DISEASES OF THE LOWEK ANIMALS 



ing the ticks of southern cattle. If this can be 

 accomplished the last difficulty will be over- 

 come. 



Contagious pleuro-pneumonia was at one 

 time one of the most fatal scourges of cattle. 

 By the experimental inoculation of cows the 

 contagious nature of the disease was discovered. 

 This was done while the disease was prevalent 

 in the Eastern states ; but with this knowledge 

 gained it was possible to prevent its spread to 

 the great cattle ranges of the West. A similar 

 study of foot-and-mouth disease has resulted 

 in diminishing its prevalence, and preventing 

 its transmission to man. 



Vaccination for the prevention of black-leg 

 among cattle has practically eliminated the dis- 

 ease. Before this treatment was begun the 

 mortality among herds afflicted was 10 to 25 

 per cent, each year. The loss of young cattle 

 in the United States was 100,000 head yearly. 

 In the first year succeeding the introduction of 

 vaccination for this disease the loss was reduced 

 to 0.6 per cent., a saving of 94,000 head of 

 cattle, worth about two million dollars. To ac- 

 complish this, fresh animals which had died of 

 the disease had to be secured to make the vac- 

 cine; occasionally a calf had to be infected ar- 



165 



Pleuro- 

 pneumonia. 



Foot-and- 

 mouth 

 disease. 



Black-leg. 



