Comparative infectivity of oocysts and bradyzoites of Toxoplasma gondii for intermediate (mice) and definitive (cats) hosts
Comparative infectivity of oocysts and bradyzoites of Toxoplasma gondii for intermediate (mice) and definitive (cats) hosts
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DOI：
10.1016/j.vetpar.2006.03.018
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发表时间：
2006-08-31
影响因子：
2.6
通讯作者：
Dubey, J. P.
中科院分区：
文献类型：
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作者：
Dubey, J. P.
速殖子、缓殖子（在组织包囊中）和子孢子（在卵囊中）是弓形虫的三个感染阶段。开放前期（初次感染后至排出卵囊的时间）随猫摄入弓形虫的阶段而变化。在摄入缓殖子后的开放前期（pp）较短（3-10天），而在摄入卵囊或速殖子后的开放前期（pp）较长（18天或更长）。缓殖子向速殖子和速殖子向缓殖子的转变在弓形虫的生活史中具有重要的生物学意义，并提出了用阶段性转变研究的方法。在本研究中，卵囊和缓殖子释放的组织囊的弓形虫，TgCkAr 23，猫和小鼠的感染性进行了比较。将卵囊或缓殖子的10倍稀释液经口给予猫，并经口和皮下给予小鼠。在29只猫中，每只猫喂食1- 1000万个卵囊，只有一只猫排出卵囊，pp为23天;所有猫均无症状。相反。所有口服或皮下给予相同10倍稀释卵囊的小鼠均死于弓形虫病。结果证实，卵囊对猫的感染性低于对小鼠的感染性，卵囊对猫无致病性。在41只猫中，每只喂食1-1000个游离缓殖子，15只脱落卵囊，PP为4-9天，所有猫均保持无症状。缓殖子经口给药对小鼠的感染性比皮下给药低约100倍。结果证实了这一假设，即在猫的PP是阶段，而不是剂量依赖性的，和T弓形虫的传输是最有效的猫消耗组织囊肿（食肉动物）或当中间宿主消耗卵囊（粪口传播）。(c)2006 Elsevier B. V.保留所有权利。
Tachyzoites, bradyzoites (in tissue cysts), and sporozoites (in oocysts) are the three infectious stages of Toxoplasma gondii. The prepatent period (time to shedding of oocysts after primary infection) varies with the stage of T gondii ingested by the cat. The prepatent period (pp) after ingesting bradyzoites is short (3-10 days) while it is long (18 days or longer) after ingesting oocysts or tachyzoites. The conversion of bradyzoites to tachyzoites and tachyzoites to bradyzoites is biologically important in the life cycle of T gondii and it has been proposed that the pp can be used to study stage conversion. In the present study, infectivity of oocysts and bradyzoites released from tissue cysts of a recent isolate of T gondii, TgCkAr23, to cats and mice was compared. Ten-fold dilutions of oocysts or bradyzoites were administered orally to cats, and orally and subcutaneously to mice. Of the 29 cats each fed 1-10 million oocysts only one cat shed oocysts and the pp was 23 days; all cats remained asymptomatic. In contrast. all mice administered the same 10-fold dilutions of oocysts either orally or subcutaneously died of toxoplasmosis. The results confirm that infectivity of the oocysts to cats is lower than for mice and that oocysts are non-pathogenic for cats. Of the 41 cats each fed 1-1000 free bradyzoites, 15 shed oocysts with a short pp of 4-9 days, and all remained asymptomatic. The infectivity of bradyzoites to mice by the oral route was approximately 100 times lower than that by the subcutaneous route. The results confirm the hypothesis that the pp in cats is stage and not dose dependent, and that transmission of T gondii is most efficient when cats consume tissue cysts (carnivory) or when intermediate hosts consume oocysts (fecal-oral transmission). (c) 2006 Elsevier B.V. All rights reserved.