Diseases of the Respiratory System 159 



viduals recover, but others continue weak and have a chronic 

 form of the disease for months ; during which time they con- 

 tinue to disseminate the contagion. 



This disease is distinguished from diphtheria by the ab- 

 sence of the thick, tough, and very adherent newly formed 

 membranes (false membranes) in the nostrils, mouth, and 

 throat which are characteristic of the latter. 



The Course of the Disease. — The course of roup is usually 

 of long duration. A simple, putrid discharge from the nose 

 may stop in three or four weeks. But generally the symp- 

 toms last for months. When the eyelids become swollen 

 and tumors appear, the case is usually chronic. Affected 

 birds may be better for a few days or weeks, and then be- 

 come very weak again. Damp, cold weather usually inten- 

 sifies the disease. 



It is well known that fowls may be more or less sick from 

 roup for one or even several years and these birds should 

 have the greatest care and attention, or else be killed at once, 

 for they are generally the cause of new outbreaks. Once 

 introduced, roup may remain in a flock for many years. The 

 first cold and moist nights of the fall and early winter 

 cause all kinds of catarrhs, which in many instances are 

 followed by roup. Roup spreads rapidly in the winter 

 time and may attack from 10 to 90 per cent of the fowls in 

 a flock. Towards spring, the disease gradually disappears ; 

 during the summer months, a few birds remain chronically 

 affected ; and then the first cold nights give the disease a 

 fresh start. 



There is a great deal of difference in the susceptibility of 

 fowls to the disease. Young fowls and finely bred fowls are 

 especially liable to contract it. Some birds are apparently 

 naturally immune and never take the disease. Others ap- 

 parently have it in a mild form and completely recover, 

 having thereby acquired an immunity. 



