Studies on the Helminth Fauna of Alaska XX. The Histogenesis of the Alveolar Larva of Echinococcus Species

Abstract

A detailed description of the day-to-day development of the alveolar-type larva of Echinococcus sp. occurring on St. Lawrence Island, is presented. The larva of the St. Lawrence Island cestode attains its alveolar form by proliferation of exogenous secondary vesicles, which explains its rapid invasion of host tissue and its malignant effect. It is concluded that ability of Echinococcus sp. from St. Lawrence Island to produce secondary vesicles exogenously constitutes the main difference between its larval development and that of E. granulosus. It is considered specifically distinct from E. granulosus on the basis of larval development and host species occurrence (in rodents) of the larval stage.