Persistence of babesiosis for >2 years in a patient on rituximab for rheumatoid arthritis

We report a patient who was being treated with rituximab for rheumatoid arthritis who developed Babesia microti infection that persisted for 26 months despite prolonged anti-babesia drug therapy. The explanation for the persistence was likely to have been the long-term immunocompromising effects of rituximab, as evidenced by seronegativity for B. microti antibodies that lasted for more than 1 year after onset of infection.