Comparative studies on the biology and morphology ofEchinococcus granulosusfrom domestic livestock, moose and reindeer

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Abstract
1. As an intermediate host of the hydatid tapeworm in boreal North America, the moose is of relatively greater importance than other indigenous cervids (white-tailed deer, wapiti, barren-ground caribou) primarily because of a higher rate of infection in different individuals and the fertility of the hydatid cysts.2. The European reindeer introduced into north-western Canada is of considerable importance as an intermediate host where it occurs locally.3. Timber wolves are the important definitive hosts; no infections occurred naturally or were produced experimentally in the bobcat, Canada lynx, raccoon, fisher, marten, striped skunk or European ferret.4. A description using biological and morphological criteria is presented forEchinococcus granulosus granulosusin dogs, sheep and other domestic animals,E. g. borealissubsp.nov. in timber wolves, moose and other cervids indigenous to North America, andE. g. canadensisWebster and Cameron, 1961, in dogs and reindeer introduced into north-western Canada from Laplandic Norway.5. The rate of cystic growth, scolex production, infectability of timber wolves and dogs and prepatent period are similar for all three subspecies.6.E. g. borealisreached a gravid state in experimental red foxes (Vulpes fulva).7. Hydatid cysts developed only rarely in sheep fed eggs ofE. g. borealisorE. g. canadensis.8. Eggs ofE. g. granulosusproduced only one viable hydatid cyst in a series of experimental red deer (Cervus elaphus) and fallow deer (Dama dama).9.E. g. granulosus, E. g. borealisandE. g. canadensisare morphologically distinct, the most distinctive characters occur inE. g. canadensis.10. Besides the above andE. multilocularis, other species inEchinococcusare little known. Those recognized as being currently valid areE. lycaontis, E. ortleppi, E. felidis, E. cameroni, E. oligarthrus, E. cruziand possiblyE. patagonicus.The writers wish to thank Sir Charles Hercus and the other members of the Hydatid Research Committee for their interest and encouragement in the present study. Valuable discussion in the early stages of this work was had with Prof. A. M. Fallis, Director, Department of Parasitology, Ontario Research Foundation. Much of the field work was done with various members of the Ontario Research Foundation; Institute of Parasitology, McGill University; Canada Department of Agriculture; and Canada Department of Northern Affairs and Natural Resources, to whom we extend our thanks. Norwegian material was kindly provided by Dr Sven Skjenneberg, Statens Veterinaera Laboratorium for Nord-Norge. Technical assistance was provided by Messrs G. D. Page, D. V. Weston, Miss L. A. Duncan and Mrs B. R. Clarke.