QRAHAMELLA 905 



Eperythrozoon coccoides . 



This is a parasite of mice which was discovered independently by Dingei-(1928, 1929), 

 and Schilling (1928). A considerable proportion of normal mice appear to be infected, 

 but the organisms are rarely found unless the spleen is removed. Two to four days after 

 splenectomy the organisms appear in the blood in the form of rings or discs stuck on to 

 the external surface of the red blood corpuscles, and staining a bluish-purple colour with 

 Giemsa. Unlike Bartonella muris, they have a preference for polychromatic red cells. 

 They may persist in the blood for weeks or months, their numbers varying from time to 

 time. Beyond producing a slight degree of anaemia, they seem to be without any very 

 definite effect on the animal. Mice infected with Eperythrozoon coccoides are susceptible 

 to Bartonella muris, showing that the two organisms are distinct (see also McCluskie and 

 Niven 1934, Schwetz 1934, Marmorston 1935). In contrast to Bartonella, Eperythrozoon 

 is round in shape with numerous annular and disc-like elements ; rods are rare and are 

 seldom in chain formation. The organisms have not yet been cultivated. Infection 

 appears to be spread by lice. Numerous other animals, besides mice, are liable to infection 

 with Eperythrozoon (see Weinman 1944). 



Grahamella . 



This parasite was first described by Graham-Smith (1905) at Cambridge, who observed 

 it in the red blood cells of 10 per cent, of moles that were being examined for Piroplasma. 

 Since then it has been found in the blood of several other animals. The organisms appear 

 as longer or shorter rods of irregular contour lying within the red corpuscles. Though 

 resembling Bartonella, they are much coarser, and more like ordinary bacteria. With 

 Giemsa they take on a blue rather than a reddish tint. Only occasional red cells are 

 affected. According to Jettmar (1932) they can be cultivated on serum blood agar. 

 They appear to be non-pathogenic and to have no effect on the health of the host. In 

 the rat Vassihadis (1935) has been able to transmit infection from one animal to another 

 in series. In most animals splenectomy has little or no influence on infection, though 

 the rat is said to constitute an exception (Vassiliadis 1935). Ectoparasites, such as hce, 

 are probably responsible for the natural transmission of infection. Unlike Bartonella 

 muris, Grahamella seems to be resistant to arsenic (see also Kikuth 1934). 



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