Cryptosporidium parvum is a parasitic protozoan that functions as important causative agent of diarrhea in human and animals. The host's immune response to surface anti-gens of C. parvum has been previously demonstrated. In this respect, the role of humoral immunity in the development of host protective immunity against this protozoon has been well demonstrated. Methods: The effect of specific chicken egg yolk antibody (IgY) against recombinant C. parvum P23 was examined. IgY sample was

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... from eggs of chickens immunized with recombi-nant C. parvum protein p23 and analyzed with C. parvum lysate and recombinant P23. Results: The anti P23 specific IgY was recognized a protein band with approximately 23 kDa in lysates prepared from the C. parvum oocysts. Also dot blot analysis of recombinant P23 showed that it could be recognized by the anti P23 specific IgY up to 1/1000 dilution of antibody. But the best antibody dilution for immunological studies was determined as 1:200. Conclusion: Since P23 is an immunodominant surface glycoprotein expressed in the early phase of infection, specific IgY against recombinant p23 could be recommended as a favorable candidate for passive immunization against C. parvum infection in human and animals.