Occurrence, Etiology, Natural Infeetiou. 



779 



The nature of the disease was determined bj- the investigations of Theiler m 

 the Transvaal, and of Koch in Buluwayo. 



Occurrence. The disease formerly existed in a latent form 

 along the East African coast, a severe outbreak however oc- 

 curred in 1900 when some very susceptible cattle were brought 

 to the Portuguese territory, to Beira (Koch; Creutz believes 

 that the Australian cattle introduced the virus). With the 

 severely affected cattle it was then spread into the interior 

 of Africa, especially to German East Africa, Natal, the Trans- 

 vaal and Rhodesia, where it caused great loss among the cattle 

 herds. 



Tn 190.5 about 500 farms were infeeteil in the Transvaal, and inside of a 

 year about 50,000 cattle succumbed to the ilisease. 



Etiology. The Piroplasma parvum (Babesia parva), the 

 smallest of piroplasma known at the present, nmy' be seen 

 in its characteristic form as a fine rod-shaped intracellular 

 body, which on one end contains a chromatin grannie, and fre- 

 quently appear arranged in cross or willow leaf -shaped form ; 

 ring and disc shapes also occur, while pear-shaped twin forms 

 are never present (Fig. 134). 



The disease cannot be prod-uced 

 artificially by the inoculation of 

 blood containing the parasite. 

 Health}' cattle withstand subcu- 

 taneous, intravenous or intraperi- 

 toneal injections of such blood with- 

 out harm, only when they are inocu- 

 lated two weeks later for the second 

 time, a rise in temperature sets in 

 immediately, and after 10 or 12 days 

 more a mild form of the disease ap- 

 pears, whereupon parasites may be 

 demonstrated in the blood. Meyer 

 obtained positive results by intro- 

 ducing large pieces of spleen from 

 affected animals into the al^dominal 

 cavity of healthy cattle, whereupon 



after 12 days the parasites appeared in the blood with a simul- 

 taneous rise in temperature. 



The natural, infection is transmitted by various ticks, 

 especially by nvmphs of the sexually mature forms of Phipice- 

 phalus appendiculatus, further l^y sexually mature forms of 

 Ehip. evertsi, Rhip. simus, Rhip. nitens, and Rhip. capensis, 

 which in the earlier stages of their development have sucked 

 blood from affected cattle. The parasite does not pass through 

 the egg of the tick as is the case with the piroplasma bigemmum, 

 neither is it transmitted from immune animals to health cattle 

 (Theiler, Lichtenheld). Its development in the body of the 



Fig. 134. PiropJasma parvnm. 

 Cattle blood, chromatin stain. 

 (After Theiler.) 



