654 A MANUAL OF BACTERIOLOGY 



differ from the Plasmodia in the following respects : absence of 

 pigment, non-fragmenting of the nucleolus, division into two or 

 four only, and frequency of extra -corpuscular forms. They cause 

 many diseases in animals, are conveyed by ticks, but are unknown 

 in man. (A piroplasma was described as the causative organism 

 of Rocky Mountain spotted fever by Wilson and Chowning, but 

 the observations appear to be erroneous, see p. 673.) The body 

 of a piroplasma is typically pear-shaped (Plate XXXI, a), but 

 rounded and rod forms occur. Two nuclear masses are present, 

 one larger than the other. 



The developmental cycle in the ticks has not been worked out, 

 but Koch observed peculiar rayed forms with P. bigeminum, 

 and Christophers x various developmental forms with P. canis. 

 Miyajima states that a piroplasma of Japanese cattle (apparently 

 P. parvum) in blood broth develops into typical trypanosome 

 forms. 2 



Piroplasma bigeminum. This is the parasite of the well-known 

 Texas fever of cattle, a disease which is characterised by fever, 

 emaciation, anaemia, hsemoglobinuria, and enlargement of the 

 liver and spleen. 



The disease causes considerable loss among cattle, and is met 

 with in various parts of the world, America, Australia, South 

 Africa, Malaya, the Philippines, the Roman Campagna, Greece, 

 Roumania, and North Ireland. 



In the acute type of the disease a small proportion (1-5 per 

 cent.) of the red corpuscles in the peripheral circulation contain 

 pairs of pyriform bodies 2-4 p. in length and 1-5-2 p, in largest 

 diameter. One end of each body is rounded, and the body 

 gradually tapers to a point at the other end, and the pair lie 

 close together, their tapering ends directed towards each other. 

 A dark spherical body is present at the rounded end of the parasite. 



Some of the young parasites exhibit amoeboid movements 

 when the blood is examined on a warm stage. In the internal 

 organs the parasites are more numerous ; in the kidney and 

 liver 10-25 per cent, of the corpuscles contain them, in the heart- 

 muscle 50 per cent. In the mild type 5-50 per cent, of the 

 corpuscles in the circulating blood may be infected at one time 



1 Brit. Med. Journ., 1907, vol. i, p. 76. 



2 Philippine Journ. of Science, vol. ii, 1908, p. 37. 



