Detection of extracellular forms of babesia in the blood by electron microscopy: a diagnostic method for differentiation from Plasmodium falciparum.

Light microscopic examination of blood smears is the traditional approach for the diagnosis of babesiosis, but there is morphological overlap with Plasmodium falciparum. The authors describe 3 patients with babesial infection in whom the diagnosis was made by identifying extracellular merozoites in a buffy coat preparation using electron microscopy. This method resulted in a high yield of extracellular babesia, even in a case where virtually no extracellular babesia were detectable in the blood smear. The test had a reasonably fast turnaround time and allowed detailed visualization of the organisms and reliable distinction from Plasmodium falciparum.