Babesiosis B60.0

Zoonosis caused by babesias (protozoa parasitizing in erythrocytes) and transmitted by ticks. In humans, malaria-like clinical pictures (fever, anaemia, jaundice) can be triggered.

Plasmodium-like protozoa. Transmission by ticks (Ixodes dammini, Ixodes ricinus) or small rodents.

Babesia divergens: spread in Europe; transmission by Ixodes ricinus.

Babesia microti: transmitted by Ixodes dammini, infects red deer in the adult stage, rodents in the larval and nymph stage. Transmission by blood transfusion described.

• Babesiosis caused by Babesia divergens:
  • Parasitosis of cattle with large losses in livestock with worldwide distribution. Endemic mainly in subtropical and tropical regions.
  • In humans: Spread in Europe.
  • Transmission by Ixodes ricinus.
• Babesiosis caused by Babesia microti (in the USA, B. microti was detected in 3-11 % of Ixodes scapularis nymphs -Sanchez-Vicente S et al. 2023):
  • More common in humans than Babesia divergens.
  • Mainly occurring in splenectomized patients.
  • Mainly occurring in the USA (islands of Nantucket, Martha's Vineyard, Long Island; Massachusetts; New York and Connecticut).
  • Transmission by Ixodes dammini.
  • Reservoir are rodents.

Integument: Little itching at the tick bite, brown-red to black round tick body. A tick bite is not always memorable. Pale, discoloured, anaemic mucous membranes (oral cavity, lips). Often, but not always, a haemolytic icterus occurs. In individual cases mucous membrane hemorrhages, petechiae, purpura.

Incubation period: 1-4 weeks.

Babesia divergens infection: fever, chills, muscle and limb pain, hemolytic anemia, hemoglobinuria, hepatitis and nephropathy. Spleno- and hepatomegaly, dyspnea (due to anaemia and haemolysis). High lethality.

Babesia microti infection: usually latent or subclinical course. In rare, severe courses similar to Babesia divergent infection, rarely lethal.

Thick drop: Differentiation from malaria difficult.

Blood smear: low parasitemia, several smears necessary.

Serology: indirect fluorescent antibody test, antibody increase to be expected after 2-4 weeks (low specificity).

PCR: genome detection.

• Babesia microti infection:
• Therapy of choice: Clindamycin 3 times/day 600 mg p.o. and quinine 3 times/day 650 mg p.o. for 7-10 days.
• Alternatively, atovaquone twice a day 750 mg and azithromycin once a day 250 mg (500 mg on the first day) p.o. for 7-10 days.
• Babesia divergence infection:
• In severe cases: exchange transfusion.

Babesia divergens infection: High lethality.

Babesia microti infection: Frequently subclinical course, low lethality.

1. Genchi C (2007). Human babesiosis, an emerging zoonosis. Parasitologia 49: 29-31
2. Krause PJ et al. (2008) Persistent and relapsing babesiosis in immunocompromised patients. Clin Infect Dis Feb 46: 370-376
3. Sanchez-Vicente S et al (2023) Tick-Borne Co-Infections: Challenges in Molecular and Serologic Diagnoses. Pathogens 12:1371.