Relapsing Babesiosis: When Standard Treatment Fails

Immunocompromised patient with recurrent symptoms
Multiple treatment failures over several months
Sustained recovery achieved with combination therapy including Malarone

This case report highlights a critical challenge: immunocompromised patients with Babesia may not respond to standard antimicrobial therapy, leading to relapsing infection.

In their article, “Atovaquone-Proguanil: A Promising Therapy for Persistent Relapsing Babesiosis,” Shahid and colleagues describe a case successfully treated with a Malarone-based regimen.

Case Report: Relapsing Babesiosis

A 73-year-old man with a history of chronic lymphocytic leukemia (CLL) in remission presented with generalized weakness and fatigue. Laboratory testing revealed unexplained anemia.

Weeks later, he developed confusion and falls, prompting evaluation by hematology. He was treated with prednisone, intravenous immunoglobulin (IVIG), and rituximab for suspected CLL-related complications or viral illness, with only partial improvement.

Notably, the patient did not recall a tick bite. However, he had received multiple blood transfusions and had recently traveled to Long Island, New York—both recognized risk factors for Babesia exposure, as discussed in our Babesia transmission guide.

Eventually, testing confirmed Babesia microti infection. Peripheral smear and bone marrow findings supported the diagnosis.

Multiple Treatment Failures

The patient was initially treated with atovaquone and azithromycin for 4 weeks. Eight weeks later, symptoms recurred.

A second regimen of azithromycin, atovaquone, and clindamycin was administered for 8 weeks. However, relapse occurred again, with persistent parasitemia on peripheral smear.

These repeated failures highlight the complexity of Babesia management, particularly in immunocompromised individuals and in the context of tick-borne coinfections.

Treatment Success with Malarone Combination

Therapy was then adjusted to include atovaquone-proguanil (Malarone), azithromycin, and clindamycin.

Following this regimen, the patient showed sustained improvement. Over the next year, follow-up peripheral smears remained negative for Babesia.

The authors concluded that Malarone may serve as an effective salvage therapy in cases of antimicrobial resistance or treatment failure.

Why This Matters

Relapsing babesiosis can be difficult to treat, particularly in immunocompromised patients. Standard regimens may not always be sufficient, requiring alternative or combination therapies.

These challenges mirror broader patterns seen in complicated Babesia presentations, where symptoms and treatment responses vary widely.

Clinicians should consider alternative regimens and close follow-up in patients with persistent or relapsing babesiosis.

Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.

Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention