160 Diseases of Poultry 



Etiology. — Several organisms have been isolated from the 

 lesions of birds suffering from roup/ Four of these have some 

 claim to be considered the cause of the disease. These include 

 three species of bacteria and one protozoon. There is also 

 some evidence that the cause of the disease is an invisible 

 virus. While the specific organism or organisms which cause 

 the disease are not certainly known its infectious nature is 

 well established. It is probably carried from one individual 

 to another in a flock, by the particles of dried secretion in the 

 air or possibly by the food and drink contaminated by the 

 diseased birds. It may be introduced into a flock by the 

 bringing in of birds from an infected flock, or by birds that 

 have contracted the disease at shows. Possibly it is sometimes 

 carried on the shoes or clothing of persons coming from in- 

 fected yards or houses, and possibly also by wild birds or 

 pigeons which fly from one poultry yard to another. While 

 a source of infection is necessary for the production of the 

 disease it does not appear to attack birds when the mucous 

 membrane is in a healthy condition. It is most apt to attack 

 birds that are suffering with catarrh. When a flock once 

 becomes infected the birds which develop a mild chronic form 

 of the disease serve as sources of infection whenever ex- 

 posure to cold and dampness causes catarrh in the unaffected 



^ Much confusion in regard to etiology of the diseases belonging 

 to general class commonly referred to as roup arises from the fact 

 that several investigators believe them to be stages in a single dis- 

 ease. A partial Ust of the literature on the etiology of roup and 

 diphtheria follows: Harrison, F. C, and Streit, H., loc. cit. Uhlen- 

 huth and Manteufel, loc. cit. von Betegh, L., loc. cit. von Katz, 

 S., loc. cit. Guerin, C, Ann. Inst. Pasteur, T. 15, pp. 941^52. 

 1901. Borrel. Compt. Rend. Soc. Biol. (Paris), T. 67, pp. 642-643. 

 1904. Galli-Valerio. Centbl. Bakt. Orig., Bd. 36, pp. 465-471. 1904. 

 Streit, H., Ztsch. Hyg. u. Infectionskrank. 46, pp. 407^62. 1904. 

 MuUer, R., Centbl. Bakt., etc., Orig. 41, pp. 423-426; 515-523; 621- 

 628. 1906. Bordet, J., et FaUy, V., Ann. Inst. Pasteur. T. 24. 

 pp. 563-568. 1910. 



