Distribution of species of Echinococcus (E. multilocularis, E. granulosus, E. oligarthrus, and E. patogonicus) was reviewed with special reference to the American continent. Human and domestic animal populations susceptible to echinococcosis are strikingly different in distribution. In the Americas, human disease is most prevalent in areas of intensive sheep husbandry, but the pattern of occurrence of hydatidosis may be altered as changes in the structure of the animal industry are introduced in developing countries. Recently published information and governmental reports on the status of human and animal infection reflect the global significance of the disease. The prevalence of infection shows no evidence of decline on any continent and may be rising in some areas with intensification and expansion of the livestock industry. Although effective control programs have been instituted in several island territories, the problem faced at the continental level has yet to be confronted. In South America, where hydatidosis probably reaches its greatest importance, high economic losses are incurred, and human disease has reached an alarming level. New control methods will have to be devised by carefully designed pilot programs, which must be critically analyzed to permit detection of changes in the prevalence of the disease when control measures are applied.
Present address: Calle 13 bis, No. 176 S San José, Costa Rica.