Trypanosoma cruzi in the rectum of the bug Triatoma infestans: effects of blood ingestion of the vector and artificial diuresis.

The population density and the percentage of different developmental stages of an established infection of Trypanosoma cruzi were determined at 40 days after the last feeding of the fourth instar in the rectum (lumen, anterior and posterior wall) of fed and unfed groups of fifth instars of Triatoma infestans. Additionally, the rectum and the Malpighian tubules were incubated in saline, inducing diuresis by addition of the diuretic hormone. The rectum contained an average of 200,000-400,000 T. cruzi. After feeding the percentages of spheromastigotes and drop-like intermediate stages were reduced from < 7% and 15%, respectively, to < 3%, but those of slender intermediate stages increased statistically significantly from < 7% to 10%. After 4 h of diuresis the in-vitro-incubated isolated rectum with the four Malpighian tubules showed the same trends, indicating that diuresis rather than factors of the hemolymph or digestive products induces the development of metacyclic trypomastigotes of T. cruzi originating from epimastigotes.