Abstract
Although apicomplexan parasites of the group Piroplasmida represent commonly identified global risks to both animals and humans, detailed knowledge of their life cycles is surprisingly limited. Such a discrepancy results from incomplete literature reports, nomenclature disunity and recently, from large numbers of newly described species. This review intends to collate and summarize current knowledge with respect to piroplasm phylogeny. Moreover, it provides a comprehensive view of developmental events of Babesia, Theileria, and Cytauxzoon representative species, focusing on uniform consensus of three consecutive phases: (i) schizogony and merogony, asexual multiplication in blood cells of the vertebrate host; (ii) gamogony, sexual reproduction inside the tick midgut, later followed by invasion of kinetes into the tick internal tissues; and (iii) sporogony, asexual proliferation in tick salivary glands resulting in the formation of sporozoites. However, many fundamental differences in this general consensus occur and this review identifies variables that should be analyzed prior to further development of specific anti-piroplasm strategies, including the attractive targeting of life cycle stages of Babesia or Theileria tick vectors.
Highlights
The group Piroplasmida received its name after its pear-shaped intra-erythrocytic stages and refers to intracellular parasites transmitted exclusively by hard ticks (Ixodidae) (Mehlhorn and Schein, 1993; Votypka et al, 2017)
Species of the group Piroplasmida possess a characteristic lifecycle that significantly differs from other apicomplexan parasites
A uniform consensus describes three consecutive phases (Figure 1): (i) schizogony and merogony, asexual multiplication in blood cells of the vertebrate host; (ii) gamogony, sexual reproduction inside the tick midgut, later followed by kinete invasion of the tick internal tissues; and (iii) sporogony, asexual proliferation in tick salivary glands resulting in the formation of sporozoites (Box 1)
Summary
Marie Jalovecka * 1,2,3 , Ondrej Hajdusek 2, Daniel Sojka 2, Petr Kopacek 2 and Laurence Malandrin 1. Apicomplexan parasites of the group Piroplasmida represent commonly identified global risks to both animals and humans, detailed knowledge of their life cycles is surprisingly limited. Such a discrepancy results from incomplete literature reports, nomenclature disunity and recently, from large numbers of newly described species. This review intends to collate and summarize current knowledge with respect to piroplasm phylogeny It provides a comprehensive view of developmental events of Babesia, Theileria, and Cytauxzoon representative species, focusing on uniform consensus of three consecutive phases: (i) schizogony and merogony, asexual multiplication in blood cells of the vertebrate host; (ii) gamogony, sexual reproduction inside the tick midgut, later followed by invasion of kinetes into the tick internal tissues; and (iii) sporogony, asexual proliferation in tick salivary glands resulting in the formation of sporozoites.
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