CHAPTER IX 
AVIAN DIPHTHERIA AND BIRD POX 
General discussion. The group of pathological conditions re- 
ferred to by various authors under such designations as simple ca- 
tarrh, colds, contagious catarrh, influenza, coryza, roup, canker, 
diphtheria and bird pox present a complicated subject for discussion. 
The pathological features presented by the lesions of the mucosa 
of the fowl’s head in the conditions described as roup or diphtheria, 
have been concisely summarized by Moore. He studied the disease 
in the eastern United States and has described three stages or va- 
rieties of lesions as follows: 
“(1) An exudate of a serous or muco-purulent character in the con- 
junctiva or nasal cavities. Ordinarily this condition cannot be recognized 
in the mouth. The mucosa in these cases is apparently but slightly 
altered. 
“ (2) The mucosa over a small or larger area is covered with a spreading 
exudate of a grayish or yellow color. It is firmly attached to the mucous 
membrane and when removed leaves a raw, bleeding surface. Sections 
through this exudate and the subadjacent tissues show that the epithelial 
layer is destroyed, and the underlying tissue infiltrated with cells. The 
extent of the infiltration varies in different individuals. 
“ (3) The mucosa is covered with a thick mass of exudate, varying in 
color from a milky white to a lemon yellow or brown. It is easily re- 
moved, leaving a more or less granular and healed surface. This sloughed 
mass is frequently dried at its margins to the adjacent tissue. It emits 
a strong putrid odor, due to decomposition. The drying of the margins 
prevents the fowl from expelling the exudate after it becomes separated 
from the underlying tissue.” 
In the far West and South, the lesions described will commonly 
be found accompanied by the tumor-like lesions known as chicken 
pox or epithelioma contagiosum. 
The earlier studies of the etiology of the diphtheritic lesions of 
fowls extending over a long period have resulted in a mass of con- 
clusions, in the main contradictory and confusing. Various authors 
have ascribed the lesions as due to gregarina, chlamdyozoa, coccidia 
and numerous species of bacteria. 
The discovery that the filterable virus of chicken pox is capable 
of causing diphtheritic lesions has now received abundant confirma- 
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