MODES OF ASSOCIATION OF TRYPANOSOMA-CRUZI WITH THE INTESTINAL-TRACT OF THE VECTOR TRIATOMA-INFESTANS

The interface between Trypanosoma cruzi and two regions of the intesti nal tract of reduviid bugs, the small intestine and the rectum, was in vestigated by electron microscopy. The mode of association of the tryp anosomes with the midgut surface differs fundamentally from that in th e rectum, the preferred site of colonisation by T. cruzi. The parasite s caused no detrimental changes in the extracellular membrane layers, microvilli or epithelial cells. Parasites resided mainly at the border of the gut contents, also regularly showing parasite-parasite interdi gitations. In regions in which the extracellular membrane layers were absent or only weakly developed, trypanosome bodies or flagella occasi onally could be found inserted shallowly between the tips of the micro villi. Since there were usually no ultrastructural modifications of th e cell body and/or flagellum associated with attachment, there is appa rently no strong attachment of the flagellates to the wall of the midg ut. In the rectal lumen the flagellates also interdigitated with each other and on the rectal wall T. cruzi was intimately attached to the r ectal cuticle lining. At the attachment site flagella were enlarged an d sometimes contained electron-dense, hemidesmosome-like material bene ath the plasma membrane. (C) 1998 Elsevier Science B.V. All rights res erved.