Treatment algorithm

Please note that formulations/routes and doses may differ between drug names and brands, drug formularies, or locations. Treatment recommendations are specific to patient groups: see disclaimer

ACUTE

asymptomatic documented infection

1st line – observation

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ACUTE
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asymptomatic documented infection
1st line – 

observation

Antimicrobial therapy is not required unless parasites are seen on thin blood smear for more than 1 month. Monitoring parasitemia using polymerase chain reaction (PCR) testing is not indicated in asymptomatic immunocompetent hosts.[31]

mild to moderate disease

1st line – oral antimicrobial therapy

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ACUTE
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mild to moderate disease
1st line – 

oral antimicrobial therapy

Patients are generally immunocompetent, experience mild to moderate symptoms, have a parasitemia <4%, and are ambulatory and do not require hospital admission.[31]

Azithromycin plus atovaquone is the preferred first-line treatment option as it is clinically effective and well-tolerated. Azithromycin slightly increases the risk of pyloric stenosis in infants <6 weeks of age, and so should be used with caution in this group.[6][31]

Clindamycin plus quinine is an alternative option. This combination is less preferred as it is frequently associated with adverse effects such as tinnitus, vertigo, and gastrointestinal upset. However, it may be considered when azithromycin plus atovaquone is not tolerated or is unavailable. Clindamycin plus quinine is preferred when parasitemia and symptoms have failed to abate following initiation of atovaquone plus azithromycin.[6][31]

Treatment course is 7 to 10 days. The treatment duration may also need to be extended to at least 6 weeks in patients who are immunocompromised. Clinical improvement generally occurs within a few days of starting treatment. Fever and parasites on blood smear usually clear within a week. Monitoring parasitemia using peripheral blood smears is recommended during treatment of the acute illness; however, testing is not recommended once symptoms have resolved. Fatigue and low-grade parasitemia may persist for weeks or months after treatment. Further monitoring and treatment are rarely needed in these patients as relapse rarely occurs.[6][31]

Primary options

azithromycin: children: 10 mg/kg orally once daily (maximum 500 mg/dose) on the first day, followed by 5 mg/kg once daily (maximum 250 mg/dose); adults: 500 mg orally on the first day, followed by 250 mg orally once daily

and

atovaquone: children: 20 mg/kg orally twice daily, maximum 750 mg/dose; adults: 750 mg orally twice daily

Secondary options

clindamycin: children: 7-10 mg/kg orally three to four times daily, maximum 600 mg/dose; adults: 600 mg orally three times daily

and

quinine sulfate: children: 8 mg/kg orally three times daily, maximum 650 mg/dose; adults: 650 mg orally three times daily

acute severe disease

1st line – oral and parenteral antimicrobial therapy

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ACUTE
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acute severe disease
1st line – 

oral and parenteral antimicrobial therapy

Patients should be admitted to hospital and treated with a combination of either intravenous azithromycin plus oral atovaquone; or intravenous clindamycin plus oral quinine.

Azithromycin plus atovaquone is the preferred first-line treatment option as it is clinically effective and well-tolerated. Azithromycin slightly increases the risk of pyloric stenosis in infants <6 weeks of age, and so should be used with caution in this group. Clindamycin plus quinine is an alternative option when parasitemia and symptoms have failed to abate following initiation of azithromycin plus atovaquone (or the patient is unable to take azithromycin plus atovaquone). It is also the preferred option in children as there is a lack of evidence for the use of azithromycin plus atovaquone in children. Some experts may use intravenous quinidine in place of oral quinine; however, quinidine is no longer available in the US.[6]​[31]

Worsening of symptoms or increasing parasitemia despite azithromycin plus atovaquone followed by clindamycin plus quinine should prompt consideration of an alternative antimicrobial regimen.[31] Consult an infectious diseases specialist for guidance on an appropriate regimen. 

