Epidemiology and diagnosis of echinococcosis in Canada

TWO SPECIES OF ECHINOCOCCUS OCCUR IN CANADA: (1) E. multilocularis and (2) E. granulosus. E. multilocularis, originating in the Arctic, is spreading southwards and has reached Saskatchewan and the Dakotas. The original hosts are foxes but dogs and cats are alternatives. The larvae occur in field mice as multilocular microcysts containing numerous protoscolices, but in man the cysts are alveolar and sterile and resemble both in histology and growth a cholangiocellular carcinoma of the liver with metastases. Signs and symptoms are chronic and poorly defined. Diagnosis is difficult. Test antigens are not yet satisfactory. E. granulosus has a sylvatic cycle, the adult tapeworms living in wolves and dogs, while the larvae occur only in Cervidae and man. The cysts occur almost exclusively in the lungs as unilocular, macrocystic, relatively benign tumours, although abnormal complications can occur. The Casoni intradermal sensitivity test, its technique and interpretation are discussed.