Eperythrozoon-Like Bodies (Text-figure 1).

Blood smears were taken from 50 Australian black-tailed wallabies, Wallabia ualabatus (Lesson and Gamier), shot at Waimate in July, 1947. Those from seven animals proved to contain numerous bodies resembling Eperythrozoon Schilling. The bodies are in the form of rings occurring either free in the plasma (Text-fig. 1,

Text-figure 1

1—Erythrocyte of Wallabia ualabatus.

2—Free Eperythrozoon-like bodies.

3 and 4—Epierythrocytic Eperythrozoon-like bodies.

Fig. 2) or attached to the outer surface of erythrocytes (Text-fig. 1, Figs. 3 and 4). They stain reddish-purple with Giemsa, the free forms often having lighter staining maculations (Text-fig. 1, Fig. 2). Epierythrocytic forms stain more intensely on the side in contact with the red cell, as Tyzzer (1942) states to be the case for Eperythrozoon varians. The greatest diameter of these bodies ranges from 1.0μ to 3.3μ. Weinman (1944) claims that members of the genus Eperythrozoon do not exceed 2.0μ in diameter. The rings of Eperythrozoon are characteristically delicate structures. Dinger (quoted by Weinman) estimating the non-staining central zone of E. coccoides to occupy 80 per cent. of the total area of the organism. In the more massive ring bodies from Wallabia ualabatus, the central clear zone occupies only 6 per cent. to 15 per cent. of the total area.

All seven infected preparations are heavily contaminated with various bacteria. At first sight some of these could easily be confused with the solid discs and rods which accompany the rings of Eperythrozoon, but the manner of their occurrence in clumps, often associated with partly-laked areas of the smears, adjacent areas being clean and free from bacteria, points to external contamination. All the wallaby smears were prepared by an investigator working under trying field conditions, and I was subsequently informed that many of them had been made directly from shot wounds. Wenyon (1926) emphasizes that films made under such conditions almost always become contaminated with bacteria from the skin or wounded intestine. No Eperythrozoon-like bodies were found in any of the un-contaminated smears forwarded. These bodies are thus regarded as bacterial artefacts which entered the blood from some external source during the preparation of the smears concerned. Numbers of the bodies, having become attached to the outer surfaces of the erythrocytes, bear a superficial resemblance to epierythrocytic forms of Eperythrozoon. They may be distinguished from organisms of this genus by their appreciably greater size and the much smaller area of the central clear zone in relation to the total area of the body.