Haemophilus Infections in Chickens. II. The Pathology of the Respiratory Tract

Birds. Day-old White Leghorn chicks were obtained from an isolated flock of the University of California, and raised under isolation until the experiment began (when the birds were six weeks old). During the last five years, periodic examination of birds from the parent flock, by necropsy and serologic means, have failed to show evidence of infectious bronchitis, Newcastle disease, or infection with Mycoplasma gallisepticum. There was no evidence of clinical coryza in this flock. Prior to experimentation, all sera were tested for agglutinins against M. gallisepticum. Eighteen birds were exposed for 3 days to 2 chickens that had been infected intranasally with one drop of the eggpropagated strain 0083 of H. gallinarum.5 Two birds from the contact group were necropsied on the 3rd, 4th, 5th, 6th, 7th, 10th, 14th, and 21st day after initial exposure. At another time, 5 birds were examined 18 hours after exposure. Histology. Sections of nasal passages, sinuses, tracheas, and diseased air sacs were routinely taken at necropsy for histologic examination. The tissues were fixed in formalin,