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  • Babesiosis is an infection of the Babesia species of intraerythrocytic protozoa, causing lysis of host red blood cells.
  • Spread by the deer tick (Ixodes scapularis)
    • People often unaware they are bitten
  • Natural reservior is the white footed mouse
  • Endemic in US, Europe, parts of Russia and China
    • Babesia Microti is pathogen in US
  • Possible to have co-infection with Lyme (same tick family)

Clinical Features

Differential Diagnosis

Tick Borne Illnesses


Peripheral blood smear showing "Maltese Cross" classic for babesiosis.
  • CBC
    • Often with depressed white count
  • Peripheral Blood Smears
    • Shows intracellular parasites: Maltese Cross sign
    • May need large smear as parasitemia can be as low as 1%
    • Can often be confused for malaria parasites
  • Electrolytes and renal function
  • LFTs
    • Total bilirubin and haptoglobin values reflect the intensity of the infection (hemolysis)
  • Lyme
  • Urine - hemolysis
  • CXR - rare but possible ARDS


Each regimin is for 10 days duration and option 1 is often used for mild parasitemia <4% with option two for sever cases with >4% parasite load

Option 1

Atovaquone (750mg BID) and Azithromycin (500-1000mg on first day, 250-1000mg on subsequent days)[1]

Option 2


  • 600 mg PO q8h x 7-10 days
  • Alt: 300-600mg IV q6h x 7-10 days
    • First Dose: 300-600mg IV x 1
  • Give with Quinine (650mg TID); use IV for severe infections


  • Clindamycin 20mg/kg/day for children and 25mg/kg/day for children for 7-10 days



  • Severe anemia (hemoglobin <10g/dL)
  • Parasitemia >4%
  • Mortality risk higher in asplenic patients


  • Parasitemia <4%
  • Asymptomatic or mild disease with intact spleen
  • Discharged patients should follow-up with primary care or infectious disease specialist

See Also

External Links


  • Tobler WD, Cotton D, Lepore T, Agarwal S, Mahoney EJ. Case Report: Successful non-operative management of spontaneous splenic rupture in a patient with babesiosis. World Journal of Emergency Surgery : WJES. 2011;6:4. doi:10.1186/1749-7922-6-4.
  1. Krause PJ, Lepore T, Sikand VK, Gadbaw J Jr, Burke G, Telford SR 3rd, et al. Atovaquone and azithromycin for the treatment of babesiosis. N Engl J Med. Nov 16 2000;343(20):1454-8.