INFECTIOUS DISEASES OP CATTLE. 473 



ing the competition of the West. And it is the inherent capacity of 

 the South for greatly increasing its herds and enlarging its pasture 

 lands that makes the actual loss even secondary to the potential loss 

 due to restrictions necessitated by the presence of the cattle tick. 

 This potential loss maybe described as the difference between the 

 value of the cattle industry of the South to-day and the extent to 

 which this industry would be increased if farmers and ranchmen 

 were assured that their lands and cattle would not become infested 

 with fever ticks. ■ Could this assurance be given, the beneficial effects 

 would extend over the entire country, because the market of the 

 northern breeder would thereby become greatly extended. 



These appalling losses and annual sacrifices of the cattle raisers of 

 the infected district can be entirely effaced, and this at a small pro- 

 portionate cost; for, with enthusiastic stockmen, satisfactory State 

 legislation, sufficient money, and a trained corps of inspectors, the 

 cattle tick may be exterminated, and every dollar expended in this 

 work will be returned many fold during each succeeding year. 



The so-called period of incubation. — After the young ticks have 

 attached themselves to cattle the fever appears about ten days there- 

 after, in midsummer. When the weather is cool, as in autumn, this 

 period may be a little longer. The actual period of incubation may 

 be shorter than this, for if blood from a case of Texas fever be 

 injected into the blood vessels of healthy cattle the fever may appear 

 within five days. When cattle graze upon pastures over which south- 

 ern cattle have passed, the time when the disease appears varies 

 within wide limits. When the animals have been put upon pastures 

 immediately after southern cattle have infected them with ticks, it 

 may take from thirty to sixty days, or even longer, before the disease 

 appears. This will be readily understood when we recall the life 

 history of ticks. The southern cattle leave only matured ticks which 

 have dropped from them. These must lay their eggs and the latter 

 be hatched before any ticks can get upon native cattle. The shortest 

 period is thus not less than thirty days if we include ten days for the 

 period of incubation after the young tick has attached itself to native 

 cattle. When the infection of pastures with ticks has taken place 

 early in the season, or when this is cold, the period will be much 

 longer, because it takes longer for the eggs to hatch. 



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 between 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 young ticks are already present, 

 they will show the fever in thirteen to fifteen days if the season be hot. 



