Congenital babesiosis in China: first molecularly confirmed case of vertical transmission of Babesia microti

Congenital babesiosis is rarely reported globally. We report a 74-day-old male infant presented with fever, pallor, and severe, life-threatening haemolytic anaemia (haemoglobin: 45 g/L). The infant had 16% parasitemia with ring forms evident on peripheral blood smear. Babesia microti infection was confirmed in both the mother and infant by PCR and metagenomic next- generation sequencing. Genetic analysis revealed an identical strain in bot. Treatment with intravenous azithromycin and oral atovaquone/proguanil resulted in rapid clearance of parasitemia and resolution of anaemia. This first molecularly confirmed case of congenital B. microti transmission in China demonstrates vertical transmission from an asymptomatic mother. It underscores the need for heightened clinical suspicion in neonates with unexplained haemolytic anaemia in endemic regions and highlights critical gaps in access to essential anti-babesia therapies.