Can Babesia Pass From Mother to Baby? Congenital Babesiosis Explained

Babesia can rarely pass from mother to baby during pregnancy
A five-week-old newborn developed severe anemia and feeding difficulty
Prompt diagnosis and treatment led to rapid parasite clearance

Can Babesia pass from mother to baby? Although congenital babesiosis is rare, Babesia parasites can cross the placenta during pregnancy and infect a developing baby. A published case report describes a five-week-old newborn who developed profound anemia, lethargy, pallor, and difficulty feeding due to congenital Babesia microti infection.

Babesiosis is most commonly transmitted through the bite of an infected tick. Less commonly, it can spread through contaminated blood transfusions or from an infected mother to her baby during pregnancy. Although congenital transmission is uncommon, clinicians should consider the diagnosis when a young infant develops otherwise unexplained anemia and thrombocytopenia, particularly if the mother had possible tick exposure during pregnancy.

A five-week-old newborn with congenital babesiosis becomes seriously ill

The patient was born at 36 5/7 weeks’ gestation by cesarean section. At five weeks of age, she presented to the emergency department with pallor, increased lethargy, and difficulty feeding.

Her mother reported that the infant was “more difficult to arouse and very pale compared to her twin brother.” Although feeding occurred with similar frequency, the duration had decreased from approximately 20 minutes to 10 minutes because of fatigue.

On examination, the newborn had a rectal temperature of 100.4°F and appeared markedly pale. She remained vigorous but demonstrated mild tachypnea and tachycardia with heart rates between 170 and 180 beats per minute.

Possible Babesia exposure during pregnancy

The mother reported one febrile illness during pregnancy at approximately 23 to 24 weeks’ gestation. The illness was associated with a maculopapular rash that resolved spontaneously, according to Walker and colleagues.

Throughout her pregnancy, she had also made several trips to Cape Cod, Massachusetts, an area where Babesia microti, Lyme disease, and other tick-borne infections are endemic.

When the newborn became ill, the mother showed no evidence of active babesiosis. Her laboratory testing revealed a Babesia microti IgG antibody titer of 1:160, an IgM of <1:10, and a negative PCR test, findings interpreted by the authors as consistent with a previous infection that had already cleared.

Blood smear reveals Babesia parasites

Laboratory testing in the newborn demonstrated profound anemia, thrombocytopenia, leukocytosis, and elevated liver enzymes.

“Because of the profound hematologic abnormalities, a routine thin smear was obtained, which was significant for multiple intraerythrocytic ringed parasites consistent with Babesia microti,” the authors wrote.

Babesia parasites infect red blood cells. Their destruction can lead to hemolytic anemia and contribute to fatigue, pallor, rapid heart rate, shortness of breath, jaundice, or dark urine, depending on the severity of the infection.

In newborns, babesiosis may present differently than in adults. Because symptoms such as pallor, poor feeding, and lethargy are nonspecific, recognition often depends on identifying unexplained hematologic abnormalities and performing a peripheral blood smear.

PCR testing may also help confirm the diagnosis, although direct visualization of parasites on a peripheral blood smear remains one of the most important diagnostic findings during acute babesiosis.

Treating congenital babesiosis

The newborn received a transfusion of packed red blood cells along with atovaquone twice daily and azithromycin daily. Within five days, Babesia parasites were no longer detected in her blood.

Her twin brother tested negative for Babesia microti, while the mother’s laboratory results showed a Babesia microti IgG titer of 1:160, an IgM of <1:10, and a negative PCR, findings consistent with a resolved maternal infection.

“Although case reports of congenital babesiosis exist, this is the first report describing asymmetric transplacental transmission in twins,” the authors wrote.

The case illustrates that congenital babesiosis may become clinically apparent weeks after birth, even when maternal testing no longer demonstrates active infection.

What is congenital babesiosis?

Congenital babesiosis is a form of congenital transmission, meaning the Babesia parasite passes from an infected mother to her developing baby during pregnancy.

Unlike tick-acquired babesiosis, congenital infection may not become evident immediately after delivery. Published case reports show that affected infants often become ill several weeks later with pallor, poor feeding, lethargy, fever, anemia, thrombocytopenia, or elevated liver enzymes.

Because these symptoms overlap with many neonatal illnesses, congenital babesiosis may not initially be suspected unless clinicians recognize the combination of unexplained hematologic abnormalities together with maternal tick exposure or travel to an endemic area during pregnancy.

When should congenital babesiosis be considered?

Walker and colleagues recommend including tick-borne diseases such as babesiosis in the differential diagnosis of infants with otherwise unexplained anemia, thrombocytopenia, or neutropenia, particularly when the mother lived in or traveled to an endemic area during pregnancy.

Although congenital babesiosis remains rare and this report describes only a single family, it demonstrates that maternal infection may resolve before delivery while the newborn later develops clinically significant disease.

Frequently Asked Questions

Can Babesia be transmitted during pregnancy?

Yes. Although uncommon, published case reports demonstrate that Babesia parasites can cross the placenta and infect a developing baby.

What are the symptoms of congenital babesiosis?

Reported symptoms include pallor, lethargy, poor feeding, fever, rapid breathing, rapid heart rate, anemia, thrombocytopenia, and elevated liver enzymes. Symptoms may not appear until several weeks after birth.

How is congenital babesiosis diagnosed?

Diagnosis typically involves examination of a peripheral blood smear, PCR testing for Babesia DNA, antibody testing, and laboratory evaluation of anemia, platelet counts, and liver function.

Can one twin develop congenital babesiosis while the other does not?

Yes. In this published case report, one twin developed congenital babesiosis while the other twin remained uninfected. The authors described this as asymmetric transplacental transmission.

How is congenital babesiosis treated?

Treatment depends on the infant’s clinical condition and should be directed by experienced pediatric specialists. In this case, the newborn improved after a blood transfusion together with atovaquone and azithromycin.

Can congenital babesiosis be cured?

Published case reports indicate that most newborns recover with prompt diagnosis and appropriate antimicrobial therapy. Early recognition is important because untreated babesiosis can lead to severe hemolytic anemia and other complications.

Clinical Takeaway

Congenital babesiosis is an uncommon but important cause of anemia in young infants. The diagnosis should be considered when a newborn presents with unexplained pallor, lethargy, poor feeding, thrombocytopenia, or hemolytic anemia, particularly if the mother had possible tick exposure or traveled to an area where Babesia microti is endemic during pregnancy.

This case also illustrates an important clinical point: maternal infection may have resolved before delivery, resulting in negative maternal PCR testing by the time the infant becomes ill. A careful maternal travel and exposure history, combined with examination of a peripheral blood smear, may be critical in establishing the diagnosis.

Although congenital babesiosis remains rare, this case demonstrates that transplacental transmission can occur and that prompt recognition and appropriate treatment can lead to an excellent outcome.

Related Articles

Learn more about babesiosis, coinfections, and related tick-borne illnesses:

Babesia Symptoms, Diagnosis, and Treatment
The Case of an Untreated Babesia Infection
Tick-Borne Coinfections: Babesia, Bartonella, and More

References

1. Walker S, Coray E, Ginsberg-Peltz J, Smith L. A Five-Week-Old Twin With Profound Anemia: A Case Report of Asymmetric Congenital Babesiosis. Cureus. 2022;14(3):e22774.

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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