THE PIROPLASMATA 529 



deposition of melanin, and changes in, and enlargement of, the 

 spleen and liver, analogous to those occurring in malaria in man. 

 The Halteridium parasite, according to Schaudinn, is a stage in 

 the life-cycle of a trypanosome (see p. 494). 



Somewhat similar parasites are frequent in the blood of the lower 

 vertebrates (see Plate XXVI. &). 



The Piroplasmata x 



Syn. Pyrosoma, Bdbesia. 



The Piroplasmata form a somewhat anomalous group, but are 

 usually included in the Haemosporidia of the Sporozoa. They 

 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. 546). The body 

 of a piroplasma is typically pear-shaped (Plate XXVI. 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 has observed peculiar rayed forms with P. bigeminum, 

 and Christophers 2 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. 3 



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

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

 emaciation, anaemia, haemoglobinuria, 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 



1 See Hewlett, Trans. XlVtk Internal. Cong, of Hygiene, Berlin, 

 vol. ii, 1908, p. 146 ; Minchin in Allbutt's System of Med., ed 2, vol. ii, 

 pt. 2, p. 86. 



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



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



34 



