Márcia Mayumi Ishikawa

Paratrichodina africana (Ciliophora): A pathogenic gill parasite in farmed Nile tilapia

Trichodinids are ciliated protozoa that are widely known as one of the main groups of fish parasites. The genus Trichodina presents the greatest species diversity. However, records of Paratrichodina species are scarce, and little is known about their pathogenicity in hosts. The present study provides new records of Paratrichodina africana Kazubski and El-Tantawy (1986) in Nile tilapia from South America and descriptions of pathological changes and seasonality. A total of 304 farmed fish were examined. From gill scraping, parasites were identified using Kleins nitrate impregnation method. Gill samples were fixed for histopathological analysis. Small trichodinid found in this study have a prominent blade apophysis and narrow central part and blade shape that corresponds to the characteristics of P. africana Kazubski and El-Tantawy (1986). Gill lesions were proportional to parasite intensity, in which the gill tissue was compromised in heavy infestation. Proliferative disturbances were found, including epithelial hyperplasia, desquamation, and mononuclear and eosinophilic infiltrate that culminated in necrosis. We did not observe a seasonality effect on the occurrence of P. africana. This ciliated protozoan causes compromised respiratory capacity that leads to severe gill lesions and currently is an important pathogen that afflicts intensive tilapia cultures in Brazil.

First record of Chilodonella hexasticha (Ciliophora: Chilodonellidae) in Brazilian cultured fish: A morphological and pathological assessment

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.

Investigação epidemiológica da brucelose bovina em um estrato do Estado de Mato Grosso do Sul

The study aimed to estimate the prevalence of bovine brucellosis in 22 counties which make up the region Extract 1 of the State of Mato Grosso do Sul, Brazil, in order to identify risk factors associated with the infection. The sample region encompasses an area of 70,214.1 km2 and represents 19.7% of the State. The region studied has about 5.7 million head of cattle, corresponding to 23% of the total of 24.9 million cattle in the State of Mato Grosso do Sul. On 210 farms, between December 2003 and March 2004, 2,376 blood samples were collected from cows, aged 24 months or older, for serial diagnostic tests. Screening through the buffered acidified antigen test was confirmed by the 2-mercaptoetanol test. On the occasion of sample collection a questionnaire with information related to identification, kind of cattle and management practices was filled out. In individual animals the real prevalence was estimated at 5.6%, and in the cattle herds at 37.3%. The variables, which presented association through odds ratio (OR), univariate analysis and 95% confidence interval (CI) with serum positivity for brucellosis, were: the exploration of beef cattle (OR = 2.82, 95% CI = 1.49-5.34), Zebu breed (OR = 2.62, 95% CI = 1.40-4.88) and abortion (OR = 1.83, 95% CI = 1.01-3.33). The results shown here demonstrate, despite the prevalence of brucellosis in the extract of Mato Grosso do Sul studied, that the control of the disease may depend on adoption of a program focusing upon the exploration of beef cattle, the Zebu breed and the occurrence of abortion.

Heparina e Na2EDTA como anticoagulantes para surubim híbrido (Pseudoplatystoma reticulatum x P. corruscans): eficácia e alterações hematológicas

The effect of heparin 100IU and Na2EDTA in concentration of 3%, 5% and 10% on the blood coagulation and hematological parameters of hybrid surubim catfish were evaluated. We used ten fish weighing 386,7±24,3g and average length of 38,7±6,4cm for collection of blood samples and determination of the percentage of hematocrit, plasma total protein content and osmotic fragility erythrocytes test (OFE). Data were submitted to analysis of variance and averages compared by Tukey test at 5% probability. Coagulation was efficiently inhibited when used the Na2EDTA, while the samples with heparin coagulate ten hours after collection. There was an increase in osmotic fragility of erythrocytes (P<0.01), especially when using Na2EDTA 10% and 5%, with no difference between control and heparin. In hematocrit and total plasma protein content were not observed statistical differences. The Na2EDTA 3% is safe and effective anticoagulant for hybrid surubim catfish, preventing clotting for more than 10 hours causing slight effect on the osmotic fragility of erythrocytes.

Fauna parasitária dos híbridos siluriformes cachapinta e jundiara nos primeiros estágios de desenvolvimento

The objective of this work was to evaluate the parasitic fauna of the hybrid fish cachapinta (Pseudoplatystoma corruscans male x P. reticulatum female) and jundiara (Leiarius marmoratus male x P. reticulatum female) at the hatchery stages. A total of 315 animals, 126 hybrids of jundiara and 189 hybrids of cachapinta were examined according to their development stage: larvae, post‑larvae, and fingerlings. Larvae and post‑larvae were pressed between a slide and a cover slip and were observed under optical microscopy. Fingerlings were externally observed in a stereomicroscope and dissected for internal evaluation of organs. Water quality parameters were measured in all cultivation phases. The parasitological exam showed the presence of the protozoa Epistylis sp. and Trichodina sp., on integument and gills, and Ichthyophthirius multifiliis on integument, of the helminth Monogenea on gills, and of digenean metacercariae on gills, spleen, kidneys, liver, and intestines in both hybrid fish evaluated. The parasites Epistylis sp., Trichodina sp., and digenean metacercariae occur most frequently in the two hybrids at the stages of post‑larvae and fingerlings. There is a higher prevalence and diversity of parasites in the fingerling phase of the studied hybrids.

