Cryptosporidiosis in man: parasite life cycle and fine structural pathology.

The Cryptosporidium here described is a very small (3-4 micron) opportunistic pathogenic coccidian parasite. Through seven known human enteric infections it is now associated with diarrhoea in immunosuppressed or immunodeficient individuals. Neither the full pathogenic potential nor the complete life cycle of this parasite are known, and there is no adequate chemotherapeutic agent with which to eradicate it. What is known of its intracellular intestinal forms and the fine structural changes occurring in parasitised epithelial cells has been described. A viral complication of the infection is discussed and mention is made of relevant cryptosporidial infections of domestic and other animals.