792 THE INTRA-CORPUSCULAR H^EMATOZOA 



confers immunity. The blood of immunized animals contains the parasite and is 

 capable of setting up a fatal disease in a non-immune animal. 



Appearance in the blood. The parasites, numerous in the acute form, are 

 somewhat rare in the chronic form of the disease. This species, like P. 

 bigeminum, is found in the blood in two forms : 



1. The round, amoeboid forms sometimes small and free, sometimes 

 discoid or annular contained in the red cells divide by budding (Kinositha) : 

 the annular forms consist of a ring of protoplasm enclosing a central vacuole ; 

 the protoplasm contains a chromatin mass divided into nucleus and blepharo- 

 plast (Liihe). 



2. The pear-shaped forms appearing particularly during the second period 

 of the infection correspond, according to Kinositha, to sexually differentiated 

 sporonts ; but in the blood they may multiply by binary longitudinal divi- 

 sion. Some parasites have one or -two flagella (Breinl, Kinositha). The 

 pyriform bodies are free or intra-corpuscular : some of the red cells contain 

 as many as eight parasites. 



[Cf. Nuttall and Graham-Smith's description (p. 788).] 



Development in the tick. Christophers, following the development of the 

 parasite in Rhipicephalus sanguineus, describes a sporogonic development 

 as taking place in the alimentary canal of the tick resulting in the formation 

 of vermicular elements which pass into the ovaries of the adult tick and into 

 the embryonic tissues of the nymph, there forming a rounded mass, or zygote, 

 which in turn gives origin to sporoblasts and these to sporozo'ites. 



Cultures. In vitro, Kleine has observed modifications of the parasite 

 without true multiplication, in diluted defibrinated blood. The blood is 

 collected from infected dogs some hours before death, defibrinated and mixed 

 with an equal volume of normal saline solution and incubated at 25 C. to 

 27 C. 



Under these conditions, club forms with radiating processes are seen after 

 about 12 hours similar to those described by Koch in the case of P. bigeminum : 

 these bodies exhibit very distinct amoeboid movement. They assume a 

 rounded form towards the second day, the radiating processes become 

 obliterated and the parasites then themselves disappear. 



Methods of detection. The technique is similar to that for Piroplasma 

 bigeminum. Nocard advises fixing the blood films in absolute alcohol and 

 staining with carbol-thionin. 



To facilitate the diagnosis in cases in which the parasites are few in number 

 and where microscopical examination has failed to reveal their presence, 

 Nocard recommends injecting into a young dog sub-cutaneously or intra- 

 venously, 5-10 c.c. of the blood of the dog under examination. If it be a 

 case of piroplasmosis the inoculated animal as a rule develops an acute piro- 

 plasmosis, and after the third to the fifth day the parasites multiply in its 

 blood. 



4. Piroplasma equi. 



Equine piroplasmosis is a common disease in the Transvaal, where it 

 has been studied by Theiler : it is very similar to " red-water " in cattle. 

 The parasite was discovered by Laveran ; it is smaller than P. bigeminum, 

 and as generally seen is round or oval, pyriform bodies being very rare. The 

 disease is transmitted by a tick, Rhipicephalus evertsi (Theiler). 



Piroplasma equi has been found in Madagascar by Thiroux in horses suffering 

 from a chronic disease known by the inappropriate name of Osteomalacia. 



Equine piroplasmosis is a common disease in India (Patton), where it is 

 said to be transmitted by biting flies or mosquitos (Williams). 



