EN
This study was conducted in population of wild small mammals in northern Poland, District of Mazury Lake, Urwitałt, near Mikołajki. Samples were collected four times, from autumn 1989 until spring 1991. Twenty percent (66 of 330) of the examined mammals were positive for Cryptosporidium, i.e., 55 of 275 Clethrionomys glareolus, 6 of 39 Apodemus flavicollis, 5 of 16 Sorex araneus were naturally infected with Cryptosporidium. There was no infection of Cryptosporidium assessed in A. agrarius and S. minutus. Our histological data clearly indicate that the population of C. glareolus was infected with C. parvum. This population of rodents appears to have maintained an infection throughout two years. These findings indicate that C. glareolus and possibly other rodents have potential to act as a reservoir for C. parvum, a pathogen of man and ruminants.