Sibley L David, Khan Asis, Ajioka James W, Rosenthal Benjamin M
Department of Molecular Microbiology, Washington University School of Medicine, Saint Louis, MO 63130, USA.
Philos Trans R Soc Lond B Biol Sci. 2009 Sep 27;364(1530):2749-61. doi: 10.1098/rstb.2009.0087.
Toxoplasma gondii is one of the most widespread parasites of domestic, wild, and companion animals, and it also commonly infects humans. Toxoplasma gondii has a complex life cycle. Sexual development occurs only in the cat gut, while asexual replication occurs in many vertebrate hosts. These features combine to create an unusual population structure. The vast majority of strains in North America and Europe fall into three recently derived, clonal lineages known as types I, II and III. Recent studies have revealed that South American strains are more genetically diverse and comprise distinct genotypes. These differences have been shaped by infrequent sexual recombination, population sweeps and biogeography. The majority of human infections that have been studied in North America and Europe are caused by type II strains, which are also common in agricultural animals from these regions. In contrast, several diverse genotypes of T. gondii are associated with severe infections in humans in South America. Defining the population structure of T. gondii from new regions has important implications for transmission, immunogenicity and pathogenesis.
刚地弓形虫是家畜、野生动物和伴侣动物中分布最广泛的寄生虫之一，它也常常感染人类。刚地弓形虫具有复杂的生命周期。有性发育仅发生在猫的肠道内，而无性繁殖则发生在许多脊椎动物宿主中。这些特征共同造就了一种不同寻常的种群结构。北美和欧洲的绝大多数菌株属于最近分化出的三个克隆谱系，即I型、II型和III型。最近的研究表明，南美菌株的基因更为多样，包含不同的基因型。这些差异是由罕见的有性重组、种群扩张和生物地理学形成的。在北美和欧洲，大多数被研究的人类感染是由II型菌株引起的，这些菌株在这些地区的家畜中也很常见。相比之下，几种不同基因型的刚地弓形虫与南美洲人类的严重感染有关。确定来自新地区的刚地弓形虫的种群结构对传播、免疫原性和发病机制具有重要意义。
