Pathogenesis of Trypanosoma brucei infection in deer mice (Peromyscus maniculatus): light and electron microscopic studies on erythrocyte pathologic changes and phagocytosis.

Light microscopic and scanning and transmission electron microscopic studies demonstrated that Trypanosoma brucei EATRO 110 produced several alterations in RBC structure including microspherocytes, schistocytosis, vacuolation, doughnut-cell formation, and keratocytosis. Mature RBC and reticulocytes were constantly observed to adhere firmly to trypanosomes in heart blood and in blood vessels of the testes, heart, liver, and kidney, as well as in the sinuses and pulp cords of the spleen. Adhesion of RBC to trypanosomes was also observed by light microscopy in thin blood films. Except for a few platelets that adhered to trypanosomes, other blood cells were not involved. Minute pores were sometimes observed on the RBC membrane at the point of adhesion to the trypanosome, but effects were not seen on the parasite. Erythrophagocytosis was marked in the spleen and to a lesser extent in the liver; mature RBC, as well as reticulocytes, were engulfed. Erythrophagocytosis was presumed to arise from the mechanical injury to RBC, the damage caused by the adhesion phenomenon and the hyperactivity of the enormously enlarged spleen.