DISEASES OF CATTLE 341 



Naturally this time varies according to the type of the attack. . As 

 the best results with these immunizing experiments have been ob- 

 tained 'in cool weather and with young cattle, it is recommended that 

 animals from 6 to 15 months old be selected for inoculation, and that 

 they be immunized during the late fall or winter months, in order 

 that they may enter tick-infested pastures in the spring without 

 danger. 



By Infesting with Tieks. Immunity may also be induced in 

 susceptible animals by placing a limited number of fever ticks upon 

 their 'bodies in order to produce the disease naturally. For this pur- 

 pose only animals less than 1 year of age should be used, as the 

 method is not applicable for older and more susceptible animals. 

 Upon the bodies of these young cattle from twenty-five to fifty seed 

 ticks should be placed, which in the course of about ten days will oc- 

 casion a rise of temperature and a mild form of Texas fever. When 

 the animal has entirely recovered from this attack, a second crop 

 double the number first used should be applied to the animal in 

 order to increase its power of resistance when pastured on infested 

 soil. In order to carry out this method successfully, a constant sup- 

 ply of seed ticks must be at hand. This can be accomplished by 

 placing the mature females in a Mason fruit jar among some dirt 

 and leaves and keeping them in a warm place. In a few weeks the 

 eggs will have been laid and hatched, and a number of seed ticks 

 will be present for use in infesting the cattle to be immunized. By 

 placing a few adult females in the jar every two months there will 

 always be a supply of these young ticks. This method of producing 

 immunity by controlled tick infestation is not so safe as blood inocu- 

 lation, since the quantity of germs injected can be more accurately 

 regulated by means of a syringe. 



Treatment. When the disease has broken out, all animals, the 

 sick as well as the healthy, should at once be removed to another 

 noninfected pasture. While this may not cut short the disease, it 

 may save the lives of some by removing them from the possibility of 

 being attacked by more young ticks. Removal from infected pas- 

 tures likewise prevents a second later attack in October or early in 

 November, which is caused by another generation of ticks. It is true 

 that sick natives infect with a new generation of ticks the pasture to 

 which they are removed, but these usually appear so late that they 

 have but little opportunity to dp any damage. Hence, sick natives 

 do not, as a rule, cause visible disease in other natives. 



It is of importance to remove all ticks, as far as this is possible, 

 from sick animals, since they abstract a considerable amount of 

 blood and thereby retard the final recovery. 



Medical treatment of the sick has generally been unsatisfactory, 

 although in chronic cases and those occurring late in the fall bene- 

 ficial results have followed. If the animal is constipated, a drench 

 containing 1 pound of Epsom salts dissolved in 1 quart of water 

 should be administered, followed by the sulphate of quinine in doses 

 of 30 to 90 grains, according to the size of the animal, four times a 

 day until the system is well saturated with it. Tincture of digitalis 



