Morphological changes of Trypanosoma vivax in mice

Morphological changes were observed in the blood forms of Trypanosoma vivax strain Y486 in mice on Days 12-13 of infection, following the peak parasitaemia. During this period elongate trypomastigotes, 25-40 μm long, were observed, most showing an anterior movement of the kinetoplast towards the nucleus and some having a blunt posterior end. In a few parasites a complete transformation to the epimastigote form, 40-42 μm long, was observed. Small sphaeromastigotes were also present, especially in the fine capillaries of various organs. Smears and electron microscopy suggested the presence of extravascular forms in the spleen.