Characterization of Trypanosoma cruzi populations by zymodemes: correlation with clinical picture.

Trypanosoma cruzi isolated from 55 chronic chagasic patients were grouped into isozymic strains on the basis of electrophoretic patterns for a set of six enzymes. The total sample showed a distribution of asymptomatic (63.6%) and clinically ill (36.4%) patients similar to that generally reported for Chagas' disease. Six of the 12 zymodemes known to exist in Argentina have been isolated from humans. Only two (Z1 and Z12) are frequent and widely distributed in the endemic area. These two zymodemes differ significantly in their pathogenicity. The proportion of asymptomatic patients was higher with the Z1 zymodeme (81.1%) than with the Z12 zymodeme (27.3%). The incidence of heart alterations was lower in Z1 than in Z12 zymodeme patients (18.9% versus 72.7%). Clinically evident acute disease was seen in 36.3% of cases with zymodeme Z12 and in 8.1% of cases with zymodeme Z1. The differences between the two prevalent zymodemes in Argentina are statistically significant. These observations indicate that the Z1 T. cruzi is a more benign strain than Z12. Patients infected with Z1 would be more likely to be asymptomatic for a longer time than those infected with Z12. The risk of cardiac lesion would be greater for patients harboring Z12 T. cruzi than for those with Z1. The results suggest that strain identification could be a useful prognostic tool.