[Last Modified: ]

April 2006
Answer to Case 177
This is a case of babesiosis caused by Babesia sp.  Diagnostic features are:

• many ring-form organisms with red chromatin dots surrounded by blue cytoplasm.  There is no yellow and/or brown pigment visible, which may be present in Plasmodium spp.  Although the thick smear is useful in determining the presence of parasites, an examination of thin smears is necessary in order to make an accurate laboratory diagnosis.
• the presence of pleomorphic intra-erythrocytic parasites (Figure B), a feature consistent with Babesia spp.
• vacuolated ring-forms (Figure B below, black arrow).

B

Additional testing methods, such as serology and/or molecular techniques, are always recommended to make a species identification of Babesia.

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