Christensen J P, Henriksen S A
National Veterinary Laboratory, Copenhagen, Denmark.
Acta Vet Scand. 1994;35(2):165-72. doi: 10.1186/BF03548344.
Forty-seven piglets were inoculated with doses of 100 to 50,000 sporulated oocysts of Isospora suis. After 5-7 days oocysts were found in faeces. The patent period extended from 8 to 16 days. The shedding of oocysts showed a cyclic pattern with 2-3 peaks separated by intervals of approximately 5 days. Subpatent periods were often seen between the peaks. The level of oocyst shedding during the initial days of the patent period reflected, to some extent, the inoculation dose. However, a maximum of OPG at the 100,000 level was observed among one or more piglets from all groups, regardless of the inoculation dose. Among the majority of piglets inoculated with more than 100 oocysts, the highest OPG-figures were observed in the first peak of the cyclic pattern. Unlike this, the maximum of OPG was observed in the second peak of the cycle among 6 of the 7 piglets inoculated with 100 oocytes only. The triphasic pattern was most pronounced in the low dose group. The marked upscaling of oocyst production, as particularly registered in the low dosed groups, seams to explain at least part of the problems met under practical conditions, when trying to eliminate the transmission of oocytes between successive litters in the farrowing boxes. The cyclic excretion pattern and an apparent absence of autoinfection may indicate that the development of I. suis in the host includes several oocyte producing generations descending from the same initial infection. The presence of subpatent periods can probably explain the marked variation in OPG, as they are often recorded when examining faecal samples from piglets, even when the samples are originating from the same litter.
47头仔猪接种了100至50,000个猪等孢球虫有孢子卵囊。5至7天后在粪便中发现卵囊。排虫期为8至16天。卵囊排出呈周期性模式，有2至3个高峰，间隔约5天。高峰之间常出现亚临床期。排虫期最初几天的卵囊排出水平在一定程度上反映了接种剂量。然而，所有组中一头或多头仔猪在100,000水平时观察到最高每克粪便含卵囊数（OPG），与接种剂量无关。在接种超过100个卵囊的大多数仔猪中，在周期性模式的第一个高峰观察到最高OPG值。与此不同的是，仅接种100个卵母细胞的7头仔猪中有6头在周期的第二个高峰观察到OPG最大值。三相模式在低剂量组中最为明显。尤其是在低剂量组中记录到的卵囊产量显著增加，这似乎至少可以解释在实际条件下试图消除分娩箱中连续窝仔猪之间卵母细胞传播时遇到的部分问题。周期性排泄模式和明显不存在自身感染可能表明猪等孢球虫在宿主体内的发育包括从同一初始感染衍生的几代产生卵母细胞的过程。亚临床期的存在可能可以解释OPG的显著变化，因为在检查仔猪粪便样本时经常记录到这种变化，即使样本来自同一窝仔猪。
