What are the symptoms of babesiosis?

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From the Guidelines

Babesiosis symptoms range from mild to severe and can include fever, chills, sweating, fatigue, headache, muscle aches, joint pain, and loss of appetite. The disease can be asymptomatic in some individuals, making it difficult to diagnose. Symptoms typically appear 1-4 weeks after a tick bite, though many patients don't recall being bitten. Severe cases are more common in elderly individuals, those without a spleen, with weakened immune systems, or with other serious health conditions. These patients may develop complications like low blood pressure, respiratory failure, kidney failure, or even death. Babesiosis is caused by Babesia parasites (primarily B. microti in the US) that infect red blood cells after transmission through the bite of infected blacklegged ticks. Some key symptoms and signs include:

  • Fever
  • Chills
  • Sweats
  • Myalgia
  • Arthralgia
  • Anorexia
  • Nausea
  • Vomiting
  • Fatigue
  • Splenomegaly
  • Hepatomegaly
  • Jaundice
  • Hemolytic anemia with an elevated reticulocyte count
  • Thrombocytopenia
  • Proteinuria
  • Elevated levels of liver enzymes, blood urea nitrogen, and creatinine 1. If you experience these symptoms after potential tick exposure, seek medical attention promptly as treatment with antiparasitic medications like atovaquone plus azithromycin or clindamycin plus quinine is most effective when started early. In severe cases, partial or complete RBC exchange transfusion may be indicated, especially in patients with high-grade parasitemia, significant hemolysis, or renal, hepatic, or pulmonary compromise 1. Patients with moderate-to-severe babesiosis should be monitored closely during therapy to ensure clinical improvement and improvement of parasitemia and other laboratory abnormalities 1.

From the Research

Symptoms of Babesiosis

The symptoms of babesiosis can range from mild to severe and may include:

  • Flu-like illness
  • Anemia
  • Thrombocytopenia
  • Hemolytic anemia
  • Disseminated intravascular coagulation
  • Acute renal failure
  • Respiratory failure
  • Fever
  • Hemolysis

Severity of Symptoms

The severity of symptoms can vary depending on the individual and may be more severe in certain groups, such as:

  • Immunocompromised individuals
  • Those who have undergone splenectomy
  • Older adults
  • Individuals with underlying medical conditions

Diagnosis and Treatment

Diagnosis of babesiosis is typically confirmed by identification of Babesia parasites on blood smear or Babesia DNA with polymerase chain reaction 2, 3, 4. Treatment usually consists of a 7-10 day course of antibiotics, such as clindamycin and quinine, or atovaquone and azithromycin 3, 4, 5. In severe cases, exchange transfusion may be necessary to reduce parasite load and replace damaged red blood cells 2, 3, 6.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Babesiosis diagnosis and treatment.

Vector borne and zoonotic diseases (Larchmont, N.Y.), 2003

Research

Human Babesiosis.

Infectious disease clinics of North America, 2022

Research

Babesiosis: An Update on Epidemiology and Treatment.

Current infectious disease reports, 2003

Research

Heavy parasitemia in babesiosis treated without adjunctive red cell exchange.

Transfusion and apheresis science : official journal of the World Apheresis Association : official journal of the European Society for Haemapheresis, 2019

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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