Changing Concepts in the Microecology, Macroecology and Epidemiology of Hydatid Disease

Abstract

The ecology of hydatid disease can be considered to involve the interaction between two biological systems: those involving the intimate relationship of Echinococcus granulosus or E. multilocularis with the microenvironment of their definitive and intermediate hosts, which represents the microecology of these organisms and the inter-relationship of these definitive and intermediate hosts, both between themselves and with their external environment, which represents the macroecology. Understanding the nature of the host-parasite relationship, and hence the epidemiology of the disease, involves a detailed knowledge of both these interacting systems. Recent advances in selected areas of the developmental biology of Echinococcus spp. in vivo and in vitro are reviewed, drawing attention to areas where gaps in our knowledge exist and where further work is particularly needed. Studies on the microecology have led to the now well-recognised concept that E. granulosus and (probably E. multilocularis) exist as a number of different strains, and the mechanism whereby these may originate and their significance is examined. The impact of these studies on our understanding of the overall ecology and epidemiology of hydatid disease and its control is discussed.