The impact of babesiosis on transfusion medicine.

Babesiosis is an emerging zoonotic disease that has begun to have a noticeable impact on transfusion medicine. This is reflected in the growing medical literature on the topic. There has been no review to summarize the various ways in which babesiosis influences transfusion medicine. Babesiosis is the most frequently reported tick-borne pathogen to be transmitted by blood transmission. Until recently, it has been an underrecognized complication of blood transfusion. However, the increased use of blood products for an ever-increasing elderly and immunodeficient patient population has heightened awareness about this disease. Fortunately, the risk of acquiring a symptomatic infection through a blood transfusion is surprisingly low. Nevertheless, babesiosis should be included in the differential diagnosis of a febrile hemolytic illness in recipients of blood transfusions. Infected individuals who become chronic carriers and donate blood during asymptomatic periods pose the greatest risk to the blood supply. The exact risk that this parasite poses to our blood supply remains to be accurately assessed. Reported cases of transmission, to date, have involved only the transfusion of red blood cells (RBCs) and, more rarely, platelets. Transmission of these piroplasms through plasma alone has not been documented. Much of our understanding about this organism evoked host responses and its requirements for in vitro survival has come from studies on non-human vertebrates. These studies have shown that antigenic variation may play a significant role in the development of prolonged parasitemia, that complement-induced changes to erythrocytes are pivotal in facilitating protozoan entry into host RBCs, and that autoimmunity contributes to disease. Severe infections may require lifesaving exchange transfusions and even plasmapheresis. Controlled studies to clearly define specific indications, benefits, and objectives of this therapy are still needed. Despite the development of novel and improved diagnostic tests, these tests are not readily available for the mass screening of blood donors. Improved strategies to assess and prevent transfusion-associated babesiosis are required. Current measures cannot be relied on to identify infected donors with a high degree of sensitivity or to protect susceptible recipients from this parasite. Copyright 2002, Elsevier Science (USA). All rights reserved.