棘球绦虫的主要生理学特点与包虫病控制方法的确立

Physiological characteristics of Echinococcus and their association with interventions against echinococcosis

由细粒棘球绦虫和多房棘球绦虫引起的棘球蚴病在全世界范围内流行，严重危害了人群的身体健康和社会发展。棘球绦虫生理学特点和生理指标是设计控制方案，解决诊断、治疗和预防等方面问题的基础。棘球绦虫有其复杂的生活史，需要寄生于两个哺乳类动物，经历不同发育的阶段（成虫、虫卵、包囊和原头蚴），每个阶段都有各自不同的生理学特点。本文系统总结和归纳了棘球绦虫主要生理学特点并强调了与控制方案有关的生理学参数。从生活史可以看出，棘球绦虫有两个感染阶段，一是虫卵,它是引起人和中间宿主原发性感染的唯一阶段；二是原头蚴，唯一感染犬等终末宿主的发育阶段。虫卵产生于寄生在终末宿主小肠里的成虫，虫卵在成虫体内的成熟时限是确定对犬驱虫间隔期的生理参数。细粒棘球绦虫在犬体内发育45 d产生发育成熟的虫卵。该期限是国外每年8次驱虫的基础。多房棘球绦虫在犬和狐狸体内感染28～30 d产生成熟的虫卵，控制泡球蚴的流行和传播，驱虫间隔期应该少于30 d。鉴于泡型包虫病和囊型包虫病在我国西部共流行，目前对犬每年12次驱虫，即成虫期前驱虫措施已经列入包虫病控制规划，广泛应用西部流行区。绵羊肝肺脏器内的包囊发育至成熟原头蚴需要12～15个月，采取羔羊上市的牧业生产方式因其羊体内的包囊不能产生原头蚴而成为囊型包虫病控制的有效方法。另外，棘球绦虫有其独特的生物学特点，比如有性繁殖和无性繁殖，包囊的单细胞层结构，胆盐调控原头蚴双向发育，包虫蚴在中间宿主体内长期感染的无症状反应等等，使其成为研究生物学和医学生物学问题的工具。囊蚴分泌的包囊液是研究诊断试剂的抗原来源，特异的六钩蚴表达基因是研制疫苗的重要发育阶段。随着高通量组学，包括基因组学、转录组学以及蛋白质组学的发展和应用，我们可以利用棘球绦虫的生理学特性寻找诊断试剂，研发预防疫苗和确定新型药靶。

Alveolar and cystic echinococcosis are important zoonotic diseases caused by the dog/fox tapeworms of Echinococcus granulosus and E. multilocularis, which are distributed in almost whole the world. The diseases remarkably impact on the people＇s health and economic development of communities. Echinococcus tapeworms need two mammalian animals to complete their lifecycle. The worms undergo different developmental stages （adult, egg/oncosphere, cyst, and protoscolex）. Each stage has its own distinct physiological characteristics. We summarize the characteristics and emphasize that some features that strongly impact on design of control program. Based on the lifecycle of these worms, two stages are infectious, one is egg the only stage for primarily infecting humans and intermediate host, and another stage is protoscolex, the only stage for infecting the definite hosts of the worms. Eggs are produced by the adult worms parasitized in the intestine of definite hosts. It takes 45 days for eggs becoming mature in dogs. With this feature of the tapeworm, New Zealand and Tasmania in Australia designed control program for deworming 8 times annually with an interval between deworms at 45 days. E. multilocularis takes 28-30 days in dog/fox producing mature eggs. Given that co-existence of E. granulosus and E. multilocularis in western China, a control measure so called ＂prepatent deworming control measure＂ has been used in these endemic areas with dosing worms in dogs every month. It normally takes 12-15 months for producing protosocleces in E. granulosus cysts in sheep. If meat markets attract most lambs, that is an effective measure for controlling cystic echinococcosis given that there are no protoscoleces produced from those lambs. In addition, Echinococcus has its own unique biological characteristics, such as sexual reproduction and asexual reproduction, single-cell layer structure of cyst, bidirectional development of protoscoleces induced by bile salts, and long term of infection causing host asymptomatic reaction make the parasites a models for addressing some biological and biomedical issues. And more, hydatid cyst fluid is the antigen resource for identifying diagnostic reagents; the specific gene expressed in oncospheres has been developed as an effective vaccine used for control program. With the development and application of high-throughput omics, including genomics, transcriptomics and proteomics, we can use the physiological characteristics of Echinococcus for searching diagnostic reagents, developing preventive vaccines and identify new drug targets.