Long-Term Consequences ofCryptosporidiumInfections in Immunocompetent and Immunodeficient Individuals

Abstract

Protozoans of the genus Cryptosporidium are small coccidian parasites that infect the mucosal epithelium of a variety of vertebrate hosts, including humans. The life cycle of most Cryptosporidium species is completed within the gastrointestinal tract (primarily the small intestine) of the host, with developmental stages being associated with the luminal surface of the mucosal epithelial cells. Cryptosporidiosis in the immunocompetent person is a self-limiting, acute gastroenteritis with a variety of presenting symptoms. Symptoms of cryptosporidiosis are generally similar but often develop insidiously in immunocompromised patients. The fact that both immunocompetent and immunocompromised persons develop a diarrheal illness suggests that symptoms are not totally dependent on an intact immune response. A recent paper analyzed the effect of the two major human pathogens, C. hominis and C. parvum, on oocyst shedding, symptoms, and long-term effects on growth. Primary immunodeficiencies (PIDs) are rare inherited disorders of the innate, cellular, and/or humoral immune system. In a study of the association between X-linked hyper-immunoglobulin M (IgM) syndrome (XHIM) and tumors of the pancreas, liver, and biliary tree, 14 of the 20 boys (70%) were found to be infected with Cryptosporidium species. The treatment of cryptosporidiosis in immunocompromised patients can, in principle, be based on (i) the use of antimicrobial agents, (ii) passive immunotherapy, and (iii) immune reconstitution.