Serological monitoring on layer farms with specific pathogen-free chickens

To monitor the existence of avian pathogens in laying chicken flocks, speci fic pathogen-free (SPF) chickens were introduced into two layer farms and r eared with laying hens for 12 months. SPF chickens were bled several times after their introduction and examined for their sere-conversion to avian pa thogens. As a result, antibodies to eight or ten kinds of pathogens were de tected in SPF chickens on each farm. Antibodies to infectious bronchitis vi rus (IBV), avian nephritis virus, Mycoplasma gallisepticum and M. synoviae were detected early within the first month. Antibody titer to IBV suggested that the laying chickens were infected with IBV repeatedly during the expe riment on both farms. However, antibodies to infectious bursal disease viru s and 6 pathogens were not detected.