RESUMEN
A descriptive epidemiologic study was designed to test an impression that infections of Echinococcus granulosus in dogs, sheep, and human beings were concentrated in central Utah, and to determine when and how the parasite was introduced into the state, which factors were involved in the distribution of the cestode, and which factors increased either a person's risk of infection of the number of people at risk. Data were secured by review of available records, interviews, questionnaires, and field observations. It was found that 37 of 39 infections in human beings, and seven of eight counties with endemic hydatid disease in dogs and sheep, are located in central Utah. Possible factors responsible for the increasing number of people at risk were use of local people as herders, the existence of community herds, and specific dog management practices. Determinants such as trailing sheep between seasonal pastures, association of sheepmen from several counties on winter range, and sheep marketing practices undoubtedly influence distribution of infections in dogs and sheep.