CHAPTER XII. 



POULTRY DISEASES AND PARASITES. 



Maintenance of Health. — ^The conservation of vigor and 

 maintenance of health are fundamental problems of poultry 

 production. In the last analysis these constitute but a 

 single problem, for great vigor is only an abundant health. 

 The preceding chapters have been given up, for the most 

 part, to discussing methods of maintaining health, under 

 such divisions as breeding, feeding, and housing. 



In proceeding to a brief and practical discussion of the 

 more common poultry diseases, it cannot be too greatly 

 emphasized that constructive breeding, with rational feeding 

 and management, is the first and principal line of defence 

 against disease. This corresponds in a general way to the 

 construction and maintenance of a fireproof building. Flock 

 treatment to prevent the spread of disease that has somehow 

 gained entrance to the flock, corresponds to the efforts of 

 the firemen to save other buildings in the block, for even 

 "fire proof" buildings sometimes burn. Endeavoring to 

 cure a diseased individual corresponds to the efforts to save 

 a badly damaged building from complete destruction, with 

 this very important difference, that while fire in a building 

 may be entirely put out and the damage completely repaired, 

 a bird sick with contagious disease is seldom so completely 

 cured that it does not constitute a source of danger to its 

 flock mates, or so quickly cured that it is capable of complete 

 self repair. A sick fowl may usually be considered as 

 permanently damaged for productive purposes. Comparing 

 the small value of an individual fowl with the serious menace 

 to the entire flock of a bacillus-carrying, cured bird, it is 

 questionable whether it is ever advisable to attempt the 

 cure of birds infected with a contagious disease. 

 (480) 



