The pathogen of Chronic Respiratory Disease(CRD) is Mycoplasma Gallisepticum(MG). The MG exists widely in chicken. So it usually brings considerable economic lose to the fowl aquaculture .

• 鸡毒支原体（Mycoplasma Gallisepticum，MG）感染，也称为鸡败血霉形体感染或慢性呼吸道病（Chronic Respiratory Disease,CRD）,因其在鸡群中广泛存在而造成很大的经济损失。