Marshall P A, Hughes J M, Williams R H, Smith J E, Murphy R G, Hide G
Built and Human Environment Research Institute, School of Environment and Life Sciences, University of Salford, Salford M5 4WT, UK.
Parasitology. 2004 Jan;128(Pt 1):39-42. doi: 10.1017/s0031182003004189.
The relative importance of different transmission routes of Toxoplasma gondii has been a matter for debate. This ubiquitous parasite is generally thought to be transmitted by infective oocysts excreted by the definitive host, the cat. Ingestion of undercooked meat has also been considered an important route of transmission in many mammals while congenital transmission has generally been considered relatively rare. Experimental studies demonstrate the ability of T. gondii to be transmitted congenitally, but few studies have investigated the frequency of this transmission route in natural populations. We use PCR amplification of the SAG1 gene to investigate the frequency of congenital transmission in a wild population of mice (Mus domesticus) and show that congenital transmission is occurring in 75% of pregnancies in this population. Furthermore, for infected pregnant mice, transmission occurs to at least one foetus in 100% of cases while variable penetrance of congenital infection is observed. These high levels of congenital transmission in this wild population of mice, taken together with other recent data on congenital transmission in sheep, suggests that this phenomenon might be more widespread than previously thought.
弓形虫不同传播途径的相对重要性一直是一个有争议的问题。这种无处不在的寄生虫通常被认为是通过终宿主猫排出的感染性卵囊传播的。在许多哺乳动物中，摄入未煮熟的肉类也被认为是一种重要的传播途径，而先天性传播通常被认为相对罕见。实验研究证明了弓形虫先天性传播的能力，但很少有研究调查这种传播途径在自然种群中的发生频率。我们使用SAG1基因的PCR扩增来研究野生小鼠（小家鼠）种群中先天性传播的频率，并表明该种群中75%的怀孕存在先天性传播。此外，对于受感染的怀孕小鼠，100%的病例中至少有一个胎儿会发生传播，同时观察到先天性感染的可变外显率。野生小鼠种群中如此高的先天性传播水平，再加上最近关于绵羊先天性传播的其他数据，表明这种现象可能比以前认为的更为普遍。
