CHAPTER II. 



ACUTE INFECTIOUS DISEASES WITH LOCALIZA- 

 TION IN CERTAIN ORGANS. 



EPITHELIOSIS INFECTIOSA AVIUM. 



Contagious Epithelioma. Chicken-pox. Diphtheria. 

 Roup. Canker. 



Prevalency and Distribution of the Disease.— The disease 

 affects nearly all birds, especially chickens, turkeys, pea- 

 fowls, pheasants, guineas, pigeons, sparrows, quail, etc., 

 but is not so frequently observed in ducks, geese and swans. 

 The malady is widely distributed, appearing in practically 

 all countries where birds are found in any considerable 

 numbers. In the United States infectious epitheliosis is 

 quite prevalent, especially in the northern states during the 

 colder months. In the fall when the cold, damp weather 

 begins outbreaks occur quite commonly, and poultrymen 

 often refer to the early inception of the disease as a "cold." 

 The intensity of the disease usually increases until the 

 warm weather makes its appearance, when it diminishes and 

 lies dormant, to reappear at the first cool, damp weather in 

 the fall when the birds are more closely confined. 



Etiology. —Evidence obtained by experiments indicates 

 that a filtrable virus is the primary causative agent, and 

 that the more or less severe complicating conditions are 

 induced by secondary infection, of which a bacillus, probably 

 the Bacillus diphtheria? columbarum of Loeffler, seems to be 

 the most constant. 



Pathogenesis. — Transmission of this disease is not very 



difficult. Usually about 70 per cent, of healthy birds will 



show symptoms of the disease after associating with an 



affected one for a short time. Actual contact is not neces- 



38 



