Babesiosis

Overview 
Theory 
Diagnosis 
Management 
Follow up 
Resources 

Management options in patients with a confirmed diagnosis include observation and monitoring, oral or parenteral antimicrobials, and/or exchange transfusion depending on disease severity. The goal of treatment is to reduce symptoms of disease and to eliminate parasitaemia while preventing complications of disease. Current treatment recommendations presented here are for Babesia microti.

Asymptomatic patients

Observation is sufficient in asymptomatic patients. 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]

Symptomatic patients: mild to moderate disease

These patients are generally immunocompetent, experience mild to moderate symptoms, have a parasitaemia <4%, and are ambulatory and do not require hospital admission.[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 parasitaemia and symptoms have failed to abate following initiation of atovaquone plus azithromycin.[6] [31]

The 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 parasitaemia 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 parasitaemia may persist for weeks or months after treatment. Further monitoring and treatment are rarely needed in these patients as relapse rarely occurs.[6][31]

Monitoring parasitaemia during treatment of acute illness using peripheral blood smears is recommended; however, testing is not recommended once symptoms have resolved.[31]

Symptomatic patients: acute severe disease

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 parasitaemia 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 some countries.[6][31]

Worsening of symptoms or increasing parasitaemia 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 parasitaemia 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.[6][31][34]

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.

Exchange transfusion using red blood cells rapidly decreases parasitaemia by replacing parasitised with non-parasitised erythrocytes. It may be considered for patients with high-grade parasitaemia (>10%) or those who have any one or more of the following: severe haemolytic anaemia 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 thrombocytopaenia, and complications associated with venous access devices. Consultation with a transfusion services physician or haematologist 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.

Close clinical and laboratory follow-up, including FBC, renal and hepatic function, and peripheral blood smear is essential to ensure clinical improvement, reduction in parasitaemia, and improvement in other laboratory abnormalities, such as anaemia or renal dysfunction. In immunocompromised patients who experience severe disease, peripheral blood smear should be monitored at least daily until parasitaemia 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 standardised approach to monitoring highly immunocompromised patients but close clinical and laboratory follow-up are important.[31] Patients may have persistent low levels of parasitaemia for months after completing treatment.

Patients with persistent symptoms or with especially severe disease despite appropriate therapy may have co-infection with Borrelia burgdorferi or Anaplasma phagocytophilum, or both. Those found to be co-infected should be treated appropriately. An underlying immunodeficiency should also be excluded in patients with severe or prolonged disease despite appropriate therapy. Consultation with an infectious disease specialist is recommended.

Recurrent or refractory disease

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

Peripheral blood smears and/or PCR should be performed if symptoms recur.[31]

Re-treatment with anti-babesial therapy, tailored to the severity of recurrent disease, may be required if parasites are seen on blood smear or if babesial DNA is detected by PCR more than 3 months after initial treatment, regardless of symptoms.[34] Consultation with an infectious disease specialist is recommended.

Alternative antibiotic options used for refractory disease in immunocompromised patients include:[31]

Atovaquone plus azithromycin plus clindamycin
Atovaquone plus clindamycin
Atovaquone/proguanil plus azithromycin
Atovaquone plus azithromycin plus clindamycin plus quinine.

However, these regimens have limited evidence of efficacy

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.

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