| Summary: | Abstract Background Apicomplexan tick-borne pathogens that cause disease in companion animals include species of Babesia Starcovici, 1893, Cytauxzoon Neitz & Thomas, 1948, Hepatozoon Miller, 1908 and Theileria Bettencourt, Franca & Borges, 1907. The only apicomplexan tick-borne disease of companion animals that is known to occur in Australia is babesiosis, caused by Babesia canis vogeli Reichenow, 1937 and Babesia gibsoni Patton, 1910. However, no molecular investigations have widely investigated members of Apicomplexa Levine, 1980 in Australian ticks that parasitise dogs, cats or horses, until this present investigation. Results Ticks (n = 711) removed from dogs (n = 498), cats (n = 139) and horses (n = 74) throughout Australia were screened for piroplasms and Hepatozoon spp. using conventional PCR and Sanger sequencing. The tick-borne pathogen B. vogeli was identified in two Rhipicephalus sanguineus Latreille ticks from dogs residing in the Northern Territory and Queensland (QLD). Theileria orientalis Yakimov & Sudachenkov, 1931 genotype Ikeda was detected in three Haemaphysalis longicornis Neumann ticks from dogs in New South Wales. Unexpectedly, the exotic tick-borne pathogen Hepatozoon canis James, 1905 was identified in an Ixodes holocyclus Neumann tick from a dog in QLD. Eight novel piroplasm and Hepatozoon species were identified and described in native ticks and named as follows: Babesia lohae n. sp., Babesia mackerrasorum n. sp., Hepatozoon banethi n. sp., Hepatozoon ewingi n. sp., Theileria apogeana n. sp., Theileria palmeri n. sp., Theileria paparinii n. sp. and Theileria worthingtonorum n. sp. Additionally, a novel cf. Sarcocystidae sp. sequence was obtained from Ixodes tasmani Neumann but could not be confidently identified at the genus level. Conclusions Novel species of parasites in ticks represent an unknown threat to the health of companion animals that are bitten by these native tick species. The vector potential of Australian ticks for the newly discovered apicomplexans needs to be assessed, and further clinical and molecular investigations of these parasites, particularly in blood samples from dogs, cats and horses, is required to determine their potential for pathogenicity.
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