First report of Myxobolus sp. infection in the skeletal muscle of Neotropical freshwater fish Piaractus mesopotamicus.

Although there are several reports of Myxobolus species infecting the somatic muscle of teleost fish, species of this genus have not been described parasitizing the muscle tissue of pacus, Piaractus mesopotamicus. This study presented the first report of natural infection by Myxobolus sp. in the skeletal muscle of pacus reared in intensive system. Twenty-one fish (±142.2 g; ±23.1 cm) were captured (April 2013) from an intensive fish farm in São Paulo State, southeast Brazil. Spores of Myxobolus sp. were contained within plasmodia and showed oval morphology with the apical portion slightly pyriform and two polar capsules pyriform retaining the same ratio to each other. In the histopathological study, the skeletal muscle do not present signs of inflammation. The integrity of myofibrils within the infected fibers showed some degree of degeneration, with partial loss of myofibrillar details and striations. Spores were found infecting the skeletal muscle of 18 fish (85.7%). Finally, the high prevalence of Myxobolus sp. infection in the skeletal muscle of P. mesopotamicus and the absence of macroscopic lesions in the muscle tissue indicate the necessity of more meticulous examinations during the health management in the rearing system and at slaughter of pacus to ensure best quality of meat.

Parasitic infections in ornamental cichlid fish in the Peruvian Amazon.

The aim of this study was to evaluate the prevalence and seasonal distribution of the main parasite species in Amazonian ornamental cichlids that affect their trade. The study was conducted from August 2007 to September 2009. We sampled 3042 specimens from 9 different species, of which 9.47% had at least one type of external parasite. 81.25% of the cases occurred in the dry season. Crenicichla anthurus (28.57%) was the most parasitized, followed by Aequidens diadema (26.32%), Pterophyllum scalare (22.69%), Cichlasoma sp. (9.52%), Apistogramma sp. (3.88%) and Symphysodon aequifasciatus (3.66%). Monogenea was the most abundant group of parasites, occurring in 66.67% of the cases, of which 96.88% occurred in the dry season. This parasite infested 95.68% of Pterophyllum scalare, 76.67% of Apistogramma sp, 33.33% of Cichlasoma sp. and 23.81% of Symphysodon aequifasciatus cases. Ichthyophthirius multifiliis infested 100% of Aequidens diadema, 76.19% of Symphysodon aequifasciatus, 66.67% of Cichlasoma sp, 41.67% of Crenicichla anthurus and 23.33% of Apistogramma sp cases. Myxosporidia infested 58.33% of Crenicichla anthurus. Trichodina infested 4.32% of Pterophyllum scalare. The prevalence of these parasites is related to the season, preferred habitat, fish behavior, individual susceptibility and handling of animals during transportation by fishermen.

Expression of cellular components in granulomatous inflammatory response in Piaractus mesopotamicus model.

The present study aimed to describe and characterize the cellular components during the evolution of chronic granulomatous inflammation in the teleost fish pacus (P. mesopotamicus) induced by Bacillus Calmette-Guerin (BCG), using S-100, iNOS and cytokeratin antibodies. 50 fish (120±5.0 g) were anesthetized and 45 inoculated with 20 µL (40 mg/mL) (2.0 x 10(6) CFU/mg) and five inoculated with saline (0,65%) into muscle tissue in the laterodorsal region. To evaluate the inflammatory process, nine fish inoculated with BCG and one control were sampled in five periods: 3rd, 7th, 14th, 21st and 33rd days post-inoculation (DPI). Immunohistochemical examination showed that the marking with anti-S-100 protein and anti-iNOS antibodies was weak, with a diffuse pattern, between the third and seventh DPI. From the 14th to the 33rd day, the marking became stronger and marked the cytoplasm of the macrophages. Positivity for cytokeratin was initially observed in the 14th DPI, and the stronger immunostaining in the 33rd day, period in which the epithelioid cells were more evident and the granuloma was fully formed. Also after the 14th day, a certain degree of cellular organization was observed, due to the arrangement of the macrophages around the inoculated material, with little evidence of edema. The arrangement of the macrophages around the inoculum, the fibroblasts, the lymphocytes and, in most cases, the presence of melanomacrophages formed the granuloma and kept the inoculum isolated in the 33rd DPI. The present study suggested that the granulomatous experimental model using teleost fish P. mesopotamicus presented a similar response to those observed in mammals, confirming its importance for studies of chronic inflammatory reaction.

Acute toxicity by water containing hexavalent or trivalent chromium in native Brazilian fish, Piaractus mesopotamicus: anatomopathological alterations and mortality.

