Case #290 – December, 2010

A 31-year-old man was admitted to a local hospital with fever, chills, myalgia, and fatigue. His travel history included a two week work-related trip to Cambodia and a one week vacation in Connecticut immediately after that trip. His symptoms began about 3 days after returning from Connecticut. He indicated that he did take anti-malarial prophylaxis while in Cambodia but failed to take the remainder of his medication before going to Connecticut. Blood smears were ordered, stained with Giemsa, and examined. Figures A–D show what was observed at 1000x oil magnification. What is your diagnosis? Based on what criteria?

Figure A

Figure B

Figure C

Figure D

This was a case of babesiosis caused by Babesia sp. Morphologic features included:

pleomorphic and vacuolated intraerythrocytic ring-like parasites in normal-sized red blood cells.
an absence of malarial pigment found in Plasmodium species.

In general, identification of Babesia to the species or strain level is not possible by morphology, and requires molecular analysis of a blood specimen. Regrettably, no pretreatment blood was available in this case for subsequent testing so the final diagnosis remains Babesia sp.