Protozoal infection causing fever, chills, myalgia, and hemolytic anemia; can occur as coinfection with Lyme disease. Vector is deer tick. Definitive diagnosis is detection of basket-shaped intraerythocyte parasites. Condition leads to severe and often fatal infections in splenectomized patients. Treatment is pentamidine, chloroquine phosphate, or increasingly, Mepron or Malarone.