TRYPANOSOMA-CRUZI - STUDY OF THE DISTRIBUTION OF 2 WIDESPREAD CLONAL GENOTYPES IN BOLIVIAN TRIATOMA-INFESTANS VECTORS SHOWS A HIGH-FREQUENCY OF MIXED INFECTIONS

The detection of two widespread Trypanosoma cruzi clonal genotypes (20 and 39) in feces of Bolivian specimens of the vector Triatoma infesta ns was performed by a combination of polymerase chain reaction and clo ne-specific DNA hybridization. The hybridization pattern of 186 PCR po sitive samples of T. infestans feces collected in two Bolivian departm ents identified clone 20 in 74.2% and clone 39 in 63.4% of the triatom ine bugs. For the first time, a high percentage (mean: 43.2+/-26%) of mixed infections (presence of both clones in a given fecal sample) in various localities was recorded. Results were in agreement with the tw o assumptions of independent transmission of clones 20 and 39 and of t he absence of selection in the natural cycles under survey. Statistica l analysis of the geographical distribution of clones 20 and 39 favore d the hypotheses that the frequencies of T. cruzi natural clones are d ifferent among localities and that these differences are not proportio nal to the distances that separate the localities. The epidemiological significance of these results is discussed. (C) 1996 Academic Press. Inc.