Equine piroplasmosis is a tick-transmitted disease that is considered one of the most serious infectious diseases affecting equines. Searching for novel antipiroplasm drugs remains indispensable due to the emergence and spreading of resistant piroplasm parasites against the limited currently used drugs, diminazene aceturate and imidocarb dipropionate. Therefore, novel drugs with specified targets need to be identified and exploited. The inhibitory effects of Medicines for Malaria Venture (MMV) Malaria Box compounds with potent in vitro anti-equine piroplasmosis activity were evaluated against the growth of B. microti in mice in this study. Using a nested PCR assay targeting the B. microti ss-rRNA gene, we investigated the far-reaching impacts of effective combinations to inhibit parasite recrudescence. Using real-time PCR, this study revealed potential targets for the found potent compounds. When used as monotherapy, screening the Malaria Box against the in vivo growth of the B. microti parasite resulted in the discovery of new, potent antipiroplasm medicines, such as MMV020275 and MMV020490. In MMV020275-treated Theileria equi in vitro culture, a statistically significant difference (P<0.05) in the cGMP-dependent protein kinase (PKG) mRNA level was identified as a down-regulation in contrast to non-treated cultures. In conclusion, new potent antipiroplasm drugs, including MMV020275 and MMV020490 are identified. MMV020275 significantly down-regulate the mRNA levels of the PKG gene. Clofazimine enhanced the inhibitory efficacy of MMV compounds which is suggested to use in treatment of animal or human babesiosis in the future.
Keywords: Babesia microti; Combination therapy; Drug discovery; MMV020275; MMV020490; Malaria box; Theileria equi.
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