Experimental treatment of Neospora caninum-infected mice with the arylimidamide DB750 and the thiazolide nitazoxanide

[Display omitted] ► The in vivo efficacies of DB750 and nitazoxanide against murine neosporosis were investigated. ► Both drugs were not effective when applied orally. ► Nitazoxanide was highly toxic when applied intraperitoneally. ► DB750 was effective when applied intraperitoneally, leading to reduced cerebral parasite burden. The cationic arylimidamide DB750 and the thiazolide nitazoxanide had been shown earlier to be effective against Neospora caninum tachyzoites in vitro with an IC50 of 160nM and 4.23μM, respectively. In this study, we have investigated the effects of DB750 and nitazoxanide treatments of experimentally infected Balb/c mice, by applying the drugs either through the oral or the intraperitoneal route. In experiment 1, administration of DB750 (2mg/kg/day) and nitazoxanide (150mg/kg/day) started already 3days prior to experimental infection of mice with 2×106 tachyzoites. Following infection, the drugs were further administrated daily for a period of 2weeks, either orally or intraperitoneally. Intraperitoneal injection of DB750 was well tolerated by the mice, but treatment with nitazoxanide resulted in death of all mice within 3days. Upon intraperitoneal application of DB750, the cerebral parasite load was significantly reduced compared to all other groups, while oral application of DB750 and nitazoxanide were not as effective, and resulted in significant weight loss. In experiment 2, mice were infected with 2×106 tachyzoites and at 2weeks post-infection, DB750 (2mg/kg/day) was applied by intraperitoneal injections for 14days. In the DB750-treated group, only 2 out of 12 mice succumbed to infection, compared to 7 out of 12 mice in the placebo-group. DB750 treatment also resulted in significantly reduced cerebral parasite burden, and reduced numbers of viable tachyzoites. Our data suggest that DB750 exerted its activity also after crossing the blood–brain barrier, and that this class of compounds could be promising for the control of N. caninum-associated disease.