Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content + Download Section PDF Listen ++ For further information, see CMDT Part 35-05: Babesiosis + Key Features Download Section PDF Listen +++ +++ Essentials of Diagnosis ++ History of tick bite or exposure to ticks Fever, flu-like symptoms, anemia Intraerythrocytic parasites on Giemsa-stained blood smears Positive serologic tests +++ General Considerations ++ An uncommon intraerythrocytic infection caused mainly by Babesia species and transmitted by Ixodes ticks Most cases in the United States occurs in the coastal northeast, with some cases also in the upper midwest The incidence of the disease appears to be increasing in some areas Caused by Babesia divergens in Europe Caused by Babesia venatorum in China Can be transmitted by blood transfusion, but blood supplies are not screened A survey of a large set of blood samples from endemic regions of the United States identified ~0.4% as potentially infectious for B microti + Clinical Findings Download Section PDF Listen +++ ++ Serosurveys suggest that asymptomatic infections are common in endemic areas With B microti infections Symptoms appear 1 to several weeks after a tick bite Parasitemia is evident after 2–4 weeks Typical flu-like illness develops gradually and is characterized by Fever Malaise Fatigue Headache Anorexia Myalgia Other findings may include nausea, vomiting, abdominal pain, arthralgia, sore throat, depression, emotional lability, anemia, thrombocytopenia, elevated transaminases, and splenomegaly B divergens infections Most cases seen in Europe in patients who have had splenectomy These infections progress rapidly with High fever Severe hemolytic anemia Jaundice Hemoglobinuria Acute kidney injury Mortality rates are over 40% + Diagnosis Download Section PDF Listen +++ ++ Identification of the intraerythrocytic parasite on Giemsa-stained blood smears establishes the diagnosis Repeated smears are often necessary because well under 1% of erythrocytes may be infected, especially early in infection, although parasitemias can exceed 10% Diagnosis can also be made by PCR, which is more sensitive than blood smear An indirect immunofluorescent antibody test for B microti is available from the CDC Antibody is detectable within 2–4 weeks after the onset of symptoms and persists for months A four-fold increase in antibody titer between acute and convalescent sera confirms acute infection + Treatment Download Section PDF Listen +++ +++ Medications ++ Standard therapy for mild to moderate disease is a 7-day course of atovaquone (750 mg orally every 12 hours) plus azithromycin (600 mg orally once daily), which is equally effective and better tolerated than the alternative regimen, a 7-day course of quinine (650 mg orally three times daily) plus clindamycin (600 mg orally three times daily) However, there is more experience using quinine plus clindamycin, and this regimen is recommended by some experts for severe disease +++ Therapeutic Procedures ++ Exchange transfusion has been used successfully in severely ill asplenic patients and those with parasitemia > 10% + Outcomes Download Section PDF Listen +++ +++ Complications ++ Severe complications are most likely to occur in older persons or in those who have had splenectomy Serious complications include Respiratory failure Hemolytic anemia Disseminated intravascular coagulation Heart failure Acute kidney injury +++ Prognosis ++ Most patients have a mild illness and recover without therapy Disease is usually self-limited Parasitemia may continue for months to years, with or without symptoms In a study of hospitalized patients, the mortality rate was 6.5% + References Download Section PDF Listen +++ + +Krause PJ. Human babesiosis. Int J Parasitol. 2019 Feb;49(2):165–74. [PubMed: 30690090] + +Moritz ED et al. Screening for Babesia microti in the U.S. blood supply. N Engl J Med. 2016 Dec 8;375(23):2236–45. [PubMed: 27959685] + +Sanchez E et al. Diagnosis, treatment, and prevention of Lyme disease, human granulocytic anaplasmosis, and babesiosis: a review. JAMA. 2016 Apr 26;315(16):1767–77. [PubMed: 27115378]