Skip to content

Babesiosis

Basics

  • Caused by intraerythrocytic protozoan Babesia species.
  • Geographic distribution mainly Northeastern and upper Midwest U.S.; sporadic global cases.
  • Incubation: 5-33 days, up to 9 weeks post-transfusion.
  • Systems affected: cardiovascular, GI, hemic/lymphatic/immunologic, musculoskeletal, nervous, pulmonary, renal.
  • Pediatric, pregnancy, and geriatric considerations noted.

Epidemiology

  • Most patients in 40s-50s.
  • Coinfection with other tick-borne diseases common (Lyme, ehrlichiosis).
  • Approx. 2,000 cases/year reported to CDC (2020 data).
  • Prevalence hard to estimate due to asymptomatic cases.

Etiology & Pathophysiology

  • Main agents: B. microti (US), B. divergens, B. bovis (Europe), B. duncani (US).
  • Vectors: Ixodes dammini/scapularis (deer tick), Ixodes ricinus.
  • Reservoir: white-footed deer mouse.
  • Infection via tick saliva; sporozoites infect RBCs causing hemolysis.
  • Humans are dead-end hosts.

Risk Factors

  • Residence in endemic areas.
  • Asplenia, immunosuppression, advanced age.

Prevention

  • Avoid endemic areas May-September.
  • Use insect repellents with DEET (10-35%) and permethrin-treated clothing.
  • Daily tick checks.

Associated Conditions

  • Coinfection with Borrelia burgdorferi and Ehrlichia spp.

Diagnosis

History

  • Travel or residence in endemic areas.
  • Symptoms similar to malaria: fever, fatigue, chills, sweats, headache, myalgia, anorexia, cough, arthralgia, nausea.
  • Severe disease in comorbid patients.

Physical Exam

  • High fever, hemodynamic instability possible.
  • Mild hepatosplenomegaly.
  • Rare rash; consider Lyme disease if rash present.
  • CNS involvement: headache, photophobia, neck stiffness, altered sensorium.
  • Jaundice, dark urine late.

Differential Diagnosis

  • Bacterial sepsis, hepatitis, Lyme disease, ehrlichiosis, Rocky Mountain spotted fever.
  • Malaria, HIV, EBV, HELLP syndrome (pregnancy).

Tests

  • Labs: hemolytic anemia, elevated LDH, mild leukopenia, elevated transaminases, renal dysfunction.
  • Blood smear (Wright/Giemsa): intraerythrocytic parasites, pathognomonic Maltese cross tetrads.
  • Serology: IgM by IFAT; titers >1:64 or 4-fold rise diagnostic.
  • PCR: highly sensitive/specific; useful for monitoring.
  • Animal inoculation in refractory diagnosis.

Treatment

General Measures

  • Empiric doxycycline in endemic areas to cover coinfections until testing complete.
  • Treat asymptomatic patients only if parasitemia >3 months.

Medications

  • First line (mild-moderate): atovaquone 750 mg PO BID (with fatty meal) + azithromycin (loading 500 mg BID day 1, then 250 mg daily).
  • Pediatrics: weight-based dosing of above agents.
  • Severe disease: IV azithromycin and atovaquone or oral quinine plus IV clindamycin.
  • Persistent/relapsing: 6-week course, 2 weeks after negative smear.
  • Second line: quinine + clindamycin (preferred for severe cases).
  • Other agents (tetracycline, primaquine, sulfadiazine) less consistent efficacy.

Alerts

  • Clindamycin may cause C. difficile colitis.

Referral

  • Infectious disease and hematology consult for severe disease and exchange transfusion consideration (parasitemia >10%, asplenia, massive hemolysis).

Admission

  • Severe babesiosis with organ compromise.
  • Exchange transfusion for high parasite load or critical illness.

Follow-Up

  • Monitor parasitemia and hematocrit until clinical and parasitological resolution.
  • Mild/moderate disease improves in 48 hours; full resolution by 3 months.
  • Risk factors for severity: ALP >125 U/L, WBC >5x10^9/L, cardiac abnormality, splenectomy, murmur, parasitemia ≥4%.

Complications

  • CHF, DIC, ARDS, renal failure, coma, death.
  • Warm autoimmune hemolytic anemia in asplenic patients.

Clinical Pearls

  • Tick must be attached >24 hours for transmission.
  • Most patients unaware of tick bite.
  • First-line treatment: atovaquone plus azithromycin.
  • Coinfection with Lyme and ehrlichiosis common; doxycycline covers these.
  • Untreated infections may persist silently for months or years.