Edsandra Campos Chagas

The use of natural products with antimicrobial activity is an effective and sustainable alternative for the prevention, treatment, and/or control of diseases in aquaculture. The objective of this study was to determine the chemical composition and antimicrobial activity of nine essential oils (EOs) against strains of Aeromonas jandaei and Aeromonas hydrophila isolated from tambaqui (Colossoma macropomum). Essential oils were obtained by hydrodistillation and their composition by gass chromatography coupled with mass spectrometry. Antimicrobial activity of the nine essential oils was evaluated based on the Minimum Inhibitory Concentration (MIC), using the microdilution method, and Minimum Bactericidal Concentration (MBC). The major components identified in EO of Croton sacaquinha, Cymbopogon nardus, Curcuma longa, Lippia origanoides, Mentha arvensis, Ocimum basilicum, Ocimum micranthum, Piper hispidum e Piper marginatum were β-selinene (14.5%), geraniol (53.3%), ar-turmerone (30.2%), carvacrol (43.3%), menthol (88.5%), methyl chavicol (33.9%), piperitone oxide (36.2%), γ-terpinene (37.1%) and δ-3-carene (13.1%), respectively. The EOs of L. origanoides (9.2 mg·mL−1), C. nardus (10 mg·mL−1), M. arvensis, and P. marginatum (15 mg·mL−1) exhibited the most pronounced antimicrobial activity, whereas all essential oils tested demonstrated bactericidal activity against Aeromonas strains.

The current study investigated the use of different concentrations of the essential oil of Zingiber officinale (EOZO) in the transport water of Astyanax lacustris by evaluating the behavioral responses of the fish, water quality, gill histopathology and residues in the fillet after transport. Four hundred juvenile A. lacustris (1.99 ± 0.72 g) were randomly distributed in 20 plastic bags, 20 fish each, with 4 L of water and 2/3 of pure oxygen. Five treatments were applied: control and four concentrations of EOZO (5, 10, 15 and 20 µL L-1), with four replicates each in a completely randomized design. The bags were sealed and shaken periodically during a simulated 2-h transport. Water quality variables were measured before and after transport, while fish survival was recorded, and gill and muscle samples were collected, at different times after transport. Gill histopathology was analyzed to detect tissue alterations and muscle (fillet) residues were quantified. The use of low concentrations of EOZO during transport of A. lacustris was effective at sedating the fish, ensuring survival. The histopathological changes observed in the gills of fish transported with 5 and 10 µL L-1 of EOZO were reversible. Furthermore, EOZO preserved water quality, with an observed reduction in ammonia levels for animals transported with 10 µL L-1. Although small histopathological changes were caused to the gills, EOZO residues in fillets were minimal and disappeared quickly (in less than 12 h). Therefore, the use of 10 µL L-1 of EOZO in the transport water of A. lacustris is recommended.

The aim of this study was to evaluate the effects of the dietary supplementation Ocimum gratissimum essential oil (EO) on pacu (Piaractus mesopotamicus) intestinal microbiota and morphometry. In this study, juveniles of P. mesopotamicus were fed with diets supplemented with 0.5 and 1% of Ocimum gratissimum EO for 30 days. At the end of this period, the intestinal microbiota of the pacus was relatively quantified through qPCR, and the intestinal morphometry was evaluated using histometric methods. O. gratissimum EO feeding supplementation at 1% significantly altered the intestinal microbiota of juvenile pacus, resulting in higher relative quantification of bacteria from the genera Enterococcus and Bacillus when compared to 0.5% and control groups. O. gratissimum EO feeding supplementation presented no effects in intestinal morphometry. Our results suggest that the feeding supplementation of P. mesopotamicus with O. gratissimum at 1% concentration during 30 days modulates the intestinal bacterial populations but do not cause any changes in intestinal morphometry.

