Dubey J P
US Department of Agriculture, Agricultural Research Service, Livestock and Poultry Sciences Institute, Beltsville, Maryland 20705-2350, USA.
Int J Parasitol. 1998 Jul;28(7):1019-24. doi: 10.1016/s0020-7519(98)00023-x.
This paper reviews recent studies on the life cycle of Toxoplasma gondii. Tachyzoites, bradyzoites, and sporozoites are the three infectious stages of T. gondii. Humans and animals become infected mainly by ingesting bradyzoites or oocytes. After ingestion, both bradyzoites and sporozoites convert to tachyzoites inside tissues. The conversion of tachyzoites to bradyzoites and bradyzoites to tachyzoites is of biological and clinical significance because bradyzoites are less susceptible to chemotherapy and reactivation of bradyzoites to tachyzoites is considered the cause of fatal toxoplasmosis in AIDS patients. Of all the methods currently available to assess stage conversion of T. gondii, feeding infective stages to cats is the most reliable method. Felidae, the definitive hosts of T. gondii excrete oocysts 3-10 days after ingesting tissue cysts/bradyzoites, > or = 18 days after ingesting oocysts, and > or = 13 days after ingesting tachyzoites.
本文综述了近期关于刚地弓形虫生命周期的研究。速殖子、缓殖子和子孢子是刚地弓形虫的三个感染阶段。人和动物主要通过摄入缓殖子或卵囊而感染。摄入后，缓殖子和子孢子在组织内均转化为速殖子。速殖子向缓殖子以及缓殖子向速殖子的转化具有生物学和临床意义，因为缓殖子对化疗不太敏感，而缓殖子重新激活为速殖子被认为是艾滋病患者致命性弓形虫病的病因。在目前所有可用于评估刚地弓形虫阶段转化的方法中，给猫喂食感染阶段是最可靠的方法。弓形虫的终末宿主猫科动物在摄入组织包囊/缓殖子后3 - 10天、摄入卵囊后≥18天以及摄入速殖子后≥13天排出卵囊。
