Trypanosoma cruzi infection in Didelphis marsupialis in Santa Catarina and Arvoredo Islands, southern Brazil.

Between 1984 and 1993 the prevalence of the Trypanosoma cruzi infection in opossums (Didelphis marsupialis) was studied in Santa Catarina and Arvoredo Islands, State of Santa Catarina, Brazil. The association of the triatomine bug Panstrongylus megistus with opossums nests and the infection rate of these triatomines by T. cruzi was also studied. Thirteen different locations were studied in Santa Catarina Island (SCI), in which 137 D. marsupialis were collected. Sixty two opossums were collected at the Arvoredo Island (AI), located 12 miles north from SCI. All captured animals were submitted to parasitological examinations that revealed the presence of T. cruzi in 21.9% of the opossums captured in SCI and 45.2% among opossums captured in the AI. The presence of P. megistus was detected in most of the D. marsupialis nests collected in the SCI, however, in the non-inhabited AI only eight triatomines were collected during the whole study. The presence of T. cruzi-infected D. marsupialis associated with P. megistus in human dwellings in the SCI, and the high infection rate of D. marsupilais by T. cruzi in the absence of a high vector density are discussed.

Elimination of bancroftian filariasis (Wuchereria bancrofti) in Santa Catarina state, Brazil.

During the 1950s, three foci of Wuchereria bancrofti transmission were identified in the State of Santa Catarina, Brazil. In Florianópolis, São José da Ponta Grossa and Barra da Laguna community treatment of bancroftian filariasis with diethylcarbamazine (DEC) was performed using two distinct approaches, without vector control or improvements in sanitation. In two of the three communities only microfilaraemic individuals were treated, while in Barra da Laguna the entire population received DEC treatment regardless of their infection status. In both cases, transmission of the parasite was blocked and no new cases were detected in all localities for up to 10 years. Recently, a new survey in São José da Ponta Grossa and Barra communities revealed no microfilaria-positive individuals, including residents that were positive in the 1950s. These data confirm that transmission of W. bancrofti was interrupted in Santa Catarina, and mass treatment appears to be more effective than treatment of microfilaraemic individuals only.

Biological and isoenzymatic characterization of Trypanosoma cruzi strains isolated from sylvatic reservoirs and vectors from the state of Santa Catarina, Southern Brazil.

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.

[Very large trypomastigotes as a morphological pattern of strains of Trypanosoma cruzi in the southern region of Brazil]. / Tripomastigota muito largo como padrão morfológico de cepas do Trypanosoma cruzi do extremo sul do Brasil?

The morphological patterns of blood trypomastigotes from five sylvatic Trypanosoma cruzi strains from Santa Catarina, South Brazil, were studied during the course of infection in experimentally infected mice. A predominance of stout trypomastigotes (greater than 70%) was observed during all over the acute phase in four strains of medium virulence. With the remaining strain, of high virulence, the slender forms predominating at the early infection stage were soon also replaced by stout forms. Since almost all T. cruzi strains displaying predominance of this peculiar morphological pattern have been isolated in South Brazil (Rio Grande do Sul, Santa Catarina) and since there are evidences pointing out to the existence of biological differences among these distinct blood parasites, the authors suggest further investigations of possible correlations between the morphological markers and clinical-epidemiological aspects of Chagas' disease.

Growth-inhibition drug test with Trypanosoma cruzi culture forms.

A 48-hr drug screening test is described which evaluates inhibition of exponential growth of T. cruzi culture forms by electronic cell count. About 80% of drugs active in vivo produced a greater than 50% growth inhibition, whereas among compounds inactive in vivo, only 19.6% induced such inhibition. Advantages of this test are low cost, rapid results, small amounts of drugs needed, and feasibility without animal facilities. Comparative studies showed that culture forms are not suitable for screening additives to prevent transmission of T. cruzi by banked blood.