Despite the evaluation of over 100 antimicrobial drugs, the diarrheal
disease cryptosporidiosis has remained refractory to treatment. We rep
ort the evaluation of five dinitroaniline herbicides including triflur
alin, profluralin, nitralin, pendimethalin, and fluchloralin for antic
ryptosporidial activity in an in vitro cultivation model of Cryptospor
idium parvum. All five compounds exhibited significant anticryptospori
dial activities with no corresponding evidence of toxicity. The most a
ctive compound was pendimethalin with an IC50 of 0.19 mu M while nitra
lin was the least active with an IC50 of 4.5 mu M. These compounds sho
uld be evaluated further in an animal model of cryptosporidiosis.