Cryptosporidiosis emergence triggered the screening of many compounds for potential
anti-cryptosporidial activity in which the majority were ineffective. The outbreak
of cryptosporidiosis which occurred in Milwaukee in 1993 was not only the first significant
emergence of Cryptosporidium spp. as a major human pathogen but also a huge waterborne
outbreak thickening thousands of people from a major city in North America. Since
then, outbreaks of cryptosporidiosis are regularly occurring throughout the world.
New drugs against this parasite became consequently urgently needed. Among the most
commonly used treatments against cryptosporidiosis are paromomycin, and azithromycin,
which are partially effective. Nitazoxanide (NTZ)'s effectiveness was demonstrated
in vitro, and in vivo using several animal models and finally in clinical trials.
It significantly shortened the duration of diarrhea and decreased mortality in adults
and in malnourished children. NTZ is not effective without an appropriate immune response.
In AIDS patients, combination therapy restoring immunity along with antimicrobial
treatment of Cryptosporidium infection is necessary. Recent investigations focused
on the potential of molecular-based immunotherapy against this parasite. Others tested
the effects of probiotic bacteria, but were unable to demonstrate eradication of C.
parvum. New synthetic isoflavone derivatives demonstrated excellent activity against
C. parvum in vitro and in a gerbil model of infection. Newly synthesized nitro- or
non nitro- thiazolide compounds, derived from NTZ, have been recently shown to be
at least as effective as NTZ against C. parvum in vitro development and are promising
new therapeutic agents.