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TABLE 8

 

Malaria characteristics with fresh blood or blood collected using EDTA with no extended lag time (preparation of thick and thin blood films within < 60 min of collection)

 

Plasmodium vivax (benign tertian malaria)

1.      48-hour cycle

2.      Tends to infect young cells

3.      Enlarged RBCs

4.      Schüffner's dots (true stippling) after 8-10 hours

5.      Delicate ring

6.      Very ameboid trophozoite

7.      Mature schizont contains 12-24 merozoites

 

Plasmodium malariae (quartan malaria)

1.      72-hour cycle (long incubation period)

2.      Tends to infect old cells

3.      Normal size RBCs

4.      No stippling

5.      Thick ring, large nucleus

6.      Trophozoite tends to form "bands" across the cell

7.      Mature schizont contains 6-12 merozoites

 

Plasmodium ovale

1.      48-hour cycle

2.      Tends to infect young cells

3.      Enlarged RBCs with fimbriated edges (oval)

4.      Schüffner's dots appear in the beginning (in RBCs with very young ring forms in contrast to P. vivax)

5.      Smaller ring than P. vivax

6.      Trophozoite less ameboid than that of P. vivax

7.      Mature schizont contains average 8 merozoites

 

Plasmodium falciparum (malignant tertian malaria)

1.      36-48-hour cycle

2.      Tends to infect any cell regardless of age, thus very heavy infection may result

3.      All sizes of RBCs

4.      No Schüffner's dots (Maurer's dots: may be larger, single dots, bluish)

5.      Multiple rings/cell (only young rings, gametocytes, and occasional mature schizonts are seen in peripheral blood)

6.      Delicate rings, may have two dots of chromatin/ring, appliqué or accolé forms

7.      Crescent-shaped gametocytes

 

Plasmodium knowlesi (simian malaria)*

1.         24-hour cycle

2.         Tends to infect any cell regardless of age, thus very heavy infection may result

3.         All sizes of RBCs, but most tend to be normal size        

4.         No Schüffner’s dots (faint, clumpy dots later in cycle)

5.         Multiple rings/cell (may have 2-3)

6.         Delicate rings, may have two or three dots of chromatin/ring, appliqué forms

7.         Band form trophozoites commonly seen

8.         Mature schizont contains 16 merozoites, no rosettes

9.         Gametocytes round, tend to fill the cell

 

*Early stages mimic P. falciparum; later stages mimic P. malariae