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

Abstract

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.

Developmental and reproductive patterns of Triatoma brasiliensis infected with Trypanosoma cruzi under laboratory conditions

“…T. cruzi requires synergistic stressors, such as starvation or other environmental factors, to cause actual harm to the triatomines (Schaub 1992). Scanning electron microscopy demonstrated that the T. cruzi parasites create a carpet of 3-4 layers on the rectal cuticle of the insect, which could impair the uptake of nutrients (Schaub & Böker 1987). In T. cruzi-infected Panstrongylus megistus, the reproductive parameters were significantly affected (Lima et al 1992).…”

The development of Blastocrithidia triatomae (Trypanosomatidae) in the reduviid bug Triatoma infestans (Insecta): influence of starvation

“…In a subsequent investigation, starvation affected this distribution pattern and, at 30 and 60 days after feeding, about 20% and 40%, respectively, of the living flagellates were attached to the rectal wall and, at 90 and 120 days after feeding, the value was already 70% (Kollien and Schaub 1998). Differences in population density between the different regions of the rectal wall were evident, using scanning electron microscopy (Bo¨ker and Schaub 1984;Schaub and Bo¨ker 1986b). In established infections, the numbers of T. cruzi found on the small rectal pads and the larger posterior rectal wall were similar but, during starvation, more parasites remained attached to the rectal pads.…”

“…The homoxenous flagellate Blastocrithidia triatomae colonizes the same regions of the intestinal tract of triatomines as Trypanosoma cruzi, the causative agent of Chagas disease (Schaub 1983;Schaub and Bo¨ker 1986b). Both parasites also possess identical developmental stages in the bug, with the exceptions that only B. triatomae develops drought-resistant cysts and only T. cruzi develops trypomastigotes (Kollien and Schaub 1999).…”

Trypanosoma cruzi Infection in Mepraia gajardoi and Mepraia spinolai: The Effect of Feeding Nymphs from the Field

“…The parasite density is only strongly influenced by very long starvation up to 20 weeks. [7][8][9] In the laboratory, the feeding status also modulated the olfactory host search behavior of triatomines.10 In Chile, the wild vector of Chagas disease is Mepraia spp. (Hemiptera, Triatominae), which is composed of three different species: M. gajardoi, M. spinolai, and M. parapatrica.…”

“…In established experimental infections, T. infestans remained to be infected after prolonged starvation. 7 The wild insect vectors in Chile can be highly infected with T. cruzi, but those looking for humans to feed are starved with low parasite burden and therefore, have a lower chance of transmitting T. cruzi. However, the proximity of other reservoirs (vertebrates) to human housing may change this probability.…”