Plasmodium falciparum
It is the causative agent of malignant tertian fever (term no longer in use):
fever on the first day, remission of fever on the second, return of fever
on the third (synchronous malaria). In order for this to occur, different
asexual erythrocytic cycles must take place, i.e. trophozoite transformation
into schizont, division and maturation, rupture of the schizont, merozoite
invasion of new red blood cells, all parasitized in a synchronous way. Actually
this hardly ever occurs, so that the patient almost always experiences fever
on a daily basis. This species is responsible for highly severe and often fatal
pernicious attacks, especially in non-immune individuals; a diagnosis must
be made with extreme urgency, since immediate pharmacological treatment
is called for. It produces a higher level of parasitemia than other species
(Plate 7).
Parasitized red blood cells
Red blood cells of all ages are parasitized [46].
Size and shape: normal, round.
Granulations: characteristic (Maurer’s clefts) and of great diagnostic value
provided that the film is stained with an aqueous solution at pH 7.2.
Polyparasitism: very frequent in this species, from 2 to 7 trophozoites may
occupy the same red blood cell, which nonetheless retains the same size and
shape.
Young trophozoite
It consists of a regular ring of blue-pale blue cytoplasm surrounding
a clearly visible vacuole, generally paler in color compared to the rest of
the red blood cell, and a ruby red or purple-red eccentric nucleus. The
appearance is like that of a signet ring. It should be pointed out that the
other three species display a similar appearance at this stage and species
identification is thus impossible. The nucleus may appear in the form of
two (or exceptionally three) masses joined by a chromatin bridge, or else it
may be positioned in the middle of the ring, appearing like a “bird’s eye”
or “cockade”. The trophozoite may assume different positions within the
parasitized erythrocyte: marginal form, flattened form “accolè”or “appliquè”,
“extra-terrestrial” form [64]. The cytoplasm may likewise assume different
forms. Neither Maurer’s clefts nor malaria pigment are present at this
stage.