304 



SPOROZOA. 



■fPiroplasma bigeminum, Gaiger, 1910, p. 66 ; Baldrey, 1910, 



pp. 569-79. 

 ■\Piroplasma {Babesia) bigeminum, Edwards, 1925, pp. 48-9. 

 Piroplasm.a bigeminum,, Minchin, 1912, p. 379, fig. 160 ; pp. 384—5, 



fig. 162 ; Castellani & Chalmers, 1919, p. 497 ; Velu, 1922, 



pp. 133-45, fig. 21 ; Hegner & Taliaferro, 1924, p. 304. 

 ■\Piroplasma bigem,inum,. Cooper, 1926 a, p. 96 ; 1926 b, pp. 314- 



15, pi. xviii, fig. 1. 

 Babesia bigemina, Wenyon, 1926, pp. 993-8, figs. 408, 410 A-J, 



pi. xviii, figs. 6-10; Knowles, 1928, p. 451, figs. 105, 106; 



Reichenow; 1929, pp. 1034-5, fig. 1019 ; Dennis, 1930, pp. 179- 



92, 2 pis. ; Kudo, 1931, p. 289, fig. 122, g. 

 -fEabesia bigem,ina. Cooper, 1931, pi. i, fig. 1 ; Ware, 1932, p. 31 ; 



Ray, 1938, p. 265. 



Largest of the known Piroplasms of cattle. Round, oval 

 or irregular, or pyriform and occurring in pairs, individuals 

 of the pair lying close together : the pear-shaped forms 

 extend across the diameter of the red corpuscle, which in cattle 

 measures from 5 to 6/i,. Occasionally four pear-shaped forms 

 are arranged in a fan-hke manner. MultipHcation takes place 



Fig. 147. — Babesia bigemina (Smith & Kilborne). ( X c. 3000.) 

 A, pear-shaped form ; B-F, multiplication by budding ; 

 G, two pear-shaped forms in a corpuscle ; H, four pear- 

 shaped forms in a corpuscle. (From Wenyon, after Nut tall 

 and Graham-Smith.) 



by a characteristic budding process, the buds remaining 

 attached by their pointed ends. Transmission by ticks. 



Dimensions. — Round forms 2-3 />t, in diameter ; pyriform 

 examples 2-4 ju, in length by 1-5-2/x in width. 



Remarks. — It was in the case of B. bigemina, the cause of 

 red- water fever in cattle in Texas, that Smith and Kilborne 

 (1893) demonstrated the possibility of transmission of proto- 

 zoal parasites by Arthropod hosts. Not only did they discover 

 that infection is transmitted by the tick, but that the eggs 

 of an infected tick are also infected, so that the second generation 

 of ticks hatched from such eggs may also be infective. This 

 was the first time that the role of Arthropods in the trans^ 

 mission of protozoal disease was demonstrated — several 



