Velmurugan G V, Dubey J P, Su C
United States Department of Agriculture, Agricultural Research Service, Animal and Natural Resources Institute, Animal Parasitic Diseases Laboratory, Building 1001, Beltsville, MD 20705-2350, USA.
Vet Parasitol. 2008 Aug 17;155(3-4):314-8. doi: 10.1016/j.vetpar.2008.04.021. Epub 2008 May 10.
Until recently, Toxoplasma gondii was considered to be clonal with very little genetic variability. Recent studies indicate that T. gondii isolates from Brazil are genetically and biologically different from T. gondii isolates from USA and Europe. However, little is known of the genetics of T. gondii strains from Africa. In this study, we genotyped 19 T. gondii isolates from chickens from six African countries (Egypt, Kenya, Nigeria, Congo, Mali, and Burkina Fasco) using 10 PCR-RFLP markers (SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico). The results revealed four genotypes. Thirteen isolates belong to the Type III lineage, five isolates have Type II alleles at all loci except apico and they belong to the Type II lineage. One isolate from Nigeria had atypical genotype. In general, these isolates were mostly clonal Type III and II strains that predominate in North American and European. DNA sequencing at several loci for representative isolates confirmed the results of PCR-RFLP genotyping. Taken together with recent studies of T. gondii isolates from Africa, it is clear that the three clonal lineages (Types I, II and III) predominate not only in North America and Europe, but also in Africa.
直到最近,刚地弓形虫都被认为是克隆性的,遗传变异性很小。最近的研究表明,来自巴西的刚地弓形虫分离株在遗传和生物学上与来自美国和欧洲的分离株不同。然而,对于来自非洲的刚地弓形虫菌株的遗传学却知之甚少。在本研究中,我们使用10种PCR-RFLP标记(SAG1、SAG2、SAG3、BTUB、GRA6、c22-8、c29-2、L358、PK1和Apico)对来自六个非洲国家(埃及、肯尼亚、尼日利亚、刚果、马里和布基纳法索)鸡体内的19株刚地弓形虫分离株进行了基因分型。结果显示有四种基因型。13株分离株属于III型谱系,5株分离株除apico外所有位点均具有II型等位基因,它们属于II型谱系。来自尼日利亚的一株分离株具有非典型基因型。总体而言,这些分离株大多是在北美和欧洲占主导地位的克隆性III型和II型菌株。对代表性分离株几个位点的DNA测序证实了PCR-RFLP基因分型的结果。结合最近对来自非洲的刚地弓形虫分离株的研究,很明显这三个克隆谱系(I型、II型和III型)不仅在北美和欧洲占主导地位,在非洲也是如此。