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

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].

**49**

Echinococcus granulosus

cyst [10, 11].

[9, 11].

**4. Transmission**

**5. Strains of** *E. granulosus*

strain in pigs [12].

**6. Parasite classification**

Kingdom: Animalia Phylum: Platyhelminthes Superclass: Eucestoda Class: Cestoda Subclass: Cestoda

Order: Cyclophyllidea (Ben; Braun, 1900)

Family: Taeniidae (Ludwig, 1886)

*DOI: http://dx.doi.org/10.5772/intechopen.90708*

When intermediate hosts (farm animals) or humans (accidental host) ingest the eggs, the embryo (oncospheres) hatches and becomes active, transmitted by the bloodstream to the liver or any other organ. As soon as the hexacanth embryo reaches its definitive position, it develops into unilocular hydatid cyst that enlarges and produces daughter cysts or protoscoleces inside the inner layer of the hydatid

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

Species of *E. granulosus* is divided into several strains such as G1–G10 and these strains have a high degree of adaptation to their hosts, as these strains are named according to the names of their intermediate hosts that play an important role in the continuity of the life cycle of these strains. These strains vary in shape, rate of development, pathogenicity, and geographical extent of their presence: G1 is found in sheep, G2 in Tasmania sheep, and G3 in buffalo. These strains all fall within the *E. granulosus* species, and G4 strain in equine is therefore called *E. equinus*; G5 in cows is called *E. ortleppi*; G6 in camels; G7 in pigs; G9, which is characterized weak, has been isolated from cystic disease in human cases in Poland; G7, G8, and G9 may fall into *E. canadensis*, and some researchers consider the G9 strain a type of G7

The classification of Echinococcus genus has been controversial for a long time, and 16 species and 13 subspecies of this genus have been described, based on the difference in the structural and phenotypic properties of the parasite and the characteristics of the host and its type, but only 4 of them are taxonomically adopted: *E. granulosus*, *E. multilocularis*, *E. oligarthrus*, and *E. vogeli* [13]. According to [14],

the classification system of granulocytic parasitic parasite is as follows:

**3. Larval stage (hydatid cyst)**

**Figure 2.** E. granulosus *egg in feces [7].*
