Members of this class constitute a 

 fairly cohesive group of blood cell para- 

 sites of vertebrates. They are small in 

 comparison with the Plasmodiidae. They 

 are piriform, round, amoeboid or rod- 

 shaped, depending in part on the genus. 

 They occur in the erythrocytes, and some 

 genera occur in the leucocytes or histio- 

 cytes as well. Pigment (hemozoin) is not 

 formed from the host cell hemoglobin. 

 No spores are formed, and no flagella or 

 cilia are present. Locomotion is by body 

 flexion or gliding. Reproduction is asex- 

 ual, by binary fission or schizogony. 

 Budding has also been said to occur, but 

 the processes described under this name 

 are actually binary fission with the forma- 

 tion of 2 daughter cells or schizogony 

 with the formation of 4. The existence of 

 sexual reproduction is dubious, altho it 

 has been described by earlier authors. 

 The Piroplasmasida are heteroxenous; the 

 known vectors are ixodid or argasid ticks. 



The systematic position of this group 

 is still uncertain, and varies with the 

 authority. The position given it here 

 seems reasonable. 



There is a single order, Piroplas- 

 morida. It contains 2 families, both of 

 which contain parasites of domestic 

 animals. 



Chapter 11 



THE 

 mOPLASMASm 



FAMILY BABESIIDAE 



Members of this family are relatively 

 large, piriform, round or oval parasites. 

 They occur in the erythrocytes, where 

 they reproduce asexually by binary fission 

 or schizogony. The vectors are ixodid or 

 argasid ticks. Binary fission, schizogony 

 and sexual reproduction have been des- 

 cribed in the tick, but the existence of 

 sexual reproduction is dubious, and Reich- 

 enow (1953) believed that schizogony is 

 simulated by repeated binary fissions. 



By far the most important genus in 

 the family is Babesia, species of which 



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