In this paper we report the first recorded occurrence of Trypanosoma vivax in the Pantanal, Brazil. The Pantanal is a seasonal floodplain of about 140,000 km 2 , located in the centre of South America, between 16° and 21° S and 55° and 58°W (Fig.). It is divided into ten subregions differing in terms of water courses, soil types and historical occupation (EMBRAPA/CENARGEN 1987 Documentos, 82, Brasília, DF, Brasil, 339 pp.). Extensive cattle ranches varying from 10,000 to 200,000 ha occupy most of this wetland. The Pantanal is one of the most important livestock + Corresponding author. Fax: 55-67-231.1011, E-mail: ramss@sede.embrapa.br Received 18 December 1995 Accepted 13 May 1996 regions of Brazil. Trypanosomosis is one of the world's most important diseases of livestock and man, and makes it practically impossible to raise livestock in many parts of the tropics which would otherwise be ideal. T. vivax infects a wide range of wild and domestic ungulates, is transmissible both cyclically by tsetse flies and mechanically by other blood suckling flies, and is recognized as an important cause of cattle losses in many areas (BA Allsopp & SD Newton 1985 Int J Parasitol 15: 265-270). In the acute form of infection the animal has a high temperature, lethargy, weakness, anemia and slight loss of condition and dies within five weeks. Abortion may occur, but foetal blood and amniotic fluid have not been found to be infected. Weight loss may be substantial in a relatively short time. It has been observed that pure zebu cattle develop high parasitemia and disease Location of trypanosomiasis outbreaks due to Trypanosoma vivax in the Poconé subregion of the Pantanal of Brazil. R1 to R9: Ranch 1 to Ranch 9.

Trypanosoma evansi caused severe anemia in horses and pronounced leukopenia in dogs, both naturally infected. The horses presented microcytic normochromic anemia and the dogs showed microcytic hypochromic anemia. The clinical signs observed were fever, anemia, edema of the legs and lower parts, weakness and inappetence. Light microscopic studies demonstrated that Trypanosoma evansi produced several alterations in erythrocytes of dogs and horses. These pathologic changes included vacuolation, acanthocytes, dacrocytes, codocytes, microspherocytes and bizarre shapes. Mature erythrocyte were observed adhered to trypanosomes. Erythrophagocytosis was also demonstred.

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