PATENT GUT INFECTIONS IN IMMUNOSUPPRESSED ADULT C57BL 6N MICE FOLLOWING INTRAPERITONEAL INJECTION OF CRYPTOSPORIDIUM-PARVUM OOCYSTS/

Two experiments were conducted to determine if intraperitoneal (i.p.) and/or subcutaneous (s.c.) injection of Cryptosporidium parvum oocysts could produce patent gut infections in dexamethasone (DEX) or dexamet hasone phosphate (DEXp)-immunosuppressed adult female C57BL/6N mice. T he results from experiment 1 were suggestive but did not unequivocally demonstrate that i.p. injection of oocysts could produce patent gut i nfections in these mice. In experiment 2, all mice were individually c aged, immunosuppressed with DEXp (groups 1 and 2) or DEX (groups 3 and 4), and administered C. parvum oocysts either by orogastric intubatio n (groups 1 and 3), i.p. (group 2), or s.c. (group 4). All but 1 mouse in groups 1 and 3 began shedding oocysts in their feces on day 3 post infection (PI). Mice in these 2 groups continued to shed oocysts until they were killed on day 17 PI. Mice administered oocysts s.c. did not shed oocysts. In group 2, 1 mouse died, 1 failed to shed oocysts, and 1 began shedding oocysts on day 3 PI. The remaining 5 mice started sh edding oocysts on either days 8, 10, or 14 PI and continued to shed oo cysts until they were killed. We conclude that immunosuppressed adult CS7BL/6N mice administered oocysts i.p. can develop patent gut infecti ons with C. parvum.