672-675, Iowa State Univ Press, 1994. Birds are in good general body condition. The tracheal mucosa is hemorrhagic and the lumen contains fibrinonecrotic exudate. Moderate mixed miscellaneous bacteria were recovered from the tracheal exudate. Increased mortality rates are usually attributable to occlusion of bronchial airways with caseous exudate.
Mortality rates can vary with virus strain pathogenicity and partial protection by vaccination.
We included larynx in our morphologic diagnosis because several of the slides contained a small section of larynx. Also, pseudomembranes were variably present among the sections. Several gallinaceous birds, including pheasants and peafowl, also are susceptible. Canaries may be infected as well. Unlike other herpesviruses, natural transmission is exclusively aerogenic.