176 POULTRY DISEASES 



fully inoculated with contagious epithelioma, producing typ- 

 ical tissue changes upon the comb and wattles, or in the eye 

 and mouth, using the virus contained in the scabs removed 

 from the comb or wattles of sick birds for inoculation. Such 

 inoculations, however, do not serve to distinguish one disease 

 from the other, provided contagious epithelioma and diph- 

 theria or roup are separate and distinct diseases. 



Transmission of the 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 necessary, as is shown by the 

 spread of the disease at poultry shows. It has been noted 

 that in experimental work in using an infecting bird with 

 pox lesions, mucous membrane lesions of roup would appear 

 in the birds subjected to and developing the disease, and in 

 some cases where the roup type was used, pox lesions would 

 develop in the exposed contracting birds. 



Emulsions of scrapings from either cutaneous or mucous 

 membrane lesions injected subcutaneously, submucously or ap- 

 plied to scarified areas on the skin, would in some cases pro- 

 duce the generalized form of the disease, that is, both pox and 

 roup types combined. 



As hinted before in this disease, there are secondary in- 

 vaders which cause ago^ravated symptoms. These infections 

 manifest themselves after the filtrable virus has produced 

 more mild symptoms. The more common of these secondary 

 invaders is the Bacillus diphtlieriae columhariim of Loeffler. 



Therefore the filtrable virus is the necessary primary in- 

 vader which lowers the bird's resistance and thus prepares 

 the tissues for the invasion by the secondary organisms. 

 Neither factor alone will cause the typical disease. 



Mode of Spread. — Diphtheric roup is spread by birds intro- 

 duced into a flock from infected premises, and by exposure, as 

 at poultry shows. A chronic type of the disease in one or 

 more birds (carriers) in a flock may serve to infect others 

 when they are weakened by predisposing causes, as by ex- 

 posure to cold or dampness, or by roosting in drafts, or in 

 badly ventilated buildings. The beak bathed with nasal dis- 

 charges constantly contaminates the drinking water and feed. 



Symptoms. — There are three forms of the disease or the 

 lesions. Any or all may be present in the same bird. 



1. The nasal type. — This type is characterized at first by a 

 thin, watery discharge with an offensive odor characteristic of 

 roup. Later the catarrhal product becomes somewhat thicker 

 (mucopurulent) and the nostrils become occluded fglued 

 shut), and quite frequently there is a bulging of the sinus 



