Farid, AlyaaAiad, SilviaSafwat, Gehan2023-11-142023-11-142023-11https://doi.org/10.1186/s13568-023-01632-whttp://repository.msa.edu.eg/xmlui/handle/123456789/5765Cryptosporidiosis is an intestinal infection that is triggered by the protozoan parasite Cryptosporidium spp. Crypto- sporidium oocysts can spread from one host to another either through direct contact with infected hosts’ faeces or through indirect means (consumption of contaminated water or food). Signifcant numbers of oocysts are pro- duced as a result of the rapid growth of the parasite within the infected hosts. For proper care of cryptosporidiosis, a laboratory diagnosis is necessary. Therefore, this study aimed to produce anti-Cryptosporidium parvum (C. parvum) oocyst immunoglobulin (Ig)G polyclonal antibodies (pAbs). The produced pAbs were used in the detection of C. parvum oocysts antigens in stool and serum samples of infected calves. Moreover, pAbs were tested in protection of balb-c male mice from cryptosporidiosis infection. C. parvum oocysts were used in the preparation of antigens to be used in the immunization of New Zealand white rabbits. pAb was purifed by ammonium sulphate precipitation method, caprylic acid purifcation method and diethylaminoethyl (DEAE) anion exchange chromatographic method. Sandwich enzyme-linked immunosorbent assay (ELISA) (using prepared pAb) scored higher sensitivity (85% and 95% for serum and stool samples) than that (80%) of microscopic examination of stool samples. Moreover, pAb signif- cantly reduced the oocysts shedding, decreased infammatory cytokines and enhanced the loss in the body weight of protected animals. The prepared pAb succeeded in the diagnosis of cryptosporidiosis in calves with high sensitiv- ity either in the serum or stool samples. Our results indicated the usefulness of using the prepared pAb in protection against cryptosporidiosis.enCryptosporidium parvum, Polyclonal antibodies, Oocysts, Immunoglobulin A, Interferon-γ, Interleukin-4Articlehttps://doi.org/10.1186/s13568-023-01632-w