XII 



DISEASES AND PARASITES OF MAMMALS, 

 AND POISONING FROM PLANTS 



Probably all species of mammals have various diseases and parasites. 

 Hundreds of books, bulletins, pamphlets and articles in periodicals, 

 discussing diseases of domesticated mammals, have been published 

 far too many to be even listed in this volume, and only a few of the 

 principal diseases may be mentioned briefly. Also there is an extensive 

 and much-scattered literature of the diseases and parasites of wild 

 mammals, only a few items of which may be herein mentioned for 

 purposes of illustration. Though diseases of domestic stock result in 

 great economic loss, on the other hand, diseases of certain destructive 

 wild mammals are sometimes distinctly beneficial to the human race, 

 because they serve to keep injurious animals in check. The subject of 

 mammals as disseminators of disease, especially of diseases which af- 

 fect human beings, is discussed in the next chapter, including rabies, or 

 hydrophobia, and tularemia, or rabbit fever. 



Let us first turn briefly to some serious epidemic and non-epidemic 

 diseases of domestic stock. In 1915 it was estimated that the total loss 

 to stock raisers from livestock diseases in the United States amounted 

 to $212,000,000 annually, the chief diseases being as follows: 1 



Hog cholera $75,000,000 Contagious abortion $20,000,000 



Texas fever 40,000,000 Scabies, cattle and sheep . . . 4,600,000 



Tuberculosis 25,000,000 Glanders 5,000,000 



Black-leg 6,000,000 Other livestock diseases 22,000,000 



Anthrax 1,500,000 Parasites 5,000,000 



To this must be added a large but unknown amount of indirect loss 

 due to the expense of fighting disease, quarantine, etc. In the United 

 States, in 1915, one percent of all the cattle slaughtered under federal 

 inspection were infected with tuberculosis, and the meat partly or 

 wholly condemned. It will be noticed that the greatest loss in the 

 foregoing list is from hog cholera, upon the study and control of 

 which large sums of money have been expended for many years, with 

 great ultimate success, hog-raising being far less hazardous than form- 



1 Mitchell, Animal diseases and our food supply, Yearbook U. S. Dept. Agric. for 

 , PP. 159-172. 



