Case #515 - May, 2020
A group of college students traveled to Brazil on a rafting and camping trip for two weeks. Malaria prophylaxis was highly recommended however one student declined. The one student who declined prophylaxis developed headache, fever, and chills two days after returning from the trip. He sought medical attention at the university travel clinic and a blood smear was prepared, stained with Wrights stain and examined for parasites. Figures A–G show what was detected. What is your diagnosis? Based on what criteria?
This was a case of malaria caused by Plasmodium vivax. Diagnostic morphologic features shown in the images included:
- enlarged infected red blood cells up to 1.5 x normal size
- amoeboid trophozoite with tenuous pseudopodial processes (Figure C)
- schizont with 16 merozoites (P. ovale has 8-10 on average)
- travel history of the patient
The infected rbcs of this case did not present stippling and demonstrates why we recommend using a Giemsa stain at the proper pH. Doing so can allow one to observe Schüffner’s dots (stippling), a morphologic feature which is only associated with P. vivax and P. ovale. The travel history of this case was Brazil and P. ovale is not recorded in the New World.
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Images presented in the monthly case studies are from specimens submitted for diagnosis or archiving. On rare occasions, clinical histories given may be partly fictitious.
DPDx is an educational resource designed for health professionals and laboratory scientists. For an overview including prevention, control, and treatment visit www.cdc.gov/parasites/.