The fox as a definitive host of Echinococcus and its role in the spread of hydatid disease.

In the first part of this discussion of the significance of the fox in the epidemiology of hydatid disease in man, the author reviews the literature on vulpine echinococciasis. He points out that the evidence available from field surveys and laboratory observations suggests that the fox is not a definitive host of Echinococcus granulosus-the parasite responsible for the most common form of hydatid disease in man-but is a host of E. multilocularis, which is found in parts of Europe and Asia, in the islands of the Bering Sea and in Alaska, and is known to be the causal agent of alveolar hydatid disease.In the second part, the author presents the results of experimental infestation of the European red fox (Vulpes vulpes) with the Australian strain of E. granulosus. These results indicate that a few tapeworms became established in some of the foxes, but were retarded in growth (as compared with their growth in the dogs used as controls) and failed to reach sexual maturity (production of ova) even 112 days after infestation. The author therefore concludes that the fox plays no role in the spread of hydatid disease caused by E. granulosus in Australia.Finally, the author discusses the etiology of two autochthonous cases of alleged alveolar hydatid disease in man in Australasia, putting forward two alternative hypotheses to explain their occurrence.