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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., Competing Interests: Conflict of interestThe authors declare that they have no conflict of interest., (© Indian Society for Parasitology 2019.)

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.

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., Competing Interests: Conflict of interestThe authors declare that they have no conflict of interest.

The toxicity of formalin on Cyprinus carpio var. koi and its anti-parasite effects against Dactylogyrus minutus (Monogenea) in in vitro tests is analyzed. Specimens of D. minutus were submitted to eight concentrations of formalin: 50, 75, 100, 125, 150, 175, 200, 250 mg L -1 , in triplicate. Concentrations of formalin 100, 150 and 200 mg L -1 were then tested to determine the median lethal concentration of 50% of the fish per immersion bath. Fish behavior was also observed during the first 6 h of exposure. The 200 mg L -1 concentration was the most rapid efficacy for D. minutus , killing all parasites in 16 min. All parasites were killed in 47 min at concentration 100 mg L -1 . Concentration 200 mg L -1 was the most lethal for fish in less than 24 h exposure, with 24 h LC 50 at 135.44 (119.78-153.14) mg L -1 . The therapeutic index was 2.05-30 min and 1.15-16 min. A short bath (1 h) is recommended in koi carp with a minimum concentration of 75 mg L -1 of formalin, not exceeding 100 mg L -1 for treatment against D. minutus., Competing Interests: The authors declare that they have no conflict of interest.All procedures were performed following protocols by the Ethics Committee of the Federal University of Santa Catarina (CEUA/UFSC/PP00928).

The capsalid monogenean Neobenedenia melleni is known as a lethal pathogen for captured marine teleost ornamental fish, if left untreated. This study reports the occurrence of N. melleni parasitizing four species of ornamental reef fish imported into Brazil and maintained in quarantine: Arabian angelfish (Pomacanthus asfur ), yellowbar angelfish (Pomacanthus maculosus), regal angelfish (Pygoplites diacanthus), and bluecheek butterflyfish (Chaetodon semilarvatus). Ten days after the beginning of quarantine, some fish showed behavioral alterations, such as irritability, and corneal opacity, which were rapidly diagnosed to be caused by monogenean parasites by body surface scraping. The fish from the same batch were treated with two applications of 2 mg L-1 praziquantel each at an interval of four days. Seven days after the first treatment, the mucus surface of the fish was re-examined, which did not reveal the parasites presence being delivered for commercialization.

Several environmental parameters may influence biological processes of several aquatic invertebrates, such as the Monogenea. Current analysis investigates oviposition, hatching success and infestation of Aphanoblastella mastigatus, a parasite of the silver catfish Rhamdia quelen at different temperatures (~ 24 and 28 °C) and salinity (by adding sodium chloride to water, at concentrations 0, 5 and 9 g/L) in laboratory. There was no significant difference in oviposition rate and in A. mastigatus infestation success at 24 and 28 °C. On the other hand, the concentration 9 g/L of sodium chloride in the water impaired the parasite's survival and the viability of the eggs. Results show that its usage is efficient as a possible prophylactic treatment. Eclosion rate of A. mastigatus's eggs was significantly higher at 28 °C, although it was significantly less from 5 g/L. Two oviposition peaks (06h15 and 18h15) occurred during a 24-hour period, or rather, during the highest variations in luminosity. Further studies are recommended with greater temperature intervals and more intense experimental infestations to verify the effects of temperature in the life span and infestation success of A. mastigatus.

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., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

This study evaluated the correlation of hematological parameters with the mean abundance of the monogenean helminth Rhabdosynochus rhabdosynochus in Centropomus undecimalis reared at different temperatures and salinities. The experimental conditions were: 28 °C/0 ppt (parts per thousand); 28 °C/15 ppt; 28 °C/32 ppt; 25 °C/0 ppt; 25 °C/15 ppt; and 25 °C/32 ppt. The prevalence was 100.0% in fish at 28 °C/15 ppt, 28 °C/32 ppt and 25 °C/15 ppt, which was significantly different (p < 0.05) from those at 25 °C/32 ppt. The red blood cell (RBC) count, hematocrit and total leukocyte (WBC) count were significantly higher in fish at 28 °C/15 ppt and 28 °C/32 ppt. The mean abundance of R. rhabdosynochus, hematocrit and RBC showed positive correlations (P < 0.05) with temperature (ρ= 0.3908; ρ= 0.4771 and ρ = 0.2812). Mean abundance showed negative correlations with hemoglobin (ρ= -0.3567) and mean corpuscular hemoglobin concentration (MCHC) (ρ = -0.2684). No correlation between abundance and salinity was detected among the experimental conditions (ρ = -0.0204). The low numbers of monogeneans recorded (min -1 and max -33) explain the few changes to fish health. This suggests that these experimental conditions may be recommended for development of rearing of C. undecimalis in Brazil, without any influence or economic losses from R. rhabdosynochus.

This study evaluated for two years the haematological parameters and the occurrence of gill parasites in silver catfish Rhamdia quelen, farmed in the state of Santa Catarina, southern Brazil. Between March 2010 and January 2012, a total of 137 fish were caught in a fish farm to compare the haematological and parasitological analysis, during hot and cold seasons. Simultaneously, water quality parameters were measured in the pond to analyze the relationship between environmental conditions and haematology and parasitism. During the hot season, there was an increase in water temperature, electrical conductivity and ammonia followed by a decrease in dissolved oxygen, pH, transparency and alkalinity. Two species of Monogenea were observed in the gills, Aphanoblastella mastigatus (Dactylogyridae) and Scleroductus sp. (Gyrodactylidae). Additionally, during this season, there was a significant increase (p<0.05) in the mean intensity of infection by Monogenea, as well as total leukocytes number, thrombocytes and lymphocytes, and a reduction in monocytes. The changes might be caused by parasitism and/or environmental variations between seasons.