to the editor: The article by Dr. Mylonakis provides an excellent overview of the management of babesiosis.¹ I would like to point out, however, that the degree of parasitemia need not always parallel the severity of clinical symptoms.² This disparity may be attributed to some of the indirect, harmful effects related to parasitemia within the host. Usually, this is evident when anemia is disproportionate to the degree of parasitemia.³ The reason for such incongruity is related to the fact that both parasitized and healthy erythrocytes get destroyed, as a result of an infection-mediated, autoimmune, hemolytic process.The production of anti-erythrocytic autoantibodies, possibly aimed at Rh antigens on the red cell,⁴ explains why some persons may have a positive Coombs test during infection.

Dr. Mylonakis recommends exchange transfusion, together with antibabesial chemotherapy, for critically ill patients with a blood parasitemia of more than 10 percent, massive hemolysis and asplenia.¹ Indeed, prompt institution of exchange transfusion, in combination with appropriate drug therapy, can be life-saving; however, reliance solely on the level of parasitemia or the degree of hemolysis alone to advocate this form of therapy may be misleading, for the reasons alluded to above. Cases that are refractory to appropriate antibiotic therapy may also respond to exchange transfusion. Moreover, exchange transfusion may be of value to persons who cannot tolerate drugs because of toxicities or adverse effects. Transfusions are not to be recommended for routine management because of the hazards posed by multiple blood exposures. The benefits of this treatment, however, clearly outweigh the risks when it is clinically indicated. Until controlled trials are available to clarify the specific indications, merit and goals of exchange transfusion in the management of babesiosis, clinical judgment is probably still the best guide.

in reply: I would like to thank Dr. Pantanowitz for his interest in my article. In his letter, Dr. Pantanowitz suggests that "clinical judgment" is the best guide for the use of exchange transfusion in the management of babesiosis. I wholeheartedly agree, and this is stated clearly and unequivocally in my paper.¹

Dr. Pantanowitz also writes that "exchange transfusion may be of value to persons who cannot tolerate drugs because of toxicities or adverse effects."I would like to caution care providers that the use of exchange transfusion without antimicrobial chemotherapy is untested. The appropriate management of patients who are ill enough to require exchange transfusion and cannot tolerate an antimicrobial regimen is to try another regimen, not to use exchange transfusion alone. In a large study among patients with babesiosis, 97.5 percent of patients were able to complete a course of azithromycin with atovaquone with excellent results,² and a number of other treatment options are available.