弓形虫是广泛分布的机会性致病原虫 ,速殖子和缓殖子之间的相互转换是其致病的中心环节。速殖子引起的急性感染可被宿主正常的免疫系统所抑制 ,从而转变为代谢、增殖缓慢的缓殖子 ,并以包囊的形式继续存在于脑、肌肉和视网膜等细胞中 ,形成隐性感染。当宿主免疫功能下降时 ,包 Toxoplasma gondii is a widely distributed opportunistic pathogenic protozoa, and the conversion between tachyzoites and bradyzoites is the central pathogenicity. Acute infections caused by tachyzoites can be suppressed by the host’s normal immune system, which translates into slowly metabolizing and slowly proliferating bradyzoites that continue to accumulate in cells such as brain, muscle and retina to form recessive infection. When the host immune function decline, the package