Congenital Babesiosis in a Four-Week-Old Female Infant

Abstract

To the Editors: Babesia, a tick-borne intraerythrocytic protozoa, is most commonly acquired after exposure to the Ixodes scapularis tick, or less commonly, via blood transfusion.1 In neonates, the course of illness ranges from mild to severe disease, requiring hospitalization, antibiotics, and blood transfusion.2 Only 3 cases of congenital babesiosis and 8 cases of acquired neonatal babesiosis (associated with blood transfusion or tick bite) have thus far been reported.2–6 In 2006, Fox et al2 reported a case of transfusion-associated neonatal babesiosis and reviewed 9 other cases, including 5 transfusion-associated cases. Of these 5 babies, 4 were preterm infants who received blood transfusions for anemia of prematurity. The other cases included 2 congenital3,4 cases and 2 tick transmitted cases.5 Recently there was a probable case of congenital babesiosis in a neonate with 15% parasitemia requiring blood transfusion.6 None of these 11 cases required exchange blood transfusion. Although all reported cases did well once identified and treated, this illness is potentially fatal if not identified. We evaluated a full term 4-week-old baby with a 1-day history of fever to 38.8°C. There was no history of tick bites and no history of maternal blood transfusion. Physical examination revealed fever and mild pallor. A complete blood count revealed anemia (hematocrit 24.3%). Her platelet count was clumped, which triggered doing a peripheral blood smear, revealing intraerythrocytic parasites, identified as Babesia microti. The parasite count was 2% and liver function tests were mildly elevated. Repeat platelet count was 101 × 103/mm3. She had been initially started on IV ampicillin and cefotaxime for presumed sepsis. Once the parasites were identified, the antibiotics were switched to oral atovaquone (40 mg/kg/d divided q 12 hours) and azithromycin (10 mg/kg/d). She subsequently defervesced and the parasite count decreased to 0.2%. Anemia worsened over 2 days (hematocrit 17.3%), requiring readmission for a red blood cell transfusion. The mother's serum Babesia polymerase chain reaction (PCR) was positive. At that time, she had a normal CBC, was asymptomatic, and therefore was not treated. Most cases of babesiosis in the United States are endemic to the Northeastern states, the majority occurring in adults. There have been few reported cases of neonatal babesiosis, perhaps related to a lack of recognition or severity of this infection in this age group. The advent of newer molecular diagnostic tools, such as Babesia PCR, may herald increased identification of cases of neonatal babesiosis. Recommended treatments for babesiosis include clindamycin and quinine; or azithromycin and atovaquone for 7 to 10 days; the latter combination is more effective in adults and has fewer adverse effects.2,4 The safety and efficacy of these combinations have not been evaluated in infants, but atovaquone and azithromycin therapy is well tolerated in HIV infected children.7 Exchange blood transfusion may be potentially life saving in patients with severe disease, high parasitemia (>10%), significant hemolysis, renal or pulmonary involvement, findings rarely present in reported infections in infants. It is important that physicians keep babesiosis in mind as a differential diagnosis of fever in neonates in endemic areas, especially if infants present with hemolytic anemia with or without thrombocytopenia. Omolara Aderinboye, MD Salma S. Syed, DO Division of Infectious Diseases, Department of Pediatrics, SUNY at Stony Brook Stony Brook, NY