Disease

Babesia infection can range from subclinical to life-threatening. 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.

Clinically manifest Babesia infection is characterized by the presence of hemolytic anemia and nonspecific influenza-like symptoms (e.g. , fever, chills, body aches, weakness, fatigue). Splenomegaly, hepatomegaly, or jaundice may be evident.

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 mask or modulate the clinical manifestations (e.g. , the patient may 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.

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.

In symptomatic patients, Babesia parasites typically can be detected by light microscopic examination of blood smears. Examination by a reference laboratory should be considered for confirmation of the diagnosis, in part because it can be difficult to distinguish between Babesia and Plasmodium (especially P. falciparum). Molecular techniques can be used to detect low levels of parasites and to differentiate among Babesia species.

Although the diagnosis of babesiosis should be parasitologically confirmed whenever possible, antibody detection by serologic testing can provide supportive evidence for infection. However, antibody tests do not reliably distinguish active from prior infection. Serologic testing is relatively species specific. For example, if the antigen source for the assay is B. microti, serum from patients infected with B. duncani (or other Babesia species) will react minimally, if at all.

More on: Laboratory Diagnosis

Treatment

Most patients who are asymptomatic do not require treatment. Health care providers may consult with CDC staff about whether to treat someone who has babesiosis, what type(s) of therapy to use, how to monitor the status of the infection, and how long to treat. Treatment decisions should be individualized, especially for people 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.