CSF exam showed a lymphocytic pleocytosis. Giemsa stained peripheral blood smear showing many intra-erythrocytic ring forms with some cells demonstrating multiple ring forms. This malarial-like protozoa can be transmitted by the bite of an infected Ixodes scapularis tick. Diagnosis can be made by observation of the merozoites of Babesia microti within red blood cells. Travel history is important to the diagnosis of this infection, as the morphology of the intra-erythrocytic parasite remarkably resembles Plasmodium falciparum.
Splenectomized patients are prone to more severe and apparent illness.