Cubas-Atienzar Ana I, Hide Geoff, Jiménez-Coello Matilde, Ortega-Pacheco Antonio, Smith Judith E
Ecosystems and Environment Research Centre, School of Environment and Life Sciences, University of Salford, Salford, M5 4WT Manchester, UK.
Ecosystems and Environment Research Centre, School of Environment and Life Sciences, University of Salford, Salford, M5 4WT Manchester, UK.
Vet Parasitol Reg Stud Reports. 2018 Dec;14:191-199. doi: 10.1016/j.vprsr.2018.10.009. Epub 2018 Oct 29.
Toxoplasmosis is a zoonotic disease of worldwide distribution. The parasite exhibits strong geographical patterns of strain variation with contrasting high levels of diversity across South America and restricted variation across North America. Little is known about the diversity of strains in the transitional area between the two continents. Here we present data on the prevalance and diversity of Toxoplasma gondii in the Yucatan peninsula of Mexico, through a study in commercially reared pigs. A survey of 12 farms found evidence of circulating T. gondii DNA in 125 of 632 blood samples (19.8%, CI: 16.7%-23%). In addition, 46 tongue samples were collected from culled animals and 16 of these were positive for T. gondii DNA and 3 were positive in mouse bioassay. PCR-sequencing was used to generate genotyping data from blood and tissue samples. Four loci (SAG1, 2, 3 and GRA6) were reliably amplified and revealed a high diversity among Yucatan strains with evidence of recombination and novel alleles. Sequencing data from the four loci was achieved in eight samples each of which had a different genotype. The predominant allelic type was atypical, in relation to the dominant strain types (I, II, III), the number of allelic variants being 27 (I, II-III, u-1-25), 20 (I, III, u1-18), 6 (I, III, u1-4) and 11 (I, II, u1-9) for the SAG1, SAG2, SAG3 and GRA6 loci respectively. Phylogenetic analysis showed that T. gondii strains from Yucatan shared alleles with strains originating from both North and South America. Our findings are consistent with data from other regions of Central America and suggest the genetic population structure of the parasite, with significant levels of allelic variation and recombination, constitutes a reservoir from which new strains may emerge. Positive bioassay results (7.5%) indicate that consumption of undercooked pork could be a potential T. gondii infection risk to humans.
弓形虫病是一种分布于全球的人畜共患病。该寄生虫表现出强烈的地理菌株变异模式，南美洲各地的多样性水平较高，而北美洲的变异则受到限制。关于两大洲过渡区域菌株的多样性，人们了解甚少。在此，我们通过对商业养殖猪的研究，呈现了墨西哥尤卡坦半岛弓形虫的流行情况和多样性数据。对12个农场的调查发现，在632份血液样本中的125份（19.8%，置信区间：16.7%-23%）检测到了弓形虫DNA的循环证据。此外，从被扑杀动物身上采集了46份舌头样本，其中16份弓形虫DNA呈阳性，3份在小鼠生物测定中呈阳性。采用聚合酶链反应测序法从血液和组织样本中生成基因分型数据。四个基因座（SAG1、2、3和GRA6）得到可靠扩增，显示尤卡坦半岛菌株具有高度多样性，存在重组和新等位基因的证据。从四个基因座获得的测序数据来自八个样本，每个样本都有不同的基因型。与主要菌株类型（I、II、III）相比，主要等位基因类型是非典型的，SAG1、SAG2、SAG3和GRA6基因座的等位基因变体数量分别为27个（I、II-III、u-1-25）、20个（I、III、u1-18）、6个（I、III、u1-4）和11个（I、II、u1-9）。系统发育分析表明，来自尤卡坦半岛的弓形虫菌株与源自北美洲和南美洲的菌株共享等位基因。我们的研究结果与中美洲其他地区的数据一致，表明该寄生虫的遗传种群结构具有显著水平的等位基因变异和重组，构成了一个可能产生新菌株的储存库。阳性生物测定结果（7.5%）表明，食用未煮熟的猪肉可能会给人类带来潜在的弓形虫感染风险。
