The tiny, iodine- and chlorine-resistant protozoan oocysts of Cryptosp
oridium parvum, long recognized by veterinarians, have become increasi
ngly noted as a cause of watery diarrhea in developed and developing c
ountries throughout the world For immunocompromised patients, particul
arly those with AIDS, this diarrhea can be severe and life-threatening
. Clovis Martins and Richard Guerrant here discuss the increasing reco
gnition of this important pathogen in immunocompetent Patients as well
, and outline new challenges to improved water treatment, immunologic
and antiparasite chemotherapy.