**4. Transmission**

*Overview on Echinococcosis*

**2.** *E. granulosus* **eggs**

**Figure 1.**

E. granulosus *adult.*

The eggs are spherical in shape (**Figure 2**) and have a diameter of about 40–30 μm and are similar in appearance to the eggs of other tapeworms, containing a hexacanth or oncosphere embryo because the embryo has sixth-hooks lets. The eggs are surrounded by clear coatings [8] and the eggs contain a sticky layer that adheres to the fur of animals and other things, which helps them to spread, as well as insects such as flies, beetles, and birds that play the role of mechanical carrier of eggs, in case of optimal conditions, the eggs remain viable for weeks or months in pastures and gardens as well as they remain viable with the right humidity and moderate temperatures, and the eggs are found in water and wet sand for 3 weeks at 30°C and 225 days at 6°C and 32 days at 10–21°C, also the eggs remain for a short time when exposed to sunlight and dry conditions and kill eggs when exposed to 3.75% of sodium hypochlorite for 10 minutes as well as killed when frozen at −70°C

for 4 days or −80°C for 2 days or by heat larger from 60°C for 3 minutes [9].

**48**

**Figure 2.**

E. granulosus *egg in feces [7].*

Transmission to humans is caused by fecal-oral route while eating food and water contaminated with parasite eggs, and these eggs are thrown out with feces of the definitive hosts such as dogs or through contamination of hands with eggs found in contaminated soil or sand or in the hair of infected dogs. The definitive hosts become infected with the adult worm when they feed on the hydatid cysts, which are found in the organs of the intermediate host, such as infected sheep [9, 11].
