Óleos essenciais de plantas como alternativa aos fármacos convencionais na produção de peixes

Abstract

The essential oils (EO) obtained from plants are a major source of new molecules and have been studied as alternatives to conventional drugs in the treatment of diseases, as immune response modulators and as new growth promoters in fish. The aim of this study was to evaluate the potential use of different EOs from the plants Ocimum americanum (OA), Ocimum gratissimum (OG), Hesperozygis ringens (HR), Cymbopogon flexuosus (CF) and Melaleuca alternifolia (MA) in the control of diseases, as immunomodulators and as growth promoters in the fish species Rhamdia quelen and Sciaenops ocellatus. The EOs from OA, OG and HR showed weak to moderate activity in vitro against the bacterium A. hydrophila, however, they significantly inhibited the hemolytic activity caused by this bacterium in fish erythrocytes. The EO of OA also presented antiparasitic activity in vitro and in vivo against the monogenean parasite Gyrodactylus sp. The EOs from OA, CF and MA were capable of triggering (in vitro) superoxide anion (O2 -) production in S. ocellatus leukocytes (head-kidney macrophages and/or blood leukocytes). The use of the OA and HR EOs in vivo promoted survival of R. quelen infected with A. hydrophila, as well as showed potential as modulator of the innate immune response in both studied fish species: after exposure through baths (R. quelen) or added to the diet (OA in S. ocellatus). Herbal products such as EOs appear as safe alternatives in fish production because they are natural and biodegradable products, contributing to the reduced use of conventional drugs and pesticides.