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 dexamethasone phosphate (DEXp)-immunosuppressed adult female C57BL/6N mice. The results from experiment 1 were suggestive but did not unequivocally demonstrate that i.p. injection of oocysts could produce patent gut infections in these mice. In experiment 2, all mice were individually caged, immunosuppressed with DEXp (groups 1 and 2) or DEX (groups 3 and 4), and administered C. parvum oocysts either by orogastric intubation (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 shedding oocysts on either days 8, 10, or 14 PI and continued to shed oocysts until they were killed. We conclude that immunosuppressed adult C57BL/6N mice administered oocysts i.p. can develop patent gut infections with C. parvum.