Updated: 9/28/2020


Review Topic
  • Snapshot
    • A 68-year-old man presents to the physician with complaints of fever, malaise, and chills for the past few weeks. He says that he and his wife recently visited New Hampshire for a summer family reunion, where they hiked in the White Mountains. His temperature is 102°F (38.9°C). Physical exam is notable for a palpable spleen. Laboratory studies are significant for a hematocrit of 30%, decreased serum haptoglobin levels, and an elevated reticulocyte count. A peripheral blood smear is obtained, and confirms the diagnosis.
  • Introduction
    • Epidemiology
      • location
        • northeastern United States (same geography as Lyme disease)
      • risk factors
        • outdoor activities that increase exposure to ticks
    • Pathogenesis
      • transmission
        • Ixodes tick is the vector for the parasite
          • same vector as Borrelia burgdorferi which causes Lyme disease; co-infection may occur
        • white-footed mouse is a reservoir
    • Associated conditions
      • hemolytic anemia
  • Presentation
    • Symptoms
      • fever
        • may be sustained or intermittent
      • chills
      • malaise
      • fatigue
      • arthralgias
      • nausea and vomiting
      • dark urine
    • Physical exam
      • typically few, if any, physical findings
      • in a minority of patients
        • jaundice
        • splenomegaly
        • hepatomegaly
        • petechiae
        • ecchymoses
  • Studies
    • Labs
      • complete blood count with differential
        • mild-to-severe hemolytic anemia
        • lymphopenia
        • thrombocytopenia
      • decreased serum haptoglobin levels
      • elevated reticulocyte counts
    • Histology
      • peripheral blood smear
        • Giemsa-stained or Wright-stained
          • intraerythrocytic ring forms with a central pallor
          • merozoites arranged in tetrad configuration resembling a Maltese cross (pathognomonic of babesiosis)
    • Making the diagnosis
      • based on clinical presentation and peripheral blood smear findings
  • Differential
    • Malaria
      • distinguishing factor
        • visualization of Plasmodium on peripheral blood smear
    • Lyme disease
      • distinguishing factor
        • erythema migrans (bulls-eye rash)
    • Erlichiosis
      • distinguishing factor
        • southeastern and mid-Atlantic United States
  • Treatment
    • Medical
      • IV atovaquone and IV azithromycin
      • IV clindamycinand oralquinine
  • Complications
    • Severe hemolytic anemia
    • Thrombocytopenia
    • Disseminated intravascular coagulation (DIC)
    • Death
      • babesiosis can be severe or life-threatening particularly in the following groups
        • asplenic patients
        • immunocompromised patients
        • elderly

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