414 THE iMANAGliMENT AND FEEDING OF CATTLE 



infest others. The infection is not spread by means of 

 the saliva, breath, urine, or manure of infected animals. 



The ticks do not migrate from one animal to another. 

 The full-grown female tick, gorged with the blood of 

 the animal which has sustained her, usually a cattle 

 beast made immune to the disease, drops from the body 

 to the ground, and within about a fortnight has laid 

 from, say, 1,500 to 2,500 eggs. They hatch in from two 

 to eight weeks, according to the condition of the 

 weather. The young ticks, so minute as to be scarcely 

 visible at first, are nevertheless very active. They crawl 

 up the grass and other forms of vegetation and cling to 

 these, where they are able to live for three to four 

 months in the absence of live stock. From the pastures 

 they reach the legs of cattle grazing on them and crawl 

 up to their feeding grounds, that is, the parts where the 

 skin is thin, as the inside of the thighs and flanks and 

 portions of the udder and escutcheon. Except in cool 

 weather, they attain full size in from three to four weeks, 

 and are ready to infect pastures. In some instances 

 symptoms of the fever are manifest within ten days of 

 the exposure. Usually, but not always, from 30 to 40 

 days elapse from the time that cattle which bring the 

 ticks pass over the pastures before the outbreak occurs 

 on the other cattle that have been exposed. 



When cattle from without are taken into the in- 

 fected areas, they usually contract the disease the first 

 summer. Young cattle may survive, especiallv calves, 

 but mature animals of whatever class will nearlv all 

 perish. Calves and other animals which recover are 

 practically immune. When the infection is carried by 

 tick-infested animals beyond the permanently infected 

 areas, the pastures, roads, and inclosures where they 

 have been are dangerous to susceptible cattle. The ticks 

 may also be conveyed in litter from cars which have 

 carried infested animals. 



