Isolation of a Hemagglutinating Agent Distinct from Newcastle Disease from the Respiratory Tract of Chickens

A veterinarian described, by telephone, an unusual respiratory infection associated with a mortality of over 20% in a flock of fryers in the preceding 24 hours. The brood had been vaccinated when 4 days old with the B-1 strain of Newcastle disease (ND) vaccine given in the drinking water. No other vaccine was used. At 3 weeks old the flock became severely affected with a respiratory infection primarily involving the trachea. No other lesions were found on necropsy. Tentative diagnosis was ILT, and the tracheas of six birds were preserved in 50% glycerine and shipped to this laboratory for confirmation. The tracheas were moderately congested with petechial hemorrhages in the mucosa. There was considerable caseous exudate in the larynx and in the upper third of the trachea. The exudates and curetted mucosa of the tracheas were ground with sterile alundum in buffered saline. A portion of the suspension was left untreated, and the other was treated with 5000 units of penicillin and 10 mg of streptomycin per ml