PERSISTENT PARASITEMIA AFTER ACUTE BABESIOSIS

Background Babesiosis, a zoonosis caused by the protozoan Babesia micr oti, is usually nor treated when the symptoms are mild, because the pa rasitemia appears to be transient. However, the microscopical methods used to diagnose this infection are insensitive, and few infected peop le have been followed longitudinally. We compared the duration of para sitemia in people who had received specific antibabesial therapy with that in silently infected people who had not received specific therapy . Methods Forty-six babesia-infected subjects were identified from 199 1 through 1996 in a prospective, community-based study designed to det ect episodes of illness and of seroconversion among the residents of s outheastern Connecticut and Block Island, Rhode island. Subjects with acute babesial illness were monitored every 3 months for up to 27 mont hs by means of thin blood smears, Bab. microti polymerase-chain-reacti on assays, serologic tests, and questionnaires. Results Babesial DNA p ersisted in the blood for a mean of 82 days in 24 infected subjects wi thout specific symptoms who received no specific therapy. Babesial DNA persisted for 16 days in 22 acutely ill subjects who received clindam ycin and quinine therapy (P = 0.03), of whom 9 had side effects from t he treatment. Among the subjects who did not receive specific therapy, symptoms of babesiosis persisted for a mean of 114 days in five subje cts with babesial DNA present for 3 or more months and for only 15 day s in seven others in whom the DNA was detectable for less than 3 month s (P<0.05); one subject had recrudescent disease after two years. Conc lusions When left untreated, silent babesial infection may persist For months or even years. Although treatment with clindamycin and quinine reduces the duration of parasitemia, infection may still persist and recrudesce and side effects are common. Improved treatments are needed . (N Engl J Med 1998;339:160-5.) (C)1998, Massachusetts Medical Societ y.