The egg then hatches in the small intestine of the intermediate host and releases an oncosphere that penetrates the intestinal wall and moves through the circulatory system into different organs, in particular the liver and lungs. Once it has invaded these organs, the oncosphere develops into a cyst. The cyst then slowly enlarges, creating protoscolices (juvenile scolices), and daughter cysts within the cyst. The definitive host then becomes infected after ingesting the cyst-containing organs of the infected intermediate host. After ingestion, the protoscolices attach to the intestine. They then develop into adult worms and the cycle starts all over again. Eggs
Echinococcus eggs contain an embryo that is called an oncosphere or hexcanth. The name of this embryo stems from the fact that these embryos have six hooklets. The eggs are passed through the feces of the definitive host and it is the ingestion of these eggs that lead to infection in the intermediate host. Larval/hydatid cyst stage
From the embryo released from an egg develops a hydatid cyst, which grows to about 5–10 cm within the first year and is able to survive within organs for years. Cysts sometimes grow to be so large that by the end of several years or even decades, they can contain several liters of fluid. Once a cyst has reached a diameter of 1 cm, its wall differentiates into a thick outer, non-cellular membrane, which covers the thin germinal epithelium. From this epithelium, cells begin to grow within the cyst.
Alveolar echinococcosis
A number of strategies are geared towards prevention and control of alveolar echinococcosis—most of which are similar to those for cystic echinococcosis. For instance, health education programs, improved water sanitation, improved hygiene and de-worming of hosts (particularly red foxes) are all effective to prevent and control the spread of alveolar echinococcosis. Unlike cystic echinococcosis, however, where there is a vaccine against E. granulosus, there is currently no canidae or livestock vaccine against E. multilocularis. Polycystic echinococcosis
While a number of control and prevention strategies deal with cystic and alveolar echinococcosis, there are few methods to control and prevent polycystic echinococcosis. This is probably due to the fact that polycystic echinococcosis is restricted to Central and South America, and that the way that humans become accidental hosts of E. oligarthrus and E. vogeli is still not completely understood. Human vaccines
Currently there are no human vaccines against any form of echinococcosis. However, there are studies being conducted that are looking at possible vaccine candidates for an effective human vaccine against echinococcosis. Treatment
Cystic
A number of therapy options are presently available. Treatment with albendazole, whether combined or not with praziquantel, is useful for smaller, uncomplicated cysts (< 5 cm). Only 30% of cysts disappear with medical treatment alone. Noramlly, albendazole is preferred twice a day for 1–5 months. An alternative to albendazole is mebendazole for at least 3 to 6 months. Surgery is indicated for bigger liver cysts (> 10 cm), and cysts at risk of rupture and/or complicated cysts.