Hemoparasitization by Theileria in the loggerheads Carettacaretta of the Mediterranean Sea

Theileria is a small Apicomplexan parasite considered as the scourge of the cattle industry, here detected for the first time in the blood cells of Caretta caretta from the Mediterranean Sea. In the early stage of infection by Theileria, rounded forms, defined schizonts, occur in lymphocytes and heterophils. After lysis of these leukocytes, the schizonts shift into plasmatic rounded free forms named merozoites. The latter enter the erythrocytes producing two, three, or four bacilliform daughter cells and curved forms similar to trophozoites and sometimes larger crescent-shaped forms similar to gametocytes. The differential recognition of Babesia, which is also a member of the Theileriidae versus Theileria is based on observing the early stages of Theileria in leukocytes, which Babesia is not parasitic. Infestations of Theileria are first recognized in loggerheads by their presence in leukocytes.