Dubey J P, Miller N L, Frenkel J K
J Exp Med. 1970 Oct 1;132(4):636-62. doi: 10.1084/jem.132.4.636.
Coccidian oocysts resembling those of Isospora bigemina were excreted by cats fed Toxoplasma. In order to identify these oocysts with Toxoplasma infectivity a number of critical comparisons were made. The appearance of oocysts and Toxoplasma infectivity was simultaneous in the feces of 23 of 24 adult cats, 3-5 days after feeding of Toxoplasma cysts; in the feces of 4 out of 9 cats, 7-10 days after feeding of trophozoites; and in 8 out of 17 cats, 20-24 days after feeding of cat feces containing oocysts. Oocysts and infectivity were present in similar numbers, and they disappeared simultaneously from the feces of cats. Oocysts and infectivity were also observed simultaneously in the feces of 9 kittens, 1-2 days old, fed Toxoplasma cysts. Oocysts could not be separated from infectivity by filtration, by continuous particle electrophoresis, or by density gradient centrifugation. Excystation of oocysts was followed by an increase in titer of Toxoplasma infectivity. Unsporulated oocysts in fresh cat feces were noninfectious to mice, but oocyst sporulation was associated quantitatively with the development of infectivity at different temperatures and conditions of oxygenation. Maximum oocyst sporulation at 48 hr correlated with the development of maximum Toxoplasma infectivity. 1 and 2% sulfuric acid, and 2.5% potassium dichromate were found to be the best preservatives for sporulation of oocysts and for the development of Toxoplasma infectivity. Low sporulation rates in 0.1% formalin, 20% ethanol, and in water were associated with low infectivity in these reagents. Neither Toxoplasma infectivity nor oocysts developed in 0.3% formalin, 1% ammonium hydroxide, or 1% iodine in 20% ethanol. Oocysts, sporocysts, and sporozoites were stained specifically with Toxoplasma antibody in the indirect fluorescent antibody test. Typical coccidian stages, schizonts, and male and female gametocytes were found in the epithelium of the small intestine of kittens fed Toxoplasma cysts. The classification of T. gondii is discussed in relation to that of other isosporan coccidia of cats and dogs. The term "Toxoplasma oocyst" is introduced and Toxoplasma is classified in the family Toxoplasmidae of the suborder Eimeriina. The species Isospora bigemina is restricted to dogs, and I. cati to cats. I. felis and so-called I. rivolta from cats were noninfectious to dogs, and did not confer immunity to subsequent infection with I. canis and I. rivolta from dogs.
给感染弓形虫的猫喂食后，其排出的球虫卵囊与双芽艾美耳球虫的卵囊相似。为了鉴定这些具有弓形虫感染性的卵囊，进行了多项关键比较。在给成年猫喂食弓形虫包囊3 - 5天后，24只成年猫中有23只的粪便中同时出现卵囊和弓形虫感染性；在给猫喂食滋养体7 - 10天后，9只猫中有4只出现；在给猫喂食含卵囊的猫粪便20 - 24天后，17只猫中有8只出现。卵囊和感染性数量相似，且它们同时从猫粪便中消失。在给1 - 2日龄的9只小猫喂食弓形虫包囊后，其粪便中也同时观察到卵囊和感染性。通过过滤、连续颗粒电泳或密度梯度离心都无法将卵囊与感染性分离。卵囊脱囊后弓形虫感染性滴度升高。新鲜猫粪便中的未孢子化卵囊对小鼠无感染性，但在不同温度和氧合条件下，卵囊孢子化与感染性的发展在数量上相关。48小时时卵囊最大程度的孢子化与弓形虫最大感染性的发展相关。发现1%和2%的硫酸以及2.5%的重铬酸钾是卵囊孢子化和弓形虫感染性发展的最佳防腐剂。在0.1%福尔马林、20%乙醇和水中孢子化率低与这些试剂中感染性低相关。在0.3%福尔马林、1%氢氧化铵或20%乙醇中的1%碘中，弓形虫感染性和卵囊均未发育。在间接荧光抗体试验中，卵囊、子孢子囊和子孢子被弓形虫抗体特异性染色。在给小猫喂食弓形虫包囊后，在其小肠上皮中发现了典型的球虫阶段、裂殖体以及雄配子体和雌配子体。讨论了弓形虫与猫和狗的其他等孢球虫的分类关系。引入了“弓形虫卵囊”这一术语，并将弓形虫分类在艾美耳亚目弓形虫科中。双芽艾美耳球虫仅限于狗，猫艾美耳球虫仅限于猫。来自猫的猫等孢球虫和所谓的里氏等孢球虫对狗无感染性，也不能使狗对随后感染来自狗的犬等孢球虫和里氏等孢球虫产生免疫力。
