Pathogenicity. 767 



Tenacity. Defibrinated blood kept at 8° C. is still virulent after 42 days, 

 while in the blood of cattle which have died or have been slaughtered by bleeding 

 the parasites remain alive for nine days. In the meat of slaughtered animals they 

 die at latest after twelve hours (Kossel, Schiitz, Weber & Miessner). Their rapid 

 death may possibly be due to lack of oxygen, as well as to the acid reaction of 

 the media which acts destructively on the piroplasma (Jackschath). 



Pathogenicity. The disease may be transmitted to healthy 

 cattle with blood containing piroplasma of affected animals. 

 After an intravenous, subcutaneous, or intramuscular inocula- 

 tion of 5-10 cc. of defibrinated blood, the parasites appear 

 usually in from 8 to 9 days in the blood of the inoculated ani- 

 mals. At approximately the same time the body temperature 

 becomes elevated, whereupon, during the reaction which lasts 

 for 7_or 8 days, the number of red blood corpuscles diminishes, 

 and in some of the cases hemoglobin appears in the urine. 

 After 25 to 30 days another febrile reaction follows, usually 

 with milder sjanptoms. In some animals the artificial disease 

 terminates in death, in the majority of cases however recovery 

 takes place in one to two weeks. In the blood of such recovered 

 animals the parasites may be demonstrated for a long time, 

 although in smaller numbers (in one case the blood was still 

 infectious 531 days after an artificial infection, and according 

 to Schroeder & Cotton the parasites may persist for 10 

 to 12 years). The disease may also be produced, although 

 with less certainty, by the injection of blood containing piro- 

 plasma into the serous cavities, lungs, l)rain, further by rubbing 

 upon the scarified skin; feeding is, on the other hand, always 

 ineffective. To an infection which causes a severe affection 

 among older cattle, cattle under one year of age usually react 

 only with an elevation of temperature lasting for several days. 

 Other species of animals are not susceptible to the infection. 



In America, Africa, Australia and Eastern Asia, as well 

 as probably in Southern Europe, the natural infection is trans- 

 mitted by the boophilus species, in middle and Northern Eu- 

 rope, on the other hand, by the Ixodes ricinus (I. reduvius). 



According to Salmon & Stiles, the carrier of the parasite is the bo- 

 ophilus annulatus, in North America, and, according to Motas, also in 

 Roumania; in South America, Cuba, Porto Rico, in the Philippines and 

 Australia, the B. anstralis, in South Africa the B. decoloratus (accord- 

 ing to Theiler also the Rh. appendicnlatus), act as carriers, while of the 

 sub-family ixodiae, the Ixodes ricinus has only been known with cer- 

 tainty to transmit the disease in Europe (according to Krageriid the I. 

 hexagonns acts in a similar way in Norway). 



The piroplasmas of cattle transmitted by various ticks in different 

 localities do not appear to be entirely identical, but probably represent 

 varieties of one species, and Liihe even separates them into two species, 

 apparently on account of the differences in size, namely, into the small, 

 Babesia bovis, which is found in Europe and North America, and the 

 larger, Babesia bigeminum, which is prevalent in America, Australia 

 and South Africa. Their difference appears also to be substantiated by 

 the fact that animals immunized against one of the varieties are not 

 always immune against the other varieties. This has been established 



