Mycoplasma iowae infection in chicks.

Five groups of light hybrid SPF chicks were inoculated at 1 day of age with different strains of Mycoplasma iowae via the right thoracic air sac and right foot pad. Control birds were inoculated with sterile mycoplasma broth at the same sites. The chicks were observed daily for clinical signs and at 3 and 6 weeks approximately half the birds in each group were killed for postmortem, histological and cultural examination. At 6 weeks serological studies were also carried out. Clinical signs were minimal although in three of the five infected groups there was impaired ability in some birds to flex the digits of the feet. On postmortem examination the most common finding was exudative tenosynovitis affecting the digital flexor tendons above and below the hock joint. Histological examination of such tendons revealed inflammatory changes with heterophil infiltration together with plasma cells and lymphoid foci. Some tendons exhibited sigmoid folding which was apparently associated with rupture of that tendon. M. iowae was reisolated from chicks in only three of the five infected groups and there was no obvious correlation with lesions. Rapid serum plate agglutination tests using an antigen made from the type strain gave one positive reaction out of 34 infected birds tested but an antigen prepared from another strain (serovar J DJA) gave 11 positive reactions.