Transfusion Babesiosis Involving WA1-Type Parasite
Abstract & Commentary
Synopsis: A case of well documented babesiosis transmitted by red blood cell transfusion is described; it is the first infection transmitted in this way caused by a recently (1993) described babesia-like organism, WA1.
Source: Herwaldt BL, et al. Transfusion-transmitted babesiosis in Washington state: First reported case caused by a WA1-type parasite. J Infect Dis 1997;175:1259-1262.
Herwaldt and colleagues report the case of a 76-year-old man with babesiosis, not caused by Babesia microti, which was acquired by transfusion of packed red blood cells. The patient, who had been multiply transfused over a number of years for various reasons, presented with fever, fatigue, anorexia, weakness, and weight loss in the autumn of 1994. His hematocrit was 28 vol %; ring forms, originally thought to represent plasmodia, were observed in less than 1% of his erythrocytes. Treatment with chloroquine and primaquine failed to clear the parasitemia.
Further review of his peripheral blood smear identified a single intra-erythrocytic tetrad consistent with the presence of a babesia-like organism. Babesiosis was confirmed by isolation of the organism by hamster inoculation. Serological studies found that the patient had very high antibody titers to antigen prepared from his parasite and to WA1-type parasite, but no antibody to B. microti. He was then treated with clindamycin and quinine with resultant negative hamster inoculation results, decrease in his antibody titers, but with persistent fatigue and intermittent chills.
Evaluation of relevant blood donors identified one, from whom the patient had received packed red blood cells three days after donation and approximately one month before presentation, with a very high serum titer to the patient's isolate. The donor, who lived in a rural area frequented by deer, was generally healthy, but inoculation of his blood into hamsters seven months after the implicated donation yielded a babesia-like organism. Sequencing of a region of nuclear small subunit rRNA of the isolates from both the recipient and the donor found them to be identical to that of WA1, which had been isolated from a patient with tick borne disease in 1991.
COMMENT BY STAN DERESINSKI, MD, FACP
Babesiosis, long known as a disease of cattle (believed by some to be the cause of the plague that killed the cattle of Ramses II, as described in Exodus), was first described in humans in 1957. Reported cases in the United States were initially all acquired in the northeastern coastal region. Subsequent cases have, however, been reported from a variety of geographic areas throughout the country. More recently, infection with WA1, a babesia-like organism that was thought to represent a new species, was found in the blood of patients from Washington state and California, while another isolate, called MO1, was found in Missouri.1-3
Studies indicate that WA1 and, by implication, the strains identified in this report, are genetically distinct from B. microti. These parasites reside in the host erythrocyte in which they, as in this case, are often mistaken for plasmodia, particularly P. falciparum. Babesia sp., however, lack the hemozoin (brown pigment), as well as the synchronous developmental stages seen with that organism. The finding of tetrads of merozoites ("Maltese Cross") is uncommon, but diagnostic of babesiosis, and was the clue to diagnosis in the case reviewed here. Serological tests for infection with B. microti are available but may not detect infection with other babesia-like organisms. Since Lyme disease is transmitted by the same ticks as babesiosis, evidence of this infection should also be sought in patients with babesiosis.
Babesiosis is a zoonosis whose transmission to humans is predominantly via the bite of ticks. In Europe, the infection is transmitted from bovine species by Ixodes ricinus, while in the United States, the reservoir is in rodents with transmission by Ixodes scapularis. Babesiosis in Taiwan, only recently described for the first time, may have its reservoir in rodents as well.4
Transmission of babesiosis by blood transfusion was first reported in 1991.5,6 Transmission of B. microti in blood is facilitated by an incubation period that may be as long as a month, by its ability to cause prolonged asymptomatic infection of red blood cells, and its capability of survival under typical blood bank conditions.
References
1. Quick RE, et al. Ann Intern Med 1993;119:284-290.
2. Persing DH, et al. N Engl J Med 1995;332:298-303.
3. Herwaldt BL, et al. Ann Intern Med 1996;124:643-650.
4. Shih CM, et al. J Clin Microbiol 1997;35:450-454.
5. Popovsky MA. Trasnfusion 1991;31:296-298.
6. Mintz ED, et al. Transfusion 1991;31:296-298.
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