Abstract：
Toxoplasma gondii is a food-borne zoonotic parasite widespread in a variety of hosts, including humans. With a majority of infections in Europe estimated to be meat-borne, pork, as one of the most consumed meats worldwide, represents a potential risk for consumers. Therefore, we aimed to investigate the progress of T. gondii infection and tissue tropism in experimentally infected pigs, using different T. gondii isolates and infectious stages, i.e. tissue cysts or oocysts. Twenty-four pigs were allocated to treatment in four groups of six, with each group inoculated orally with an estimated low dose of either 400 oocysts or 10 tissue cysts of two European T. gondii isolates, a type II and a type III isolate. The majority of pigs seroconverted two weeks post-inoculation. Pigs infected with the type III isolate had significantly higher levels of anti-T. gondii antibodies compared to those infected with the type II isolate. Histopathological exams revealed reactive hyperplasia of the lymphatic tissue of all pigs. Additionally, a selected set of nine tissues was collected during necropsy at 50 dpi from each of the remaining 22 pigs for T. gondii DNA detection by quantitative real-time PCR. A positive result was obtained in 29.8 % (59/139) of tested tissues. The brain was identified as the most frequently positive tissue in 63.6 % (14/22) of the animals. In contrast, liver samples tested negative in all animals. The highest mean parasite load, calculated by interpolating the average Cq values on the standard curve made of ten-fold serial dilutions of the genomic DNA, corresponding to 100 to 104 tachyzoites/µL, was observed in shoulder musculature with an estimated concentration of 84.4 [0.0-442.5] parasites per gram of tissue. The study highlights the variability in clinical signs and tissue distribution of T. gondii in pigs based on the combination of parasite stages and strains, with type III isolates, particularly oocysts, causing a stronger antibody response and higher tissue parasite burden. These findings suggest the need for further investigation of type III isolates to better understand their potential risks to humans.
摘要：
弓形虫是一种广泛存在于多种宿主中的食源性人畜共患寄生虫,包括人类。据估计，欧洲大多数感染是肉类传播的，猪肉,作为世界上消费最多的肉类之一，对消费者来说是一个潜在的风险。因此,我们旨在研究弓形虫感染和组织嗜性的实验感染猪的进展，使用不同的弓形虫分离株和感染阶段，即组织囊肿或卵囊。二十四头猪被分入四组,每组六只,每组口服估计低剂量的400个卵囊或10个组织囊肿的两个欧洲弓形虫分离物，II型和III型分离物。大多数猪在接种后两周血清转化。感染III型分离株的猪具有明显更高水平的抗T。弓形虫抗体与II型分离株感染的抗体相比。组织病理学检查显示所有猪的淋巴组织反应性增生。此外,在50dpi的尸检期间,从其余22头猪的每只中收集一组选定的9个组织,用于通过定量实时PCR检测弓形虫DNA。在29.8%(59/139)的测试组织中获得阳性结果。在63.6%(14/22)的动物中,大脑被鉴定为最常见的阳性组织。相比之下,所有动物的肝脏样本测试均为阴性。最高的平均寄生虫负荷，通过在基因组DNA的十倍连续稀释的标准曲线上插值平均Cq值来计算，对应于100至104个速殖子/微升，在肩部肌肉组织中观察到，估计每克组织的寄生虫浓度为84.4[0.0-442.5]。该研究强调了基于寄生虫阶段和菌株组合的猪弓形虫的临床体征和组织分布的变异性，III型分离株，尤其是卵囊,导致更强的抗体反应和更高的组织寄生虫负担。这些发现表明，需要进一步调查III型分离株，以更好地了解它们对人类的潜在风险。
