title: Infection of immunosuppressed C57BL/6N adult mice with a single oocyst of Cryptosporidium parvum.
abstract: The present study was designed to determine the minimum number of Cryptosporidium parvum oocysts capable of producing patent infections in immunosuppressed C57BL/6N adult mice. Sixty-four female mice were divided into 6 groups of 8 mice each, except group 1 that contained 24 mice. Mice in groups 1-3 were immunosuppressed with dexamethasone and inoculated with 1, 5, and 10 oocysts per mouse, respectively. The accuracy of the inoculum size was microscopically confirmed. Mice in groups 4-6 served as controls: they received either only oocyst inoculation (group 4), or immunosuppression (group 5), or no treatments (group 6). Fecal oocyst shedding was monitored daily for each mouse using an indirect immunofluorescent assay. Parasite colonization in the terminal ileum of each mouse was evaluated histologically. Four of 24 mice in group 1 developed patent infections, with a prepatent period of approximately 6 days. All mice in groups 2 and 3 developed patent infections, with prepatent periods ranging from 4 to 7 days. Mice in groups 4-6 remained uninfected. Parasite colonization was observed in the terminal ilea of all mice in groups 1-3 that shed fecal oocysts. The present study experimentally demonstrates that a single viable oocyst can induce patent C. parvum infections in immunosuppressed C57BL/6N adult mice and indicates that this mouse model could be used for the parasite genotype or isolate cloning.
authors.affiliation: Department of Animal, Dairy, and Veterinary Sciences, Utah State University, Logan 84322-5600, USA.
authors.forename: S
authors.initials: S
authors.lastname: Yang
authors.forename: S K
authors.initials: SK
authors.lastname: Benson
authors.forename: C
authors.initials: C
authors.lastname: Du
authors.forename: M C
authors.initials: MC
authors.lastname: Healey
mesh_terms: D000818:Animals; D003457:Cryptosporidiosis / Q000276:immunology* / Q000469:parasitology; D016785:Cryptosporidium parvum / Q000276:immunology / Q000502:physiology*; D004195:Disease Models, Animal; D004198:Disease Susceptibility; D005243:Feces / Q000469:parasitology; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D007082:Ileum / Q000469:parasitology; D007121:Immunocompetence; D007165:Immunosuppression Therapy; D051379:Mice; D008810:Mice, Inbred C57BL; D009929:Organ Size; D010865:Pilot Projects; D011897:Random Allocation; D013154:Spleen / Q000473:pathology