Babesiosis

Babesiosis

• Babesiosis is caused by microscopic parasites that infect red blood cells and are spread by certain ticks.
• In the United States, tickborne transmission is most common in particular regions and seasons: it mainly occurs in parts of the Northeast and upper Midwest and usually peaks during the warm months.
• Although many people who are infected with Babesia do not have symptoms, for those who do effective treatment is available.
• Babesiosis is preventable, if simple steps are taken to reduce exposure to ticks.
• Babesia microti is transmitted by the bite of infected Ixodes scapularis ticks—typically, by the nymph stage of the tick, which is about the size of a poppy seed.
• ''Babesia infection can range from subclinical to severe. Symptoms, if any, usually develop within a few weeks or months after exposure but may first appear or recur many months later, particularly in persons who are or become immunosuppressed.

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Clinical features

• Clinically manifest Babesia infection is characterized by the presence of hemolytic anemia and nonspecific flu-like symptoms (e.g., fever, chills, body aches, weakness, fatigue).
• Some patients have splenomegaly, hepatomegaly, or jaundice.

Risk factors

• Risk factors for severe babesiosis include asplenia, advanced age, and other causes of impaired immune function (e.g., HIV, malignancy, corticosteroid therapy).
• Some immunosuppressive therapies or conditions may affect the clinical manifestations (e.g., the patient might be afebrile). Severe cases can be associated with marked thrombocytopenia, disseminated intravascular coagulation, hemodynamic instability, acute respiratory distress, myocardial infarction, renal failure, hepatic compromise, altered mental status, and death.

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Diagnosis

• Diagnosis of babesiosis requires a high index of suspicion, in part because the clinical manifestations are nonspecific.
• For acutely ill patients, the findings on routine laboratory testing frequently include hemolytic anemia and thrombocytopenia.
• Additional findings may include proteinuria, hemoglobinuria, and elevated levels of liver enzymes, blood urea nitrogen, and creatinine.
• If the diagnosis of babesiosis is being considered, manual (non-automated) review of blood smears should be requested explicitly.
• In symptomatic patients with acute infection, Babesia parasites typically can be detected by light-microscopic examination of blood smears, although multiple smears may need to be examined.
• Sometimes it can be difficult to distinguish between Babesia and Plasmodium (especially P. falciparum) parasites and even between parasites and artifacts (such as stain or platelet debris).
• Consider having a reference laboratory confirm the diagnosis—by blood-smear examination and, if indicated, by other means, such as molecular and/or serologic methods tailored to the setting/species.

Treatment

• Most asymptomatic persons do not require treatment.
• Treatment decisions should be individualized, especially for patients who have (or are at risk for) severe or relapsing infection.
• For ill patients, babesiosis usually is treated for at least 7-10 days with a combination of two prescription medications — typically either:
• Atovaquone PLUS azithromycin; OR
• Clindamycin PLUS quinine (this combination is the standard of care for severely ill patients).

The typical daily doses for adults are provided in the table below.

Drug	Adult dosage (usually treat for at least 7–10 days)
Atovaquone	750 mg orally twice a day
along with
Azithromycin	On the first day, give a total dose in the range of 500–1000 mg orally; on subsequent days, give a total daily dose in the range of 250–1000 mg
or
Clindamycin	600 mg orally 3 times a day or 300–600 mg intravenously 4 times a day
along with
Quinine	650 mg orally 3 times a day

Supportive care

• Antipyretics;
• Vasopressors (if the blood pressure is low and unstable);
• Blood transfusions;
• Exchange transfusions (in which portions of a patient’s blood or blood cells are replaced with transfused blood components);
• Mechanical ventilation; or
• Dialysis

Babesiosis Resources
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