The effect of route of inoculation on protection by killed vaccines in chickens

The effect of various routes of immunization on protection against challenge by virulent agents was examined in chickens. Chickens were immunized intratracheally, intranasally, per os, by crop gavage, and intramuscularly. Agents examined were killed Haemophilus paragallinarum, Mycoplasma gallisepticum, and infectious bursal disease virus. Results of immunization by intratracheal administration were equivalent to those produced by parenteral administration. All vaccines effectively induced production of serum antibodies against pathogens, and all immunized chickens were protected against infection by each pathogen.