The immunosuppressive effects of dexamethasone administered in drinking water to C57BL/6N mice infected with Cryptosporidium parvum.

The feasibility of immunosuppressing adult C57BL/6N mice by using dexamethasone in drinking water to sustain infections with Cryptosporidium parvum was investigated. An ethanol-soluble formulation of dexamethasone (DEX) was compared with a water-soluble (phosphated) formulation (DEXp). DEX or DEXp was provided for mice ad libitum in drinking water at dosages of 10, 33, and 100 micrograms/ml. DEX was also administered to mice by intraperitoneal injection at 125 micrograms/mouse/day. All mice were inoculated intragastrically with 10(6) C. parvum oocysts/mouse on day 14 postimmunosuppression. Mice immunosuppressed through drinking water exhibited increased signs of toxicity compared with mice intraperitoneally injected with DEX. Moreover, mice receiving DEX in drinking water were less active and died significantly sooner (P < 0.05) than mice receiving DEXp at the same dosages. Immunosuppressed mice began shedding oocysts 3 days postinfection and continued to shed until they either died or were killed. Beginning on day 12 postinfection, mice receiving DEX or DEXp in drinking water shed significantly more oocysts (P < 0.05) than mice immunosuppressed via intraperitoneal injection. Immunosuppressing mice through drinking water was comparatively simple, less traumatic than injection, and efficient with regard to time and labor.