Human Cystic and Alveolar Echinococcosis

Echinococcus granulosus causes human cystic echinococcosis, whereas Echinococcus multilocularis produces human alveolar echinococcosis. The latter constitutes a slowly progressive but often fatal disease. Cystic echinococcosis is widely distributed and represents a serious problem in sheep- and cattle-raising areas. Eggs released from gravid proglottids in faeces from definitive hosts may contaminate water, fruits, or weeds, and be eaten by humans or other intermediate hosts where a hydatid cyst develops. Histopathological and microscopic examinations, imaging techniques and serologic tests as well as molecular studies are used in diagnosis. Whenever possible, hydatid cysts should be removed surgically, taking precaution to avoid rupture that could lead to seeding, metastatic proliferation and anaphylactic shock. In cases when surgery is not possible, chemotherapy with albendazole or, alternatively, mebendazole combined with praziquantel is used. The close contact with infected dogs is a risk factor for humans. Prevention includes eliminating infection in definitive hosts—especially domestic dogs—by periodic deworming and preventing them from consuming raw entrails from butchered animals. Introduction of vaccines in sheep has been successful as it remarkably diminishes hydatid cysts, with regard to number and size. However, in spite of the different measures taken, the continuous report of cases in endemic countries shows that those measures are insufficient. Widespread vaccine administration to domestic animals acting as intermediary hosts shows promise in achieving a long-term disease prevention and control. In conclusion, current interventions need to be sustained and combined with effective vaccines.