Treatment with the intravenous antibiotic should continue until symptoms abate, before the patient is switched to all oral therapy. The treatment course is typically 7 to 10 days in total.[31] Longer duration of therapy may be required in patients with very high parasitemia or in those with severe or persistent symptoms, although no controlled studies have evaluated prolonged therapy. The treatment duration may also need to be extended to at least 6 weeks in patients who are immunocompromised.[34][31]

Primary options

azithromycin: children: 10 mg/kg intravenously every 24 hours until symptoms abate, followed by 5-10 mg/kg orally once daily, maximum 500 mg/day; adults: 500 mg intravenously every 24 hours until symptoms abate, followed by 250-500 mg orally once daily

More

and

atovaquone: children: 20 mg/kg orally twice daily, maximum 750 mg/dose; adults: 750 mg orally twice daily

Secondary options

clindamycin: children: 7-10 mg/kg intravenously every 6-8 hours until symptoms abate, followed by 7-10 mg/kg orally three to four times daily, maximum 600 mg/dose; adults: 600 mg intravenously every 6 hours until symptoms abate, followed by 600 mg orally three times daily

and

quinine sulfate: children: 8 mg/kg orally three times daily, maximum 650 mg/dose; adults: 650 mg orally three times daily

Consider – supportive care and monitoring

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ACUTE
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acute severe disease
Consider – 

supportive care and monitoring

Treatment recommended for SOME patients in selected patient group

Aggressive supportive care (e.g., vasopressor therapy, mechanical ventilation, dialysis) may be required in some patients.[36]​ Cases of infection with B divergens and B divergens-like species (such as MO-1) are medical emergencies and should be treated as such. Consultation with a critical care and infectious disease specialist is recommended.

Close clinical and laboratory follow-up, including CBC, renal and hepatic function, and peripheral blood smear is essential to ensure clinical improvement, reduction in parasitemia, and improvement in other laboratory abnormalities, such as anemia or renal dysfunction. In immunocompromised patients who experience severe disease, peripheral blood smear should be monitored at least daily until parasitemia is <4%. After this, blood smears should be obtained at least weekly until no parasites are detected. PCR testing should be considered if blood smears have become negative but symptoms persist. There is no standardized approach to monitoring highly immunocompromised patients but close clinical and laboratory follow-up are important.[31] Patients may have persistent low levels of parasitemia for months after completing treatment. 

Consider – exchange transfusion

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ACUTE
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acute severe disease
Consider – 

exchange transfusion

Treatment recommended for SOME patients in selected patient group

Exchange transfusion using red blood cells rapidly decreases parasitemia by replacing parasitized with nonparasitized erythrocytes. It may be considered for patients with high-grade parasitemia (>10%) or those who have any one or more of the following: severe hemolytic anemia and/or severe pulmonary, renal, or hepatic compromise. In cases of life-threatening babesiosis, the potential benefits of exchange transfusion likely outweigh potential risks. Adverse effects include transfusion reactions, worsening of thrombocytopenia, and complications associated with venous access devices. Consultation with a transfusion services physician or hematologist in conjunction with an infectious diseases specialist is recommended.[6]​[31]

Trials of systematic comparisons between antimicrobial therapy alone and antimicrobial therapy plus exchange transfusion have not been published.

Consider – treatment of coinfection

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ACUTE
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acute severe disease
Consider – 

treatment of coinfection

Treatment recommended for SOME patients in selected patient group

Patients with persistent symptoms or with especially severe disease despite appropriate therapy may have coinfection with B burgdorferior A phagocytophilum, or both. Those found to be coinfected should be treated appropriately. Consultation with an infectious disease specialist is recommended.

ONGOING

recurrent or refractory disease

1st line – specialist referral and retreatment

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ONGOING
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recurrent or refractory disease
1st line – 

specialist referral and retreatment

Recurrent or prolonged parasitemia is more frequently seen in immunocompromised people, especially in patients with HIV.[1]

Retreatment with antibabesial therapy, tailored to severity of recurrent disease, may be required if parasites are seen on blood smear or if babesial DNA is detected by polymerase chain reaction >3 months after initial treatment, regardless of symptoms.[34]

Clinical resistance to therapy has been documented in some severely immunocompromised patients who required multiple courses of therapy.[37] In these cases, prolonged therapy has been required for cure.

Consultation with an infectious disease specialist is recommended.

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Please note that formulations/routes and doses may differ between drug names and brands, drug formularies, or locations. Treatment recommendations are specific to patient groups. See disclaimer

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