HUMAN BABESIOSIS IN TAIWAN - ASYMPTOMATIC INFECTION WITH A BABESIA MICROTI-LIKE ORGANISM IN A TAIWANESE WOMAN

An asymptomatic Babesia infection was confirmed by laboratory diagnose s. The intraerythrocytic protozoan (designed TW1) isolated from a 51-y ear-old Taiwanese woman appeared to be morphologically consistent with small-form piroplasm, and measurements indicated that it had a body s ize of 1.5 to 2.5 mu m in diameter, The typical features of ring, bina ry, and tetrad forms were observed in Giemsa-stained thin blood smears , A persistent and low grade parasitemia was established after hamster inoculation, Indirect immunofluorescent-antibody reactivities indicat e that this strain (TW1) of Babesia was serologically related to, but not identical to, the Babesia species (B. microti) that infects rodent s, Antibody titers in the patient's sera combined with the clinical sy mptoms suggested that the present case was a chronic and subclinical b abesial infection. A neighborhood human serologic survey indicated tha t the infection may have been acquired accidentally from an infected r odent and localized within the same family. Indeed, rodents from areas around the neighborhood were trapped, and a high prevalence (83%) of babesial infection was observed. The possible vector responsible for t he transmission remains to be identified.