Activity of Azithromycin against Cryptosporidia in Immunosuppressed Rats

Dexamethasone-immunosuppressed rats infectedwith Cryptosporidium parvum wereused to assess the macrolidesazithromycin and spiramycinfor anticryptosporidialactivity.Azithromy-cinconsistently prevented ilealinfection, whilespiramycin wasineffective. The anticryptosporidial activityofazithromycin wasdose-related, 200mg/kg/daybeingthe minimumdosethat prevented infection. Therapeutically, azithromycin eliminated an establishedovert infection of the small intestine in immunosuppressedrats, but the infectionrecurred after azithromycin treatment was stopped. Thesefindings suggestthat azithromycin isa potentiallyusefulanticryptosporidial agent and that long-termcontinuousadministration maybe necessaryto treat cryptosporidiosis in the immunocompromised host. Cryptosporidiosis is an intestinal and pulmonary disease caused by the protozoan Cryptosporidium. Its most common manifestation in mammalian species is enteric disease, which in immunocompetent hosts is self-limiting but can be life-threatening in hosts with suppressed immune function [I, 2]. Cryptosporidiosis is the reported cause of diarrhea i