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177 Babesia microti Infection in Renal Transplant Recipients

Friday, March 19, 2010
Grand Hall (Hyatt Regency Atlanta)
Meghan B. Brennan, MD , University of Wisconsin School of Medicine and Public Health, Madison, WI
Christina L. Klein, MD , Washington University, St Louis, MO
Debra M. Thompson, MD , Affiliated Infectious Disease Consultants, Milwaukee, WI
James J. Kazmierczak, DVM, MS , Wisconsin Department of Health Services, Madison, WI
Rong He, MD , University of Wisconsin School of Medicine and Public Health, Madison, WI
Catherine Leith, MD , University of Wisconsin School of Medicine and Public Health, Madison, WI
Matthew Oberley, MD, PhD , University of Wisconsin School of Medicine and Public Health, Madison, WI
Mitchell D. Wolf, MD , University of Wisconsin School of Medicine and Public Health, Madison, WI
Patricia P. Wilkins, PhD , CDC, Division of Parasitic Diseases, Atlanta, GA
Barbara L. Herwaldt, MD, MPH , CDC, Division of Parasitic Diseases, Atlanta, GA
Gregory M. Gauthier, MD , University of Wisconsin School of Medicine and Public Health, Madison, WI
Background: Babesia microti, an intraerythrocytic parasite, is the most common cause of babesiosis in the United States and is endemic in parts of the Northeast and upper Midwest.  This zoonotic pathogen is usually acquired through the bite of an Ixodes scapularis tick; however, transmission by blood transfusion has been reported. 

Objective: We describe two cases of laboratory-confirmed babesiosis in which transmission of B. microti likely occurred at the time of kidney transplantation.  To our knowledge, transmission of Babesia by (or during) transplantation has not been reported. 

Methods:   Evaluations for Babesia infection included blood-smear examination, immunofluorescent antibody (IFA) testing of serum/plasma for B. microti antibodies, and polymerase chain reaction (PCR) analysis of blood for B. microti DNA.

Results:   In late October 2008, two transplant recipients developed hemolytic anemia within eight weeks of receiving cadaveric renal allografts from the same donor.  The index case-patient was diagnosed with babesiosis (8% parasitemia) by manual review of a peripheral blood smear during an inpatient evaluation for pancytopenia.  The recipient of the other kidney was identified and also found to have babesiosis (1% parasitemia).  For both patients, PCR and IFA testing of post-transplant specimens documented that the etiologic agent was B. microti; no B. microti antibodies were detected in archived pretransplant specimens.  Neither patient had risk factors for tick exposure or received blood products in the peritransplant period.  Both patients were treated for six weeks with atovaquone and azithromycin, which resulted in the resolution of symptoms, hemolytic anemia, and parasitemia.  Ten months after completion of therapy, they remain asymptomatic.    

Conclusions: These two cases highlight the potential for transmission of B. microti at the time of organ transplantation.  The diagnosis of babesiosis should be considered in patients who develop unexplained hemolytic anemia after solid organ transplantation.