Epidemiology of echinococcosis

Various species and infraspecific forms of the cestode genus Echinococcus are causative agents of human echinococcosis. Pathology, epidemiology and geographical occurrence vary widely between the different Echinococcus taxa. As a general rule, those forms of echinococcosis that are transmitted mainly by wild animals are rather rare, due to limited contact between humans and wildlife. This is the case with alveolar echinococcosis (AE) caused by Echinococcus multilocularis, the 'fox tapeworm' (except in regions where domestic dogs are heavily involved in the lifecycle), and for the South American endemic species E. oligarthrus and E. vogeli. On the other hand, most forms of cystic echinococcosis (CE) are transmitted in domestic lifecycles involving dogs and livestock and constitute an emerging public health problem, especially in regions with extensive livestock husbandry and non-supervised slaughter.

This review focuses on two fields where a wealth of new information became available in recent years.

New data demonstrate that ' E. granulosus', the causative agent of CE, is an assembly of several, rather diverse, species and genotypes that show fundamental differences, not only in their epidemiology, but also in their pathogenicity to humans. This fact may explain the unequal distribution of high-endemicity areas for human CE on regional scales, which previously, has been attributed to differences in human behaviour. In addition, new data suggest that E. multilocularis is expanding its geographical range in the northern hemisphere, and its transmission is intensifying, e.g. in central Europe. Moreover, the lifecycle (involving wild foxes and rodents) is rapidly becoming 'urbanised' due to the recent establishment of fox populations in cities and towns. This shift from sylvatic to synanthropic occurrence is likely to result in an increased pressure on the human population of infection from AE.