COMPARATIVE PATHOLOGY OF A CHICKEN-ORIGIN AND 2 DUCK-ORIGIN INFLUENZA-VIRUS ISOLATES IN CHICKENS - THE EFFECT OF ROUTE OF INOCULATION

Forty-nine 5-week-old chickens were inoculated by the intravenous (IV) , intratracheal (IT), or intranasal (IN) routes with either a chicken- origin or one of two duck-origin type A influenza virus isolates. Twel ve control chickens were inoculated with sterile chorioallantoic fluid . For all viruses, IV inoculation produced predominate lesions of rena l tubule necrosis (nephrosis) and nephritis, and influenza virus nucle oprotein was localized in nuclei and cytoplasm of necrotic renal tubul e epithelium. Chickens inoculated by the IT route, and to a lesser ext ent the IN route, had mild to severe tracheitis, bronchitis, and ventr omedial pneumonia associated with secondary bronchi but lacked renal t ubule necrosis and nephritis. These data indicate low-virulence avian- origin influenza viruses were nephrotropic during simulated systemic i nfection (IV inoculation) and pneumotropic during simulated local infe ction (IT and IN inoculation). Gross and histologic kidney lesions pro duced by IV inoculation of the chicken-origin influenza virus were sim ilar to changes reported in outbreaks of low-virulence influenza virus in laying chickens.