Trichodina colisae (Ciliophora: Trichodinidae): new parasite records for two freshwater fish species farmed in Brazil

Family Trichodinidae comprises ciliate protozoa distributed worldwide; they are considered some of the main parasitological agents infecting cultivated fish. However, the trichodinidae parasitizing important fish species cultured in Brazil are unknown, and more taxonomic studies on this group of parasites are required. This research morphologically characterizes Trichodina colisae Asmat & Sultana, (2005) of pacu (Piaractus mesopotamicus) and patinga hybrid (P. mesopotamicus × P. brachypomus) cultivated in the central and southeast regions of the country. Fresh assemblies were made from mucus scraped from the skin, fins and gills, fixed with methanol and, subsequently, impregnated with silver nitrate and stained with Giemsa for assessment under light microscopy. This research reports not only the second occurrence of T. colisae in the world, but also its first occurrence in South America.

First record of Trypanosoma sp. (Protozoa: Kinetoplastida) in tuvira (Gymnotus aff. inaequilabiatus) in the Pantanal wetland, Mato Grosso do Sul State, Brazil

The blood infection by Trypanosoma sp. in tuvira (Gymnotus aff. inaequilabiatus) from the Pantanal wetland was reported in this study. Ten fish from the Paraguay River in the Pantanal were evaluated for the presence of hemoflagellates. Trypomastigotes of Trypanosoma sp. were observed in blood smears from three fish (30% prevalence) and some forms were seen to be undergoing division. Using the diagnostic methods of fresh examination and blood centrifugation in hematocrit capillary tubes, the prevalence rate was 80%. This is the first report of Trypanosoma sp. in tuvira in Brazil.

Parasitological assessment in the hybrid surubim (Pseudoplatystoma reticulatum x P. corruscans), with uncommon occurrence of Monogenea parasites

This study evaluated the parasite fauna of farmed hybrid surubim (Pseudoplatystoma reticulatum x P. corruscans) and the host-parasite-environment relationship in two fish farms located in Mato Grosso do Sul, Central Brazil, South America. A total of 120 hybrids from two different farms, 60 in each season (30 in the hot and 30 in cold season) were examined during a year. Water quality was weekly measured to evaluate the interaction among environmental conditions and parasitism. Histopathology was used to observe the effects of the parasites and environment on the fish gills. The ciliate protozoan Ichthyophthirius multifiliis and the monogeneans (Ameloblastella sp., Amphocleithrium paraguayensis, Vancleaveus ciccinus, V. fungulus and V. janacauensis) were the most prevalent parasites detected in both seasons in both farms, with prevalence above 80%. It was stated that parasites did not cause important damage in the health status of the hybrid surubim. These results might be related to general good management practices and environmental quality implemented by the fish farmers. The presence of uncommon monogenean parasites to this hybrid compared to their parents causing an environmental and ecological concern is here discussed.

Parasitofauna de cachara cultivado em tanque-rede no rio Paraguai

The objective of this work was to describe the parasitic fauna of cachara (Pseudoplatystoma reticulatum) cultured in a net-cage in the Paraguai River, Brazil. Ten fish with mean weight of 598.0±81.3 g and total length of 38.6±1.6 cm were examined. All necropsied fish were parasitized by at least two species. Among them, Ichthyophthirius multifiliis (Ciliophora), Myxobolus sp. and Henneguya sp. (Myxozoa), Monogenoidea, Choanoscolex abscissus and Nominoscolex sudobim (Cestoda), Dolops carvalhoi (Crustacea), and Digenea were diagnosed. The protozoan Ichthyophthirius multifiliis was the most prevalent parasite.

Produção de silagem ácida a partir de vísceras de surubim ("Pseudoplatystoma" sp.) e avaliação da digestibilidade para tilápia-do-nilo

Different proportions of formic acid and citric acid to produce surubim catfish viscera silage and to determine the chemical-bromatological composition and apparent digestibility of dry matter, crude protein, ether extract, crude energy and availability of calcium and phosphorus for Nile tilapia were evaluated in this study. It was used: 0.75; 0.75:1; 1:1.25 and 1.25:1 of formic acid and citric acid respectively, plus antioxidant (BHT) 0.02% for silage production. After 30 days different proportions of acids provided stable content (pH below 4) that not differed among treatments. Silage prepared with 1.0:0.75 formic acid:citric acid was selected and showed the following results expressed on dry matter: 25.7% of crude protein, 7330kcal/kg of gross energy, 42.4% of ether extract, 0.06% of calcium Ca and 0.27% of phosphorus. The apparent digestibility coefficients for dry matter, crude protein, ether extract, gross energy, calcium and phosphorus in ensiled compound showed the following percentages: 83.52; 93.30; 80.18; 87.20; 83.11 and 74.28%. Production of surubim catfish viscera silage is feasible with citric acid and formic acid and this ingredient may be considered an alternative protein source with high biological value for Nile tilapia