Cannibalism and coprophagy are modes of transmission of Blastocrithidia triatomae (Trypanosomatidae) between triatomines.

Transovarial transmission was not detectable among Blastocrithidia triatomae-infected Triatoma infestans. Rather, B. triatomae was transmitted directly between triatomines by cannibalism and coprophagy. Cannibalism conditions that excluded coprophagy always resulted in an infection of Dipetalogaster maxima. The efficiency of transmission was not influenced by the blood source--mice or chickens--fed to the infected donor bugs although chicken blood lyses the epimastigotes of the stomach population. Triatoma infestans was infected by coprophagy only if fed, not if unfed. Blastocrithidia triatomae in dry feces was taken up only if the feces were redissolved in fresh feces. Infections also appeared in groups of bugs fed on chickens previously used for feeding infected bugs.

Colonization of the rectum of Triatoma infestans by Trypanosoma cruzi studied by scanning electron microscopy: influence of blood uptake by the bug.

The colonization of the different regions of the rectum of Triatoma infestans by Trypanosoma cruzi was studied in unfed larvae, during and after feeding of the bug by scanning electron microscopy. The rectal pads always possessed the highest population densities, but in some bugs the main rectal sac and the region around the anus were also covered by a "carpet" of flagellates. Such high densities were never observed at the midgut/rectal junction. A slight decrease in this region might be caused by blood ingestion and the resulting excretion of urine. However, the flagellates in this region cannot be responsible for a phenomenon described by other authors, namely that the percentage of metacyclics is low in the first drop of faeces and increases in the following drops of deposited urine. Our observations indicate that metacyclics lying on the "carpet" of flagellates in bugs before and right after the start of feeding might later become loosened. In all dissections, numerous metacyclics were attached to the rectal wall. Further studies are necessary to clarify the exact origin of metacyclics in the urine.

Colonization of the rectum of Triatoma infestans by Trypanosoma cruzi: influence of starvation studied by scanning electron microscopy.

The colonization of the different regions of the rectum of Triatoma infestans by a Trypanosoma cruzi strain (zymodeme I) originating from the same locality as the bugs was studied by scanning electron microscopy after different periods of starvation of the bugs. Throughout the first 16 weeks no changes in colonization pattern could be observed. Parasite density was always minimal at the midgut/rectal junction and highest on the rectal pads; it was at a similar level in the other three regions of the rectum. Twenty weeks after feeding, a proportion of the bugs had died and in the surviving larvae a decreasing colonization of the cuticle occurred. Nonetheless, despite other regions being flagellate-free, a residual T. cruzi population always remained attached to the rectal pads. No changes in the proportion of trypomastigotes to epimastigotes were observed as starvation progressed.

Scanning electron microscopic studies of Trypanosoma cruzi in the rectum of its vector Triatoma infestans.

The cuticular surface of the rectum of Triatoma infestans and its colonization by a Trypanosoma cruzi strain originating from the same locality as the bugs were studied by scanning electron microscopy at different weeks post infectionem. On the basis of the cuticular folding, the rectum can be subdivided into five regions. The rectal gland has the finest structure and the region anterior to the anus the deepest folds. Try. cruzi always prefers to colonize the rectal gland, while the other regions are colonized in varying densities. Most of the flagellates are epimastigotes (long and short), except in the region at the entrance of the midgut, where trypomastigotes predominate.