This study evaluated the toxicity of hexavalent and trivalent compounds of chromium to the pacu, Piaractus mesopotamicus, in acute exposures of 96 h through mortality and histopathological responses. Hexavalent potassium dichromate was more toxic than trivalent compounds of chromium chloride, chromium oxide and chromium carbochelate. Sufficient mortalities occurred only with potassium dichromate to yield an LC50 value at 124.2 mg L(-1). Hexavalent chromium caused reversible and irreversible lesions, which may affect organ functionality. Histopathological evaluation showed that trivalent chromium caused lesions of lower severity. Pacu subjected to different concentrations of chromium carbochelate showed no histopathological changes in the kidneys, liver, skin and gills, being similar to those of the control fish. Among the three sources of Cr(3+), only chromium chloride at 200 mg L(-1) resulted in mortality, which reached 100 % within the first 18 h. These findings confirm that trivalent chromium, when administered within recommended levels, may be used safely in aquaculture.

Acute aerocystitis in Piaractus mesopotamicus: participation of eicosanoids and pro-inflammatory cytokines.

A total of 360 pacus (Piaractus mesopotamicus) were used to study vascular permeability (VP) and inflammatory cell component (CC) in induced aerocystitis in P. mesopotamicus through inoculation of inactivated Aeromonas hydrophila, and the effect of steroidal and nonsteroidal anti-inflammatory drugs. It was observed that after inoculation of A. hydrophila, the maximum VP occurred 180 min post-stimulus (MPS). Pretreatment with anti-inflammatory drugs inhibited VP, and the inhibitory effect of dexamethasone was seen earlier than the effects caused by meloxicam and indomethacin. Inoculation of the bacterium caused a gradual increase in the accumulation of cells, which reached a maximum 24 h post-stimulus (HPS). Pretreatment with dexamethasone, indomethacin and meloxicam reduced the accumulation of lymphocytes, thrombocytes, granulocytes and macrophages. There was no significant difference between the different doses of the drugs tested. The results suggest that eicosanoids and pro-inflammatory cytokines participate in chemical mediation in acute inflammation in pacus.

First record of Tuxophorus caligodes (Siphonostomatoida, Tuxophoridae) in sea-farmed cobia, Rachycentron canadum, in Brazil.

The cobia is the only representative of the Rachycentridae family and, because of its zootechnical qualities, production of this fish has been implemented in several countries, such as the United States, Mexico and Brazil. Tuxophorus caligodes is a widespread parasite of marine fish worldwide. For the present report, 15 juvenile cobias were collected from net cages on a fish farm in Ilhabela, state of São Paulo, Brazil, in the winter of 2011. The fish were sacrificed by means of cerebral concussion, and then weighed (280 ± 70.5 g) and measured (27 ± 1.97 cm). After external examination under a stereomicroscope, ectoparasites present on the body surface were collected, fixed and processed for identification. Out of the 15 fish examined, two were parasitized with Tuxophorus caligodes, thus indicating a prevalence of 13.3%. This is the first report of Tuxophorus caligodes in cobias in Brazil.

Inflammatory responses of Nile tilapia Oreochromis niloticus to Streptococcus agalactiae: effects of vaccination and yeast diet supplement.

This study evaluated the effects of dietary supplementation with 0.3% Saccharomyces cerevisiae yeast cell wall and of vaccination against Streptococcus agalactiae on the cellular component of acute inflammation induced in the coelomic cavity of Nile tilapia Oreochromis niloticus and on survival of the fish after challenge. A total of 84 tilapia of mean (±SD) weight 125.0 ± 1.5 g were distributed among twelve 310 l fiberglass tanks according to a 2 × 2 × 3 factorial design in the following manner: with and without supplementation; 2 stimulations (oily solution without S. agalactiae vaccine and vaccination); 15 d later all fish were intracoelomically challenged with 108 CFU ml-1 of a homologous strain of S. agalactiae, and evaluated after 6, 24 and 48 h, with 7 replicates. The fish received the non-supplemented or supplemented diet for a total of 77 d. The vaccination was performed on the 60th day, intracoelomically, as a single injection of 0.5 ml of the vaccine containing 108 CFU ml-1. Fifteen days later, all the fish were challenged with S. agalactiae by means of an intracoelomic inoculation of 108 CFU ml-1. No mortality was observed among the supplemented fish. The fish that were fed the non-supplemented diet and immunized with the bacterium presented a mortality rate of 28.5%. Among the non-supplemented and non-immunized fish, the mortality rate was 38.09%. Supplementation, in both vaccinated and non-vaccinated fish, induced larger accumulations of thrombocytes, lymphocytes and macrophages at the inflammatory focus. The results suggest that supplementation with 0.3% yeast cell wall, in both vaccinated and non-vaccinated fish, improved the inflammatory response of the fish and protected against the challenge. Vaccination increased the defense response, but the effect was stronger when associated with supplementation with S. cerevisiae.

