Pathogenicity studies in poultry with an undefined serotype of Mycoplasma.

Pathogenicity trials in poultry are reported with an isolate of mycoplasma, designated 'W8', which is serologically unrelated to Mycoplasma gallisepticum, M synoviae or M meleagridis. W8 killed fowl and turkey embryos when injected into the yold sacs of embryonating eggs. Infection of one-day-old fowls, turkeys and pheasants by the air sac route caused marked growth depression and a high incidence of osteomyelitis of the vertebral column in all species. A large proportion of infected turkeys and a smaller proportion of infected pheasants also developed chondrodystrophic changes of the long bones similar to those of turkey syndrome '65. Infection did not cause mortality or macroscopic air sacculitis. No obvious pathological changes occurred in fowls following W8 infection by the air sac route at two weeks of age and only minimal changes when infection was given at one week. Infection did not appear to spread to in-contact controls. W8 was recovered most frequently and in greatest profusion from the air sacs, tracheas, kidneys and vertebral columns of fowls and turkeys following air sac infection at one day of age.