A comparison of the effects of two dinitroanilines against Cryptosporidium parvum in vitro and in vivo in neonatal mice and rats

The effects of two dinitroanilines, oryzalin and trifluralin, were compared against Cryptosporidium parvum, in vitro using HCT-8 cells and in vivo using neonatal Swiss ARC mice and Wistar neonatal rats. In vitro, oryzalin and trifluralin exhibited IC50 values (concentration necessary to cause a 50% inhibition) of 750 and 800 nM, respectively. A viability assay showed that neither compound produced a cytotoxic effect on the host cells at concentrations as high as 1 μM. The in vivo component of this study consisted of inoculation of neonatal mice and neonatal rats with 105 viable oocysts of C. parvum per animal and the subsequent treatment of this infection with trifluralin and oryzalin administered via gastric intubation. At doses of 100 mg kg−1 body weight administered twice daily for 3 consecutive days, trifluralin had no statistically significant effect on the number of oocysts recovered from the gut of either rats or mice compared with controls, whereas at the same concentration, oryzalin caused 90 and 79% inhibition of oocysts recovered from mice and rats, respectively.