Approaches to food-based vaccines for domestic chickens

Domestic chickens were fed viral vaccines that were applied to the surface of food pellets. Responses were judged by the production of specific antibodies, and compared with the responses obtained when the same vaccines were given by conventional routes. Chickens responded similarly to commercial avian infectious encephalomyelitis vaccine given on food or by eyedrop when antibodies were measured by ELISA, and the vaccine virus spread by contact. Increasing the dose of oral vaccine tenfold gave a more rapid serological response but the levels of antibody were not increased. There was no serological response to commercial infectious laryngotracheitis virus vaccine given on food. An experimental avian adenovirus vaccine produced a serological response when given on food, but higher levels of antibody were produced in response to vaccination by eyedrop. The vaccine virus spread by contact. It was concluded that current avian infectious encephalomyelitis vaccines, and prospective recombinant vaccines based on avian adenovirus vectors, could be delivered on food.