Case Report: Overwhelming Babesia Parasitemia Successfully Treated Promptly With RBC Apheresis and Triple Therapy With Clindamycin, Azithromycin, and Atovaquone

Relapsing Babesiosis With Molecular Evidence of Resistance to Certain Antimicrobials Commonly Used to Treat Babesia microti Infections

Human babesiosis cases are emerging with an increased incidence and a wider geographic range worldwide. Relapsing babesiosis cases are becoming more frequently encountered in clinical practice associated with the use of immunosuppressive medications. The 2020 Infectious Diseases Society of America babesiosis guideline recommends at least 6 weeks of antimicrobial treatment for highly immunocompromised patients with Babesia microti infection. Nevertheless, cases have relapsed even after 6 weeks of treatment. Genetic mutations regarded as the potential cause of antimicrobial resistance in B microti have been identified in certain relapsing cases. A few alternative antimicrobial regimens have been used successfully to achieve cure for some of these cases, but other cases have had fatal outcomes. In this review, we discuss the molecular evidence of genetic resistance to certain antimicrobials commonly used to treat B microti infections based on an evaluation of 9 patients with relapsing infection.

Human Babesiosis

Babesiosis is caused by intraerythrocytic parasites that are transmitted primarily by ticks, infrequently through blood transfusion, and rarely through transplacental transmission or organ transplantation. Human babesiosis is found throughout the world, but the incidence is highest in the Northeast and upper Midwestern United States. Babesiosis has clinical features that resemble malaria and can be fatal in immunocompromised and older patients. Diagnosis is confirmed by identification of Babesia parasites on blood smear or Babesia DNA with polymerase chain reaction. Standard treatment consists of atovaquone and azithromycin or clindamycin and quinine for 7 to 10 days.

Treatment of Human Babesiosis: Then and Now

Babesiosis is an emerging tick-borne disease caused by apicomplexan parasites of the genus Babesia. With its increasing incidence worldwide and the risk of human-to-human transmission through blood transfusion, babesiosis is becoming a rising public health concern. The current arsenal for the treatment of human babesiosis is limited and consists of combinations of atovaquone and azithromycin or clindamycin and quinine. These combination therapies were not designed based on biological criteria unique to Babesia parasites, but were rather repurposed based on their well-established efficacy against other apicomplexan parasites. However, these compounds are associated with mild or severe adverse events and a rapid emergence of drug resistance, thus highlighting the need for new therapeutic strategies that are specifically tailored to Babesia parasites. Herein, we review ongoing babesiosis therapeutic and management strategies and their limitations, and further review current efforts to develop new, effective, and safer therapies for the treatment of this disease.

Red Cell Exchange as Adjunctive Therapy for Babesiosis: Is it Really Effective?

Human babesiosis is a parasitic disease prevalent in the Northeastern and Midwestern United States (US). Treatment with antibiotics is the standard of care but red cell exchange (RCE) has been used as an adjunctive treatment in more severe disease. Data for the efficacy of RCE in the treatment of babesiosis has been based on case reports and case series. An English language literature search was conducted for cases of babesiosis treated with RCE since 1980 and relevant laboratory and clinical outcome data were extracted. Similar data were obtained on severe cases of babesiosis referred for RCE in our hospitals in the time period 2000 to 2020. Fifty reports including forty-one individual case reports and nine case series were retrieved. There were 108 patients that underwent RCE with an overall mortality rate of 20%. Some patients had more than one RCE. The patients varied in the level of anemia and evidence of compromise of renal or pulmonary function. The pre-RCE level of parasitemia varied between 1.7% to 85% with the vast majority >10%. The post-RCE level of parasitemia varied between 1% to 10%. Since 2000, 32 patients were referred for RCE in our hospitals and RCE was performed on 23 of 32. There were more patients treated with RCE in the second decade as compared to the first decade, 19 versus 4 respectively. The overall mortality was 22% similar to the national data. Comparing the cohort treated with RCE to the 9 patients who were treated only with antibiotics, there were similar levels of parasitemia and laboratory parameters. The overall number of days needed to achieve a parasite count <1% was similar between the two cohorts and mortality for the antibiotics only cohort was 0%. More than 40 years after the first reported case of RCE in severe babesiosis it cannot be concluded that this adjunctive therapy favorably influences the clinical outcome. Since there is largely equipoise, a registry of severe patients treated with or without RCE could identify a benefit or otherwise.