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 dexa methasone in drinking water to sustain infections with Cryptosporidium parvum was investigated. An ethanol-soluble formulation of dexamethas one (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 mug/ml. DEX was also administered to mic e by intraperitoneal injection at 125 mug/mouse/day. All mice were ino culated intragastrically with 10(6) C parvum oocysts/mouse on day 14 p ostimmunosuppression. Mice immunosuppressed through drinking water exh ibited increased signs of toxicity compared with mice intraperitoneall y injected with DEX. Moreover, mice receiving DEX in drinking water we re less active and died significantly sooner (P < 0.05) than mice rece iving DEXp at the same dosages. Immunosuppressed mice began shedding o ocysts 3 days postinfection and continued to shed until they either di ed or were killed. Beginning on day 12 postinfection, mice receiving D EX or DEXp in drinking water shed significantly more oocysts (P < 0.05 ) than mice immunosuppressed via intraperitoneal injection. Immunosupp ressing mice through drinking water was comparatively simple, less tra umatic than injection, and efficient with regard to time and labor.