in the temperature range of 24 to 28 ºC. This protocol was adopted in the second stage of this study, which aimed to evaluate the chemical composition as well as the in vitro anthelmintic potential of 11 species of essential oils (OEs) obtained from different medicinal plants, in the control of N. buttnerae, from an experimental design with a control group and nine concentrations of each essential oil, in triplicate, after 2 hours, 6 hours and 24 hours of exposure. There was a reduction in the Effective Concentrations (EC50) values of the essential oils with an increase in exposure time, the lowest values being obtained with the OEs of Mentha arvensis, Lippia grata, Lippia origanoides, Croton cajucara morphotype red, Ocimum gratissimum, Croton cajucara morphotype white and Piper aduncum. As for the in vitro efficacy of N. buttnerae control, all the essential oils were 100% effective within 24 hours. Structural analysis of helminths exposed to OEs suggests that mortality is associated with dissociation of the tegument from the underlying muscle layer, edema in the lacunar spaces with formation of subcutlicle bubbles, body swelling, increased volume of the pseudocelloma and degeneration of the reproductive organs. Therefore, all the essential oils evaluated have potential for the in vivo control of N. buttnerae. The anthelmintic efficacy of L. grata, L. origanoides and O. gratissimum OEs was evaluated in the in vivo control of N. buttnerae in C. macropomum, besides the growth, hematological, biochemical, enzymatic and histopathological parameters. Juveniles of tambaqui naturally infected by N. buttnerae, after 30 days of feeding containing OEs of L. grata (0.86 g kg-1), L. origanoides (0.76 g kg-1) and O. gratissimum (1.03 and 2.06 g kg-1), resulted in 100% survival of the fish, reduction in the intensity and average parasitic abundance and the average percentage of anthelmintic efficacy of OEs was between 43.9 and 62.1%. It should be noted that after the use of OEs of L. grata, L. origanoides and O. gratissimum the morphophysiological parameters indicated the maintenance of organic homostasis in the fish, therefore these OEs are good therapeutic alternatives in the control of acanthocaphalosis in C. macropomum.