Different behavior of two Trypanosoma cruzi major clones: transmission and circulation in young Bolivian patients.

Specificity of two widespread Trypanosoma cruzi clonal genotypes or "clonets" (20 and 39) was first analyzed by hybridization with a large set of T. cruzi stocks characterized by multigenic study relying on both MLEE and RAPD. Then, these clonets were detected in the blood of Chagasic children from a Bolivian endemic area by a combination of polymerase chain reaction and clonet-specific DNA hybridization. The distribution of these clonets in patients was significantly different from that observed in the vectors of the same area (Triatoma infestans). In vectors, clonets 20 and 39 are found with comparable frequencies (0.69 and 0.67, respectively) in contrast with patients, in whom clonet 20 and mixed infections exhibit low frequencies. The Chagasic population can be divided into acute infections and latent infections above the accepted criterion of parasitemia (direct microscopic examination). The results suggest a limited selection in the transmission of the two clonets and a further drastic control of clonet 20 parasitemia by the immune system of children patients.