COMPARED VECTORIAL TRANSMISSIBILITY OF PURE AND MIXED CLONAL GENOTYPES OF TRYPANOSOMA-CRUZI IN TRIATOMA-INFESTANS

A total of 15 mixtures involving 9 different stocks attributed to the 19/20, 32 and 39 major clonal genotypes of Trypanosoma cruzi were used to infect third-instar nymphs of Triatoma infestans via an artificial feeding device. Three biological parameters were considered: (1) the percentage of infected insects (%II), (2) the number of flagellates pe r insect (NFI), and (3) the percentage of trypomastigotes per insect ( %DIF). Genetic characterization by both multilocus enzyme electrophore sis (MLEE) and random amplification of polymorphic DNA (RAPD) indicate d that in almost all cases (87%), mixtures remained present after comp letion of the whole cycle in the insect vector. Two lines of compariso n were performed: (1) pure clonal genotypes versus corresponding mixed clonal genotypes and (2) the actual behavior of mixed clonal genotype s versus the expected behavior of the theoretical mixture (i.e. the ar ithmetic mean of the results observed for each of the two clonal genot ypes taken separately). Statistical analyses of the variables were mad e difficult because of the presence of large standard deviations. Neve rtheless, in several cases, mixtures differed significantly from pure clonal genotypes, and in one case the actual mixture differed signific antly from the theoretical mixture. In some cases, interaction (either potentialization or reciprocal inhibition) could be suspected.