Cryptosporidiosis in patients with HIV/AIDS.

Cryptosporidium spp. are intestinal protozoan parasites of the phylum Apicomplexa, which cause diarrheal disease in humans worldwide (reviewed in [1–6]). In immunocompetent individuals, infection with this parasite may be asymptomatic or cause a self-limiting diarrheal illness. However, in immunocompromised patients such as those with HIV/AIDS Cryptosporidium spp. may cause severe, chronic and possibly fatal diarrhea and wasting. Although Cryptosporidium was discovered in 1907, it was not till 1976 that the first human cases of cryptosporidiosis were reported and not till the onset of the AIDS epidemic in the early 1980s that this parasite became widely recognized as a human pathogen (reviewed in [4,7,8]). Indeed, cryptosporidiosis was one of the original AIDSdefining illnesses and as such was associated with an increased risk of death compared to other AIDS-defining illnesses [9]. The use of highly active antiretroviral therapy (HAART) in the past 2 decades has reduced the prevalence of this disease in AIDS patients in industrialized countries [10–12]. However, the emergence of drug-resistant HIV variants and failure or discontinuation of HAART has been associated with re-emergence of Cryptosporidium spp. infection in these patients [13,14]. Even patients with advanced AIDS who are on HAART have recently been reported to have Cryptosporidium spp. infection [15]. Although antiretroviral treatment (ART) has recently become available in some developing