Egg transmission of a respiratory isolate of Mycoplasma synoviae and infection of the chicken embryo.

Egg transmission of Mycoplasma synoviae (Ms) was demonstrated in broiler breeder birds of over 40 weeks of age from a commercial flock that had been infected during rearing and in birds experimentally inoculated before onset of lay. Infection of growing birds with Ms did not prevent egg transmission in adult life. The embryonated eggs of experimentally infected hens were less susceptible to infection by inoculation than those of specific pathogen-free birds. Some chicks with maternal antibody were found to be infected at hatching and in these maternal antibody was not mycoplasmacidal. Indeed by protecting the embryo maternal antibody may have promoted hatching of infected chicks.