INFECTIOUS DISEASES OF CATTKE. 493 



If native cattle are placed upon pastures which have been infected 

 some time before with ticks, the disease will appear so much sooner, 

 because the young ticks may be already hatched and attack the cattle 

 at once. It will be evident, therefore, that the length of time elaps- 

 ing betAveen the exposure of native cattle on infected fields and the 

 appearance of the disease will depend on the date of original infec- 

 tion, and on the weather, whether cold or hot. When native cattle 

 are placed upon fields on which yomig ticks are already present, 

 they will show the fever in 13 to 15 days if the season be hot. 



The fever appears before the ticks have matured. In fact, they ariSi 

 still small enough to be OA^erlooked. In any case vei*y careful search 

 nhould be made for them in those places upon which they prefer to 

 locate — the tliighs, escutcheon, and udder. After the acute stage of 

 the fever has passed by. the ticks begin to swell up and show very 

 plainly. (PI. XL VIII, figs. 6 and 7.) 



PREVENTION. 



It is generally accepted that if southern cattle ai-e entirely free 

 from that species of tick known as Margaropus (or Boophilus) 

 mmulatus, they can be allowed to mingle with the most susceptible 

 animals without danger. Furthermore^ it has been learned from the 

 study of the life histoi-y of the cattle tick and from the fact that this 

 tick infests pastures only transiently, never permanently, and will 

 not mature except upon cattle or equines, that its exteiToination is 

 possible, and that the disease it causes may be prevented. The various 

 methods with these results in vieAv should be directed toward the 

 destruction of ticks on cattle as well as their eradication from the 

 pastures. The following discussion of methods of eradication is 

 largely taken from Fanners' Bulletin 378, which may be obtained 

 on application to the Secretary of Agidculture. 



METHODS OF ERADICATION. 



In undertaking measures for eradicating the tick it is evident that 

 the pest may be attacked in two locations, namely, on the pasture 

 and on the cattle. 



In freeing pastures the method followed may be either a dii-ect or 

 an indirect one. The former consists in excluding all cattle, horses, 

 and mules from pastures until all the ticks have died from starvation. 

 Tl>e latter consists in permitting the cattle and other animals to con- 

 tinue on the infested pasture and treating them at regular intervals 

 with oils or other agents destructive to ticks and thus preventing 

 engorged females from dropping and reinfesting the pasture. The 

 larvic on the pasture, or those which hatch fi'om eggs laid by females 

 already there, will all eventually meet death. Such of these as get 

 upon the cattle from time to time will be destroyed by the treat- 



