Toda Junko, Miyasaka Jiro, Osako Hideo, Murata Koichi, Yunus Muchammad, Amalia Reski, Soe Babi Kyi, Sato Hiroshi
Meat Inspection Center of Kumamoto Prefecture Office, 1314 Sosaki, Kikuchi, Kumamoto 861-1344, Japan; Public Health Emergencies Management Division, Kumamoto Prefecture Office, 6-18-1 Suizenji, Chuo-ku, Kumamoto 862-8570, Japan.
Meat Inspection Center of Kumamoto Prefecture Office, 1314 Sosaki, Kikuchi, Kumamoto 861-1344, Japan.
Parasitol Int. 2026 Feb;110:103144. doi: 10.1016/j.parint.2025.103144. Epub 2025 Aug 21.
Food poisoning caused by consuming raw horsemeat contaminated with Sarcocystis is a significant public health concern. Two morphotypes of sarcocysts in horsemeat, characterized by upright and folded villar protrusions, are typically identified as Sarcocystis fayeri and S. bertrami, respectively. However, recent molecular studies focusing on the ribosomal RNA gene (rDNA) and mitochondrial cytochrome c oxidase subunit I gene (cox1) have indicated a conspecific relationship between these two morphotypes using a limited number of specimens. To explore further genetic diversity in equid sarcocysts, cox1 and large-subunit (LSU) rDNA sequences were analyzed in sarcocysts extracted from horsemeat inspected from 150 horses (76 and 41 horses imported from Canada and France, respectively, and 33 horses reared in Japan). Sarcocysts were detected in the muscles of 71, 2, and 3 horses from Canada, France, and Japan, respectively. Fifty-eight sarcocysts underwent cox1 and the LSU rDNA sequencing. Newly obtained cox1 sequences (n = 53) and sequences labeled as equid S. bertrami, S. fayeri and S. asinus retrieved from GenBank (n = 53) exhibited conspecific relationships. Inter-individual variation in cox1 sequences was observed among various sarcocysts, even within a single host animal, although no intra-individual variation was observed. However, nuclear-embedded mitochondrial DNA (NUMT: cox1 pseudogene) sequences were obtained using inappropriate techniques using certain primers. The LSU rDNA of sarcocysts (211 cloned sequences from 54 sarcocysts) exhibited inter-individual and robust intra-individual variations, indicating significant intragenomic rRNA array mosaicism in S. bertrami. These findings confirmed the conspecificity of classically defined species without geographical subpopulations.
食用被肉孢子虫污染的生马肉导致的食物中毒是一个重大的公共卫生问题。马肉中两种肉孢子虫形态型，其特征分别为绒毛突起直立和折叠，通常分别被鉴定为费氏肉孢子虫和伯特拉米肉孢子虫。然而，最近针对核糖体RNA基因（rDNA）和线粒体细胞色素c氧化酶亚基I基因（cox1）的分子研究表明，使用有限数量的标本，这两种形态型之间存在同种关系。为了进一步探索马属动物肉孢子虫的遗传多样性，对从150匹马（分别从加拿大和法国进口76匹和41匹，在日本饲养33匹）的检验马肉中提取的肉孢子虫的cox1和大亚基（LSU）rDNA序列进行了分析。分别在来自加拿大、法国和日本的71匹、2匹和3匹马的肌肉中检测到肉孢子虫。对58个肉孢子虫进行了cox1和LSU rDNA测序。新获得的cox1序列（n = 53）以及从GenBank检索到的标记为马属伯特拉米肉孢子虫、费氏肉孢子虫和驴肉孢子虫的序列（n = 53）显示出同种关系。尽管未观察到个体内变异，但在各种肉孢子虫之间，甚至在单个宿主动物内，都观察到了cox1序列的个体间变异。然而，使用某些引物通过不适当的技术获得了核内线粒体DNA（NUMT：cox1假基因）序列。肉孢子虫的LSU rDNA（来自54个肉孢子虫的211个克隆序列）表现出个体间和强烈的个体内变异，表明伯特拉米肉孢子虫存在显著的基因组内rRNA阵列镶嵌现象。这些发现证实了经典定义的物种无地理亚群的同种性。
