I. Pathophysiology and epidemiology
  1. An infection with Babesia microti, a red blood cell parasite
  2. Endemic in southern New England and the Midwestern United States
  3. Lifecycle involves the Ixodes scapularis tick, white-footed mouse, and white tail deer (the latter just as a vector for the tick)

II. Clinical features
  1. Has a prolonged incubation period (typically 1-6wks but may be months)
  2. Most symptomatic infections are mild-to-moderate with gradual onset of:
    1. Malaise and fatigue
    2. Then, intermittent fever with chills and sweats
    3. Loss of appetite
    4. Headache
    5. Arthralgias and myalgias
    6. Cough
    7. Px: Mild enlargement of liver and/or spleen
    8. Lab: Mild anemia and thrombocytopenia, elevation of transaminases; WBC may be elevated, normal, or low
  3. Severe disease (can include any or all of the items below)
    1. Risk factors for severe disease: age > 50yo, immunocompromise (e.g. splenectomy status or HIV infection), Borrelia burgdorferi infection
    2. Severe anemia
    3. Respiratory failure
    4. Heart failure
    5. Renal failure
    6. Disseminated intravascualr coagulation
III. Diagnosis
  1. Traditional gold standard = identification of organism on blood smear
  2. Babesia PCR is available and may be helpful in early infection or during convalescence, when parasite load is low
  3. Serologic testing is available
IV. Management (all meds PO unless otherwise indicated)
  1. Duration of treatment: 7-10d for mild-moderate disease; no clear standards exist for severe disease
  2. Mild-to-moderate disease:
    1. Atovaquone 750mg (in child, 20mg/kg max 750mg) BID + azithromycin 1000mg QD (in child, 10mg/kg on day 1 then 5mg/kg/d)
    2. Clindamycin 600mg (in child, 6-10mg/kg, max 600mg) Q8h + quinine 650mg (in child, 8mg/kg max 650mg) Q8h
  3. Severe disease:
    1. Clindamycin 300-600mg (in child, 6-10mg/kg, max 650mg) IV Q6h + quinine 650mg (in child, 8mg/kg max 650mg) Q8h
Sources include Core Content Review of Family Medicine, 2012)