This study aimed to genetically characterize Toxoplasma gondii isolates obtained from free-range chickens reared in the metropolitan region of the state of Rio de Janeiro, Brazil, and to evaluate the morbidity and histological changes associated with these isolates in mice. A mouse bioassay was used to isolate T. gondii from a pool of tissue samples (brain, heart, and thigh muscles) collected from 163 chickens. The 36 isolates obtained were genetically characterized by restriction fragment polymorphism (PCR-RFLP) analysis of the SAG1, 5′-3′SAG2, aSAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, Apico, and CS3 genomic regions. Seventeen atypical genotypes were identified and nine of them were reported for the first time. All identified genotypes caused clinical signs and histological changes in mice, with the majority being associated with high cumulative morbidity (65%) and severe or very severe histological changes (76%). The exclusive identification of atypical genotypes, with a predominance of new genotypes, indicates great genetic diversity of T. gondii in the region studied. In addition, the finding that all identified genotypes caused clinical signs and often severe histological changes in mice suggests potentially relevant virulence of these strains.

这项研究的目的是从刚在巴西里约热内卢州的大都市地区饲养的散养鸡中获得弓形虫的分离株，并评估它们在小鼠中的发病率和组织学变化。小鼠生物测定法用于分离弓形虫从一组163只鸡收集的组织样本（大脑，心脏和大腿肌肉）中提取。通过限制性片段多态性（PCR-RFLP）分析SAG1、5'-3'SAG2，aSAG2，SAG3，BTUB，GRA6，c22-8，c29-2，L358，PK1，Apico，和CS3基因组区域。鉴定出17种非典型基因型，其中9种为首次报道。所有确定的基因型都会引起小鼠的临床体征和组织学变化，其中大多数与高累积发病率（65％）和严重或非常严重的组织学变化（76％）相关。对非典型基因型的独家鉴定以及新基因型的优势表明弓形虫的巨大遗传多样性在研究的区域。另外，发现所有已鉴定的基因型都会引起临床体征，并且经常在小鼠中引起严重的组织学改变，这表明这些菌株可能具有潜在的相关毒力。