Immunosuppression can increase the susceptibility of chickens to other disease-causing pathogens and interfere with the efficacy of vaccination against those pathogens. Chicken anaemia virus (CAV) and infectious bursal disease virus (IBDV) are common causes of immunosuppression in chickens. Immunosuppression was induced by experimental infection with either CAV or IBDV to assess the effect of immunosuppression on the efficacy of vaccination with Mycoplasma gallisepticum strain ts-304 against infection with virulent M. gallisepticum, a common bacterial pathogen of chickens worldwide. Birds were experimentally infected with either CAV or IBDV at 1 week of age, before vaccination and challenge with M. gallisepticum to examine the effect of immunosuppression at the time of vaccination, or at 6 weeks of age, after vaccination against M. gallisepticum but before challenge with virulent M. gallisepticum, to investigate the effect of immunosuppression at the time of challenge. All birds were vaccinated with a single dose of the ts-304 vaccine at 3 weeks of age and experimentally challenged with the virulent M. gallisepticum strain Ap3AS at 8 weeks of age. In immunosuppressed chickens there was a reduction in protection offered by the ts-304 vaccine at two weeks after challenge, as measured by tracheal mucosal thicknesses, serum antibody levels against M. gallisepticum, air sac lesion scores and virulent M. gallisepticum load in the trachea. Immunosuppressed birds with detectable serum antibodies against M. gallisepticum were less likely to have tracheal lesions. This study has shown that immunosuppression caused by infection with CAV or IBDV can interfere with vaccination against mycoplasmosis in chickens.

免疫抑制会增加鸡对其他致病病原体的易感性，并干扰针对这些病原体的疫苗接种效果。鸡贫血病毒（CAV）和传染性法氏囊病病毒（IBDV）是鸡免疫抑制的常见原因。免疫抑制是通过用 CAV 或 IBDV 实验性感染诱导的，以评估免疫抑制对鸡毒支原体ts-304疫苗接种对强毒鸡毒支原体感染的效果的影响，鸡毒支原体是全世界鸡的常见细菌病原体。在接种疫苗和用鸡毒支原体攻击之前，鸡在 1 周龄时用 CAV 或 IBDV 进行实验感染在接种疫苗时或在接种鸡毒支原体疫苗后但在用有毒的鸡毒支原体攻击前6 周龄时检查免疫抑制的效果，以研究攻击时免疫抑制的效果。所有鸡在 3 周龄时接种单剂 ts-304 疫苗，并在 8 周龄时用毒性鸡毒支原体菌株 Ap3AS 进行实验性攻击。在免疫抑制鸡中，攻击后两周 ts-304 疫苗提供的保护降低，这是通过气管粘膜厚度、血清抗鸡毒支原体抗体水平、气囊损伤评分和毒力鸡毒支原体测量的装入气管。具有可检测到鸡毒支原体血清抗体的免疫抑制禽类发生气管病变的可能性较小。这项研究表明，由 CAV 或 IBDV 感染引起的免疫抑制会干扰鸡支原体病的疫苗接种。