Medical Microbiology

&Afteroneormoreschizogonicgenerations,someoftheplasmodiaineach

generationdevelopintosexualforms,themalemicrogamonts(microgame-

tocytes),andfemalemacrogamonts(macrogametocytes).Thesesexualforms

(gametocytes)persistforacertainperiodintheblood(P.vivaxoneday,P.

falciparumupto 22 days),afterwhichthosenottakenupbybloodsucking

Anophelesfemalesdie.

Plasmodium 525

MalarialPlasmodia:DifferentialDiagnosisinBloodSmears

Plasmodium ovale

Infected erythrocyte beginning at stage A: somewhat enlarged, often oval with ragged

edges, Schüffner's dots more pronounced than in Plasmodium vivax

Rings similar

to Plasmodium

vivax

Rounded or cleft,

pigment not very

prominent

8 merozoites,

pigment central

Similar to

Plasmodium vivax,

rare in oval

erythrocytes

Plasmodium malariae

Infected erythrocyte: size normal or somewhat smaller than usual, multiple infection rare

Plasma ring

wide,vacuole

midsized

Band or rounded

form, vacuoles

lacking or small,

pigment dark brown

6–12 merozoites,

often in rosette

form, pigment

usually central

Similar to P. vivax,

but smaller

Similar to

Plasmodium vivax,

rare in oval

erythrocytes

Similar to P. vivax,

but smaller

A: Young

trophozoite

B: Older

trophozoite

C: Schizont D: Macro-

gametocyte

E: Micro-

gametocyte

Fig.9. 18 Continued

9

Kayser, Medical Microbiology © 2005 Thieme