Echinococcosis: an emerging or re-emerging zoonosis?

The aim of this review is a critical discussion of factors actually or pote ntially contributing to persistence or emergence of echinococcosis in human s. Alveolar echinococcosis (AE), a life-threatening infection of humans, is caused by a larval stage of Echinococcus multilocularis. The adult parasit e inhabits the intestine of foxes and other carnivores and has a wide distr ibution in the northern hemisphere (North America and northern and central Eurasia). Recent surveys in central Europe have extended the known geograph ical occurrence of E. multilocularis in foxes from four countries at the en d of the 1980s to at least 11 countries in 1999. Cases of human AE previous ly regularly reported from only four countries are now recorded from seven countries, but the annual incidences are low. Since adequate information fr om earlier surveys is not available, it is not possible to conclude if the new findings reflect a recent extension of the parasite's range or just the first identification of hitherto unnoticed endemic areas. Evidence of para site spreading has been reported from North America and Japan. Factors with the potential of enhancing the infection risk for humans in the future inc lude increasing fox populations and parasite prevalences, progressing invas ion of cities by foxes, the establishment of urban cycles of the parasite, and the spill-over of the E. multilocularis infection from wild carnivores to domestic dogs and cats. In view of the potential severity and fatality o f AE in humans health authorities should initiate internationally coordinat ed countermeasures. Although control programmes against human cystic echino coccosis (CE), caused by E. granulosus, have been established in some count ries and effective control strategies are available, the parasite has still a wide geographical distribution affecting many countries of all continent s. Thus, human CE is persisting in many parts of the world with high incide nces, and in some areas it is a re emerging problem. For example. alarming increases of the number of human cases have been reported from Bulgaria and Kazakhstan, and the People's Republic of China. Progress in control can on ly be expected if health authorities attribute a higher priority to this di sease and if ail modern diagnostic and control options (for example vaccina tion of intermediate host animals) can be used. (C) 2000 Australian Society for Parasitology Inc. Published by Elsevier Science Ltd. All rights reserv ed.