Molecular phylogeny of piroplasmids: is there more to come?

SCHNITTGER L; ASCENCIO M; RODRIGUEZ AE; FLORIN-CHRISTENSEN M

Congreso; International Congress of Tropical Veterinary Medicine 2nd Joint AITVM-STVM Meeting; 2018

Piroplasmids aretick-transmitted hemoprotozooans that infect mammals and birds, and which areacknowledged for their major impact on farm and pet animal health andassociated economic costs worldwide. Additionally, piroplasmid infections ofwildlife can be fatal if associated with stressful management practices; andhuman babesiosis, also transmitted by blood transfusion, is an increasingpublic-health concern. A comprehensive overview of the classical taxonomic criteriathat have been used to define piroplasmids into the genus Babesia, Cytauxzoonand Theileria parasites, as well as the need for a thoroughtaxonomic revision will be outlined. Important milestones in the naturalhistory of piroplasmids as for example, the invention of the intracellular andtick-vertebrate life style will be discussed. Previously, phylogenetic analysisof 18S rRNA genes resulted in a molecular classification of six monophyleticgroups: four Babesia, one Cytauxzoon, and one Theileria lineage.Based on currently available data, the molecular phylogeny of piroplasmid 18SrRNA genes has been revisited, revealing at least ten monophyletic piroplasmidlineages. The constructed tree allows observing important insights and patternsof piroplasmid evolution with respect to the nature of piroplasmiddiversification, the frequency of host switching, and the timeframe ofpiroplasmid evolution. Furthermore, the paraphyly of human-infecting Babesiaspecies and potential consequences for treatment will be outlined. Themethodological difficulties and the progressive dynamics of piroplasmidclassification will be demonstrated based on selected species/groups of Theileriaand Babesia parasites. Finally, research strategies to improve andaccelerate the knowledge on piroplasmid phylogeny will be proposed.