Babesiosis

For patient information click here Template:DiseaseDisorder infobox Template:Search infobox Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Babesiosis is an uncommon malaria-like parasitic disease caused by protozoan parasites of the genus Babesia.

Epidemiology

Babesiosis is a vector-borne illness usually transmitted by ticks. (Babesia microti uses the same tick vector, Ixodes scapularis, as Lyme disease does, and frequently occurs in conjunction with it.) In babesia-endemic areas, the organism can also be transmitted by blood transfusion. The disease exists mostly in Eastern Long-Island and its barrier island, Fire Island, and the islands off the coast of Massachusetts. It is sometimes called "The Malaria of The North East."

Babesiosis causes a disease very similar to Malaria. In mild cases, people may experience mild fevers and anemia. In more severe cases, fevers go up to 105 degrees with shaking chills, and anemia (hemolytic anemia) can become severe. Organ failure may follow including adult respiratory distress syndrome.

Infection with Babesia parasites can be asymptomatic or cause a mild non-specific illness, and therefore many cases go unnoticed. It may also cause severe disease. While most severe cases occur in the very young, very old, or persons with underlying medical conditions (such as immunodeficiency) and those without a spleen, they can occur in normal individuals. Indeed, both the incidence or all cases of babesiosis and severe cases are increasing rapidly. Some cases are identified when patients with another tick-borne illness are screened for babesiosis.

Little is known about the occurrence of Babesia species in malaria-endemic areas, where Babesia can easily be misdiagnosed as Plasmodium.

Pathophysiology

Babesia parasites reproduce in red blood cells, where they can be seen as cross-shaped inclusions (4 merozoites asexually budding but attached together forming a structure looking like a "Maltese Cross") and cause hemolytic anemia, quite similar to malaria.

Note that unlike the Plasmodium parasites that cause malaria, Babesia species lack an exo-erythrotic phase, so the liver is usually not affected.

Diagnosis

Babesiosis is easy to diagnose but only if it is suspected. It will not show up on any routine tests. It must be suspected when a persons with exposure in an endemic area develops persistent fevers and hemolytic anemia. Babesiosis can be diagnosed by direct examination of the blood (see photo), with serology, or with PCR-based tests. Other laboratory findings include decreased numbers of red blood cells and platelets on complete blood count.

Treatment

Most cases of babesiosis resolve without any specific treatment. For ill patients, treatment is usually a two-drug regimen. The traditional regimen of quinine and clindamycin is often poorly tolerated; recent evidence suggests that a regimen of atovaquone and azithromycin can be equally effective . In life-threatening cases, exchange transfusion is performed. In this procedure, the infected red blood cells are removed and replaced with fresh ones.

References

• Herwaldt BL, Persing DH, Précigout EA, et al. A fatal case of babesiosis in Missouri: Identification of another piroplasm that infect humans. Ann Intern Med 1996;124:643-65.
• Pershing DH, Herwaldt BL, Glaser C, et al. Infection with a Babesia-like organism in northern California. N Engl J Med 1995;332:298-303.

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