Genetic diversity among Leishmania (Viannia) parasites.

The mode of reproduction in, and population structure of Leishmania (Viannia) parasites were deduced from the nature and extent of genetic variation in the parasites. Forty-seven zymodemes belonging to the Viannia subgenus were analysed by enzyme electrophoresis and the profiles compared with those of two zymodemes belonging to the Leishmania subgenus. The results revealed extensive genetic variation in Viannia. The widespread occurrence of certain zymodemes, the level of heterozygosity and the great similarity observed among the samples are indicative of a clonal population structure. However, the large number of recurrent mutations needed to explain the variation observed and the presence of hybrid parasites indicate that occasional bouts of genetic exchange may occur.