Trypanosoma cruzi in the rectum of the bug Triatoma infestans: effects of blood ingestion by the starved vector.

To follow the developmental effects of feeding of the insect host after long starvation periods, the population density and composition of an established infection of Trypanosoma cruzi in the rectum of Triatoma infestans were determined 60 days after the last feeding (daf) and then at different intervals after feeding. The original population decreased and then increased up to the 10th daf. In starved bugs, about 30% were spheromastigotes (including intermediate forms), 20% epimastigotes, and 50% trypomastigotes, but one daf, these forms represented 2%, 70%, and 10%, respectively. In addition, one daf there were about 10% giant cells, i.e., a multiple division stage. In the following two days, this form represented on average 30-50% of the total population, but it then disappeared nearly completely. Thus, giant cells evidently develop by rapid growth of epimastigotes, if conditions become optimal after long starvation periods of the vector.