旋毛虫起源、进化及其宿主的感染来源与途径

Origin,Evolution and Its Source and Route of Their Host Infection of Trichinella

毛形属在距今27500万年前从毛形科中正式分化出来，各旋毛虫种间的遗传差异形成于距今的1500万～2000万年间。对亚洲和欧洲的共110个Trichinella spiralis地理隔离株的线粒体基因分析结果显示，欧洲地理株间仅存1个碱基差异，具有高度的一致性，而亚洲地理株间则具有8个碱基差异，存在明显的种内差异。依据线粒体累积变异速率计算，T．spiralis由亚洲传播至欧洲的时期大约在6000年～16000年以前。不同种旋毛虫对动物的感染具有一定的异嗜性，而宿主感染旋毛虫的途径则主要来源于水平传播，即食用感染有虫体的肉类；机械性传播，即经粪便、土壤、废水、食腐性昆虫的机械性传播；垂直传播，目前在人类、豚鼠中有检出报道。

Genus Trichinella was differentiated formally from Trichnellidae 275 million years（MY） ago, the genetic diversity among extant species of Trichinella accumulated within the last 15-20 MY. It was showed in the analytic result of mitochondrion gene among 110 T. spiralis geographic isolates, each specimen of European T. spiralis bears one base substitution, by contrast sampled Asian haplotypes differ by as much as 8 times that amount. According to the accumulated variation rate of chondrosome, T. spiralis spread from Asia to Europe about 6 000-16 000 years ago. Different species have different hosts. There are 3 ways of Trichinella infection to hosts, inducing horizontal transmission, that is eating the meat containing infec tive larvae ; mechanical transmission, i.e. through excrement, soil, waste liquid, scavenging insects; vertical transmission, it was reported in humans and guinea pigs.