3D 



8 



TEXAS FEVER 



liable to be on the ground continuously. In estimating the 

 time to elapse after the exposure to the tick infested field, 

 before the disease will appear, it is necessary, therefore, to 

 determine the exact stage in the life cycle of the ticks at the 

 time when the animals come in contact with them. 



Small quantities of the blood from immunized cattle in 

 the tick infested district, when injected into susceptible 

 animals either intravenously or beneath the skin, will produce 

 the disease. While this mode of infection rarely if ever 

 occurs in the natural order~of events, it may happen that in 



case of certain 





^ 



*H,ftS«: 



^. 



Fig. 97. Eggs and young tick, jitst hatched 

 {Stnith). 



operations bits of 

 blood may be car- 

 ried directly from 

 a southern to a 

 northern animal 

 thus inoculating 

 the latter with the 

 disease. 



In the fall of 



1898 two cases occurred in the practice of Dr. Ambler of 

 Chatham, N. Y. The owner had his animals dehorned in 

 December and soon afterward two fatal cases of Texas fever 

 developed. The Piroplasma and the characteristic lesions 

 were present. Inquiry revealed the interesting fact that the 

 two animals which sickened and died were dehorned immedi- 

 ately after two imported southern cattle. The owner was not 

 aware of the fact at the time that these were southern bred 

 cattle, as he had bought them of a dealer in \'ermont. More 

 recently another case of this disease produced in the same way 

 has been reported. 



§ 269. Symptoms. In the acute type of the disease 

 which occurs during the hot summer months, the onset is sud- 

 den and usually all animals exposed to the same infection 

 together come down at the same time. The first indication of 

 the disease is a rise of temperature, at first higher in the after- 



