Case #507 – January, 2020

A 63-year-old man returned from visiting with family in Nigeria. He developed fever, chills and a mild headache three days before presenting to the clinic. A medical evaluation revealed that he also had not taken any drug prophylaxis prior to or during his visit. A blood smear was ordered and stained with Giemsa. Figures A and B (thick smears) and C and D (thin smears) show what was observed. What is your diagnosis? Based on what criteria?

(This case and images were kindly provided by the NV-Southern Nevada Health District Office of Epidemiology.)

Figure A

Figure B

Figure C

Figure D

This was a case of malaria caused by Plasmodium falciparum. Morphologic features shown included:

Numerous ring stage parasites in the thick smears (Figures A and B).
Schizont (rarely seen in peripheral blood) with 9-10 merozoites and compact pigment in one thick smear (Figure B).
Infected red blood cells (RBCs) normal size in the thin smears (Figures C and D).
Applique forms and ring stage parasites with delicate cytoplasm in the thin smears.

In addition to the morphologic features, PCR testing results also revealed that only Plasmodium falciparum was present.