98 POULTRY DISEASES AND THEIR TREATMENT. 



"Young fowls and fowls of the fine breeds are especially liable 

 to roup. While some poultrymen maintain that birds once hav- 

 ing suffered from roup never take the disease again, most of the 

 experimental evidence tends to show that no acquired immunity 

 exists, as sometimes happens after other diseases. Some fowls 

 are, however, naturally immune, and never take the disease. 

 In the course of our own experiments, a white chicken which 

 had never had roup, was inoculated with repeated and large 

 doses of the roup germ, but without effect." 



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 

 3 species of bacteria and one protozoan. 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 com- 

 ing from infected yards or houses. While a source of infection 

 i" necessary for the production of the disease it does not appear 

 to attack birds when the mucous membrane is in a healthy con- 

 dition. 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 exposure to cold and dampness causes ca- 

 tarrh in the unaffected birds. Thus in infected flocks an out- 

 break of roup usually follows catarrh caused by exposure and 

 this fact has led some poultrymen to think that the disease may 

 be caused directly by exposure. In some flocks it appears annu- 

 ally with the cold damp weather of late autumn and breaks out 

 again at every radical change of temperature and moisture con- 

 ditions throughout the winter. Vigorous and properly nour- 

 ished birds are better able to resist catarrh and consequently 

 roup than those that are delicate and improperly fed. 



Treatment. The best treatment is prevention. The disease 

 can be prevented by stopping all sources of infection. Some 

 things to keep in mind are : 



