No abstract

Babesiosis is a parasite infection that causes wide spectrum of clinical manifestations. To examine the peripheral blood for Babesia, most laboratories prepare thick and thin peripheral blood (PB) smears from a patient and stain them with Giemsa, essentially employing the routine technique used for detecting malaria parasites. This method is labor intensive and time consuming. Also, patients with low levels of parasitemia are sometimes missed. We studied the use of acridine orange to see if this stain could be helpful in diagnosis of Babesia. 36 blood samples were collected from the patients with suspected infection between June and August. Two identical thin peripheral blood smear slides were prepared and a small aliquot was submitted for PCR testing. PCR test was considered confirmatory test. The slides were stained with either standard Giemsa or AO stain. The paired slides were examined under either light or fluorescent microscope (FITC filter) by two pathology residents. Using increasing magnification power, the slides were examined for the presence of Babesia and its morphology. The concordance of the two methods was analyzed and all the results were compared to PCR. Out of 36 patients who were tested for babesiosis, four patients had Babesia species identified in both Giemsa and AO stained slides. The four patients' blood sample PCR tests were also positive. Three of four patients had initial parasitemia of approximately 10%. The positive patients were followed with daily PB smears and PCR tests (average days followed = 6 days), which was stopped when there was no detectable Babesia species on Giemsa-stained smears. Comparing the two staining methods, AO stain was more sensitive in detecting Babesia than standard Giemsa stain at low power (10×). Parasites stained with AO fluoresced brightly against the dark background, and this greatly improved visibility, therefore increasing sensitivity even in low levels of parasitemia.