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This study evaluated the in vitro antiparasitic activity of the essential oils of Lippia alba, L. origanoides and L. sidoides against monogenean parasites of koi carp Cyprinus carpio and its zootechnical performance in net cages. The oils were obtained from the leaves by hydro distillation, and the chemical composition was evaluated via gas chromatography. In vitro assays were performed with each essential oil separately and combined in binary (1:1) and tertiary (1:1:1) mixtures with the Lippia species at 10, 20, 40, 60, 80 and 100 mg L -1 and two control groups (grain alcohol and tank water). To determine zootechnical performance, L. sidoides oil was added to the feed at 0.00 (control), 0.25, 0.50, 0.75 and 1%, in triplicate and with 20 fish per net cage fed for 60 days. The best results in vitro against monogeneans were observed for L. sidoides (40 mg L -1 in 8 min), followed by L. origanoides (40 mg L -1 in 25 min) and L. alba (40 mg L -1 in 4 h). Reductions in weight gain, protein efficiency rate and specific growth rate were observed in diets containing 0.75% of L. sidoides oil in comparison to the control and the 0.25% diet. There were no significant differences in growth, individual mean feed intake, apparent feed conversion and parasitological indices. Based on our results, 0.25% L. sidoides oil showed the best zootechnical performance, but was not effective against koi carp parasites in vivo.

Nile tilapia is an exotic species produced in Brazilian aquaculture. The aim of this study was to constitute a pathological diagnosis in Oreochromis sp. with a noticeable presence in a river in southern Brazil, and to verify the origin of these fish in this natural habitat, an environment with high sanitary precariousness due to discharges of industrial effluents. A total of 30 fish were collected during three sampling events and their health status was assessed by parasitological fauna survey, parasitological indices and histopathological examination of the gills, liver, spleen and kidney. Five species of monogenea were identified infesting gills and stomach: Cichlidogyrus sclerosus, C. halli, C. thurstonae, Scutogyrus longicornis and Enterogyrus cichlidarum; and 4 species of trichodinidae infesting the body surface and gills: Trichodina magna, T. compacta, T. centrostrigeata and Paratrichodina africana. The results showed differences according to the seasonality of the collection, with higher parasite count and larger tissue alterations in summer. Histopathological analysis fluctuated from moderate to severe, but necrosis prevailed in all organs and in all fish, indicating that these fish did not enjoy full health.

This study aimed to evaluate the hematological profile and relative condition factor of naturally parasitized Nile tilapia from 12 fish farms in southern Brazil. A total of 240 fish were collected from four regions of the state of Santa Catarina. They were anesthetized, and the blood was collected by puncturing the caudal vein. Subsequently, the fish were necropsied for parasitological analysis. The results were compared with the Kruskal-Wallis test, and the correlations were verified with the Spearman test (P < 0.05). The parasitological analysis revealed high infestations by Ichthyophthirius multifiliis on the fish gills of the south and west regions. The presence of Trichodina magna and Trichodina compacta was observed in low intensity on the body surface of fish from all facilities. Trichodina spp. was found in high intensity parasitizing the fish gills of northern, Itajaí valley and western regions, nonetheless, in those regions, the presence of Monogenea, Cichlidogyrus sclerosus, and Cichlidogyrus halli, on fish gills was observed. The hematological profile presented altered parameters, featuring monocytosis and thrombocytopenia, possibly associated with high parasitic intensities. The observed correlations suggest that neutrophils and monocytes are directly involved in an organic defense against parasites. Monocytes are mainly targeted in the defense against I. multifiliis.