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Clinical manifestations, diagnosis, treatment, and prevention of babesiosis

Jeffrey A Gelfand, MD, FACP
Edouard G Vannier, PhD
Section Editor
Johanna Daily, MD, MSc
Deputy Editor
Elinor L Baron, MD, DTMH


Babesiosis is an infectious disease caused by protozoa of the genus Babesia. Babesia protozoa infect vertebrate animals and cause lysis of host red blood cells [1]. The zoonotic cycle is maintained by tick vectors. Human infection is accidental; humans are not definitive reservoir hosts. Babesiosis may also be acquired by blood transfusion, particularly in areas endemic for B. microti and B. duncani.

The main etiologic agents of human babesiosis are B. microti in the northeastern and upper midwestern regions of the United States and B. divergens in Europe [2]. Other Babesia species are occasionally but rarely identified in humans (eg, B. divergens-like organisms in the Midwest and on the west coast of the United States; B. duncani on the west coast of the United States; and B. venatorum in Europe and mainland China).

Treatment modalities depend on the species of Babesia and the immune status of the host. The clinical manifestations, diagnosis, treatment, and prevention of babesiosis will be reviewed here. The epidemiology and pathogenesis of this infection are discussed separately. (See "Epidemiology and pathogenesis of babesiosis".)


Babesia infections range from asymptomatic to severe and are sometimes fatal. The severity of infection depends on the Babesia species and the immune status of the host.

B. microti — B. microti is the predominant species in the United States whereas B. microti-like organisms have been implicated in Europe, Asia, and Australia. Clinical manifestations may be absent or range from mild to severe, sometimes resulting in death. Symptoms typically develop one to six weeks after the bite of an infected tick [2,3]. An incubation period of 12 weeks was described in one case report. The median interval from transfusion to onset of symptoms is 37 days (range 11 to 176 days) [4].


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Literature review current through: Sep 2016. | This topic last updated: Sep 29, 2016.
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