Which malaria parasite typically shows ameboid trophozoites and produces small reddish dots in the red blood cell cytoplasm?

• A. Plasmodium knowlesi
• B. Plasmodium falciparum
• C. Plasmodium malariae
• D. Plasmodium vivax

Answer: (D)

Focus on how malaria parasites look in stained blood smears. Plasmodium vivax is characterized by amoeboid trophozoites and the presence of Schuffner’s stippling—small reddish dots—in the red blood cell cytoplasm. The amoeboid shape reflects a more irregular, expansive trophozoite form, and the stippling results from cytoplasmic changes in the infected RBCs, giving pinkish granules that are visible under light microscopy. Vivax also tends to enlarge the infected red cells because it preferentially invades reticulocytes, which helps distinguish it from other species.

In contrast, falciparum typically shows tiny ring forms and may have multiple parasites in one RBC, without the characteristic RBC enlargement or Schuffner’s dots. Malariae features band-shaped trophozoites and normally-sized RBCs, and knowlesi can resemble falciparum or malariae at different stages but does not present this amoeboid trophozoite with Schuffner’s dots pattern.