Diagnostic Findings [Last Modified: ]
Malaria
[Plasmodium falciparum] [Plasmodium knowlesi] [Plasmodium malariae] [Plasmodium ovale] [Plasmodium vivax]
Causal Agent Life Cycle Geographic Distribution Clinical Features Laboratory Diagnosis Treatment

Early ring-form trophozoites (rings) of P. knowlesi are similar to P. falciparum, as rings may show double chromatin dots.  Appliqué forms may appear, as well as rectangular rings harboring one or more accessory chromatin dots.  Red blood cells may also be multiply-infected.  When full-grown, non-amoeboid rings may occupy half or more of the host RBC.

Plasmodium knowlesi ring-form trophozoites
A

A: Ring-form trophozoites of P. knowlesi.  Fig. 1: Normal red cell; Figs. 2-6: Increasingly mature ring-form parasites.
Illustrations from: Coatney GR, Collins WE, Warren M, Contacos PG. The Primate Malarias. Bethesda: U.S. Department of Health, Education and Welfare; 1971.

Plasmodium knowlesi ring-form trophozoites in thin blood smear Plasmodium knowlesi ring-form trophozoites in thin blood smear
B C

B, C: Ring-form trophozoites of P. knowlesi in a thin blood smear from a human patient that traveled to the Philippines.  Images courtesy of the Wadsworth Center, New York State Department of Health.

Plasmodium knowlesi ring-form trophozoites in thin blood smear Plasmodium knowlesi ring-form trophozoites in thin blood smear
D E

D, E: Ring-form trophozoites of P. knowlesi in a thin blood smear from a human patient that traveled to the Philippines.  Images courtesy of the Wadsworth Center, New York State Department of Health.

 
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