Trypanosoma vivax Adhesion to Red Blood Cells in Experimentally Infected Sheep

Trypanosomosis, a globally occurring parasitic disease, poses as a major obstacle to livestock production in tropical and subtropical regions resulting in tangible economic losses. In Latin America including Venezuela, trypanosomosis of ruminants is mainly caused by Trypanosoma vivax . Biologically active substances produced from trypanosomes, as well as host-trypanosome cellular interactions, contribute to the pathogenesis of anemia in an infection. The aim of this study was to examine with a scanning electron microscope the cellular interactions and alterations in ovine red blood cells (RBC) experimentally infected with T. vivax . Ovine infection resulted in changes of RBC shape as well as the formation of surface holes or vesicles. A frequent observation was the adhesion to the ovine RBC by the trypanosome's free flagellum, cell body, or attached flagellum in a process mediated by the filopodia emission from the trypanosome surface. The observed RBC alterations are caused by mechanical and biochemical damage from host-parasite interactions occurring in the bloodstream. The altered erythrocytes are prone to mononuclear phagocytic removal contributing to the hematocrit decrease during infection.