Microscopy

A

A: Babesia microti infection, Giemsa stained thin smear.  The organisms resemble Plasmodium falciparum; however Babesia parasites present several distinguishing features: they vary more in shape and in size, and they do not produce pigment.  A 67-year-old woman, status postsplenectomy, infection probably acquired in Long Island (New York).

B	C

B, C: Infection with Babesia.  Giemsa stained thin smears.  Note in B the tetrad (left side of the image), a dividing form pathognomonic for Babesia.  Note also the variation in size and shape of the ring stage parasites (compare B and C), and the absence of pigment.  A 6-year-old girl, status postsplenectomy for hereditary spherocytosis, infection acquired in the United States.