A fluorescent-antibody study of the pathogenesis of infectious laryngotracheitis.

A study of the pathogenesis of infectious laryngotracheitis (ILT) by the fluorescent-antibody (FA) technique in birds inoculated ocularly, intratracheally, by vent brush, and by aerosol revealed that the epithelium of the conjunctiva and respiratory tract are the tissues actively infected by natural routes of infection. The virus propagated at the sites of initial exposure but there was no evidence of spread by viremia. Viral antigen was detected 2-7 days postexposure and rarely thereafter. Birds infected intratracheally showed intense infection in the nasal turbinates, suggesting that high concentrations of virus were expelled as an aerosol from infected tracheas. Virus applied to the dorsal lip of the vent by drop or brush was rapidly transferred mechanically to the bursa of Fabricius; the epithelial lining between follicles and between follicular cortex and medulla was positive in FA tests 48-72 hours postexposure.