Contents lists available at ScienceDirect Ticks and Tick-borne Diseases journal homepage: www.elsevier.com/locate/ttbdis The effects of nitidine chloride and camptothecin on the growth of Babesia and Theileria parasites Dickson Stuart Tayebwa a,b,c , Bumduuren Tuvshintulga a , Azirwan Guswanto a , Arifin Budiman Nugraha a , Gaber El-Saber Batiha a,d , Sambuu Gantuya a , Mohamed Abdo Rizk a,e , Patrick Vudriko a,c , Thillaiampalam Sivakumar a , Naoaki Yokoyama a , Ikuo Igarashi a, ⁎ a National Research Center for Protozoan Diseases, Obihiro University of Agriculture Veterinary Medicine, Nishi 2 Sen-11, Inada-cho, Obihiro, Hokkaido 080-8555, Japan b Central Diagnostic Laboratory, College of Veterinary Medicine, Animal Resources and Biosecurity, Makerere University, 7062, Kampala, Uganda c Research Center for Tick and Tick-borne Diseases Control, College of Veterinary Medicine, Animal Resources and Biosecurity, Makerere University, 7062, Kampala, Uganda d Department of Pharmacology and Therapeutics, Faculty of Veterinary Medicine, Damanhour University, 22511, Albeheira, Egypt e Department of Internal Medicine and Infectious Diseases, Faculty of Veterinary Medicine, Mansoura University, 35516, Egypt ARTICLE INFO Keywords: Bovine piroplasmosis Camptothecin Equine piroplasmosis Nitidine chloride Topoisomerase inhibitors ABSTRACT The treatment of bovine and equine piroplasmosis is limited to diminazene aceturate (DA) and imidocarb di- propionate. To address this challenge, we need to explore novel drug compounds and targets. Topoisomerases are potential drug targets because they play a vital role in solving topological errors of DNA strands during replication. This study documented the effectiveness of topoisomerase inhibitors, nitidine chloride (NC) and camptothecin (Cpt), on the growth of Babesia and Theileria parasites. The half maximal inhibitory concentrations (IC 50 s) against B. bovis, B. bigemina, B. caballi, and T. equi were 1.01 ± 0.2, 5.34 ± 1.0, 0.11 ± 0.03, and 2.05 ± 0.4 μM for NC and 11.67 ± 1.6, 4.00 ± 1.0, 2.07 ± 0.6, and 0.33 ± 0.02 μM for Cpt, respectively. The viability experiment revealed that 4, 10, and 4 μM treatments of NC or 48, 8, and 8 μM treatments of Cpt were sufficient to stop the in vitro regrowth of B. bovis, B. bigemina, and B. caballi, respectively. However, T. equi regrew in all of the concentrations used. Moreover, increasing the concentration of NC and Cpt to 16 μM and 1.2 μM (8 × IC 50 ) did not eliminate T. equi. The micrographs of B. bigemina and B. caballi taken at 24 h and 72 h showed deformed merozoites and remnants of parasites within the red blood cell (RBC), respectively. The treatments of 25 mg/kg DA and 20 mg/kg NC administered intraperitoneally and 20 mg/kg NC given orally showed 93.7, 90.7, and 83.6% inhibition against Babesia microti (B. microti), respectively, compared to the untreated group on day 8. In summary, NC and Cpt were effective against Babesia and Theileria parasites in vitro. Moreover, 20 mg/kg NC administered intraperitoneally was as effective as 25 mg/kg DA against B. microti in mice and showed no toxic symptoms in mice. The results indicate that NC may, after further evaluations, prove to be an alternative drug against bovine and equine piroplasmoses. 1. Introduction Species of the genus Babesia and Theileria cause bovine and equine piroplasmosis, which are associated with economic losses to the cattle and equine industries worldwide (Bock et al., 2004; Wise et al., 2014). The available drug options are limited to diminazene aceturate (Berenil ® , Hoechst Ltd, Frankfurt, Germany) and imidocarb dipropio- nate (Imizol ® , Schering-Plough, New Jersey, USA). Furthermore, di- minazene aceturate (DA) has been withdrawn from the European market due to strong toxicity, and circumstantial reports have docu- mented emerging resistance to the current remedies (Mosqueda et al., 2012). Therefore, the research to discover new drugs and drug targets is https://doi.org/10.1016/j.ttbdis.2018.04.019 Received 21 December 2017; Received in revised form 19 April 2018; Accepted 26 April 2018 ⁎ Corresponding author at: National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Nishi 2 Sen-11, Inada-cho Obihiro, Hokkaido, 080-8555, Japan. E-mail addresses: tayebwa.dickson@gmail.com (D.S. Tayebwa), tuvshintulga@gmail.com (B. Tuvshintulga), guswanto7@gmail.com (A. Guswanto), arifin.budiman.fkh@gmail.com (A.B. Nugraha), gaberbatiha@gmail.com (G.E.-S. Batiha), sgantuya@gmail.com (S. Gantuya), Dr_moh_abdo2008@mans.edu.eg (M.A. Rizk), vpato2009@gmail.com (P. Vudriko), Siva@obihiro.ac.jp (T. Sivakumar), yokoyama@obihiro.ac.jp (N. Yokoyama), igarcpmi@obihiro.ac.jp (I. Igarashi). Abbreviations: CI, Combination index value; Cpt, Camptothecin; DA, Diminazene aceturate; DDW, Double distilled water; iRBC, Infected red blood cells; NC, Nitidine chloride; NC-IP, Nitidine chloride intraperitoneally administered; NC-Oral, Nitidine chloride orally administered; NC-DA, Nitidine chloride-diminazene aceturate combination; Cpt-DA, Camptothecin- diminazene aceturate combination Ticks and Tick-borne Diseases xxx (xxxx) xxx–xxx 1877-959X/ © 2018 Published by Elsevier GmbH. Please cite this article as: Tayebwa, D.S., Ticks and Tick-borne Diseases (2018), https://doi.org/10.1016/j.ttbdis.2018.04.019