Trypanosoma cruzi: quantitative studies of development of two strains in small intestine and rectum of the vector Triatoma infestans.

This paper describes the development stages and numbers of flagellates of two strains of Trypanosoma cruzi living in the small intestine and rectum of the insect, Triatoma infestans, during the first 12 weeks postinfection (pi). Mainly epimastigotes and occasionally amastigotes and final trypomastigotes developed in the small intestine but after starvation periods of 3 or 4 weeks higher percentages of spheromastigotes including their transitional forms to/from epimastigotes were found. In the rectum, the percentage of final trypomastigotes increased in two steps; the second, but not the first, correlated with the development of intermediates originating from epimastigotes. For both strains the total number in the small intestine increased during the first 8 or 9 weeks, although there were reduced numbers when the bugs had starved for 3 or 4 weeks. In the rectum the numbers increased up to 10 weeks pi; only about 25% of these lived in the lumen, the others were located at the rectal wall. In small intestine and rectum the "Chile 5" strain of T. cruzi (zymodeme 1) nearly always reached higher population densities than the "Chile 7" strain (zymodeme 2).