Probable Congenital Babesiosis in Infant, New Jersey, USA

Sonia Sethi; David Alcid; Hemant Kesarwala; Robert W. Tolan, Jr.


Emerging Infectious Diseases. 2009;15(5) 

In This Article

The Case

A 26-day-old, 8-pound, full-term infant girl was transferred to Saint Peter's University Hospital for evaluation of fever and hyperbilirubinemia. For 1 week, she was not feeding well and was gagging and irritable. On the day of admission, her mother noted fever and yellow eyes. The mother (a migrant crop worker) reported having had an uneventful pregnancy, labor, and delivery, except for having been bitten by 2 ticks at 8 months' gestation while picking crops in New Jersey. She did not seek treatment. The mother had not traveled elsewhere in the United States during her pregnancy. Knowledge about earlier travel to Babesia-endemic areas would have been helpful in understanding the mother's infection, but this information was unavailable. The infant had no history of tick exposure; she had been outdoors only for visits to the pediatrician.

Physical examination showed an alert but pale infant weighing 4.4 kg; her temperature was 101.8°F (38.7°C), pulse rate 160/min, respiratory rate 36/min, blood pressure 90/40 mm Hg, and oxygen saturation 99% while breathing room air. Her conjunctivae were icteric. Her liver and spleen were palpable 4 cm and 5 cm below their respective costal margins. No hemorrhagic lesions or tick bites were noted. The rest of her physical examination findings were unremarkable except for a diaper rash.

Initial laboratory findings included a hemoglobin level of 8.8 g/dL (indices within normal limits); leukocyte count of 9.0/mm3 with 3% bands, 18% neutrophils, 72% lymphocytes, 7% monocytes; and platelet count of 34,000/mm.3 Blood chemistry concentrations included total and indirect bilirubin 5.9 mg/dL (reference range 0.1–1.2 mg/dL); alanine aminotransferase 18 IU/L; aspartate aminotransferase 53 IU/L; alkaline phosphatase 108 IU/L; blood urea nitrogen 6 mg/dL; creatinine 0.3 mg/dL; and C-reactive protein 54 mg/dL (reference range 1.0–10.0 mg/dL). Peripheral blood smear demonstrated evidence of hemolysis and was consistent with Babesia microti infection (although B. duncani is indistinguishable from B. microti on peripheral smear) and ≈15% parasitemia (Figure).


Giemsa-stained (A) and Wright-stained (B) peripheral blood smear from a newborn with probable Babesia microti infection. Parasitemia was estimated in this newborn at ≈15% based on the number of parasites per 200 leukocytes counted. The smear demonstrated thrombocytopenia and parasites of variable size and morphologic appearance and an absence of pigment. Magnification ×1,000

Subsequently, the infant's lactate dehydrogenase concentration was found to be 1,912 IU/L (reference range 313–618 IU/L) and later rose to 2,535 IU/L (Table 1). The infant's Babesia immunoglobulin (Ig) G and IgM titers by immunofluorescent antibody (IFA), which are genus specific but not species specific, were 256 (reference <16) and 40 (reference <20), respectively (both tests were performed by Quest Diagnostics–Nichols Institute, Chantilly, VA, USA). Lyme IgG Western blot plus 2 Lyme IgM Western blots, performed early during hospitalization and just before discharge, were negative. The mother's peripheral blood smear did not show any parasites, but her Babesia IgG and IgM titers by IFA were >1,024 and 80, respectively, and her Lyme serology was positive. The mother refused additional testing. Despite the variability in sensitivity and specificity of commercially available serologic tests (particularly the IFA for Babesia IgM), Babesia serologic results were not confirmed at a reference laboratory. Species-specific PCR was not performed.

After concluding that this infant had probable congenital babesiosis, we began treating her with oral atovaquone (40 mg/kg/d) in 2 divided doses and azithromycin (12 mg/kg/d) once per day. The infant received 1 transfusion with packed red blood cells on hospital day 3 because of continued hemolysis, but she did not require exchange transfusion despite having a high initial parasite count. The infant's parasitemia decreased rapidly, and she responded well to treatment (Table 1). She was discharged after 8 days and was to complete a 10-day course of atovaquone and azithromycin (which were well tolerated); she was subsequently lost to follow-up.


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.
Post as: