Predominance of Trypanosoma cruzi lineage I in Mexico.

Randomly amplified polymorphic DNA (RAPD) has emerged as an effective genetic marker for analysis of Trypanosoma cruzi population variability. This method has been used to study the genetic variability of Mexican T. cruzi stocks and to relate these results to previous classifications. High clonal diversity was observed among the Mexican populations: 24 RAPD types were scored among 56 stocks analyzed. Only two stocks (3.6%) belonged to the T. cruzi II lineage, while all others belonged to T. cruzi I. The robustness of these clusters was statistically highly significant. Mexican T. cruzi I stocks formed a homogeneous group with reduced genetic distances among its members. Parasites from this group were isolated from both domestic and sylvatic cycles over a broad geographic area in Mexico. The two Mexican stocks classified as T. cruzi II (isolated from sylvatic cycles) were of the same RAPD type, although they were not closely related to the three reference T. cruzi II stocks circulating in domestic cycles in Argentina, Brazil, Bolivia, and Chile. These stocks were also unrelated to the formerly named Zymodeme III.