770 



Piroplasmosis of Cattle. 



cattle, tlie piroplasma appear in the blood in about eight clays, 

 and in some cases fever and hemogiobinuria sets in (Fig. 133). 

 The results of experiments conducted with nj^nphs which as 

 larvae sucked blood from affected cattle, are similar, and the 

 disease may be also produced with larvae, which have wintered 

 in the open (the infectiousness of the sexually mature ticks 

 of the species described here is as yet questionable). 



According to these experimental results, which correspond 

 with practical observations, the natural infection of cattle 

 occurs usually on previously infected pastures in which one 

 of the mentioned species of ticks are present, and in which 

 the larvae and nymphs originated from females which had the 

 opportunity to suck blood from affected animals or in which 

 the n\miphs themselves in a previous stage of development 

 sucked infected blood. As these ecto-parasites subsist as a 



Fig. 133. Fever curve in p'lroj)! osmosis of cattle. After placing several thou- 

 sand infected larvae on tlie animal. (After Kossel, Schiitz, Wol)er & Miessner.) 



rule in marshy places, especially in forest pastures or near 

 forests and bushes, the disease usually affects cattle driven to 

 such pastures. On the other hand its annual reappearance 

 may be explained by the facts that the virus passes from the 

 impregnated female ticks to their progeny, and that they are 

 capable of offering considera])le resistance to unfavorable 

 weather conditions, especially the cold of Avinter. If at the 

 onset of w^armer weather the larvae have already hatched from 

 the eggs, the first cases of disease among cattle driven to in- 

 fected pastures usually appear after two weeks and, in case 

 the respective pasture was badly infected the previous year, 

 a great number of the animals may become affected within 

 a short time. With stable feeding, however, the disease is 

 observed only very exceptionally, and only in cases in which 



