Author: Dr Marie Hartley, staff writer, 2009.

What is babesiosis?

Babesiosis is a parasitic infection caused by protozoa of the genus Babesia. Various species of Babesia cause the disease throughout the world. Most reported cases have occurred in the United States, with Babesia microti the main species responsible.

Babesia are transmitted by the bite of ixodid ticks. These ticks are the same vector responsible for the transmission of Lyme disease, and consequently around 20% of patients with babesiosis are co-infected with Lyme disease. As well as the tick vector, Babesia require a vertebrate reservoir, most commonly mice or cattle. The ticks are most often found in wooded or grassy areas. Tick transmission usually occurs between the months of May to October.

The prevalence of babesiosis is unknown, because most patients are symptom-free. Surveys using serological testing to detect evidence of past infection, have shown around 10% of the population have been infected in highly endemic areas, such as Rhode Island. Other areas of the United States where tickborne transmission occurs include the Northeast and upper Midwest, especially in parts of New England, New York State, New Jersey, Wisconsin, and Minnesota.

While most cases of babesiosis are transmitted by ticks, cases of disease associated with blood transfusions have been reported.

What are the clinical features of babesiosis?

After a bite from an infected tick, Babesia cause lysis (rupture) of the host's red blood cells. Clinical features range from nil or mild symptoms, to severe disease and death.

Skin manifestations of babesiosis

How is babesiosis diagnosed?

Consider a diagnosis of babesiosis in:

Definitive diagnosis of babesiosis can be made by:

What is the treatment of babesiosis?

How can babesiosis be prevented?

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