LARYNGOTRACHEITIS VIRUS IN CHICKENS

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Abstract
Inoculated intranasally into unanesthetized baby chicks the virus remains limited to the nasal fossa, produces acute desquamation of all nasal epithelia, results in functional recovery of the respiratory epithelium, but leaves important residual abnormalities. From the earliest recognizable lesions through 4 1/2 months'' convalescence, the principal changes are: Initial lesions, or small syncytia of intranuclear "inclusions", first identifiable in the mucociliated cells of the shallowest portion of the epithelium at about 21 hr. postinoculum (the inner surface of the maxillary conchal scroll). Acute sloughing, (about 3 to 7 days), marked by: spread of lesions from cell to cell via multinucleated "giant cells" which progressively slough and desquamate respiratory, olfactory, and sinus epithelia, epithelial neural elements and blood vessels; appearance of numbers of eosinophilic leukocytes along the basement membrane at the sites of lesions just previous to sloughing; intensive infiltration of the submucosa with small lymphocytes after sloughing begins; histochemical change in the intracellular mucus of the cells which comprise the syncytia: this mucus stains with Alcian blue alone when stained with AB-PAS; [Alcian blue- Periodic acid Schiff]; and all cartilages of the maxillary conchae become flaccid, and the cell nuclei and matrix lose both basophilic and Alcian blue staining properties, effects which recede by about the 8th day. Repair (about 8 to 21 days), marked by rapid initial spread of a sheet of epithelial cells over the infiltrated submucosa, appearance of numbers of plasma cells circulating in the tissues, formation of encapsulated secondary nodules, and mucosal adhesions. Convalescence (about 1 to 4 1/2 months when experiments terminated), marked by functional restoration of the mucociliary lining of the nasal fossa. However, at 4 1/2 months 8 specimens all show complete metaplasia of the olfactory organ (end nerves, supporting cells, and glands of Bowman) to mucociliated epithelium, all show abnormal formation and alignment of mucous acini, and about 50% have severe persistent sinusitis.