Aegyptianella pullorumCarpano 1928—fine structure and taxonomy

Abstract

Intraerythrocytic granules in the blood of Sudanese fowls first seen by Balfour (1908) were namedAegyptianella pullorumby Carpano (1928).Electron microscopy of a Rhodesian strain ofA. pullorumindicated the similarity between these organisms and theRickettsia-PLT group of organisms, also their dissimilarity to Sporozoa which we have studied. The organism was coccoid or coccobacillary, measuring up to 0·6 μm in diameter, and in longitudinal sections 1·5–3 μm. Pleomorphic and dividing forms were observed. Each organism was surrounded by two unit membranes with short internal invaginations from the inner membrane only. A layer of ribosome-like particles varying in density and depth gave the impression of an outer cortex. Irregular extensions of this layer towards the centre of the organism followed the lines of fine DNA-like filaments forming a web lattice throughout the substance of the organism. There was no well-defined nucleus as seen in Protozoa. Single as well as groups of organisms were situated in vacuoles lined by a membrane similar to the erythrocytes' own outer membrane. No intranuclear organisms were seen.The similarity of these organisms to symbionts studied by Roshdy and Bird in both adult and immature stages ofA. persicusis illustrated. From this evidence, and its apparent likeness to the tick-borne fever agent, there is good reason for includingA. pullorumamong the Rickettsiaceae. The position suggested for it is between theRickettsiaand PLT group of organisms, closely allied toWolbachia, the agent of tick-borne fever (Cytoecetessp.) and the agent of bovine heart water disease (Cowdria ruminantium).We thank Mr R. Jacobson, F.I.M.L.T. for his willing assistance in conducting the sensitivity test, also Miss L. Lanigan and Mr D. Day for their technical and photographic assistance.