7 formalin-inactivated bacteria·mL -1 , for 20 minutes. Vaccinated fish groups presented higher hematocrit, number of erythrocytes and leukocytes than the non-vaccinated group. Serum agglutination titer of intraperitoneally vaccinated fish was higher on both evaluation periods for the three bacteria strains. Only on day 21 post-vaccination fish from the oral and immersion vaccination groups presented higher serum agglutination titer than the non-vaccinated fish for A. hidrophyla and E. durans. Serum antimicrobial activity in vaccinated fish was higher for P. aeroginosa and E. coli than in non-vaccinated fish on both evaluation periods. The different vaccine administration routes stimulated hematological and immunological responses in Nile tilapia 21 days post-vaccination, but intraperitoneal vaccination presented higher total number of leukocytes, lymphocytes and serum agglutination titer.

This

Infection by the acanthocephalan Neoechinorhynchus buttnerae is considered the most important obstacle in farmed tambaqui or cachama (Colossoma macropomum), the second most cultivated fish species in Brazil. This study describes the occurrence of N. buttnerae in farmed this fish based on parasitological and histopathological analysis in highly infected fish. A total of 102 fish were collected from fish farms located in Brazilian states in the northern region. All of the examined fish were heavily infected by N. buttnerae and showed no signs of anorexia, but heterogeneous growth and cachexia were frequently found. No cases of mortality were observed in fish farms. Macroscopically, the intestines showed hyperaemia, hardening, thickening of the intestinal wall, yellowish mucosal secretion and a bluetongue aspect. Histological sections showed different degrees of penetration of the acanthocephalan proboscis in the intestinal tissue, surpassing the mucosa, submucosa and muscular layer, provoking dilacerations due to their spines as well as an intense inflammatory reaction composed of macrophages, Langerhans cells and lymphocytes, and granuloma formation located mainly in the submucosa layer. Submucosal oedema, an increased number of goblet cells, metaplasia areas and a reduction of the intestinal villi were also observed. The results present an important register of N. buttnerae infection in C. macropomum and contribute to the comprehension of pathogeny caused by these worms. Statement of relevance: Characid fish farming has led to significantly increased fish production in Brazil. However, the most important obstacle is the acanthocephalan infection caused by Neoechinorhynchus buttnerae in the intestinal tract. The infection does not provoke death but cachexia and growth reduction are frequently observed as well as intense pathological conditions in histological sections.

Chilodonelids are small ciliated protozoans found worldwide and can be dangerous in culture conditions. This study presents morphometric data on the ciliate Chilodonella that is found in cultured Nile tilapia (Oreochromis niloticus), native bait fish tuvira (Gymnotus aff. inaequilabiatus) and native pacu (Piaractus mesopotamicus) and includes a histopathological assessment of the changes that occur in the pacu. For parasitic diagnosis, skin and gill samples were scraped onto slides, dried at room temperature, stained with Giemsa or impregnated with silver nitrate, and the measurements were obtained from photomicrographs. In the diseased pacu, the first gill arch was collected and fixed in a 10% buffered formalin solution for histopathological analysis. Parasite specimens from the different collection sites were identified morphologically as C. hexasticha Kiernik (1909). Diseased fish exhibited depigmentation, skin ulceration, scale loss, excessive mucus production and gill lesions. Histopathological analysis of pacu gills displayed epithelial proliferation with mononuclear inflammatory infiltrate, hemorrhages, and scattering necrosis. In Brazilian-farmed fish this is the first record of C. hexasticha, which has great pathogenic potential in cultured freshwater species. In addition, two new hosts are presented.

