A Study of Infectious Laryngotracheitis Virus. II. The Duration and Degree of Immunity Induced by Conjunctival Vaccination

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Abstract
Preparation and standardization of the 146 strain of infectious laryngotracheitis virus for use in a conjunctivally administered vaccine are discussed. Birds were vaccinated by applying one drop of vaccine, containing 100 ELD50, onto the conjunctival sac. "Takes," in the form of swollen and closed eyelids, developed 5-7 days post-vaccination. All birds appeared normal by the 11th day after immunization. Adverse effects were not detected during safety and potency tests. Cockerels, immunized by the conjunctival route, were refractive to intrasinusoidal challenges of 1,000 ELD50 of a heterologous infectious laryngotracheitis virus isolate for 372 days. Neutralization indices were obtained against both the immunizing and challenge infectious laryngotracheitis virus strains with serum collected 372 days post-vaccination.