Fig. 1. Veterinary research is constantly in the fight against diseases that affect animals. Here 

 the chronic respiratory disease agent is being isolated and propagated in embryonating eggs. 



CHRONIC RESPIRATORY DISEASE 



By H. VAN ROEKEL and O. M. OLESIUK * 



RESPIRATORY infections in 

 poultry have become a major 

 threat to the poultry industry 

 during the past twenty years. Even 

 though these infections have the 

 same symptoms and lesions, labor- 

 atory investigations have now iden- 

 tified them as distinct and specific 

 diseases, thus making possible the 

 development of effective control 

 methods. 



Within recent years a new respir- 

 atory disease has been identified 

 among poultry in Massachusetts. 

 It differs from infectious bronchitis 

 and Newcastle disease in that its 

 rate of spread through a flock is 



* Dr. Van Roekel, Research Professor, Veterinary 

 Science, assisted by O. M. Olesiuk, Assistant 

 Research Professor. 



slow and its course is of long stand- 

 ing. Because of these features it 

 has been called "chronic respiratory 

 disease." 



Viral-like Agent 



The identification of the disease 

 is economically important to the 

 poultry industry. At present, it has 

 been identified in widely scattered 

 areas in the United States but its 

 distribution and prevalence are not 

 known. 



The disease is caused by a viral- 

 like agent, the nature of which is 

 not fully understood. It is difficult 

 to study the behavior and charac- 

 teristics of this agent because it is 

 not readily isolated in embryonat- 

 ing eggs or in special culture media . 



