Histological and hematological alterations of silver catfish Rhamdia quelen highly parasitized by Lernaea cyprinacea.

The main objective of this study was to evaluate the histological and hematological alterations of silver catfish Rhamdia quelen (Quoy & Gaimard, 1824) against intense parasitism by anchor worm Lernaea cyprinacea Linnaeus, 1758. Thirteen fish specimens were collected at the Fish Genetic Improvement Unit (EPAGRI/CEDAP), Brazil. After acclimatization, the fish were anesthetized for blood collection, and the samples were used for counting thrombocytes, total leukocytes, differential leukocytes and for quantification of total erythrocytes. Afterwards, the animals were euthanized, the parasites removed and quantified, and the portions of the affected tegument fixed in 10% buffered formalin. All the analyzed animals were parasitized by L. cyprinacea with mean intensity of 192 specimens per fish. The hematological profile of the animals was different from that reported for healthy fish. Immature leukocytes were the most abundant cells, followed by monocytes, lymphocytes, neutrophils, and periodic acid-Schiff-positive granular leukocytes. A small number of neutrophils were present in the bloodstream of parasitized fish, while histological examination evidenced the accumulation of this cell type near the place of infection by the parasite. Total leukocytes correlated significantly and positively (r = 0.6, p = 0.030) with the intensity of L. cyprinacea infection and the fish weight. Histological changes included hemorrhage, liquefactive necrosis and connective tissue disarrangement, necrosis, granulomatous inflammation, mononuclear and polynuclear inflammation, as well as hyperplasia and hypertrophy of the alarm and mucous cells. The L. cyprinacea infection intensity caused deleterious changes both in the hematological profile and the integument of R. quelen, confirming the pathogenic potential of this parasite to the affected fish species.

Haematological and parasitological assessment of silver catfish Rhamdia quelen farmed in Southern Brazil.

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.

Haematological and parasitological assessment of silver catfish Rhamdia quelen farmed in Southern Brazil / Monitoramento hematológico e parasitológico em jundiá Rhamdia quelen criado no Sul do Brasil

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.

O presente estudo avaliou, durante dois anos, os parâmetros hematológicos e a ocorrência de parasitos branquiais em jundiá Rhamdia quelen, cultivado no Estado de Santa Catarina, Sul do Brasil. Entre março de 2010 e janeiro de 2012, um total de 137 jundiás foi coletado de uma piscicultura para comparar os parâmetros hematológicos e parasitológicos durante as estações quente e fria. Simultaneamente, foram medidos os parâmetros de qualidade da água do viveiro, para relacionar as condições ambientais com a hematologia e o parasitismo. Na estação quente, houve aumento da temperatura, condutividade elétrica e amônia, e redução do oxigênio dissolvido, pH, transparência e alcalinidade. Duas espécies de Monogenea foram observadas nas brânquias, Aphanoblastella mastigatus (Dactylogyridae) e Scleroductus sp. (Gyrodactylidae). Na estação quente, houve aumento significativo (p<0,05) da intensidade média de infecção por Monogenea, bem como dos valores de leucócitos totais, trombócitos e linfócitos, e redução significativa dos monócitos. As diferenças observadas podem ter sido causadas pelas variações ambientais entre as estações.