First Record of Trypanosoma Sp. (protozoa: Kinetoplastida) in Tuvira (gymnotus Aff. Inaequilabiatus) in the Pantanal Wetland, Mato Grosso Do Sul State, Brazil

Primeiro registro de Trypanosoma sp. Abstract 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. Resumo O objetivo do presente estudo foi reportar a infecção por Trypanosoma sp. em tuviras (Gymnotus aff. inaequilabiatus) oriundas do Pantanal Sul-mato-grossense, Brasil. Dez peixes provenientes do rio Paraguai, Pantanal Sul-mato-grossense, foram avaliados quanto à presença de hemoflagelados. Tripomastigotas de Trypanosoma sp. foram observados nas extensões sanguíneas de três peixes (30% de prevalência), e algumas formas encontravam-se em divisão. Por meio do exame a fresco e da centrifugação do sangue em capilar de hematócrito como métodos para diagnóstico, a taxa de prevalência foi de 80%. Esse é o primeiro relato de Trypanosoma sp. em tuviras no Brasil.


Introduction
Trypanosomes are kinetoplastid protozoa that cause blood infection in many species of fish worldwide, including both freshwater species (FIGUEROA et al., 1999;SMIT et al., 2004;GU et al., 2007;KONAS et al., 2010) and marine species (SAUNDERS, 1959;OVERATH et al., 1999;KARLSBAKK, 2004;BURRESON, 2007).Transmission of these hemoflagellates between fish has been attributed to different species of leeches.The leech Hemiclepsis marginata is responsible for transmission of T. carassii among European carp (OVERATH et al., 1999).In Canada, Actinobdella inequiannulata is the most abundant leech species and is the specific vector of T. catostomi for Catostomus commersoni (JONES; WOO 1992).The main vector of trypanosomiasis in fish belonging to the family Loricariidae in Brazil is the leech Batracobdella gemmata (D'AGOSTO;SERRA-FREIRE 1993).
The tuvira (Gymnotus aff.inaequilabiatus) (Teleostei: Gymnotidae) is a knifefish native species in the Pantanal basin that inhabits lentic environments, with turbid water and aquatic vegetation that is rich in organic matter coming from the flooding process.This species has economic importance because of its use as live bait, driven by the demand for sport fishing in the Pantanal, such as for the dourado (Salminus brasiliensis) and for two catfish species: pintado (Pseudoplatystoma corruscans) and cachara (Pseudoplatystoma reticulatum).However, constant exploitation has caused its numbers to diminish in its natural environment (MORAES; ESPINOSA, 2001).Production in captivity may be Pádua, S.B. et al. Rev. Bras. Parasitol. Vet. an economic alternative for riverbank peoples, and it may diminish the capture pressure on the natural environment.However, lack of information about health issues relating to tuvira has limited their rearing.Th e aim of the present study was to report the blood infection by Trypanosoma sp. in tuvira (G.aff .inaequilabiatus) from the Pantanal wetland, Mato Grosso do Sul State, Brazil.

Material and Methods
Tuvira specimens that had been caught by bait gatherers in the Paraguay river (18° 04' 15,00" S and 57° 28' 17,00" W), in the Pantanal, and had been put on the market in the Corumbá city, were acquired and transported to the Fish-farming Laboratory of Embrapa Western Region Agriculture, located in the Dourados, Mato Grosso do Sul State.Th e fi sh were kept in round fi berglass tanks with 1000 L of capacity, which were supplied with a continuous fl ow of water coming from an artesian well (10 L.min -1 ).
To diagnose the presence of hemofl agellates, ten fi sh specimens were subjected to venous puncture of the caudal vein, to collect blood.Blood smears on slides were produced in duplicate and stained panchromatically with the May Grünwald-Giemsa-Wright combination, and were then evaluated under an optical photomicroscope (Nikon® E200, Japan).Fresh blood between a slide and a coverslip was also examined, by means of phase contrast microscopy (Nikon ® E200, Japan).Th e same procedure was used for observations after centrifugation of blood samples in hematocrit capillary tubes, just above the white blood cell layer (WOO, 1969).

Results and Discussion
Trypomastigotes of Trypanosoma sp. were observed in the blood smears from three fi sh (30%) (Figure 1a, b), and some of them were found to be undergoing division (Figure 1d).From evaluating both the fresh samples and the results from centrifugation of blood samples in hematocrit capillary tubes, from the same fi sh specimens, the prevalence rate was found to be 80% (Figure 1c, d).Th is characterized the most effi cient method for diagnosis.
Th e prevalence rate of these blood parasites is generally high in fi sh from the natural environment (OVERATH et al., 1999;SMIT et al., 2004;KONAS et al., 2010).Th is is possibly related to the immunity mechanisms of the fi sh against infections.Overath et al. (1999) stated that the immune response of nonmammalian vertebrates is of limited effi cacy and/or these parasites evade or manipulate the immune response of their respective hosts.
Multiplication of these hemofl agellates in blood tissue has been described in some vertebrate hosts (PATERSON; WOO, 1984;BURRESON;KARLSBAKK, 2007).Th is division may be an adaptive mechanism, if the pathogenicity of these trypanosomes for their hosts is dependent on the intensity of the parasitemia (BURRESON; KARLSBAKK, 2007).

Conclusion
This is the first report of Trypanosoma sp. in tuvira in Brazil.Additional studies need to be conducted in order to identify this parasite systematically and molecularly, and to identify its biological cycle, pathogenicity and impact on tuvira populations in the natural environment and on populations reared by bait gatherers.