Study Finds 12 U.S. Cases of Transfusion-Transmitted Ehrlichiosis and Anaplasmosis Between 1997 and 2020

October 26, 2021

Research published recently in Emerging Infectious Diseases found 12 documented cases of transfusion-transmitted ehrlichiosis or anaplasmosis in the United States since 1997. Ehrlichiosis and anaplasmosis are emerging tick-borne diseases caused by Ehrlichia and Anaplasma spp. obligate intracellular bacteria, but transmission can also occur through blood transfusion or solid organ transplantation.

As part of this study, researchers reviewed published literature and reports from six Centers for Disease Control and Prevention (CDC) investigations for ehrlichiosis and anaplasmosis cases among transfusion and solid organ transplant recipients. Of the 12 transfusion-transmitted cases, eight resulted from transfused red blood cell components while three were from transfused platelet components (two apheresis and one whole blood–derived); the component for one case was not identified. The authors noted that while leukoreduction has been presumed to reduce risk for ehrlichiosis and anaplasmosis through passive removal, 83% (10/12) of components implicated in transfusion-transmitted cases in this study were leukoreduced.

Ten (83.3%) of 12 transfusion-associated cases were A. phagocytophilum infections. One case was associated with E. ewingii and one was associated with E. chaffeensis. Eighty-three percent of patients survived their infections, and one-third of cases were associated with mild symptoms. Intensive care unit treatment was noted for two anaplasmosis patients. Three anaplasmosis patients had multisystem organ failure. Two patients died, one from anaplasmosis and the other from other medical complications.

The authors noted that known cases of transfusion- and transplant-transmitted ehrlichiosis or anaplasmosis are uncommon, but studies of asymptomatic infection among blood donors and the survivability of infection in blood suggest the risk of transmission is greater than previously recognized. Furthermore, they believe that donor-derived ehrlichiosis and anaplasmosis highlight the importance of donor risk mitigation strategies in the setting of blood transfusion and solid organ transplantation and the potential role of laboratory-based screening. “Because the prevalence of tick-borne disease infections is rising, additional risk mitigation interventions will likely be necessary to enhance blood and organ safety,” they concluded.