Echinococcosis is a parasitic disease that occurs in two main forms in humans: cystic echinococcosis (also known as hydatidosis) and alveolar echinococcosis, caused by the tapeworms Echinococcus granulosus and E. multilocularis, respectively.
Dogs, foxes and other carnivores harbour the adult worms in their intestine and pass the parasite eggs in their faeces. If the eggs are ingested by humans, they develop into larvae in several organs, more frequently the liver and lungs.
Both cystic and alveolar echinococcosis are characterized by asymptomatic incubation periods that can last many years until the parasites grow to an extent that triggers clinical signs.
Both diseases can cause serious morbidity and death.
A number of herbivorous and omnivorous animals act as intermediate hosts of Echinococcus, which means they get infected by ingesting the parasite eggs in the contaminated ground and develop parasitic larval stages in their viscera. Carnivores are definitive hosts for the parasite, and are infected through the consumption of viscera of intermediate hosts that harbour the parasite or through scavenging infected carcases. Humans are accidental intermediate hosts and are not able to transmit the disease.
Cystic echinococcosis is globally distributed, with highly endemic areas mostly found in the eastern part of the Mediterranean region, northern Africa, southern and eastern Europe, at the southern tip of South America, in Central Asia, Siberia and western China. Conversely, alveolar echinococcosis is confined to the northern hemisphere, in particular to regions of western and northern China, the Russian Federation, most countries of continental Europe and northern countries of North America.