This study aimed to investigate the occurrence of anti-Toxoplasma gondii antibodies in free-range chickens from Khorramabad, western Iran, and also to compare the performance of direct microscopy and semi-nested PCR in mice bioassayed with tissues from seropositive chickens. We investigated 97 serum samples from free-range chickens, using the modified agglutination test (MAT). Tissues from all seropositive chickens (MAT ≥ 1:10) were bioassayed in mice. All inoculated mice were examined by direct microscopy and a semi-nested PCR targeting the 529 bp repeat element (RE) of the parasite. Anti-T. gondii antibodies were detected in 21.6% of chicken sera. Eighteen of 21 (85.7%) seropositive chickens were positive in mouse bioassay using molecular DNA detection. However, biological forms of the parasite were isolated only from 11 (52.3%) seropositive chickens. Compared with semi-nested PCR, the sensitivity of direct microscopy was 62.1%. It can be concluded that although direct microscopy is a rapid and specific method for the detection of T. gondii, it does not detect the parasite in all experimentally infected mice. The low sensitivity of direct microscopy highlights the need for molecular techniques, such as RE-based semi-nested PCR, to increase the sensitivity of the mouse bioassay.

这项研究旨在调查来自伊朗西部霍拉马巴德的散养鸡中抗弓形虫抗体的发生，并比较用血清阳性鸡组织进行生物测定的小鼠中直接显微镜和半巢式PCR的性能。我们使用改良的凝集试验（MAT）研究了来自散养鸡的97个血清样品。对所有血清阳性鸡（MAT≥1:10）的组织进行了小鼠生物测定。通过直接显微镜检查和靶向该寄生虫的529 bp重复元件（RE）的半巢式PCR检查所有接种的小鼠。抗弓形虫在21.6％的鸡血清中检测到抗体。使用分子DNA检测在小鼠生物测定中，有21只血清阳性鸡中的18只（85.7％）呈阳性。但是，仅从11只（52.3％）血清反应阳性的鸡中分离出了该寄生虫的生物学形式。与半巢式PCR相比，直接显微镜的灵敏度为62.1％。可以得出结论，尽管直接显微镜检查是检测弓形虫的一种快速而特定的方法，但它并不能在所有实验感染的小鼠中检测到寄生虫。直接显微镜的低灵敏度凸显了对分子技术（例如基于RE的半巢式PCR）的需求，以提高小鼠生物测定的灵敏度。