98 Pori.TKV DISKASES AND THEIR TREATMENT. 



■■\'()Uii,i;' fowls aii<l f()\\]'- of the liiK" Ijreeds are especially liable 

 to roup. W hilo sonic poulUymcn maintain that birds once hav- 

 ing suffered from r(~)U]) ne\'cr take the disease again, most of the 

 experimental evidence tentl> to .show that no acquired immunity 

 exists, as sometimes hai)pens after other diseases. vSome fowls 

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

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

 iiad never had roup, was innculated 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 possiblv 1)\' the food and 

 drink contaminated b\- the diseased birds. It may be introduced 

 into a flock 1)\- tlie 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 }ards 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 

 catarrli. When a Hock once becomes infected the l)irds 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 unaft"ected birds. Tims in infected flocks an out- 

 break of roup usually follows catarrh caused by exposure and 

 this fact has lerl s(^me poultrymcn to think that the disease may 

 be caused directly ])y exposure. In some flocks it a])])ears 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 jiroperly nour- 

 ished liirds are better able to resist catarrh and consequently 

 roup than those that arc delicate and improperl)- fed. 



TrcalDh'iit. The best treatment is prevention. The disease 

 can be prevented by stopping all sources of infection. Some 

 things to kee]") in mind are : 



