BILIARY-TRACT CRYPTOSPORIDIOSIS IN AN IMMUNOSUPPRESSED RAT MODEL

Rats immunosuppressed by hydrocortisone acetate and a low protein diet were challenged with Cryptosporidium parvum oocysts and studied on da ys 10, 35 and 70 post-infection. The biliary tract was found to be a m ajor site of parasite infection. C. parvum was visible in the biliary papillary area in association with a proliferation of highly convolute d tubular glands. The papillary lumen was narrowed, and an upstream di latation with bacterial proliferation was seen. The liver was initiall y free of lesions, and subsequently exhibited late lesions of cholesta sis. Parasites were not found in the pancreatic duct, although pancrea titis was frequently observed. Oocysts were consistently present in th e distal portion of the ileum. Both challenged and unchallenged immuno suppressed rats, exhibited widespread focal hepatic infarcts and pyelo nephritis. Other organs appeared free of lesions. In addition to the i ntestine, data identified the biliary tract as a major site of C. parv um infection and as a potential protected reservoir which may sustain a chronic infection.