Transmission of toxoplasmosis by leukocyte transfusion.

S TUDIES IN RABBITS HAVE SHOWN that the protozoan Toxoplasma gondii is able to parasitize peripheral blood leukocytes.’ In humans, parasitemia caused by this organism has been demonstrated in an asymptomatic blood donor,2 and in a woman who delivered a congenitally infected infant.3 Despite these observations, no cases of acute toxoplasmosis acquired via transfusion of blood products have been reported previously. We have recently observed four patients with acute leukemia who developed toxoplasmosis following transfusion of leukocytes (WBC) from donors with chronic myelogenous leukemia (CML). These transfusions had been given in an attempt to treat granulocytopenia complicated by bacterial infection.4 Serologic data, obtained retrospectively, suggest that the transfused leukocytes were the source of the parasite in the recipients.