The effect of halofuginone, Wellcome 993 C, oxytetracycline, and diminazene diaceturate on Babesia equi-infected lymphoblastoid cell cultures.

The efficacy of halofuginone (DL-trans-7-bromo-6-chloro-3,3-(3-hydroxy-2-piperidyl) acetonyl-4-(3H) quinazolinone), Wellcome 993 C (2-hydroxy-3-cyclohexyl-1,4-naphthoquinone), and oxytetracycline, all of which have been shown to have a schizonticidal effect in the treatment of bovine theileriosis, and the babesicidal drug diminazene diaceturate, were tested against the schizont stages of Babesia equi in cell culture. The in vitro test system measured DNA synthesis in treated and untreated cell lines. Halofuginone (0.02 microgram/ml) and Wellcome 993 C (5 micrograms/ml) suppressed the incorporation of tritiated thymidine by more than 80%. Oxytetracycline was less effective, while diminazene diaceturate showed no notable effect. The insufficient schizonticidal activity may explain the failure of diminazene diaceturate to cure B. equi infections. Schizonticidal drugs either alone, or in combination with known babesicidal drugs, should be tested in the chemotherapy of B. equi infections.