In vitro studies and host-specificity in Echinococcus.

Anatomical, biochemical and physical factors may play a part in determining the host-specificity of Echinococcus species. The author discusses the morphological differences between the duodenums of common potential carnivore hosts such as cat, fox and dog, and the biochemical differences in intestinal physiology-particularly the composition of the bile, which is important in the initial establishment of the parasite. After a consideration of the histochemistry, cytology and ultrastructure of adult and larval Echinococcus, he reviews the advances made in in vitro techniques in recent years. These are of particular importance to research in hydatid disease in view of the dangers associated with maintaining the highly infectious adult stage of Echinococcus in dogs and of the difficulty of obtaining a sufficiency of animals infected with the larval stage. The culture of cystic E. multi-locularis from protoscolices has now been achieved, and sexually mature adults of E. granulosus with 3 proglottids have been grown in vitro from protoscolices; with the latter, the major factor inducing growth in a strobilar direction is the continuous contact of the rostellum with a protein substrate.