Man is intermediate host for:
Definitive host for Echinococcus is Dog
a. Humans play the role of intermediate hosts in the dog tapeworm life cycle as sheep.
b. Humans become infected by ingesting tapeworm eggs passed from an infected carnivore.
c. This occurs most frequently when individuals handle or contact infected dogs or other infected carnivores or inadvertently ingest food or drink contaminated with fecal material containing dog tapeworm eggs.
d. They hatch into embryos in the intestine, penetrate the intestinal lining, and are then picked up and carried by blood throughout the body to major filtering organs (mainly liver and/or lungs).
e. After the developing embryos localize in a specific organ or site, they transform and develop into larval echinococcal cysts in which numerous tiny tapeworm heads (called protoscolices) are produced via asexual reproduction
f. Approximately two thirds of patients experience liver echinococcosis.
g. The second most common organ involved is the lung.
h. In each anatomic site, cysts are surrounded by the periparasitic host tissue (pericyst), which encompasses the endocyst of larval origin.
i. Inside the laminated layer, or hyaline membrane, the cyst is covered by a multipotential germinal layer called the endocyst, giving rise to the production of brood capsules and protoscolices.
j. The central cavities of cysts of E granulosus are filled with clear fluid, numerous brood capsules, and protoscolices. In addition, daughter cysts of variable size are often detected.
k. Months or years may pass before an individual exhibits any signs or symptoms of infection with the cystic larval stages.
l. During the natural course of infection, the fate of E granulosus cysts is variable:-
m. Some cysts may grow to a certain size and then persist without noticeable change for many years.
n. Other cysts may rupture spontaneously. Spontaneous or traumatic cyst rupture and spillage of viable parasitic tissue during interventional procedures may result in secondary echinococcosis.
o. Collapse of the cyst and spontaneous cure of cystic echinococcosis is possible.
p. After a variable incubation period, infections may become symptomatic if cysts are growing and exerting pressure on adjacent tissue and inducing other pathologic findings.