This study evaluated the anesthetic and sedative effects of the essential oil of Zingiber officinale (EOZO) on juvenile pacu (Piaractus mesopotamicus). Experiment 1 evaluated concentrations of 0, 50, 100, 200 and 400 mg L^-1 EOZO for times of induction and recovery from anesthesia. Furthermore, hematological responses and residual components of EOZO in plasma were determined immediately after anesthesia. Experiment 2 evaluated the effect of 0, 10, 20 and 30 mg L^-1 EOZO on water quality, blood variables and residual components of EOZO in plasma and tissues (muscle and liver) immediately after 2 h of transport. Survival was 100%. The three main compounds of EOZO [zingiberene (32.27%), β-sesquiphellandrene (18.42%) and β-bisabolene (13.93%)] were observed in animal plasma and tissues (muscle and liver) after anesthesia and transport, demonstrating a direct linear effect among the evaluated concentrations. The concentration of 200 mg L^-1 EOZO promoted surgical anesthesia of pacu and prevented an increase in monocyte and neutrophil levels, yet did not alter other hematological parameters. The use of 30 mg L^-1 EOZO has a sedative effect on juvenile pacu, thereby reducing oxygen consumption during transport. Furthermore, the use of 30 mg L^-1 EOZO in transport water prevented an increase in hemoglobin and hematocrit, with minimal influences on other blood variables.

The tambaqui (Colossoma macropomum) is a species of great economic importance for fish farming in the Brazilian Amazon, and acanthocephaliasis caused by Neoechinorhynchus buttnerae (Golvan 1956) represents an obstacle to its production due to it causing severe morphological damage to the intestinal mucosa, thus impairing the absorption of nutrients and causing weight loss in the fish. Therefore, the establishment of in vitro protocols for evaluation of anthelmintic drugs is the first step to development of effective measures for in vivo control of this endoparasite. The present study evaluated the in vitro survival of N. buttnerae maintained in Eagle’s minimum essential medium under different culture conditions. Three assays were carried out to evaluate whether temperature, supplementation with the antibiotics penicillin and streptomycin, and culture medium replacement or no replacement would influence the motility and morphology of the acanthocephalans. The results of the Kaplan-Meier analysis indicated that the use of culture in minimum essential medium together with penicillin and streptomycin prolonged the parasite’s survival when kept at temperatures of 24 °C or 28 °C. We describe herein for first time an alternative protocol that is ideal for the in vitro culture of N. buttnerae. As such, this protocol ensures greater reliability in further in vitro studies with N. buttnerae.

The aim of this study was to determine the acute toxicity of the essential oils (EOs) of Aloysia triphylla, Lippia gracilis and Piper aduncum in juvenile tambaqui (Colossoma macropomum), and evaluate the possible histopathological alterations in their gills. For the acute toxicity tests, juvenile tambaqui (n=24/treatment) were distributed in six treatments with three replicates, which comprised the control and five EO concentrations of A. triphylla (60, 80, 100, 120 and 140 mg L^-1), L. gracilis (35, 40, 45, 50 and 55 mg L^-1) and P. aduncum (42.5, 45, 47.5, 50 and 52.5 mg L^-1), with an exposure period of 4 h. The mortality rate and severity of damage to the tambaqui gills were proportional to the increase in the concentration of the EO, with LC₅₀-4 h values estimated at 109.57 mg L ^-1 for A. triphylla, 41.63 mg L ^-1 for L. gracilis and 48.17 mg L ^-1 for P. aduncum. The main morphological damages observed in the gills of the tambaqui exposed to the three EOs, were Grade I: hypertrophy and hyperplasia of lamellar epithelial cells, lamellar fusion, epithelial detachment, capillary dilation and constriction, proliferation of chloride cells and mucosal cells and edema; in low frequency Grade II damage as epithelial rupture and lamellar aneurysm. Necrosis (Grade III damage) was observed only in gill lamellae exposed to P. aduncum EO (47.5, 50.0 and 52.5 mg L^-1). Concentrations of EOs below LC₅₀-4 h can be used sparingly, for short periods of exposure for the treatment of diseases in tambaqui breeding.

This study aims to report the occurrence of two important parasites in farmed tambaqui Colossoma macropomum in the state of Tocantins, the acanthocephalan Neoechinorhynchus buttnerae and the dinoflagellate protozoan Piscinoodinium pillulare, also suggesting the main treatments to control them. The fish sampled for the study were infected by N. buttnerae, and P. pillulare, with prevalence from 100% and mean intensity from 51.4 to 354,264, respectively. This was the first report on the occurrence of such parasites in C. macropomum in the state of Tocantins. We emphasize the need to adopt good farm management and biosecurity practices to prevent pathogenic agents to enter or leave a property. Reported treatments with synthetic and natural products with positive results are also suggested to treat against those parasites in farmed C. macropomum.