The anemic and thrombocytopenic febrile neonate.

Background: Babesiosis is a tick-borne, protozoal disease seen primarily in the northeastern and northern Midwest portions of the United States. It is primarily transmitted through the bite of the Ixodes scapularis tick and may cause hemolysis.

Case Report: In the following case report, we present a 4-week-old male neonate with a temperature of 38.8°C (102.0°F) who presented to our pediatric emergency department with anemia, thrombocytopenia, and splenomegaly. Blood smear analysis demonstrated U-shaped parasitic rings within red blood cells consistent with babesiosis, confirmed by a positive Babesia microti antibody screen. Because the patient was never exposed to a vector for babesiosis, and never lived in an endemic area, the most likely exposure was in-utero transmission of the disease through transplacental migration of the parasite prior to birth. The patient was treated with atovaquone and azithromycin and discharged from the hospital after 6 days. The patient's mother also tested positive and was treated with the same medications. The evaluation of a febrile neonate includes a broad differential diagnosis. Although babesiosis is still uncommon in many areas of the United States, a specific constellation of laboratory findings and symptoms should prompt its consideration, even in patients who have not been exposed to an endemic area or a typical vector. Vertical transmission of babesiosis has been previously reported, but the occurrence is quite rare. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Practitioners should include babesiosis in their differential diagnosis where appropriate and be aware that it can be transmitted not only via tick bite, but also from mother to neonate during pregnancy.