An in vitro model of infection of chicken embryos by Cryptosporidium baileyi

• In vitro model for Cryptosporidium baileyi was developed in chicken embryo.
• The life cycle of C. baileyi was described by light and electron microscopy.
• Time point and reproduction number of C. baileyi oocysts was clarified in allantoic fluid of chicken embryos.

Cryptosporidiosis is one of the most prevalent parasitic infections in domesticated, caged and wild birds. Cryptosporidium baileyi is the most common species reported in a wide range of avian hosts. Although this parasite is well investigated, there is no adequate in vitro model for its endogenous development, and therefore, knowledge of each life cycle phase is scarce. In the present study, an in vitro model for C. baileyi in chicken embryos was developed and the complete life cycle investigated by light and electron microscopy, including both the sexual and asexual reproduction stages. The complete life cycle of C. baileyi was observed during 1–96 h post inoculation (PI), and the average reproduction number of C. baileyi oocysts in allantoic fluid of each chicken embryo was greatest at 168 h PI. These results suggest that chicken embryos could adequately represent the natural host cells and support the development of all the endogenous life cycle stages of C. baileyi, and also provide a new and effective in vitro cultivation system for further studies on antigens, virulence, infectivity, metabolites, and sensitivity of drugs against parasites.

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