Physiological characteristics of Echinococcus and their association with interventions against echinococcosis / 中华预防医学杂志

ABSTRACT

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.