Identification is based on observation of the parasite on Giemsa or Wright-stained blood smears. Multiple smears may be needed for diagnosis. Typical multiple-ring forms are seen in the RBCs. The Maltese cross formation, shown in the lower image, is helpful but not common in most smears. Thick blood smears are not very useful because the rings are polymorphic and can be confused with stain precipitate. Indirect immunofluorescence titer can be performed, and PCR may be valuable.
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