Consider Babesiosis in Transfused Infants With Liver Problems
PHILADELPHIA — A single split unit of infected blood was the source of Babesia microti infections in four very-low-birth-weight babies in Rhode Island, Dr. Kari Simonsen reported at the annual meeting of the Eastern Society for Pediatric Research.
The first case was seen in an acutely ill 35-day-old infant born at 25 weeks' gestation. The other three cases were identified after a search for other recipients of the suspect blood. None of these infants was seriously ill. Unlike the index case, who had a parasitemia level of 17%, the other three infants had low levels of parasitemia, said Dr. Simonsen, a pediatric infectious disease fellow at Brown University, Providence, R.I.
B. microti is an erythrocytic parasite similar to Plasmodium—the cause of malaria. The parasite is transmitted via tick bite to a human. It is endemic in the Northeast and upper Midwest of the United States, where up to 10% of the population is infected, Dr. Simonsen said.
Blood banks do not routinely screen for the parasite in donations, despite the prevalence of infections in some regions. “Up to 1.4% of blood donated in hyperendemic regions is seropositive and up to 53% [of the seropositive blood] is positive by [polymerase chain reaction],” she said.
The index infant weighed 760 g at birth, and on day 2 received a transfusion for anemia. On day 35, the infant developed worsening apnea, respiratory distress requiring reintubation, fever, edema, hepatosplenomegaly, hemolytic anemic, and thrombocytopenia.
The initial workup, which was unrevealing, included blood, urine, and cerebrospinal fluid cultures, and viral studies. The patient was managed with ampicillin, gentamicin, and amphotericin B.
When the infant was 50 days old, a blood smear was done; a laboratory technician noted the typical intraerythrocytic “Maltese cross” formation of the Babesia parasite, with 17% of the red blood cells parasitized. “The infant immediately received a double-volume exchange transfusion, and clindamycin and quinine were started,” Dr. Simonsen said.
By treatment day 6, the infant still had a parasitemia of about 6%. Another double volume exchange transfusion was performed; azithromycin and atovaquone were added to the existing medical therapy. By day 9, the parasitemia had decreased to 0.09%, and quinine was discontinued. A week later, the infant's blood smear was negative, but parasitemia increased to 0.03% on day 20. “This patient experienced a long period of low, but not absent, parasitemia,” Dr. Simonsen said. Medical therapy was continued until two consecutive negative smears were obtained (days 24 and 27). On day 28, antibiotics were discontinued.
A blood bank investigation identified three additional infants who had received transfusions from the same unit of blood, all of whom were asymptomatic or mildly symptomatic. Case 2 had only a single organism on blood smear, and was managed with clindamycin and quinine. The smear was negative after just 1 day of treatment. Case 3 had a parasitemia of 0.9%, received clindamycin and quinine, and had a negative smear after 14 days. The final case had a parasitemia of 1.5%, and also was negative after 14 days of clindamycin and quinine.
Epidemiologists could find no reason for the large load in the index case, Dr. Simonsen said. “That infant did not receive a larger share of the blood than our other cases.”
Dr. Peter J. Krause, director of the division of infectious diseases in the department of pediatrics at the University of Connecticut, Farmington, commented on the identification of infants with suspected babesiosis.
“It's probably not worth a routine smear, but if you have a neonate who has been transfused and is not doing well, with increasing liver enzymes or splenomegaly, it might be something to order.” The incubation period in transfusion-related cases is typically 6–9 weeks, he said at the meeting.
Up to 1.4% of blood donated in hyperendemic regions (such as the Northeast U.S.)is seropositive. DR. SIMONSEN
