Dermocystidium sp. in the gills of farmed Oreochromis niloticus in Brazil.

The genus Dermocystidium is very comprehensive in the host and site of infection, however this is the first report of the occurrence of Dermocystidium sp. in the gills of Nile tilapia. This study was carried out in a fish farming located in the state of Santa Catarina, Brazil. No mortalities were reported in the facility studied and the animals were clinically healthy. During the histopathological analysis of the gills, 8.33% of the fish presented spores of Dermocystidium sp. in the gill tissue. The spores reported herein had a mean length and width of 6.206 x 5.233 µm and a refractile body diameter of 1.965 µm and were studied by histopathology and Transmission Electron Microscopy. This study highlights the importance of a new branchial pathogen in farmed tilapia, as well as to its pathogenic potential, considering the outbreaks of mortalities associated with other fish species.

Three previous recorded species of Dactylogyrus Diesing, 1850 (Monogenea: Dactylogyridae) infecting cultured Carassius auratus in southern Brazil.

The present study aimed to contribute to the monogenean dactylogyrids that occur in C. auratus from an ornamental fish farm in southern Brazil. Samples of goldfish were obtained from a fish farm and the gills were removed and analysed to identify the species of Dactylogyrus to determine the levels of infestation. Three species of Dactylogyrus were found in the gills: Dactylogyrus anchoratus, Dactylogyrus baueri and Dactylogyrus formosus. The most prevalent species was D. baueri [prevalence (P) = 70%, mean intensity (MI) = 2.14 ± 1.21, mean abundance (MA) = 1.5 ± 1.43], followed by D. anchoratus (P = 60%, MI = 1.67 ± 0.81, MA = 1.00 ± 1.05) and D. formosus (P = 30%, MI = 1.66 ± 1.15, MA = 0.5 ± 1.64). Dactylogyrus anchoratus shares morphological characteristics with D. arcuatus by the similarity in shape of the haptor parts. Dactylogyrus baueri shows similarity to D. dulkeiti in relation to the pair of anchors and accessory piece of the male copulatory complex. Dactylogyrus formosus presents an accessory piece with branch and total length of the anchors smaller than D. anchoratus. This study reports the occurrence of D. anchoratus, D. baueri and D. formosus in goldfish cultured in southern Brazil. These monogenean species have been described in cyprinid fishes that have a wide geographic distribution with the result of the dissemination of the host in the world.

Hemato-immunological and biochemical parameters of silver catfish Rhamdia quelen immunized with live theronts of Ichthyophthirius multifiliis.

This study investigated the immunization by intraperitoneal injection (i.p.) (assay I) and immersion bath (assay II) with live theronts of Ichthyophthirius multifillis in Rhamdia quelen and its influence on the hemato-immunological and biochemical parameters. Fish were divided in control (non immunized no challenged); non immunized and challenged with 12,000 theronts/fish; non immunized and challenged with 22,000 theronts/fish; immunized and challenged with 12,000 theronts/fish; immunized and challenged with 22,000 theronts/fish. Six days after challenge, either in the assay I or in the assay II the prevalence of I. multifillis in the gills was higher in non immunized fish (33.33% and 27.77%, respectively). In the assay I showed higher numbers of thrombocytes, leukocytes, lymphocytes, neutrophils and monocytes 20 days after injection and lower numbers after challenge. The immunoglobulin values were higher in fish non immunized. Fish immunized by immersion bath (assay II) showed greater values of catalase (CAT) in the liver (1245.49 U/mgprt) when compared to i.p. (198.79 U/mgprt). The levels of CAT in the liver of fish from the assay II were greater (1738.47 U/mgprt) 14 days after immunization than that observed 21 days after (1114.26 U/mgprt). The vaccination by i.p method showed influence on the hematological parameters. On the other hand, the immersion bath vaccination showed greater influence on the catalase activity in the liver. The results showed that new parameters like total protein, immunoglobulin and antioxidant enzymes could be considered in evaluating the host response to infection.