title: Demonstrable parasitemia among Connecticut blood donors with antibodies to Babesia microti.
abstract: BACKGROUND
  Reports of transfusion-transmitted Babesia microti have risen steadily during the past several years, reflecting a concurrent increase in US cases of human babesiosis. Although several studies have measured B. microti antibodies in blood donors, little is known about associated parasitemia and the inherent risk of transmitting the parasite by transfusion.
  
  
  METHODS
  Donations from blood donors located in Babesia-endemic and nonendemic areas of Connecticut were tested for B. microti antibodies from July through September. Subsequently, an additional blood sample was collected from selected seropositive donors and tested by nested polymerase chain reaction (PCR) for B. microti nucleic acids.
  
  
  RESULTS
  A total of 3490 donations, 1745 each from endemic and nonendemic areas, were tested for B. microti antibodies; 30 (0.9%) were confirmed as positive and seroprevalence rates peaked in July. Significantly more seropositive donations were from endemic areas (24, 1.4%) than nonendemic areas (6, 0.3%). Ten (53%) of 19 seropositive donors subsequently tested by PCR were positive.
  
  
  CONCLUSIONS
  B. microti seroprevalence was highest in those areas of Connecticut where the parasite is endemic. More than half of seropositive donors tested had demonstrable parasitemia, indicating that many are at risk for transmitting B. microti by blood transfusion. Three donors were identified as parasitemic in October, suggesting that donors may be at risk for transmitting the parasite outside of the peak period of community-acquired infection.
authors.affiliation: Department of Transmissible Diseases, American Red Cross, Rockville, MD 20855, USA. leiby@usa.redcross.org
authors.forename: David A
authors.initials: DA
authors.lastname: Leiby
authors.forename: Amy P S
authors.initials: AP
authors.lastname: Chung
authors.forename: Jennifer E
authors.initials: JE
authors.lastname: Gill
authors.forename: Raymond L
authors.initials: RL
authors.lastname: Houghton
authors.forename: David H
authors.initials: DH
authors.lastname: Persing
authors.forename: Stanley
authors.initials: S
authors.lastname: Badon
authors.forename: Ritchard G
authors.initials: RG
authors.lastname: Cable
mesh_terms: D000913:Antibodies, Protozoan / Q000097:blood*; D041001:Babesia microti / Q000276:immunology*; D001404:Babesiosis / Q000175:diagnosis / Q000453:epidemiology; D001782:Blood Donors / Q000706:statistics & numerical data*; D003237:Connecticut / Q000453:epidemiology; D016054:DNA, Protozoan / Q000097:blood; D003710:Demography; D019353:Endemic Diseases; D005500:Follow-Up Studies; D006801:Humans; D008403:Mass Screening; D018512:Parasitemia / Q000175:diagnosis / Q000453:epidemiology*; D016133:Polymerase Chain Reaction; D016036:Seroepidemiologic Studies
chemical_list: D000913:Antibodies, Protozoan; D016054:DNA, Protozoan