In the present study, protoscolices and hydatid fluid were prepared from livers or lungs of sheep with hydatid cyst in sterile conditions. The protein concentration of samples was then measured by Bradford method. 12 lambs 4 - 6 months of age of mixed sex were randomly allocated to 3 groups of 4 lambs. Each lamb in groups 1 and 2 was immunized subcutaneously in the neck with a 2 - ml dose of vaccine (1 mg of protoscolex and hydatid fluid proteins dissolved in 1 ml of PBS) and emulsified with an equal volume of Freund s complete adjuvant (FCA) respectively. Control lambs were immunized with adjuvant in PBS. Lambs were boosted at day 28 with the same preparation except that FCA was replaced by Freund s incomplete adjuvant (FIA). Three weeks after the second immunization, each lamb received a challenge infection with 2000 protoscolices intrapritoneally and 10 adult E. granulosus. All lambs were euthanized after 7 months and examined for hydatid cysts. Results showed that, the number of cysts in immunized lambs with protoscolices were lower than in control group and also the number of cysts in immunized lambs with hydatid fluid antigen was significant (p<0.05). This result indicated that the protective immunity in lambs with protoscolices and hydatid fluid was 54.5% and 75.75% respectively.

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