Neoehrlichia mikurensis and Borrelia miyamotoi co-infection in an immunocompromised patient.

BACKGROUND: Neoehrlichia mikurensis and Borrelia miyamotoi are emerging tick-borne pathogens that primarily cause disease in immunocompromised individuals. Human co-infection with both pathogens has not previously been reported. CASE PRESENTATION: A 55-year-old man receiving rituximab for primary progressive multiple sclerosis developed persistent fever, fatigue, malaise, and neck pain following a tick bite on Bornholm, Denmark. Multiple erythema migrans resolved after phenoxymethylpenicillin treatment, but systemic symptoms persisted. Borrelia burgdorferi serology was negative. Owing to ongoing symptoms and B-cell depletion, blood was analysed by 16S rRNA sequencing and species-specific PCR. Both B. miyamotoi and N. mikurensis DNA were detected and confirmed by independent laboratories. Treatment with doxycycline resulted in rapid clinical improvement and complete recovery. CONCLUSION: To our knowledge, this is the first reported human co-infection with B. miyamotoi and N. mikurensis. The case highlights the importance of molecular diagnostics for emerging tick-borne infections in patients receiving anti-CD20 therapy.