Natural populations of Trypanosoma cruzi, the agent of Chagas disease, have a complex multiclonal structure
Fecha
1986Autor
Tibayrenc, Michel
Ward, Philip
Moya, Andrés
Ayala, Francisco J
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ABSTRACT.
We have studied 15 gene loci coding for
enzymes in l2l Trypanosoma cruzi stocks from a wide geographic rangFfrom the United States and Mexico to Chile and
southern Brazil . T. cruei is diploid but reproduction is basically
clonal, with yery little if any sexuality remaining at present. We
have identified 43 different clones by their genetic composition;
the same genetic clone is often found in very distant places and
in diverse hosts. There is much genetic heterogeneity among the
different clones, and they cannot be readily classified into a few
discrete groups that might represent naturd taxa. These
findings imply that the biological and medical characteristics
need to be ascertained separately for each natural clone. The
evidence indicates that clonal evolution is very ancient in f.
cruzi. We propose two alternative hypotheses concerning the
relationship between the biochemical diversity and the heterogeneity in other biological and medical characteristics of f.
cruzi. One hypothesis is that the degree of diversity between
strains simply reflects the time elapsed since their last common
ancestor. The second hypothesis is that biological and medical
heterogeneity is recent and reflects adaptation to different
transmission cycles. A decision between the two hypotheses can
be reached with appropriate studies, with important medical
consequences.