Acta Tropiea, 60(1995) 167-177 167 ACTROP 00507 Biological and isoenzymatic characterization of Trypanosoma cruzi strains isolated from sylvatic reservoirs and vectors from the state of Santa Catarina, Southern Brazil Mfirio SteindeP; Helena K. Tom#; Maria M. I. Ishid#; Silvane M. F. Murtab; Carlos J. de Carvalho PintoS; Edmundo C. Grisarda; Bruno R. Schlemper Jr.~; Rodrigo Ribeiro-Rodrigues b and Alvaro J. Romanha b'* "Departamento de Mierobiologia, Imunologia e Parasitologia, Universidade Federal de Santa Catarina, Caixa posta1476, CEP 88040-900, Florian6polis - Santa Catarina, Brazil bLaborat6rio de Parasitologia Celular e Moleeulat Centro de Pesquisas "Renb Rachou" FIOCR UZ, Av. Augusto de Lima 1715, 30190-002, Belo Horizonte, Minas Gerais, Brazil 'Received 29 March 1995; accepted 4 September 1995) Sixty eight Trypanosoma cruzi strains were isolated in the state of Santa Catarina, Southern Brazil, from sylvatic reservoirs or naturally infected vectors and characterized by their biological behaviour in mice, morphology of bloodstream forms and isoenzyme profiles. Twenty eight strains were isolated from the triatomine bug (Panstrongylus megistus), 2 from rodents (Echimys dasythrix and Akodon sp) and 38 from opossums (Didelphis marsupialis). The infectivity in mice of 48 T. cruzi strains showed that 2 (4.2%) were of high virulence, 19 (39.6%) of medium virulence, 15 (31.2%) of low virulence and 12 (25.0%) produced subpatent parasitemia in mice. A morphological study of bloodstream trypomastigotes from 8 T. cruzi strains showed a predominance of stout forms. The isoenzyme pattern of 59 T, cruzi strains showed that 54 (91.5%) belonged to zymodeme Z1, 3 (5.1%) to zymodeme Z2 and 2 (3.4%) to mixed zymodemes, Z1 and Z2. All 34 T. cruzi strains analyzed from opossums were Z1. Three out of 5 strains isolated from adults of P. megistus collected inside houses, belonged to zymodeme Z2 and two strains exhibited mixed zymodemes, Z1 and Z2, in 5 out of 6 enzymes studied. Although the State of Santa Catarina is a non endemic region for human Chagas'disease, the presence of zymodeme Z2 parasites in the sylvatic vector, P. megistus, captured in domiciliary environments suggests the possibility of human and/or domestic mammal infection by T. cruzi. Key words: Trypanosoma cruzi; Strains; Biological behaviour; Zymodeme; Chagas' disease Introduction Trypanosoma cruzL the ethiological agent of human Chagas' disease, is a digenetic protozoan that in nature circulates among a large number of triatomine bugs and mammalian species. Intraspecific variations in T. cruzi populations have been shown *Corresponding author SSDI 0001-706X(95)00124-7