Protozoan Cattle Fever. Texas Fever. Paludism of Cattle. 57 1 



such cases the animals should be shipped in carefully disinfected 

 cars, and before leaving they should be liberally oiled or larded 

 so that the ticks will not climb upon them, in being led to their 

 stable. They must be kept stabled until the febrile effects of the 

 injection have entirely passed, usually si month or more. 



d. Injection of Blood from Bodies of the Ticks. In view of the 

 difficulty of shipping infected blood without danger of contamina- 

 tion or sepsis, and the occasional accidents that happen to animals 

 injected with such blood outside of the infected area, attempts 

 have been made with dried blood, or that charged with antisep- 

 tics (calcium oxalate), or that had been frozen, but in every in- 

 stance the virulence of the pyroplasma was destroyed. Dalrymple 

 and Dodson availed of the blood drawn by mature ticks, which, 

 in their blood-gorged condition, were shipped to the points where 

 the injections were to be made. The mature ticks charged with 

 blood were taken from infected indigenous cattle, and at once 

 shipped. On their arrival they were washed externally with a 

 mercuric chloride solution (1:1000) to destroy any adherent 

 saprophytic or other bacteria, mashed in a sterilized mortar, with 

 a few cubic centimeters of boiled water and the fluid portion 

 drawn off and injected subcutem, into the animal to be protected. 

 From 3 to 12 mature female ticks were used for each animal. 

 The results were the same, only milder than when the blood of 

 the indigenous animal was used direct, and the subsequent toler- 

 ance of the pyroplasma proved satisfactory. 



It is difficult to explain the moderate effect of the considerable 

 mass of blood injected in such cases, as compared with the deadly 

 effect of the small amount that could come from the insertion of 

 the rostra of even 50 or 100 ticks. But perhaps the venomous 

 saliva instilled in concentrated form into the bites, protects the 

 pyroplasma in the very limited area, until it gains sufficiently in 

 numbers and force to hold its own even in the circulating blood. 



Limited Value of Artificially Induced Tolerance. It must be 

 added that all these measures for securing a partial immunity in 

 the individual animal, and which enable us to safely intro- 

 duce previously susceptible cattle into an infected district, virtu- 

 ally imply the continuance of the infection and infection bearer 

 (boophilus) for all time. They give no promise of the extinc- 

 tion of the bovine infection at even a remote future time, nor the 



