Congenital Babesiosis: Transmission Risk in Infants of Mothers with Lyme
Can Babesia be passed from mother to infant during pregnancy?
Congenital babesiosis is rare but clinically significant. Two infants born to mothers with Lyme disease during pregnancy developed Babesia infections, highlighting the risk of unrecognized coinfection.
These represent the first reported cases in which mothers had prepartum Lyme disease with subclinical Babesia microti infection.
Congenital transmission has been described in at least seven prior cases, typically presenting with fever, anemia, and thrombocytopenia, according to Saetre.
Infant #1
A 4½-week-old male presented with fever, sleepiness, and irritability.
His mother had been diagnosed with Lyme disease at 32 weeks’ gestation after developing an erythema migrans rash and was treated with amoxicillin.
The infant’s blood smear revealed 2% parasitemia for Babesia.
He was treated with atovaquone and azithromycin, which are often better tolerated in infants than clindamycin and quinine.
The infant did not require transfusion and recovered fully.
Infant #2
The second infant’s mother developed fever and myalgias at 35 weeks, followed by an erythema migrans rash at 37 weeks.
The infant was initially asymptomatic despite a positive PCR for B. microti, but developed anemia and neutropenia one week later.
She required hospitalization, treatment with azithromycin and atovaquone, and ultimately a blood transfusion due to symptomatic anemia.
Clindamycin was added due to persistent parasitemia, and treatment was extended to 14 days.
Treatment Considerations
Both infants were treated longer than the 7–10 day duration recommended in guidelines due to concerns about impaired parasite clearance in neonates.
These cases resemble prior reports in which infants presented between 19 and 41 days of age with fever, anemia, thrombocytopenia, and often neutropenia.
Coinfection Risk in Pregnancy
The risk of Babesia coinfection in Lyme disease is significant.
Depending on geographic region, 2% to 40% of patients with early Lyme disease may be coinfected with Babesia.
Tick studies in Westchester County, New York, have identified coinfection rates of up to 22.4%.
Clinical Questions Raised
- Can Babesia infection earlier in pregnancy affect fetal outcomes?
- Would Babesia be recognized without classic Lyme features such as erythema migrans?
- Could earlier treatment have prevented complications in the second infant?
- Should treatment during pregnancy address both Lyme disease and Babesia?
Clinical Perspective
These cases highlight the importance of considering Babesia coinfection in pregnant patients diagnosed with Lyme disease.
Subclinical maternal infection may still result in neonatal disease.
Early recognition and individualized treatment may reduce complications in affected infants.
Clinical Takeaway
Congenital babesiosis can occur in infants born to mothers with Lyme disease and unrecognized Babesia infection. Coinfection should be considered in pregnancy, particularly in endemic regions.
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
