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J Clin Microbiol. 2016 November; 54(11): 2842.
Published online 2016 October 24. doi:  10.1128/JCM.01022-16
PMCID: PMC5078567

Closing the Brief Case: Probable Transfusion-Transmitted Babesiosis in a Transplant Recipient

C.-A. D. Burnham, Editor
Washington University School of Medicine


  1. What is the median incubation period for transfusion-transmitted babesiosis (time from transfusion to symptoms)?
    • (a)
      7 days
    • (b)
      18 days
    • (c)
      37 days
    • (d)
      83 days

Answer: c. Thirty-seven days is the median time from transfusion to onset of symptoms (if symptoms appear) reported in the literature, with a range from 11 to 176 days.

  1. What is the primary vector for Babesia in the United States, and what other pathogen can it transmit?
    • (a)
      Ixodes scapularis, Borrelia burgdorferi
    • (b)
      Dermacentor variabilis, Rickettsia rickettsii
    • (c)
      Amblyomma americanum, Ehrlichia chaffeensis
    • (d)
      Ornithodoros hermsi, Borrelia recurrentis

Answer: a. Ixodes scapularis can also transmit Borrelia burgdorferi, the causative agent of Lyme disease. The other tick species listed are matched with appropriate infectious agents, but they do not transmit Babesia spp.

  1. What is the gold standard test method for definitive diagnosis of Babesia infection?
    • (a)
      Hamster inoculation
    • (b)
      Real-time PCR
    • (c)
      Giemsa-stained blood smear
    • (d)
      IgG/IgM antibody detection by indirect immunofluorescence

Answer: c. Giemsa-stained blood smears remain the gold standard for diagnosis. Real-time PCR is the most sensitive and specific diagnostic test, but there are no FDA-cleared tests commercially available. Antibody detection and titer by IFA analysis is available through reference laboratories and may be helpful in certain situations but is not recommended for primary diagnosis. Inoculation of a hamster (or other small rodent) is widely reported for detection of Babesia spp. directly from patient blood samples but is not practical for clinical laboratories.


  • Currently, the U.S. blood supply is not directly screened for the presence of Babesia spp. Therefore, babesiosis should be considered in individuals with the appropriate clinical symptoms who have received a blood transfusion within the last several months (perhaps up to 6 months), regardless of the time of year or geographic area.
  • Routine testing for Babesia spp. is done in the same manner as testing for Plasmodium spp., i.e., by Giemsa-stained blood smear. There is a high degree of morphological similarity between these organisms; thus, thorough technologist training and careful slide reading are required for accurate interpretation. Molecular testing is available at reference laboratories but might be best used in Giemsa-stained blood smear-negative cases with a high index of suspicion for babesiosis or in cases where infection with Babesia spp. versus Plasmodium spp. cannot be differentiated.
  • The geographic area of endemicity of Babesia spp. overlaps that of the infectious agent of Lyme disease, Borrelia burgdorferi, and both are transmitted by the same vector, Ixodes scapularis. Dual infections have been reported in areas of endemicity.

(See page 2632 in this issue [doi:10.1128/JCM.00981-16] for case presentation and discussion.)

Articles from Journal of Clinical Microbiology are provided here courtesy of American Society for Microbiology (ASM)