The present study was concerned with prevalence, ultrasonographical, immunological and molecular biological differentiation between Echinococcus granulosus isolates (hydatid cysts) among different farm animals including camel, sheep & goat, equine and pig in Egypt. Determination of the resvoirs of the parasites by these studies would help the focusing of control effort. Moreover, determination of the specific antigens of Echinococcus granulosus will have great important in proper diagnosis as well as vaccine candidate production. The occurrence of hydatidosis in 3175 slaughtered animals was 4.4 %. Cystic Echinococcosis Prevalence of camel and equine, which were 11.5% and 11.1% respectively, were higher than those observed in the other animal species. The lowest infection prevalence rate was in buffalo and sheep then in pigs with percentage of 0.5 %, 0.57 % and 2.95 % respectively. The highest fertility of hydatid cyst was in equine with percentage of 75 % while, the lowest fertility was in pig with percentage of 6.25 %. All collected hydatid cysts from buffalo and sheep was sterile. Hydatid cysts in camel were collected from liver and lung with percentage of 9.02 % and 90.9 % and the fertility was 30.7 % and 60 % respectively. In buffalo and sheep, the hydatid cysts were collected from the liver. In equine, Hydatid cysts were collected from liver and lung with percentage of 92.5 % and 7.4 % and the fertility was 78 % and 37.5 % respectively. In pig, Hydatid cysts were collected from liver, lung and other organs as spleen and kidney with percentage of 6.25% , 85.4% and 8.3 with fertility of 33.3 %, 37.5 % and 0 %, respectively. The infection rate increased with the age of the host in all studied animal species. No infection less than 2 years old and most of infection occurred more than five years old specially in camel, buffalo and equine. Also, The prevalence and intensity of infection was not significantly different between male and female animals. By flotation technique, the hydatid cysts in camel and donkey that present in the lung and liver were of type I (cysts were univesicular viable cysts, with a visible cyst wall), type IV (cysts presented a solid calcified mass, indicative of degenerating membranes with heterogeneous hypoechoic or hyperechoic contents), type V (cysts were completely or partially calcified cysts with a thick calcified wall ) and Type VI (were unilocular cystic lesions with uniform anechoic content ,cyst wall not visible). Among 54 examined donkey, a total of 5 animals were found to have hepatic hydatid cysts (9.3 %) while at post mortem the percentage of hydatidosis in examined animals were (11.1 %). These cysts included type I, type IV and Type VI of cysts diagnosed by ultrasound with diameter between 1x0.5 to 3x2cm. The specificity percentage, sensitivity percentage and accuracy percentage of ultrasonography examination in the donkeys was 100 %, 83.3 % and 98.1 %, respectively. Among twenty examined goat, one animal was found to had hepatic hydatid cysts (5%) that had 7cysts of type I and type III diagnosed by ultrasound at the level of middle 11th intercostals space on the right side. All cysts were of type I except one cyst of type III. in type (III) the cysts were multivesicular and multisepted cysts, in which daughter cysts may produce a ‘‘rosette-like’’ or ‘‘honeycomb-like’’ structure. The diameter was between 1x1 to 3x3 cm. After the try of aspiration by guiding of the sonar revealed the presence of clear hydatid fluid which was fertile by presence of protoscoleces. But in two cases, the try of aspiration by guiding of the sonar was failed from a single unilocular thin walled cyst in the liver parenchyma which is indistinguishable from a unilocular hydatid cyst caused by E. granulosus on ultrasound examination. Those indicated as T. hydatigena cysticerci present within the liver parenchyma. Taenia hvdatigena cysticerci occur in the mesentery and liver of domestic livestock. This misdiagnosed with hydatid cyst. The SDS-PAGE technique demonstrated that 12 KDa was a shared protein band between crude antigen of hydatid fluid obtained from the camel and protoscoleces obtained from the equine origin while 27 KDa was a shared protein band between crude antigen of protoscoleces obtained from the camel and protoscoleces obtained from the equine origin and 31 KDa was a shared protein band between crude antigen of protoscoleces obtained from the camel and hydatid fluid obtained from the equine origin. 35 KDa was a shared common protein band between all used antigens. ELISA was carried out as a screening test to select the antigen of choice. The test was carried out on crude antigens obtained from hydatid fluid and protoscoleces of camel and equine origin against their antisera. In hydatid fluid antigen of camel origin that used for diagnosis of camel hydatidosis by ELISA gave sensitivity percentage of 87.5 %, specificity percentage of 100 % and accuracy percentage of 93.3 %. However, hydatid fluid antigen of camel origin that used for diagnosis of equine hydatidosis by ELISA gave sensitivity percentage of 100 %, specificity percentage of 66.6% and accuracy percentage of 86.6 %. That means, the hydatid fluid antigen of camel origin was the antigen of choice for diagnosis of camel and equine hydatidosis. The technique of random amplified polymorphic DNA (RAPD) has been used to detect DNA polymorphisms among E. granulosus isolates of camel, sheep, donkey and pigs. Eight arbitrary oligonucleotides (10-mer) were used as primers to amplify total genomic DNAs and significant genetic heterogeneity was detected among these isolates. Five of the Eight primers under assay, P1 followed by P2, P4, OPH-12 and P3 proved useful as genetic markers of strain variation, while P5,OPH-03 and OPH-18 allowed distinction at the genus level. P1, P2, P4 were the most effective primers giving sharp distinct banding pattern and the least values of similarity coefficient. Some variations within E. granulosus isolates from the same type of the host were observed in form of differences in band intensities in all the primers used. The study implies that the donkeys are important host in transmission of hydatidosis between animals and human.