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Last reviewed: 28 Oct 2023
Last updated: 06 Jun 2023



History and exam

Other diagnostic factors

  • constitutional symptoms
  • pyrexia
  • jaundice
  • hepatosplenomegaly
  • petechiae, splinter hemorrhages, or ecchymoses
  • dark urine
  • conjunctival injection
  • cough
  • sore throat
  • photophobia
Other diagnostic factors

Risk factors

  • residence in or travel to an endemic region
  • exposure to Ixodes scapularis ticks
  • blood transfusion
  • asplenia
  • immunosuppression
  • age >50 years
  • Lyme disease
  • human granulocytic anaplasmosis
  • maternal infection during pregnancy
More risk factors

Diagnostic investigations

1st investigations to order

  • peripheral blood smear (Giemsa or Wright stained)
  • polymerase chain reaction for babesial DNA
  • CBC
  • LFTs
  • serum creatinine and blood urea nitrogen (BUN)
  • urinalysis
  • ELISA and/or immunofluorescence assay for Lyme disease
  • polymerase chain reaction and/or immunofluorescence assay or buffy coat smear for human granulocytic anaplasmosis
More 1st investigations to order

Investigations to consider

  • indirect immunofluorescence antibody assay for Babesia microti
  • IgG/IgM immunoblot for Lyme disease
  • HIV serology
More investigations to consider

Treatment algorithm


asymptomatic documented infection

mild to moderate disease

acute severe disease


recurrent or refractory disease



Sarah Hochman, MD

Assistant Professor

Department of Medicine

Division of Infectious Diseases and Immunology

New York University School of Medicine

New York



SH declares that she has no competing interests.

Louis Weiss, MD, MPH
Louis Weiss

Professor of Medicine

Division of Infectious Diseases

Professor of Pathology

Division of Parasitology and Tropical Medicine

Albert Einstein College of Medicine




LW has received grant funding from the National Institute of Allergy and Infectious Diseases. He is also the author of references cited in this topic.

Peer reviewers

Jeremy Gray, BSc, MSc, PhD


Department of Environmental Resource Management

University College Dublin



Republic of Ireland


JG declares that he has no competing interests.

Sam Telford III, ScD

Associate Professor of Biomedical Sciences

Division of Infectious Diseases

Cummings School of Veterinary Medicine

Tufts University




ST has active research funding from the NIH. ST is an author or co-author of numerous primary publications on the biology of babesiosis, as well as reviews that have been referenced in this topic.

Raymond J. Dattwyler, MD

Professor of Medicine and Microbiology/Immunology

Chief of Allergy, Immunology and Rheumatology

New York Medical College




RJD declares that he has no competing interests.

  • Babesiosis images
  • Differentials

    • Lyme disease
    • Human granulocytic anaplasmosis
    • Rocky Mountain spotted fever
    More Differentials
  • Guidelines

    • Tickborne diseases of the United States: a reference manual for health care providers
    • 2020 Guideline on diagnosis and management of babesiosis
    More Guidelines
  • Patient leaflets

    Lyme disease

    Malaria prevention

    More Patient leaflets
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