Light and electron microscopic features of Eperythrozoon-like parasites ina North American opossum (Didelphis virginiana)

Epierythrocytic parasites associated with a severe anemic episode have not been previously reported in the opossum. A Wright-Giemsa-stained peripheral blood smear from an anemic North American opossum (Didelphis virginiana) r evealed numerous organisms attached to red blood cells either singularly or in chains. Ring forms of the organism were common and could be found free in the plasma. Electron microscopy revealed that these organisms were attac hed to the intact plasma membrane in depressions on the surface of red bloo d cells. Delicate fibrils between the organism and adjacent membrane were o bserved. The organisms were round to oval with a diameter of 300-750 nm and were enclosed by a single limiting membrane. The light and electron micros copic features of these epierythrocytic organisms are similar to those repo rted for Eperythrozoon and Haemobartonella species.