A total of 240 Nile tilapia were examined between April 2007 and March 2008, gathered from three different fish farms, 20 fish in each fish farm, in the four seasons of the year. Fish ponds were located in Joinville, Blumenau and Ituporanga, Santa Catarina state, Brazil and each pond had a different culture system. Prevalence, mean intensity, mean abundance and mean relative dominance were compared among fish ponds and seasons. During this period, the water quality was kept in normal values. Piscinoodinium pillulare (Dinoflagellida) was the most dominant parasite followed by Trichodina magna e T. compacta (Ciliophora), Cichlydogyrus sclerosus, C halli, C. thurstonae, Scutogyrus longicornis (Monogenoidea), copepodids Lernaeidae gen. sp. The highest prevalence, mean intensity and mean abundance of ectoparasites were found on the body surface in fish from Joinville followed by Blumenau and Ituporanga. In the gills, the highest mean intensity and mean abundance were found in fish from Blumenau and Ituporanga in the winter. Piscinoodinium pillulare showed prevalence 100% during autumn in Blumenau and Ituporanga. In winter P. pillulare occurred in all study facilities. Fish from Joinville showed 100% prevalence of Monogenoidea during all seasons, as well as the highest mean intensity and abundance. The results showed that the majority of examined fish had higher infestations by protozoan during autumn and winter and higher infestations by metazoan have occurred in spring and summer.

Resumo -O objetivo deste trabalho foi isolar bactérias ácido-lácticas do intestino de tilápias-do-nilo, e avaliar seu potencial probiótico. Foram isoladas cepas de bactérias ácido-lácticas, e foi avaliada a inibição aos patógenos in vitro. As cepas com os melhores resultados foram identificadas e utilizadas no experimento de colonização do trato intestinal de tilápias-do-nilo, via suplementação na dieta, em delineamento inteiramente ao acaso, com três tratamentos e quatro repetições. Foram avaliados: o total de bactérias, as bactérias ácido-lácticas, Vibrio ssp. e Pseudomonas ssp. A cepa com melhor resultado foi utilizada na infecção experimental, em delineamento inteiramente ao acaso, em esquema fatorial 2x3: dieta suplementada com a cepa e dietacontrole; e os peixes não submetidos à injeção, peixes submetidos à injeção de solução salina e à injeção de Enterococcus durans, com três repetições. Foram avaliados os parâmetros hematológicos. As duas cepas identificadas foram: Lactobacillus plantarum e Lactobacillus brevis, que colonizaram o trato intestinal de tilápias, contudo L. plantarum teve menor número total de bactérias e de Pseudomonas ssp. Foi observado maior número total de eritrócitos, trombócitos, leucócitos, linfócitos, neutrófilos e monócitos, em peixes alimentados com L. plantarum e submetidos à injeção de E. durans. O L. plantarum tem efeito probiótico e melhora o sistema imune das tilápias.Termos para indexação: Enterococcus durans, Lactobacillus plantarum, Oreochromis niloticus, hematologia, infecção experimental. Lactic-acid bacteria isolated from the intestinal tract of Nile tilapia utilized as probioticAbstract -The objective of this work was to isolate lactic-acid bacteria from the intestines of Nile tilapia, and to assess their potential as probiotic. Strains of lactic-acid bacteria were isolated, and inhibition against pathogens was evaluated in vitro. Strains with best results were identified and used in tilapia intestinal tract colonization experiment through supplementation in the diet, in a completely randomized design, with three treatments and four replicates. Total number bacteria, lactic-acid bacteria, Vibrio ssp. and Pseudomonas ssp. were evaluated. The strain with best result was used for experimental infection, in a completely randomized design, in factorial arrangement 2x3: diet supplemented with strain and control diet; and fish not submitted to injection, fish submitted to injection of saline solution, and fish submitted to injection of Enterococcus durans, with three replicates. Hematological parameters were evaluated. Two strains were identified as Lactobacillus plantarum and Lactobacillus brevis, which colonized fishes' intestinal tract. However, L. plantarum had the lowest number of total bacteria and of Pseudomonas ssp. Greater number of red blood cells, thrombocytes, leukocytes, lymphocytes, neutrophils and monocytes were observed in fish fed with L. plantarum and submitted to injection of E. durans. L. plantarum has probiotic effect on Nile tilapias and improve their imm...

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