598 ACUTE INFECTIOUS DISEASES 



the disease spreads from one location to the other, and the 

 difference in the lesions is due to the difference in the struct- 

 ure of the tissue involved. 



General Symptoms. In the early stages before much 

 secondary infection takes place, there are no marked general 

 symptoms. Later marked general symptoms appear. The 

 birds show dulness, assume a sitting posture, wings are 

 held pendent, plumage becomes rough and the patients 

 show much depression. The comb and wattles grow 

 bluish-red in color, later pale and cold. In the colder 

 climates the disease often assumes a subacute or chronic 

 form, while in warmer climates the acute form is more often 

 observed. Frequently, however, the disease assumes the 

 character of a chronic catarrh. 



Diagnosis. The disease usually makes its first appearance 

 in the fall and often occurs as the cutaneous form. It may 

 be overlooked, especially if the birds are on the range. 

 The mucous membrane form usually makes its appearance 

 soon after housing for the winter. The sneezing, mouth- 

 breathing, occluded nostrils and an occasionally inflamed 

 eye are significant, especially when rapidly spreading 

 through the flock. Soon after a few will refuse food and 

 appear depressed. 



It must also be suspected when similar symptoms appear 

 after adding new birds to a healthy flock or birds returned 

 from shows. 



A peculiar characteristic and offensive odor is associated 

 with this disease and poultrymen familiar with it often 

 recognize the disease from the odor alone. The same odor 

 is given off by cultures. 



Differential Diagnosis. Wounds on the skin around the 

 head, usually pick-inflicted, appear suspicious, but these 

 heal rapidly without extensive thickening. An injury to 

 the eye, even though serious, will not cause the formation 

 of the characteristic yellow deposit. Difficult respiration, 

 rarely seen in more than one bird in a flock, may be due to 

 several causes, and those observed persisted for some time 

 without affecting the general health of the bird. 