Histopathology of gills of Piaractus mesopotamicus (Holmberg, 1887) and Prochilodus lineatus (Valenciennes, 1836) infested by monogenean and myxosporea, caugth in Aquidauana River, State of Mato Grosso do Sul, Brazil.

A histological analysis was conducted on the gills of 15 Piaractus mesopotamicus and 19 Prochilodus lineatus specimens collected between April and November 2004 from the Aquidauana River, State of Mato Grosso do Sul, Central-West Brazil, to describe the anatomopathological characteristics of the gills of these freshwater fish. Gill samples were fixated in 10% buffered formalin and processed following histological routine procedures. The histological examination of the gills of P. mesopotamicus revealed intralamellar monogenean and mixosporean cysts of Henneguya piaractus at several developmental stages over the entire (basal, median and distal) lamella. Intraepithelial cysts caused lamella dilation and deformity of adjacent lamellae. In P. lineatus gills, monogenean cysts were detected. In both host species, hyperplasia of the gill epithelium and structural disorganization of secondary lamellae was seen diffusely in the gills, leading to fused lamellae in the gills. In few cases, there was found mononuclear inflammatory cells and hemorrhagic focal points distally in the lamellae.

[Praziquantel, levamisole and diflubenzuron in the control of Dolops carvalhoi (Crustacea: Branchiura) and Anacanthorus penilabiatus (Monogenea: Dactylogyridae) in Piaractus mesopotamicus Holmberg, 1887 (Osteichthyes: Characidae)]. / Praziquantel, levamisol e diflubenzuron on controle de Dolops carvalhoi (Crustacea: Branchiura) e Anacanthorus enilabiatus (Monogenea: Dactylogyridae) em Piaractus mseopotamicus Holmberg, 1887 (Osteichthyes: Characidae).

This assay evaluated the control efficacy of diflubenzuron, praziquantel and levamisole added to the diet of pacu (Piaractus mesoptamicus) infected with Anacanthorus penilabiatus and Dolops carvalhoi. 19 water tanks of 300 L capacity were utilized with 28 fish in each one. The treatments were made by mixing the active principles in the diet. The experiment was evaluated in four harvests done 1 day before and 3, 7 and 15 days after the treatment. The medicated feeding was applied for 7 days. The results of efficacy suggest that the diflubenzuron alone or associated with levamisole and praziquantel was efficient against the crustacean D. carvalhoi and the efficacy in the 3, 7 and 15 days evaluations ranged from 96.2 to 100%. Against the monogenean the drugs did not present efficacy. The results suggest the use of diflubenzuron for the control of D. carvalhoi in captive fishes in special conditions.

Leukocyte and thrombocyte reference values for channel catfish (Ictalurus punctatus Raf), with an assessment of morphologic, cytochemical, and ultrastructural features.

BACKGROUND: Hematology tests are useful to evaluate physiologic disturbances in fish and can provide important information for the diagnosis and prognosis of disease. OBJECTIVES: The primary purpose of this study was to define reference intervals for thrombocytes and leukocytes in healthy channel catfish (Ictalurus punctatus). In addition, the morphologic, cytochemical, and ultrastructural features of blood cells were assessed. METHODS: Blood samples (0.5 mL) were collected into EDTA from 40 clinically healthy catfish on a commercial fish farm in Jaboticabal, Brazil. Thrombocyte, total WBC, and differential WBC counts were determined and reference intervals were calculated as the 25-95th percentiles of data. Thrombocyte and leukocyte morphology was assessed in blood smears stained with May Grünwald-Giemsa-Wright and ultrastructurally by transmission electron microscopy. Cytochemical staining patterns were described using periodic acid-Schiff (PAS), peroxidase, nonspecific esterase, alkaline phosphatase, and toluidine blue. RESULTS: Reference intervals were as follows: thrombocytes 58,802-99,569/microL; total WBCs 27,460-41,523/microL; lymphocytes 5380-11,581/microL; monocytes 2949-7459/microL; neutrophils 12,529-22,748/microL, and basophils 736-2003/microL. Neutrophils were positive for peroxidase and PAS; monocytes were positive for nonspecific esterase; and basophils were positive with toluidine blue. CONCLUSION: The morphologic and staining features of neutrophils and monocytes of channel catfish are similar to those of mammals, and the presence of basophils in this species was verified. These reference intervals and morphologic findings provide a foundation for future investigations on the functions and alterations of blood cells in channel catfish.