Elleipsisoma thomsoni Franca, 1912: an Apicomplexan parasite in the red blood cells of the mole (Talpa europaea)

Abstract

SUMMARYThe rediscovery of Elleipsisoma thomsoni Franca 1912 from Talpa europaea is reported. This organism, whose identity as a parasite was initially doubted, is shown to be an intra-erythrocytic protozoan parasite. Light microscope observation confirmed the original description and 22/53 (42·5%) moles examined from a locality near Blackpool were positive. Organ impression smears demonstrated that E. thomsoni was concentrated in the heart and lungs, occasionally in the kidneys, liver and spleen. Electron microscope studies conclusively showed that the parasite was a member of the phylum Apicomplexa. A typical apical complex was present with rhoptries, micronemes, polar ring and microtubules but, in contrast to the genera Plasmodium, Babesia and Theileria, a conoid was also present. The parasitized red cells were larger than normal mature erythrocytes and the remaining cytoplasm of the erythrocyte was less dense than that of non-infected red cells. The problem of studying this enigmatic parasite and its life-cycle are described.