DurgicalDurgical
EN
Open the app

Microbiology · Apicomplexans

Babesia spp. !

  • Parasite
  • For completeness

A red-cell parasite spread by ticks. It mimics malaria and is severe in people without a spleen or with weak immunity.

Updated 2026-11-01

Also called: Babesia microti, Babesia divergens

At a glance

Shape
Small rings, pear shapes and Maltese-cross tetrads
Family
Babesiidae
Type
Intraerythrocytic apicomplexan protozoan (piroplasm)
Stain
Giemsa on thick and thin films
Size
Small intraerythrocytic forms

Morphology

  • Small rings, sometimes several per cell, resembling P. falciparum.
  • Tetrads (four parasites in a Maltese cross), highly characteristic.
  • No malaria pigment and no gametocytes in the blood.
  • Extracellular forms may be seen.

Transmission

  • Bite of Ixodes ticks (in the United States, I. scapularis; in Europe, I. ricinus).
  • Transfusion of blood from infected donors.
  • Rarely transplacental.

Reservoir: White-footed mouse (B. microti); Cattle (B. divergens)

Vector: Ticks of the genus Ixodes, the same ones that transmit Lyme disease.

Isolation precautions

What the care team adds to standard precautions.

  • Standard

Life cycle

  1. An infected tick injects sporozoites while feeding.
  2. Sporozoites invade red cells directly; there is no liver stage.
  3. Inside the red cell they divide by budding, forming rings and tetrads.
  4. Rupture of the cell releases merozoites that infect other red cells.
  5. A tick takes up parasites from an infected rodent; the sexual phase occurs in the tick.
  6. Humans are accidental hosts with no role in the natural cycle.

Virulence factors

  • Invasion and lysis of red cells: hemolytic anemia.
  • The spleen is key for clearance; asplenia allows high parasitemia.
  • Systemic inflammation with risk of multi-organ failure.

Diseases it causes

  • Babesiosis: fever and hemolytic anemia, mild to severe, potentially fatal in people without a spleen, the elderly or the immunocompromised. Babesiosis →

Clinical picture

  • Many cases are silent.
  • Fever, chills, sweats, myalgia and fatigue one to several weeks after the bite.
  • Hemolytic anemia, jaundice, dark urine and low platelets.
  • Severe forms: respiratory distress, kidney failure, disseminated intravascular coagulation.

Diagnosis

  • Giemsa blood smear: rings without pigment and tetrads.
  • PCR to confirm, identify the species and detect low parasitemia.
  • Serology (immunofluorescence) as support.
  • Checking for coinfection with other Ixodes-borne infections.

Treatment

Atovaquone plus azithromycin in most cases; in severe disease clindamycin with quinine and exchange transfusion have been used in specialized centers.

Drug class only; doses and regimens are set by the clinician from the current guideline.

In Pharmacology:

Prevention

  • Avoiding tick bites: long clothing, repellents and skin checks after time in the woods.
  • Prompt removal of attached ticks.
  • Blood-donor screening in endemic areas.

Vaccine: There is no human vaccine.

Test yourself

Think of the answer, then tap the question to see it.

Which smear form is typical of Babesia?

The tetrad or Maltese cross: four parasites joined inside one red cell.

Which patients are at highest risk of severe babesiosis?

People without a spleen, the elderly and the immunocompromised, for example with HIV or on rituximab.

Which vector transmits Babesia microti?

The Ixodes scapularis tick, which also transmits Lyme disease.

Which findings help separate Babesia from Plasmodium falciparum on the smear?

Babesia makes no pigment or gametocytes and can form tetrads; a history of ticks or transfusion also helps.

Add to my cards (4)

← Back to the group: Apicomplexans

Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: Babesiosis (CDC (DPDx), 2024); Clinical Overview of Babesiosis | Babesiosis | CDC (CDC, 2024).

Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake

Representative model, for educational purposes only.